This paper proposes a dual-band dual-circularly polarized (CP) aperture-coupled patch antenna with flexible frequency ratio. By simply etching a modified S-shaped slot at the central of a circular patch, dual-band dual-CP operation is realized. In addition, the frequency ratio of the two CP bands can be flexibly controlled by optimizing the length parameters of the S-shaped slot arms. As a result, the frequency ratio can be tuned from 1.12 to 1.46 according to different requirements. For demonstration, the circularly polarized patch antenna operating at 3.42 and 3.85 GHz is manufactured and tested. The measured 3-dB axial-ratio (AR) bandwidth is 1.1% and 2.3% for the right-hand circular polarization (RHCP) and left-hand circular polarization (LHCP), respectively. The measured gains at the lower and upper bands are 9.4 and 9.8 dBic, respectively.INDEX TERMS Circularly polarized, dual-band, patch antenna, slot coupled, flexible frequency ratio.
A triple-band dual-sense circularly polarized truncated patch antenna is proposed. The truncated patch is fed by the aperture etched on the ground plane. Firstly, a y-axis directional rectangular slot is introduced in the truncated patch to excite two orthogonal modes for left hand circular polarization(LHCP). Then an x-axis directional rectangular slot is employed to obtain right hand circular polarization (RHCP) performance. After that, one parasitic stub is loaded in the central of the x-axis directional rectangular slot, thus, an extra RHCP can be realized. Finally, the other parasitic stub is loaded beneath the truncated patch to improve the impedance and axial ratio performances. The etched slots and loaded stubs technologies are used in a single radiating patch to realize different senses at three different operating bands. And the senses and operating bands can be controlled by tuning according slots and stubs. Consequently, a compact tripleband dual-sense circularly polarized antenna is successfully designed. The 3-dB axial-ratio bandwidths of the proposed antenna are 2.6% (3.55-3.64 GHz), 0.24% (4.175-4.185 GHz), and 0.47% (4.26-4.28 GHz), respectively. Triple-band, circularly polarized, patch antenna, stub, slot.
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