US20040178944A1 - Radio tag for lfm radar - Google Patents
Radio tag for lfm radar Download PDFInfo
- Publication number
- US20040178944A1 US20040178944A1 US09/804,355 US80435501A US2004178944A1 US 20040178944 A1 US20040178944 A1 US 20040178944A1 US 80435501 A US80435501 A US 80435501A US 2004178944 A1 US2004178944 A1 US 2004178944A1
- Authority
- US
- United States
- Prior art keywords
- lfm
- signal
- pulse waveform
- circuit
- waveform
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Granted
Links
- 230000005540 biological transmission Effects 0.000 claims abstract description 16
- 238000010200 validation analysis Methods 0.000 claims abstract 11
- 238000000034 method Methods 0.000 claims description 12
- 238000004891 communication Methods 0.000 claims description 10
- 239000013307 optical fiber Substances 0.000 claims description 2
- 230000004044 response Effects 0.000 claims description 2
- 230000001360 synchronised effect Effects 0.000 abstract description 5
- 230000010355 oscillation Effects 0.000 abstract description 3
- SDJLVPMBBFRBLL-UHFFFAOYSA-N dsp-4 Chemical compound ClCCN(CC)CC1=CC=CC=C1Br SDJLVPMBBFRBLL-UHFFFAOYSA-N 0.000 description 14
- 238000010586 diagram Methods 0.000 description 11
- 238000012545 processing Methods 0.000 description 7
- 238000013461 design Methods 0.000 description 6
- 230000003111 delayed effect Effects 0.000 description 4
- 238000001514 detection method Methods 0.000 description 4
- 238000005070 sampling Methods 0.000 description 4
- 230000003321 amplification Effects 0.000 description 3
- 238000003199 nucleic acid amplification method Methods 0.000 description 3
- 230000008569 process Effects 0.000 description 3
- 238000002592 echocardiography Methods 0.000 description 2
- 230000000737 periodic effect Effects 0.000 description 2
- 238000012216 screening Methods 0.000 description 2
- 230000003595 spectral effect Effects 0.000 description 2
- 101150062184 DSP4 gene Proteins 0.000 description 1
- 230000009471 action Effects 0.000 description 1
- 230000008901 benefit Effects 0.000 description 1
- 238000004364 calculation method Methods 0.000 description 1
- 230000015556 catabolic process Effects 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 125000004122 cyclic group Chemical group 0.000 description 1
- 230000003247 decreasing effect Effects 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 230000006870 function Effects 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- 238000001228 spectrum Methods 0.000 description 1
- 230000007704 transition Effects 0.000 description 1
Images
Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S13/00—Systems using the reflection or reradiation of radio waves, e.g. radar systems; Analogous systems using reflection or reradiation of waves whose nature or wavelength is irrelevant or unspecified
- G01S13/74—Systems using reradiation of radio waves, e.g. secondary radar systems; Analogous systems
- G01S13/82—Systems using reradiation of radio waves, e.g. secondary radar systems; Analogous systems wherein continuous-type signals are transmitted
- G01S13/825—Systems using reradiation of radio waves, e.g. secondary radar systems; Analogous systems wherein continuous-type signals are transmitted with exchange of information between interrogator and responder
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S13/00—Systems using the reflection or reradiation of radio waves, e.g. radar systems; Analogous systems using reflection or reradiation of waves whose nature or wavelength is irrelevant or unspecified
- G01S13/74—Systems using reradiation of radio waves, e.g. secondary radar systems; Analogous systems
- G01S13/76—Systems using reradiation of radio waves, e.g. secondary radar systems; Analogous systems wherein pulse-type signals are transmitted
- G01S13/765—Systems using reradiation of radio waves, e.g. secondary radar systems; Analogous systems wherein pulse-type signals are transmitted with exchange of information between interrogator and responder
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S13/00—Systems using the reflection or reradiation of radio waves, e.g. radar systems; Analogous systems using reflection or reradiation of waves whose nature or wavelength is irrelevant or unspecified
- G01S13/88—Radar or analogous systems specially adapted for specific applications
- G01S13/89—Radar or analogous systems specially adapted for specific applications for mapping or imaging
- G01S13/90—Radar or analogous systems specially adapted for specific applications for mapping or imaging using synthetic aperture techniques, e.g. synthetic aperture radar [SAR] techniques
- G01S13/904—SAR modes
Abstract
Description
- (Not Applicable)
- (Not Applicable)
- A basic transponder receives a signal from a SAR (synthetic-aperture radar), and then retransmits the signal back to the SAR. The problem with retransmitting the signal back to the SAR without any changes is that the signal must compete with ground reflection noise from natural and cultural ground clutter. If no type of modulation is used, then to stand out above the background noise, extra power and electronics are often needed to increase the gain in the return signal, often requiring two antennas, one for receiving and one for transmitting. Most transponders do not provide any added information in the retransmitted signal. In most cases the interrogator is a SAR located in an aircraft or satellite, and a transponder is located some distance away from the radar, normally on the ground.
- The ability to provide command control and communications to and from a transponder has many potential applications. Besides the military applications for battlefield management, intelligence gathering and the like, there are commercial applications which include transponder status, other environmental status and emergency response. A RFID (radio frequency identification) system contains two main elements, an interrogator and one or more transponders. In the radar transmission between the interrogator and transponder, a RF signal is encoded within the SAR pulse to provide information between the interrogator and transponder, that is normally unknown to the other element.
- U.S. Pat. No. 5,486,830 discloses a RFID system wherein digital codes are encoded in the SAR signal that is received by a transponder, also called a RF tag or simply tag. A single antenna can be utilized by this transponder to transmit and receive signals. This is accomplished by a time-gating method using a 50% duty cycle factor for setting the tag's transmitting and receiving intervals, which are mutually exclusive. The received SAR signal is mixed with a reference oscillator to provide a detected signal that can be decoded. Tag logic and timing circuits measure the time between detected pulses and decode these pulses into downlink commands from the SAR, symbols of the downlink commands are encoded in the spacing between the SAR pulses. Downlink commands contain mode information that allows the SAR and tag to obtain a common pulse index (coarse synchronization) . However, in order to achieve fine synchronization the tag must average the measured time-of-arrival of a number of pulses. After fine synchronization is achieved, and if so commanded, the tag will go into the uplink mode. The tag device phase encodes its echo with a sequence containing both prescribed and periodic or pseudo-random patterns, containing status or information unknown to the radar source's signal processor. A bi-phase (0/pi) modulator is utilized to allow selective amplification of +1 or −1 of the signal before retransmitting the signal back to the SAR. The signal processing at the SAR mixes a sequence identical to the prescribed periodic or pseudo-random selective amplification against the received echoes. This selective amplification spreads the spectrum of the natural or cultural echoes and de-spreads the tag's echo, making the retransmitted signal stand out above the natural or cultural noise.
