Wideband Branch-line Coupler Research Articles

A Compact Wideband Branch Line Coupler for Lower 5G Applications

A Compact Wideband Branch Line Coupler for Lower 5G Applications

A Novel Compact Broadband Quasi-Twisted Branch Line Coupler Based on a Double-Layered Microstrip Line.

A novel quasi-twisted miniaturized wideband branch line coupler (BLC) is proposed. The design is based on bisecting the conventional microstrip line BLC transversely and folding bisected sections on double-layered substrates with a common ground plane in between. The input and output terminals, each with a length of λg/4, and the pair of quarter-wavelength horizontal parallel arms are converted into a Z-shaped meandered microstrip line in the designed structure. Conversely, the pair of quarter-wavelength vertical arms are halved into two lines and transformed into a periodically loaded slow-wave structure. The bisected parts of the BLC are placed on the opposite side of the doubled-layer substrate and connected through four vias passing through the common ground plane. This technique enabled a compact BLC size of 6.4 × 18 mm2, which corresponds to a surface area miniaturization by ~50% as compared to the classical BLC size of 10 × 23 mm2 at 6 GHz. Moreover, the attained relative bandwidth is 73.9% (4.6-10 GHz) for S11, S33, S21, and the phase difference between outputs (∠S21 - ∠S41). However, if a coupling parameter (S41) of up to -7.5 dB is considered, then the relative bandwidth reduces to 53.9% (4.6-10 GHz) for port 1 as the input. Similarly, for port 3 as the input, the obtained bandwidth is 75.8% (4.5-10 GHz) for S33, S11, S43, and the phase difference between outputs (∠S43 - ∠S23). Likewise, this bandwidth reduces to 56% (4.5-8 GHz) when a coupling parameter (S23) of up to -7.5 dB is considered. In contrast, the relative bandwidth for the ordinary BLC is 41% at the same resonant frequency. The circuit is constructed on a double-layered low-cost FR4 substrate with a relative permittivity of 4.3 and a loss tangent of 0.025. An isolation of -13 dB was realized in both S13 and S31 demonstrating an excellent performance. The transmission coefficients between input/output ports S21, S41, S23, and S43 are between -3.1 dB to -3.5 dB at a frequency of 6 GHz. Finally, the proposed BLC provides phase differences between output ports of 90.5° and 94.8° at a frequency of 6 GHz when the input ports 1 and 3 are excited, respectively. The presented design offers the potential of being utilized as a unit cell for building a Butler matrix (BM) for sub-6 GHz 5G beamforming networks.

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.

Wideband Octagonal Dual Circularly Polarized Sub-array Antenna for Ku-Satellite Systems

In this paper the analysis and design of a dual circularly polarized 4×4 antenna array operating in Ku-band are discussed with emphasis on its sequential feeding network. The dual circular polarization is achieved by feeding a stacked octagonal patches with a wideband branch line coupler. The proposed 4×4 antenna array is based on two separate sequential feeding networks for LH and RH circular polarizations. The advantage of the proposed feeding network is that it is implemented on a single layer. Simulation results by using both HFSS and CST are presented for comparison. In addition, experimental verifications are presented.

A Flexible Miniaturized Wideband Branch-Line Coupler Using Shunt Open-Stubs and Meandering Technique

A Flexible Miniaturized Wideband Branch-Line Coupler Using Shunt Open-Stubs and Meandering Technique

A Tunable Vector-Sum Filtering Power Divider With Continuously Tuned Frequency and Arbitrary Output Phase Difference

A novel tunable vector-sum filtering power divider (FPD) with arbitrary output phase difference is proposed. It is constructed by a tunable FPD [which has reconfigurable in-/out-of-phase output and arbitrary power division ratios (PDRs)] on the left and a wideband branch-line coupler (BLC) on the right. The output wave from the left FPD forms two orthogonal vectors at each output port of the BLC. The orthogonal vectors are summed up and result in a new vector with phase that is purely determined by the amplitude ratio of the orthogonal vectors. As a result, the phase difference between the new vectors at the outputs of the BLC can be continuously tuned by adjusting the PDR of the left FPD. Detailed theoretical analysis has been given. It shows that the phase difference between the output ports can be flexibly tuned from 0 °C to 360 °C within the full frequency tuning range.

Notice of Retraction: Comments on “Coupling Coefficient Reconfigurable Wideband Branch-Line Coupler Topology With Harmonic Suppression”

Retracted.

