In this paper, a novel three-port antenna structure, named 180 antenna hybrid, is proposed and demonstrated. This structure is composed of a Wilkinson power divider with the isolation resistor replaced by an aperture-coupled patch antenna. The equivalent series impedance of the antenna can be adjusted to the required one by properly choosing the dimensions of the patch and the coupling aperture. When a signal is fed to the balanced port of this antenna hybrid, the power is equally split, with equal phases, to the two unbalanced ports. No power is radiated out from the antenna. In the other hand, a signal received from the antenna will be split with equal power but 180 phase difference to the two unbalanced ports. The balanced port is an isolation port. The measurement results showed good agreement with the characteristics to be designed. Three applications of this 180 antenna hybrid are introduced, that is, a balanced mixer, an active transmitting antenna, and a dual-radiation-mode antenna array. The balanced mixer was constructed with diodes directly mounted on the two unbalanced ports of the antenna hybrid. The LO signal is fed from the balanced port and RF signal is received from the antenna. The active transmitting antenna was implemented with feedback configuration. The route from one of the unbalanced port to the balanced port of the antenna hybrid was used as the feedback path. A locking signal may be injected from the other unbalanced port. Finally, through a three-quarter-wavelength microstrip line, the balanced port of the antenna hybrid was connected to another aperture-coupled patch antenna to form a dual-radiation-mode antenna array. The in-phase and out-of-phase radiation patterns of this two-element array can be obtained from two unbalanced ports of the antenna hybrid, respectively.

This paper proposes a new circuit-fed 2-D amplifying array architecture using the multi-ported aperture-coupled patch antennas. The power distribution achieved by this array is formed by stacking three kinds of basic cells repeatedly. Each cell, which serves as a radiator and also a power relay, has a multi-ported patch antenna and one or two amplifiers. The signal transmission coefficient of the cell from the input port to the output port is designed with a power level of 0 dB and a phase of 360. An X-band 4 3 element array with uniform amplitude distribution is demonstrated. The measured results, such as the antenna gain and the radiation patterns, agree very well with the predicted ones, due to the precision design of the basic cells. The measured gain of the antenna array is 27.7 dBiA at the frequency of 10.4 GHz on the H-plane, with a half-power beamwidth of 14 in the H-plane and 16 in the E-plane.