Microstrip Branch-line Coupler Research Articles

An Ultra Compact Microstrip Branch Line Coupler with Wide Stopband Using LCL Filter and Meandered Stubs for Microwave Applications

A branch line coupler (BLC) with ultra-compact size and harmonic suppression ability using an LCL filter and meandered stubs is proposed in this paper. There are some important factors in microstrip coupler design, including size reduction, harmonic suppression, and low insertion loss. Thus, improving each of these factors will contribute to a more efficient design. In the proposed circuit, for the first time, LCL filters, including four T-shaped circuits and four meandered line open-ended stubs, were used together to reduce the circuit size and suppress unwanted harmonics. The proposed LCL filters, incorporated in the BLC branches, resulted in superior size reduction and harmonic suppression for the presented BLC. The proposed BLC correctly worked at 900 MHz with 300 MHz operating bandwidth, which showed 33% fractional bandwidth (FBW). Additionally, a wide suppression band from 1.4 GHz to 8.8 GHz, with more than 20 dB attenuation level was obtained, which suppressed the second to ninth unwanted harmonics. The overall size of the proposed 900 MHz coupler was only 11 mm × 10.4 mm (0.044 λ × 0.042 λ) while the size of the conventional 900 MHz coupler was 61.5 mm × 62.5 mm (0.25 λ × 25 λ). The proposed BLC had a very small size and only occupied 3% of the size of the conventional coupler, which corresponded to a 97% size reduction. To the best of the authors’ knowledge, to date, the best size reduction has been obtained among the published couplers. Furthermore, the experimental results verified the simulated and analyzed results of the proposed technique and demonstrate its potential for improving the performance and miniaturizing the size of other similar BLCs.

A modified branch line coupler with compact size and ultra wide harmonics suppression band

ABSTRACT In microstrip branch line coupler (BLC) design, there are significant parameters, including size reduction, insertion loss, and harmonic suppression, which affect the performances of the device. In this paper, a modified BLC with compact size, wide harmonics suppression band, and low insertion loss in operating band is designed. In the proposed design, four types of resonators are used together to create proposed BLC with superior performance. The proposed BLC works at 900 MHz with only 0.1 dB insertion loss at pass band. The proposed BLC provides wide harmonics rejection band from 1.8 to 8.1 GHz, which suppresses 2nd to 9th unwanted harmonics. The conventional coupler occupies 0.25 λ × 0.25 λ, which has undesirable size. But, the proposed BLC occupies compact area of only 21.95 mm × 30.55 mm (0.12 λ × 0.09 λ), which shows more than 81% size reduction.

Design of a Modified Compact Coupler with Unwanted Harmonics Suppression for L-Band Applications

This paper presents the design, analysis, and fabrication of a new miniaturized microstrip branch line coupler (BLC) with high harmonics suppression. The T-shaped resonators, open stubs cross-shaped resonators and radial stubs are used in the proposed coupler design. The designed BLC operates at 1 GHz frequency, which can suppress up to 5th spurious harmonics with a 20 dB level of attenuation. High miniaturization of about 86% is obtained for the proposed BLC, which is corresponding to the normalized size of 0.009 λg2. The measured values of isolation and return loss are obtained 28 dB and 29 dB, respectively, while the measured insertion loss of better than 0.2 dB is achieved at the operating frequency. Additionally, the operating bandwidth of the designed coupler ranges from 0.905 GHz up to 1.105 GHz, which shows a 200 MHz operating bandwidth or a fractional bandwidth (FBW) of 20%. The presented BLC is fabricated and measured, where the measurements confirm the simulated results. The designed coupler shows desirable performance compared to the recent designed couplers.

The Influence of changes in the dielectric constant on Return loss, Vswr, Isolation and Phase Difference Microstrip Hybrid Coupler For Coastal Radar Applications

This study aims to determine the effect of changes in perubahan value changes in the Hybrid coupler on the return loss, insertion loss, coupling factor and the isolation value at the 3 GHz frequency which is applied to coastal radar. the type of antenna used is a microstrip patch antenna. The material used to design the antenna is FR4 with a substrate thickness of 1.6 mm and has a value of er r = 4.3. This study designed a microstrip branch line coupler with a T-Junction that works at a frequency of 3 GHz with both loss values ​​for (Tx) and (Rx), namely 3 dB and a phase difference of 90 °. The steps taken are after obtaining the length and width values ​​from the formula, then these values ​​are simulated after obtaining the correct value of 3 GHz, then an experiment is carried out with the dielectric constant values ​​of 4.1, 4.3 and 4.6.

