US2411963A

US2411963A - Signal receiver circuit

Info

Publication number: US2411963A
Application number: US440820A
Authority: US
Inventors: Roscoe H George
Original assignee: RCA Corp
Current assignee: RCA Corp
Priority date: 1942-04-28
Filing date: 1942-04-28
Publication date: 1946-12-03
Anticipated expiration: 1963-12-03

Description

Dec. 3, 1946. R. H.'GEORGE SIGNAL RECEIVER CIRCUIT Filed April 28, 1942 QREQQQQQ E Q INVENTOR R. H. GEORGE BY ATTORNEY Batented Dec. 3, 1946 star ,1.

2,411,963 SIGNAL RECEIVER CIRCUIT Roscoe H. George, West Lafayette, to Radio Corporation of America,

of Delaware Ind., assignor a corporation Application 'April 28, 1942, Serial No. 440,820

8 Claims. (01. 315 -22) The present invention relates to a system by which aircraft or the like may be guided efficiently. without sight of the significant areas toward which they are approaching, the areas from which they are departing, and the areas over which they are flying.

In my prior Patent No. 2,216,707 granted October 1, 1940, a system was disclosed by which it was made possible for the pilot of an aircraft to guide its flight path by observing, on the viewing target of a cathode ray tube, bright spots for each marker on the airport or other significant area toward which, over which, or from which the airplane is flying. Provision was made, according to the patent above discussed, whereby, on the viewing screen of the cathode ray tube, the spots representing adjacent significant areas were caused to appear in correct perspective, so that the ilot would, in a sense, actually see at least the boundary indications of the area in question. Further provision was made for controlling the operation of the system so that for changes in signal strength, an efliciently operating automatic volume control would function to maintain the indications upon the viewing tube.

One form of volume control, as applied to the circuit of Patent No. 2,216,707 particularly, was more specifically claimed and disclosed in Patent No. 2,289,493 issued on July 14, 1942, covering a divisional portion of the patent hereinabove referred to.

The present invention is one tending to improve upon the blind landing system disclosed in the aforesaid patent and application, and to provide an automatic gain or volume control for use in connection therewith, but, at the same time, provides an automatic gain control which improves upon the arrangements hereinbefore disclosed, which held the combined signal of the vertical and horizontal direction finding circuits to be of substantially constant value.

The present invention has, however, as one of its primary purposes and objects, that of providing proper observation of the resulting pattern, and at the same time, that of providing so that the ratio of the brilliance of the resultant spots as they produce indications upon the viewing target of the cathode ray tube shall be generally inversely proportional to the actual geographical distance of the observer from the significant area in question.

It has been found in the past that it is difficult to obtain extremely'great stability of operation with the types of gain controls heretofore used when the signals change abruptly, as in the case fit 'and at the same of signals transmitted with the type of blind landing system herein disclosed. Furthermore, with the type of automatic volume control and the general receiver arrangement heretofore disclosed, the true illusions of perspective which are so desirable in connection with a system of blind landing or blind guiding are lost, to some extent, or at least impaired, because with the light points on the target being represented at all times in the samebrilliance, irrespective of the actual location of the transmitter with regard to the plane, this objection has been overcome to a substantial extent by the resent disclosure.

In its broader sense, this disclosure has as its object, that of providing ways and means by which the defects of prior art arrangements are overcome. In this connection, it is possible to overcomethe defects hereinabove noted, simultaneously, by providing an automatic gain control which will control the beam voltage on the oathode ray tube in such a manner thatthe beam voltage is increased with an increase of signal strength. The result is that not only does the increase in the beam voltage at the tube cause an increase in the brilliance of the resultant spot appearing upon the luminescent target of the tube because of the increased velocity of beam impact, but, at the same time, the deflection sensitivity of the cathode ray tube is decreased because of the higher velocity of the beam resulting in a so-called stiffer beam, so that the automatic gain control thus inherently tends to provide the perspective features of the illusion. This has the effect then of changing the beam velocity or stiffness in such a manner that. the automatic volume control need not act as rapidly as those provided by prior art arrangements, time provision is made so that the automatic volume control can have a substantial voltage change produced and still be effective in its operation.