- The present invention is an improvement over the other REFID systems. Prior art used simple pulses defined by their spacings in the SAR pulses. The pulses represent symbols that encode the digital information contained in the SAR pulses.
- The present invention uses SAR LFM (linear frequency modulation) pulse waveforms. One advantage of using LFM pulse waveforms is that these waveforms are not noise sensitive. While the symbols of the encoded digital code are determined by the time internal between the pulses as in U.S. Pat. No. 5,486,830, noise can cause an incorrect interval to be detected and thereby generate an invalid message.
- Two receivers, an AM and a FM receiver, are connected to an antenna and are used to demodulate their respective components of the LFM pulse waveform. The output of the AM receiver is the demodulated envelope that is proportional to the amplitude of the AM component of the LFM pulse waveform. The amplitude and time duration are compared to a preprogrammed threshold and time duration criteria. The preprogrammed criteria are stored in the tag DSP (Digital Signal Processor. If both the threshold value and time duration are determined to be valid, then the demodulated FM portion of the LFM pulse waveform is checked for validity.
- A reference local oscillator is needed to demodulate FM signal component of a LFM pulse waveform. This is generated by delaying LFM pulse waveform and mixing it with the non-delayed LFM pulse waveform. A separate reference oscillator is, therefore, not required. The demodulated waveform is then passed through a zero-crossing detector. The output of the zero-crossing detector is sampled and the samples are counted by the DSP to estimate the average frequency over the pulse duration.
- In order to determine the slope of the frequency deviation, a 90° power splitter is added to the local oscillator, before the mixer. The power splitter has two outputs, one in-phase and one in quadrature-phase with the LFM pulse waveform. The signal component set of mixer, lowpass filter, zero-crossing detector and sampler is replaced with two identical sets of components. The output of the set with the in-phase signal is labeled “FM In-Phase”, and the output of the set with the quadrature-phase signal is labeled “FM quadrature-phase”. These two outputs are then used by the DSP to determine the slope of the frequency deviation.
- The DSP utilizes the slope information and frequency deviation to determine the message sent by the SAR. Though the use of Phase Modulation (PM), the tag can encode data to send back to the SAR.
- By using RF switches, the signals can be directed so that the same antenna can be used for receiving and transmitting. Since the same antenna is used, a chop timing of the RF switches in required. There are 3 stages in the chop signal: receive, transmit and blanking. The blanking stage is required to prevent oscillations in the tag due to reflections from nearby objects. Some systems require randomizing the blanking time to prevent the radar from accidentally locking onto the spectral lines that are generated during the chopping of the RF signal. The blanking times can change pseudo-randomly each cycle.
- Illustrative and presently preferred embodiments of the present invention are shown in the accompanying drawings in which:
- FIG. 1 is simplified block diagram of the tag;
- FIG. 2 is the detailed block diagram of the tag;
- FIG. 3 is the detailed block diagram of the digital signal processor;
- FIG. 4 is the software flow diagram during message reception;
- FIG. 5 is the signal flow through the AM receiver;
- FIG. 6 is the signal flow through the FM receiver;
- FIG. 7a is a graph of the low pass filter output of the FM receiver;
- FIG. 7b is a table showing the frequency estimator code;
- FIG. 8 is a timing diagram for synchronizing the tag and radar;
- FIG. 9 is the signal flow during transmit;
- FIG. 10 shows the chop timing of S1 and S2;
- FIG. 11a is a diagram of the random chop generator;
- FIG. 11b is a table showing the tag modulation states per pulse;
- FIG. 12 shows the tag modulation.
- FIG. 13a shows the FM receiver without slope direction;
- FIG. 13b shows the FM receiver with slope direction capability;
- FIG. 14a shows a graph of the I and Q outputs of the FM Receiver;
- FIG. 14b is a table showing the slope measurement code;
- FIG. 15 shows the slope polarity of a positive-going LFM; and
- FIG. 16 shows the slope polarity of a negative-going LFM.
- FIG. 1 shows the transponder device or tag10 simplified block diagram. An
antenna 1 receives the LFM (linear frequency modulation) input waveform from SAR. The received waveform is then fed into theAM receiver 2, theFM receiver 3, and astorage element 6. TheAM receiver 2 demodulated output signal is then fed into the digital signal processor (DSP) 4. If theDSP 4 determines that the AM demodulated output signal is valid, then theDSP 4 determines if the demodulated output of theFM receiver 3 is valid. If both demodulated outputs are valid, then theDSP 4 checks the validity of the received LFM input waveform against stored data. After theDSP 4 has determined that the data encoded in the LFM input waveform is valid, and decoded the message; the RF signal stored in thestorage element 6 is modulated in themodulator 5. The output of themodulator 5 is then fed back into theantenna 1 to be transmitted back to the originating source. - FIG. 2 shows a further breakdown of the components of the
tag 10. The typical operating frequency is 8 to 12 GHz. The LFM input waveform is sensed inantenna 1. Abandpass filter 11 is utilized to remove any undesirable out of band signals out of the LFM input waveform. A firstdirectional coupler 12 passes the filtered LFM input waveform to aRF switch 13 through the coupled side of thedirectional coupler 12. Ifswitch 13 is closed, then the received filtered RF signal will be fed into alow noise amplifier 14. TheRF switch 13 is only closed during the receive cycle.Switch 20 is open during the receive cycle. The RF filtered LEFM input waveform is then routed through the coupled side of thesecond coupler 15. A secondlow noise amplifier 22 amplifies the signal, which is then fed into apower splitter 23. Up to the input of thepower splitter 23, the LFM input waveform signal has been identically processed for both theAM receiver 2 andFM receiver 3. - The signal flow in the
