Tunable selective receiver front end with impedance transformation filtering

Abstract

A highly selective impedance transformation filtering technique suitable for tunable selective RF receivers is proposed in this paper. To achieve blocker rejection comparable to SAW filters, we use a two stage architecture based on a low noise trans-conductance amplifier (LNTA). The filter rejection is captured by a linear periodically varying (LPV) model that includes band limitation by the LNTA output impedance and the related parasitic capacitances of the impedance transformation circuit. This model is also used to estimate "back folding" by interferers placed at harmonic frequencies. Discussed is also the effect of thermal noise folding and phase noise on the circuit noise figure. As a proof of concept a chip design of a tunable RF front-end using 65 nm CMOS technology is presented. In measurements the circuit achieves blocker rejection competitive to SAW filters with noise figure 3.25.2 dB, out of band IIP3 > +17 dBm and blocker P1dB > +5 dBm over frequency range of 0.5-3 GHz.

Analysis of nonidealities of N‐path circuits using impulse response

“…N‐path filters, with their high tunability and linearity, are an interesting alternative for SAW filters in RF applications such as multi‐standard receivers . These filters are simply composed of switches and capacitors, and hence, can be easily realized on‐chip in CMOS technologies.…”

A −40‐dB EVM 20‐MHz subsampling multistandard receiver architecture with dynamic carrier detection, bandwidth estimation, and EVM optimization

“…The existing reconfigurable receivers in the literature are reported as wideband sampling receivers [5][6][7][8] and multistandard subsampling receivers. [9][10][11][12][13][14] In these sampling receivers, selection of the sampling frequency defines the receiver architecture, which includes an oversampling receiver with discrete-time mixer (DTM), 5 time-interleaved (TI) discrete-time oversampling receiver, 6 and sub-sampling receiver.…”

Harmonic fold back reduction at the N‐path filters

“…Recently, CMOS technology enhancement makes it possible to implement high-frequency N-path band-pass filters, even in radio frequencies (RF). Today, extensive research in this area is ongoing [18][19][20][21][22][23][24][25][26][27][28].Center frequency tunability in a wide frequency range by the switching frequency, capability of owning high Q-factor, linearity, and process scalability are some of the most attractive properties of the N-path filters [18,19]. Limited out-of-band rejection, due to the switches on-resistance (R SW ), and pass-band 'round' shape problems have been addressed in [20,21].…”

“…Recently, CMOS technology enhancement makes it possible to implement high-frequency N-path band-pass filters, even in radio frequencies (RF). Today, extensive research in this area is ongoing [18][19][20][21][22][23][24][25][26][27][28].…”