The design of miniaturised linear arrays by using isotropic lenses with reduced complexity is addressed. The problem at hand is formulated as a global optimisation one, then solved by means of a computationally-efficient customisation of the system-by-design (SbD) paradigm suitably integrated with the quasi-conformal transformation optics method. To yield arbitrary transformation geometries with a limited set of degrees-of-freedom and to reduce the lens complexity, while guaranteeing the same radiation performance of a larger reference aperture, a spline-based description of the lens shape is adopted. Representative numerical results are reported to assess the effectiveness as well as the computational efficiency of the proposed SbD-based approach.

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Retro‐directive antenna arrays are capable to reflect back an incoming signal in source direction just like corner reflectors. Retro‐directive antenna arrays do not use complex and expensive phase shifters or smart antennas to steer their beam. These arrays steer beam autonomously in source direction by reversing progressive phase induced by incident signal. Two basic designs of retro‐directive antenna array are Van Atta array and Phase Conjugating array. A simplified design for phase conjugating array is proposed in this article. Moreover, RF measurement and testing in Lab environment need special schemes to cater for issues of multipath, far field reflections, and mutual interference. Therefore, a specially designed lab environment testing methodology is proposed and validation of retro‐directive response of developed phase conjugating array using proposed testing methodology is also presented in the article.