Branch-line Hybrid Research Articles

A Defected Ground Structure without Ground Contact Problem and Application to Branch Line Couplers

A new defected ground structure (DGS) microstrip line that is free from the ground contact problem is described together with its application example. The proposed DGS microstrip line adopts a double-layered substrate. The first layer contains the microstrip line and DGS patterns on the top and bottom planes as with the conventional DGS line. The second substrate, of which upper metal plane has already been removed, is attached to the bottom ground plane of the first layer. This structure prevents the ground plane of the first substrate with DGS patterns from making contact with the metal housing. The proposed DGS microstrip line has advantageous transmission and rejection characteristics, without the ground contact problem of DGS patterns, which has been a critical problem of previous DGS lines. A 10 dB branch line hybrid coupler is designed and measured, as an example of application of the proposed DGS microstrip line.

MINIATURIZED HYBRID BRANCH LINE COUPLERS BASED ON A SQUARE-SPLIT RESONATOR LOADING TECHNIQUE

In this paper, new miniaturized hybrid branch line couplers loaded by square-split ring resonators are proposed. This loading technique increases the electrical length of transmission lines by patterning the ground plane under the conductor trace in microstrip lines with the complementary, dual-behavior, configuration of squaresplit ring resonators. Each branch is loaded by one resonator in the first coupler and by two resonators in the second coupler. Hence, compact sizes of 9.29mm × 9.57mm, and 8.88mm × 9.11mm, or equivalently 0.2λg × 0.2λg and 0.19λg × 0.19λg, respectively, are obtained at the operation frequency, 2.4GHz. This corresponds to 66.14% and 60.18% of a conventional structure’s area, respectively. Moreover, the new designs can suppress higher harmonic components due to the bandstop response of the square-split resonators at their resonant frequency while maintaining similar measured performance compared to the conventional branch-line hybrid coupler. Measured and simulated responses are in very good agreement which validates the proposed structures and technique. This technique can also be applied to minimize the size of other microwave circuits.

A COMPACT STACKED CIRCULARLY POLARIZED ANNULAR-RING MICROSTRIP ANTENNA FOR GPS APPLICATIONS

A novel design of circularly polarized (CP) annular-ring microstrip antenna (ARMSA) working in TM11 mode is presented. The CP radiations of the proposed antenna are implemented by a 90 - branch-line hybrid coupler placed at the inner part of the ARMSA. Since the ARMSA has narrow bandwidth and high-input impedance, a circular parasitic patch suspended above the ring is employed for not only improving the impedance matching and bandwidth, but enhancing the performances of axial ratio (AR). Due to the utilizing of parasitic patch and circular hybrid, the measured results are shown to attain a 10-dB return loss bandwidth of 31.2% (1300{1780MHz) and a 3-dB AR bandwidth of 19.2% (1360{1650MHz) respectively. The CP gain is 8.2dB at 1.575GHz. The proposed antenna is low proflle and has a simple structure, therefore, it can be a good candidate for GPS portable terminal applications.

New approach to a fast and accurate design of microwave circuits with complex topologies

A robust simulation-driven design methodology of microwave circuits with complex topologies has been presented. The general method elaborated is suitable for a wide class of N-port unconventional microwave circuits constructed as a deviation from classic design solutions. The key idea of the approach proposed lies in an iterative redesign of a conventional circuit by a sequential modification and optimisation of its atomic building blocks. The speed and accuracy of the method presented has been acquired by solving a number of simple optimisation problems through surrogate-based optimisation (SBO) techniques, which offer a satisfactory approximation of the optimal design solution. Two exemplary designs have been supplied to verify the method introduced. An abbreviated wideband quarter-wave impedance matching transformer and a miniaturised hybrid branch–line coupler have been developed. Diminished dimensions of the circuits under construction have been achieved by means of compact microstrip resonant cells. As an SBO engine, an implicit space mapping technique has been utilised. The final results have been acquired in only a fraction of time that is necessary for a direct electromagnetic (EM) optimisation to generate competitive results. An experimental validation of the method proving its high utility has been provided.