AM receiver 2 continues from the output of thepower splitter 23 though thebandpass filter 24.Bandpass filter 24 removes unwanted out of band noise generated by the two previous amplifier stages 14 and 22. The output offilter 24 is applied to adiode detector 25. Thedetector 25 demodulates the envelope of the LFM input waveform; the output ofdetector 25 is proportional to the amplitude of the LFM input waveform. A square law device is used in the detector although other types of detector devices are possible, such as envelope, synchronous, and log-video; however the square law detector is one of the most common forms. In the preferred embodiment, thedetector 25 consists of a tunnel diode and passive bias components and the design is not shown but is well known to practitioners of the art. The detected output of thedetector 25 is filtered by alow pass filter 26, which removes the higher order frequency terms which were generated during the non-linear process of detection. Avideo amplifier 27 amplifies the filtered output offilter 26. The output of thevideo amplifier 27 is applied to the positive input terminal of athreshold comparator 28. The voltage at the negative input terminal of thecomparator 28 is set by a digital to analog converter (DAC) 35. The output of theDAC 35 is determined by the digital word from theDSP 4. The output of thecomparator 28 is a digital logic “1” when the input at the positive input terminal is higher than the voltage at the negative input terminal. The output ofcomparator 18 is a logic “0” when the input at the positive input terminal is lower than the voltage at the negative input terminal. The output of thecomparator 28 is labeled “AM After Threshold Detection” in FIG. 2 and is applied to a field programmable gate array (FPGA) 44 contained inDSP 4 shown in FIG. 3. The FPGA 44 measures the pulse width of thecomparator 28 output. This pulse width is screened to be within the programmable minimum and maximum limits, which typically range between 10 μs to 150 μs. A pulse width, that does not pass the pulse width screening, will not enable the frequency estimator within theDSP 4, as shown in FIG. 4, the tag software flow diagram. An invalid pulse will cause no action in the frequency estimator. Only after a pulse width has passed the pulse width screening will the frequency estimator be enabled. - The signal flow in the
FM receiver 3 continues from the output of thepower splitter 23 though thelow noise amplifier 29. The FM receiver shares common parts with theAM receiver 2 from theantenna 1 to the input ofpower splitter 23 as illustrated in FIGS. 2, 5 and 6. In the FM receiver is a new input signal labeled “LO” (Local Oscillator) which is utilized as shown in FIG. 6. This signal is generated from the input LFM pulse waveform that shares common parts with the AM receiver and FM receiver from theantenna 1 to the input of the seconddirectional coupler 15, as illustrated in FIGS. 2, 5 and 6. At thecoupler 15, the signal passes through the main line of seconddirectional coupler 15, and then through thedelay line 16. The time delay, of thedelay line 16, in the preferred embodiment is 60 ns with the delay element being a coaxial cable. However, the design of thedelay line 16 will operate with any delay as long as the delay is constant over frequency. Other delay elements can be used such as SAW, BAW, optical fiber, tuned filter and digital circuits such as DRFM. These alternate delay elements may require support circuits that are not shown here, but are well known in the art. The output ofdelay line 16 then passes through the coupled side of the thirddirectional coupler 17. The output of the thirddirectional coupler 17 then passes through the LO lownoise buffer amplifier 34. The output of thebuffer amplifier 34 is then fed into the LO input of themixer 30. - The LO signal at the
mixer 30 input is a delayed replica of the LFM input waveform received at theantenna 1. This LO signal and themixer 30 comprise the frequency detector in theFM receiver 3 of the original LFM pulse waveform. The frequency demodulation is accomplished by multiplying the delayed signal (LO) with the non-delayed signal in themixer 30. The formula for the demodulation output of thelow pass filter 31 after themixer 30, for an LFM input, is given below: - Frequency output (Hz)=delay (seconds)×LFM (Hz/second).
- The following is an example calculation of the above formula. The tag has a time delay of 60 ns, and an input LFM waveform is applied at 8.5 GHz with a positive-slope ramp deviation of 100 MHz and a pulse width of 27.7 μs. The frequency output is60 e-9×100
e 6/27.7 e-6 or approximately 216 KHz. FIG. 7 shows the output of thelow pass filter 31 for this input signal. - After the
low pass filter 31, the FM signal is limited with a zero-crossingcomparator 32 that converts the signal into a one bit digital value and the sampling of the one bit digital value is controlled by the Sample Clock input, from the FPGA 44 of theDSP 4 as shown in FIG. 3, to thesampler 33.Sampler 33 may be a clocked register or an other circuit that can hold the value of the digital bit until the next sample clock is received by thesampler 33. The output ofsampler 33 is labeled “LFM After Sampling”. The output ofsampler 33 is applied to themicroprocessor 42 in theDSP 4 in FIG. 3, for storage in thememory RAM 41 for further processing by themicroprocessor 42. It is only processed if the output ofcomparator 28 is within the preprogrammed valid range of widths. - FIG. 4 is a diagram of the processing steps of the microprocessor. The output of the
FM receiver 3, which is the output of thesampler 33, is fed into themicroprocessor 42 for frequency estimating. The frequency estimator counts the zero-crossings of the demodulated FM signal from the output ofsampler 33, and calculates the average frequency during the valid receive interval. The code for this frequency estimator is provided in FIG. 7B. In FIG. 7B, the variable “SS” represents a valid receive interval. If the variable “SS” is not equal to 1, then the output of thethreshold comparator 28 is not adigital logic 1. All received signals that do not generate adigital logic 1 at the output ofcomparator 28 are considered to be noise and are not processed further. The variable “SLIN” is the digital bit in the output signal orcomparator 33 labeled as “FM After Sampling”. The variable “clock” is a 2 MHz sample clock. The actual frequency can be changed but the program must make the variable “clock” equal to the actual sample clock rate used. The variable “data” is the sample length. The sample length dynamically changes with the width of the input pulse. - In the previous example, the sample length would be 2 Mhz×27.7 μs, or approximately 55 samples. Using the frequency estimator of FIG. 7B and the 100 MHz deviation from the example, the calculated frequency output is 219 KHz. This is within 2% of the theoretical value of 216 KHz and is satisfactory for the RFID system. The FM processing continues in FIG. 4, where the measured frequency is compared to a table of valid frequencies. If the comparison is true, then the tag builds a message from the data that was encoded in the pulse width and frequency deviations of the received input LFM pulse waveform. Although this implementation is described in software, faster operation could be obtained using a matched filter in the DSP section.
