This paper proposes four methods and empirical formulas of adjusting characteristic impedances for thin-metal mesh transmission lines. The characteristic impedances are discretely adjusted by changing the number and the size of unit meshes, which provides macro-tuning capability, and the discrete values can be tuned more precisely by varying the thin-metal line width and the aspect ratio of mesh geometry. The validity of proposed methods is confirmed by full-wave numerical simulations, and the simulated impedance variations are well-described by our empirical formulas. For further verifications, 26 distinguished samples of thin-metal mesh transmission lines and a 28-GHz thin-metal mesh antenna are fabricated, and their characteristics are measured in millimeter-wave spectrums. The measured results confirm that the proposed methods and empirical formulas can provide accurate and more flexible design rules for impedance adjustment, which allows potential advances in display-integrated antenna applications.
This paper proposes a pattern distortion coefficient as a new figure of merit to quantitatively evaluate both mutual coupling and pattern distortions in multi-antenna systems. The proposed coefficient is defined as a cross correlation between unaffected and affected far-field patterns of antennas under test, and the input patterns are weighted using a Gaussian function to consider the target operation angle. The feasibility of the proposed approach is validated using a two-antenna system composed of an inverted-F antenna and a microstrip patch antenna, and the amount of mutual coupling is adjusted by changing the distance between the two antennas. The evaluation is further extended to a single-antenna system with a conducting wall that produces strong platform effects with serious pattern distortions. The results demonstrate that the proposed figure of merit provides quantitative insight into the amplitude and phase distortions of far-field patterns that can be caused by both mutual coupling and platform effects.
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