Design of Miniaturized 10dB Wideband Branch Line Coupler Using Dual and T-Shape Transmission Lines

Design of Miniaturized 10dB Wideband Branch Line Coupler Using Dual and T-Shape Transmission Lines

Rapid surrogate-assisted design optimization of minimum-size broadband branch-line couplers with variable topology

This work discusses simulation-driven design of miniaturized wideband branch-line couplers with a variable topology. Size reduction is enabled here by replacing uniform transmission lines of the original coupler with slow-wave structures in the form of cascaded compact cells and meander lines. The primary goal is to determine a number of cells in the cascade and particular cell dimensions for which the minimum size of the coupler as well as its required operating conditions are ensured. To this end, we employ a surrogate-assisted technique involving a trust-region gradient search framework. Computational efficiency of the design process stems from estimating the Jacobian of circuit responses at the level of a low-fidelity model of the cascade. The latter is composed in a circuit simulator from duplicated EM-evaluated data blocks of a single cell and is well correlated with the corresponding high-fidelity model. The key advantage of this work is the utilization of a reconfigurable, cheap, and well-aligned low-fidelity model. The proposed approach is demonstrated through design of a minimum-size two-section branch-line coupler with quasi-periodic dumbbell-shaped cells and meander lines. Excellent circuit performance as well as its small size showcase the reliability and usefulness of the presented method. Experimental verification is also provided.

Wideband Branch Line Coupler with Open Circuit Coupled Lines

This paper focuses on the design of a Wideband Branch Line Coupler by using open circuits coupled lines technique. The design is implemented by adding four open circuits coupled lines to the structure of the Conventional Branch Line Coupler. The proposed design of Wideband Branch Line Coupler is simulated using CST microwave software. The simulation results show that the coupler is operated at 3.8 GHz with coupling factor of -3dB and 90̊ phase difference between the two output ports. The prototype is fabricated and measured to validate the simulated results. A similar Wide Bandwidth is observed on simulation and measurement. The structure achieved a fractional bandwidth of 42.63%, and return loss of 21 dB compared to the Conventional Branch Line Coupler (BLC).

A novel two section branch line coupler employing different transmission line techniques

In this paper, a 3dB wideband branch line coupler with reduced size and harmonic suppression is presented. New multiple asymmetric π-shaped, cross and T-shaped transmission line techniques are used to reduce the physical size of the coupler. At the operating frequency of f0=0.9GHz, the fabricated coupler achieves 15dB return loss bandwidth of 44.4% with a size reduction of 76.3%. The designed coupler has insertion loss better than 3.6dB with a magnitude balance of 0±1dB over the frequency band 0.67–1.05GHz. In addition to compact design, the unwanted harmonics are well suppressed up to 4f0 with a level better than 20dB by maintaining good agreement between the measured results and theoretical predictions.

Miniaturized Wideband Branch-Line Hybrid Coupler with Capacitive Effect and Defected Ground Structure (DGS)

Background/Objectives: Branch-line hybrid couplers are used as components, in almost every Radio Frequency (RF) system, including power combiners and dividers. In this paper a 3dB miniaturized broadband branch-line coupler is designed and experimentally verified. Methods/Statistical Analysis: The new distributed capacitors which are placed within the empty space of the hybrid, minimize the size of the coupler. The ground of the structure is also defected by dumbbell shape parts to increase the impedance bandwidth. Findings: A prototype at 2.5GHz was designed and fabricated. The measurement results show that the bandwidth and isolation of the modified version are superior to the conventional 3dB hybrid coupler, also the measurement results confirmed that there is 2700 phase difference between output ports. The size of the fabricated structure shows 62% size reduction and also the measured bandwidth is 0.82GHz. Conclusion/Improvements: Miniaturized wideband branch-line hybrid coupler is a good candidate for development of a compact size and integrated microwave systems.

Circularly polarized rectangular dielectric resonator antennas with branch-line coupler for wideband applications

In this paper, two circularly polarized rectangular dielectric resonator antennas (RDRAs) are proposed for wideband applications. One common method for achieving the orthogonal modes for circular polarization is used by coupler. In this configuration, a 45° rotated branch-line coupler which is located under the hollow RDRA with two tapered excitation strips are connected to sidewall of RDRA to excite two degenerate TE111 modes is used. For the second antenna, a pair of tapered stubs and metallic vias is added to structure to increase bandwidth, and antenna gain. These antennas exhibit better results in comparison with similar conventional DRA with similar feeding technique. The major differences of the proposed antenna compared to the prior arts were using a few simple techniques simultaneously to improve impedance and axial ratio (AR) bandwidths, gain, and cost of structure. These techniques consist of using wideband branch-line coupler, hollow RDRA, placing the coupler under DR with 45° rotation, tapered excitation strip, FR4 substrate, and tapered stubs and metal vias in the second antenna. Both simulated and measured results are presented. These first and the second antennas offer an impedance bandwidth (S11<−10dB) of 69.4% and 96.3%, and axial ratio bandwidth (AR<3dB) of 52.45% and 57%, respectively.