- The
tag 10 checks the validity of the data in the message by examining the data fields and performing a checksum. An example of a checksum is theCCITT 16 bit CRC (cyclic redundancy check). However, other types of checksum may be used since the type of checking does not materially affect the performance of the tag. The tag's 10 checksum is compared with the transmitted checksum and if they match then the message is valid and the tag declares Message Complete. A valid message will typically contain the radar pulse width, radar PRI, and transmitted checksum, and may include other information for thetag 10 or about the radar depending on the system operation. - A valid message will enable data transmission from the
tag 10. Thetag 10 must align its transmission so that its pulse is on top of, or synchronous with, the radar pulse. Thetag 10 does this by loading the initial radar pulse width and radar PRI (pulse repetition interval) in a counter of theDSP 4, but not starting the counter. These values in the counter are the pulse width and PRI from the valid message that were obtained after the tag declares Message Complete. At the starting edge of the initial radar pulse, a digital control signal, download_intn, is generated, which is a request by the FPGA 44 to themicroprocessor 42 for modulation data. This data is used in the validating of any decoded valid AM and FM demodulated output to theDSP 4. From the data decoded from the initial SAR pulse, thetag 10 estimates when the next pulse will be received. The exact timing for the ld_symbol during the initial pulse is not critical, however the ld_symbol must occur before the first transmit pulse. The download_intn is a request from the FPGA 44 to themicroprocessor 42 for new modulation data. This data is used in the next pulse one PRI later. Ld_symbol latches the modulation data into the FPGA 44 before rf_detect occurs. Thetag 10 waits for the leading edge of the initial radar pulse and when it detects the leading edge it transmits after the initial PRI. During the following pulses the tag loads the counter with the actual radar PRI and so transmits this PRI repeatedly. The PRI timer gets resynchronized to each incoming RF to take into account inaccuracies in the FPGA clock. After the initial PRI, an uplink gate signal is generated to control the waveform XMT, which is the envelope of the RF transmission from the tag. In this way thetag 10 becomes synchronized with future pulses from the radar. The error between the tag pulse and radar pulse is typically less than±100 ns. The process of synchronizing the tag with the radar is illustrated in FIG. 8. The following is a description of the signals named in the figure: - “rf” is the envelope of the received RF signal in the LFM pulse waveform;
- “latency” is the time delay from the received RF to the digital output of the
threshold detector 28, labeled as “AM After Threshold Detector”, and occurs due to circuit delay in theAM receiver 2; - “init_pri” is the initial PRI transmission from the
tag 10; - “gate” is the width of the received LFM pulse waveform;
- “pri” is the PRI of the received LEM pulse waveform, and the PRI of all tag transmissions except for the initial PRI;
- “rf_detect” is the same as the output of the
threshold detector 28, labeled as “AM After Threshold Detector”; - “uplink gate” is the pulse width of the tag transmission;
- “download_intn” is a digital word signal sent by the FPGA44 to the
microprocessor 42 and is a request to themicroprocessor 42 for modulation data; - “ld_symbol” initializes the FPGA44 with new modulation information from the
microprocessor 42; - “xmt” is the envelope of the RF transmission from the
tag 10; - “chopping signal” refers to a toggling state of the controlling signals S1 and S2 that control
RF switch S1 13 andRF switch S2 20 respectively. - The LFM pulse waveform signal flow during transmit is shown in FIG. 9. The dashed line was previously described in the received signal flow and is also part of the transmission. The LFM input pulse waveform uses the same components as the
AM 2 andFM 3 receivers up to the input of the seconddirectional coupler 15. The LFM pulse waveform signal passes through the main line of seconddirectional coupler 15, followed by thedelay line 16. It then passes through the main line of thirddirectional coupler 17. The LFM pulse waveform signal that was stored indelay line 16, after passing through thedirectional coupler 17 is electrically coupled to thevariable attenuator 18,phase modulator 19, RF switch S2 20 (closed in transmit),power amplifier 21, back through the main line of the firstdirectional coupler 12 and throughbandpass filter 11 and transmitted from theantenna 1. - To allow the tag to share the
same antenna 1 for both receive and transmit, the chopping signals S1 and S2 use the same frequency and the length of delay for thedelay line 16 is based on the frequency used in the timing of chopping signals S1 and S2. The timing of S1 and S2 is shown in FIG. 10 for a 60 nsdelay line 16. In this figure the receive time is 60 ns, transmit time is 60 ns, and the blanking time (when the tag is neither transmitting nor receiving) is 60 ns. The transition time from on to off and vice versa due to the RF switchesS1 13 andS2 20 is 10 ns. A complete cycle in the example in FIG. 10 is 180 ns. The blanking interval in FIG. 10 prevents oscillations due to reflections from nearby objects. - Some systems require randomizing the blanking time to prevent the radar from accidentally locking onto the spectral lines that are generated during the chopping of the RF signal. The randomizing circuit for chop timing is shown in FIG. 11a. The blanking time changes pseudo-randomly each cycle from 60 ns to 200 ns with a resolution of 20 ns. The design is a [7,1] maximal length generator and the initial seed is binary 1111111. The sequence repeats every 127 chop cycles. The circuits for the chop timing and chop randomization are contained in the FPGA 44. Other randomizing circuit designs could also be utilized.
- The pulse is modulated with tag data using the
signal phase modulator 19 as shown in FIG. 2, by the signal labeled “PM”. Thephase modulator 19 is a 5-bit phase shifter and is capable of placing frequency modulation and phase modulation on the RF signal. A typical modulation consists of a linear frequency slope and a bi-phase value. During the process of modulation, the binary data in the message is encoded. An example of an encoding scheme is shown in FIG. 11b Three bits of data from the tag are placed on each pulse using different states of frequency deviation and phase. However, the tag is capable of generating other modulation values, and the design is capable of a broad range of frequency and phase modulation. - The RF output from the
tag 10 for the example in FIG. 11b is shown in FIG. 12. It shows that the tag adds chop modulation, phase modulation, and linear frequency modulation (LFM) to the radar pulse. The transmit time of the tag is synchronous with the radar pulse. The plus symbol in the LFM+ indicates that the tag has modified the LFM slope of the original radar LFM signal. - The tag adjusts the gain in the transmit path using the AM signal at the
variable RF attenuator 18 in FIG. 2, the signal being generated from themicroprocessor 42 in FIG. 3. The AM signal controls a 5-bit digitally tunable RF attenuator. However, the signal may also be an analog voltage in another implementation and the type of RF attenuator does not materially affect thetag 10. Themicroprocessor 42 sets the amplitude value of the AM. The gain is typically set to 63 dB (peak) as measured from the antenna RF input to the antenna RF output. - FIG. 13a is a partial block diagram of the
FM receiver 3 in FIG. 2. These components can not distinguish between increasing and decreasing LFM signals, because they respond equally to positive and negative slopes from the FM signal. The preferred embodiment uses amixer 30, followed by alow pass filter 31, a zero-crossingdetector 32 and asampler 33. The output of thesampler 33 is labeled LFM After Sampling. This output is then processed by themicroprocessor 42 in theDSP 4. - This restriction is overcome by quadrature detection and processing of the I and Q signals as shown in FIG. 13b of FIG. 13. FIG. 13b shows the block diagram of the revised design for calculating the slope. The
amplifiers power splitter 100 is now placed between the output ofamplifier 34 andmixer 30. The 90°power splitter 100 produces two outputs, one is in-phase with the input signal and the other output is out of phase by 90° and is in quadrature-phase with the input. Each output is processed by a separate but identical set of components. The outputs of the two sets of components are labeled “FM In-Phase” (I) and “FM Quadrature-Phase” (Q) . The output from the revisedFM receiver 3 labeled “FM in-phase” uses the component set: mixer 30I, lowpass filter 31I, zero-crossing detector 32I and sampler 33I. The output from the revisedFM receiver 3 labeled “FM Quadrature-Phase” uses the component set: mixer 30Q,lowpass filter 31Q, zero-crossingdetector 32Q and sampler 33Q. - These two output signals are further processed by the
microprocessor 42 in the DSP4, to find the polarity of the slope. The analog outputs of I and Q prior to digitizing are shown in FIG. 14a, using the same input example as previously discussed. - The processing steps for the slope polarity are shown in FIG. 14b. SLOPE[n] is the output and is initialized to zero. The result is +1 when the slope is positive and −1 when the slope is negative. The data processing is accomplished by the
microprocessor 42 inside theDSP 4. The output of the slope polarity is shown in FIG. 15 for the positive slope of the example. The top trace is the detection output of theAM receiver 2threshold comparator 28 and is shown for reference only, and the bottom trace is the slope polarity scaled by ½. FIG. 16 is the output for a negative slope. - The algorithm in FIG. 14b provides multiple outputs, separated in time but having identical value, and any one of the multiple values is suitable for defining polarity. Typically the
microprocessor 42 will select the first value. The number of multiple values is a function of the input FM deviation and pulse width. - The above teachings are illustrations of preferred embodiment of the present invention. It should be noted that modifications to the invention, such as would occur to those of ordinary skill in the art, are also within the intended scope of the present invention.
