The trend towards reconfigurable receivers requires on-chip flexible filters that can replace dedicated, bulky and non-tunable filters (e.g., SAW and BAW [1]). Although BAW filters are compatible with silicon processes, their center frequency is sensitive to thickness variation of the piezoelectric
Abstract Electronically variable delays for beamforming are generally realized by phase shifters. Although a constant phase shift can approximate a time delay in a limited frequency band, this does not hold for larger arrays that scan over wide angles and have a large instantaneous bandwidth. In thi
Periodically time-variant passive 8-path notch filters are demonstrated in 65nm CMOS technology, with a notch frequency tunable from 100MHz to 1.2GHz with a clock signal. In a 50Ω environment, filter insertion loss in the pass band is 1.4-2.8dB, while the rejection at the notch frequency is >20dB. G
Phased arrays in CMOS for consumer communication bands aim to enhance receiver performance by exploiting beamforming with antenna arrays. Sensitivity increases with the number of antenna elements through array gain and interferers can be cancelled through the spatial filtering of the beam pattern [1
A 1-4GHz 4-element phased array receiver frontend demonstrates spatial interferer rejection using null steering. Element phase and amplitude control are performed by a switchedcapacitor vector modulator with integrated downconversion, utilizing a rational sine/cosine approximation. The 65nm CMOS rec
Abstract—A spectrum analyzer requires a high linearity to handle strong signals, and at the same time a low NF to enable detection of much weaker signals. This is not only important for lab equipment, but also for the spectrum sensing part of cognitive radio, where low cost and integration is at a p
Abstract-Practical time delay circuits do not have a perfectly linear phase-frequency characteristic. When these delay circuits are applied in a phased-array system, this frequency dependency shows up as a frequency dependent beam direction (“beam squinting”). This paper quantifies beam squinting fo
Software-Defined Radio (SDR) and Cognitive Radio (CR) concepts have recently drawn considerable interest. These radio concepts built on digital signal processing to realize flexibly programmable radio transceivers, which can adapt in a smart way to their environment. As CMOS is the mainstream IC tec
Abstract—Spectrum sensing is one of the key characteristics of a cognitive radio. Energy detection provides maximum flexibility by not relying on any prior knowledge, but suffers from an SNRwall due to noise uncertainty. Crosscorrelation of the outputs of two receiver paths is a technique to reduce
Abstract Spectrum sensing is a key enabler of cognitive radio but generally suffers from what is called a signal-to-noise ratio (SNR) wall, i.e., a minimum SNR below which it is impossible to reliably detect a signal. For energy detection, which has the advantage of not requiring knowledge of the si
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