Introductions about Microstrip Couplers and Power Splitters

Microstrip couplers and power splitters are widely used electrical components in the field of microwave technology, which has the function of dividing one wave into multiple waves with same magnitudes but different phases. In this essay, 5 typical types of couplers and power splitters are introduced, with their applications, layout designs, effect on the wave, advantages and weaknesses. Couplers and power splitters are labelled with their output wave phase differences and their voltage magnitude transfer ratio. In this essay, all the couplers introduced are 3dB couplers, which means that the output voltage is decreased by 3dB. The Wilkinson power splitter has an output phase difference of 0 degree, the monolithic multilayer 2-line microstrip directional coupler, the Lange coupler, the microstrip branch-line coupler have output phase difference of 90 degrees, and the planar Marchand balun has output phase difference of 180 degrees. The microstrip rat-race coupler has 2 divider modes and 1 combiner mode, where in the divider mode the phase difference could be set as 0 degree or 180 degrees. Therefore, in the design of microwave circuits, the type of coupler should be carefully chosen according to the working characteristics, the structure features and the working conditions of couplers.

New design of wideband microstrip branch line coupler using T-shape and open stub for 5G application

A new design of wideband branch-line coupler (BLC) using T-shape with open stub microstrip line is proposed. The branch line coupler is integrated with low and high impedance λ/4 transmission lines to achieve the comparatively compact size of (27.2 mm × 16.5 mm). operating the bandwidth in simulated of BLC from 2.9 to 4 GHz is obtained 30.22% with a frequency center of 3.5 GHz. Meanwhile, the measured bandwidth of the BLC is cover from 2.8 GHz to 4.22 GHz is equal 33.40% at the center frequency 3.55 GHz respectively. The BLC simulated has low isolation and high return loss of -29.28 dB and -30.69 dB at the center frequency 3.5 GHz.Whereas, the measured result has a simple difference in the return loss and isolation are -27.43dB and -24.46 dB at the frequency 3.55GHz respectively. This BLC design has a good coupling factor of -2.97 and insertion loss of -3.65 dB. Furthermore, it obtains an excellent amplitude and phases different between two output of ±0.1 and 93.6°±3.4° with high performance. There is a good agreement between the simulated result and the measured result. This branch line coupler design used for 5G applications for future wireless communication systems.

A Model-Order Reduction Approach for Electromagnetic Problems With Nonaffine Frequency Dependence

The aim of this paper is to present a novel model-order reduction (MOR) technique for the efficient frequency-domain finite-element method (FEM) simulation of microwave components. It is based on the standard reduced-basis method, but the subsequent expansion frequency points are selected following the so-called sparsified greedy strategy. This feature makes it especially useful to perform a fast-frequency sweep of problems that lead to systems of equations exhibiting a nonaffine frequency dependence. This property appears, for example, when the excitation of the problem is characterized by a frequency-dependent waveguide mode pattern, or when the computational domain includes materials with frequency-dependent permittivity or permeability tensors. Moreover, the new MOR scheme can be also used to accelerate the frequency sweep of problems with many excitations, for which the standard reduction algorithms tend to be time-consuming. Its effectiveness and accuracy is verified through analysis of three microwave structures: planar microstrip branch-line coupler, three-port waveguide junction with ferrite post, and an eighth-order dual-mode waveguide filter.

A Branch Line Coupler with improved stopband and miniaturized size for L-band applications

This paper offers a compact microstrip branch line coupler with amended stopband performance using stepped impedance resonators. The operational frequency is adjusted at 1.174 GHz for L-band applications. The proposed coupler has a 75% decrement of size compared with a typical branch line coupler at the operational frequency. Embedded stepped impedance resonators make attenuation (more than 12 dB) on 2nd to 17th harmonics. The insertion loss and coupling are −3.1 dB and −3.1 dB, respectively. The proposed branch line coupler has been simulated, fabricated and tested. Good accord has been attained between simulation and test results.

Designs of Branch-Line Couplers by Considering the Parasitic Effects of P-I-N Diodes

Branch-line couplers (BLCs) are commonly used in the wireless systems. To achieve reconfigurable applications, switchable BLCs with p-i-n diodes can be used. Several studies have used diode parasitic reverse-biased capacitor and forward-biased inductor to approach off and on states. Although the capacitance and inductance are usually low, the parasitic effect may degrade predicted switching responses. This study proposes five reconfigurable switching microstrip BLCs. Each of the first two presented BLCs uses shunt to ground diodes for realizing two switching modes. The first mode with reverse-biased capacitors for perfect matching design is equivalent to a conventional branch-line coupler (BLC). The second mode uses low forward-biased inductances to approach shunt to ground, which transfers most signal power from Port 1 to Port 2/4; however, parasitic inductors produce some mismatches. To improve this problem, the proposed third or fourth BLC achieves two perfect matching modes by using shunt stub-loaded diodes. Specifically, by using four stub-loaded diodes, the proposed final BLC exhibits three perfect matching modes and one perfect isolation mode under a lossless ideal circuit condition.

