Design of dual/tri-frequency impedance transformer with ultra-high transforming ratio

Abstract

In this article, the design of a new dual-band impedance transformer with ultra-high transforming ratio (UHTR) is presented. The closed-form expressions are derived analytically using a lossless transmission-line theory. To practically validate the proposed design concept, two examples of dual-band transformer working at smaller and larger frequency ratios are designed for different load impedance of 500, 1000, and 1500 Ω. Finally, three prototypes of dual-band transformer with UHTR are designed, fabricated, and tested. For all these prototypes, different frequency ratios (two operating frequencies can be chosen arbitrarily) are considered. The measured return loss of the prototypes is better than 15 dB at all the operating frequencies. The measured results are matched very closely with the simulated results. This design is then extended to match a complex load at two different frequencies. The multi-band characteristic is obtained by decomposing a shorted stub into a stepped impedance section of the proposed structure. With the necessary derivation and analysis, a tri-frequency matching network is designed for a transforming ratio of 10.

A compact tri‐band impedance transformer for frequency‐dependent complex loads

“…To make the tri-band impedance transformer achievable, the maximum ratio of Z e and Z f can be taken as 7.0 (Z e = 140 Ω, Z f = 20 Ω). Therefore, the values of m should be more than 1.59 according to (7) and (8). So far, the design parameters of the tri-band impedance transformer can be determined according to the closed form design equations above.…”

“…[4][5][6][7] However, tri-band impedance transformer still remains a technical challenge, especially for matching the frequency-dependent complex loads. The tri-band impedance transformer with ultrahigh impedance transforming ratio 8 or using coupled line 9 is preferred for the real impedance loads, and it is unsuited for the frequency-dependent complex impedance of active integrated devices. For Nghiem et al, 10 the impedance matching network is unable to work at arbitrarily chosen desired frequencies.…”

Design of a tri‐band 180‐degree directional coupler with spurious suppression based on extended pi‐shaped microstrip line

“…To face the challenges presented by the wireless communication industry in the current scenario, it is crucial to design microwave components with features such as compactness, harmonic suppression, multifrequency operation, and good out of the band rejection performance. Especially, the design of multiband components is gaining a lot of interest because of their inherent ability to simultaneously operate at different frequencies and thereby saving crucial on‐board space.…”

“…The π‐shaped unit with resonators has been used for the tri‐frequency RRC design . Recently, some techniques have been reported for tri/quad‐band operation such as concentric dual split ring slots, cross‐shaped with a shunt stub, extended Pi‐shaped coupled line, and modified H‐shaped . This techniques can be employed for the realization multiband microwave circuits such as power divider, branch line balun and hybrid couplers.…”