Other objects and advantages of the invention are those of providing a system which Simplifies the arrangements of the prior art and at the same time operates with a greater eificiency than did the arrangements of the prior art. Still other objects and advantages will become apparent to those skilled in the art to which the invention is directed by a reading of thefollowing specification taken in connection with the single figure of drawings which shows a relatively simplified form of receiver circuit arrangement.

Referring now to the drawing, the radio frequency amplifier detector units I, 3, 5 and I are all schematically illustrated. In this group of amplifiers and detectors it is intended that the units i and 3 shall connect respectively to the left side horizontal amplifier and rectifier 9, and and l to the right side horizontal amplifier and rectifier H. The output from these units is adapted to energize horizontal deflecting coils (conventionally represented at [4) connected to terminal points l3 and 1-5. The horizontal deflecting coils are not shown in detail, but the connection of-the amplifiers thereto will be apparent from what is to be indicated in connection with the vertical deflection and also from What has been shown in the aforesaid Patent No. 2,216,707.

Where desired, suitable automatic volume-control features, as indicated conventionally at H, may be incorporated with a horizontal receiving system. Signals to represent the as received and amplified in the radio frequency amplifier and detector .units 5 and 1 are supplied through the transformers 2i and 22 to be amplified in the amplifying

tubes

23 and 24. The output energy from these amplifying tubes is then fed by way of further transformers 26 and 21 to two additional stages of amplification represented by the

tubes

23 and, 29. Operating voltages for these tubes are supplied from the terminal points and 3|, as indicated, for the D. C. potentials, and the heater elements of the various tubes are energized from a suitable A. C. source in Well known manner (not illustrated). The output signals from the

amplifiers

28 and 29 are then fed by way of the transformers 32 and 33 to the rectifying

tubes

34 and 35. These tubes may be of any suitable typeknown in the art, for instance, as the double diode, and identifiable by the type number 6H6.

The heterodynefrequency introduced on the transformers 2i and 22 into the amplifier stages comprising the

tubes

23, 24 and 28, 29 is then filtered out by suitable condensers 36 and 37 connected across the output load circuit ofthe rectifrom the tubes 34 and through the differel tially connected

magnetic deflecting coils

38, 39 on the one hand, and 40, 4! on the other hand, and returns to ground potential at point 42 by way of the common output or load resistor 43. The coils 38,- 39 and 40, 4| are each preferably wound in two or more parts to more accurately superin known manner.

Within the cathode ray tube 45 there is provided the usual electron gun structure comprising the cathode 41, shield 46 which may serve also as a control electrode, an anode element 49 and-a suitable second anode element 50, which, together, form the cathode ray beam conventionally indicated by the dot-dash line 5|.

At times, when signals are received in the receiver detector units 5 and I andoutput energy flows through the

rectifiers

34 and 35 to produce a voltage drop across the resistor 43 caused by the combined signal currents, the resultant voltage drop is applied by way of a conductor 52 to the control electrode 53 of an automatic gain or'automatic volume control tube 54. The plate or anode element 55 high frequency voltage from an oscillator tube 56 vertical control of tube 54 is supplied only with having the tuned plate circuit comprising the inductance and capacity elements forming the tank circuit 57 and the tuned grid circuit formed from the inductance and capacity elements forming the tank circuit 58, and such energy is supplied to the plate or anode 55 through the coupling condenser 59.

In order to maintain a sufiiciently high A. C. plate voltage on the tube 54, a tuned tank circuit 68, comprising the inductance element 6i and the capacity 62, which is made resonant to the fre quency of the oscillator tube 56, is connected in series with the plate element 55 of the automatic Volume control tube 54. From this connection it can be appreciated that the current rectified in the plate circuit of the tube 54 will be proportional, because of the control exercised by the control electrode 53 thereupon, to the positive potential produced across the load resistor 43 in excess of any adjustable bias that is provided by way of the conventionally indicated variable bias means 63 applied to the cathode 64 of the au-- tomatic volume control tube 54.

As is indicated by the conductor 25, which is connected to the center tap of the secondary windings of the transformers 2| and 22, which also connects to the end of the tuned circuit 60, this rectified voltage is applied to one of the first stages of the amplifier, and, also, the same voltage is applied by way of a second conductor 66 to the control electrode 61 of the high voltage tube 68. A resistance 69 is connected between conductor 25 and ground to function as a grid resistor for

tubes

23 and 24.

