Wideband Coupler Research Articles

A design of octagon‐shaped 3‐dB ultra wideband coupler using multilayer technology

AbstractA design of a 3‐dB ultra wideband (UWB) coupler with compact size (35 mm × 15 mm), which operates between 3.1 and 10.6 GHz is presented in this article. The proposed design is accomplished by using multilayer microstrip structure, which is formed by three layers of conductor and two layers of substrate. The top and bottom layers consist of an octagon‐shaped microstrip lines and an octagon‐shaped slot in the middle layer. The design was fabricated on Rogers RO4003c substrate. Both of the simulation and measurement results are being compared with verify the coupler's performances in real environment. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:127–130, 2013; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27259

A Design of Compact Ultra Wideband Coupler for Butler Matrix

A design of 3 dB compact ultra wideband (UWB) coupler for a 4 A— 4 Butler Matrix, which is operating between 3 and 11 GHz frequency range, is presented in this paper. The proposed design uses multilayer technology that allows having a compact and broad bandwidth coupler. The design uses elliptically shaped broadside coupled strips and a slot created in a common ground plane of two dielectric substrates with the same shape. The design then being fabricated on 0.8 mm thick FR4 substrates and it occupies the dimension of 30 mm A— 15 mm. The simulation and experimental results show a good performance in terms of bandwidth, which covers the entire UWB operation. In addition, detailed analysis of air gap effect for S-parameters and phase difference of the designed coupler is presented in this study.

Planar Ultra-Wideband Antennas in Ku- and K-Band for Pattern or Polarization Diversity Applications

Two planar diversity antennas operating in Ku- (12.4-18 GHz) and K-band (18-26.5 GHz) are proposed for ultra-wideband (UWB) applications. Both of them consist of a monopole radiating element and two orthogonal feeding ports. Their ground planes are modified and optimized to improve the isolation as well as to control the radiation. The first one is a pattern diversity antenna with a disc monopole patch. The second one is a polarization diversity antenna based on a square patch which is able to provide both linear and circular polarizations. Different feeding approaches are adopted to obtain a broadband impedance matching. Two wideband couplers are designed to provide the required feeding circuit. Both the simulated and measured results are presented to verify the proposed idea. Good radiation efficiency and isolation between the two ports are achieved. Consistent diversity performance is observed across the whole UWB bandwidth which is demonstrated by their radiation patterns.

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.

Recent results on compact broad-band and multi-band low-temperature co-fired ceramic components for radio frequency front-ends

Compact components for radio frequency (RF) front-ends realised in low-temperature co-fired ceramics (LTCC) are presented. The aim of this study was to highlight recent advances in realisation of different components for modern RF/microwave subsystems, stressing such attributes as compactness, wide bandwidth and operation in multiple bands. Two key components of every RF front-end are filters and couplers. To illustrate the feasibility of using LTCC technology to realise these components, several designs of filters and couplers are presented. Very compact LTCC ridge waveguide filter covering the whole US ultra-wide band is first discussed, followed by a dual-band LTCC ridge waveguide filter. Two types of wide-band couplers are shown: ridge waveguide couplers realised in LTCC and empty metallic waveguide and also a strip-line LTCC coupler. A common characteristic that will be shown is that the presented components by the authors are modelled using computer-aided design tools based on modal analysis for waveguides as well as commercially available finite-element tools. The shown examples have simulation results compared by different methods as well as some experimental results in LTCC and empty metallic waveguide, used to demonstrate the proposed approach.

Hybrid orthogonal junctions: wideband plasmonic slot-silicon waveguide couplers

In this paper, novel ultra compact and ultra wide band couplers between silicon and plasmonic slot waveguides are analyzed, characterized, and fabricated. This novel coupling scheme is fabricated using silicon on insulator platform. An orthogonal junction configuration is designed to provide non-resonate wideband coupling from a 400 nm silicon waveguide to 50-nm wide air-filled plasmonic slot. The 1 μm wide full-width half-max coupling spectrum can theoretically reach high peak of 70% coupling to the plasmonic slot centered around the 1550 nm wavelength. This center wavelength can be controlled by varying the silicon waveguide width. Theoretical analysis is in good agreement with FDTD simulated results, and experimental results. The fabrication procedure is also presented and discussed.

Rigorous Analysis of Wide-Band Directional Coupler Using Π-Shape Dielectric Waveguide

Wide-band directional couplers using П-Shape dielectric waveguide in the parallel coupling region are investigated in detail by a rigorous mode matching method, both the eigenvalue problem of the coupled П-guide and the coupling characteristics of curved transition structure are solved accurately. Particular attention is directed toward the effects of transition waveguides on the scattering and coupling performance of the coupler to give useful guidelines for the design and optimization consideration. Finally, a 3-dB directional coupler is proposed with quite constant coupling factor (within ±0.5dB) throughout a wide frequency band from 34 GHz to 40 GHz.

Design of Coaxial Couplers for High Efficiency Helix TWT

The main objective of the paper is to make an efficient design of the input and output coaxial coupler for a helix TWTs. An approach has been developed for the efficient design and analysis of the coaxial couplers in the practical situation. Normally multi-section impedance transformer approach is used for any wide band coupler. For a space helix TWT, coupler should be wide bandwidth and small size. In this case coupler is matched with helix slow wave structure and the standard 50-ohm connectors. The simulated return loss (dB) profile for different type of couplers is obtained by using Ansoft HFSS, CST microwave studio and compares those with experimental results. The tip loss design at sever ends for the input and the output section has been also optimized.

