US2300115A - Noise limiter - Google Patents

Noise limiter Download PDF

Info

Publication number
US2300115A
US2300115A US395371A US39537141A US2300115A US 2300115 A US2300115 A US 2300115A US 395371 A US395371 A US 395371A US 39537141 A US39537141 A US 39537141A US 2300115 A US2300115 A US 2300115A
Authority
US
United States
Prior art keywords
resistor
limiter
gate voltage
voltage
circuit
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.)
Expired - Lifetime
Application number
US395371A
Inventor
Gustave L Grundmann
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
RCA Corp
Original Assignee
RCA Corp
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by RCA Corp filed Critical RCA Corp
Priority to US395371A priority Critical patent/US2300115A/en
Application granted granted Critical
Publication of US2300115A publication Critical patent/US2300115A/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

Links

Images

Classifications

    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03G—CONTROL OF AMPLIFICATION
    • H03G11/00—Limiting amplitude; Limiting rate of change of amplitude ; Clipping in general
    • H03G11/04—Limiting level dependent on strength of signal; Limiting level dependent on strength of carrier on which signal is modulated

Definitions

  • My invention relates to noise limiters for radiol tive for noise reduction in a sound channel having a wide pass band such ⁇ as that in a television receiver.
  • the series type limiter is meant a limiter of the general type 4described in Kaar Patent 2,207,- 587 wherein the gate Voltage maintains a current flow through a diode and an output resistor in series while the soundl signal is applied to this series combination with 'a -polarity opposed to that of the gate voltage. If noise pulses in the signal exceed the gate voltage,vthe ow of diode current ceases for the durationfof the noise pulse thus limiting its amplitude.- l
  • An object of my invention is to provide an improved and simplified noise limiter circuit of the above-described type in which the gate voltage varies with changes in the average carrier.
  • a further object of theinvention is to provide an improved and simplified noise limiter circuit of the above-described type in which the ⁇ gate voltage varies in accordance with changes-in the average carrier and in which the gate voltage also substantially follows the useful modulation envelope of the sound modulatedY carrier wave.
  • FIG. 1 is a circuit diagram showing the wide band sound channel of a television receiverembodying my invention
  • Figure 2 is a circuit diagram similar to Fig. l but showing another embodiment ofthe invention.
  • Figure 3 is a circuit diagramV ⁇ showing another embodiment of the invention applied to a narrow band radioreceiver such'as a police receiver.
  • Fig. 1 shows the invention applied' to theV sound channel of a television receiver.
  • the 'receiverv ⁇ map comprise a first detector and a tunable oscillator indicated at IIJ for converting ⁇ the incoming picture signal and accompanyingy sound signal to intermediate frequency signals.
  • the soundsignal is supplied to an intermediate frequency amplifier indicated by the rectangle II which has a pass band several times the width of the vfrequency band occupied bythe sound signal being passed.
  • thev pass band may be 200 k. c. and the vsignall band-8 f or 10 k. c.
  • One I. F. amplifier tube and a'couplingV .r transformer are indicated generally I by y dotted lines inthe rectangle II.
  • the I. F. amplifier output is supplied through-a 1 coupling transformer I2 to the second detector4v This detector, in the example villustrated, 4
  • I3. comprises a diode I4 and a load resistor' I6 connected in series with each other and acrossthe secondary of the transformer I2.
  • the resistor IB is shunted by the usual bypass condenser Il for f bypassing the I. F. carrier wave.
  • the receiver is provided with a suitable 'auto-f i matic volume control ⁇ or A. V. C. circuit operating on average carrier.
  • A. V. C. circuit operating on average carrier.
  • the average carrier voltage appearing across the detector load resistor I6 is applied to-one-ormore of the I. F. amplifier tubes through a resistor-v I5.
  • the usual A. V. C. filtery condenser is shown'at 20.
  • the noise limiterA comprises a diode I8 and anY output resistor I9 connected in series with each other and across the loadr'esistor I6 through a coupling condenser 2
  • denser 24 connected thereacrossA for causing the gate or limiter voltage to follow the useful modulation envelope.
  • a flow of direct current is maintained through the limiter diode IB by means of a voltage drop produced ⁇ by the automatic volume control cur-v In the embodiment rent or a portion thereof; of Fig. l, this voltage drop is obtained from a relsistor 26 through which plate current flows to oneu or more of the I. F. amplifier tubes controlled'by the A. V. C. circuit.
  • the said voltage drop is applied to the series combination
  • the resistor 26 may be the usual filter resistor for the plate supply to one or more of the amplifier tube plates.
  • a filter' condenser is indicated From the foregoing it will vbe-apparent that there is applied to the limiterl diode 18a gatev Voltage which Varies withV changes in theaverage carrier and that this voltage and'thesignal voltcircuit Iii-24 causes the gate voltage to follow the luseful modulation envelope-fof the-sound modulated carrier wave.
  • the time constant of this R-C circuit is such that it has a cut-off just beyond the highest frequency component of the sound signal if the signal is to appear at the output circuit without any attenuation of the higher frequency signal components.
  • Fig. 2 The embodiment of the invention shown in Fig. 2 is similar to that shown in Fig. 1, thle difference being that the average carrier change in the gate voltage for the noise limiter in Fig. 2 isobtained from ⁇ the'screen grid circuits of the I. amplifiers vwhich have an A. V. C. control thereon. ⁇
