The proposed frequency-offset self-injection-locked (FOSIL) radar combines two independent SIL radar front-ends with up/down-mixers. The transmit frequency can be held constant by properly adjusting the injection phases and amplitudes of two oscillators. Therefore, electromagnetic interference (EMI) in the monitoring of a moving subject using conventional SIL radars is eliminated, and multiple FOSIL radars can be operated simultaneously within a limited bandwidth. In this work, one RF mixer with digital frequency demodulation is used to extract the motion of the target relative to the radar, reducing the system complexity and eliminating the $I/Q$ imbalance and dc offset calibration. The proposed system substantially improves the SNR over that of the conventional SIL radar by 28 dB, by mitigating the flicker noise and the large Doppler shift. In noncontact vital sign sensing experiments, the 5.8-GHz industrial scientific medical (ISM) band FOSIL radar prototype had a sensing range of 8 m, and its frequency swing range was reduced by over 96% without or with clutter signals. Two FOSIL radars with a frequency spacing of 2 MHz can yield exact information on the cardiopulmonary activities of two subjects at the same time in the experimental environment.

中文翻译：

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具有数字频率解调功能的频偏自注入锁定雷达可提高 SNR、消除 EMI 问题和直流偏移校准

所提出的频偏自注入锁定 (FOSIL) 雷达将两个独立的 SIL 雷达前端与上/下混频器相结合。通过适当调整两个振荡器的注入相位和振幅，可以使发射频率保持恒定。因此，消除了使用传统 SIL 雷达监测移动对象时的电磁干扰 (EMI)，并且可以在有限带宽内同时操作多个 FOSIL 雷达。在这项工作中，一个具有数字频率解调功能的 RF 混频器用于提取目标相对于雷达的运动，降低系统复杂性并消除 $I/Q$ 不平衡和直流偏移校准。通过减轻闪烁噪声和大的多普勒频移，所提出的系统大大提高了传统 SIL 雷达的信噪比 28 dB。在非接触式生命体征传感实验中，5.8GHz 工业科学医疗（ISM）频段 FOSIL 雷达样机的传感范围为 8 m，在无杂波信号或有杂波信号的情况下，其频率摆幅范围降低了 96% 以上。两个频率间隔为 2 MHz 的 FOSIL 雷达可以在实验环境中同时产生关于两个受试者的心肺活动的准确信息。