This paper presents a non-Foster matching circuit (NFC) for very low frequency (VLF) receive loop antennas. A 1 ⁎ 1 m VLF receive loop antenna was designed with a CMOS switch-based tunable inductor built into the NFC. The NFC can be applied to different VLF loop antennas by adjusting the number and inductance of the cells in the tunable inductor. A loop antenna was matched to the designed NFC with −10 dB S11 fractional bandwidth, marking a 383% improvement as well as enhanced transducer gain (S21) compared to most bands in passive matching (over 15–30 kHz). The noise and received signal-to-noise ratio (SNR) of the matching network were assessed to find that, with a low noise floor level (4 dB) receiver, the SNR of the passive loaded antenna performs better than the non-Foster loaded antenna in VLF.
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机译：本文介绍了非常低频（VLF）接收环天线的非培养匹配电路（NFC）。 1÷1 M VLF接收环形天线设计，采用基于CMOS开关的可调电感器内置于NFC中。通过调整可调谐电感器中的单元的数量和电感，可以将NFC应用于不同的VLF环形天线。环形天线与具有-10dB S11分数带宽的设计的NFC匹配，与无源匹配中的大多数带（超过15-30kHz）相比，标记了383％的改进以及增强的换能器增益（S21）。评估匹配网络的噪声和接收的信噪比（SNR）以发现，通过低噪声底层（4 dB）接收器，无源装载天线的SNR比加载的非福斯特更好地执行VLF中的天线。
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