Claims (26)
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US09/804,355 US6791489B1 (en) | 2001-03-12 | 2001-03-12 | Radio tag for LFM radar |
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US09/804,355 US6791489B1 (en) | 2001-03-12 | 2001-03-12 | Radio tag for LFM radar |
Publications (2)
Publication Number | Publication Date |
---|---|
US6791489B1 US6791489B1 (en) | 2004-09-14 |
US20040178944A1 true US20040178944A1 (en) | 2004-09-16 |
Family
ID=32928130
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
US09/804,355 Expired - Lifetime US6791489B1 (en) | 2001-03-12 | 2001-03-12 | Radio tag for LFM radar |
Country Status (1)
Country | Link |
---|---|
US (1) | US6791489B1 (en) |
Cited By (21)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US20040095995A1 (en) * | 2002-11-20 | 2004-05-20 | Matreci Robert J. | Method for determining imbalance in a vector signal modulator |
US20050169401A1 (en) * | 2004-02-02 | 2005-08-04 | Satius, Inc. | Frequency modulated OFDM over various communication media |
US20050206551A1 (en) * | 2002-01-22 | 2005-09-22 | Komiak James J | Digital rf tag |
US20050212692A1 (en) * | 2004-03-26 | 2005-09-29 | Iny David R | 2-d range hopping spread spectrum encoder/decoder system for RF tags |
US20060232463A1 (en) * | 2005-04-19 | 2006-10-19 | Northrop Grumman Corporation | Joint stars embedded data link |
US20070081585A1 (en) * | 2004-01-16 | 2007-04-12 | Noriharu Suematsu | Power supply apparatus and power supply method |
WO2008041252A1 (en) * | 2006-10-06 | 2008-04-10 | Space Engineering S.P.A. | Active transponder, particularly for synthetic aperture radar, or sar, systems |
US20080247447A1 (en) * | 2004-09-08 | 2008-10-09 | Satius, Inc. | Apparatus and method for transmitting digital data over various communication media |
US20100013700A1 (en) * | 2005-06-03 | 2010-01-21 | Space Engineering S.P.A. | Active transponder, particularly for synthetic aperture radar, or sar, systems |
US20110110459A1 (en) * | 2004-02-02 | 2011-05-12 | Satius Holding, Inc. | FM OFDM over various communication media |
US20120268308A1 (en) * | 2008-06-05 | 2012-10-25 | Keystone Technology Solutions, Llc | Systems and Methods to Use Radar in RFID Systems |
WO2013022877A1 (en) * | 2011-08-08 | 2013-02-14 | Strata Proximity Systems, Llc | Proximity detection system with concurrent rf and magnetic fields |
CN102981162A (en) * | 2012-12-11 | 2013-03-20 | 电子科技大学 | Spatial synchronization device and synchronization method for bistatic SAR |
WO2013184232A1 (en) * | 2012-06-08 | 2013-12-12 | Raytheon Company | Wideband low latency repeater and methods |
US9030301B2 (en) | 2008-06-05 | 2015-05-12 | Micron Technology, Inc. | Systems and methods to determine kinematical parameters using RFID tags |
US9285457B2 (en) | 2011-12-27 | 2016-03-15 | Lattice Semiconductor Corporation | High-accuracy detection in collaborative tracking systems |
US9477863B2 (en) | 2008-06-05 | 2016-10-25 | Micron Technology, Inc. | Systems and methods to determine motion parameters using RFID tags |
WO2018162756A1 (en) | 2017-03-10 | 2018-09-13 | Thales Alenia Space Italia S.P.A. Con Unico Socio | Innovative locator system, related low power consumption regenerative transponder and related localization method and service |
US20200220707A1 (en) * | 2019-01-09 | 2020-07-09 | Electronics And Telecommunications Research Institute | Method and apparatus for backscatter communication of pattern-based demodulation |
WO2021254183A1 (en) * | 2020-06-16 | 2021-12-23 | 华为技术有限公司 | Communication apparatus for transmitting signal, and signal transmission method |
US11237246B1 (en) * | 2020-07-13 | 2022-02-01 | Dbtsystems Llc | Pulsed radar with multispectral modulation to reduce interference, increase PRF, and improve doppler velocity measurement |
Families Citing this family (14)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US8190162B2 (en) * | 2003-09-15 | 2012-05-29 | Broadcom Corporation | Radar detection circuit for a WLAN transceiver |
US7030805B2 (en) * | 2004-07-23 | 2006-04-18 | Sandia Corporation | Methods and system suppressing clutter in a gain-block, radar-responsive tag system |
WO2006130988A1 (en) * | 2005-06-10 | 2006-12-14 | Telecommunications Research Laboratories | Wireless communication system |
KR100666340B1 (en) | 2006-01-17 | 2007-01-09 | 인티그런트 테크놀로지즈(주) | Rfid reader and rfid system |
US20080131133A1 (en) * | 2006-05-17 | 2008-06-05 | Blunt Shannon D | Low sinr backscatter communications system and method |
US20090243854A1 (en) * | 2008-03-26 | 2009-10-01 | Paul Raymond Scheid | Wireless aircraft maintenance log |
US20110140866A1 (en) * | 2008-03-26 | 2011-06-16 | Paul Raymond Scheid | Wireless aircraft maintenance log |
US8527240B2 (en) * | 2008-03-26 | 2013-09-03 | United Technologies Corporation | Wireless sensor assembly for an aircraft component |
US20090132697A1 (en) * | 2008-04-04 | 2009-05-21 | Paul Raymond Scheid | Integration of passenger and flight operation communications |
EP2407799B1 (en) * | 2010-07-16 | 2018-04-11 | Sivers Ima AB | Method and device for continuous wave radar measurements |
US10018718B1 (en) * | 2015-10-29 | 2018-07-10 | National Technology & Engineering Solutions Of Sandia, Llc | Artifact reduction within a SAR image |
US9681388B2 (en) * | 2015-11-05 | 2017-06-13 | Cox Communications, Inc. | Systems and methods for low power RF data reception |
RU2609525C1 (en) * | 2016-06-28 | 2017-02-02 | Федеральное государственное казенное военное образовательное учреждение высшего образования "Военная академия воздушно-космической обороны имени Маршала Советского Союза Г.К. Жукова" Министерства обороны Российской Федерации | Method of generating signals and transmitting information in radar identification system |
CN116449304B (en) * | 2023-04-19 | 2023-09-08 | 扬州宇安电子科技有限公司 | SAR emission pulse arrival time measurement method based on frequency measurement |
Citations (26)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US3969725A (en) * | 1974-06-12 | 1976-07-13 | The United States Of America As Represented By The Secretary Of Transportation | Distance measuring equipment |
