Research on Passive Polarization Calibration Methods for Insect Radars in Non-Ideal Environments

Most current insect radars use a fully polarimetric system that measures polarization information to determine biological parameters such as the insect's head orientation, body length, and weight. Amplitude and phase inconsistencies between the polarization channels in radar systems, along with cross-polarization interference from dual-polarized antennas, can introduce polarization errors. These errors distort the radar's polarization data, leading to significant inaccuracies in the derived insect parameters. Additionally, insect radars are often deployed in complex outdoor environments where fluctuating factors such as temperature and humidity cause time-varying polarization errors, making it challenging to calibrate these errors accurately. Polarization calibration techniques are designed to estimate and correct these system errors, forming the foundation for obtaining accurate polarization information from radar. This paper aims to analyze the performance of existing polarization calibration methods under conditions of time-varying polarization errors. First, the sources of polarization errors, the concept of polarization calibration, and its classifications are introduced. Next, the system error model for polarimetric scattering matrix (PSM) measurements is analyzed, and several typical passive polarization calibration methods are presented. Then, a qualitative analysis of the time-varying effects of system polarization errors is conducted using measured data, and a comparative analysis of the performance of typical passive polarization calibration methods under these conditions is provided through simulation experiments. Finally, the applicability of existing polarization calibration methods to current insect radars is discussed.