A 0.3dB-NF SiGe LNA Array for 10.5T Multi-Channel MRI Receivers

This paper presents an on-chip LNA array at 447 MHz for 10.5 T multi-channel MR receive arrays. First, we develop a theoretical foundation for minimizing bipolar amplifier noise figure, and design an LNA based on this approach. Additionally, we consider several implementation factors including coupling between channels and magnetic-field robustness. A preamplifier array based on this concept is then fabricated using the GF 8XP 130 nm SiGe process. The total area of the 4-element array is <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$2.2 \text{mm} \times 1.2 \text{mm}$</tex> with each channel consuming 20 mW. Measurements show an excellent noise figure of 0.3 dB, a gain of 28 dB across 410-510 MHz, and more than 29 dB isolation making this array a viable replacement for existing bulky off-the-shelf solutions. The theoretical calculations, design kit simulations and measurements results show good agreement. This chip opens the door for integrated receiver systems for next generation high-channel-count MR arrays.