Post-Processing for Active Radar Two-Way Radiation Pattern Measurements

In modern integrated radar systems conventional antenna measurements are often impractical due to the lack of access to the antenna feed points. For frequency modulated continuous wave radars, the two-way radiation pattern can be characterized with a reflector while utilizing the integrated transmit and receive module. However, some post-processing steps are required for this measurement method to obtain the frequency-resolved radiation characteristic. This paper takes a closer look at the fast Fourier transform (FFT) and inverse FFT with the associated window functions and the necessary range gating including zero-padding based on simulations. A sufficiently wide range gating is necessary to reconstruct the frequency resolution of the antennas correctly. Yet a tradeoff between the required wide range and the filtering of mutual coupling and reflections from the environment has to be made in the case of real measurements. Moreover, depending on whether a frequency in the center or at the edge of the chirp is to be reconstructed, different window functions provide the most accurate result.