Wideband 18–40 GHz Surface Micromachined Branchline Quadrature Hybrid

This letter demonstrates two 18-40 GHz rectangular coaxial branchline quadrature hybrids designed using circuit and full-wave simulations. The chosen topologies are fabricated in a surface micromachining technology PolyStrata. Measured in-band performance of baseline wideband branchline hybrid shows |S <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</sub> |<;-10dB, |S <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">21</sub> | = -4.1 ± 1dB, and |S <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">31</sub> | = -4.3 ± 0.7 dB. This hybrid is miniaturized by meandering the rectangular coaxial lines to obtain 57% reduction in surface area and in-band performance with |S <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</sub> | <; -10dB, |S <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">21</sub> |= -4.2±1.2dB, and |S <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">31</sub> | = -4.1 ± 0.7 dB.

High-efficiency three-way Ka-band waveguide unequal power combiner

This article presents the design, simulation and characterisation of a novel high-efficiency Ka-band (32.05 ± 0.25 GHz) rectangular waveguide three-way serial combiner for monolithic microwave integrated circuit power amplifiers (PAs) with unequal output power. The combiner presented here is suited for low data rate communications from deep space using a single carrier with constant envelope (amplitude) type modulation. The three-way combiner consists internally of two branch-line hybrids connected in series by a short length of waveguide. The two branch-line hybrids were each designed to combine two input signals that are equal in phase and with an amplitude ratio of two, although in general the amplitude ratio could be arbitrary. The combiner was fabricated in an E -plane split-block arrangement and precision machined from blocks of aluminium with standard WR-28 waveguide ports. S -parameter measurements demonstrated a close achievement of the design goals. The measured return loss at the output port was greater than 16 dB and the isolation between the three input ports of the three-way combiner were greater than 22 dB. The combining of three PAs was successfully demonstrated in which the measured combining efficiency was greater than 90% at the centre frequency of 32.05 GHz.

삼각 패치형 인공 전송 선로를 이용한 브랜치 라인 하이브리드

본 논문에서는 슬롯을 갖는 삼각 패치형 인공 전송 선로를 이용한 브랜치 라인 하이브리드를 제안한다. 제안된 인공 전송 선로는 구조가 콤팩트하고 슬롯의 파라미터들을 변화시킴으로써 선로의 특성 임피던스와 전기적 길이를 조절하는 데 용이하여 일반적인 전송 선로를 소형화시키는 데 유용하다. 제안된 브랜치 라인 하이브리드는 이러한 직각 삼각형의 인공 전송 선로들을 이용하여 구현되었기 때문에 공간의 활용도가 높고 소형화되었다. 제작된 3 dB 브랜치 라인 하이브리드는 중심 주파수 2.45 GHz의 15 % 대역폭 내에서 <TEX>${\pm}0.5$</TEX> dB의 결합도 변화 특성과 두 출력 포트 간 <TEX>$91^{\circ}{\pm}4^{\circ}$</TEX>의 위상차 특성을 보였다. 또한, 제안된 브랜치 라인 하이브리드의 크기는 일반적인 브랜치 라인 하이브리드 크기의 38 %이다. A branch-line hybrid using microstrip artificial transmission lines(ATLs) with slotted-triangular patches is proposed. The proposed artificial transmission line is compact in structure as well as easy to adjust the characteristic impedance and electrical length of equivalent transmission line by changing the slot's parameters; hence, it is useful for miniaturizing conventional transmission lines. The designed branch-line hybrid, because of the use of the right angled isosceles triangular shaped artificial transmission lines as building blocks, has no useless empty space, and hence optimally miniaturized. A fabricated 3 dB branch-line hybrid shows the coupling variation of <TEX>${\pm}0.5$</TEX> dB and the phase difference between two output ports of <TEX>$91^{\circ}{\pm}4^{\circ}$</TEX> within 15 % bandwidth at 2.45 GHz center frequency. The size of proposed branch-line hybrid is only 38% of the conventional branch-line hybrid.

Dual-band branch-line hybrid with distinct power division ratio over the two bands

This article presents a novel methodology for the design of transmission line-based dual-band branch-line hybrid with distinct power division over any two specified frequencies. These distinct power divisions at specified frequencies are achieved while keeping the quadrature relation intact at both the frequencies. To demonstrate the effectiveness of the proposed technique, a prototype of dual-band uneven branch-line hybrid operating at 1960 and 3500 MHz has been designed for use in Wideband Code Division Multiple Access (WCDMA) and Worldwide Interoperability for Microwave Access (WiMax) applications. The designed hybrid possesses equal power division in the WCDMA band and 3-dB unequal power division in the WiMax band. © 2012 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2013.

