US2491276A - Radio transmission control - Google Patents

Description

Dec. 13;, 1949 D. MITCHELL 2,491,276

I RADIO TRANSMISSION CONTROL Filed April 20, 1948 2 sheets-sheet 1 2 ALT/METER ALT/METER RECEIVER TRANSMITTER RADIO TRANSMITTER RECEIVER INVEN TOR Q Ml TCHELL qua-O M ATTORNEY Dec. 13, 1949 D, MITCHELL 2,491,276

RADIO TRANSMISSION CONTROL Filed April 20, 1948 2 Sheets-Sheet 2 lNl/EN TOR 0. M/TCHELL JQLUWT ATTORNEY Patented Dec. 13, 1949 RADIO TRANSMISSION CONTROL Doren Mitchell, Martinsville, N. 3., asslgnor to Bell Telephone Laboratories, Incorporated, New York, N. Y., a corporation of New York Application April 20, 1948, Serial No. 22,229

9 Claims. (Cl. 25017) This invention relates to radio systems and in particular to systems and methods of controlling the propagation and reception ranges of radio waves.

It is an object of this invention to obtain in an aircraft radio system a constant transmittingrange.

It is another object of this invention to obtain in a radio system a constant transmitting range irrespective of the height of said system.

It is a further object of this invention to obtain in an aircraft radio system, comprising a transmitterconneoted to an antenna, a constant transmission range without varying the power output'of said transmitter.

It'is' a still further object of this invention to control the range of a mobile radio transmitter -receiver system in accordance with the altitude of said system.

It is an additional object of this invention to-control the energy radiated by an antenna in accordance with the height of said antenna.

Dth'er objects and uses of the invention will be apparent from a study of the specification and drawings.

lit is known that the propagation and reception ranges of radio systems may be determined by varying the power output of these systems. Control systems have been developed to regulate transmission and reception ranges and while these systems are usually efiicient in operation they also have inherent limitations. When, for example, mobile radio systems are used in airplanes it may be desirable to limit the transmission and reception of the radio system to a twent'y-mile range in order to minimize interference. If a one hundred watt transmitter operating at one hundred and fifty megacyoles is used in an. airplane the transmitter will have an effective range of about twenty miles when the airplane containing the transmitter is situated on the ground. However, as the airplane rises from the ground the transmitter range increases fairly rapidly to a range of. about two hundred miles, at: an altitude of twenty thousand feet, and this expandedrange may be an undesirable feature. In the future, due to the rapid development of the mobile radio art and the resultant extensive use of mobile radio systems by increasing numbers of people, the extension of the transmission and recaption ranges of a radio system may result in unwanted crosstalk and other interferences. The invention maintains a substantially constant range in a radio system by eiiectively limiting the radio system transmission-reception distances in accordance with the altitudes of the radio system radiating and receiving members.

In the preferred embodiment of the invention the control of a radio system transmission and/ or reception range is varied automatically in accordance with the height of the system transmittingreceiving members in relation to the earth. In the invention an automatic coupling system may vary the radiated power output of a radio trans-- mitter, or the power input of a radio receiver, in response to variations in the altitude of the transmitting or receiving antennae. In an alternative embodiment of the invention the automatic coupling system responds to variations in the pressures of the atmosphere.

Referring to the drawings:

Fig. l is a schematic drawing of an embodi ment of the invention and shows equipment for automatically controlling the ranges of a transmitter-receiver radio system in accordance with variations in altitude;

Fig. 2 is a schematic drawing of an alternative embodiment of the system shown in Fig. 1, and shows equipment for automatically controlling the ranges of a' transmitter-receiver radio system in accordance with variations pressures; and

Fig. 3 is a schematic drawing and shows the control system of Fig. 1 and/or Fig. 2 utilized in an airplane.

