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Both S713 and S723 use similar multi-beam signal processing, figure 11. The processor applies moving target indication (m.t.i.) and non-coherent processing to each of the beams produced by the b.f.n. Each beam is subject to a single filter which is set to give a triple canceller response. This is followed by a time-sidelobe removal system and a choice of thresholds-thermal, temporal or fast acting constant false alarm (c.f.a.r.). Normally, the threshold used is either 'thermal' (in clear conditions) or 'temporal' (in clutter), but when jamming is present, the fast-acting c.f.a.r. facility is switched in,

Additionally, there is a non-coherent processing channel for each beam, working on digital log video, with the same form of time-sidelobe removal and thresholding.

Each channel has an output (derived from its temporal estimator) to indicate the presence of clutter, and a full-amplitude output taken from either the m.t.i. or non-coherent channel before time-sidelobe removal and thresholding. The threshold outputs from both channels of all beams are combined to give a composite 'black and white' video output to a plot forming unit.

When a target is detected, depending on whether the detection is in an m.t.i. or non-coherent channel and whether or not clutter is present, a decision is made automatically on whether the full amplitude outputs of all beams are taken from the m.t.i. or from the non-coherent channels, and the selected information is passed to the plot forming unit for elevation extraction,


In addition to the essential elements of frequency synthesis, transmitter drive, transmitter, receiving and signal processing chains, the S713 and S723 systems also include a display known as the Radar Management Position. figure 12. It presents the Radar Manager with complete data on the radar operating characteristics both functionally and positionally within the cover and enables him to select the most appropriate modes.

The radar signals and plot outputs are presented on a conventional p.p.i. display and equipment status and control indications on a TV monitor. The latter incorporates a Digilux touch-mask man-machine interface which enables the Radar Manager to control the radar and select data for display via the Management Processor.


The design of transportable electronic equipment for pan-climatic operation is an established capability within the Company, built up from some 40 years experience of supplying radars to the Services. Even so, large rugged planar arrays presented a new challenge.

For the S713, the array is 20 feet wide by 35 feet high and has 60 rows of 32 dipoles: the S723 is 40 feet wide by 24 feet high and has 40 rows of 64 dipoles. Thus in both cases some two thousand dipoles have to be positioned accurately. They must be located within a dimensional tolerance of a few millimetres over the whole surface to guarantee radar performance and must maintain their relative positions in the face of winds of 100 miles per hour and survive without permanent distortion in gusts up to 150 m.p.h.


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Updated 06/11/2001

Constructed by Dick Barrett

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ęCopyright 2000 - 2002 Dick Barrett

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