Dual-band Branch-line Coupler Research Articles

A 26/38-GHz Dual-Band Filtering Balanced Power Amplifier MMIC for 5G Mobile Communications

This letter presents a 26/38-GHz dual-band filtering balanced power amplifier (PA) using 100-nm GaAs process. Dual-band branch-line couplers are proposed for the balanced PA, which also engage into the dual-band input–output impedance matching and provide out-of-band rejection simultaneously. The proposed PA achieves the saturation output power ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$P_{\text {sat}}$ </tex-math></inline-formula> ) of 27.7/26.9 dBm, output 1-dB compression point (OP <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$_{\mathrm {1\,dB}}$ </tex-math></inline-formula> ) of 27.1/25.6 dBm, peak power-added efficiency (PAE) of 31.5%/22.8%, and small signal gain of 22.4/15.8 dB at 26/38 GHz. At frequencies of 12, 34, and 45 GHz, the small signal suppressions are 45, 54, and 40 dBc, respectively. In virtue of the high output power in 5G band n258/n260 and good out-of-band rejection, the proposed PA can be a potential candidate for 5G applications.

A Dual-Band Branch-Line Coupler with Ultra-Wideband Harmonic Suppression

A dual-band branch-line coupler with ultra-wideband harmonic suppression is proposed in this paper. The conventional quarter-wavelength transmission lines are replaced with π-shaped lines to achieve a dual band. In addition, ultra-wideband harmonic suppression is obtained by the frequency-selecting coupling structure (FSCS) providing three transmission zeros. The two operating frequencies are 0.9 GHz and 2.0 GHz, and the corresponding -10 dB bandwidth at 0.9 GHz and 2.0 GHz is 18.9% and 10.5%, respectively. A wide harmonic suppression band is generated from 3.7 GHz to 8.3 GHz. The simulation and measurement results are in good agreement.

Dual-Band Branch-Line Coupler Based on Crossed Lines for Arbitrary Power-Split Ratios.

Dual-band branch-line couplers with arbitrary power-split ratios are presented. The use of crossed lines at the center of the dual-band coupler enables it to independently provide different power-split ratios to the two bands. Additionally, open stubs are utilized to enhance the stopband responses. The complete design procedure with example design curves is provided. For experimental verification, three dual-band couplers with power-split ratio combinations of +3 dB () and −3 dB (), −3 dB and +3 dB, and 0 dB () and +13 dB () at 1 GHz and 2.5 GHz were designed and fabricated. The measured results are in excellent agreement with the ideal and full-wave simulated results. The measured difference of −13.3 dB between the power-split ratios of the two bands is the largest reported for a dual-band branch-line coupler.

Dual-Band/Dual-Mode Rat-Race/Branch-Line Coupler Using Split Ring Resonators

A novel dual-band/dual-mode compact hybrid coupler which acts as a dual-band branch-line coupler at the lower band and as a rat-race coupler at the higher band is presented in this paper. One of the most interesting features of the proposed structure is that outputs of the proposed coupler in each mode of operation are on the same side. This unique design is implemented using artificial transmission lines (ATLs) based on open split ring resonators (OSRR). The low-cost miniaturized coupler could be operated as a dual-band 90° branch-line coupler at 3.3 and 3.85 GHz and 180° rat-race coupler at 5.3 GHz. The proposed coupler could be utilized in the antenna array feeding circuit to form the antenna beam. The structure’s analytical circuit design based on its equivalent circuit model is provided and verified by measurement results.

Reduced-Cost Microwave Design Closure by Multi-Resolution EM Simulations and Knowledge-Based Model Management

