Antenna Arrays for Dual-Frequency Harmonic Radar Application

Abstract: The aim of this thesis is to design two patch antenna arrays for dual-frequency harmonic radar application, one for the transmitter and the other for the receiver. The arrays are used to track the Bogong moth that migrates from the countryside to the Australian Alps during spring. The tracking is done at the radar by operating the transmitter at one frequency and the receiver at twice the frequency. A transponder is attached to the target which doubles the frequency of the signal received from the transmitter before sending the signal back to the receiver. The antenna arrays at the radar are designed with the ISM band (unlicensed spectrum) of 5.8GHz for the transmitter and 11.6GHz for the receiver. Coupling and polarization play a major role in the patch antenna array design and these aspects are studied in this thesis. Based on the compatibility in the radar system the maximum allowed size of the antenna arrays should be less than or equal to 200×300mm. We have chosen RT/duroid 5880 substrate for both the transmitter and receiver antenna arrays with the permittivity of 2.20. Based on a previous study, at 5.8GHz we are supposed to get a gain of 20dBi at the transmitter array and 26dBi at the receiver array. Also, the bandwidth of the system is expected to be 50MHz. According to the planar array the aperture efficiency should be between 0.6 to 0.8 for the antenna arrays. We used FEKO, an electromagnetic simulation software, to design the antenna arrays. An edge port is used in the simulation as a source of power supply for the antenna arrays. Upon designing the antenna arrays in the simulation software, various parameters have been examined. On that note, we obtained acceptable reflection coefficient, input impedance, and voltage standing wave ratio (VSWR). The simulated bandwidth, for the VSWR of less than 1.5, is verified in experiment. We used an SMA (Sub Miniature version A) connector for both the antenna arrays in the fabrication. We achieved a simulated gain of 15dBi at the transmitter array and 16dBi at the receiver antenna array.