Miniature microstrip branch line coupler with folded artificial transmission lines

The present work is devoted to the miniaturization of a conventional three branch line coupler device in UHF band. The procedure for designing miniature structures based on replacing the microstrip transmission line segment with equivalent structures with the same phase shift is described. These structures are placed in free space inside the coupler. The proposed coupler operates at 1 GHz (UHF band), with good specifications. The area of the manufactured prototype of the three-branch line coupler with open-circuit conditions stubs is 909 mm2, which is 76% less than the size of the conventional device and relative bandwidth is 23.7%. The area of the manufactured prototype of the three-branch line coupler with high-resistance lines with a high-resistance segment in the form of U symbol is 1169.7 mm2, which is 69.1% less than the size of the conventional device and relative bandwidth is 34.1%.

Miniaturized branch-line coupler based on slow-wave microstrip lines

AbstractThis paper presents a miniaturized 3-dB branch-line coupler based on slow-wave microstrip transmission lines. The miniaturized coupler operating at 2.45 GHz is designed and implemented on a double-layer printed circuit board substrate with blind metallic vias embedded in the lower substrate layer providing the slow-wave effect. Based on this concept, a 43% size miniaturization is achieved as compared with a classical microstrip branch-line coupler prototype. The measured S parameters present a return loss of 25.5 dB and an average insertion loss equal to 0.05 dB at the operating frequency.

Novel microstrip branch-line coupler with low phase shift for WLANs

In this work, a novel branch-line coupler is presented using a new type of microstrip cells. The proposed structure is consisting of high and low impedance sections and a main small square closed loops. It operates at 2.4 GHz for WLAN applications. Using the introduced structure, a good passband performance is achieved. An excellent phase balance closed to ideal is obtained with a phase difference of 270 ± 0.037° between output ports. Furthermore, there are low return loss and high isolation better than − 29 and − 30 dB respectively. Meanwhile, the designed coupler has a good insertion loss and coupling factor. Despite of having a high performance, this coupler is relatively compact with an overall size of 0.037 λg2. The designing method is based on proposing an LC model of a basic microstrip cell and finding the effective parameters to obtain a high performance. In order to validate the designing method and simulation results, the presented coupler is fabricated and measured. There is a good agreement between the simulated and measured results.

Разработка микрополоскового двухшлейфного моста с высокой степенью миниатюризации

Разработка микрополоскового двухшлейфного моста с высокой степенью миниатюризации

A miniaturized branch-line hybrid coupler microstrip for long term evolution applications

This paper presents the miniaturized microstrip branch-line 3dB hybrid coupler (BLHC) is designed and simulated as a platform in producing a significant reduction in the operating frequency 2.2 GHz in Long Term Evolution (LTE) application. High and low impedance transmission line are used to miniaturize the conventional Branch-Line Hybrid Coupler. The proposed branch line coupler is utilized from meander line Technique. The design and simulated results of all above components are validated by electromagnetic simulation (by Method of Momentum using the Advance Design System (ADS) tool from Agilent technologies), which confirms the theory and validates the proposed coupler design. After this validation into the simulation. The Branch-Line Hybrid Coupler which has been designed using a substrate material of FR-4 with dielectric constant (4.3), substrate thickness (h=1.570 mm). The size of the implemented branch-line 3dB hybrid coupler (BLHC) is 50x19.51mm², which is 29.72% compared to the conventional couplers for the higher LTE frequency band. Also, the reflection coefficient, the isolation and the phase difference between two output ports are as good agreement simulated results permits to confirm the designed coupler structure.

Design of compact microstrip branch line coupler using semi-circular and rectangular resonators with wide range suppressed harmonics

In this paper, a novel compact branch line coupler (BLC) with 10 suppressed harmonics is proposed. To achieve small size, four semi-circular and eight stepped impedance resonators are used instead of 35 Ω and 50 Ω conventional branch line coupler transmission lines. The operational frequency of the presented branch line coupler is 0.85 GHz. The size of the proposed circuit is reduced about 78% in compared with the conventional branch line coupler. To verify the design and analysis, the proposed coupler is simulated using full-wave EM simulator Advanced Design System and fabricated. Simulation results are in good agreement with measurement results.

