US2455191A

US2455191A - Radio wave detector system

Info

Publication number: US2455191A
Application number: US564085A
Authority: US
Inventors: Richards Claude Langdon
Original assignee: Mullard Radio Valve Co Ltd
Current assignee: Mullard Radio Valve Co Ltd
Priority date: 1943-07-30
Filing date: 1944-11-18
Publication date: 1948-11-30
Anticipated expiration: 1965-11-30
Also published as: GB570772A

Description

Now. 1948. c, s I 2,455,191

mm WAVE DETECTOR SYSTEM Filed Nov. 18, 1944 Alp H Flo INVENTOR CLA UDELANGDCWRICHARDJ.

6C1. 2 AUDIO OUTPUT ATTORNEY.

Patented Nov. 30,1948

PATENT arise RADKO WAVE DETECTOR SYSTEM Claude Langdon Richards, London, England, as signor to The Mullard Radio Valve Company Limited, London, England Application November 18, 1944, Serial No. 564,085 In Great Britain July 30, 1943 Section 1, Public Law 690, August 8, 1946 Patent expires July 30, 1963 Claims.

e. g. as amplitude modulation or as frequencymodulation of a carrier wave. It is a feature of the invention that the switch means may be incorporated in the L. F. stage or stages of the circuit. It is more especially intended that one of the forms of radiation from which a circuit according to the invention is capable of extracting information shall be a frequency-modulated carrier wave and for this purpose the circuit includes discriminator means, preferably arranged in the manner described in the specification of co-pending patent application currently filed by me for Frequency'Modulated Receivers", Serial No. 564,086, now Patent No. 2,415,656, issued February 11, 1947, according to which the output from a limiter is applied to an inductance (primary) which is coupled with another inductance (secondary), the primary or the secondary or both forming part of a tuned circuit adjusted to the unmodulated carrier frequency, and a connection is provided-between the limiter output circuit and the secondary circuit whereby a carrier frequency component from one circuit is added vectorially to a carrier frequency component from the other circuit, which components are 90 out of phase when the carrier frequency and the tuned circuit (or circuits) are exactly in tune, thephase angle varying on either side of 90 as the carrier frequency is greater or smaller than the turned frequency the resultant of the components being applied to a rectifier circuit comprising a single diode. The invention contemplates the use of a single channel (wholly or in part) for the reception of each of the various transmissions which the circuit is capable of receiving, rather than the use of separate and distinct channel for each form, and in this connection one feature of novelty introduced by the invention comprises the application, for the reception of C. W. radiation, of a modulating voltage to the anode of a valve which functions as part of the frequency discriminating circuit during reception of F. M. radiation. Further, circuits according to the invention may be adapted to provide automatic volume control; and where they are designed to receive, as one form of 2 radiation, a continuous wave transmission, the circuits are arranged so that a heterodyne beatnote can be applied to the detector without interfering with the A. V. C. provided. It will be noted from the description below of forms which the invention may assume that these various" functions are achieved by the use of fewer valves and components than have been necessary in circuits heretofore proposed to provide some of these functions.

In order that the invention maybe more readily understood certain embodiments thereof will now be described with reference to the accompanying drawing in which Fig. 1 is a schematic diagram showing one form of a circuit according to the invention,

Fig. 2 is a schematic diagram showing another form of a circuit according to the invention and Fig. 3 is a schematic diagram illustrating a further embodiment of the invention.

In the circuit embodying the invention shown in Fig. 1 the valve V1 together with the associated elements Lp,Ls,Cs form a limiter-discriminator circuit for reception of F. M. waves, and is substantially identical with the circuit described in the aforementioned specification of co-pending patent application, Serial No. 564,086, now'U. S. Patent 2,415,656, issued February 11, 1947, referred to above. The F. M. waves derived from the preceding stages of the receiver are applied to a primary widing 8 of a L-F transformer I, the-secondary circuit 9 of which has one terminal connected to the grid ID of tube V1 and the other terminal connected to the cathode II and ground through a resistor 16 shunted by capacitor 17 which resistor effects amplitude limitingof the- F. M. wave in the tube V1 in know manner. Connected in the anode circuit of tube Vi is the winding Lp, which winding is magnetically coupled to the circuits Ls, Cs, tuned to the center frequency of the applied wave and is also connected to one end of said circuit through capacitor Hi. As pointed out in the above-referred to copending application, by interconnecting and magnetically coupling the winding Lp, Ls, a resulting voltage is obtained comprising two components which are in quadrature with respect to each other when the applied wave has an instantaneous frequency equal to the resonant of the tuned circuit. At frequencies of the applied wave deviating from the center frequency, variations'of the relative'phase relationship of the two components are produced, thereby correspondingly varying the amplitude of the resultant. The resultant signal is applied to the A three-way switch 8 has one contact F. M.

connectedto the output of the diode rectiiier oi the tube V1 and the switch is thrown to this contact when frequency-modulated radiation is being received, the impulses being fed through a suitable filter circuit l8, it as shown to the audio output stage of the receiver.

