Phase-Conjugated Arrays Using Low Conversion-Loss Resistive Phase-Conjugating Mixers and Stub-Loaded Patch Antennas

A 1-D four-element and 2-D eight-element phase-conjugated retrodirective arrays employing low conversion-loss resistive field-effect transistor mixers and stub-loaded patch elements are proposed. The mixer, systematically designed using a multi- harmonic loading technique, offers a low 5.2-dB conversion loss at a 4.5-dBm local oscillator power level. The stub-loaded patch element is a square patch with a capacitive open stub loaded at each of its four corners, leading to patch-size reduction, lower mutual coupling between adjacent elements, and broader beam width. With the same element spacing of half a free-space wavelength at 5.8 GHz, the mutual coupling is suppressed by 3.1 and 3.3 dB in the E- and if-planes, respectively, when compared to the conventional square patches. Within an angle of plusmn60deg normal to the arrays, distinct linearly polarized retrodirectivities in terms of pattern deformations are experimentally confirmed for both the H-plane of the 1-D array and both E- and H-planes for the 2-D array. Additionally, circularly polarized retrodirectivity are also experimentally confirmed for 2-D arrays.