For successful beam shaping and scanning in phased array radars, it is essential to precisely set the amplitude and phase
of each element channel. However, considerable amplitude and phase differences among the channels can occur due to
the different RF hardware connected to each element. Also, the phase and amplitude characteristics of most RF devices
depend on frequency and temperature and usually drift in time. In order to equalize the phase and amplitude effects of
the channels, phased array radars need to be calibrated periodically.
In the literature, various phased array calibration methods are discussed. However, the specifics of these methods are
usually not covered. Here, we describe four of the most commonly used calibration methods in detail: near-field
scanning probe, peripheral fixed probes, calibration lines, and mutual coupling. Each calibration method is described
step by step and relevant formulas are given. The advantages and disadvantages of each method are also discussed.