When the circuit is to be used for reception of amplitude modulated signals the switch S,is thrown to another contact thereof AM connected to the gird iii of the pentode in the tube V1. This grid is used as a diode from which A. V. C. and modulated signals are fed through suitable filter elements 20, 2!, 22, and 23, as shown, respectively to preceding and subsequent stages of the receiver. When the valve is working in this manner the diode, and the other pentode elements in the tube V1 are inoperative.

For C. W. reception the switch 8 is thrown to the third contact thereof 0. W. and a heterodyne signal obtained from a Hartley or other oscillator formed by the tube V: and the 'tuned circuit 24 is fed by direct coupling as shown. to the anode i2 oi the tube V1 as a modulating voltage. This heterodyne beatnote is rectified in the diode section li-ii of the tube V1 and supplied through the selector switch to the later stages of the receiver. The oscillator tube V:

. .is not in use except for C. W; reception and a switch H (which may be part of, or ganged to, the switch S) controls the supply of power thereto. As will be seen no heater current flows to the valve V2 except when the circuit is used for C. W. reception.

The form of the invention shown in Fig. 2 is substantially identical with that shown in Fig. 1 save that for C. W. operation it is preferred to supply the local oscillator voltage to the diode section I 3-i i of the discriminator tube V1 through a suitable resistance R and a capacitor 21 rather than by direct coupling to the limiter anode as in Fig. 1. For satisfactory operation oi' the discriminator in F. M. reception the tuned circuits L5, Cs must be very heavily damped and the resistance R assists in providing such damping.

A third form of the invention is shown in Fig. 3 Here, for C. W.- operation, the local oscillator voltage developed across a load resistor 3i connected to-anode 26 of tube V: is supplied through the intermediary of a resistor 28 and a capacitor 30 to the control grid of V1 together with the incoming signal. The value oi the voltage from the local oscillator V2 is adjusted (for use during C. W. reception) to be equal to the carrier voltage at which 100% modulation just gives maximum power output. Interference with the A. V. C. operation is prevented by the resistances R1, R2 associated with the positive limiting diode D2. Manual control of the volume maybe effected by means of the variable resistance Ra, operation of which controls both the resultant L. F. signal from the diode D1 and the bias voltage from the oscillator Vi by way ot the diode D3 thereof. The latter voltage is employed as indicated at G. C. 2 to control in part the gain of the circuit, while as indicated at G. C. I the remainder of the gain is controlled automatically aspreviously described. It will be noted that various switch arms and associated contacts are provided to include or exclude various parts of the circuit according to the form of modulated radiation being received, and all may be ganged .-to or term part of the switch 8 operating as described above. The operation of the various switch arms is self-apparent from the drawings and is therefore not described in detail.

I claim:

1. A detector system for a carrier wave havinga predetermined central frequency, comprising a discharge tube having a cathode, an anode and a control grid interposed between the cathode and the anode, an input circuit for the carrier wave connected between the control grid and the cathode, a resistance element and a condenser element connected in shunt with each other and in series with the control grid and the cathode for producing grid circuit limiting of the carrier wave and for generating a potential proportional to the amplitude of the carrier wave, a transformer having a primary winding in the output circuit of said anode and a secondary winding, said secondary winding being tuned to substantially the said predetermined frequency and being magnetically coupled to said primary winding to produce a terminal voltage in quadrature with the voltage of the primary winding, means to interconnect one end of each of said windings to thereby combine the voltage of the primary winding and said terminal voltage to produce a resultant voltage, means for rectii'ying said resultant voltage to produce a potential proportional to the amplitude of said resultant voltage, a heterodyne oscillator coupled to said discharge tube, means to energize said discharge tube and said heterodyne oscillator, an output circuit, and means to selectively connect the output circuit to said means for generating a potential proportional to the amplitude of the carrier wave and saidmeans to generate a potential proportional to the amplitude of said resultant voltage and to selectively energize said heterodyne oscillator.

