US2074478A

US2074478A - Short wave detector

Info

Publication number: US2074478A
Application number: US56940A
Authority: US
Inventors: Ernest G Linder
Original assignee: RCA Corp
Current assignee: RCA Corp
Priority date: 1935-12-31
Filing date: 1935-12-31
Publication date: 1937-03-23
Anticipated expiration: 1954-03-23
Also published as: GB470805A; NL47929C; DE708035C

Description

March 23, 1937. E. G. LlNDER SHORT WAVE DETECTOR Filed Dec. 31, 1955 7 NM, pawl! Ihv {\m J fi M x H, 5 s; v J

. .eN 1 Q o ituated Mar- .1937

PATENT OFFICE 2.014.473 snon'r wave nnrso'roa Ernest o. Linder, Philadelphia, Pa.,' assignor to Radio Corporation of America, a corporation of Delaware Application December 31, 1935, Serial No. 56,940 10 Claims. (01. 250-27) The present invention relates tomeans for detecting ultrashort radio waves and has for its primary object to provide an improved means for that purpose.

' It is a further object of the present invention to provide an ultrashort wave detector embodying electric'discharge apparatus having means for producing a stream of electrons and means for causing a deflection of the electron stream in response to acceleration and deceleration by means under control of an improved ultrahigh frequency modulated carrier wave.

Uitrahigh. frequency detector systems have been proposed heretofore embodying an electron l5 stream, but such systems have further included means for deflecting the electron stream or varying the rate of flow of thestream. as in the usual radio tube having a control grid and each of such systems had certain limitations. In accordance with the present invention, howeventhe speed of electron fiow in an elongated electronic path is varied through a deflecting electromagnetic or electrostatic field of fixed area, intensity and position, and under control of a received carrler wave. With this arrangement, an electron beam may be caused to be deflected as a result of a variation in speed of flow. The beam is simultaneously deflected with the acceleration and deceleration of the electrons.

The invention will, however, be better understood from the following description when considered in connection with the accompanying drawing and its scope will be pointed out in the appended claims. g

: In the drawing, Figure 1 is a schematic circuit diagram of ultrashort wave or high frequency detector means embodying the invention, and

Figs. 2 and 3 are similar schematic diagrams of modifications of the invention as shown in Fig. 1.

Referring to Fig. 1, 5 indicates the evacuated envelope of a cathode ray device having an electron gun as a source of electrons 8, at one end of the envelope, and a plurality of closely spaced targets or anodes I, 8 and 9 at the opposite end of the envelope toward which an electronic stream or beam, indicated by the dotted line Iii, is projected from the source 8. Between the source 8 and the anodes and more adJacent to the latter the electron beam. is subjected to a relatively strong electricalfield such as an electrostatic field provided by two electrostatic deflecting plates II to which are connected terminal leads i2 for the application of deflecting potentials. The strength of the field is adjusted in such a manner that electronic stream hassuflicient velocity to follow the dotted path l0 and a continuation thereof indicated at iii to normally strike a central target 8. In systems herefore known, signal strength variation has been utilized to cause a variation'in 5 the potentials of the deflecting plates or of similar electrodes spaced along the electronic stream to cause a deflection thereof to actuate an amplifier as an output device. In the present example, an

electric discharge amplifier stage is provided in 10 connection with the detector, and includes an electric discharge tube H having a cathode ii, a control grid i6 and an output anode i'l, the

- latter being coupled to a suitable audio frequency output circuit i8 through a coupling transformer 15 IS in the anode output circuit 20.

The amplifier control grid iii is arranged for self bias operation and is connected'through an input circuit with a grid resistor 2 i through which bias potentials are supplied to the grid. The 20 cathode end of the bias resistor 2| is connected to the central anode 8 while the grid end of the resistor 2| is connected as indicated with the adiacent anode electrodes I and 9.

With a constant electrostatic field supplied by 5" the electrodes II, a variation in the velocity in the electron beam, for example, a reduction in velocity. causes the beam to be deflected simultaneously to a greater or lesser degree under the influence of the electrostatic field, as indicated 30 by the dotted paths 22, the direction of deflection depending upon the polarization. of the plates and in any case will be in but one direction. Ifv modulation is present, the same is transferred to the grid impedance 2| and is amplified in the de- 5 vice II, as is well understood.

In order that the velocity of the electron beam may vary in response to a received signal wave, a transmission line is provided adjacent to and extending along the electron beam, as indicated 40 by the conductors 23 and 24-, each of which is connected with a short wave antenna at the end more adjacent to the cathode or electronic gun 8. In the present example. the antenna includes a divided half wave wire 25-26 extending through 45 the envelope of the device for collecting radiated energy.

