Active feedback receiver with integrated tunable RF channel selectivity, distortion cancelling, 48dB stopband rejection and >+12dBm wideband IIP3, occupying <0.06mm2 in 65nm CMOS

The impedance transformation property of passive mixers enables integrated high-Q channel selection at RF with a programmable center frequency through a clock [1,2]. As such, this technique is suitable for addressing both linearity and flexibility requirements in wideband and cognitive radio applications. However, given the typically low resistance level at the RF side of the receiver chain, the RC product necessary for filtering results in large capacitors, and, consequently, large die area that does not scale with technology. In addition, filter rejection at the RF side is limited by the resistance of the switches of the passive mixer. Thus, large switches are typically needed for moderate rejection values (5Ω switches for 16dB rejection [2]), which translates to higher power consumption in the LO buffers. Furthermore, filtering prior to the LNA [1] or eliminating it altogether [3] improves linearity at the expense of noise and switching harmonics being injected directly at the antenna node. Conversely, an LNA first architecture offers an opposite trade-off. This work demonstrates a highly compact design of a direct-conversion receiver with an active feedback frequency translation loop to perform channel selection at the LNA output while simultaneously cancelling its distortion.