RF-FPGAs and field-programmable filter arrays require tunable analog filters that can be digitally reconfigured in real-time to have several user-selected passbands and stopband notches. Such reconfigurable analog filters must operate in the microwave frequencies up to several GHz in order to meet the needs of emerging cognitive radio and reconfigurable radar front-ends. Tunable passive filters based on RF-MEMS, surface acoustic wave- and planar-technologies have been explored in the recent past to achieve this goal. In this paper, a novel RF-IC approach to design microwave filterbanks having multiple bands, each having independently tunable center frequency and quality factors, is proposed. The proposed technique is based on transfer function synthesis using first-order all-pass filters as a building block. Using measured data from a current-mode 130-nm CMOS allpass filter implementation, the feasibility of multi-band tunable filter arrays is simulated with a tuning range of 4 GHz.
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