A high-speed TIA based programmable broadband complex filter

Abstract

By combining the functions of a poly phase filter and a variable gain amplifier, a 2nd order active complex filter is proposed in this paper for 5G and other broadband applications. Thanks to the TIA based structure, the complex filter has an operating speed up to 2.3 GHz and a variable voltage gain of 0–20 dB. Its center frequency is programmable from 500 MHz to 1.85 GHz by integrating an on-chip capacitor tank. An image rejection ratio of higher than 17 dB is achieved when its gain is 14 dB for all center frequency settings, consuming less than 40.6 mW from a 1.4 V supply. Fabricated in a 65 nm CMOS process, the core circuit area is 0.25 mm × 0.2 mm. To the best knowledge of the authors, this work is the first published GHz active complex filter, advancing the state-of-the-art.