Dual Band Integrated Antennas and Arrays For Global Navigation Satellite System.

Abstract

The evolution of the Global Navigation Satellite System (GNSS) is aiming to provide more benefits in comparison to the existing standalone Global Positioning System (GPS). The biggest advantage for such an evolution will be higher visibility provided by combined number of navigation satellites in the orbit. Although a multi-band GNSS antenna and the receiver can exploit the advantages of the combined navigational systems, one of the biggest factors affecting the accuracy of the position solution is the presence of the multipath interference. These interference signals are generated by the reflection and diffraction of the incoming line of sight signals from different objects present around the antenna. This work presents the design, development and measurement of a novel dual band multipath mitigating antenna for precise orbit determination (POD) applications. The proposed antenna is the combination of a fully integrated dual band step-shorted annular ring antenna and a compact broadband multipath mitigating ground plane. The proposed antenna is compact, low cost and has a very simple easy to manufacture structure. Moreover, the proposed antenna configuration offers uniform performance across both bands. In order to validate the suitability of the proposed multi-path mitigating antenna for small satellite applications, the performance is compared against the existing multipath mitigating ground planes available in the literature. The figures of merit selected for the characterisation of multipath mitigation are front to back ratio (FBR), gain pattern slope, polarization purity, side lobe level suppression and cross polarisation gain at about and below the horizon. The overall antenna size, design complexity and commissioning have also been considered. This work also presents the design and development of a compact low cost dual band circularly polarized switched beam array antenna for remote sensing applications. The array antenna uses a low cost PIN diode and microstrip line based switching mechanism integrated to the antenna. The array provides left hand circular polarization (LHCP) with +-25 coverage and is intended for GNSS reflectometry where the weak navigation signals are picked up by the high gain antenna array after reflection from the surface of the ocean or the earth and different phenomenon such as speed and direction of the winds, and soil moisture can be estimated. Similar to the dual band multipath mitigating antenna, the measurement results of the integrated antenna array show uniform performance across both bandwidths