Compact Single and Dual-Band Branch-Line Coupler with Effective Fractional Bandwidth for Wireless Communication Systems

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.

This article presents a compact dual-band (DB) branch line coupler (BLC) with different power division ratio at arbitrary two frequency bands. In this article, we add a technique to satisfy transmission lines of conventional BLC with different impedance at two bands, while they are transformed to π-type equivalent circuits. The design equations for DB BLC with different coupling coefficients at two bands are given. Furthermore, folded shape of shunt lines make about 77% circuit dimension comparing to conventional single-band BLC. A DB BLC operating different power division ratio at 0.9 and 2.0 GHz is demonstrated in excellent agreement with both circuit simulation and experimental results. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52: 1476–1480, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.25258

A new Dual band branch line coupler (BLC) using coupled transmission lines that can operate at two arbitrary frequencies, is introduced. The analysis of the structure is based on the even-odd mode analysis of conventional BLC as well as a new equivalent circuit which composed of a coupled transmission line and two transmission lines. This new dual band BLC has miniaturized size and planar structure. For verification purposes, simulated results of a micro-strip branch line coupler that is designed for 900/2000 MHz are included.

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.

The design of a compact dual‐band (DB) branch line coupler (BLC) using composite right/left‐handed (CRLH) transmission lines (TLs) is described. By properly choosing the parameters of the CRLH TLs, the structure yields phase responses of π /2 and − π /2 at two arbitrary operating frequencies. Employing this structure, a DB microstrip BLC operating at 0.93 and 1.78 GHz is achieved. The size of the proposed DB BLC is significantly compact, at 34.4% of the previous DB BLC when they are both designed using CRLH TLs for the same DB frequencies. The simulated and measured performances of the proposed DB BLC are reliable compared with those of the previous DB BLC.

Branch line coupler with dual band is proposed with combination of Pi and T stub lines for Global Positioning System (GPS) (1.2276 and 1.5754 GHz) and satellite applications (3.7 – 4.2 GHz). Some degree of freedom is used to provide flexibility in choosing the different characteristic impedances and electrical lengths for desirable frequency ratio. Compact size achieves by the features of Pi and T stub lines. The quarter wave transmission line is converted into Pi and T shaped stub lines which provide the efficient and better impedance matching. With the help of cascading it enhances bandwidth of the branch line coupler. It operates at the center frequency of 1.36/3.98 GHz and uses FR4 epoxy substrate with dielectric constant 4.4.

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.

The implementation of microstrip nonuniform transmission lines (MNTLs) for dual-band branch-line coupler design is presented in this study. The proposed structure demonstrates dual-band performance, low insertion loss, and compact size in comparison with other prior proposed dual-band branch-line couplers. The current work fabricates an experimental dual-band branch-line couplers working at 0.9/1.8 GHz. Employing the stubless branches also leads to circuit miniaturization and achieves an overall size reduction up to 64.4%, compared with conventional stub tapped dual-band couplers. Also, stubless dual-band operation of the coupler causes the same phase relation between the two output signals at the two frequency bands. The measured results validate good dual-band performance.

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.

This paper presents a novel dual band coupler design that can operate at two frequency bands. It is accomplished by modifying the length and impedance of the branch lines in the conventional structure. Open stubs are used to achieve dual band branch line coupler with compact size and improve the performances. The dimensions of a conventional BLC “Branch Line coupler” occupy large area, according to the length of the transmission line which is always (g/4 of the operating frequency, ( is so long at low frequencies. When we use open ended stubs the dimensions of the new BLC is reduced compared to the conventional design. The proposed model was shown to reduce the size of the dual-band BLC around 61% based on the proposed topology. It was designed and simulated using EM solver tools for both DCS and WIMAX systems. The final optimized microstrip coupler was fabricated and measured. The simulation and measurement results are in good agreements.

This article proposes an analytical design methodology for dual-band hybrid couplers and baluns structures for any arbitrary frequency ratio using a stub-loaded transmission line. An analysis of changing the impedance behavior of the stub, is carried out for the two bands of operation, which along with a dispersive analysis, emphasizes certain conditions where the existing methodology is not applicable. In addition, an extra degree of freedom has been included to increase the solutions for a given frequency ratio, thus providing greater flexibility and feasibility of the proposed structure. The design methodology is experimentally validated with the design and fabrication of dual-band branch-line and rat-race couplers for various commercial frequency bands. © 2011 Wiley Periodicals, Inc. Int J RF and Microwave CAE , 2011.

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.

In this paper, a novel design approach for significant size reduction of a class of dual-band branch-line coupler (BLC) by use of a transmission line model loaded with a folded-T-type stepped-impedance-stub (FTTSIS) is proposed. At the first step, by loading FTTSIS at the middle of each branch instead of stepped-impedance-stub (SIS) in the conventional branch-line coupler, a compact dual-band BLC with same performance that is about 65% of the conventional one is achieved. Then by mirroring the FTTSISs of 35Ω lines inside the inner space of the proposed structure, miniaturized dual-band BLC that is only 30% of the conventional dual-band BLC operating at same WLAN frequencies is obtained. The proposed structure is then fabricated and measured. The measurement results show good agreement with the theoretical ones.

This paper presents the design and analysis of multi-section dual band branch line coupler (BLC) using meta line structures. This BLC incorporates enhanced bandwidth of multi-section topology and miniaturization capabilities of composite right/left hand (CRLH) configuration structures. A prototype is designed and fabricated to operate at GSM 900 MHz and ISM 2.45 GHz. The designed structure achieves miniaturization of 47% with coupling bandwidth 18% in lower band and 28.1% in upper band. Phase imbalance between the output ports in both the bands is ≤ 50 for this coupling bandwidth.

This paper presents a novel dual band/dual mode compact hybrid coupler which acts as dual-functional, a dual band branch line coupler at lower band but a rat-race coupler at higher band. The outputs of the proposed coupler at the each mode of operation are the same side. This unique design is implemented by using artificial transmission lines (TLs) based on open split ring resonators (OSRR). The proposed 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.