A varactor based tunable RF filter for multistandard wireless communication receivers

This paper presents the design of a tunable RF filter dedicated for multistandard operation in Software Defined Radio (SDR) receivers. This filter is based on the Dual-Behaviour Resonators (DBR) topology realized in microstrip technology with PTFE substrate and using SMV1405 varactors as tuning elements. It provides the independent control of its center frequency and bandwidth relative to the radio standards UMTS, Wi-Fi and LTE (Band N°7). The center frequency ranges from 2.142 to 2.65 GHz and the required bandwidth varies from 86 to 108 MHz. S-parameters simulations and measurements with non-linearity study are provided to evaluate the performance of the designed filter. A very good agreement between simulations and measurements is obtained and the designed filter shows acceptable performances in terms of insertion and return losses which are less than 6 dB and more than 14 dB, respectively for all bands. Moreover, linear properties regarding receiver requirements with a minimum 1-dB compression point (P1dB) of 11.4 dBm and a minimum third order intercept point (IP3) of 21.2 dBm are satisfying.