Active Eight-Path Filter and LNA With Wide Channel Bandwidth and Center Frequency Tunability

This paper presents a differential eight-path bandpass filter with tunable center frequency and bandwidth. Fully differential Miller compensated Butterworth Gm-C biquads are used to implement the active low-pass filters required in the structure of the eight-path filter. The -3-dB bandwidth of each Gm-C filter can be tuned from 2.5 to 51 MHz by means of six digital bits. The center frequency of the eight-path filter can be tuned from 100 MHz to 2 GHz by varying the frequency of the 12.5% duty cycle clocks applied to the gates of the switches in the filter. A wideband low-noise amplifier (LNA) is designed to precede the eight-path filter and acts as an active single-to-differential converter while providing a moderate voltage gain to compensate for the noise produced by the eight-path filter. The LNA has a noise canceling common-gate common-source with 20 dB of gain and a noise figure (NF) of 1.8 dB. The filter and LNA are designed and fabricated in 180-nm CMOS process. The circuit operates in 100 MHz to 2 GHz frequency range, achieving a voltage gain of 19 dB and a total NF of 3.3 dB. The achieved out-of-band input third-order intercept point of the circuit is +23 dBm, and the power consumption of the filter is approximately 32.3 mW, while the LNA consumes 16.5 mW.