2. A detector system for a carrier wave having a predetermined central frequency, comprising a discharge tube having a cathode, an anode and a control grid interposed between the cathode and the anode, an input circuit for the carrier wave connected between the control grid and the cathode. a resistance element and a condenser element connected in shunt with each other and in series with the control grid and the cathode for producing grid circuit limiting of the carrier wave and for generating a potential proportional to the amplitude of the carrier wave, a transformer having a primary winding in the output circuit of said anode and a secondary winding, said secondary Winding being tuned to substantially the said predetermined frequency and being magnetically coupled to said primary winding to produce a terminal voltage in quadrature with the voltage of the primary winding, means to interconnect one end of each of said windings to thereby combine the voltage of the primary winding and said terminal voltage to produce a resultant voltage, means for rectifying said resultant voltage to produce a potential proportional to the amplitude 01' said resultant voltage, a heterodyne oscillator coupled to the anode of said discharge tube. means to energize said discharge tube and said heterodyne oscillator, an output circuit, and means to selectively connect the output circult to said means for generating a potential proportional to the amplitude of the carrier wave and said means to generate a potential propor tional to the amplitude of said resultant voltage and to selectively energize said heterodyne oscillator.

3. A detector system for a carrier wave having a predetermined central frequency, comprising a discharge tube having a cathode, an anode and a control grid interposed between the cathode and the anode, an input circuit for the carrier wave connected between the control grid and the cathode, a resistance element and a condenser element connected in shunt with each other and in series with the control grid and the cathode for producing grid circuit limiting of the carrier wave and for generating a potential proportional to the amplitude of the carrier wave, a transformer having a primary winding in the output circuit 01' said anode and a secondary winding, said secondary winding being tuned to substantially the said predetermined frequency and being magnetically coupled to said primary winding to produce a terminal voltage in quadrature with the voltage of the primary winding, means to interconnect one end of each of said windings to thereby combine the voltage of the primary winding and the said terminal voltage to produce a resultant voltage, means for rectifying said resultant voltage to produce a potential proportional to the amplitude of said resultant voltage, a heterodyne oscillator coupled to the control grid of said discharge tube, means to energize said discharge tube and said heterodyne oscillator, an output circuit, and means to selectively connect the output circuit to said means for generating a potential proportional to the amplitude of the carrier portional to the amplitude of said resultant voltage and to selectively energize said heterodyne oscillator.

4. A detector system for a carrier wave having a predetermined central frequency, comprising a discharge tube having a cathode, an anode, a control grid interposed between the cathode and the anode and a diode anode, an input circuit for the carrier wave connected between the control grid and the cathode, a resistance element and a condenser element connected in shunt with each other and in series with the control grid and the cathode for producing grid circuit limiting of the carrier wave and for generating a potential proportional to the amplitude of the carrier wave, a transformer having a primary winding in the output circuit oi said anode and a secondary winding, said secondary winding being tuned to substantially the said predetermined frequency and being magnetically coupled to said primary winding to produce a terminal voltage in quadrature with the voltage of the primary winding, means to interconnect one end of each of said windings to thereby combine the voltage of the primary winding and said terminal voltage to produce a resultant voltage, means to connect the 6 other end of the secondary winding to said diode anode, a load resistance element interconnecting the diode anode and the cathode for producing a potential proportional to the amplitude of said.

ant voltage and to selectively energize said het- I erodyne oscillator.

5. A detector system for a carrier wave having a predetermined central frequency, comprising a discharge tube having a cathode, an anode, and a control grid interposed between the cathode and the anode, an input circuit for said carrier wave connected between the control grid and the cathode, a parallel circ'uit arrangement comprising a resistance element and a capacitive reactance element connected in series with the control grid and cathode of said discharge tube to generate a potential proportional to the amplitude of said carrier wave, a transformer having a primary winding connected in the output circuit of said anode and a secondary winding, one of said windings being substantially tuned to said central frequency and said secondary winding being magnetically coupled to said primary winding to produce a terminal voltage in quadrature with the voltage across said primary winding, means to interconnect one end of each of said windings to combine the voltage of said primary winding and said terminal voltage to produce a resultant voltage, means for rectifying said resultant voltage to generate a potential proportional to the frequency deviations of said carrier wave from said central frequency value, an output circuit, and means selectively to connect said output circuit to said means for generating a potential proportional to the amplitude of the carrier wave and said means to generate a potential proportional to frequency deviations of said carrier wave.

CLAUDE LANGDON RICHARDS.

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

UNITED STATES PATENTS Number Name Date 2, 125,953 Prochnow Aug. 9, 1938 2, 250, 862 Farrington July'29, 1941 2, 356, 224 Crosby Aug. 22, 1944 2, 415, 656 Richards Feb. 11, 1947