A MedRadio RF receiver integrated circuit for implanted and wearable biomedical devices must be resilient to the out-of-band (OOB) orthogonal frequency division modulation (OFDM) blocker. As the OFDM is widely adopted for various broadcasting and communication systems in the ultra-high frequency (UHF) band, the selectivity performance of the MedRadio RF receiver can severely deteriorate by the second-order intermodulation (IM2) distortion induced by the OOB OFDM blocker. An analytical investigation shows how the OFDM-induced IM2 distortion power can be translated to an equivalent two-tone-induced IM2 distortion power. It makes the OFDM-induced IM2 analysis and characterization process for a MedRadio RF receiver much simpler and more straightforward. A MedRadio RF receiver integrated circuit with a significantly improved resilience to the OOB IM2 distortion is designed in 65 nm complementary metal-oxide-semiconductor (CMOS). The designed RF receiver is based on low-IF architecture, comprising a low-noise amplifier, single-to-differential transconductance stage, quadrature passive mixer, trans-impedance amplifier (TIA), image-rejecting complex bandpass filter, and fractional phase-locked loop synthesizer. We describe design techniques for the IM2 calibration through the gate bias tuning at the mixer, and the dc offset calibration that overcomes the conflict with the preceding IM2 calibration through the body bias tuning at the TIA. Measured results show that the OOB carrier-to-interference ratio (CIR) performance is significantly improved by 4–11 dB through the proposed IM2 calibration. The measured maximum tolerable CIR is found to be between −40.2 and −71.2 dBc for the two-tone blocker condition and between −70 and −77 dBc for the single-tone blocker condition. The analytical and experimental results of this work will be essential to improve the selectivity performance of a MedRadio RF receiver against the OOB OFDM-blocker-induced IM2 distortion and, thus, improve the robustness of the biomedical devices in harsh wireless environments in the MedRadio and UHF bands.

中文翻译：

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用于 MedRadio 生物医学设备和传感器的 CMOS 射频接收器对 OFDM 引起的二阶互调失真具有更高的恢复能力

用于植入式和可穿戴生物医学设备的 MedRadio RF 接收器集成电路必须能够适应带外 (OOB) 正交频分调制 (OFDM) 阻塞器。由于 OFDM 被广泛用于超高频 (UHF) 频段的各种广播和通信系统，MedRadio RF 接收器的选择性性能会因 OOB OFDM 阻塞引起的二阶互调 (IM2) 失真而严重恶化. 一项分析研究显示了如何将 OFDM 引起的 IM2 失真功率转换为等效的双音引起的 IM2 失真功率。它使 MedRadio RF 接收器的 OFDM 引起的 IM2 分析和表征过程更加简单和直接。MedRadio RF 接收器集成电路在 65 nm 互补金属氧化物半导体 (CMOS) 中设计，其对 OOB IM2 失真的恢复能力显着提高。设计的 RF 接收器基于低中频架构，包括低噪声放大器、单差分跨导级、正交无源混频器、跨阻抗放大器 (TIA)、镜像抑制复带通滤波器和分数相位-锁环合成器。我们描述了通过混频器处的栅极偏置调谐进行 IM2 校准的设计技术，以及通过 TIA 处的体偏置调谐克服与前面 IM2 校准冲突的直流偏置校准的设计技术。测量结果表明，通过建议的 IM2 校准，OOB 载波干扰比 (CIR) 性能显着提高了 4-11 dB。测得的最大容许 CIR 对于双音阻塞条件在 -40.2 和 -71.2 dBc 之间，对于单音阻塞条件在 -70 和 -77 dBc 之间。这项工作的分析和实验结果对于提高 MedRadio RF 接收器对 OOB OFDM 阻塞引起的 IM2 失真的选择性性能至关重要，从而提高 MedRadio 和超高频频段。