Referring to Fig. l which is a schematic drawing of an embodiment of the invention, a shaft l0, adapted for rotative movement in clockwise or counter cl'ockwise directions, may be actuated through. connecting gears H and I2 by a drive shaft it which may be motivated by a reversible motor It. The shaft it has an antenna connection 15 from an antenna it, an antenna pick-up loop 11, a ground connection is, and an absorption loop l8 withwhich is connected. a dissipation resistance 26 The equipment units 55, ii, l8, l9 and 2d are electrically divided as illustrated by insulated segments 23, 22, 23, and 2 3 of the shaft i6. Positioned for inductive coupling to the pickin atmospheric up loop IT, or to the absorption loop !9, is a loop 25 which is connected to a radio transmitter-receiver 26. Secured to an end of the shaft til is a position indicatin pointer 2i. The pointer 21 turns withv the shaft Ill and. moves over a chart 28, which may be calibrated in angles of degrees.

so that the position of the pointer 2? in relation. to the chart 28' may inform an observer at any instant of the angular position of the shaft H).

The reversiblev motor is may be energized from an electromotive source 29 through operatedcon- 3 tacts of a relay 3!], or may be energized to rotate in an opposite direction through the operated contacts of a relay 3|. The motor it may be so connected that operation of the relay 38 actuates the motor M in a counter-clockwise direction and the motor M acting upon the shaft it, through the gears i l and I2, turns the shaft H3 in a clockwise direction, while operation of the relay 3i may cause the motor M to turn the shaft iii in a counter-clockwise direction. The operation circuits of the relays and 3| are controlled from electromotive sources 32 and 33 through potentiometers 34 and 35, and through potentiometer slider arms 36 and 31. The voltage potential across the electromotive source 32 is preferably equal to the voltage potential across the electromotive source 33, and the resistances of. the potentiometers 34 and should also be of equal value.

The potentiometer slider arm 37 is mechanically connected to the shaft I I] and movement of the shaft it! moves the potentiometer slider arm 3! in a corresponding direction. The potentiometer slider arm 36 is connected to an indication needle 38 of an electronic altimeter system 39. Movement of the indicator 38 upon an altimeter indicating dial 40 results in a movement of the potentiometer slider arm 36 in a corresponding direction. The electronic altimeter system 39 may be of a type known in the art such as that system disclosed in Patent 2,247,662 issued July 1, 1941 to R. C. Newhouse.

The system embodiment in accordance with the invention operates as follows. Suppose that the system is installed as a part of a mobile radio system in an airplane. When the airplane is situated on the ground the antenna pick-up loop ll will be positioned for optimum inductive coupling to the radio transmitter-receiver loop 25. When the pick-up loop I! is so situated, the potential between a point 4H and the tip of the potentiometer slider arm 36 will equal the potential between the point 4! and the tip of the potentiometer slider arm 31. Since these potentials oppose each other there is no potential difference between the tips of the slider arms 36 and 31, and no current will flow from these tips through the relay energizing circuits. When the airplane rises into the air and has attained a certain altitude the electronic altimeter needle 33 will have moved to a new position 38' in relation to the altimeter indicator dial Ml, and will have moved the potentiometer slider arm 3% to a new position 36'. When the slider arm 36 occupies the new position 36' the potential between the point 4! and the tip of the slider arm 3% in position 36 will be less than the potential between the point 4| and the tip of the slider arm 31, and current will flow to the tip of the slider arm 36 and thence through a circuit, including a unidirectional conducting valve 4 2, to energize and operate the relay 3!. Operation of the relay 3| energizes the motor It so that the shaft it turns in a counter-clockwise direction as discussed. The counter-clockwise movement of the shaft l0 swings the antenna pick-up loop H away from the transmitter-received loop 25, so as to reduce the coupling between the loop I! and the loop 25, and at the same time swings the absorption loop I 9 into a more favorable coupling position so as to increase the coupling between the loop i9 and the transmitter-receiver loop 25. This action diverts a portion of the energy from the radio transmitter-receiver 23 into the absorption loop 19 and prevents some of this energy portion from reaching the antenna l6, for some of the energy diverted into the absorption loop [9 is dissipated in the resistance 23. The use of the absorption loop provides range control of the mobile radio system, equalizes the load on the transmitter and facilitates the tuning of the transmitter.

