Implementation of an in‐field CMOS frequency division multiplexer for 9.4 T magnetic resonance applications

This paper introduces the implementation of an application‐specific complementary metal oxide semiconductor frequency division multiplexer as a novel solution to interface magnetic resonance (MR) phased arrays of micro‐detectors to an image‐processing unit, thus reducing the complexity and space issues associated with MR detector arrays. The frequency multiplexer, in a compact 3 × 4 mm silicon die, is designed to operate at 400 MHz, which is the Larmor frequency of ¹H protons in a 9.4‐T MR imaging system. The system implements eight channels, where each channel consists of a low‐noise amplifier, a frequency mixer, and a band‐pass filter. The maximum gain of an individual channel after the band‐pass filter stage is 38 dB. The suppression of the local oscillator ranges from 40 to ?51 dB, and the maximum coupling between channels is ?39 dB. The input dynamic range of an individual channel is 8 mV. Each channel consumes 54 mA from a 3.3‐V source. The chip operates without errors within a high 9.4‐T magnetic field. Copyright © 2014 John Wiley & Sons, Ltd.