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International Journal of Antennas and Propagation
Volume 2017 (2017), Article ID 6198686, 10 pages
https://doi.org/10.1155/2017/6198686
Research Article

Non-Foster Matching Circuit Design via Tunable Inductor for VLF Receive Loop Antennas

Department of Electronic Engineering, Naval University of Engineering, Wuhan 430033, China

Correspondence should be addressed to Chao Liu

Received 15 March 2017; Revised 28 August 2017; Accepted 1 October 2017; Published 24 October 2017

Academic Editor: Toni Björninen

Copyright © 2017 Yalong Yan et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

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 fractional bandwidth, marking a 383% improvement as well as enhanced transducer gain () 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.