Gain Measurement of a Cavity-Backed Spiral Antenna from 4 to 18 GHz Using the Three-Antenna Method
DEFENCE RESEARCH ESTABLISHMENT OTTAWA (ONTARIO)
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This report presents the results of the measurement of the maximum gain of a cavity-backed spiral antenna in the frequency range of 4-18 GHz. This measurement activity was requested by CFEWC. The method selected for this measurement was the three-antenna method for antenna gain measurements. As the antenna-under-test AUT is a circularly polarized CP antenna, the method was extended to obtain the CP co-pol and cross-pol gain of the AUT. This method requires the use of two other linearly polarized LP antennas. Two sets of gain measurements were performed using the LP antennas with their polarization oriented horizontally and then vertically. The two antennas were TECOM LP quad-ridged horns. Although these horns are dual polarized, only one polarization was used. This report describes also the three-antenna method algorithm, the Matlab program written for this application, and gives an outlook of the experimental steps and procedures required to implement the method. The antenna gain measurements were made in the far-field antenna measurement range in the DREO-DFL Antenna Research Laboratory DDARLing.
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