In this paper, we propose a newly enhanced Doherty combiner by adding a 180° transmission line to the stage of the peaking amplifier of a typical Doherty combiner such that the designer can easily construct a combiner having a phase deviation to be turned on within the intended bandwidth. Given such characteristics, the proposed structure provides wider phase bandwidth and better performance with respect to power combining rate than the conventional structure does. We introduce formulas for the design variables of the added transmission line and also demonstrate its validity through circuit design and experiment.

In this article, we suggest a new design method of the unequal Wilkinson power divider. The line impedances of the proposed formula are decided after the resistor value is arbitrarily chosen, while the isolation resistor of the conventional unequal Wilkinson power divider is derived by the power ratio. Therefore, using the proposed formula, the more accurate resistor value is applicable to the Wilkinson power divider, and a narrow line width is improved up to 46.5% in 10:1 Wilkinson power divider. The proposed design formula of the Wilkinson power divider is derived, and the proposed formula is verified by the fabrication and measurement results. © 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 58:2450–2452, 2016

A wideband planar 180 hybrid is proposed for arbitrary power division ratios and implementing cascaded planar structure. In addition, the proposed structure not only has the same function as the conventional ring hybrid, but also has a planar cascade connection when connecting other components because the output ports have same direction. The proposed planar 180 hybrid consists of two 3 dB couplers, and 4 transmission lines (TLs) with symmetrical TLs connected in series with different impedances of ZA and ZB. The design theory of the proposed structure is based on a cascaded multiport connection form, converged from transmission matrix to S‐parameter, and the ratio of ZA and ZB impedances is derived for wideband performance. The design equations are verified as the measurement results of the magnitude and phase characteristics. The proposed structure, regardless of whether 2 TLs are connected in cascaded form, has a 29% reduced area compared with the conventional ring hybrid.

This article proposes the stepped impedance line Wilkinson power divider (SIL WPD) and extracts the design formulae of SIL WPD. In the process of forming the WPD and executing a simulation based on the calculated design parameters, this study found that the SIL WPD improves stop‐band performance compared to the conventional one. In addition, it is useful in reducing the size due to the characteristics of SIL. Finally, the consistency of the simulated and measured results confirmed the validity of the SIL structure. © 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 58:1607–1610, 2016

A novel method of designing a group delay equalizer consisting of a typical 3‐dB hybrid coupler combined with one of newly proposed 4 types of resonator is presented. It is designed by applying the phase obtained from the reflection coefficient between the 3‐dB coupler and the proposed resonator to the group delay formula. Once the resonance frequency with the group delay as the peak is set to form a desired band by setting the parallel and series resonance frequencies, each component value of the proposed equalizer is obtained. In order to improve the group delay bandwidth, the proposed equalizers with different target frequencies are connected as cascaded. One of the proposed 4 types of equalizers was implemented using open and short stubs due to the fabrication limitation of lumped components, and its measurement results showed that the insertion loss is under −1 dB, and the group delay is 4.5 ns with ±1.5 fabrication error. This implies that the measurement results were well matched with the design method of the proposed equalizer.