As the shaft It] turns in a counter-clockwise direction the slider arm 3'! turns with the shaft it until it reaches a new position 31. When the slider arm 3! has reached the position 3'! the voltage potential between the point 4! and the tip of slider arm 36 in position 36 will equal the voltage potential between the point M and the tip of the slider arm 3'! in position 31. Since these potentials opposed each other there is no potential difference between the tips of the slider arms 36 and 31 in positions 36' and 31', and no current will flow to the relay energizing circuit and the relay 3| will restore to a normal nonoperated condition and stop the movement of the motor M. When the motor i4 stops, the turning movement of the shaft Ill ceases and the shaft it] comes to rest with the loops I1 and I9 retaining their new positions in relationship to the transmitter-receiver loop 25.

When the airplane loses altitude the altimeter needle 38 will move back from the position 38 towards the zero position on the altimeter dial 4%] until it reaches a position at which it will indicate the new altitude of the airplane in relationship to the earth. The backward movement of the needle 38 will move the slider arm 33 back from the position 36' towards the position originally occupied by the slider arm 36 before altitude was attained. When the slider arm 36 occupies the new position the potential from the point M to the tip of the slider arm 31, in position 37', will be less than the potential between the point 4| and the tip of the slider arm 38, and current will flow to energize and operate the relay 30 through a circuit including the slider arm 3'! in position 31, the relay 3D, and a unidirectional conducting valve 43. Operation of the relay 3!! actuates the motor it and causes the shaft m to turn in a clockwise direction as discussed. The shaft l [i when turning in a clockwise direction moves the absorption loop away from the transmitter-receiver loop 25, and moves the antenna loop I! into a better coupling position in relationship to the transmitter-receiver loop 25. The turning movement of the shaft Ill also moves the slider arm 31 back from the position 31', towards the original position it occupied before the airplane attained altitudes, until the.

slider arm 31 reaches a point on the potentiometer 35 whereat the potential from the point 4! to the tip of the slider arm 36 is equal to the potential from the point 4! to the tip of the slider arm 31. When the condition of equal potentials is attained no current flows to the relay energizing circuits, the relay 3!! will then restore to a normal non-operated position and the turning movement of the shaft ill will cease.

It will be readily understood that while the system as shown utilizes one antenna for both transmission and reception purposes a plurality of antennae may be utilized. The automatic control features in accordance with the invention may also be utilized by the transmitter mechanism alone, while the receiver mechanism may operate normally and use a separate antenna without the automatic control feature.

Referring to Fig. 2, there is shown an alternate embodiment of the invention for automatically controlling the range of a radio system in accordance with variations in atmospheric pressures. Here is shown a disk 45 with a pin 46 attached to the disk. The disk 45 is adapted for connection to the coupling mechanism of Fig. 1 along the section marked XX. The pin 46 is connected by a crank 4'! to a bellows mechanism 48 which is preferably sealed at sea level atmospheric pressure. This equipment is adaptable for use in an airplane for controlling the coupling between the pick-up loop H, the absorption loop l9 and the transmitter-receiver loop 25 of Fig. 1.

This system operates as follows. When the airplane is situated upon the ground the bellows 48 being subjected to ground level atmospheric pressure is in a normally contracted condition. When the airplane leaves the ground and gains altitude the atmospheric pressure decreases and the bellows mechanism expands and occupies a new position 48'. Expansion of the bellows actin through the crank 41 upon the pin 46 pushes the pin 46 to a new position 46', and turns the shaft in a counter-clockwise direction moving the pick-up loop I! away from the transmitterreceiver loop 25, in a manner discussed in relation to Fig. 1. As the airplane loses altitude the bellows is compressed and contracts due to increased atmospheric pressure, and the pin 46 moves from the position 46' back towards the original osition it occupied when the airplane was situated on the ground, and moves the absorption loop 19 away from the transmitter-receiver loop 25, in a manner discussed in relation to Fig. 1.

