Patent GB-1029656-A (GB)
Title: Improvements relating to radar systems
Inventor: HERSCH WOLFGANG
IPC: H01Q3/42
Filed: 1961-08-03
Abstract: 1,029,656. Radar ; aerials. ELECTRICAL & MUSICAL INDUSTRIES Ltd. Aug. 3, 1962 [Aug. 3, 1961], No. 28321/61. Headings H4A and H4D. In radar apparatus wherein radio frequency signals are fed to the elements of an aerial array, with such relative phase shifts as to produce a directed beam of radiation therefrom and signals received by the elements fed via frequency changing means to selected tapping points on receiver delay means, from whence they are fed selectively to two radio receivers, the frequency changing means on the tapping points or the delay means are arranged to give the effect of splitting the beam in one plane about the direction of the directed beam. The above arrangement may be duplicated for a second array of elements, interleaved with the first, the second array being slightly inclined to the first array to produce the equivalent of a second splitting of the beam in a plane perpendicular to the said one plane. The two aerial arrays A and B (not shown) may each comprise two vertical columns of elements fed from tappings on respective transmission lines, such that alteration of the frequency ft of the signal fed to the said transmission lines alters the phase difference between adjacent elements in each column and thus alters the resulting beam in elevation. The said signal is produced by generator 1 and fed via circulators 6 and 7 and connections A1 and A2 to the transmission lines of aerial array A, and via circulators 8 and 9 and connections B1 and B2 to the transmission lines of array B. Scanning of the beam in azimuth is produced by introducing phase shifters 2, 3, 4 and 5 in the feeds to the transmission lines, the azimuthal deflection of the beam from array A being made equal to that of the beam from array B. The transmitting beam is therefore scanned in elevation and azimuth and split in elevation, whilst the receiving beam is split in elevation and scanned in elevation due to the frequency variation of the received signals, azimuthal scanning of the receiving beam being effected as described below. The received signals at frequency ft from circulators 6 and 7 are each divided into two equal positions and mixed in mixes MA11/MA12 and MA21/MA22 with respective signals of frequency F LO1 /F LO2  where F LO1  = ft + fi + fa - #fa F LO2  = ft +fi + fa + #fa fi = intermediate frequency. fa = frequency equivalent of azimuth posi tion of transmitting beam as explained below. This frequency is produced by a generator coupled with phase shifters 2, 3, 4 and 5. #fa = frequency equivalent of half of required azimuth splitting of receiving beam. The resulting difference frequencies from mixers MA11 and MA21 are applied to tapped points on a delay line 15 arranged to work at the frequency fi, the tapping points being so chosen in relation to frequency fa that the azimuth position of the portion of the receiving beam thus detected is the same as that of the transmitting beam. Similarly, the outputs from mixers MA12 and MA22 are fed to tapped points on delay line 16. The output from delay line 15 is equivalent to that received by the beam of array A in an azimuth position equivalent to (fa - #fa) whilst that from delay line 16 is equivalent to a receiving beam position frequency of (fa + #fa). The signals received by array B are similarly processed in mixers MB11, MB12, MB21, MB22 and delay lines 17 and 18. Four receiver channels are thus provided: RX1, RX2, RX3 and RX4, corresponding to four separate receiving beams, the elevation split of the beam being determined by the difference in the inclination of the columns of the radiators of the two arrays and the azimuth split being determined by the frequency 2#fa. #fa may be made a function of the bearing angle determined by frequency fa. In another embodiment each mixer pair MA11/MA12 &c. may be replaced by a single mixer which is fed with a signal of frequency f LO  = ft + fi + fa, the tappings on delay lines 15 and 17 however now differing from those on lines 16 and 18 to provide the same effect in the receiver channels as the difference frequency 2#fa. Variable delay lines may then be incorporated into lines 15 and 17 to produce the equivalent of adjusting the value of #fa in accordance with the above-mentioned function of the bearing angle. In a third embodiment only one delay line and one mixer per array are used, F LO1  and F LO2  being both applied to each mixer with the value of fi different for F LO1  and F LO 2, the two intermediate frequency signals being separated out by filler means at the ends of the delay lines. The relative strengths of the signals in the four receiver channels indicates the special direction of the beam.