US2432180A

US2432180A - Radio pulse-echo system

Info

Publication number: US2432180A
Application number: US515496A
Authority: US
Inventors: Simeon I Tourshou; Trachtenberg Robert
Original assignee: RCA Corp
Current assignee: RCA Corp
Priority date: 1943-12-24
Filing date: 1943-12-24
Publication date: 1947-12-09
Anticipated expiration: 1964-12-09

Description

2 Sheets-Shee't 1 Dec. 9, 1947.

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Patented Dec. 9, 1947 RADIO PULSE-ECHO SYSTEM Simeon I. Tourshou,

Philadelphia,

Pa., and

Robert Trachtenberg, Camden, N. J., assignors to Radio Corporation of America, a corporation of Delaware Application December 24, 1943, Serial No. 515,496

6 Claims. (Cl. 250-27) Our invention relates to pulse-echo radio systems and particularly to the production of electrical pulses.

One object of the invention is to provide an improved and simplified circuit for producing two groups of periodically recurring pulses.

Another object of the invention is to provide an improved method of and means for producing a delayed electrical pulse.

A further object of the invention is to provide an improved method of and means for producing two groups of periodically recurring pulses which have a fixed time relation to each other.

A further object of the invention is to provide a receiver that will draw a comparatively small amount of +3 or high voltage direct current.

In one embodiment of the invention a circuit is provided for producing periodically recurring narrow pulses for pulse modulating a radio transmitter and for producing periodically recurring pulses of greater width to function as gate pulses for the pulse receiver. These two groups of pulses are produced by means of a blocking oscillator or the like which applies very wide pulses to a pulse forming delay line or network to charge the capacitors of the line during each wide pulse and which also applies the very wide pulses to a separate capacitor to charge it also during each blocking oscillator pulse. At about the peak of each blocking oscillator pulse a gas or vapor tube, which is connected for discharging said line and said capacitor, is ignited by a delayed blocking oscillator pulse so that the pulse forming line and the separate condenser discharge therethrough. This produces a "gate pulse which appears at the end of the pulse forming line. It also produces a narrow transmitter modulating pulse which appears across the secondary of a transformer that is connected in series with said separate capacitor and said vapor tube.

Also, according to one feature of the invention, the pulse forming line is so connected to a delay network that the gate pulse is retarded the desired amount without affecting the operation of the pulse forming line.

Other objects, features and advantages of .the invention will appear from the following description taken in connection with the accompanying drawing in which Figure 1 is a circuit and block diagram of a pulse-echo system embodying the invention,

Figure 1a is a group of graphs illustrating the operation of the system of Fig. 1, and

Figures 2 to 6 are graphs illustrating the op- 2 eration of the pulse forming circuits shown in Fig. 1.

In the several figures, similar graphs are indicated by similar reference characters.

Fig. 1 shows the invention applied to a pulseecho system comprising a radio pulse transmitter oscillator ID, a radio pulse receiver ll, an intermediate-frequency amplifier l2, a second detector and video amplifier unit l3, and a suitable indicator l5 for indicating the reception of reflected pulses. The amplifier I2 is adjusted so that it will pass received signals only during the occurrence of a gate pulse i l which, in the example illustrated in the drawing, is applied with positive polarity to the screen grid of an intermediate-frequency amplifier tube l2a.

In a preferred receiver the I.-F. amplifier comprises a plurality of L-F. amplifier tubes in cascade and the gate pulse I4 is applied to the screen grids of all these tubes except one or more which may be the last L-F. tube which has a manual gain control voltage applied to its screen grid. It will be noted that there is no D.-C. voltage applied to the screen grids of the I.-F. tubes (with the exception of the last I.-F. tube) with the result that there is a substantial saving in the +3 power supply since it does not have to supply screen grid and anode currents continuously.

The oscillator H3 is modulated by a voltage pulse l 6 which appears across the secondary of a transformer H. The apparatus for producing the gate pulse [4 and the modulating pulse It comprises a suitable pulse producing oscillator such as a freerunning or self-oscillatory blocking oscillator l8 which applies wide positive voltage pulses I9 (Fig. 2) to the anode 2i of a gas or vapor tube 22 such as a Thyratron.

The blocking oscillator i8 is of conventional design and comprises a vacuum tube 23, a feedback transformer 24,

grid leak resistors

26 and 21 and a grid capacitor 28 connected between the junction point of

resistors

26 and 21 and a point on the secondary of the transformer 24. A source of sine wave voltage may be substituted for the blocking oscillator 18 if desired.

The high potential end of the secondary of transformer 24 is connected through resistors 3| and 32 to the anode 2| of the vapor tube 22 for applying to the anode 2| a positive pulse 19 (Fig. 2). The same positive pulse 19 is applied across a resistor 33 and a capacitor 31 whereby a delayed pulse 20 (Fig. 3) appears across capacitor 31.

