A 2.4-mW interference-resilient receiver front end with series N-path filter-based balun for body channel communication

Abstract

This paper presents an interference-resilient receiver front end for body channel communication, which uses the human body as the signal transmission medium in the band of 40 to 60MHz. To tackle strong out-of-band interference resulting from the human body antenna effect, a series N-path filter-based balun preceding a low-noise amplifier is proposed to improve the frequency modulation radio interference suppression and realize single-to-differential transformation of input body channel communication signals. Besides, an enhanced harmonic rejection with combination of a series N-path filter and a harmonic rejection passive mixer using 8-phase 12.5% duty-cycle clocks as local oscillator is presented. The transconductance amplifier sharing is used to reduce the power consumption of the mixer. Fabricated in a standard 0.18-m complementary metal-oxide-semiconductor process, the proposed receiver front end occupies an area of 780x660m(2) including pads. Operating at 50MHz, the front end consumes 1.35mA from a 1.8-V supply and achieves a maximum gain of 50.5dB with a noise figure of 11.2dB, 28.5dB frequency modulation interference suppression at the second-order harmonic rejection, and 53.9dB at the third-order harmonic rejection.