A single-feed dual-band circularly polarized microstrip antenna with spiral slots

A compact, low-cost, dual-band circularly polarized (CP) microstrip antenna with single-feed operating at both 1555 MHz and 2500 MHz bands is designed in this paper. The circular patch of the antenna is slotted with four complementary spiral grooves for dual-band radiation. The bandwidths of |S₁₁|<;-10dB of the antenna are 42 MHz centered at 1555 MHz and 25 MHz centered at 2500 MHz, respectively. The frequency ratio (FR) of the upper to lower operating frequencies is about 1.6. The 3dB axial ratio (AR) bandwidths are 846 MHz at the lower band and 229 MHz at the upper band. Measured results agree with simulated ones, which show that right-hand circularly polarized (RHCP) radiation can be achieved in these two bands.