The application of complex quantized feedback in integrated wireless receivers

TitleThe application of complex quantized feedback in integrated wireless receivers
Publication TypeJournal Article
Year of Publication2006
AuthorsEbadi, Z. S., S. Mirabbasi, and R. Saleh
JournalCircuits and Systems I: Regular Paper s, IEEE Transactions on
Pagination594 -603
Date Publishedmar.
Keywords1/f noise, ac-coupling, baseband signal path, baseband signal spectrum, baseline wander effects, feedback, integrated wireless receiver architectures, IQ mismatch, local oscillator phase error, low-frequency disturbances, monolithic receivers, oscillators, QFB technique, quantized feedback technique, radio receivers, spectrally efficient modulation schemes

Integrated wireless receiver architectures, such as direct-conversion receivers, offer many advantages over the conventional heterodyne receivers including smaller size, lower cost, and reduced power consumption. However, the design of monolithic receivers, using direct-conversion, involves many challenges including dealing with low-frequency disturbances, namely, dc-offset and 1/f noise (especially in CMOS implementations), in-phase (I) and quadrature (Q) amplitude and phase mismatch, local oscillator (LO) leakage, and even-order distortions. A cost-effective method to minimize the low-frequency disturbances is to use ac-coupling in the baseband signal path. However, it results in baseline wander effects, especially in spectrally efficient modulation schemes such as quadrature amplitude modulation (QAM) where the baseband signal spectrum contains a significant amount of energy near dc. A system solution to mitigate the effects of low-frequency disturbance is presented in this paper. The quantized feedback (QFB) technique is used in conjunction with ac-coupling to minimize the baseline wander effects. A cross-coupled (CC) QFB extension to compensate for the receiver local oscillator phase error as well as the IQ mismatch is also described. Simulation results are presented to demonstrate the effectiveness of this complex QFB technique


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