A CMOS gm-C Low-Pass Filter for Direct Conversion Receivers with Tuning Capability

This work presents a third order Butterworth low-pass filter with a tunable capability that serves different wireless technologies such as Bluetooth, cdma-2000, wideband CDMA and IEEE 802.11 a/b/g/n. Hence, it is suitable for multi-mode direct conversion receivers. The filter is implemented using a gm-c topology. The gm-cell converts voltage to current using a triode region MOSFET device while a current-multiplier circuitry widens the tuning range and enhances linearity. By implementing a programmable capacitor array, the filter can operate over a cutoff frequency range of 200KHz to 40MHz. The filter was designed using 28nm CMOS process technology. It consumes 0.803mW to 1.04mW of power for minimum and maximum cutoff frequencies using a 1V supply voltage. It exhibits input referred noise (190-770)nV/√(Hz) at room temperature with acceptable linearity of 9.89dBm to 22.3dBm for minimum and maximum IIP
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