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This paper presents a novel design of ultra-high transforming ratio quad-band impedance transformer. This transformer is capable of matching a very high real load ( Z L ) to the source impedance ( Z S ) of 50 Ω at four different operating frequencies. The proposed structure is constructed using two series transmission line separated by a H-shaped network. The analytical relationship between various design parameters are obtained using ABCD matrix method to provide a accurate solution. To validate the derived formulas, two prototype of the quad-band transformers with impedance transforming ratios of 10 and 20 are designed, fabricated, and tested. The measured return loss is greater than 15 dB at all operating frequencies. The measured results are consistent with the simulated and theoretical calculations. [ABSTRACT FROM AUTHOR]

In this paper, a 3 dB wideband branch line coupler with reduced size and harmonic suppression is presented. New multiple asymmetric π -shaped, cross and T-shaped transmission line techniques are used to reduce the physical size of the coupler. At the operating frequency of f 0 = 0.9 GHz, the fabricated coupler achieves 15 dB return loss bandwidth of 44.4% with a size reduction of 76.3%. The designed coupler has insertion loss better than 3.6 dB with a magnitude balance of 0 ± 1 dB over the frequency band 0.67–1.05 GHz. In addition to compact design, the unwanted harmonics are well suppressed up to 4 f 0 with a level better than 20 dB by maintaining good agreement between the measured results and theoretical predictions. [ABSTRACT FROM AUTHOR]

In this article, a novel transmission line model consisting of open stubs and a one-end connected coupled line is introduced as an alternative to the standard quarter wavelength transmission line (QWTL). The new transmission line unit is used to realize a highly compact branch-line balun. Even and odd mode analysis is employed to extract the closed-form design equations. To substantiate the theoretical analysis, a branch-line balun with f 0 = 0.9 GHz is implemented on a biodegradable substrate material and tested. The developed prototype is having a relative circuit area of 11.2% of the conventional balun. The measured results exhibit that the return loss is better than 20 dB. A good match is found between the simulated and tested results. [ABSTRACT FROM AUTHOR]

This letter presents a novel design approach for implementation of miniaturized quad-band branch-line crossover. To achieve quad-band operation, each 90° microstrip-line of a single-band crossover is replaced with a novel quad-band transmission-line. The proposed structure is developed by connecting one coupled-line between two series transmission-lines. The even–odd mode technique is applied to derive closed-form formulas. For experimental verification, a quad-band crossover operating at 0.9 GHz, 2.48 GHz, 3.82 GHz and 5.4 GHz for GSM, WiFi, 5G and WLAN applications, respectively, are designed, fabricated and demonstrated. The measurement results of the fabricated prototype at four distinct frequency bands exhibit similar characteristics to that of a conventional single-band prototype. In addition, the fabricated prototype achieves a size miniaturization of 67.35% when compared to the conventional single-band crossover. [ABSTRACT FROM AUTHOR]

A compact high-isolation self-diplexing antenna is designed on a single-layered substrate integrated waveguide (SIW) cavity for dual-frequency communication in C-band. The antenna design procedure is straightforward. The antenna is backed by an SIW cavity for possible low back-lobe radiation and easy circuit integration. One rectangular and one triangular patch are created on the top-side of the SIW cavity to radiate at 4.18 GHz and 7.8 GHz respectively. Two planar inset-feed lines orthogonal to each other, are employed to excite the resonator. The inset depths of the feedlines are designed to obtain low interference and high isolation. The antenna achieves peak gain of 5.88 dBi and 6.62 dBi at lower and upper resonant frequencies respectively. The antenna supports independent frequency tuning-design and easy frequency-ratio control. The proposed design is fabricated on a RT/Duroid 5870 substrate and is characterized for validation. [ABSTRACT FROM AUTHOR]