Design of an integrated RF filter for the direct digitization front end of a dual GPS/GLONASS software radio receiver

A software radio can be defined as a receiver implementation in which the analog-to-digital (ADC) converter is positioned as close to the antenna as possible, so that the resulting samples can be processed using a programmable microprocessor. Compared to the conventional superheterodyne implementation, this direct digitization front-end eliminates additional components used for frequency translation. A key component of such a front-end is the RF filter which facilitates band-pass sampling of the incoming signal. In this paper, we present the design of a wide-band integrated filter which passes both the GPS and GLONASS satellite bands using a minimum number of analog components. The filter is realized on a microstrip and simulated to test the baseband specifications and signal integrity.