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

摘要

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 3.3 dB from 0.8 to 6GHz. Moreover, the LNA delivers two kinds of gain curves with ⅡP_3 of -2.6 dBm 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 200 kHz. The RF front-end also provides two kinds of gain curves. For the low-frequency mode, the conversion gain is 28.8～31.1 dB from 800 MHz to 2.4 GHz. For the high-frequency mode, the conversion gain is 26.8～27.4dB from 3 to 5 GHz. 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 200 kHz to 6.4 MHz while achieving an image rejection of 44dB.