Radiation received by the antenna causes standing waves to be formed on the transmission line, along which are spaced a plurality of pairs 50 r of grids 21, one grid of each pair being connected with one of the

leads

23 and 24 forming the transmission line. The grids in any pair are arranged closely together, at a distance which is relatively short in comparison with the wave -55 length of the carrier wave to be received, and

preferably less than one tenth of the length of said carrier wave. Furthermore, the spacing of the pairs of grids along the transmission is preferably some multiple of a half wave, as the de tector system shown is most eifectivefor the re-, ception of micro waves, such as those below ten centimeters in length or above 3,000 megacycles in frequency.

The grids are arranged preferably in the form of loops or circular coaxial rings, as shown, through the center of which the electronic stream is projected. The characteristics of the line, such as the inductance of the leads 23 and 2 3, are so adjusted, that the average electron speed may equal or closely approximate-the speed of propagation of the received wave along the transmission line. The electrostatic field is adjusted to a fixed value so that in the absence of a signal or carrier wave the electron beam strikes the central anode. With the beam directed along the axis of the transmission line and through the grids, as shown, in the presence of asignal or carrier wave, the electrons. are accelerated or decelerated successively at each pair of grids, if the electron velocity approximates that of the wave propagation. The net acceleration is translated into transverse spread of the beam as the beam passes through the-transversely acting fixed electrical field;

The beam is collected on the set of three'adja- -cent anodes which are closely spaced, the two outer anodes being connected together. In the present example, when a signal is received, the

' beam spreads as shown in response to deceleration and more current is received by one or the other of the electrodes, depending upon the polarity of the plates Ii, and if carrying modulation, the same is amplified and transferred to the output circuit i8.

It is necessary to bend or deflect the electronic stream or beam in the transverse deflecting field and to provide a strong field in order that a low percentage variation in speed of the beam may be efiective to cause the electrodes. This permits the sensitivity of the detector to be made relatively'high and is desirable for the reason that the speed variation is in any case a. relatively small percentage of the average speed of the stream. For the foregomg reasons, the present device may be considered as a variable'velocity detector.

It is desirable to reduce the speed of propagation of the wave along the transmissign line and, in Fig. 2, a system modified to provide the above feature is shown. In this figure, the same reference numerals are used to refer to the same parts as provided in the circuit of Fig. 1.

Referring to Fig. 2, a curved envelope 3!] is provided so that the electron beam it from the electron gun 6 is caused to strike the central anode 8 by reason of deflection through a transversely acting magnetic field indicated by the cross hatched area 8 i. The strength or the field is such that the beam assumes the curved initial path 32 normallyto strike the electrode 8, as shown. As signals are received on the antenna 25-46 and transmitted along the transmission line and the grids 21, acceleration of the stream will cause the speed to increase and the electron beam to shift to the outer anode 7 along a path generally indicated at 33, while a decrease in the acceleration and speed of the electrodes will cause the streamt'o shift to the inner electrode 8 along a beam to sweep across the path generally indicated at 34, the curvature taking place only in the magnetic field.

In order to cause the wave propagation to be reduced in speed, thereby to avoid excessive electron speeds, a few inductive turns 35 may be introduced into the transmission line between the pairs of grids, as indicated.

By means of the spaced pairs of grids connected with and positioned along a transmission line adapted for sustaining standing waves, the electrons are accelerated and decelerated in response to carrier waves to cause operation of the detector, as distinguished from systems hereto- -fore known wherein the electron beam is deflected in response to signals applied to plates arranged along the path of the beam, and acting at right angles thereto; Further, as shown in Fig. 2, in order that slight variations in speed may cause a wide deflection of the beam at the target end of the cathode ray device, the beam is preferably initially deflected through a. fixed field, such as a magnetic field acting transversely with respect to the beam.

As in the previous embodiment of the invention, the anodes are connected with a suitableaudio frequency amplifier 36.

Referring now to Fig. 3, in which the same reference numerals are used for like circuit elements and parts, as in Fig. 2, it will be seen that the electron discharge or cathode ray device is further curved and is arranged to provide sub-' tion shown. 'The operation is the same as de-,

scribed in connection with the preceding figures.

As shown in Fig. 3, the electronic beam is de fiected through an arc of a circle by a relatively large area magni 'xic field whereby the length of the beam acted on by the field is greater and the control of the speed of the electrons is more From the foregoing description, it will. be seen that it is desirable to increase the length of the electronic path or the length of the beam and the transmission line, as well as the area of the transversely acting electromagnetic or electrostatic field and to cause the beam initially to be deflected so that the acceleration and deceleration of the electrons may simultaneously cause a deflection of the beam. It will be seen that the sensitivity 01 the detector may be increased by increasing the strength of the field and by providing the series of grids spaced along the beam in conjunction with the initial deflection. No complicated means is required for conveying or translating signalvariations into variable electrical potentials" or fields for deflecting the beam, as has heretofore been necessary.