The triode 68 is connected in parallel with the high resistance bleeder H1 which has one terminal thereof connected to, the plate or anode 1| of the tube 68, and the other terminal thereof connected to ground 42 by way of the conductor 12. The bleeder resistor 10 is intended to supply the various accelerating potentialsto the various electrodes of the cathode ray tube 45, and current to this bleeder-resistor is supplied by way of a resistor 13 which is connected at terminal point 14 to a source of high voltage (not shown).

Since the tube 58- is connected in parallel with the bleeder-resistor 10, it is, of course, quite apparent, that the total beam voltage developed within the cathode ray tube 45 may be varied over a very considerable range by any variation in the current passed by the tube 68, to produce a variation in the voltage drop across resistor '13. Accordingly, by a variation of the potential applied to the control electrode 6'! of this tube, the current flowing within the tube may be varied within relatively wide limits, so that varying amounts of current are by-passed from the bleeder-resistor 70.

In normal operation, the automatic gain control tube 54 is biased to approximately a cutoif point by means of the variable bias 63. This bias, where desired, may be taken from the main power supply by way of a suitable potentiometer. The adjustable bias T5 for the tube 68 is suitably adjusted so that with no signal being received, the impact point of the cathode ray beam 5| upon the luminescent target 46 of' tube 45 is just barely visible, but not of a brightness which maximum. Thus,'it is apparent that as the signal received in the amplifying and detecting units 5 and I and the normal operating levels are obtained, the voltage from gain contro1 tube 54 is such that a' is applied to the control electrode- 68 so that a decrease in the plate the automatic negative bias 6'! of the tube less current is drawn in the shunt path include.

ing thetubefiil. This decrease of current through the tube BB're's'ults not onlyina bright impact point on the target area '48, but also results in. a=decreasein sensitivity of deflection of the tube,

because it permits a higher accelerating; voltage to be applied to form the cathode ray beam 5i, and consequently, the electronsof the beam are moving through the tube 45 more rapidly so as to be less subject-to a' shift in location'on the target by any predetermined deflection energy than would an eIectron beam formedof less rapidly movingelectrons; .Y I

- With the arrangement as it is disclosed, the automatic gain control tube 54 is so-arranged that it can permit a considerable rise in the output of the receiver instrumentality, comprising the various amplifiers hereinabove described, with any increases in sign'als'trength, and yet have thisrise in the output'signal compensated for by the increased stiffness of the beam, that is,

the beam is moving so rapidly that/the sensitivity of the tube deflection system-becomes less.

'It is, of course, possible'to vary, to some ex-' tent, the control arrangement herein disclosed, by'replacing the control tube 68 by-afltetrode, for instance. Transients which occur across the 'c'oils'33, 39 and itl, 4| may be' rectified, where desired, and applied, for'instance, atthe term'inal points 76, ll of the" tube 29 in such a way as'to cut off the beam 5| developed within the tube during the period of readjustment when changing from a strong signal to a weak one, or the reverse.

Still other modifications may readily be made, provided such modifications fall fairly within the spirit and scope of what is herein set forth and what is claimed in the claims following.

Having described the invention, what is claimed 1. Signal reproducing apparatus comprising means to receive and amplify signal energy, a cathode ray tube having included therein means to develop an electron beam and means associated therewith for deflecting the developed electron beam under the control of applied energy, means to rectify the received and amplified signals, means to energize the beam deflecting means under the control of the said rectified signals, an automatic volume control tube, means included within the signal reproducing apparatus for locally generating alternating current energy for energizing said automatic volume control tube, means for applying the rectified energy to the control circuit of said automatic volume control tube, and means controlled by the ouput energy of the automatic volume control tube for varying the velocity of the developed cathode ray beam whereby the intensity of the light developed thereby varies with the variances in the intensity of the received signals.