US4109247A (en) * | 1975-07-03 | 1978-08-22 | Rca Corporation | Clutter free communications radar |
US4746830A (en) * | 1986-03-14 | 1988-05-24 | Holland William R | Electronic surveillance and identification |
US4786906A (en) * | 1985-06-17 | 1988-11-22 | Forsvarets Forskningstjeneste | Method of motion compensation in synthetic aperture radar target imaging and a system for performing the method |
US5051741A (en) * | 1990-03-28 | 1991-09-24 | Wesby Philip B | Locating system |
US5469170A (en) * | 1994-10-20 | 1995-11-21 | The United States Of America As Represented By The Secretary Of The Army | Passive SAW-ID tags using a chirp transducer |
US5486830A (en) * | 1994-04-06 | 1996-01-23 | The United States Of America As Represented By The United States Department Of Energy | Radar transponder apparatus and signal processing technique |
US5495248A (en) * | 1992-11-25 | 1996-02-27 | Sachio Uehara, Director General, Technical Research And Development Institute, Japan Defence Agency | Stabilizing method of synthetic aperture radar and position determining method thereof |
US5525993A (en) * | 1995-05-12 | 1996-06-11 | The Regents Of The University Of California | Microwave noncontact identification transponder using subharmonic interrogation and method of using the same |
US5565858A (en) * | 1994-09-14 | 1996-10-15 | Northrop Grumman Corporation | Electronic inventory system for stacked containers |
US5602538A (en) * | 1994-07-27 | 1997-02-11 | Texas Instruments Incorporated | Apparatus and method for identifying multiple transponders |
US5627517A (en) * | 1995-11-01 | 1997-05-06 | Xerox Corporation | Decentralized tracking and routing system wherein packages are associated with active tags |
US5629691A (en) * | 1995-05-26 | 1997-05-13 | Hughes Electronics | Airport surface monitoring and runway incursion warning system |
US5640151A (en) * | 1990-06-15 | 1997-06-17 | Texas Instruments Incorporated | Communication system for communicating with tags |
US5767802A (en) * | 1997-01-10 | 1998-06-16 | Northrop Grumman Corporation | IFF system including a low radar cross-section synthetic aperture radar (SAR) |
US5774876A (en) * | 1996-06-26 | 1998-06-30 | Par Government Systems Corporation | Managing assets with active electronic tags |
US5798893A (en) * | 1995-11-28 | 1998-08-25 | Daewoo Electronics Co., Ltd. | Head drum assembly for use in a video cassette recorder |
US5804810A (en) * | 1996-06-26 | 1998-09-08 | Par Government Systems Corporation | Communicating with electronic tags |
US5821895A (en) * | 1995-05-24 | 1998-10-13 | Deutsche Forschungsanstalt Fur Luft-Und Raumfahrt E. | Method and device for locating and identifying objects by means of an encoded transponder |
US5822683A (en) * | 1996-04-05 | 1998-10-13 | Ball Aerospace And Technologies Corp. | Pseudo-passive transponder device |
US5856788A (en) * | 1996-03-12 | 1999-01-05 | Single Chips Systems Corp. | Method and apparatus for radiofrequency identification tags |
US5872520A (en) * | 1995-10-24 | 1999-02-16 | Siemens Aktiengesellschaft | Identification and/or sensor system |
US5886902A (en) * | 1997-02-03 | 1999-03-23 | Digital Equipment Corporation | Method for optimizing items represented in permutation spaces |
US5892441A (en) * | 1996-06-26 | 1999-04-06 | Par Government Systems Corporation | Sensing with active electronic tags |
US6433671B1 (en) * | 1996-11-29 | 2002-08-13 | X-Cyte, Inc. | Dual mode transmitter-receiver and decoder for RF transponder tags |
US6577266B1 (en) * | 2001-10-15 | 2003-06-10 | Sandia Corporation | Transponder data processing methods and systems |
Family Cites Families (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4724427A (en) | 1986-07-18 | 1988-02-09 | B. I. Incorporated | Transponder device |
US5798693A (en) | 1995-06-07 | 1998-08-25 | Engellenner; Thomas J. | Electronic locating systems |
-
2001
- 2001-03-12 US US09/804,355 patent/US6791489B1/en not_active Expired - Lifetime
Patent Citations (26)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US3969725A (en) * | 1974-06-12 | 1976-07-13 | The United States Of America As Represented By The Secretary Of Transportation | Distance measuring equipment |
US4109247A (en) * | 1975-07-03 | 1978-08-22 | Rca Corporation | Clutter free communications radar |
US4786906A (en) * | 1985-06-17 | 1988-11-22 | Forsvarets Forskningstjeneste | Method of motion compensation in synthetic aperture radar target imaging and a system for performing the method |
US4746830A (en) * | 1986-03-14 | 1988-05-24 | Holland William R | Electronic surveillance and identification |
US5051741A (en) * | 1990-03-28 | 1991-09-24 | Wesby Philip B | Locating system |
US5640151A (en) * | 1990-06-15 | 1997-06-17 | Texas Instruments Incorporated | Communication system for communicating with tags |
US5495248A (en) * | 1992-11-25 | 1996-02-27 | Sachio Uehara, Director General, Technical Research And Development Institute, Japan Defence Agency | Stabilizing method of synthetic aperture radar and position determining method thereof |
US5486830A (en) * | 1994-04-06 | 1996-01-23 | The United States Of America As Represented By The United States Department Of Energy | Radar transponder apparatus and signal processing technique |
US5602538A (en) * | 1994-07-27 | 1997-02-11 | Texas Instruments Incorporated | Apparatus and method for identifying multiple transponders |
US5565858A (en) * | 1994-09-14 | 1996-10-15 | Northrop Grumman Corporation | Electronic inventory system for stacked containers |
US5469170A (en) * | 1994-10-20 | 1995-11-21 | The United States Of America As Represented By The Secretary Of The Army | Passive SAW-ID tags using a chirp transducer |
US5525993A (en) * | 1995-05-12 | 1996-06-11 | The Regents Of The University Of California | Microwave noncontact identification transponder using subharmonic interrogation and method of using the same |
US5821895A (en) * | 1995-05-24 | 1998-10-13 | Deutsche Forschungsanstalt Fur Luft-Und Raumfahrt E. | Method and device for locating and identifying objects by means of an encoded transponder |
