RF Front-End and Complex BPF for Reconfigurable Low-IF Receiver

概要

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A LNA, an RF front-end and a 6th-order complex BPF for reconfigurable low-IF receivers are demonstrated in this work. Due to the noise cancellation, the two-stage LNA presents a low NF of 2.8 to 3.3dB from 0.8 to 6GHz. Moreover, the LNA delivers two kinds of gain curves with IIP3 of -2.6dBm by employing the capacitive degeneration and the resistive gain-curve shaping in the second stage. The flicker noise corner frequency of the down-converter has been considered and the measured fC of the RF front-end is 200kHz. The RF front-end also provides two kinds of gain curves. For the low-frequency mode, the conversion gain is 28.8∼31.1dB from 800MHz to 2.4GHz. For the high-frequency mode, the conversion gain is 26.8∼27.4dB from 3 to 5GHz. The complex BPF is realized with gm-C LPFs by shifting the low-pass frequency response. With variable transconductances and capacitors, a fixed ratio of the centre frequency to the bandwidth (∼2) is achieved by varying the bandwidth and the centre frequency of the LPF simultaneously. The complex BPF has a variable bandwidth from 200kHz to 6.4MHz while achieving an image rejection of 44dB.