Compact Wide-Band Branch-Line Coupler with Meander Line, Cross, and Two-Step Stubs

Despite being widely used, branch-line couplers (BLC) still suffer from large size. This makes it difficult to incorporate BLC into miniature microwave devices. The work presented here is the design and implementation of a 3-dB reduced-size wide-band 3-branch-line coupler (3-BLC). By combining meander line, cross, and two-step stubs techniques, size reduction and bandwidth improvement is successfully achieved on 3-BLC design. The 3-BLC length was reduced along the horizontal branches using two-step reduction technique while the center vertical branch was reduced using cross stubs. A simple two-turn meander line is utilized at the two ends vertical branches of the coupler to obtain balanced length with the middle vertical branch. Hence, its width was optimized to maximize the coupler bandwidth. The 3-BLC was designed to operate at 2.45 GHz wireless local area network frequency band (IEEE 802.11 b/g) and fabricated on a 1.6 mm thick FR-4 board. The simulated and measured results are in very good agreement and show a fractional bandwidth of 50% and a sized reduction of 61.64% at the center of the frequency band. The proposed coupler design provides BLC that occupies less space, simple to implement, and wide-band BLC architecture with generic 3-BLC wide-band characteristics retained. © 2013 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:1810–1815, 2013

A Compact Microstrip Wideband Arbitrary Branch-Line Coupler with Coupled-Line Impedance-Transforming Structures

Abstrct A novel coupled-line impedance-transforming structure with two parallel short-circuit stubs is proposed to design a wideband branch-line coupler with arbitrary power division in this article. In order to design this modified wideband branch-line coupler, analytical synthesis equations are obtained. As typical examples, four wideband branch-line couplers with different power dividing ratios are presented. The widest 20-dB return loss and isolation fractional bandwidth in these four numerical examples is almost 38%. Finally, two microstrip branch-line couplers operating at 1 GHz are fabricated and measured. One of these couplers has equal power division and a measured 13.9-dB return loss and isolation fractional bandwidth of 32.8%. The other one has 3-dB unequal power division and a measured 12.7-dB return loss and isolation fractional bandwidth of 37.6%. Obviously, this proposed branch-line coupler has several advantages, including a wide band, a compact size, an unequal power division, easy implementation (simple structure), and an analytical design method.

Wideband Branch-Line Couplers With Single-Section Quarter-Wave Transformers for Arbitrary Coupling Levels

Wideband branch-line couplers with arbitrary coupling levels are demonstrated. By integrating single-section quarter-wave transformers at each port, wideband characteristic with excellent coupling flatness is achieved. Also, a method is demonstrated that introduces intentional mismatch for a further enhancement in bandwidth. Superior structural and design simplicity outperform previous wideband couplers. Branch-line couplers at 3 GHz are demonstrated experimentally that maintain the coupling level within 0.5 dB from the specified 10 dB in as much as a 50.9% bandwidth, with minimum return loss and isolation of 16.3 and 18.7 dB, respectively.

Harmonic suppressed compact wideband branch-line coupler using unequal length open-stub units

In this article, the design of a broadband branch-line coupler (BLC) with reduced size and suppressed harmonic passband response is presented. The proposed approach can be used to replace the low impedance λ/4 lines of the conventional BLC by an equivalent structure almost λ/12 in length. The main advantage of the proposed BLC is that, it has approximately the same bandwidth as that of a conventional BLC. A prototype broadband coupler having fractional bandwidth >50% at 1.1 GHz and of size less than one third of a conventional three-section wideband BLC topology is realized. In addition, at least 20 dB suppression of up to fourth harmonics is achieved. © 2010 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2011.

Compact wide-band branch-line hybrids

Wide-band branch-line couplers are designed and tested. The proposed couplers feature compact size on a single circuit layer structure without via-holes. For the broad-band property and cost effectiveness, we have designed a four-branch hybrid with mixed distributed and lumped distributed elements. Analysis on the equivalent circuits was performed carefully in order to obtain a sufficient bandwidth with reduced design area. The fabricated hybrids have the fractional bandwidth larger than 56% at the center frequency of 2 GHz. They also show size reduction up to 55.2% compared with the conventional design method.