  • Figs. 1 and 2 -like parts are indicated by the. same reference characters.
  • the average carrier variation of the gate voltage appearsacross a screen grid resistor SI whichis bypassed by the usual filter condenser 32.
  • One or more amplifier tubes controlled by the A. V. C. circuit may have their screen grids supplied by the operating voltage through the resistor SI. lIf a plurality of tubes is so supplied, the resistance of resistor 3
  • the operation of lthe kcircuit of Fig. 2 is similar to that of the circuit previously described. If the incomingsignal fades, the control grid of the I. F'. amplifier tube becomes lessnegative with the-result vthat the screen grid current increases and the gate voltage on the plate of the limiter diode I8 becomes less positive whereby the limiter diode becomes nonconducting at a lower value of signal voltage.
  • the circuit of Fig. 2 has an advantage over that of Fig. 1 inl that there is a degenerative action in the screen grid circuit whereby the changes in screen grid voltageare nearly linear with respect to changes in average carrier and, therefore, follow the output of the linear detector I4 rather closely.
  • FIG. 3 there is shown anv embodiment of the invention in which the average carrier variations of the gate voltage are obtained by means of an extra tube, not a signal amplifier tube, which is controlled by the A. V. C. voltage. Also, in Fig. 3, the invention is shown applied to a sound receiver, such as a police receiver, having a narrow band sound channel and the gate Voltage in the example illustrated is not made to follow the modulating envelope. Like parts in Figs. 1 and 3 are indicated by the same reference characters.
  • the receiver may comprise a rst detector and an oscillator indicated at 40 for supplying an I. F. signal to an amplifier 4I connected through a transformer to the second detector I3.
  • the detector I3 comprises a diode I4 having a load resistor 42 shunted by a condenser 43.
  • the noise limiter connections are substantially the same as in the other gures except that the average carrier variations in the gate voltage are obtained from across a resistor 44 which supplies plate voltage to the above-mentioned extra tube indicated at 46.
  • the tube 46 has a control electrode connected through a resistor 41 to a point on the A. V. C. circuit whereby the current through the plate resistor 44 will vary with the A. V. C. voltage and thus' vary the gate voltage applied to the limiter diode I8 in accordance with changes in average carrier.
  • condenser 5I which may be switched across the output resistor I9 for attenuating the higher frequency components of the sound signal for tone controll and/or additional noise reduction.
  • the condenser 5I has substantially greater capacity than the condenser 24 in the circuit of the other figures where the gatevoltage is made to follow the modulation envelope.
  • an important feature of the present invention is the provision of a simplified noise suppressor circuit of the series diode type in which the gate voltage follows both the average carrier and the useful modulation envelope, the circuit also hav- ;,ing the desirable feature of utilizing the full voltage output of the second detector.
  • a radio receiver having a sound channel which includes an amplifier, a detector supplie-d ,from said channel and having a load resistor across which the demodulated signal appears, a noise limiter of the series diode type connected across at least a portion of said load resistor, said limiter comprising a diode and an output resistor in series, an automatic volume control signal components passed by said channel, said channel including an amplifier, a detector supplied from said channel and having a load resistor across which the demodulated signal appears, a noise limiter of the series ⁇ diode type connected across substantially the entire portion of said load resistor, said limiter comprising a diode and an output resistor in series, an automatic volume control circuit for said amplier, means controlled by said circuit for applying to said limiter a gate voltage which varies with average carrier, and means for also causing the gate voltage to vary with the useful modulation envelope of the received carrier wave.
  • a radio receiver having an intermediate frequency amplifier with a pass band which is several times the width of the frequency band occupied by the signal components passed by said channel, a detector supplied from lsaid ampliiier and having a ⁇ load resistoracross-which the demodulated signal appears, a noise limiter of A the series diode type connected across at least a portion of said load resistor, an automatic volurne control circuit for controlling the gain of said amplifier, said limiter comprising a diode and an output resistor in series, a resistor through which voltage is supplied to an electrode of an amplifier tube in said amplifier, and .means for applying the voltage drop appearing across said last resistor to said limiter as at least a portion of its gate voltage whereby the gate voltage varies with average carrier.
  • a radio receiver having a sound channel including an amplifier tube, a. detector connected to be supplied with signal from said channel, said detector having a load resistor across which the demodulated signal appears, a noise limiter. connected across at least a portion of said load resistor, an automatic volume control circuit for. controlling the gain of said amplifier tube, la' resistor through which voltage is applied to screen grid electrode in said amplifier tube, and means for applying the voltage drop appearing across said last resistor to said noise limiter as at least a portion of its gate voltage whereby the gate voltage varies With average carrier.

