Abstract:

A new type of dual loop broadband circularly polarized antenna is designed and fabricated to overcome the microstrip antennas disadvantages of narrow inherent frequency band,low radiation efficiency,and small possibility of high gains.The patch unit of the antenna uses the slot/strip configuration composed of a slot loop and a strip loop.The slot loop offers a minimum AR point at a lower frequency while the strip loop offers a minimum AR point at a higher frequency.An appropriate combination of the two minimum AR points can result in a significant enhancement for the circularly polarized bandwidth.A broadband balun is used for the feeding of the antenna and the impedance matching.Simulation and measurement results of the fabricated antenna with optimized parameters exhibit a broadband impedance bandwidth (VSWR≤2) of,37% an axial ratio (≤3 dB) of 29.8%,and a gain up to 6.4 dB.

Key words: dual loop;broadband circularly polarized;microstrip antenna