Fully digital cross polarization interference canceller for multilevel digital radio

Abstract

AbstractIn the digital radio system using dual polarizations, an interference canceller is needed that cancels excessive interference. In this paper, a fully digital cross‐polarization interference canceller is proposed in which digital signal processing (DSP) technology and LSI technology are applied. By means of DSP technology, the cancellation characteristics are determined mainly by the quantization accuracy and the number of taps. The only degradation factor is the rounding‐off error of the operations. High accuracy and large cancellation effects are expected. Also, an application of an advanced control algorithm is possible. Flexible applications are possible for any symbol rate. In this paper, the estimation method for the fully digital cross‐polarization interference canceller is presented. Based on this method, the relationships among the cancellation characteristics, the input signal quantization accuracy, tap coefficient quantization accuracy, and number of taps are analyzed theoretically for the case where the method is applied to the 256 QAM system. Next, the configuration of the canceller is presented. From the results of the experiments using the symbol rate of 12.5 MBaud and 256 QAM signals, good agreement with the theoretical prediction is obtained and, hence, the validity of the present estimation method is demonstrated. It is demonstrated that a high‐performance cross‐polarization interference canceller is realized which can be applied to a multilevel modulation system for a high‐speed region, such as 12.5 MBaud.