Description

0i 27. 1942. s. x.. GRUNDMANN NOISE LIHITER Filed ay 21.1941
200 A1C-P l l T... Sb
/17' Df7: WILL/970B nventor attorney Patented Oct. 27, 1942 UNITED STATES PATENT co,F-rfifcEffN NOISE LIMITEE.'
Gustave L. Grundmann, Westmont, N. J., assign,
or to Radiol Corporation of America, a corporation of Delaware Application May 27, 1941, Serial No. 395,371
(Cl. Z50- 20) 6 Claims.
My invention relates to noise limiters for radiol tive for noise reduction in a sound channel having a wide pass band such` as that in a television receiver.
By the series type limiter is meant a limiter of the general type 4described in Kaar Patent 2,207,- 587 wherein the gate Voltage maintains a current flow through a diode and an output resistor in series while the soundl signal is applied to this series combination with 'a -polarity opposed to that of the gate voltage. If noise pulses in the signal exceed the gate voltage,vthe ow of diode current ceases for the durationfof the noise pulse thus limiting its amplitude.- l
An object of my invention is to provide an improved and simplified noise limiter circuit of the above-described type in which the gate voltage varies with changes in the average carrier.
A further object of theinvention is to provide an improved and simplified noise limiter circuit of the above-described type in which the `gate voltage varies in accordance with changes-in the average carrier and in which the gate voltage also substantially follows the useful modulation envelope of the sound modulatedY carrier wave.
The invention will be better understood from the following description taken in connection with the accompanying drawing in which Figure 1 is a circuit diagram showing the wide band sound channel of a television receiverembodying my invention,
Figure 2 is a circuit diagram similar to Fig. l but showing another embodiment ofthe invention, and
Figure 3 is a circuit diagramV `showing another embodiment of the invention applied to a narrow band radioreceiver such'as a police receiver.
Fig. 1 shows the invention applied' to theV sound channel of a television receiver.` `The 'receiverv `map comprise a first detector and a tunable oscillator indicated at IIJ for converting `the incoming picture signal and accompanyingy sound signal to intermediate frequency signals.
The soundsignal is supplied to an intermediate frequency amplifier indicated by the rectangle II which has a pass band several times the width of the vfrequency band occupied bythe sound signal being passed.- vvFor example, thev pass band may be 200 k. c. and the vsignall band-8 f or 10 k. c. One I. F. amplifier tube and a'couplingV .r transformer are indicated generally I by y dotted lines inthe rectangle II.
The I. F. amplifier output is supplied through-a 1 coupling transformer I2 to the second detector4v This detector, in the example villustrated, 4
I3. comprises a diode I4 and a load resistor' I6 connected in series with each other and acrossthe secondary of the transformer I2. The resistor IB is shunted by the usual bypass condenser Il for f bypassing the I. F. carrier wave.
The receiver is provided with a suitable 'auto-f i matic volume control `or A. V. C. circuit operating on average carrier. In the' example illustrated, the average carrier voltage appearing across the detector load resistor I6 is applied to-one-ormore of the I. F. amplifier tubes through a resistor-v I5. The usual A. V. C. filtery condenser is shown'at 20.
The noise limiterA comprises a diode I8 and anY output resistor I9 connected in series with each other and across the loadr'esistor I6 through a coupling condenser 2| and through a bypass condenser 22 of the' voltage divider 23.- Thus the A. C. sound signal' is applied across the series I8-I9. As explained hereinafter,
denser 24 connected thereacrossA for causing the gate or limiter voltage to follow the useful modulation envelope.
` A flow of direct current is maintained through the limiter diode IB by means of a voltage drop produced `by the automatic volume control cur-v In the embodiment rent or a portion thereof; of Fig. l, this voltage drop is obtained from a relsistor 26 through which plate current flows to oneu or more of the I. F. amplifier tubes controlled'by the A. V. C. circuit. The said voltage drop is applied to the series combination |8-I9 throughV a D.'C. connection comprising a high'impedance resistor 2'I. and the left hand vportion of the Voltage divider 23,' this portion having the `usual bypass condenser 28 thereacross.