2. The system claimed in claim 1, wherein the last named control means includes an electron bleeder tube.

3. Signal reproducing apparatus comprising means to receive and amplify signal energy, a cathode ray tube having included therein means to develop an electron beam and means associated therewith for deflecting the developed elec tron beam under the contro1 of applied energy, means to rectify the received and amplified signals, means toienergize the beam deflecting means under the control 10f the said rectified signala'an" automatic volume'control tube, means-included within the signal reproducing apparatus for 10- cally generatingalternatingcurrent energy and supplyingsaid energyto .the output circuit of. said automatic volume control tube, means for applying the received rectified energy to thecontrol circuit of said "automatic volume control tube, an inductive means connected to receive the output energy from the'automaticvolumelcontrol tubeiand to supply said energy to the amplifier means to vary the amplification of the received signals in the amplifier, and electronic means controlled by the output energy of the automatic, volume control tube for varying the velocity of the developed cathode ray beam.

4. Signal reproducing apparatus comprising means to receive and amplify signal energy, an oscillation generator for generating energy at a frequency relatively high with respect to that of the signal energy received, a cathode ray tube having included therein means to develop an electron beam and means associated therewith for trol of the said rectified signals, an automatic volume control tube, means for supplying the 10- callyr-gen'erated high frequency energy to the output circuit of said automatic'volume control tube,'and means for applying the rectified energy to the control circuit of said automatic volume control tube, means responsive to the output energy' from the automatic volume control tube for varying the amplification of the received signals in the amplifier, and means controlled by the output energy of the automatic volume control tube for varying the velocity of the developed cathode ray beam, whereby the intensity of the light developed thereby varies with the variances in the intensity of the received signals.

5. Signal reproducing apparatus comprising means to receive and amplify signal energy, a cathode ray tube having included therein electrode means to develop an electron beam and means associated therewith for deflecting the developed electron beam under the control of applied energy, a bleeder resistor to control the voltage supplied to the beam forming electrodes, means to rectify the received and amplified signals, means to energize the beam deflecting means under the control of the said received rectified signals, an automatic volume control tube, means for locally generating alternating current to energize said last named tube, means for applying the rectified energy to the input circuit of said automatic volume control tube to produce an output voltage proportional to the intensity of the received signals, means responsive to the output voltage from the automatic volume control tube for varying the amplitude of deflection of the developed beam and the velocity of the developed cathode ray beam, whereby th intensity of the light developed thereby and the raster dimensions vary with the variance in the intensity of the received signals.

6. Signal reproducing apparatus comprising means to receive and amplify signal energy, a cathode ray tube having included therein means i to develop an electron beam and means associnals, meanstoenergize the beam deflecting means.

under'the control of thesai'd amplified and rectified signals so that the deflectionis proportional to signal intensitman automaticxvolume control tube, a. source of alternating current energy for. energizing said automatic volume control tube, means, for supplying the. rectified signal energy. to the. control circuitof said automatic volume con! trol tubev so that the output energy is, a direct current. proportional. tov thereceived signal in-.- tensity, inductive. means connected: to the output circuit, of the automatic volume control tube for supplying the output. energy therefrom .to. the amplifying means so that the amplification of the received signals in the amplifier is varied, and electronic means also controlled bythe output energy of the automatic volume control tube for varying the velocity of the developed cathode ray beam, whereby the intensityof the light developed thereby varies with the variances in the intensity of the received signals and the deflection is variable with variances in the rectified received energy.

7. A signal reproducing apparatus. comprising means to receivev and amplify independently of each other two time separated versions of signal energy of a. predetermined character, a cathode trol tube, means to generate alternating current energy to energize said last named tube, means to; supply the .said; rectified and; combine signal.

energy to said last named tube, so that the. output. energy therefrom is adirect currentof an ins. tensity proportional tot-he received signal inten-, sity, means to. supply said direct, current to the amplifying means, to. control the amplification level thereof and. means to. simultaneously control the intensity ,of; the cathode. ray beam deray beam, and means associated therewith for .de-

fleeting the cathode ray beam under the control of applied energy, rectifying means for rectiiymg each of the amplified signals, meansfor dififerentially applying the output of the rectifying means to. the. deflecting means for energizing said means in accordance with the differential output of the said two rectifying means, automatic volume control means connected to develop biasing voltages proportional to the received signal in tensity, means for controlling the amplification level of the amplifying means. in accordance with the voltage output of the automatic volume COD-.- trol means, and means for varying the velocity of the cathode ray beam developed proportional to the output of the automatic volume control means, whereby the light initiated by the impact of the cathode ray beam upon a target element is of an intensity proportional to the signal strength.

I ROSCOE H. GEORGE.