GB1285053A - Improvements in or relating to radars - Google Patents

Abstract

1285053 Monopulse radar MARCONI CO Ltd 26 Nov 1969 [17 April 1969] 19601/69 Heading H4D A monopulse radar has an auxiliary waveguide located centrally of the radiating horns or waveguides of the static split aerial system for injecting auxiliary signals, of the same frequency as the radar operating frequency into the aerial receiving channels, which signals represent a target situated on the mechanical axis of the aerial and also has means for using the signals produced by the radar in response to the auxiliary signals, as error correcting signals when receiving echoes from a target. In a normal monopulse radar system the four signals from a square cluster of elements in the aerial 1 are combined by hybrid system 4 to produce a sum and azimuth and elevation difference signals. These signals are fed to receiver 6 where they are converted to I.F. The I.F. signals are then passed to three amplifiers 51, 71, 81 which are gain controlled by a voltage dependent on the detected amplitude of the sum signal. The difference signals are then compared to the sum signal in two phase sensitive detectors 10, 11. The auxiliary signals are injected into the radar from a waveguide (W) connected to the output of a variable h.f. source 12, which may be part of the radar transmitter 2. A switch 13 causes the signals to be injected and also operates a magnetic tape or other recorder 14 which records the outputs from the two PSD's due to the injected signals. These values are then fed into two subtractors 15, 16 the other inputs to which are the P.S.D. outputs. When echoes from a target are received, they are processed normally and the outputs from the subtractors 15, 16 are thus corrected by the error signals from the recorder. The subtractor outputs are used to control the aerial to track the target or are fed to a display. The use of this system allows different errors e.g. due to using different operating frequencies and ageing of components or temperature effects to be allowed for. If a four horn aerial is used the auxiliary signals are injected through coupling holes in the four horns (H) and in the waveguide (W) positioned centrally of the cluster (Fig. 2, not shown). If a two element aerial is used the coupling holes are arranged to be in the parallel sided sections of the horns (Fig. 3, not shown) or in the waveguide feeders to the horns (Fig. 4, not shown) not in the flared portions.