Array Excitation Error Calibration

The objective of phased array antenna calibration is to sample each antenna element in the array, and compare the obtained results to identify the differences among the elements. Phased array calibration for both transmit and receive are similar, the primary difference lies in the test-signal distribution at the input and the combination at the output. For receive calibration, a calibration source and/or a distribution network is required to inject the test signal into the input of each element, the array beamformer can be used as a test signal combiner. For transmit calibration, it requires a calibration source signal into each element and additional equipment or beam combiner for combined signal monitoring. Only receive calibration is presented here to keep the discussion focused, the extension for transmit calibration is straightforward. The calibration methods vary from different systems and applications, either suitable for factory test or for in-field test. These calibration methods can be generally divided into four main categories, i.e., the near-field scanning probe method, the peripheral fixed probe method, the mutual coupling method, and the built-in network method. The advantages and challenges of these calibration methods are shortly summarized in Table 4.1 and presented in the following subsections.