Dual-band Coupler Research Articles

Dual-Band Butler Matrix with the Same Phase Difference for Long-Term Evolution Applications

ABSTRACTA novel dual-band Butler matrix is proposed with the same phase difference, aiming at the interest of long-term evolution. The total circuit simply includes four 3-dB 90° dual-band couplers and two 45° broadband phase shifters, which are capable of operating at two separate frequencies. Due to the utilized 45° broadband phase shifter, the phase differences remain invariant at two unrelated frequencies between the adjacent outputs. This Butler matrix can be easily fabricated by using single-layer microstrip technology. The measured results of a prototype demonstrate that it can operate at both 1.85 and 2.7 GHz, which perform phase errors and coupling ratios within 5.44° and –6.63 ± 0.72 dB.

Highly Compact VHF/UHF Dual-Band/Dual-Function LTCC Circuits: Application to Avionic Systems

New architecture for a compact dual-band coupler filter suitable for avionic systems operating in the VHF 108–137 MHz and UHF 329–335-MHz bands is proposed. A systematic design methodology is presented, whereby, starting with a distributed branchline coupler, equivalent lumped-element models are generated and augmented to obtain the desired functionality. The resulting topology of interconnected inductors and capacitors is designed in an LTCC technology with a very small form factor. This circuit is fabricated and tested. Measured results are in close agreement with simulation and show that the circuit meets the required specifications.

A Novel Design of Dual-Band Coupler with Stepped-Impedance Open Stubs

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.

Generalized dual-band branch-line coupler with arbitrary power division ratios

In this paper, a novel design of generalized dual-band quadrature hybrid with arbitrary power division ratios is presented and investigated. This coupler has a simple structure and can cover a wide range of power division ratios at the two designated frequencies. Exact closed-form equations are derived based on the even–odd-mode analysis method. The proposed structure offers some special features, encompassing: (1) a generalized structure of some recently published papers; (2) isolation in vertical and horizontal directions in the two-dimensional structure; (3) the same sign of the output phase difference for the structure with horizontal isolation and the opposite sign for the structure with vertical isolation; (4) large power division ratios for both vertical and horizontal isolation conditions; (5) large frequency band ratio for both vertical and horizontal isolation conditions; (6) capability of the bandwidth improvement by exploiting coupled lines with small coupling coefficient. For demonstration, a microstrip implementation of a 16:1 dual-band coupler working on 2.45/5.8 GHz is developed. Consistency between simulation and measurement results justifies the proposed design method and its equations.

Dual-band patch quadrature coupler with controllable power division ratios

By employing reactive loading method, a dual-band quadrature coupler, with flexible frequency ratio and controllable power division ratios, is proposed. Stubs with unequal width are loaded on different quadrants of circular sector patch to achieve dual-band operation with simplicity both in structure and design procedure. They also offer the possibility to provide different power division ratios at the two frequency bands for some special cases, and the quadrature phase characteristics can be obtained simultaneously. To verify the proposed configuration, four dual-band quadrature couplers for C and X band applications are designed, fabricated, and measured.

Design of Dual-Band Coupler With Arbitrary Power Division Ratios and Phase Differences

This paper presents, for the first time, a directional coupler that allows for arbitrary power division ratios as well as arbitrary phase differences at dual frequencies of interest. Explicit design equations in terms of dual-band power-dividing ratios and phase differences will be given here and were derived based on the even- and odd-mode decomposition analysis. To illustrate the design procedure, examples will be provided and the relevant studies on the coupler's electrical parameters for a wide range of dual-band specifications and frequency ratios were conducted, by which the graphical solutions can be readily used as the further design tool. In addition, the resulting operational bandwidths are included and discussed for completeness. To validate our idea, four coupler prototypes were carried out according to the given guidelines. Excellent agreement is obtained between the measured and full-wave calculated results. The functional versatility of the proposed simple structure is well suited to applications in dual-band integrated modules, such as the beam-forming networks, for both loss and size reduction.

Design principles of analytical methods for calculation of dual-band strip directional couplers with full structure symmetry

Conditions ensuring the dual-frequency operation of directional couplers with two symmetry planes were defined, and an approach to the development of methods for calculating the electric parameters of coupler elements was considered. This approach is based on using input impedances of partial two-pole networks of the co-phase (symmetrical) and opposite-phase (asymmetrical) excitation. Examples of using such approach to the classical circuit of double-stub directional coupler and to its modification with two additional reactive elements were also presented.

