Gain and Noise Performance of Non-Foster Matching Circuit for VLF Receiver Loop Antenna

Abstract

Abstract-Non-Foster matching circuits are those that can function as negative capacitors or inductors, and can thus overcome the gain-bandwidth limitation of passive matching circuits for antennas. This paper presents a non-Foster matching circuit (NFC) for a very low frequency (VLF) receiver loop antenna. The bandwidth of the antenna was improved by 383%, and the average gain was improved in most bands compared to a passive matching circuit (over 15-30 kHz). In contrast to circuits reported in other publications, the signal to noise ratio (SNR) of the passive matching network performed better than the non-Foster matching network. To analyze this phenomenon, a noise model was developed for the simplified balanced NFC, and noise analysis was conducted between the non-Foster and passive matching networks, which indicates that the non-Foster matching circuits cannot provide a better SNR performance than the passive matching circuits under low noise figure level receiver conditions.

A high Q piezoelectric resonator as a portable VLF transmitter

“…The size and loss of this matching network, even assuming a Q of 1000, greatly exceed the antenna itself, making this technique non-viable. Active non-Foster matching networks, while shown to improve system bandwidth, are unwieldy at high voltages 10–12 . A potential solution is acoustically resonant transmitters 3,13 .…”