Patent GB-1278419-A (GB)
Title: Improvements in or relating to radar systems
Inventor: DAVIES ERIC
IPC: G01S13/42
Filed: 1968-12-06
Abstract: 1278419 Pulse radar MARCONI CO Ltd 2 Sept 1969 [6 Dec 1968] 58010/68 Heading H4D Relates to within-pulse scanning radar systems, i.e. within the period t of the transmitted pulse (which is emitted omnidirectionally) a sector is explored directionally by the receiving apparatus which quantizes range and azimuth. In a system not according to the invention receiving horns H1 ... H61, Fig. 1, each have a radiation pattern covering at least the azimuthal sector and feeds into a frequency changer consisting of a receiver proper R1 ... R61 and a local oscillator O1 ... O61, the local oscillation frequencies being: The outputs from the frequency changers are fed via I.F. amplifiers A1 ... A61 each of bandwidth approximating 1/t. The outputs of the I.F. amplifiers are combined and fed to a phase detector PD into which is fed frequency F from a source FR of reference frequency and phase. All the local oscillators, all the intermediate frequencies and the reference frequency are coherent as also are the transmitted carrier and the pulse repetition frequency 1/T. The phase detector feeds into a number of " boxcar " filters BC each containing switches SW1, SW2 actuated simultaneously, a filter BPF to exclude low Doppler shifts due to clutter, a rectifier RT and an integrator IC. The boxcar filter outputs are taken to a display tube U, the pairs of switches being actuated sequentially; the display is type B with a rectilinear raster of line frequency 1/t and frame frequency 1/T. If there are n range zones and m azimuth zones, there must be mn box-car filters. The invention seeks to reduce the apparatus following phase detector PD and in accordance therewith target-representative signals are stored individually, stored signals corresponding to targets in different range zones but all in one azimuth quantum are read off sequentially, stored signals corersponding to targets in different range zones but all in another azimuth quantum are read off sequentially ... and so on until all stored signals are read off, the readoff signals being utilized and/or displayed to provide quantized range-azimuth target information. The storage read out may be performed by a signal writing cathode-ray tube (C.R.T.) and a single reading C.R.T., magnetic tape means, or by storage diodes; but in the preferred embodiment the output of the phase detector PD, Fig. 3, intensity-modulates in parallel the beams of C.R.T.s CR1, CR2 which are scanned according to a raster pattern covering equal line and blanked line flyback segments progressing down the first of y adjacent columns, then the second column and so on, each vertical column accommodating x of the total n range zones, where T = 2txy. (The raster pattern is conveniently summarized in a table in the Specification). The necessary line and frame deflection waveforms are generated from a master timing unit MTU, see also Fig. 4 (not shown). The optical outputs are imaged on to corresponding charge-storage tubes KT1, KT2 which are scanned such that output signals when applied to a display C.R.T. 26 will afford a sector P.P.I, and involves scanning line direction perpendicular to that in tubes CR1, CR2, Fig. 5 (not shown). The signals are applied to C.R.T. 26 via a filter 23 which excludes targets producing a Doppler-shift below 10 c/s., a rectifier 24 and an integrator 25 with a time constant preferably t.