Wideband RF frontend design for flexible radio receiver

A wideband RF frontend for flexible radio applications is presented. A target is the performance adequate for multistandard 3G/ 4G systems operating in frequency range 0.8-6 GHz. Because of relaxed requirements on band select filters, more demands are placed on linearity while the necessary noise performance is assured. We discuss architecture with Low Noise Transconductance Amplifier (LNTA) and a passive mixer terminated by a low impedance load. One variant of it is a Miller integrator where its input impedance is upconverted by the mixer and provides partial attenuation for blockers at RF. We also investigate a variant with a capacitive load followed by a high impedance transconductance amplifier (TCA). In either variant there is a tradeoff between the frontend NF and IP3, and also between NF and the blocker attenuation. Optimization of the 65 nm CMOS frontend is attained by careful sizing of the mixer switches. The frontend simulation results show NF <; 3 dB, IIP3 >; +4 dBm and blocker attenuation >; 20 dB. Finally, we also discuss the demands placed on the A/D converter resolution in terms of the frontend and the receiver overall NF.