The delayed pulse 20 is applied to the grid 33 of the tube 22 through a resistor 34. The capacitor 31 and the resistor 36 are given such values as to introduce a suitable phase shift in the voltage pulse 20 to ignite the tube 22 preferably a short time after the pulse l9 has reached its maximum positive value .as will be apparent from a comparison of Figs. 2 and 3.

The gatepulse isproduced by" a. pulse forming'.

line 38 in the form of a network having series inductors and shunt capacitors which has its inductor side connected to the anode 2| of the vaportube 22 so that it is charged by the. first portion of the blocking oscillator pulse l9. At the same time that the line 38 is being charged, acapacitor 39, which is connected between: the anodeZl of tube 22 and the primary I'l'a of transformer I1; is also charged. An inductor H is also included in series with the capacitor 39 and the. trans former primary Ila unless the leakage inductance of transformer l! is itself large enough-for-prmducing a pulse I6 of the desired width when the capacitor 39 is discharged. Changing the amount of inductance in the circuit in series with capacitor 39 changes the width of the pulseslfi since this pulse actually is 'one half-cycle of a damped sine wave in a. series resonant circuit as indicated by the'dotted' lines in Fig. 6. However, thisv damped. Wave is-substantially of the form shown. by the solid linesince the tubes 40 and. 85 put' a low impedance load across the secondary of. trans-- former H.

The delayed pulse 20- on the grid 33. of. the. vapor:tube'22.- causes the tube 22 to ignite or: break down at about the time the blocking. oscillator: pulse l9. has applied a. maximum charge to. the; pulse-forming line 38' and to thecapacitor. 3.9;: When the tube 22' breaks down, it discharges. the. line 38 to forms. pulse Eta of a width-or duration that is equal to the time required for: a wave. to. travel from one end of the line 3 8-:to the other end ofthe line andback. In.the.example given. this pulse width is 3 ,4 microseconds.

The breakdown of vapor tube. 22 also. dis-- charges the capacitor- 39. through the inductor. M and the primary 'la.of transformerlkwhereby-the narrow pulselfi is produced. In the-pres.- en't -example' the widthof pulselfi is. micro second. By making transformer IT a. voltage step up transformer, the pulse l6. mayibeimade of high enough amplitude so that when. applied to the-anodes of the tubes 49 and 455of5th'eradi'ofrequency oscillator H]. the oscillator" oscillates during. the application of the pulse. In.the.ex ample illustrated, there. is no D. 0.. voltage on the oscillator anodes. The oscillator- I is: conventional in= design having a tuned. line:.50, .inxthe plate-circuit and: having the cathodesof tubes 46 and 35 operated above ground; potentialat the radio frequency.

The modulating pulse ifi'preferablyt'is'z applied to" the oscillator l0. through resistor-capacitor biasing elements 43- and Ml, respectively; and: through a radio-frequency choke coil 46'; Dure ing the pulse it: the. D. C. anodecurrent of the. oscillator tubes. 40 and 45': flows .throughatheebias ing elements 43. and M" to charge the: capacitor it whereby the anodes of tubes iiiand iiiib'ecome negativesomewhat before the endof the modulation' pulse 15 resulting in a sharper cut-=01? of theoscillations; also, they are held negative-long enough to preventanyp'ositive components that might follow the pulse l from" energizing the oscillator lfl.

Referring again to the production of the gate pulse I 411-, the pulse i l from the pulse-forming line38 is delayed the desiredamount by'a delay" network 41 which comprises series inductors and shunt capacitors, the amount of delay being about one and one-half microsecond, for example, as indicated in Fig. 5.

The output end of the delay line 41 is connected to a transformer 48 shunted by a resistor 49 towprovide a non-reflecting termination. Also,

means preferablyare provided for sloping the front edge of the gate pulse 14 whereby the sensitivity or gain of the intermediate frequency amplifier. 12 is the greatest when reflected pulses l'iia (Fig. 1a) are received from the more distant part: of the. pulse reception region. This also results inan improved signal-to-noise ratio. The pulse sloping means may comprise a, resistor 5| and a capacitor 52- connected in series with each otherand-inshunt to..the transformer 48. It may be noted that the gain of the receiver as plotted againsttime has a greater slope than that of the gate pulse [4 since this pulse is applied to a pluralityr of I; F. amplifier: tubes-in-cascada- In order" that the two linesor networks 38:.and. t! shall perform their pulse forming and pulse. delaying. functions independentlyv ofeach other, the series inductor sideof network l'lisconnectedi to that side. of. networkrSB which-isopposite-its. series inductor side. The end of. thenetwork flt remote from the charging endisopen-circuited: and, therefore, reflecting. Theimpedance 'loob' ing'into the input endv ofthe:networlc l'l 'issubstantially equal to; the surge. impedance of; the; network 38.

