An N-Path Sub-GHz Ultra-Low Power Receiver Exploiting an N-Path Notch Filter Topology in 90 nm CMOS

Abstract

This paper describes an N-path sub-GHz ultra-low power receiver exploiting an N-path notch filter topology in 90nm CMOS process. The receiver achieves the flexibility in the operating frequency due to an adjustable internal impedance matching network with an N-path notch filter. The receiver consists of two current-reused topologies, which greatly simplifies the structure and achieves ultra-low power consumption. Specifically, the receiver incorporates: 1) an amplifier with an N-path notch filter, which acts as the first stage of the receiver to provide an input impedance of 50 Ω without an inductor. This input matching network is frequency flexible and adjustable to suit different frequencies of the input signal. Meanwhile, the N-path notch filter can suppress out-of-band interference to cope with limited frequency bands. 2) N-path passive mixers are reused for simultaneous filtering and down-conversion. 3) Amplifiers are frequency-division multiplexed to amplify both RF and baseband signals simultaneously. Finally, the receiver is fabricated in 90 nm CMOS and operates at 0.6 V supply voltage with a power consumption of 780 µW. The receiver achieves a conversion gain of 41.2 ± 3.2 dB, a noise figure of 5.7 ± 0.3 dB and an OB-IIP3 of 14.6 ± 0.5 dBm. The chip area of the implemented receiver is 0.08 µm 2 .INDEX TERMS CMOS, N-path notch filter, passive mixer, receiver, ultra-low power

Discrete-time Receivers, from N-Path to Charge Sharing Band-pass Filters: a Comparison

“…By enabling center frequency tuning through simple sampling rate adjustment, both filters prove to be adequate for Software-Defined Radio (SDR) implementations or other reconfigurable receivers (RX) [21,23,30,31], besides being well-suited for high-performance or low-power commercial standards [12,[18][19][20][32][33][34][35]. However, the RX architectures in which they are typically used may differ.…”

“…However, the RX architectures in which they are typically used may differ. N-path based receivers usually benefit from the direct conversion (DC) IF architecture [11,[14][15][16], perhaps with a few exceptions in low intermediate-frequency (IF) like [12,13,35]. On the other hand, discrete-time receivers (DT-RX) are used in super-heterodyne or high IF (HIF) architectures [20-22, 25-28, 32, 36, 37], and in direct conversion [18,19,31,38,39].…”