The resistor 26 may be the usual filter resistor for the plate supply to one or more of the amplifier tube plates. A filter' condenser is indicated From the foregoing it will vbe-apparent that there is applied to the limiterl diode 18a gatev Voltage which Varies withV changes in theaverage carrier and that this voltage and'thesignal voltcircuit Iii-24 causes the gate voltage to follow the luseful modulation envelope-fof the-sound modulated carrier wave. The time constant of this R-C circuit is such that it has a cut-off just beyond the highest frequency component of the sound signal if the signal is to appear at the output circuit without any attenuation of the higher frequency signal components.
However, as described and claimed in the copending Holmes application Serial No. 395,346, led May'27,4 1941, it may be desirable to make the time constant of the R--C network I9--24 such that some of the higher frequency signal `components are attenuated. This may be de-V sirable for tone control purposes and/or for complementary attenuation in a system transmitting a pre-emphasized signal. In that case the gate voltage follows the modulation only approximately and some portions of the envelope representative of higher frequency components are attenuated.
In Figure 1, the values of certain elements have been indicated, merely by way of example, in ohms, megohms, and micromicrofarads.
The embodiment of the invention shown in Fig. 2 is similar to that shown in Fig. 1, thle difference being that the average carrier change in the gate voltage for the noise limiter in Fig. 2 isobtained from `the'screen grid circuits of the I. amplifiers vwhich have an A. V. C. control thereon.` In Figs. 1 and 2,-like parts are indicated by the. same reference characters.
The average carrier variation of the gate voltage appearsacross a screen grid resistor SI whichis bypassed by the usual filter condenser 32. One or more amplifier tubes controlled by the A. V. C. circuit may have their screen grids supplied by the operating voltage through the resistor SI. lIf a plurality of tubes is so supplied, the resistance of resistor 3| ordinarily should be less than the A109,000 ohms indicated on the drawing. v l v The operation of lthe kcircuit of Fig. 2 is similar to that of the circuit previously described. If the incomingsignal fades, the control grid of the I. F'. amplifier tube becomes lessnegative with the-result vthat the screen grid current increases and the gate voltage on the plate of the limiter diode I8 becomes less positive whereby the limiter diode becomes nonconducting at a lower value of signal voltage.
The circuit of Fig. 2 has an advantage over that of Fig. 1 inl that there is a degenerative action in the screen grid circuit whereby the changes in screen grid voltageare nearly linear with respect to changes in average carrier and, therefore, follow the output of the linear detector I4 rather closely.
It will be'y understood that an important feature of the. circuit in Fig. 2, as well as in Fig. l, is that the gate voltage. is caused to follow the useful modulation envelope as well as theV average carrier variations by giving the R-C circuit Iii-24 the proper time constant.
In Fig. 3, there is shown anv embodiment of the invention in which the average carrier variations of the gate voltage are obtained by means of an extra tube, not a signal amplifier tube, which is controlled by the A. V. C. voltage. Also, in Fig. 3, the invention is shown applied to a sound receiver, such as a police receiver, having a narrow band sound channel and the gate Voltage in the example illustrated is not made to follow the modulating envelope. Like parts in Figs. 1 and 3 are indicated by the same reference characters.
AThe receiver may comprise a rst detector and an oscillator indicated at 40 for supplying an I. F. signal to an amplifier 4I connected through a transformer to the second detector I3. The detector I3 comprises a diode I4 having a load resistor 42 shunted by a condenser 43.
The noise limiter connections are substantially the same as in the other gures except that the average carrier variations in the gate voltage are obtained from across a resistor 44 which supplies plate voltage to the above-mentioned extra tube indicated at 46.
