Wideband Co-Linearly Polarized Microstrip Antenna for In-Band Full-Duplex Systems Using Two Parallel L-Probes

A co-linearly polarized wideband microstrip antenna with a single shared patch feeding by two parallel L-probes is proposed in this letter. The shared patch introduces a new coupling path for the L-probes. The coupling coefficients of the two L-probes, as well as the L-probe and the patch, are quantitatively derived based on the coupled resonators theory. It is proved that by adjusting the geometries and dimensions of the two L-probes and the patch, a natural wideband high isolation can be obtained. A demonstration example is designed and measured to validate the feasibility of the proposed scheme. The results show that the proposed antenna can achieve impedance matching of −10 dB and high isolation of 20 dB in the frequency range from 3.2 GHz to 4 GHz. Besides, the measured efficiency ranges from 91% to 99% with an average realized gain of 7.4 dB. Furthermore, another example with a lower height is also designed to justify the practical usefulness, showing 19.8% decoupling bandwidth.