A N T E N N A. CW Radar I E O T R Y & D E. Lecture 21. DR Sanjeev Kumar Mishra G N

Transcription

1 CW adar Lecture 21 anjeev Kumar Mishra

2 Based on ntenna type Based on frequency band adar classification Based on waveform utilized Based on mission and/or functionality of the adar round Based irborne paceborne hipborne Phased rray F VF UF L - Band - Band C - Band X - Band Ku - Band K - Band Ka - Band mmw Continuous Wave (CW) Pulse adar (P) Low PF Medium PF igh PF Weather cquisition earch racking rack while -can Fire control arly warning ver the horizon errain following errain avoidance Mono static Bi - static maging on-maging

3 ntroduction Continuous Wave ransmission Pulse ransmission.

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5 CW ransmission ransmitter CW F scillator ntenna U iscriminator MP Mixer ndicator ntenna

6 Monostatic CW witching ime ransmitter Leakage the maximum amount of power enter into the receiver input circuitry the amount of transmitter noise enters into the receiver: reduces the receiver sensitivity hus Proper isolation is required.

7 (a) infinite duration and Frequency spectrum of CW oscillation (b) finite duration

8 Bi-static CW

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10 oppler filter bank: he effective radar oppler bandwidth is FF f/2. FF is the oppler filter bank size and f is the individual BF bandwidth (FF bin), hus, he reason for the one-half factor is to account for both negative and positive oppler shifts. ince the BF bank is implemented by an FF, only finite length data sets can be processed at a time. he length of such blocks is normally referred to as the dwell time or dwell interval. t is also known as ime on arget ( i )

11 CW quation he dwell interval ( well ) determines the frequency resolution or the bandwidth of the individual BFs. More precisely, 1 f well i herefore, once the maximum resolvable frequency by the BF bank is chosen the size of the BF bank is computed as FF 2 B f FF well 2 o B k FL P av f 2B i FF he CW radar equation can now be derived from the high PF radar equation given

12 he CW radar equation can now be derived from the high PF radar equation given k FL o n the case of CW radars, P av is replaced by the CW average transmitted power over the dwell interval P CW, and i must be replaced by well. hus CW adar equation will be t r o P av k FLL Where, t and r and are the transmit and receive antenna gains, respectively. he factor L win is a loss term associated with the type of window (weighting) used in computing the FF. i win P CW well

13 ign of the radial velocity f the echo frequency is greater than the carrier, the target is approaching f the echo-signal frequency lies below the carrier, the target is receding; (a) o doppler shift, no relative target motion; b) approaching target; c) receding target. pectra of received signals.

14 CW pplications Un-modulated CW radar is for the measurement of the relative velocity of a moving target, as in the police speed monitor or in the previously mentioned rate-of-climb meter for vertical-take-off aircraft. n support of automobile traffic, CW radar has been suggested for the control of traffic lights, regulation of toll booths, vehicle counting, as a speedometer in vehicle testing, as a sensor in antilock braking systems, and for collision avoidance. For railways, CW radar can be used as a speedometer to replace the conventional axle-driven tachometer. CW radar is also employed for monitoring the docking speed of large ships. t has also seen application for intruder alarms and for the measurement of the velocity of missiles, ammunition, and baseballs.

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