The tube 46 has a control electrode connected through a resistor 41 to a point on the A. V. C. circuit whereby the current through the plate resistor 44 will vary with the A. V. C. voltage and thus' vary the gate voltage applied to the limiter diode I8 in accordance with changes in average carrier.
In this embodiment of the invention, it may be desirable to provide a condenser 5I which may be switched across the output resistor I9 for attenuating the higher frequency components of the sound signal for tone controll and/or additional noise reduction., It will be noted that the condenser 5I has substantially greater capacity than the condenser 24 in the circuit of the other figures where the gatevoltage is made to follow the modulation envelope.
From the foregoing, it will be apparent that an important feature of the present invention is the provision of a simplified noise suppressor circuit of the series diode type in which the gate voltage follows both the average carrier and the useful modulation envelope, the circuit also hav- ;,ing the desirable feature of utilizing the full voltage output of the second detector.
I claim as my invention:
l. A radio receiver having a sound channel which includes an amplifier, a detector supplie-d ,from said channel and having a load resistor across which the demodulated signal appears, a noise limiter of the series diode type connected across at least a portion of said load resistor, said limiter comprising a diode and an output resistor in series, an automatic volume control signal components passed by said channel, said channel including an amplifier, a detector supplied from said channel and having a load resistor across which the demodulated signal appears, a noise limiter of the series `diode type connected across substantially the entire portion of said load resistor, said limiter comprising a diode and an output resistor in series, an automatic volume control circuit for said amplier, means controlled by said circuit for applying to said limiter a gate voltage which varies with average carrier, and means for also causing the gate voltage to vary with the useful modulation envelope of the received carrier wave.
3. A radio receiver having an intermediate frequency amplifier with a pass band which is several times the width of the frequency band occupied by the signal components passed by said channel, a detector supplied from lsaid ampliiier and having a `load resistoracross-which the demodulated signal appears, a noise limiter of A the series diode type connected across at least a portion of said load resistor, an automatic volurne control circuit for controlling the gain of said amplifier, said limiter comprising a diode and an output resistor in series, a resistor through which voltage is supplied to an electrode of an amplifier tube in said amplifier, and .means for applying the voltage drop appearing across said last resistor to said limiter as at least a portion of its gate voltage whereby the gate voltage varies with average carrier.
4. The invention according to claim 3 wherein the output resisor of the limiter is shunted by capacity of such value that the gate voltage also follows the useful modulation envelope of the received carrier wave.
5. A radio receiver having a sound channel including an amplifier tube, a. detector connected to be supplied with signal from said channel, said detector having a load resistor across which the demodulated signal appears, a noise limiter. connected across at least a portion of said load resistor, an automatic volume control circuit for. controlling the gain of said amplifier tube, la' resistor through which voltage is applied to screen grid electrode in said amplifier tube, and means for applying the voltage drop appearing across said last resistor to said noise limiter as at least a portion of its gate voltage whereby the gate voltage varies With average carrier. y
6. The invention according to claim 5 wherein said limiter is of the series type which has an output resistor shunted by capacity of such value that the gate voltage also follows the useful modulation envelope of the received carrier wave. l
GUSTAVE L. GRUNDMANN.
US395371A 1941-05-27 1941-05-27 Noise limiter Expired - Lifetime US2300115A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
US395371A US2300115A (en) 1941-05-27 1941-05-27 Noise limiter