Surrogate-assisted EM-driven miniaturization of wideband microwave couplers by means of co-simulation low-fidelity models

This article proposes a methodology for rapid design optimization of miniaturized wideband couplers. More specifically, a class of circuits is considered, in which conventional transmission lines are replaced by their abbreviated counterparts referred to as slow-wave compact cells. Our focus is on explicit reduction of the structure size as well as on reducing the CPU cost of the design process. For the sake of computational feasibility, a surrogate-based optimization paradigm involving a co-simulation low-fidelity model is used. The latter is a fundamental component of the proposed technique. The low-fidelity model represents cascaded slow-wave cells replacing the low-impedance lines of the original coupler circuit. It is implemented in a circuit simulator (here, ADS) and consists of duplicated compact cell EM simulation data as well as circuit theory-based feeding line models. Our primary optimization routine is a trust-region-embedded gradient search algorithm. To further reduce the design cost, the system response Jacobian is estimated at the level of the low-fidelity model, which is sufficient due to good correlation between the low- and high-fidelity models. The coupler is explicitly optimized for size reduction, whereas electrical performance parameters are controlled using a penalty function approach. The presented methodology is demonstrated through the design of a 1-GHz wideband microstrip branch-line coupler. Numerical results are supported by experimental validation of the fabricated coupler prototype.

Study on microwave dielectric properties of corundum type (Mg1−x Co x )4Nb2O9 (x = 0–0.6) ceramics for designing a microstrip branch-line coupler

This paper reports the study of structural, morphological and microwave dielectric properties of Co3O4 added corundum type Mg4Nb2O9 ceramics, sintered at 1200–1300 °C. The samples were prepared by solid state reaction method. X-ray diffraction patterns of these samples confirm the phase (Mg1−x Cox)4Nb2O9 along with a small percentage of secondary phase Mg4Nb2O9. The SEM micrographs suggest the gradual grain growth with the increase in Co addition as well as sintering temperature. The microwave dielectric properties of sintered ceramics were investigated by dielectric resonator method and they show a strong dependence on their composition, densification and microstructure. A good combination of dielectric properties with dielectric constant (er) of 16.69, quality factor (Qf) of 65,849 GHz (at 9.3 GHz) and nearly zero temperature coefficient of resonant frequency ( $${\tau }_{f}$$ ) have been obtained for (Mg0.7Co0.3)4Nb2O9 composition, sintered at 1275 °C. The design of a coupler circuit was simulated by Sonnet Lite software and then fabricated on this thermal stable ceramic taking centre frequency as 2 GHz. The experimental result resembles well with the simulated result and shows ~70% size reduction as compared to a similar circuit designed on FR4 substrate.

Computationally‐efficient surrogate‐assisted dimension scaling of compact dual‐band couplers

Reusing existing results in order to facilitate optimisation of structures for various sets of performance requirements such as operating frequencies is an attractive concept. When implemented properly, it can lead to considerable speedup of the microwave design process. In general, re-design of microwave structures is a challenging task, particularly for compact components where considerable electromagnetic (EM) cross-couplings make the relationships between geometry parameters and the structure responses complex. In this study, the authors address geometry scaling of miniaturised dual-band couplers by means of inverse surrogate modelling. It allows for fast estimation of the optimum values of structure dimensions corresponding to required operating frequencies, independently for each band. The inverse surrogate is constructed based on a set of reference designs obtained by optimising the equivalent circuit model of the coupler, and subsequently corrected using output space mapping to accommodate the discrepancies between the network model and the EM-simulation one. As demonstrated using a compact dual-band microstrip branch-line coupler example, geometry scaling is possible in a wide range of operating frequencies and at a very low cost of just a single EM simulation of the structure at hand. Numerical results are validated through physical measurements of fabricated coupler prototypes for several test cases.

Design of a compact dual‐band branch line coupler using composite right/left‐handed transmission lines

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.

Compact microstrip branch-line coupler with wideband quadrature phase balance

This letter presents planar microstrip branch-line (BL) couplers with improved phase and amplitude stability bandwidth along with significant size reduction. The prototypes are designed to operate at 433 MHz frequency band suitable for ISM 433 MHz applications. The prototypes with symmetric polygonal modification (SPM) and asymmetric polygonal modification (ASPM) offer a wide quadrature phase bandwidth of 37.8% and 35.5% respectively, over which the phase imbalance is within 90°±5°. In SPM all four transmission lines of the BL coupler have been symmetrically modified to bring in 75.99% size reduction compared to the conventional design. Further asymmetric modification has been performed to bring an additional 12.34% size reduction, compared to symmetric, and providing an overall size reduction of 78.95% compared to conventional BL coupler. The prototypes are able to offer compactness without compromising much on the matching, transmission and isolation parameters. © 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 58:1369–1374, 2016