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AP3302 Pt3 Contents

AP3302 Pt3 Section 1 Contents

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AP 3302 Pt. 3

Section 1

CHAPTER 4

Some examples of the uses of pulsed radar

Volumetric (3-D) Radar

A reduction in the number of radars required can be obtained with a volumetric (3-D) radar system which uses a stacked beam principle to provide height as well as plan position information for each aerial revolution. Parameters for a typical system are:

 

Wavelength

10 cm (S band)

 

Frequency

3 GHz

 

Peak power

3 MW

(shared among 12 separate beams)

Pulse duration

10 us

(using pulse compression-see p 617)

PRF

320 p.p.s.

 

Slant range

220 nm

 

Height

up to 100,000 feet.

 

 The aerial consists of a reflector and a feed arrangement to produce a stacked beam system. The reflector is parabolic in both dimensions and measures 40 feet (12 m) across by 15 feet (4.6 m) high. When operating as a transmitter, the transmitter power is divided in the feed system to produce 12 separate beams, as shown in Fig 6 (this is an idealised drawing). The half-power beamwidths are typically 0.6o horizontally and 1.25o vertically and the aerial has a gain of 44 db.

The aerial is rotated in azimuth at a rotation rate of 5 revs per minute, so that all twelve beams are rotated to give the cover shown. Completely gap-free cover up to a range of 220 nm and at heights up to 100,000 feet (to an elevation angle of 30o) is obtained.

When receiving, the echo power in each beam is applied to its own receiver and by comparing the output of each receiver in a computer, information on range, bearing and elevation (height) of each target is obtained for application to the display. All this information is up-dated on each rotation of the aerial. For targets at a range of about 100 nm and at heights of 40,000 feet, the following performance figures are given:

Height accuracy

better than 1,500 feet

Range accuracy

100 metres

Azimuth bearing accuracy

0.2o

Range discrimination

better than 100 metres

Angular discrimination

better than 0.8o (at low angles of elevation).


 

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ęCopyright 2000 - 2002 Dick Barrett

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