US2220183A - Impulse direction finder - Google Patents

Description

NQY 5, 1940 G. ULBRICHT 1 2,220,183

L v IMPULSE DIRECTION FINDER .Filed June 25, 1959 r Gunther UZbri/ch Bg y l v Gttc'arneg lnventor l lPatented Nov. 5, 1940 IMPULsE DIRECTION FINDER AGnther Ulbricht, Blankenfelde, Germany, asl signor to Telefunken Gesellschaft fr Drahtlose Telegraphie m. b. H., Berlin, Germany l Application' June 25, 193s, serial No. 215,759

' In Germany July 8, 1937 i solaires. `(c1. 25o- 11) This invention relates to impulse direction nders, particularly of the type in which the discrete impulses are viewed on a Braun tube indicator provided with a time basescanning potential. Among the objects of this invention are the l provision of means for increasing the accuracy lof indication by generating a scanning potential which has such a shape that the time intervals at which impulses are actually received are esppecially emphasized, and the application of the scanning potential to control an electronic switch by means of which the loop polarity is successively reversed to obtain automatic synchronization.

This inventio-n will be better understoodfrom vthe following description when considered in connection with the accompanying drawings, in which Figure 1 represents a saw-tooth scanning y L potential used in the prior art; Figure 2 represents a scanning potential in accordance with this I y 2o invention; Figure 3 is a schematic diagram of an impulse directionnder; and Figure 4 is a curve representing the voltages which are applied lto one of the switching tubesl of thedevice shown in Fig. 3.

To produce a standingv picture of arecurring impulse on the screen yof the cathode rayoscillovgraph there must be provided anifalternating scanning voltage which deflects the cathode ray beam at a rate proportional to time. The alter- 230 hating lvijiltagaplott'ed as a function of time,

customarily has the form of a saw tooth as shown in Fig. 1. Since, in general, only the center of the screen is utilized for observation of the sig-l nals, it is herein proposed to provide a deflection '35 Voltage which deflects the beam during only a portion ofreach cycle,A as illustrated in Fig. 2. Thus the cathode ray beam moves rapidly across the screen during a portion of thetime and is stationary during the remainder of the time, so

f pressingthe frame voltage upon the grids of two 'Ihe anodes of these tubes.

commutator tubes. work in push pull, and the tubes are rthen alternately blocked and opened. Blocking and opening may be done by a motor switch, or the like. According to the present invention, the deection voltage for the cathode ray` of theBraun tube is also used for the blocking and opening of` the commutator tubes. This voltage preferably has the form of the curve in Fig. 2.

A voltage of this type may be obtained by 5 applying the saw-tooth voltage illustrated in Fig.- 1 to a limiting amplifier A which cuts off the negative and the positive voltage peaks. Such an amplifier is illustrated in Fig. VIII of United States Patent No. 2,086,918, wherein the amplifier lo is similarly used to limit the positive and negative peaks of a sine wave voltage, as shown in Figure IX of'the patent. A wiring diagram is shown in Fig. 3. The Voltage from a frame antenna G is impressed in like l5 phase on the grids of a pair of commutator tubes T, T1 through coupling capacitors D. Out-ofphase control or keying voltages -are impressed on the grids of the tubes by a center-tappedr transformer U1, the primary of which is energ@ gized by a synchronized keying and scanning relaxation oscillator K. A push-pull output transformer U2 couples the commutator tubesto the input'of an amplifier-detector HF. The voltage` v from a non-directional antenna H is also coupled 25 I'he working point of the tubes is determined ,Y

by a biasing potential Ego (A in Fig. 4) Whose value is such that when the received 4voltage is superposed on the positive wave front of thel keying Voltage U the tube is opened up to 'opti- 40 mum working point (B) and on superposition of the negative wave front the tube is completely blocked as shown at (C).v

Fig. 4 represents the plate current-grid voltage characteristic Ja=f(Eg) of one ofthe commuta- 45 tor tubes, and shows-the impulse-voltage U and` the high frequency received impulses I-IF at the moment one of the tubes has been opened by the impulse voltage. y

In Fig. 4 there is drawn only the characteristic 50 of one tube. The working point B results from the positivev wave front of the voltage VU. The

other tube is opened by the negative Wave front of the voltage U.

