Investigation into nonlinearity of frequency agile antennas

Hancock, Hugh (2020). Investigation into nonlinearity of frequency agile antennas. University of Birmingham. Ph.D.

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Abstract

A series of investigations were undertaken to assess the tuning range, gain and linearity of frequency reconfigurable varactor loaded patch antennas with design frequencies ranging from 1.4 – 1.8GHz. These parameters were assessed using simulation and measurements, including two-tone testing of the fabricated antennas in an anechoic chamber.

To understand the effects of the antenna’s design on tunability, gain and linearity, six separate investigations were undertaken. These were (i) effects of design frequency and antenna substrate properties (ii) location of varactors on the antenna (iii) number of varactors loading antenna (iv) use of abrupt and hyperabrupt varactor (v) use of common cathode configurations (vi) use of common cathode configuration with parasitic patches with U-slots cut outs.

It was found that the greater the area reduction in a patch, compared to a patch with no varactor, the greater tunability achieved. The reduction of a patch size from varactor loading decreases the gain of the antenna. Increasing the number of varactors on the patch improves linearity and tunability. Using a common cathode configuration of varactors on the radiating edge of an antenna maintains tunability while improving the linearity.

These findings led to a novel type of antenna that uses the common cathode configuration of varactors with parasitic patches with U-slot cut outs to maintain gain across the frequency band whilst maintaining linearity and tunability.

Type of Work:

Thesis (Doctorates > Ph.D.)

Award Type:

Doctorates > Ph.D.

Supervisor(s):