We claim as our: invention:

1. In a pulse-echo system; meansvforproducing-periodically recurring electrical voltage-waves; each. of, positive polarity and; ot comparatively longduration, a. pulse-forming.-v delay: line and: a gas or vapor. tube-connectedto. discharge-said line for: forming; a; pulse. when said. tube is: ignited; a. capacitor and apulse-forming circuitconn'ected; in: series: with: the cathode-anode impedance oi: said-tube, means .for applying said voltage simultaneously to saidlinapto the anode-of. said tube andito said capacitor, and: means'foridise' charging; said line and said. capacitor. through said. tube: after each has. been charged; Icy-one of .said voltage waves.

2; In a pulse-echo systemnmeans, for producing: periodically recurring, electrical. voltage waves eachwof positivepolarity and-ofi compares tively; long. duration, a pulse-forming; delay. line anda gas or vapor tube connected tor discharge said linewhensaid tube; is ignited; ,.capacitor anda pulse-forming circuit; connected miseries. with: the cathode-anodeimpedance. of said tube; means forapplying. said. voltage waves-simultaneously to said. line, to .the anode of said: tube and .tesaid capacitor, and means'for.also..appiye ing said. voltage waves to. the control electrode of said tube. slightly delayedwith.respectitoithe voltage .waves. appliedjto said anodawhereby, said line. and. said' capacitor. are both discharged through said tube after being chargedlby-on'epf said voltage waves;

3; Irrapulse-echo system; meansfor'produm ing periodically recurring electrical voltagewaves each" of positivepolarity and of comparatively long duration, pulse-forming delay 'lineand a gas 1 or vapor" tube connected to" discharge said line to form a pulse when said tube is ignited;- a' capacitor-"and an inductor connected in series with the--ca-thode-anode impedance of sa-idtube to" form a pulse when said capacitor is diseliarged, means for applying said" voltage waves Sim-uhtaneously-to-saidline; to theanodeof said tube and to said capacitor, and means for also applying said voltage waves to the control electrode of said tube slightly delayed with respect to the voltage waves applied to said anode whereby said line and said capacitor are both discharged through said tube after being charged by one of said voltage waves,

4. In combination, a pulse-forming delay network comprising series inductors and shunt capacitors and having input terminals, at one end of the network and a reflecting termination at the other end of the network, one of said terminals being common to both ends of the net work, a second delay network comprising series inductors and shunt capacitors and having input terminals and output terminals and having a substantially non-reflecting termination at its output end, said terminals of the second network including a terminal that is common to both ends of the network, the common terminal of one of said networks being connected to the input terminal of the other network which is not common to both ends of the network, and means connected to the two remaining input terminals of the two networks for periodically charging and discharging said first network whereby periodically recurring delayed pulses are produced.

5. In combination, a pulse-forming delay network comprising series inductors and shunt capacitors and having input terminals at one end of the network and a reflecting termination at the other end of the network, one of said terminals being common to both ends of the network, a second delay network comprising series inductors and shunt capacitors and having input terminals and output terminals and having a substantially non-reflecting termination at its output end, said terminals of the second network including a terminal that is common to both ends of the network, the common terminal of said first network being connected to the input terminal of the other network which is not common to both ends of the network, and means connected to the two remaining input terminals of the two networks for periodically charging and discharging said first network whereby periodically recurring delayed pulses are produced at the output terminals of said second network.

6. In combination, a pulse-forming delay network comprising series inductors and shunt capacitors and having input terminals at one end of the network and a reflecting termination at the other, end of the network, one of said terminals being common to both ends of the network, a second delay network comprising series inductors and shunt capacitors and having input terminals and output terminals and have a substantially non-reflecting termination at its output end, the input impedance of the second network being substantially equal to the surge impedance of the first network, said terminals of the second network including a terminal that is common to both ends of the network, the common terminal of said first network being connected to the input terminal of the other network which is not common to both ends of the network, means connected to the two remaining input terminals of the two networks for'charging said first network, and means for periodically discharging said first network whereby periodically recurring delayed pulses are produced at the output terminals of the second network.

SIMEON I. TOURSHOU. ROBERT TRACHTENBERG.

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

UNITED STATES PATENTS Number Name Date 2,189,549 Hershberger Feb. 6, 1940 1,924,174 Wolf Aug. 29, 1933 2,223,995 Kotowski et al Dec. 3, 1940 2,281,441 Horton et a1. Apr. 28, 1942 2,309,525 Mohr Jan. 26, 1943