The detector, as shown and described, may be considered as a variable velocity detector in which an electronic beam is deflected by accelerating and decelerating the tion and acceleration and deceleration being simultaneous. f,

I claim as my invention:

electrons, the defiec- I and means responsive to a received carrier wave for changing the axial speed of flow of said electrons and the transverse deflection of the beam, whereby diflering anode eiectrodesare traversed ,by said beam.

2. Ultras ort wave radio detector l comprisirig,

in combination, means for producingian-electron beam, a plurality of anode electrodes'ytor receiv-' ing said electron beam and deflections thereof, and means responsive to a received carrier wave for changing the speed of flow I and the deflection oi the beam, whereby diflering anode electrodes are traversed by said beam, said last named means including a plurality of coaxial grid electrodes arranged in pairs along said 0 beam, whereby said beam passes through successive pairs of grids, a carrier-wave transmission line extending along said beam to which said grids are connected and a constant electrical field acting transverselywith respect to said beam over a portion 0! the length of said beamsuflicient initially to deflect it and to provide a fixed field through which the beam is iurther'deflected simultaneously with acceleration and deceleration of the electrons in said beam.

3. Ultrashort wave radio detector comprising, in combination, means for producing an electron beam, a plurality of anode electrodes for receiving said electron beam and deflections thereof, a modulation system amplifier connected with said electrodes, means iondeflecting saidbeam in response to variations in speed of electron flow therein, and means providing a transmission line extending along said beam, energy collecting means connected with said line. and a pinrality of grid electrodes arranged in pairs along said beam and connected alternately to opposite sides of said transmission line, said pairs being spaced apart along the electronic beam and transmission line at distances which area muitiple of ahalf wave, and said grids in any pair being arranged relatively closely together.

4. In an ultrashort wave receiving system, a variable velocity electronic beam detector comprising means Ior generating an'electron beam,

a plurality of receiving anodes for said beam, means for producing an electrical'field acting transversely to said beam and of a strength to cause said beam initially to be deflected, and means responsive to a received carrier wave for changing the'speed of flow of the electrons in the beam, and means responsive to the further deflection oi the beam resulting from said change of speed for establishing a signal indication.

5.-In an ultrashort wave receiving systems.

variable velocity electronic beam detector come. prising means for generating an electron beam, a plurality of means for producing an electrical field acting transversely to said beam and of a strength to 05 cause saidbeam initially to be deflected, and

. means tor iurther causing a variation in the defiection of said beam in response to 'a received carrier wave, a transmission line extending along 0! said electrons a, plurality of receivinganodes for said beam..

said beam between the electron source and the deflecting iield, a plurality of circular grid electrodes arranged coaxially in pairs along said beam and being connected in pairs to said line, one to each side of the line in each pair.

6. In an ultrashort wave receiving system, a variable velo'cityelectronic beam detector com.- prising means for generating an electron beam, a

for producing an electrical field acting transversely to said beam and of a strength to cause said beam initially to be deflected, and means for further causing a variation in the deflection of said beam in response to a received carrier wave, a transmission line extending along saidbeam between field, a' plurality of circular grid electrodes arthe electron source and the deflecting plurality of receiving anodes for said beam, means ranged coaxially in pairs along said beam and 'being connected in pairs to said line, one to each side of the line in eachpair, and means in said transmission line for adjusting the velocity of wave propagation along said line in accordance with the electron speed in said beam.

7. An ultrashort wave receiving system inaccordance with claim 4, further characterized by the fact that the electron beam is deflected initialiy through a semicircle, substantially whereby the beam and transmission line is extended without appreciably increasing the space required for said device.

8. An ultrashort wave receiving system in accordance with claim 4, further characterized by the fact that the electron beam is deflected ini-.

tially through a semicircle, substantially 180, whereby the beam and transmission line is extended without appreciably increasing the space required for said device, and that the electrical fleld acts on the beam constantly and uniformly over an area including substantially a semicircle.

.9. An ultrashort wave radio detector comprising, in combination, an electronic gun for producing an electron beam, anode electrodes for-collecting said beam, an electrical field acting transversely to said beam for providing ,an. initial deflection thereofl'and means for accelerating and decelerating the electrons in said beam in response to signals, thereby to cause said beam simultaneously to further be named means including a wave transmission line extending along the beam and a plurality of circular grid elements surrounding said beam in series and connected with the transmission line having a'characteristic such that the wave propagationtherealong has substantially the same speed as the electronic flow in the beam.

10. In an ultrashort wave receiving system, a variable velocity electronic beam detector comprising means for generating .an electron beam, receiving anodes for said beam, means for producing an electrical field acting transversely to said beam and of a strength to deflected, said last