Zeroth-Order Self-Oscillating Active Integrated Antenna Using Cross-Coupled Pair

By ingeniously integrating a pair of zeroth-order resonators (ZORs) with a cross-coupled pair, for the first time, a novel zeroth-order self-oscillating active integrated antenna (AIA) is developed. Unlike the conventional feedback oscillating AIA, the new configuration is realized by, respectively, inserting a ZOR into each of the feedback paths of the cross-coupled pair to satisfy the Barkhausen criterion, and hence stabilize the oscillation. A self-oscillating AIA operates at the UHF radio frequency identification (RFID) band was demonstrated as a proof of concept. Benefitting from the infinite-wavelength property, the embedded ZORs are electrically large and capable of providing efficient power radiation into space. The oscillation parameters, meanwhile, remain good, thanks to the inherent high-quality factor property of metamaterial resonators. Without relying on ground radiation, the new design achieves good radiation and oscillation performances at the same time, hence adding extra flexibility on shaping the radiation pattern. According to the experimental results, the developed AIA, oscillating at 0.92 GHz, features a high dc-to-RF conversion efficiency of 52%, a moderate effective isotropic power of 8.9 dBm, and a low phase noise of -124.7 dBc/Hz at a 1 MHz offset from the carrier frequency. The design principle and experimental demonstration are thoroughly discussed.