US2648038A - Antenna sector scan control - Google Patents

Description

Aug. 4, 1953 T. B. MORSE ET A1.

ANTENNA SECTOR scAN CONTROL Filed May 3, 1946 ATTORNEY Patented Aug, 4, 1953 A HTED STATES ANTENNA SECTOR SCAN CONTROL Application May 3, 1946, Serial No. 666,882

8 Claims.

This invention relates to sector scanning mechanism for a radar antenna and more particularly to means for automatically scanning any desired sector.

The invention is intended primarily for remotely controlling sector scanning of a radar antenna in a radar relay system wherein a searching radar is used to obtain radar data and relay such data to some remote location.

It .is an object of this invention to provide automatic scanning of a selected sector by a radar antenna.

Another object of this invention is to provide means for selecting the sector to be scanned.

A further object of this invention is to provide means for scanning a sector of any desired angular Width.

These and other objects will be apparent from the following specications when taken with the accompanying drawing in which:

Fig. 1 is a schematic illustration of one form of the invention; and

Fig. 2 is a block diagram of a system including the circuit of Fig. 1.

Referring rst to the system of Fig. 2 there is shown an antenna 5 coupled to antenna drive motor B by a mechanical link schematically illustrated by the dashed line 1. Power is supplied to antenna drive motor 6 from a source 9 through a reversing control I0. Reversing control I is shown coupled to antenna drive motor 6 by connections y8. Antenna drive motor 6 may be any form of electric motor that may be reversed by changing the polarity or phase of the power supplied thereto. However, the motor 6 may take other forms if desired, for example, a reversible steam driven engine or turbine. If an electric motor is employed, reversing control l may take the form of a relay controlled double-pole, double-throw reversing switch, the energy to the relay coil being supplied at terminals Il.

In certain applications of the present invention it may be desirable to locate the antenna 5, the antenna drive motor 6 and the reversing control I6 in a moving vehicle, for example an airplane in flight, while the control circuit I2 is located at a fixed point on the ground or in a second vehicle. If this is the case, the control signal appearing at terminals Ila of control circuit I2 may be coupled to terminals II by a suitable radio relay link illustrated as dashed lines IIb in Fig. 2. For reasons that Willlappear presently, it will also be necessary to couple position data from antenna to control circuit I2 as illustrated by the dashed line 1a.' in Fig. 2. This may be accomplished by a second radio relay link or by a second channel in radio relay link IIIb. The broken line A-A in Fig. 2 has been added to clearly point out the line of separation between units in the moving vehicle and units at the second location.

In still other applications of the present invention all of the units shown in Fig. 2 may be located in the same vehicle in which case the dashed line 1a. may represent an appropriate mechanical connection and dashed lines IIb appropriate electrical connections. Since the present invention is primarily concerned with the novel features of the control circuit I2 rather than the vspeciiic arrangement of the system in Fig. 2, the details of control circuit I2 will now be explained by reference to Fig. 1.

Briefly, the circuit of Fig. 1 operates as follows: Azimuth information from the radar antenna 5 is supplied to synchro I3 by connection la. Synchro I3 supplies this azimuth data to a control transformer I5. The rotor of the control transformer I5 is positioned manually by hand control I5a to select the bearing of the sector to be scanned. The control transformer develops an error voltage whose phase and magnitude are proportional to the error between its manually positioned rotor and the antenna position data supplied by the synchro. This error voltage is variable in amplitude to set the size of the sector scan and is used to operate a dilerential relay. As the antenna rotates away from the selected sector bearing the error voltage developed by the control transformer after covering a certain angle becomes large enough to operate the differential relay to operate the antenna reversing means. The antenna then passes back past the selected sector bearing and develops an increasing error voltage in opposite phase. When the antenna has traveled far enough the error voltage developed again operates the diierential relay to operate means for reversing the antenna again. Thus the antenna is made to scan a selected amount either side of said sector bearing.

Referring again to Fig. 1 the operation of the circuit will be described in detail. Azimuth information is received by antenna synchro I3 at connection 1a, which causes synchro I3 to rotate in synchronism with the antenna 5. The rotor of synchro I3 is energized from an alternating voltage source illustrated in Fig. 1 by terminals' Ill and I 6. Alternating current is also supplied at terminals I 8 and 20 to contact 22 01 tioned by a hand control Ict anxl'determinesV thebearing about which the sector scanning is, done. When the position of the rotor in control transformer I5 corresponds to the position of the rov tor in the antenna synchro, there will be no, output voltage from the rotor of control transformer I5. The rotor of control transformer I5 connects through potentiometer 48 to the primary ;52 of transformer 36.

