A High-Gain Circularly Polarized U-Slot Patch Antenna Array

Patch antennas are widely applied in modern wireless communication systems. However, conventional patch antennas have the disadvantage of narrow bandwidth and are not suitable for Ku-band satellite broadcast reception. Many researchers have proposed various techniques to enhance the bandwidth of probe-fed patch antennas, e.g., employing thick substrate [1], adding parasitic patches either in the same layer (coplanar) [2]-[3] or in another layer (stacked) [4], and using capacitor-loaded patches [5]. With the first technique, the substrate thickness increases and induces the excitation of surface waves [6]. Apart from reducing the radiation efficiency, these surface waves diffract at the substrate edges and deteriorate the radiation patterns. The presence of coplanar and stacked geometry has the disadvantage of increasing the area and thickness of the antenna, respectively. Additional capacitors cause antenna gain reduction because of the ohmic loss of the loading chip resistor.