A tunable-Q 4-path bandpass filter with Gm-C second-order baseband impedances

An active switched-capacitor 4-path bandpass filter suitable for multi-standard applications in ultra-high frequency (UHF) band with different channel bandwidths is designed and simulated in 0.18 µm CMOS technology. The baseband impedance of the filter is implemented as a second-order G
m
-C low-pass filter which can be used to tune the channel bandwidth as well as the quality factor (Q) of the RF filter. The center frequency of the filter can be tuned from 100 MHz up to 1.5 GHz by changing the clock frequency applied to the filter while its bandwidth can be tuned by tuning impedance parameters in any center frequency. To do so, the baseband impedance utilizes a frequency dependent negative resistor (i.e. FDNR) structure for having a second-order impedance. The proposed filter achieves 12–40 MHz channel bandwidth, about 2 dB noise figure (NF), and 12 dB rejection at 1GHz center frequency. According to the post-layout simulation results, the power consumption of the filter is 14 mW at 1.8 volts supply voltage consuming only 0.04 mm
²
silicon area.