Closed-Form Equations of Conventional Microstrip Couplers Applied to Design Couplers and Filters Constructed With Floating-Plate Overlay

This paper presents a new method of designing tightly coupled directional couplers on printed circuit board substrates. The coupler is realized by placing a piece of floating metal plate on parallel-coupled microstrip lines to enhance the coupling between the lines. This structure yields a tightly coupled directional coupler without wire bonding and using high-resolution fabrication processes. A design procedure based on closed-form design equations of the parallel-coupled microstrips is proposed to design the new coupler. An <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">S</i> -band 3-dB coupler constructed from the new structure is fabricated and measured to verify the proposed design procedure. Another wideband coupler, comprising two sections of conventional microstrip couplers and one section of the new type coupler, is also fabricated and measured to demonstrate the flexibility of connecting the new structure and conventional microstrip structures or devices. The measurements of the two couplers demonstrate that the coupler operates properly with approximately 54% and 94% fractional bandwidth, respectively, showing good agreement with the electromagnetic simulations. Additionally, a broadband filter consisting of four sections of the proposed coupling structure is fabricated and tested. The measured insertion losses are around 0.8 dB associated with return losses of greater than 15 dB over a frequency range of 4.5-7.1 GHz, corresponding to a fractional bandwidth of 45%.

Optimal Model for Wiggly Coupled Microstrips in Directional Coupler and Schiffman Phase Shifter

A fast way to optimize wiggly coupled microstrips to reach high directivity is proposed, which makes it easy to fabricate a multi-section high directivity wideband coupler and Schifiman wideband phase shifter using wiggly coupled microstrip.

Compact Reflectometers for a Wideband Microwave Breast Cancer Detection System

The design of compact wideband microwave reflectometers for the purpose of inclusion in a breast cancer detection system is presented. In this system, a wideband frequency source is used to synthesize a narrow pulse via the step-frequency synthesis method. The reflectometer undertakes measurements in the frequency domain and the collected data is transformed into the time/space domain using IFFT. In order to accomplish reflection coefficient measurements over a large frequency band, compact wideband couplers and power dividers are used to form the reflectometer. Two compact six-port reflectometer configurations are investigated. One uses the Lange coupler and the Gysel power divider and the other one employs a 3dB slot-coupled microstrip coupler and a 2-stage Wilkinson power divider. The reflectometer employing the slot-coupled coupler and the Wilkinson divider provides a wider operational bandwidth, as shown by simulation results performed with Agilent ADS.

Wide-band lumped-element directional coupler with an arbitrary coupling coefficient

A method of synthesising wide-band directional lumped-element couplers with an arbitrary coupling coefficient is presented. The proposed synthesis method can realise a co-directional type lumped-element coupler with a wider operational bandwidth than conventional design methods while maintaining good amplitude and phase relationships of the output ports. Two coupler prototypes with coupling coefficients of 10 and 20 dB are designed and fabricated to verify the design concept. The measurements are very close to the theoretical predictions.

Rigorous hybrid‐mode analysis of an asymmetric coupled shielded dielectric image guide

AbstractA rigorous hybrid‐mode analysis based on the mode‐matching technique is used for computing the propagation characteristic of a general symmetric coupled shielded dielectric image guide. The validity of the theory is confirmed by comparing the data for a symmetric coupled line as a special case with the reported data available in literature. Then, illustrative numerical results are presented for the coupling characteristics of various cross‐sections of dielectric guides for suitable wideband coupler applications. © 1995 John Wiley &amp; Sons, Inc.

Highly broadband buried channel couplers

It is shown that, by taking advantage of the maximum in the spectral dependence of the coupling coefficient, very wideband symmetric and asymmetric singlemode couplers can be designed. The symmetric coupler design will allow at least 98% coupling between the two cores over the wavelength range 1.3–1.59 µm, while the asymmetric coupler can act as a 3 dB splitter with only ±0.8% variation in splitting ratio over the wavelength range 1.3–1.75 µm.

Mode Coupling And Power Transfer In A Coaxial Sector Waveguide With A Sector Angle Taper

We report a theoretical study of mode coupling and power transfer in a coaxial sector taper. The power transferred from the desired TE /sub 01/ mode into other propagating modes is calculated as a function of taper length and operating frequency. Power transfer via mode coupling involves at least three other modes: TE/sub 21/, TE/sub22/, and TM/sub21/. Power transfer as a function of final sector angle is also shown. At sector angles greater than 180° the taper is highly over-moded. This type of waveguide taper is utilized to feed a wide-band input coupler for gyrotron traveling wave amplifiers.

Equalization of Waveguide Delay Distortion

Microwave all-pass circuits, consisting of reactive networks used in conjunction with wide-band circulators or couplers, are described. An extremely useful all-pass circuit for minimizing phase distortion results when the restive network is a linear taper extending beyond cutoff. The delay characteristics of this circuit are well suited to the correction of the dispersive characteristics of TE or TM mode waveguides. Design formulas have been derived for the parameters of the tapers and a set of design curves is presented. The use of composite tapered sections and the use of tapers in conjunction with other equalizing circuits are described. Experimental results have been obtained for the phase of the reflection factor of a linear taper. Close agreement was observed between the results predicted by theory and the experimental data. Typical examples demonstrate that the time-delay variation of a length of uniform waveguide can be substantially reduced by linearly tapered waveguide equalizers.

Computation of wide-band waveguide directional couplers

Computation of wide-band waveguide directional couplers

A Wide-Band Directional Coupler for Wave Guide

The frequency range over which most types of directional couplers will operate is rather limited. This is especially true of wave-guide couplers, since the impedance of the guide changes with frequency. A new type of coupler is described which uses a small loop that responds to both the electric and the magnetic fields. When used in conjunction with a special section of ridge wave guide, it is possible to obtain excellent directional characteristics over a two-to-one frequency range.