An error voltage is produced in winding 52 whenever the angular position of the rotor in control transformer I5 differs from that of the ;rotor in the antenna synchro. The phaseV of the ,errorvoltage depends upon whether the rotor of .control transformer leads or lags that of the antenna synchro, and theamplitudeof the error -voltage depends upon the `extent of lead or lag. lThe secondary of transformer 36 is c entertapped so that error voltages of the same amplitude but .of opposite phase areapplied to grids 54 and. 56 .of the two halvesof rectifier tube-36. l-f there is no error voltage,y the plate current will be the vsame inl the two halves of tube 38 vand in the l*coils* 4.2- and-44 of; relayV 46. This holdsy contact 156, in its neutral position. When an error volt- :age is present it wi-llbe essentially-inphase with :the plate `Voltage on one half of tube 36 and essentially 180 out of phase on the other half'. The. outputy of one` half oftube yiii). is increased and that ofV the,V other halfis decreased. When thiserror voltagereaches a predetermined value, itjWill actuaterelay 46V which in turn actuates latch-inrelayfil which is latchedf in the up or fdown position depending upon the relative angular' position ofthe antenna at the time.

The angular. vposition of the rotor ofY control transformer i5, isset manually to select the center-bearing about which the sector scanning is performed The amplitude or size of-` the sectorfis controlled; by variable tap 62 on `potentiometer 41%; This pick-off tap determines the fraction of the*y error voltage thatxisf-appliedto theprimary- 5.2V of'transformer 36; The lower the settiiygV of, resistance 48; theVv greater .must be the error voltage from control transformer I5 tozactuate dierentialrelay'd; As a result the scan amplitude is increased.

Now that the basic componentsI have-beendescribed, the` details of relay operation etc. will be described by. following through a complete cycle ofi the system. Switch 28 is normally int-he up` or -continuousscan position, relay. 66V is in. the up ..position and the antenna is continuously -rotating in a clockwise direction. Assume that switch 2.8.. is. thrown down for sector scanning as. the antenna; is approaching the selectedA sectorbearing. Assoon asthe antenna passes the selected 'bearingan erro r voltage of increasing -amplitude is. developedand is appliedinphasey to grid 56 offtlhie 'lower half of di'scriminator recati-,- ''er 36 and out, ofphase to grid '54` of the upper half ofi. tube 66,.A As the outer boundary. of `the ,scan sectfo'rlvisreached'. the outputof rectifier'V 30 is large enough to operate relay 46 and pull cori-- tact 58 down which energizes coil 62 to close contact 66 at point 68. This closes the circuit to the terminals Ila with the result that rotation of the antenna is changed to the counterclockwise direction. This direction of rotation is continued until thev antenna again passes the center of the sector and reaches its other limit. After passing the selected bearing an error voltage of increasing magnitude but opposite in phase is developed. When the amplitude is large enough, coil 42- of relay 46 is energized to pull contact 58 to ,theup position which in turn energizes coil 64 of relay 6.0. Coil 64 opens contact 66 which breaks Vthe circuit to the radio control transmitterwhich results in reversing the antenna rotation once more.

When switch -28 is returned to the up position for continuous antenna rotation, the heater of rectier tube 3B is kept energized to keep the circuit ready for immediate sector scanning operation. Also if relay 5.0 was last in the down position to provide counterclockwise antenna rotation coil 64 is energized through contacts 'I0 tov operate relay 6i)V and open contact 66 to give `clockwise antenna rotation as before on continuous scanning.

Thus it may be seen that. our invention provides a means for automatic scanning of any predetermined angular width about any selected bearing angle. It should be noted that although our invention has been described as. providing azimuth sector scanning. it may readily be used for angular scanning in any plane.

It is believed that the constructionandoperation as well as the advantagesof` our improved sector scan control will be apparent from the foregoing detailed description thereof. It will also. be apparent that while we have shown and described our invention in a preferred form, changes may: be made in' the: circuit disclosed without departing from they spirit ofthe. invention as sought to be definedA in the following claims.

What isclaimed. is:

l.. in a motor driven scanning antenna system 'includingv means for reversing the drive of said motor in response to a change in signal applied thereto, an electrical system for causing said antenna -to oscillate through' a predetermined arc comprising, a synchro transmitter unit and a control transformer electrically coupled at their respective stator windings, said synchro unit having` its rotor mechanically coupled to said antenna sofas to rotate in synchronism therewith, meansV coupled to saidY control transformer for positioning'the rotor thereof at apredetermined angle with respect' tothe stator ofY said control transformer to select a reference point on said scanningarc, a differential relay-having first and second coils, r'standsecond phase-sensitivedetectors electrically coupling the rotor ofv said controltrans-former to said firstpandrsecon'd coils respectivelyV the relative amplitudes ofi the sigi nals app'lieditosaid 'first -andvsecond coils of 'sai-d relayA beinga function-of the' phase and amplitude of thezsignal at;the rotor of said control trans former, saidrelay being adapted, to complete a nrstycircuit when: the unbalain'ceof signals. ap;- plied tofsaidftwo coilsreaches apredetermined magnitude; in. ain-rst direction andjto complete asecond; circuit when-said unbalancein signals reachesa predetermined magnitude inthe opposite directionandmeans .coupled tosaid relay and said drivereversing meansk for reversing the direction of said drive upon the completion of either circuit by said relay.

