Patent GB-1443885-A (GB)
Title: Radar system with brightness and resolution
Inventor: GROSS FRITZ A
IPC: G01S7/06
Filed: 1974-10-21
Abstract: 1443885 Pulse radar RAYTHEON CO 21 Oct 1974 [5 Nov 1973] 45466/74 Heading H4D A variable range radar system comprises means for converting radar returns into digital samples, writing means operative to write the samples into digital storage means, and reading means operative to read out the stored samples to display means at a rate which is lower than the writing rate for at least some range settings of the system. At short radar range settings a considerable improvement in display brightness is obtained, since the read out may be extended up to the whole of the normal scan period of the display. The storage means may make use of a random access memory or a plurality of shift registers. In an embodiment, transmission is initiated by a pulse generator 216, Fig. 1, which is coupled to a magnetron 212 via a modulator 215 and a transformer 214. Output from the magnetron is coupled through a duplexer 210 to an aerial 208. Received radar return signals are fed from the aerial through the duplexer as one input of a mixer 226, which has another input from a klystron 222. Output from the mixer at I.F. is coupled via an amplifier 224 to a radar video digital processor 230. The aerial and associated apparatus are rotatable by a motor 220, and may be mounted on a mast of a ship. A heading line switch 206 produces a pulse output each time the aerial is pointing in the same direction as the ship. This pulse provides a marker on the display, for the information of the operator. The processor 230 is contained in an indicator unit 109, and, in addition to the video signal input from the amplifier 224, it receives inputs from the pulse generator 216, a clock generator 228, and a range switch 232. The processor converts the incoming radar return signals to digital form, stores them and, after reception has been completed for one radar return time, reads them back to a CRT display unit 233. The write-in rate is determined by the setting of the switch 232 and may be, for at least some settings, inversely proportional to range. The read-out rate may be, for at least some settings, constant. After being read out of storage within the processor 230, the radar return signals are reconverted to analogue form and are coupled via an amplifier 236 to the cathode of a CRT 246. The beam of the CRT 246 is deflected by coils 248, which are connected to a deflection amplifier 234, and which are rotated around the neck of the tube by a motor 246, coupled through clutch and latch 244. The pulse from the heading line switch 206 is used to synchronize the motor 242 with the direction in which the aerial 208 is headed. The output of a generator 235 constitutes deflection waveforms which are fed to the amplifier 234. The said generator is controlled by an output on a line 260 from the processor 260. Circuitry for the radar video processor is described with reference to Figs. 3A, 3B, (not shown). The incoming video signals are first converted to digital form, and use is made of a plurality of banks of shift registers for their storage and read-in and read-out at rates determined by the settings of the range switch 232. The outputs from the shift registers in the final bank are combined, and are then converted to analogue form for application to the video amplifier 236.