Abstract
N-path techniques have become a popular candidate alternative to external pre-selection filtering in wireless receivers. Their main attraction lies in enabling tunable on-chip high- Q filters, with straightforward migration from one CMOS node to another. However, parasitic capacitance at the N-path filter input offsets the bandpass response from the desired center frequency in wideband circuits. In this paper, we focus on an LNA-first receiver and show that the offset at the LNA output varies in magnitude depending on LNA and filter load impedance properties. An offset-tuning approach is then evaluated for its effects on receiver gain and noise and to obtain design guidelines. We propose a digitally controllable implementation that preserves front-end gain and linearity, with a small penalty on receiver NF. A programmable 0.7–2.7-GHz front-end in 40-nm CMOS verifies the functionality. At 1.7 GHz, the front-end has a gain of 37 dB, a NF of 5.2 dB, and an out-of-band IIP3 of + 1 dBm.
Original language | English |
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Article number | 6926874 |
Pages (from-to) | 234-243 |
Number of pages | 10 |
Journal | IEEE TRANSACTIONS ON CIRCUITS AND SYSTEMS I-REGULAR PAPERS |
Volume | 62 |
Issue number | 1 |
DOIs | |
Publication status | Published - Jan 2015 |
MoE publication type | A1 Journal article-refereed |
Keywords
- Blockers
- circuit optimization
- CMOS
- complex filtering
- linearity
- low-noise amplifiers
- N-path filtering
- quadrature
- receivers
- RF front-ends