Dual-band branch-line couplers with three parallel lines for arbitrary power-split ratios

This work demonstrates the design procedure for a dual-band branch-line coupler that is capable of having an arbitrary coupling level. Simply with an additional parallel line that connect the centers of the two branch lines, the coupler can be designed to have an arbitrary power-split ratio between the through and coupled ports, while its structural simplicity is preserved. Moreover, the practical range of power-split ratio is relatively wider than previous dual-band branch-line couplers. A detailed design procedure is presented. Experimental results for dual-band couplers centered at 1 and 2.5 GHz with ±3-dB power-split ratios show great agreement with theoretical results. The power-split ratio remains within 0.5 dB from the specified, in as much as 230 MHz bandwidths at both 1 and 2.5 GHz.

Miniaturization of Rat-Race Coupler With Dual-Band Arbitrary Power Divisions Based on Stepped-Impedance Double-Sided Parallel-Strip Line

Generalized equations are presented for the design of a rat-race coupler with a phase inverter and an arbitrary power division, where its four arms are built by symmetric reciprocal lossless two-port networks. According to these equations, uniform- and stepped-impedance rat-race couplers are analyzed and synthesized with dual-band arbitrary power divisions. The relationships between the geometries and the design specifications of proposed dual-band rat-race couplers are completely determined. Under such circumstances, the most compact configuration of the stepped-impedance rat-race coupler is achieved when the maximum allowable impedance ratio is applied for all its arms. Several prototypes are realized with double-sided parallel-strip lines (DSPSLs) and DSPSL phase inverters. As the stepped-impedance arms are not limited to simulate 90° sections and the phase inverters are implemented into our proposed dual-band couplers, the component circumferences are reduced significantly by 65%-70%, in comparison with their conventional 540° counterpart. Their good performances are demonstrated by the simulated and measured results.

A compact dual-band coupler with arbitrary power dividing ratio using broadside-coupled microstrip

In this paper, a compact dual-band coupler with arbitrary power division ratio using broadside-coupled microstrip has been proposed, designed, and measured. The proposed coupler is formed by two three-section microstrip lines and a common ground plane with three rectangular shaped slots used for coupling. Simple analysis method based on the even-odd mode technique has been applied, design equations are then derived. With the even- and odd-mode characteristic admittances, the initial geometry parameters of the proposed coupler are obtained by using the empirical formulas. The coupler features a wide frequency ratio range, arbitrary power dividing ratio, compact size, and wide bandwidth. For verification purposes, two prototypes of the proposed couplers with a coupling ratio of 3 and 6 dB, operating at the frequency of 2.4/5.2 GHz, have been designed, simulated, fabricated, and measured. Good agreements have been shown between the simulated and the measured results.

A Novel Dual-Band 3-dB Branch-Line Coupler Design With Controllable Bandwidths

This paper presents, for the first time, the design and implementation of a dual-band branch-line coupler with unequal operating bandwidths. The control of bandwidths is accomplished by the use of dual-band quarter-wavelength impedance transformer with controllable phase slopes over the two designated frequency bands. The adjustment of phase slopes is attained by the proper selection of the circuit parameters of the transformer. For design purposes, closed-form expressions are derived for the determination of the electrical lengths and line impedances of the resulting coupler. For experimental verification, both simulated and measured results of dual-band couplers designed to operate at 1 and 2 GHz are shown.

Compact dual-band stubless branch-line coupler

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.

Thin‐film barium strontium titanate varactor tunable dual‐band quadrature hybrid coupler

AbstractA thin‐film barium‐strontium‐titanate (BST) and a conventional silicon varactor tunable dual‐band quadrature hybrid couplers are characterized and compared in this article. Both structures are composed of four quarter‐wavelength sections at a frequency located between the two operating frequencies, and with two pairs of open‐ended stubs. Frequencies tuning make used of BST interdigital and silicon varactor diode capacitors connected at the open‐ended stubs. The characterized BST interdigital capacitor presents a capacitive‐tunability of 52% through an applied voltage of 0 to 25 V, while 82.5% is for the selected commercial silicon varactor diode. The silicon varactor‐tuned dual‐band coupler exhibits 45.9 and 5.2% center operation tuning frequency for the first and the second band, respectively, while 29.2 and 4.3% are achieved by the BST tunable coupler. With two‐tone nonlinear characterization test, the BST tunable coupler biased at 0 and 25 V presents a better IP3 of +25.45 and +35 dBm, respectively, while +11.5 and +34 dBm are obtained for the silicon varactor tunable coupler. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 54:858–867, 2012; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26719