US5629691A (en) * | 1995-05-26 | 1997-05-13 | Hughes Electronics | Airport surface monitoring and runway incursion warning system |
US5872520A (en) * | 1995-10-24 | 1999-02-16 | Siemens Aktiengesellschaft | Identification and/or sensor system |
US5627517A (en) * | 1995-11-01 | 1997-05-06 | Xerox Corporation | Decentralized tracking and routing system wherein packages are associated with active tags |
US5798893A (en) * | 1995-11-28 | 1998-08-25 | Daewoo Electronics Co., Ltd. | Head drum assembly for use in a video cassette recorder |
US5856788A (en) * | 1996-03-12 | 1999-01-05 | Single Chips Systems Corp. | Method and apparatus for radiofrequency identification tags |
US5822683A (en) * | 1996-04-05 | 1998-10-13 | Ball Aerospace And Technologies Corp. | Pseudo-passive transponder device |
US5804810A (en) * | 1996-06-26 | 1998-09-08 | Par Government Systems Corporation | Communicating with electronic tags |
US5774876A (en) * | 1996-06-26 | 1998-06-30 | Par Government Systems Corporation | Managing assets with active electronic tags |
US5892441A (en) * | 1996-06-26 | 1999-04-06 | Par Government Systems Corporation | Sensing with active electronic tags |
US6433671B1 (en) * | 1996-11-29 | 2002-08-13 | X-Cyte, Inc. | Dual mode transmitter-receiver and decoder for RF transponder tags |
US5767802A (en) * | 1997-01-10 | 1998-06-16 | Northrop Grumman Corporation | IFF system including a low radar cross-section synthetic aperture radar (SAR) |
US5886902A (en) * | 1997-02-03 | 1999-03-23 | Digital Equipment Corporation | Method for optimizing items represented in permutation spaces |
US6577266B1 (en) * | 2001-10-15 | 2003-06-10 | Sandia Corporation | Transponder data processing methods and systems |
Cited By (50)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US20050206551A1 (en) * | 2002-01-22 | 2005-09-22 | Komiak James J | Digital rf tag |
US7106245B2 (en) * | 2002-01-22 | 2006-09-12 | Bae Systems Information And Electronic Systems Integration Inc. | Digital RF tag |
US20040095995A1 (en) * | 2002-11-20 | 2004-05-20 | Matreci Robert J. | Method for determining imbalance in a vector signal modulator |
US7180937B2 (en) * | 2002-11-20 | 2007-02-20 | Agilent Technologies, Inc. | Method for determining imbalance in a vector signal modulator |
US20070081585A1 (en) * | 2004-01-16 | 2007-04-12 | Noriharu Suematsu | Power supply apparatus and power supply method |
US8379758B2 (en) | 2004-01-16 | 2013-02-19 | Mitsubishi Denki Kabushiki Kaisha | Power supply apparatus and power supply method |
US20100329385A1 (en) * | 2004-01-16 | 2010-12-30 | Noriharu Suematsu | Power supply apparatus and power supply method |
US7817742B2 (en) * | 2004-01-16 | 2010-10-19 | Mitsubishi Denki Kabushiki Kaisha | Power supply apparatus and power supply method |
US20110110459A1 (en) * | 2004-02-02 | 2011-05-12 | Satius Holding, Inc. | FM OFDM over various communication media |
US11152971B2 (en) * | 2004-02-02 | 2021-10-19 | Charles Abraham | Frequency modulated OFDM over various communication media |
US20050169401A1 (en) * | 2004-02-02 | 2005-08-04 | Satius, Inc. | Frequency modulated OFDM over various communication media |
US7071866B2 (en) * | 2004-03-26 | 2006-07-04 | Northrop Grumman Corporation | 2-d range hopping spread spectrum encoder/decoder system for RF tags |
US20050212692A1 (en) * | 2004-03-26 | 2005-09-29 | Iny David R | 2-d range hopping spread spectrum encoder/decoder system for RF tags |
US20080247447A1 (en) * | 2004-09-08 | 2008-10-09 | Satius, Inc. | Apparatus and method for transmitting digital data over various communication media |
US8724526B2 (en) | 2004-09-08 | 2014-05-13 | Satius Holding, Inc. | Apparatus and method for transmitting digital data over various communication media |
US7221308B2 (en) | 2005-04-19 | 2007-05-22 | Northrop Grumman Corporation | Joint stars embedded data link |
US20060232463A1 (en) * | 2005-04-19 | 2006-10-19 | Northrop Grumman Corporation | Joint stars embedded data link |
US20100013700A1 (en) * | 2005-06-03 | 2010-01-21 | Space Engineering S.P.A. | Active transponder, particularly for synthetic aperture radar, or sar, systems |
US8384582B2 (en) | 2005-06-03 | 2013-02-26 | Space Engineering S.P.A. | Active transponder, particularly for synthetic aperture radar, or SAR, systems |
WO2008041252A1 (en) * | 2006-10-06 | 2008-04-10 | Space Engineering S.P.A. | Active transponder, particularly for synthetic aperture radar, or sar, systems |
US8830062B2 (en) * | 2008-06-05 | 2014-09-09 | Micron Technology, Inc. | Systems and methods to use radar in RFID systems |
US10162992B2 (en) | 2008-06-05 | 2018-12-25 | Micron Technology, Inc. | Systems and methods to determine kinematical parameters using RFID tags |
US11403473B2 (en) | 2008-06-05 | 2022-08-02 | Micron Technology, Inc. | Systems and methods to determine kinematical parameters |
US11237262B2 (en) | 2008-06-05 | 2022-02-01 | Micron Technology, Inc. | Systems and methods to use radar in RFID systems |
US20120268308A1 (en) * | 2008-06-05 | 2012-10-25 | Keystone Technology Solutions, Llc | Systems and Methods to Use Radar in RFID Systems |
US11042720B2 (en) | 2008-06-05 | 2021-06-22 | Micron Technology, Inc. | Systems and methods to determine motion parameters using RFID tags |
US9030301B2 (en) | 2008-06-05 | 2015-05-12 | Micron Technology, Inc. | Systems and methods to determine kinematical parameters using RFID tags |
US10824829B2 (en) | 2008-06-05 | 2020-11-03 | Micron Technology, Inc. | Systems and methods to determine kinematical parameters |
US10650200B2 (en) | 2008-06-05 | 2020-05-12 | Micron Technology, Inc. | Systems and methods to determine motion parameters using RFID tags |
US10592711B2 (en) | 2008-06-05 | 2020-03-17 | Micron Technology, Inc. | Systems and methods to determine kinematical parameters |
US9477863B2 (en) | 2008-06-05 | 2016-10-25 | Micron Technology, Inc. | Systems and methods to determine motion parameters using RFID tags |
US10571558B2 (en) | 2008-06-05 | 2020-02-25 | Micron Technology, Inc. | Systems and methods to use radar in RFID systems |
