A 4-Element Phased-Array System With Simultaneous Spatial- and Frequency-Domain Filtering at the Antenna Inputs

Abstract

-To reject strong interference in excess of 0 dBm, a 4-element LO-phase shifting phased-array receiver with 8-phase passive mixers terminated by baseband capacitors is presented. The passive mixers up-convert both the spatial and frequency domain filtering from baseband to RF, hence realizing blocker suppression directly at the antenna inputs. A comprehensive mathematical model provides a set of closed-form equations describing the spatial and frequency domain filtering including imperfections. A prototype is realized in 28 nm CMOS. It exploits 3 rd harmonic reception to achieve a wide RF-frequency range from 0.6-4.5 GHz at 34-119 mW power dissipation, while also providing impedance matching. Out of the band/beam, a 1 dB-compression point as high as +12/+10 dBm has been measured. The 1-element NF over the RF-frequency range is 4-6.3 dB, while in-beam/band IIP3 values of 0..+2.6 dBm are measured. This proposed technique can be instrumental to make RF receivers more robust for interference, while still being flexibly tunable in frequency.

Analysis of the Signal Transfer and Folding in N-Path Filters With a Series Inductance

“…Recent research has shown that N-path filters are promising candidates to realize tunable band-pass filters [2]- [12] and also simultaneous frequency and spatial domain filtering [13], [14]. Although the concept dates back to the 1960s [15], [16], only with the advent of nanometer CMOS technologies can such filters now operate at low GHz RF frequencies.…”

“…Moreover, the linearity of passive mixers realized with MOS switches can be very good, and blockers in the order of 0 dBm can be handled provided the switches have sufficient overdrive voltage. As switches and capacitors scale well with CMOS downscaling, the technique can benefit from process scaling (see for instance [14] which compares a 65 nm and 28 nm chip).…”

N-path filters and mixer-first receivers: A review

“…N-path filters can not only be used for frequency-domain filtering, but also for spatial domain filtering, i.e. beamforming, as demonstrated in [55,59,[64][65][66]. Especially if implemented at the first node of the receiver, very high compression point and Fig.…”

“…IIP3 is possible [66]. Another interesting property of N-path filtering is the controllable gain and group delay [67], which was exploited to improve wideband self-interference cancellation for an in-channel full duplex transceiver [68].…”

Vulnerability analysis of the wireless infrastructure to intentional electromagnetic interference

“…This is not desirable from a functional point of view due to the physical volume this occupies. These developments resulted in the design of blocker-tolerant receivers without front end filters suitable for wideband wireless applications [137][138][139].…”