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SWITCHABLE CONCEPTS


“Simple” switching between antenna elements, such as among single patches or a combination of patches, can be an effective way of steering the antenna beam, especially for operating frequencies like L-band. These concepts involve only a small number of active/passive RF components (LNA, PA, RF phase shifters) but usually require high performance RF switches. A typical solution is shown in the figure below: this is a switchable bidirectional antenna frontend in L-band (circular polarization) for INMARSAT systems for land-mobile platforms. The antenna has a diameter of approximately 40 cm and a height of 20 cm; this is rather large for land mobile applications but acceptable in maritime applications. In this set-up, eight (8) single patches stand alone and seven (7) combinations of paired patches (equipped with fixed phase shifters) are applied, each pair being the zenith patch and one of the inclined patches.