US9690961B2 (en) | 2008-06-05 | 2017-06-27 | Micron Technology, Inc. | Systems and methods to determine kinematical parameters using RFID tags |
US10438031B2 (en) | 2008-06-05 | 2019-10-08 | Micron Technology, Inc. | Systems and methods to determine motion parameters using RFID tags |
US9081046B2 (en) * | 2011-08-08 | 2015-07-14 | Strata Safety Products, Llc | Proximity detection system with concurrent RF and magnetic fields |
AU2012294530B2 (en) * | 2011-08-08 | 2015-05-28 | Strata Safety Products, Llc | Proximity detection system with concurrent RF and magnetic fields |
US9805579B2 (en) | 2011-08-08 | 2017-10-31 | Strata Safety Products, Llc | Proximity detection system with concurrent RF and magnetic fields |
AU2015218535B2 (en) * | 2011-08-08 | 2017-04-20 | Strata Safety Products, Llc | Proximity detection system with concurrent RF and magnetic fields |
US20130038320A1 (en) * | 2011-08-08 | 2013-02-14 | Larry D. Frederick | Proximity detection system with concurrent rf and magnetic fields |
WO2013022877A1 (en) * | 2011-08-08 | 2013-02-14 | Strata Proximity Systems, Llc | Proximity detection system with concurrent rf and magnetic fields |
US9285457B2 (en) | 2011-12-27 | 2016-03-15 | Lattice Semiconductor Corporation | High-accuracy detection in collaborative tracking systems |
US8761233B2 (en) | 2012-06-08 | 2014-06-24 | Raytheon Company | Wideband low latency repeater and methods |
WO2013184232A1 (en) * | 2012-06-08 | 2013-12-12 | Raytheon Company | Wideband low latency repeater and methods |
CN102981162A (en) * | 2012-12-11 | 2013-03-20 | 电子科技大学 | Spatial synchronization device and synchronization method for bistatic SAR |
WO2018162756A1 (en) | 2017-03-10 | 2018-09-13 | Thales Alenia Space Italia S.P.A. Con Unico Socio | Innovative locator system, related low power consumption regenerative transponder and related localization method and service |
US11372099B2 (en) * | 2017-03-10 | 2022-06-28 | Thales Alenia Space Italia S.P.A. Con Unico Socio | Innovative locator system, related low power consumption regenerative transponder and related localization method and service |
US20200220707A1 (en) * | 2019-01-09 | 2020-07-09 | Electronics And Telecommunications Research Institute | Method and apparatus for backscatter communication of pattern-based demodulation |
US10944539B2 (en) * | 2019-01-09 | 2021-03-09 | Electronics And Telecommunications Research Institute | Method and apparatus for backscatter communication of pattern-based demodulation |
WO2021254183A1 (en) * | 2020-06-16 | 2021-12-23 | 华为技术有限公司 | Communication apparatus for transmitting signal, and signal transmission method |
US11237246B1 (en) * | 2020-07-13 | 2022-02-01 | Dbtsystems Llc | Pulsed radar with multispectral modulation to reduce interference, increase PRF, and improve doppler velocity measurement |
Also Published As
Publication number | Publication date |
---|---|
US6791489B1 (en) | 2004-09-14 |
Similar Documents
Publication | Publication Date | Title |
---|---|---|
US6791489B1 (en) | Radio tag for LFM radar | |
EP1290470B1 (en) | Low probability of intercept coherent radar altimeter | |
US6980613B2 (en) | Ultra-wideband correlating receiver | |
US5337054A (en) | Coherent processing tunnel diode ultra wideband receiver | |
US8175134B1 (en) | Radio communications system and method having decreased capability for detection by an adversary | |
US5657326A (en) | Radio based collision detection for wireless communication system | |
US7664160B2 (en) | Transmitting device, receiving device, and communication system | |
US20030108133A1 (en) | Apparatus and method for increasing received signal-to-noise ratio in a transmit reference ultra-wideband system | |
US6246729B1 (en) | Method and apparatus for decoding a phase encoded data signal | |
US8254437B2 (en) | Transmitting apparatus, receiving apparatus and communication system | |
US7456747B2 (en) | Method and device for suppressing a transmitting signal in a receiver of an RFID write/read unit | |
US8934579B2 (en) | Location system | |
US20080030336A1 (en) | Semiconductor integrated circuit device and receiving device | |
KR100953266B1 (en) | Sensor fron-end with phase coding capability | |
EP1745560B1 (en) | Wireless data transmission method and apparatus | |
EP1716433A1 (en) | Methods and apparatus for randomly modulating radar altimeters | |
US4661819A (en) | Doppler tolerant binary phase coded pulse compression system | |
US11774538B2 (en) | Methods and devices for transmitting a bit sequence and estimating the arrival time of same | |
CN114063010A (en) | Detection chip, detection device and detection method based on SOC technology | |
RU2811900C1 (en) | Method for energy detection of signal with compensation of combinational components under conditions of exposure to non-stationary interference | |
US3611142A (en) | Communication system with adaptive receiver | |
CN100583859C (en) | Pulse detection in wireless communications system | |
Pohl | State of the art in signal processing for wireless SAW sensing | |
EP0257977A2 (en) | Radar receiver | |
JPH04259876A (en) | Discriminating equipment |
Legal Events
Date | Code | Title | Description |
---|---|---|---|
AS | Assignment |
Owner name: NORTHROP GRUMMAN CORPORATION, CALIFORNIA Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNORS:RICHARDSON, DAVID L.;SOBSKI, ANDRZEJ;GORHAM, KENNETH D.;AND OTHERS;REEL/FRAME:011686/0391 Effective date: 20010227 |
|
STCF | Information on status: patent grant |
Free format text: PATENTED CASE |
|
FEPP | Fee payment procedure |
Free format text: PAYOR NUMBER ASSIGNED (ORIGINAL EVENT CODE: ASPN); ENTITY STATUS OF PATENT OWNER: LARGE ENTITY |
|
FPAY | Fee payment |
Year of fee payment: 4 |
|
AS | Assignment |
Owner name: NORTHROP GRUMMAN SYSTEMS CORPORATION, CALIFORNIA Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNOR:NORTHROP GRUMMAN CORPORATION;REEL/FRAME:025597/0505 Effective date: 20110104 |
|
FPAY | Fee payment |
Year of fee payment: 8 |
|
FPAY | Fee payment |
Year of fee payment: 12 |