Analysis of a high frequency and wide bandwidth active polyphase filter based on CMOS inverters
Analog Integrated Circuits and Signal Processing
A CMOS low power current-mode polyphase filter
Proceedings of the 14th ACM/IEEE international symposium on Low power electronics and design
General non-recursive coefficients calculation formula for sincN filter
Analog Integrated Circuits and Signal Processing
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A new idea for generation of quadrature signals on chip is presented. The topology is based on a passive RC polyphase filter, where the resistive parts are made active by using inverters. The active filter combines quadrature generation, isolation, and gain without losing quadrature performance compared to a regular RC polyphase filter. The filter technique is demonstrated in a 10 GHz front-end application where a broadband VCO, having a tuning range of 1.44 GHz, drives an active polyphase filter to generate quadrature LO signals. According to simulations the quadrature phase error shows a typical tuned behavior and stays below 0.8° for the complete tuning range. Since the signal amplitude is high throughout the filter the noise is low, below 160 dBc/Hz at 10 MHz offset. The high amplitude also reduces the need for high gain tuned buffers, thereby enabling significant reductions in chip area.