International Journal of Microwave and Wireless Technologies最新文献

This article presents the modeling and realization of a compact substrate integrated coaxial line (SICL) based butler matrix operating at 5 GHz for beam-forming applications. The proposed 4 × 4 butler matrix is developed using SICL-based hybrid coupler, crossover, and phase shifter. A compact 90∘ coupler comprising of center tapped unequal stubs is designed to enhance the size reduction as well as to extend the out of band rejection. Wideband SICL-based crossover operating from DC to 10 GHz is conceived for the proposed butler matrix using a plated through hole as transition. The SICL crossover features very high measured isolation of 65 dB owing to the reduction in coupling between the two signal paths within a lateral footprint of only 0.034 $lambda_g^2$. A meandered SICL-based line is used in order to provide the necessary 45∘ and 0∘ phase shift to realize the butler matrix. The fully shielded and self-packaged compact 4 × 4 SICL-based butler matrix is fabricated and experimentally validated to operate at 5 GHz.

A reflective linear-to-circular polarization converter based on dual frequency-selective structures (FSSs) is proposed and modeled to exhibit efficient wideband performance. The design utilizes a diagonal array of two connected circular patches as an effective anisotropy with regular current distribution in several successive resonances, resulting in orthogonal reflections with a 90° phase difference. The relevant upper-part characteristic is improved by using two separate square patches as a high-frequency resonator. This design with distinct key parameters leads to high overlapping and then excellent bandwidth and efficiency over 105% and 96%, respectively, with an axial ratio below 1.7 dB. A sophisticated equivalent circuit-admittance model including effective mutual coupling between two FSSs is extracted, featuring closed-form equations for the physical design. Different dielectric constants are studied on the converter, which offer controllable coverage in the range of 3–24 GHz (S, C, X, Ku, and K bands), variably. For actual validation, a very thin (0.04λ0 at 3.65 GHz) 8 × 8 array prototype was built and measured at different incident angles, showing angular stability up to 45° in 78% (6–14 GHz) bandwidth. This converter has potential applications in communication, spectroscopy, detection, and imaging in micro-, mm-, and THz-wave regions.

This paper proposes fractal-inspired array antennae for wideband applications. The proposed antennae have a resonance frequency range of 20–40 GHz. The modified fractal antennae are fabricated with a height of 1.6 mm, substrate width, and length of 100, 50, 25, and 18.75 mm2, and a simulated result shows that the gain is increased to 11.04, 11.9, 8.4, and 6 dBi, and the designed antennae radiate power with directivity of 11.3, 13.4, 9.29, and 7.17 dBi concerning proposed designs A, B, C, and D, respectively. The proposed antennae with 5G New Radio (NR) bands have more radiation concerning resonate frequencies in the 20–40 GHz range with Φ = 0°, Φ = 90°, and θ = 90°. Moreover, the bandwidths for applications covered in the 5G NR and sub-6G are 1.92, 0.73, 0.7, 2.4, 1.3, 5.3, and 1.26 GHz, and 3.4, 3.7, 2.67, and 4.65 GHz, and 2, 3.5, and 1.57 GHz, and 2.5, 1.5, and 1.0 GHz with the maximum return loss of 37 dB, 32.8 dB, 31.2 dB, and 23 dB with corresponding resonate frequencies as 21.5, 27.6, 33, and 27.6 GHz concerning designs A, B, C, and D, respectively. The proposed antennae have been implemented and validated using Computer Simulation Technology (CST), Vector Network Analyzer (VNA), spectrum analyzer, and power sensor.