CHARACTERIZATION OF ELECTRICALLY SMALL, PERIODICALLY TIME-VARYING ANTENNAS

Abstract

Linear, time-invariant (LTI) electrically small receive antennas have well known limits on their gain-bandwidth performance. As a method to circumvent these limits, non-LTI antennas, such as time-varying antennas, have become increasingly popular in the literature. One time-varying design of interest is that of a parametric amplifier implemented on the aperture of an electrically small receive antenna to create a parametrically-tuned receive antenna. This work implements a parametrically-tuned receive antenna in a non-degenerate architecture to achieve a 3.5 times improvement in 3 dB bandwidth and data throughput over a conventional LTI receive antenna using the same physical concentric loop antenna footprint. A suite of measurement methods is discussed in order to characterize time-varying antennas as the common measurement methods applied to LTI antennas makes assumptions regarding reciprocity and measurement frequencies that are no longer valid under the time-varying regime. Included is the development of a novel Y-Factor method for time-varying antennas that considers the impact of internal and external noise at the harmonics on the noise figure of the antenna and the receive system. Finally, the gain-bandwidth trade-off is analyzed for the LTI concentric loop antenna as well as the implemented time-varying antenna.