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In this paper, two 50Ω terminated rat-race hybrid couplers based on uniform folded structures are proposed for equal division of power. The proposed designs are of simple in geometry and have an area of only one-fourth of the conventional coupler. The first technique is two-fold double section topology operating at 1.77 GHz designed with the conventional impedance ratio of √2 between port and transmission line which exhibits good in-band characteristics and requires a minimum track width of 0.8 mm. The second technique is stub-loaded double section topology where the novelty lies in deploying impedance matched stubs which avoids high impedance lines by maintaining an impedance ratio less than 2 between port and transmission line. In addition to good passband characteristics, it also suppresses higher harmonics up to 6.3f0 and requires a minimum track width of 0.41 mm which makes it easy for realization. The bottom line of both designs is to achieve extreme structural simplicity without using high impedance transmission lines of more than 100Ω, narrow tracks less than 0.4 mm, lumped elements, and via holes. The prototype of the proposed coupler is fabricated and the simulated results are validated using measurements. [ABSTRACT FROM AUTHOR]

A single-layer band-stop frequency selective surface (FSS) with miniaturized periodic element is proposed in this paper. The unit cell size of the proposed FSS is 0.047λ0 where λ0 stands for free space wavelength. The proposed unit cell consists of hexagonal concentric rings connected as a single loop by altering it by flexuous segment. Increased electrical length and effective space utilization achieve a unit cell dimension of 7.29 mm × 12.63 mm. In addition, the proposed FSS exhibits a stable response for TE and TM modes of polarization and oblique incidences. Therefore, the proposed design ensures angular and polarization independence. The full wave EM simulation of the proposed hexagonal unit cell FSS is carried out and then fabricated using the PCB method. Simulated results are validated using different measurements. [ABSTRACT FROM AUTHOR]