Microwave broadband wide-scan antenna arrays are typically implemented resorting to vertical arrangements of printed circuit boards (PCBs). Here, we propose a planar solution realized with a single multi-layer PCB, with consequent reduction in cost and complexity of the array. It consists of an array of connected slots backed by a metallic reflector and loaded with superstrates. Artificial dielectric layers (ADLs) are used in place of real dielectrics to realize the superstrates, as they are characterized by very low surface-wave losses. For the unitcell design we developed an analysis tool based on closed-form expressions and thus requiring minimal computational resources. Finite-array simulations are also performed by generalizing the analysis method to account for the truncation effects. The presence of the ADL superstrate allows reducing the distance between the array plane and the backing reflector while maintaining good matching performance. A realistic feed structure is also proposed, which consists of a microstrip line connected to a coaxial feed. Such a solution does not require balanced-to-unbalanced transitions, which often limit the achievable bandwidth. The proposed structure achieves in simulations more than an octave bandwidth (6.5 to 14.5 GHz), within a scanning range of ±50 • in all azimuth planes.

An all-electronic, I/Q-mixer-based interferometric technique to reduce measurement noise in the characterization of extreme impedances is presented. The proposed technique employs a standard vector network analyzer, an arbitrary waveform generator and an I/Q-mixer chain to generate a very stable cancellation signal. This hardware implementation enables frequency scalability, due to the large commercial availability of the mentioned components, and high stability, speed and repeatability, due to the fully electronic approach. The proposed technique is embedded in a scanning microwave microscopy (SMM) setup to demonstrate a more than 50% noise reduction in the measurement of dielectric materials.

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