A Compensation Method for Quadrature Modulation

摘要

Two methods of modulation, quadrature and amplitude-phase, are being considered for the near-term implementation of clutter or extended targets. A test of quadrature modulation has been made with fairly good results (44 dB suppression for single-sided Gaussian spectrum), but manual adjustments were required which are operationally impractical for the 32 modulators of the system. Amplitude-phase modulation has not yet been tested; however, some form of compensation will be required, and it is likely to be complicated, based on the experience with the array pointing attenuators and phase shifters. Tests of amplitude-phase modulation are required to determine the complexity of the compensation. Because of the encouraging results with quadrature modulation, it would be desirable to pursue the investigation further with this modulation scheme. Towards this end we present a relatively simple compensation method for quadrature modulation which, based on a postulated error model, improves the sidelobe suppression, removes the necessity of frequent manual adjustments, and is amendable to non-real time automatic calibration. A test of the compensation method is required to determine the actual degree of improvement and the complexity of the compensation. We show that such a test can be carried out using presently available hardware. It is recommended that such a test be conducted. (Author)