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This paper presents an X-band circularly polarized patch antenna with a simulated high gain of 12.5 dBi and a simulated side-lobe-level of below −20 dB, within the bandwidth of 5.2 %. This single element antenna achieves high gain by exploiting the mode superposition of TM 11 + TM 13 (excited by a circle of vias loading the cavity) and TM 12 + TM 14 (excited by the cavity itself) radiated from the two apertures, respectively. A simple feeding network, consisting of a quadrature hybrid and a couple of 90 • bent branches, is used in the design to excite RHCP or LHCP mode in the antenna cavity. A capacitive disk feeding is implemented so that the antenna can be matched to the feeding network, and the super-positioned fields inside the cavity are not disturbed by the feeding pins. This approach makes the design of a dual-sense circularly polarized antenna with high gain easier since the array configuration is not needed. High gain, in combination with a dual-sense circular polarization, makes the proposed antenna particularly attractive for space applications involving small satellites. With the proposed design, it is possible to employ only one antenna rather than two (RHCP and LHCP), thus saving space on the aircraft, which is clearly a limited resource.INDEX TERMS Circular patch, circular polarization, high gain, sidelobes suppression, small satellites.

Circularly polarized (CP) antennas are used in space applications for telemetry tracking and command (TT&C). In this paper, we present an antenna for a TT&C system that can employ only four antennas to achieve a wide quasi-isotropic coverage. The proposed single-feed circular polarized annular patch antenna is low profile and compact. It exhibits a wide impedance bandwidth of 19.7%, wide-angle circular polarization with an on-axis maximum gain higher than 6 dBi and an axial ratio below 4 dB in the frequency band 2.0–2.3 GHz. The developed low-cost antenna can be used for small-satellite data downlink where only two right hand circular polarized (RHCP) antennas and two left hand circular polarized (LHCP) antennas would be required since each antenna has an adequate CP gain on a wide angle. A prototype antenna has been fabricated and measured. The experimental validation shows a good agreement of the measured impedance bandwidth, axial ratio, and far-field pattern with the ones predicted by numerical full-wave study.

This paper presents a wideband or high gain 4x4 array operating in k-band. The unit cell of this array is a rectangular patch antenna in a stacked configuration. Four rectangular patches are passively excited by an additional rectangular patch located underneath. The latter is excited by a substrate integrated waveguide (SIW) through an aperture etched on the ground plane. By moving the relative position, and therefore the overlapped area, between the passive patches and the active one, a wideband or a high gain behavior can be obtained, maintaining the same layout. The proposed array achieves the impedance bandwidth of 12.55% with a gain of 22 dBi for the wideband case. In the high gain case, the impedance bandwidth is 5.5% with a gain of 24 dBi.