Opening and blocking of the tubes may be ac- 55 complished also by impressing the bias voltage upon another electrode, for instance the screen grids of the tubes.

The transformer may be so designed that it transforms essentially only the sinusoidal fundamental of the impulse-voltage, for the duration of one received impulse is generally small in comparison to the period of the impulse voltage.

In either case it is necessary to control the phase relation between the received impulse and the keying impulse voltage; i. e., the impulses must arrive when first one and then the other of the keying tubes is conducting, as shown in Fig. 4. This may be accomplished in the manner described in the oopending application of Sonnentag, et al., Serial No. 194,554, led March 8, 1938, and entitled Impulse direction finding.

Direction finding by this device is accomplished in the customary manner. The combination of the frame antenna voltage with the nondirectional antenna voltages While alternatively reversing the phase of one of said voltages, produces the vvell known crossed cardioid directivity pattern. Two impulses are successively received Whose respective amplitudes vary as a function of the orientation of the frame antenna. The bearing is determined by that position of the frame antenna in which the tivo impulses are of the same amplitude. In the case illustrated, the cathode ray is limited to alternate substantially equal periods of rest and periods of scanning'. The beam moves horizontally in a given direction once for each received impulse, the return Voltage being too rapid to make a perceptible trace. Consequently, the two impulses may be superimposed on the cathode ray screen, and the condition of equal impulse amplitude will be indicated by the minimum amplitude of the observed impulse, since rotating the loop in either direction causes one or the other of the impulses to become greater in amplitude.

One advantage of the arrangement according to the present invention consists in the use of an existing alternating voltage for commutation of the frame voltage, thus providing automatic synchronizing. Another advantage lies in the use of a deiection voltage having the form, illustrated in Fig. 2, such that the received impulses are drawn forth from another; thereby the reading of the impulse is more precise. The deflection voltage for the cathode ray of the Braun tube is impressed upon a time delay arrangement PH. By this means the deflection voltage is retarded so that each deflection of the cathode ray of the Braun tube occurs during the moment at which a high frequency signal is applied to the tube.

I claim:

l. An impulse direction lnder having a cathode ray oscillograph, means responsive to periodically radiated impulses of short duration for deecting said ray in a lirst direction, and scanning means for deilecting said ray in a second direction in synchronism With the period of said impulses, said scanning means including means for limiting the motion of said ray to periods of time less than the period between said impulses.

2. An impulse direction finder having a cathode ray oscillograph; directive means responsive to periodically radiated impulses of short duration for deilecting said ray in a rst direction.; and other means for deflecting said ray in a second direction in synchronism with said impulses, said other deflecting means including means for limiting the deection of said ray in said second direction to periods of time less than the period between successive impulses.

3. An impulse direction finder having a cathode ray oscillograph; a receiver having a directional antenna responsive to periodically radiated impulses of short duration, the output of said receiver being coupled to said oscillograph for defiecting said ray in a first direction in response to said impulses; and means for deflecting said ray in a second direction, said deiecting means including an oscillator synchronized With the frequency of said impulses, and a limiting a1nplilier for cutting on" the positive and negative peaks of said oscillations whereby said deflection in said second direction is limited to periods of time less than the period between successive impulses.

4. A device of the character described in claim 3 which includes means for adjusting the periods of deflection of said ray in said second direction to include the times at which said ray is deiiected in said iirst direction in response to said impulses.

5. An impulse direction finder having a cathode ray oscillograph, means responsive to periodically radiated impulses of short duration for deflecting said ray in a iirst direction, and scanning means for defiecting said ray in a second direction in synchronisin with the period of said impulses, said scanning means including means for limiting the motion of said ray to alternate substantially equal periods of rest and periods of scanning.

GNTHER ULBRICHT.

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