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This brief presents, for the first time, the analysis and implementation of a dual-band coupled-line trans-directional (CL-TRD) coupler. It is realized by cascading three periodically capacitor loaded coupled line segments, which are equivalent to a symmetric stepped impedance coupled line with a 180° difference between the even- and odd-mode electrical lengths. Explicit design equations of the proposed coupler were derived using the equivalent approach and the even-odd mode decomposition analysis. For demonstration, a 3-dB CL-TRD coupler operating at 0.9/2.4 GHz was designed. Under the criterion of | ${S} _{11}$ | < −15 dB and | ${S} _{21}$ | < −15 dB, the measured relative bandwidths are 37.8% and 10%, respectively, for the lower and upper bands. While for amplitude imbalance < 1 dB, the relative bandwidths are 35.6% and 8.3%, relatively, with the output ports phase differences of ± 90 ± 5°. [ABSTRACT FROM AUTHOR]

In this article, an arbitrary-phase-difference (A-PD) transdirectional (TRD) coupler is proposed and applied in the design of a flexible Butler matrix. The A-PD TRD coupler, which also features the characteristics of arbitrary power division and miniaturized size, is composed of four sections of coupled lines and four types of capacitors. Explicit equations for designing the A-PD TRD coupler were derived utilizing the even–odd mode decomposition analysis, and guidelines to obtain the circuit parameters were also given. To demonstrate the design procedure, examples of the proposed coupler are provided and the relevant studies on the coupler’s electrical parameters are conducted. By combining the proposed coupler with the TRD coupled-line-based crossovers and the −45° phase shifters, a miniaturized $4 \times 4$ Butler matrix with flexible output ports phase differences (−25°, 155°, −115°, and 65°) is implemented. It inherits the features of the TRD coupler including A-PD and compact size. At the center frequency, the measured amplitude and phase imbalances are less than 1.4 dB and 3.2°, respectively, between the output signals. Compared to state-of-the-art A-PD-coupler-based Butler matrix, the proposed structure shows a smaller size ($1.35 \lambda _{g} \times 1.36 \lambda _{g}$) and a wider bandwidth (20%). [ABSTRACT FROM AUTHOR]

This paper presents a novel coupled line 180^\circ hybrid with non-interspersed input/output ports. With the combination of a weak coupling parallel coupled line and strong coupling trans-directional coupler, a non-interspersed input/output ports coupled line 180^\circ hybrid is obtained by using printed circuit board fabrication process, and reduced substrate area is achieved. The proposed hybrid owns the features of reducing the complexity of dc biasing for the next-stage active circuits. Moreover, it requires no bond wires, via-holes, or multilayer structures. The formula of the proposed hybrid is derived, and the characteristics of the hybrid are analyzed. Two prototypes are designed to verify the concept. One is arranged with the two couplers perpendicular to each other, and the other is constructed with the two couplers arranged in a line. The measured results are in good agreement with the simulated ones [ABSTRACT FROM AUTHOR]