Design of a low-power tunable low-pass filter with highly linear Gm-C cell for a multi-mode transceiver

Abstract

This thesis presents a low-power tunable low-pass filter for a multi-mode transceiver. Customer demands for an application which supports multi-modes. For example, the smartphones support WLAN, Bluetooth, GPS as well as WCDMA in the same terminal. For multi-operation, each component in the transceiver should support the multi-mode operation. The low-pass filter operates as baseband selection in a transceiver. By varying the cut-off frequency of the low-pass filter, it supports the multi-mode operation. The transconductance amplifier is a basic building block of low-pass filter. The transconductance amplifier dominates the total linearity characteristic in low-pass filter. However, as device size and supply voltage are scaled down, the low-pass filter is getting difficult to guarantee the required linearity. Therefore, the linearity improvement techniques of the transconductance amplifier has been developed. In this work, the filter uses the cascades of two $G_m-C$ biquad cells including the transconductance amplfier. The design of the transconductance amplifier is based on the $g_{m3}$ cancellation technique for linearity improvement. The tunability of this filter is realized by using a capacitor array. The filter cut-off frequency tuning range is from 2MHz to 16.6MHz for the WCDMA(UMTS) and WLAN 802.11 a/j/n. The in-band IIP3 of the filter is 16.32 dBm. The filter is fabricated in a 0.13 μm 1P8M CMOS process, the chip area is 0.43 $mm^{2}$, and the power consumption is 1.69 mW with a 1.2 V supply power.