Analytical Design of Two-Mode Dual-Band Filters Using E-Shaped Resonators

This paper presents a novel analytical approach for designing two-mode dual-band bandpass filters using E-shaped resonators. Based on the dual-band coupling matrix, the dimensions of the filter configuration are extracted via even- and odd-mode analysis of E-shaped resonators. The back-to-back E-shaped resonators provide the out-of-phase property by coupling at specific edges, and it produces good selectivity for dual-band characteristics. The proposed filters have the advantage of compact size and satisfy various requirements of filter orders and coupling coefficients at both passbands. The transmission zeros are successfully introduced into each passband in both filters. To verify the proposed method, two filters are implemented using microstrip technology. The measured results exhibit two-mode dual-band bandpass responses and agree well with simulations.

Design of a printed dual-band coupled-line coupler with generalised negative-refractive index transmission lines

A dual–band printed metamaterial coupler made of a microstrip line and a generalised negative-refractive-index (NRI) line is presented. Owing to the presence of two left-handed bands in the generalised negative-refractive-index transmission line (NRI-TL) unit cell, backward coupling occurs over two frequency ranges centred on 2.7 and 4.7 GHz. Measured results for an edge-coupled device are reported; peak coupling levels of −3.5 and −4.4 dB are observed.

Analysis of frequency-selective impedance loading of transmission lines for dual-band couplers

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.

Design of Dual-Band Slotted Patch Hybrid Couplers Based on PSO Algorithm

A planar 3 dB patch hybrid coupler using cross and circular-shape slots is presented for a dual-band application. By inductively loading a pair of cross slots and four circular holes on a square patch, the matching and isolation performance of the miniaturized patch hybrid coupler is improved. In addition, the open-circuited shunt stubs are further installed at four ports to realize two operating bands. Since the slotted patch resonator cannot be characterized by the closed-form transmission line theory, the particle swarm optimization (PSO) algorithm is constructed and integrated with a full-wave solver to determine the variable parameters of the proposed structure. Finally, a prototype dual-band coupler operating at 915 MHz and 1575 MHz is designed and fabricated. Measured results show a good agreement with those obtained from simulation.

Novel dual-band hybrid coupler using improved simplified CRLH transmission line stubs

In this article, a novel dual-band hybrid coupler is designed by adopting improved simplified composite right-/left-handed (ISCRLH) transmission line (TL) stubs.An ISCRLH TL stub is composed of two ISCRLH TL unit cells with input and output uniform TL sections at the terminals, which can produce specified impedance and phase shift at two (arbitrary) different frequencies. The conditions for synthesizing the dual-band ISCRLH TL stub are discussed in detail, and then such a stub is applied to implement a novel dual-band hybrid coupler in microstrip configuration, and excellent agreement between the simulated and measured results is achieved, which reveal good performance and dual-band operation. The novel device is small, fully planar, and easily designed and fabricated. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52:2473–2476, 2010; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.25491

Dual-band hybrid coupler with source to load impedance matching

A novel dual-band hybrid coupler with source to load impedance transformation is presented together with detailed design formulas.Previous couplers were either dual-band or impedance transforming but not both. A dual-band impedance transforming coupler is designed accordingly for demonstration. Experimental results obtained agree well with both the numerical and simulated results. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52:2515–2519, 2010; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.25545

New Multiband Coupling Matrix Synthesis Technique and Its Microstrip Implementation

In this paper, we present a novel analytical multiband transversal coupling matrix synthesis technique. By properly combining several single-band filtering functions, the multiband filtering function with flexible transmission zeros and various bandwidth are available. The transversal coupling scheme is then transformed into a practically realizable coupling scheme. To verify the feasibility of the proposed method, two dual-band coupling schemes, both single-path and dual-path, are proposed as examples of the dual-band filter design. Finally, the dual-band filter, based on the coupling matrix corresponding to a specific coupling scheme, can be realized using a microstrip parallel-coupled structure.