Parameter adjustment through numerical optimization has become a commonplace of contemporary microwave engineering. Although circuit theory methods are ubiquitous in the development of microwave components, the initial designs obtained with such tools have to be further tuned to improve the system performance. This is particularly pertinent to miniaturized structures, where the cross-coupling effects cannot be adequately accounted for using equivalent networks. For the sake of reliability, design closure is normally performed using full-wave electromagnetic (EM) simulation models, which entails considerable computational expenses, often impractically excessive. Available mitigation techniques include acceleration of the conventional (e.g., gradient-based) routines using adjoint sensitivities or sparse sensitivity updates, surrogate-assisted and machine learning algorithms, the latter often combined with nature-inspired procedures. Another alternative is the employment of variable-fidelity simulations (e.g., space mapping, co-kriging), which is most often limited to two levels of accuracy (coarse/fine). This work discusses an EM model management approach coupled with trust-region gradient-based routine, which exploits problem-specific knowledge for continuous (multi-level) modification of the discretization density of the microwave structure at hand in the course of the optimization run. The optimization process is launched at the lowest discretization level, thereby allowing for low-cost exploitation of the knowledge about the device under study. Subsequently, based on the convergence indicators, the model fidelity is gradually increased to ensure reliability. The simulation fidelity selection is governed by the algorithm convergence indicators. Computational speedup (i.e., reduction in the number of EM simulations required by the optimization process to converge) is achieved by maintaining low resolution in the initial stages of the optimization run, whereas design quality is secured by eventually switching to the high-fidelity model when close to concluding the process. Numerical verification is carried out using two microstrip circuits, a dual-band power divider and a dual-band branch-line coupler, with the average savings of almost sixty percent when compared to single-fidelity optimization.

Dual-Band Branch-Line Couplers With Short/Open-Ended Stubs

Two dual-band branch line couplers with arbitrary power division are proposed in this brief. By adopting half-wavelength open/short-ended stubs in improved couplers, the dual-band operations could effectively be implemented while ensuring a compact size. Furthermore, the frequency is tunable by changing the characteristic impedance of the transmission line. For practical verification, two branch line coupler ( ${\varepsilon }_{r} = 2.65$ , ${h}= 0.5$ mm) operating at 0.9/1.8GHz and 0.9/1.57GHz are constructed in microstrip technology and tested. The measured results are in good agreement with the simulated ones.

A Novel Dual Band Branch Line Coupler and its Application to Design a Dual Band 4 × 4 Butler Matrix

A novel dual band branch line coupler (BLC) has been proposed, designed, implemented, and analyzed in this paper. A dual band 4 $\times 4$ Butler matrix (BM) has also been developed by employing the proposed BLC. To realize the proposed BLC, PI and modified PI-shaped transmission lines (TLs) as dual band TLs, with the complete derivation of the design equations, have also been introduced. The proposed BLC is equivalent to a dual band ±90° BLC and a dual band ±45° phase shifter combination and capable of performing a dual band operation for 2.3 to 4.4 frequency ratios. In order to verify the proposed approach, a dual band BLC for 1GHz and 2.85GHz frequencies has been designed and implemented. For the proposed BLC, equal power division between the output ports has been achieved with maximum ±0.2dB amplitude imbalance and a phase difference of +45°/-135°±1° at frequency 1GHz and +135°/−45°±2° at frequency 2.85GHz between the output ports for port1/port4 excitation. By employing the proposed BLC, a dual band 4 $\times 4$ BM has also been developed. Compared to the existing dual band BMs, the 4 X 4 BM offers a simpler design, compact size, and design with fewer number of components.

Design and Optimization of Dual-Band Branch-Line Coupler with Stepped-Impedance-Stub for 5G Applications

Design and Optimization of Dual-Band Branch-Line Coupler with Stepped-Impedance-Stub for 5G Applications

A Novel Dual-Band Branch Line Coupler for Dual-Band Butler Matrix

In this brief, a novel dual-band branch line coupler (BLC) for designing a dual-band Butler matrix (BM) has been proposed. To realize the proposed BLC, a unique dual-band impedance transformer (DBIT) with a derivation of closed-form design equations, capable of performing a dual-band operation for a traditional transmission line (TL) of any electrical length, has been proposed as well. The proposed BLC is different from the existing dual-band BLCs in terms of its phase difference between the output ports, which enables it to play a role equivalent to the combination of a dual-band equal power ±90° BLC and a dual-band ±45° / ±135° phase shifter. The circuit parameters analysis of the proposed BLC versus the frequency ratio has also been studied here. To verify the design method, a dual-band BLC has been designed using Keysight Technologies’ advanced design system (ADS), implemented on a Rogers 5870 for 1 GHz and 1.76 GHz operating frequencies, and then tested.

