Abstract
The paper describes the process of designing a dual-polarised linear antenna array with enhanced port-to-port isolation, with the example of a four-element array with isolation better than 60 dB for the U-NII 5.15–5.925 GHz band. As a single antenna, dual-polarised electromagnetically coupled microstrip antennas were used with port-to-port isolation not exceeding 25 dB. A significant improvement in the isolation of the array was achieved thanks to the application of a dedicated feeding network. On the basis of theoretical analysis, a mathematical model describing port-to-port isolation was developed. Circuit and full-wave simulations were carried out to show the influence of electromagnetic couplings between antennas and/or the microstrip lines of the feeding network and the selection of phase shifters/power dividers on the isolation. The fabricated prototype is characterised by a gain of about 14 dBi, polarisation purity of at least −27 dB within the main lobe and close to expectations isolation better than 57 dB within the whole operational band.
Highlights
Dual-polarisation antennas with high port-to-port isolation have wide applications in contemporary radiocommunication systems in order to increase their performance in variable propagation conditions.In case of microwave radar sensors, the sensitivity strongly depends on isolation between the RX input and TX output [1,2,3]
In order to verify the influence of mutual couplings between the radiators and feeding network on port-to-port isolation, a full-wave simulation was performed for two versions of antenna construction
The article describes in detail the designing of dual-polarised linear antenna arrays with increased port-to-port isolation based on the example of a four-element array dedicated to the 5.15–5.925 GHz U-NII
Summary
Dual-polarisation antennas with high port-to-port isolation have wide applications in contemporary radiocommunication systems in order to increase their performance in variable propagation conditions. Sensors 2020, 20, 6105 antenna arrays could be achieved by applying dedicated feeding networks that utilise compensation of the crosstalk between the array ports by means of the pairwise anti-phased feeding technique where couples of radiators which are the image mirror one of another are fed by currents shifted by 180◦ in the phase [13,14,15,16,17,18] The application of this technique contributes to an increase in isolation to over 50 dB [16,17,18]. Scattering parameters and radiation patterns of the prototype have been verified experimentally
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