Cw radar

CW radars have a very big advantage — very low peak power. As the transmitted power can be below 1 W (many of them work with 1 mW power), they belong to the low probability of intercept (LPI) class of radars, which can detect targets while they remain undetected. 

K. Kulpa, Adaptive Clutter Rejection in Bi-static CW Radar , International Radar Symposium 2004 19-21 Maj, Warszawa Polska, pp. 61-68. 

This is known as frequency modulation and is used on the second type of radar, Continuous Wave or CW radar (Ref 1)... 

Several methods have been proposed to nonintrusively measure the thicknesses of walls, corrosion profiles, and macrodefects [i.e., 49], Two methods at room temperature that require point contact with the cold face of the furnace are known. The first is impact-echo method, used in construction concretes and pavements (Sect. 1.4). The second method is the frequency-modulated continuous-wave (FM-CW) radar technique [50], which can produce wall thickness data in real time. 

In practice CW radar is much more complicated. A CW radar transmits while it receives. It compares the frequency of the transmitted signal with the frequency of the received signal. A precondition for the measurement is that the transmitted frequency changes over time, which is usually done by a ramp-form linear modulation with a slope of m=df/dt. When the received signal returns after the flight time tflight=2 2/c, the transmitted frequency has changed by, = Thus,... 

The over-all system configuration is presented in Section 7.3.1. In Sections 7.3.2, 7.3.3, and 7.3,4, we consider applications of the system to a cw radar with sinewave, Gaussian/Gaussian, and Gaussian/Lorentzian input signals, respectively. Section 7.3.5 deals with its use in an analog communications system, whereas Section 7.3.6 is concerned with low-frequency applications of the technique. A numerical example in Section 7.3.7 is followed by evaluations of system performance for binary communications and pulsed radar in the vacuum channel (Sec, 7.3.8) and in the lognormal atmospheric channel (Sec. 7.3.9). A discussion is presented in Section 7.3.10. The main results are expressed as the output SNR for the system in terms of the input SNR. 

Application to cw Radar with Sinewave Input Signals... 

The previous subsections were primarily concerned with the behavior of the three-frequency nonlinear heterodyne system for applications in cw radar and analog communications. As such, a determination of the output signal-to-noise ratio (SNR)o was adequate to characterize the system. In this subsection, we investigate applications in digital communications and pulsed radar, and therefore examine system performance in terms of the error probability P. Evaluation of the probability of error under various conditions requires a decision criterion as well as a knowledge of the signal statistics we now investigate operation of the three-frequency nonlinear heterodyne scheme in the time domain rather than in the frequency domain. 

Modulated Continuous Wave (FM CW) Radar, TransNav, the International Journal of Marine Navigation and Safety of Sea Transportation, Vol. 3, N3, Sept. 2009, pp. 311-314. 

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