Small dimension antenna array element for full duplex communication system

Microstrip antennas (MSA), due to their small dimensions and weight, and low cost, are widely used in communications. They are especially beneficial when used in an array. The main shortcoming of the MSA is narrow bandwidth. Methods of increasing bandwidth are not completely satisfactory. The multi-band MSA, using several microstrip radiating elements, is a good solution of the problem. It is convenient to place radiating elements one above the other, where the surface of the low-frequency radiating element is a reflector for the high-frequency one. In a full duplex communication system, a single antenna is usually used; however, the result can be increased cost and poor mass and overall dimensions. The paper presents an improved design of MSA element for full duplex communication systems. Separate excitation of the lower and upper radiating elements lets the narrowband of each element to be used as a positive factor. The microstrip resonators act as band-pass input/output filters for receiver/transmitter. It is shown that a two band microstrip antenna with separate excitation of radiating elements can be used in communication systems as a single antenna element or as an array element.