DESIGN, SIMULATION AND REALIZATION OF A COMPACT DUAL BAND MEANDERED COUPLER

Telecommunication systems increasingly require the use of miniaturized passive microwave components. One of these is the directional coupler, a four-port component intended to distribute power to two output ports, the fourth port being isolated. This paper proposes a dual-band branch-line coupler (BLC) with an extremely compact microstrip structure. The application of meandering lines as the coupler’s central connector yields dual-band operation. HFSS is used to optimize the device and to verify its transmission characteristics. This yields a design of a coupler with a footprint is 23×34.6 mm², operating at 1.65 / 3.30 GHz, with ports that can be adapted to a load impedance of 50 Ohm. To validate the model, the coupler is fabricated using microstrip technology on a FR4 substrate. A good agreement between measurement and simulation results is obtained. The coupler achieves an excellent isolation of –42.41 dB and a transmission loss of only –2.29 dB at 3.30 GHz.

Reply to “Comments on ‘A Dual-Band Port-Extended Branch-Line Coupler and Mitigation of the Band-Ratio and Power Division Limitations”’

This paper is reply to comments on a dual-band port-extended branch-line coupler and mitigation of the band-ratio and power division limitations. The author would like to thank Sinha for showing interest in the author work. The work was interestingly submitted to the IEEE TRANSACTIONS ON COMPONENTS, PACKAGING, AND MANUFACTURING TECHNOLOGY (TCPMT) almost at the same time as [3] was to the IEEE TRANSACTIONS ON INDUSTRIAL ELECTRONICS (TIE). Therefore, the discussion in these two works regarding the phase errors associated with the port-extended couplers in case of unequal port terminations is completely independent. With regards to the comments made by Sinha , we wish to make the following comments. 1) The phase error depicted in [2, Fig. 17] is valid only at the two design frequencies, which is why the two points were circled. 2) Reference [2, Fig. 17] was obtained by writing in MATLAB the equations for transmission phase found in many popular textbooks such as [4], assuming two unequal real port termination impedances. 3) The errors in [2, eqs. (24)-(27)] are not due to incorrect port terminations used in [2]. The error is possibly due to the fact that while manually obtaining a simplified version of equations used in MATLAB, R2 and R3 were replaced by the symbol Z 0 .

A dual‐band branch line coupler for LTE 0.7 GHz and LTE 2.6 GHz frequencies

In this paper, a dual-band branch line coupler (BLC) for Long Term Evolution (LTE) 0.7 GHz and LTE 2.6 GHz frequencies is designed and developed. A dual-band quarter wave transmission line (DBQWTL) capable to perform dual band operation for frequency ratio >3 is also proposed. The dual band BLC is designed by replacing the quarter wave transmission line of the conventional single band BLC with the proposed DBQWTL. By means of even and odd mode analysis, the closed form design equations of the proposed DBQWTL are obtained. Considering the implementation viewpoint of the proposed BLC, the circuit parameter analysis is carried out. The proposed BLC performs dual band operation with maximum amplitude imbalance of 0.26 dB and phase deviation of 3.07°. It is found in the comparative analysis that the proposed BLC has novelty in terms of its operating frequency ratio range.

Comments on “Systematic Design Technique for Dual-Band Branch-Line Coupler Using T- and Pi-Networks and Their Application in Novel Wideband-Ratio Crossover”

In the above paper, the authors propose a new design method for dual-band branch-line coupler. However, two errors have been found and some parameters are assigned partially. For clarification of the formulas of this design, the design equations are rededuced and the previous error equations are rectified. Then, the missing possibility is analyzed, which expands the band-ratio range. For proving the validity of this design, two simulations are implemented.

A Dual Band Branch Line Coupler With Wide Frequency Ratio

A dual-band quadrature branch line coupler (BLC) with wide frequency ratio has been proposed in this paper. A dual-band quarter wave ( $\lambda $ /4) transmission line structure with wide frequency ratio operation has also been presented here with closed-form design equations. An analysis for the BLC’s circuit parameters variations versus frequency ratio in the view of the implementation has been carried out as well. In order to the experimental verification, a dual-band BLC has been designed, implemented, and analyzed then tested for long term evolution (LTE) 0.7GHz and public safety band (PSB) 4.9GHz. The novelty of the proposed design is the wide frequency ratio of its dual-band operation, which can reach up to 11.8.