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US395371A US2300115A (en) 1941-05-27 1941-05-27 Noise limiter

Publications (1)

Publication Number Publication Date
US2300115A true US2300115A (en) 1942-10-27

Family

ID=23562762

Family Applications (1)

Application Number Title Priority Date Filing Date
US395371A Expired - Lifetime US2300115A (en) 1941-05-27 1941-05-27 Noise limiter

Country Status (1)

Country Link
US (1) US2300115A (en)

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2416614A (en) * 1943-08-12 1947-02-25 Crossley Detonation indicating system
US2518449A (en) * 1945-08-11 1950-08-15 James C Coe Noise limiter
US2606247A (en) * 1947-08-15 1952-08-05 Motorola Inc Automatic gain control
US2611823A (en) * 1945-10-24 1952-09-23 Pye Ltd Arrangement for suppressing impulsive interference in the reception of amplitude modulated signals
US2668234A (en) * 1950-06-07 1954-02-02 Zenith Radio Corp Noise-suppression system for television receivers

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2416614A (en) * 1943-08-12 1947-02-25 Crossley Detonation indicating system
US2518449A (en) * 1945-08-11 1950-08-15 James C Coe Noise limiter
US2611823A (en) * 1945-10-24 1952-09-23 Pye Ltd Arrangement for suppressing impulsive interference in the reception of amplitude modulated signals
US2606247A (en) * 1947-08-15 1952-08-05 Motorola Inc Automatic gain control
US2668234A (en) * 1950-06-07 1954-02-02 Zenith Radio Corp Noise-suppression system for television receivers

Similar Documents

Publication Publication Date Title
US2448908A (en) Television receiver
GB2089610A (en) Receiver for amplitude and angle modulated signals
US2300115A (en) Noise limiter
US2273934A (en) Noise limiting device
US2694142A (en) Signal-to-noise energy detection unit
US2927997A (en) Frequency modulation receiver
US2527617A (en) Radio receiving system
US2606247A (en) Automatic gain control
US2098286A (en) Transmission control in signaling systems
US2144304A (en) Delayed automatic gain control circuit
US2578714A (en) Sound and facsimile multiplex system
US2907831A (en) Single-sideband system for the transmission of speech
US2608648A (en) Highly selective radio receiver
US2345762A (en) Noise limiter circuit
US2303358A (en) Stable seismic wave amplifier with automatic volume control
US2379720A (en) Receiver fidelity control system
US2253338A (en) Modulated-carrier signal receiver
US2200062A (en) Automatic volume control
US2299390A (en) Noise suppressor
US2264724A (en) Receiver for frequency or phase modulated oscillations
US2573248A (en) Television receiver
US3205443A (en) Interfering signal resolving system
US2128996A (en) Automatic volume control circuits
US2034497A (en) Amplification control circuits
US2595441A (en) Angle modulated carrier wave receiver