Circularly polarized single-layer U-slot microstrip patch antenna has been proposed. The suggested asymmetrical U-slot can generate the two orthogonal modes for circular polarization without chamfering any corner of the probe-fed square patch microstrip antenna. A parametric study has been carried out to investigate the effects caused by different arm lengths of the U-slot. The thickness of the foam substrate is about 8.5% of the wavelength at the operating frequency. The 3 dB axial ratio bandwidth of the antenna is 4%. Both experimental and theoretical results of the antenna have been presented and discussed.

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A novel miniature antenna design capable of both surface-tosurface and surface-to-orbiter communications has been presented in this paper. The benefit of this antenna is that it provides comparable performance of two separate antennas (that is, a dipole and a microstrip patch) in a single package and at a fraction of the size. The relatively low gain (ϳ1.5 dBi) and small bandwidth (ϳ10 MHz) at the S-band makes this antenna suitable for low-data-rate, proximity communications, while the higher gain and wider bandwidth at the Ku-band makes it ideal for relaying collected data or communications through satellite links over longer distances. This work presents a viable candidate antenna design for lunar-surface robotic communications applications. ACKNOWLEDGMENTSThe authors wish to thank Kevin Lambert for his insightful recommendations regarding the construction of this antenna design. REFERENCES