Branch-line Coupler Structure Research Articles

A Substrate Integrated Gap Waveguide Based Wideband 3-dB Coupler for 5G Applications

A wideband 3-dB coupler using substrate integrated gap waveguide (SIGW) is proposed based on the principle of the branch-line coupler structure. The SIGW coupler design is comprehensively studied. It is found that SIGW conducting ridge vias play a significant role and have a strong impact on the cavity resonance, passband, and impedance matching. A prototype of the proposed SIGW coupler is fabricated and tested, and the measured agrees well with the simulated. The coupler, better than the reported, has a passband of ~5 GHz from 23.59 to 29 GHz with the isolation above 20 dB, covering the 24.25–27.5-GHz and 27.5–28.5-GHz frequency bands of 5G.

A Dual-Band Port-Extended Branch-Line Coupler and Mitigation of the Band-Ratio and Power Division Limitations

In this paper, enhanced designs of port-extended branch-line coupler (BLC) are presented. Initially, the analysis of the conventional dual-band port-extended equal-division BLC is presented to deduce its operation from Riblet’s viewpoint. Subsequently, it is shown that extending the Riblet’s concept to dual-band design results in a novel dual-band BLC with arbitrary power division ratios. It has also been identified that the proposed design possesses a free design variable that allows realization of BLC with higher band-ratio. Furthermore, another BLC structure, capable of achieving enhanced band-ratio, utilizing two-section transmission line at each port is also proposed. All the reported design equations are in closed form and are very simple and do not go beyond a second-degree polynomial. The effectiveness of the proposed technique is demonstrated through test cases for equal and unequal power division ratio and for numerous band-ratio ( $= f_{2}/f_{1})$ . The good agreement between the electromagnetic simulated results and the measured results from the two unequal power division BLC prototypes, on Rogers RO4003C substrate, operating at 1.2 GHz/2.52 GHz and 1 GHz/2 GHz validate the proposed approach.

90° branch-line Coupler with Reconfigurable Output Power Ratios

This letter introduces a new 90° branch-line coupler with reconfigurable output power ratios (90° BC-ROPR). Unlike a conventional branch-line coupler structure, each arm of the proposed 90° BC-ROPR is defined by an asymmetrically coupled-line, and its characteristic impedance depends on the configuration of the coupled-line. The main problem that challenged this structure was unwanted loop resonance from the inner transmission lines which form a loop in a disconnected configuration. The proposed structure was designed to obtain 1:1 and 4:1 output power ratios at 3 GHz. Both the simulation and measurement results confirm that the proposed branch-line coupler successfully dealt with the loop resonance and achieved excellent performance. © 2013 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:1878–1881, 2013

Design method for quasi-optimal multiband branch-line couplers

In this article, the design approach, the implementation, and experimental results of multiband branch-line couplers operating at arbitrary frequencies are presented. The conventional branch-line coupler structure is adapted to multiband operation by shunting its four ports with multiband reactive networks. The performance of the proposed multiband couplers is theoretically analyzed and optimized through the even-odd mode circuit analysis. Dual-band (2.4-3.5 GHz), triple-band (1.5-2.4-4.2 GHz), and quad-band (1.5-2.4-3.5 GHz) microstrip branch-line couplers have been realized and tested to verify the design method. The good experimental results (input return loss greater than 15 dB and amplitude imbalance lower than 0.7 dB) show excellent agreement with theoretical and simulated ones, thus validating the proposed approach.

An Asymmetric Arbitrary Branch-Line Coupler Terminated By One Group Of Complex Impedances

A novel arbitrary asymmetric branch-line coupler structure terminated by one group of complex impedances is proposed. Two left ports of the proposed branch-line coupler are terminated by equal arbitrary complex impedances, and the other two right ports are terminated by equal real impedances. Arbitrary power division ratios are feasible for the proposed structure. Using rigorous even- and odd-mode analysis and scattering parameters theory based on complex impedances, the closed-form design formulas for designing the proposed branch-line coupler is obtained. To validate the proposed structure and the given design equations, a microstrip branch-line coupler operating at the center frequency of 2.5GHz and terminated by 20 and 30 − 6j Ohm impedances is designed, simulated and measured. There is a good agreement between the simulated and measured results.

Dual-Band Branch-Line Coupler With Port Extensions

A new branch-line coupler structure with port extensions is proposed for the dual-band operation. The conventional branch-line coupler structure is adapted to the dual-band operation by inserting a transmission line section at the input ports and modifying the branch parameters. The dual-band performance of the proposed coupler is verified theoretically through the rigorous microwave circuit analysis and the exact design equations are derived in concise form. The design, simulation, and measurement results validate the dual-band capability of the proposed coupler with the same quadrature phase relation between the two band frequencies.

Dual-Band, Unequal Length Branch-Line Coupler With Center-Tapped Stubs

A new dual-band branch-line coupler scheme is proposed based on the unequal length branch-line coupler structure and the center-tapped stub lines. The unequal length structure reduces the size of the dual-band branch-line coupler using center tapped stubs. Also, it offers the possibility of the stubless dual-band operation for some special cases, and the same phase relation can be obtained between the two output signals at the two frequency bands.

Dual-band, cross coupled branch line coupler

A novel branch line coupler structure is proposed with application to the dual band operation. The proposed structure has additional cross coupling branches to the conventional branch hybrid coupler. Additional design freedom can be obtained using the proposed scheme, which can serve many useful purposes such as the dual band operation of the branch line coupler.

A PIN diode controlled variable attenuator using a 0-dB branch-line coupler

We describe a simple PIN diode controlled variable attenuator that employs a 0-dB branch line directional coupler. The response of the attenuator was measured between 1.3 GHz and 2.6 GHz. At the center frequency, the attenuation monotonically varied from 0.7 dB to 23 dB with the control voltage, and the distributed branch-line coupler structure resulted in low input reflection. Our attenuator is easier to design, smaller in area than a double hybrid coupled attenuator, and has comparable or better reflection and attenuation performance characteristics.