Referring to Fig. 3 which is a schematic drawing showing the automatic range control systems of Figs. 1 and 2 utilized in an airplane, Fig. 3 shows antennae 5| and 52 of an electronic altimeter system corresponding to the antennas of the altimeter 39 of Fig. 1, and antenna 53 of a transmitter-receiver system corresponding to antenna I6 together with a bellows mechanism 54.

It is to be understood that the above-described embodiments are illustrative examples and that various modifications may be made without departing from the spirit of this invention.

What is claimed is:

1. In a mobile radio system, the combination of a transmitter, a radiating member, a dissipation member, separate adjustable rotatable elements for coupling said members to said transmitter, and means responsive to changes in atmospheric pressure for simultaneously rotating said elements in a clockwise or counter-clockwise direction dependent upon the sense of the change in said pressure, whereby the couplings of said members to said transmitter are varied in opposite senses upon any change in said pressure and the sense of the variation for each coupling is reversed upon a reversal in the sense of the change in said pressure.

2. The combination of claim 1 in which the responsive means is responsive to changes in the altitude of said radiating member.

3. In a mobile radio system the combination of, a transmitter-receiver, a radiating member, a dissipation member, movable coupling loops for coupling said members to said transmitter-receiver, and means responsive to changes in at-- mospheric pressure due to changes in altitude for varyin the positions occupied by said loops in their relationships to said transmitter-receiver.

4. In a radio system the combination of a transmitter, a radiating member, a dissipation member, an adjustable coupling element included between said transmitter and said members and means responsive to changes in the altitude of said system for controllin the adjustment of said element.

5. In a mobile microwave radio system comprisin a transmitter, a radiating member, a dissipative member, and separate adjustable elements coupling said members to said transmitter, the method comprising decreasing the coupling of said radiating member and simultaneously increasing the coupling of the dissipative member upon an increase in the altitude of said system, and increasing the coupling of said radiating member and simultaneously decreasing the coupling of said dissipative member upon a decrease in said altitude.

6. In a system for rendering the effective range of a radio system independent of the height of said system, the method comprising changing the amounts of energy emitted and received by said system inversely in accordance with changes in the height of said system.

7. In a system for maintaining constant the range of a mobile radio system irrespective of variations in the altitude of said radio system and without changing the power output of said radio system, the method comprising, radiating the entire output of said radio system when said radio system is situated at a minimum altitude, radiating a portion of said output and dissipating the remaining output portion when said radio system is situated at a different altitude, and progressively decreasing the ratio of said radiated portion to said dissipated portion as the altitude increases.

8. In a system for maintaining constant the range of a mobile radio system irrespective of changes in the altitude of said radio system and in the atmospheric pressures surrounding said system, and without changing the power of said radio system, the method comprising efliciently utilizing the power of said radio system when said radio is situated at a minimum altitude, efficiently utilizing a portion of said power and dissipating the remaining portion when said radio attains a different altitude, and progressively decreasing the ratio of said eiliciently utilized power portion to said dissipated power portion as the altitude increases, while increasing said ratio as the altitude decreases.

9. The method of radio communication from an airborne vessel which comprises continuously measuring the height of the vessel above the earths surface and continuously controlling the intensity of the radio frequency energy transmitted from the vessel for communication under control of the height indication to cause that energy to vary inversely with the height.

DOREN MITCHELL.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,008,832 Leonard, Jr July 23, 1935 2,190,037 Neufeld "Feb. 13, 1940 2,378,604 Wallace ..June 19, 1945 2,403,603 Korn July 9, 1946 FOREIGN PATENTS Number Country Date 372,819 Great Britain May 12, 1982

Images