Enhancement of bandpass sampling efficiency in direct RF subsampling receivers: application to multiband GPS subsampling receiver

In this paper, a new method is proposed to enhance the efficiency of band-pass subsampling for multi-band RF signals in order to relax design specifications for Software Defined Radio receivers. Hence, analytical formulations are defined to calculate the minimum valid sub-sampling frequency by adding specific guard bands around RF signal bands in order to overcome implementation imperfections and reduce aliasing caused by different noises. Upper and lower guard bands are derived from the specifications of the band-pass anti-aliasing filter implemented before sampling in order to restrict bandwidth and achieve image rejection. The proposed method was validated for the case of a multiband L1/L2/L5 GPS subsampling receiver. ADS simulation results showed valid design with 121.3088 MHz of subsampling frequency and third order anti-aliasing RF filter.