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

Abstract

SummaryThis 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 60 MHz. 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‐μm complementary metal‐oxide‐semiconductor process, the proposed receiver front end occupies an area of 780 × 660 μm2 including pads. Operating at 50 MHz, the front end consumes 1.35 mA from a 1.8‐V supply and achieves a maximum gain of 50.5 dB with a noise figure of 11.2 dB, 28.5 dB frequency modulation interference suppression at the second‐order harmonic rejection, and 53.9 dB at the third‐order harmonic rejection.

Bird's‐eye view of analog and mixed‐signal chips for the 21st century

“…The switches and capacitors are intrinsically linear, like the N‐path filter that has its center frequency defined by the clock frequency. In recent years, the literature reported a wide variety of N‐path filters, and their associated receivers and transmitters 1–12 …”

“…In recent years, the literature reported a wide variety of N-path filters, and their associated receivers and transmitters. [1][2][3][4][5][6][7][8][9][10][11][12] A key invention of our research group is the N-path SC gain loop 9 (Figure 2), introduced as a novel direction to develop area-efficient SAW-less transceivers. Unlike the concepts of the direct-conversion transmitter (baseband [BB] filter !…”

A lumped‐element balun design with multi‐interference suppression for push–pull power amplifier

“…However, one challenge of designing a modern communication system with a low bit error rate (BER) is dealing with interferences. [13][14][15] The undesired interferences can be either harmonic, which widely exists in active components due to intermodulation and other nonideal factors, or crosstalk in multi-band systems and multiple input multiple output (MIMO) systems. Figure 1 plots three curves with/without harmonic interferences in TX.…”

Analysis of nonidealities of N‐path circuits using impulse response

“…N‐path filters, with their high tunability and linearity, are an interesting alternative for SAW filters in RF applications such as multi‐standard receivers . These filters are simply composed of switches and capacitors, and hence, can be easily realized on‐chip in CMOS technologies.…”