A 2:1 Band Frequency-Agile Active Microstrip Patch Antenna

This paper presents an aperture-coupled microstrip patch antenna whose resonant frequency can be tuned over (at least) one octave. For that purpose, p.i.n diodes are integrated at specific locations inside an H-shape patch antenna strongly coupled to two parasitic elements. This new concept of frequency-agile antenna is validated experimentally up to 56 GHz. Two set of antenna prototypes have been fabricated. In the first case, the antennas are "passive": the p.i.n diodes are replaced by ideal short and open lines. Numerical and experimental results show that, over the whole frequency band (24.2 GHz - 50.6 GHz), the maximum variation of the antenna gain and the reflection coefficient are smaller than 2 dB and -11 dB, respectively. The second antenna configuration is active and operates from 10 GHz to 20 GHz. The design and biasing circuits are described and discussed. Measurements are in acceptable agreement with the simulations.