12.02.2014 Views

Radar System Engineering

Radar System Engineering

Radar System Engineering

SHOW MORE
SHOW LESS

You also want an ePaper? Increase the reach of your titles

YUMPU automatically turns print PDFs into web optimized ePapers that Google loves.

664 MOVING-TARGET INDICATION [SEC. 16.16<br />

the doppler frequency at 10 cm will vary from plus to minus 3500 cps.<br />

The way in which this frequency is added to the reference signal is shown<br />

in the diagram. The doppler oscillator receives a shaft rotation and<br />

+250<br />

*<br />

H+100<br />

IGate Reference<br />

signal<br />

r-c)<br />

-—— ---<br />

Lli!<br />

* =looo##f<br />

=<br />

Fm. 16.27.—A typical 30-Mc /see coherent oscillator circuit.<br />

delivers a linearly related frequency with an absolute accuracy of 2 cps.<br />

This oscillator is similar to the General Radio Type 617-c Interpolation<br />

Oscillator. The single sideband rejection requirements for the carrier<br />

and unwanted sideband are very severe. The quartz filter was designed<br />

Doppler<br />

oscillator - Mixer<br />

63-70 kc /SeC<br />

Quartz<br />

From<br />

bandpass filter<br />

30 Me/see<br />

Mixer<br />

“ 6496.;; fe;03.5 + coherent<br />

L<br />

oscillator<br />

I t t<br />

Navigating Fixed + L.C Im&pass<br />

;~~ ~etin<br />

oscillator<br />

Mixer<br />

n%<br />

circuits<br />

6433.5 kc/see<br />

1<br />

23,49~~6.~&%3.5<br />

t 1<br />

Fixed .Shgle.side L G b#MSS<br />

oscillator + Mixer - band filter<br />

29,9W:F3.5<br />

66.5 kc/aec 6500 kc/see<br />

To MTI<br />

receiver<br />

FIG, 16.28.—Block diagram of a phase-shift unit.<br />

by Bell Telephone Laboratories. Pending delivery of the latter, the<br />

circuit was tested by means of LC-filters with one additional mixing<br />

step, and found to cancel target motion satisfactorily. The absolute<br />

accuracy of the circuit from the shaft of the doppler oscillator is about

Hooray! Your file is uploaded and ready to be published.

Saved successfully!

Ooh no, something went wrong!