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This paper presents a wideband blocker filtering technique for an RF front-end. A wideband LNA and a transferred impedance filter are implemented as part of a receiver to demonstrate the feasibility of the system. The transferred impedance filter includes an adjustable polyphase filter to compensate for the phase shift in the system in order to maintain correct operating frequency. The transferred impedance filter with passive mixers and the wideband LNA are analyzed by means of frequency transformation to demonstrate the different design trade-offs. The front-end achieves a gain of 43 and 41 dB and a noise figure of 3.2 and 5.7 dB with an IIP3 of -13 and -5 dBm with the transferred-impedance filter turned off and on, respectively. An added selectivity of 6 dB is achieved by using the solutions described in this paper.
Date of Publication: July 2012