From Radar Design Principles: Signal Processing and the Environment, Second Edition

Overview

The continuous wave (CW) radar is frequently used for detection and tracking of moving targets. [1] In its simplest form a single sinusoid is transmitted, and the received signals are mixed with the transmitted carrier frequency. The existence of moving targets is determined from the beat note or Doppler frequency shift f d.

(10.1)

where v is the radial velocity difference between the target and the radar (positive for closing geometries) and ? is the carrier wavelength. The advantage of this technique is its simplicity.

As with virtually all radar waveforms, the angle of arrival of the target echoes can be determined with multiple receive apertures or with monopulse receivers. On the other hand, there is no target-range determination or resolution except with special geometries that occur with lunar or planetary observation radars. If range resolution is required, the transmit waveform must be modulated. Frequency modulation is discussed in Sec. 10.2 and Chap. 13, and binary-phase modulation is discussed in Chap. 12.

Since the CW receiver responds to echoes from all ranges, it is generally necessary to separate the leakage or spillover from the transmitter and signals from close-in clutter. This is usually accomplished by filtering out received signals at the carrier frequency and at the Doppler frequency of the clutter. An alternate technique is to pulse the transmitter at a rate higher than twice the expected Doppler frequency. This technique is called interrupted CW or ICW to distinguish it from pulse...


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Topics of Interest

11.1 Terminology and General Assumptions It is now generally accepted that the use of a pulse-train waveform is virtually a necessity to detect small airborne targets in a land clutter background.

Overview The fundamental problems and different aspects of the detection of moving radar targets have long been treated by many authors. We will discuss here those aspects which are especially...

Chapter List Chapter 10: Pulse-Doppler Radar Chapter 11: Observation of Moving Targets by an Airborne Radar A doppler radar is defined by [1] as a radar which uses the doppler effect to determine...

8.4 DOPPLER MEASUREMENT Measurement of target doppler is directly analogous to range measurement, with time and frequency functions interchanged. In doppler measurement, however, two time and...

Chapter List Chapter 22: Sources and Spectra of Ground Return Chapter 23: Effect of Range and Doppler Ambiguities on Ground Clutter Chapter 24: Separating Ground-Moving Targets from Clutter Part...

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