2. An electrical system as in claim l, said system further comprising an adjustable signal divider coupled between the rotor of said control transformer and said first and second phasesensitive detectors for controlling the magnitude of said scanning arc.

3. An electrical system as in claim 1, said system further comprising manually operated switch means for disabling said phase-sensitive detectors to cause said antenna to scan continuously in one direction.

4. 1n a motor driven scanning antenna system including means for reversing the drive of said motor in response to a change in signal applied thereto, an electrical system for causing said antenna to oscillate through a predetermined arc comprising a synchro transmitterv unit and a control transformer electrically coupled at their respective stator windings, said synchro unit having its rotor mechanically coupled to said antenna so as to rotate in synchronism therewith, means coupled to said control transformer for positioning the rotor thereof at a predetermined angle with respect to the stator thereof to select a reference point on said scanning arc, a differential relay having first and second coils, said relay being adapted to close a rst circuit in response to an unbalance of signals applied to said coils of a predetermined magnitude and a iirst direction of unbalance and to close a second circuit in response to an unbalance of signals of a predetermined magnitude and the opposite direction of unbalance, first and second phase-sensitive detectors electrically coupling the rotor of said control transformer to said rst and second coils, respectively, of said relay, the relative amplitudes of the signals applied to said first and second coils of said relay being a function of the phase and amplitude of the signal at the rotor of said control transformer, a two position, latch type relay coupled to said drive reversing means to control the operation thereof, said differential relay being coupled to said latch type relay to cause it to assume a first position upon completion of said first circuit and to cause it to assume a second position upon completion of said second circuit, said drive reversing means reversing the direction of the scan of said antenna each time said latch type relay changes position.

5. An electrical system as in claim 4, said system further comprising an adjustable signal divider coupled between the rotor of said control transformer and said rst and second phasesensitive detectors for controlling the magnitude of the scanning arc.

6. An electrical system as in claim 4, said system further comprising manually operated switch means for disabling said phase-sensitive detectors to cause said antenna to scan continuously in one direction, said latch type relay being connected to assume said first position upon the operation of said manually operated switch to disable said detectors.

7. In a motor driven scanning antenna system including means for reversing the drive of said motor in response to a change in signal applied thereto, an electrical system for causing said antenna to oscillate through a predetermined arc comprising a synchro transmitter and a control transformer, each having a rotor winding and stator windings, means electrically connecting together the respective stator windings of said synchro transmitter and said control transformery means mechanically coupling the rotor of said synchro transmitter to said antenna so as to rotate in synchronism therewith, means including an alternating current source for energizing the rotor Winding of said synchro transmitter, said control transformer being operative to produce at its rotor a single error signal having a phase and amplitude proportional to the angular diiference between the rotors of said synchro transmitter and said control `transformer, means coupled to said control transformer for mechanically positioning the motor thereof at a selected angle with respect to the stator to select a reference point on said scanning arc, a phase-sensitive detector including a pair of electron tubes, each having at least an anode, a cathode and a control grid, means coupling the anodes of said tubes to said alternating current source and arranged to apply inphase energizing potentials to said tubes, means coupling the rotor of said control transformer to the control grids of said tube for applying said error signal to said grids in phase-opposition, a differential relay having first and second coils connecte-din the anode circuits of said rst and second tubes, respectviely, said relay being arranged to close a first circuit in response to an unbalance of currents in said coils of a predetermined magnitude and a rst direction of unbalance and to close a second circuit in response to an unbalance of currents of said predetermined magnitude and the opposite direction of imbalance, the relative amplitudes of the currents in said first and second coils being proportional to the amplitude and phase of the signals respectively applied to the grids of said first and second tubes relative to the energizing potential of said anodes, and means operable by said relay for operating said reversing means.

8. Apparatus in accordance with claim 7 further comprising an adjustable signal divider coupled between the rotor of said control transformer and the control grids of said first and second tubes for controlling the magnitude of said scanning arc.

TED B, MORSE". JOHN F. YEAGER.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,998,939 Mittag Apr. 23, 1935 2,422,180 Broadhent June 17, 1947 2,499,228 Norden Feb. 28, 1950 2,538,027 Mozley et al Jan. 16, 1951 2,547,363 Bishop Apr. 3, 1951 2,605,453 Miller July 29, 1952

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