How to apply the CA-CFAR methods in practice?
Constant false alarm rate detection is more of a general technique that underlies a class of approaches; you can't really say that there's "an" implementation of CFAR processing. CFAR techniques are useful when you need to detect the presence of a signal where there is some uncertainty as to what the magnitude of the signal will be, especially relative to any background noise or interference. The general principle of constant false alarm rate detection is that the detector makes some effort to estimate the background level and set a detection threshold adaptively relative to the observed ambient environment. This approach makes the performance of the detector (typically measured quantitatively using the probability of detection $P_d$ and probability of false alarm $P_{fa}$) insensitive to the bulk magnitude of the signal under observation; only relative changes in the statistics of the signal over time (such as a transition from noise only to signal-of-interest plus noise) are important.