The Non-Contacting Feeding Structures of the Printed Antennas

The feeding mechanism of the printed antenna elements via electromagnetic coupling with a printed transmission line is investigated. Three novel methods of excitation, namely proximity coupled patch antenna (PCPA), proximity-coupled radiating aperture (PCRA), and patch coupled through an aperture (ACPA), are discussed. The focus of the paper is directed toward the PCRA and ACPA antennas as a candidate elements for monolithically integrated antenna arrays (phased arrays). The main objective was to obtain a simple analytical formulas, keeping the physical comprehension of the problem. It was done using the modal field expansion under the patch, and assuming that coupling between the path and transmission line is via magnetic current in the aperture. Several samples of feeding structures are designed, manufactured, and tested on two bands of microwave frequencies (i.e. L-band: f¿ 1.06 GHz, and X-band: f¿ 10.3 GHz). The effects of feed geometry and arrangement, the inter-layer spacing and the thickness of the layers on impedance bandwidth, 3 dB beamwidth and pattern shape, are studied. Predicted values of input impedance and radiating characteristics are compared with experimental results and found to be in good agreement.