A Low-Cost Compact Planar Dual-Band 3 dB Branch Line Coupler Using an Unbalanced CRLH

In this work, a compact dual-band 3 dB branch line coupler (BLC) is designed with center frequency at 2.45 GHz and 5.08 GHz using an unbalanced composite right/left-handed transmission line. Based on the two-port ABCD parameters, the lumped equivalent circuit of the proposed TL is extracted and optimized to obtain characteristic impedance at 2.45 GHz and 5.08 GHz. The right- and left-handed characteristics of the proposed TL are examined. Incorporating the proposed TL, a dual-band BLC with 0.29λg × 0.3λg size is obtained. The frequency response has magnitude imbalance of 0.8 dB, phase imbalance of 1.8° and 160 MHz bandwidth at 2.45 GHz and magnitude imbalance of 0.81 dB, phase imbalance of 0.006° and 100 MHz bandwidth at 5.08 GHz.

Bridged-T Coil for Miniature Dual-Band Branch-Line Coupler and Power Divider Designs

In this paper, a new design method for bridged-T coil (BTC) is proposed such that it can be made equivalent to two different transmission line sections at two different frequencies. In this way, on-chip dual-band branch-line coupler and dual-band power divider designs with very compact circuit sizes can be made possible through the use of BTCs. Specifically, the proposed 2.45/5.8-GHz dual-band branch-line coupler realized using the integrated passive device (IPD) process features a compact circuit size of only $2.8~\text {mm} \times 1.4$ mm while the proposed 2.4/5.5-GHz dual-band power divider in IPD exhibits a very small circuit size of only $1.8~\text {mm} \times 1.7$ mm. To the best of our knowledge, the proposed dual-band branch-line coupler is the smallest one ever reported while the circuit size of the proposed dual-band power divider is comparable to the smallest in the literature.

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.

Comments on “Compact Dual-Band Branch-Line Coupler With Dual Transmission Lines”

The synthesis and design method for the dual-band, dual transmission line branch-line coupler in [1] involves equivalent circuit transformations that are single-banded in nature and not suitable for the dual-band operations. The proposed equivalent dual transmission line transform has been applied only in the middle of the dual-band operation frequencies and its validity has not been confirmed at the two band frequencies. As the result, the proposed circuit equivalence can be quite poor and the coupler design in [1] based on it can be quite erroneous at the dual-band operation frequencies.

Compact Dual-Band Branch-Line Coupler With Dual Transmission Lines

This letter presents a dual-band branch-line coupler with compact size and planar structure. The $\pi$ -shaped dual transmission lines structure is used to realize 90 $^{\circ}$ phase shift at two arbitrary frequencies. Explicit design equations are derived using the ABCD and admittance matrices. For verification, a prototype is designed, fabricated, and tested. The coupler has a compact size with 76% size reduction compared with the conventional circuit at the first band. The measured results are in good agreement with the simulated results.

Systematic Design Technique for Dual-Band Branch-Line Coupler Using T- and Pi-Networks and Their Application in Novel Wideband-Ratio Crossover

In this paper, a generalized analysis and design methodology of a dual-band branch-line coupler (BLC) is presented. The proposed design, although based on the prevalent method of replacement of various arms of a single-band BLC with an equivalent T-/Pi-network, simplifies the design approach by only replacing either pair of arms and therefore provides four distinct topologies. Closed-form design equations along with insightful comments are reported for all the four topologies of the BLC. A number of cases are investigated to demonstrate the effectiveness of the proposed design for equal and unequal power division ratio and band-ratio ( $= f_{2}/f_{1}$ ). As an application, a novel dual-band crossover as a cascade of BLCs is also presented. While investigating the limitations of previous designs, a strategy to obtain the crossover with so far the widest band-ratio and simple layout is also presented. An unequal power division dual-band BLC and a dual-band crossover are designed which operate at 1/2 and 1/4 GHz, respectively. These designs are validated from the electromagnetic simulations and prototypes implemented on RT/Duroid 5880 substrate.