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Hsiao-Chin CHEN Shu-Wei CHANG Bo-Rong TU
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 6 GHz. Moreover, the LNA delivers two kinds of gain curves with IIP3 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 28.831.1 dB from 800 MHz to 2.4 GHz. For the high-frequency mode, the conversion gain is 26.827.4 dB 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 44 dB.