A Novel Complex Filter Design With Dual Feedback for High Frequency Wireless Receiver Applications

TLDR: The proposed design achieves an unconditional stability thanks to the internal negative feedback mechanism and improves the Image Rejection Ratio (IRR) and Common Mode Rejection ratio (CMRR) of the proposed design.

Abstract: This brief presents a low-power tunable $G_{m}-C$ complex filter for wireless receiver applications. The proposed design achieves an unconditional stability thanks to the internal negative feedback mechanism. This negative feedback helps in achieving a high-frequency shift and the negative transconductance of the circuit improves the Image Rejection Ratio (IRR) and Common Mode Rejection Ratio (CMRR) of the proposed design. The proposed circuit has independent control over bandwidth and frequency shift which makes an attractive solution for multi-standard and multi-mode wireless receiver applications. A second order complex filter is designed for Long Term Evolution (LTE) application and used as a test vehicle to verify the proposed concept. The circuit is designed using a 180 nm CMOS process with a power consumption of $106~\mu \text{W}$ from a 1 V supply voltage. It is centered at 9.2 MHz with −3 dB bandwidth of 1.4 MHz and provides an IRR of 51 dB with a voltage gain of 45 dB. The total integrated in-band Input Referred Noise (IRN) is $70~\mu V_{rms}$ and FoM of 47 aJ is achieved. The area of the layout of the proposed design is $78~\mu \text{m}$ X $78~\mu \text{m}$ .