A NOVEL WIDEBAND CIRCULARLY POLARIZED ANTENNA FOR WORLDWIDE UHF BAND RFID READER APPLICATIONS

This paper presents the novel design of a wideband circularly polarized (CP) Radio Frequency Identiflcation (RFID) reader microstrip patch antenna for worldwide Ultra High Frequency (UHF) band which covers 840{960MHz. The proposed antenna, which consists of a microstrip patch with truncated corners and a cross slot, is placed on a foam substrate (r = 1:06) above a ground plane and is fed through vias through ground plane holes that extend from the quadrature 3dB branch line hybrid coupler placed below the ground plane. This helps to separate feed network radiation, from the patch antenna and keeping the CP purity. The prototype antenna was fabricated with a total size of 225 £ 250 £ 12:8mm 3 which shows a measured impedance matching band of 840{1150MHz (31.2%) as well as measured rotating linear based circularly polarized radiation patterns. The simulated and measured 3dB Axial Ratio (AR) bandwidth is better than 23% from 840{1050MHz meeting and exceeding the target worldwide RFID UHF band.

Wideband directional elliptic coupler based on CB-CPW technology

A new wideband 3 dB directional coupler based on CB-CPW technology is presented and implemented. The proposed coupler is elliptic, offering a wide bandwidth compared to the conventional branched-arm hybrid technology. In fact, simulated and measured results show a better performance, especially in terms of bandwidth (∼50%) compared to conventional CPW branch-line hybrid couplers. This novel architecture is useful for low-cost wideband applications.

메타물질 전송선로를 이용한 이중대역 평형증폭기

This paper describes a design of dual band balanced amplifier using a lefted handed meta-material transmission line structure for high frequency application. Meta-material transmission lines have been known to have dual band frequency responses. A dual band branch line hybrid coupler is designed using the meta-material transmission lines, and measured at first. Two identical dual band amplifiers are also designed, built and tested using the same meta-material transmission structure. The proposed dual band balanced amplifier is composed of those dual band branch line hybrid coupler and amplifiers. In order to suggest an design example, a prototype of dual band balanced amplifier is built and measured at the dual frequencies, 1800㎒(f₁) and 2300㎒(f₂). The simulation and measurement show that the fabricated balanced amplifier operates well at the desired dual frequencies bands with the gain of 11.12㏈ and 17.67㏈ at f₁ and f₂, respectively, with a good agreement with the simulation results.

Miniaturisation and harmonic suppression of the branch-line hybrid coupler

In this article, two compact structures of the branch-line hybrid coupler (BLC) which can suppress upper order harmonics of the conventional BLC are proposed. By replacing the microstrip transmission lines at any electrical length of the conventional BLC with their equivalent new T-type transmission lines, two compact BLCs that can suppress upper order harmonics are achieved. Design equations of the proposed T-type line are achieved by ABCD matrices. To validate the design concept, first, a compact BLC which utilises a proposed T-type line in each of its branch is designed and fabricated to suppress the second to the eighth harmonics. Furthermore, the first BLC is analysed by even- and odd-mode analyses and the scattering parameter matrix of the first BLC is calculated at the first to eighth harmonics. There is an excellent agreement between simulated and measured results. Then, a compact BLC which uses two proposed T-type lines in each of its branch is designed at 1 GHz to suppress the second to the fifth harmonics and the second to sixth harmonics, simultaneously. The first- and second-proposed structures are 50% and 46% of the conventional BLC, respectively, while maintaining the characteristics of the conventional BLC at the fundamental frequency.

A Miniaturized 3 dB Branch-Line Hybrid Coupler With Harmonics Suppression

This letter presents a miniaturized 3 dB branch-line hybrid coupler with second harmonic suppression using high-impedance transmission lines and interdigitated shunt capacitors. By using the interdigitated capacitors shunt with the transmission lines, further minimization of the 3 dB branch-line hybrid coupler can be achieved compared with previously reported techniques. The design of the interdigitated shunt capacitors requires concurrent optimization of the capacitance to the ground and the edge-coupling interdigitated capacitance between the ports. For validation, a miniaturized 3 dB branch-line hybrid coupler at 836.5 MHz was designed and implemented. The proposed 3 dB branch-line hybrid coupler achieved a compact size of 27.75 mm × 25.7 mm, or equivalently 0.077λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">o</sub> ×0.072λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">o</sub> , where λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">o</sub> is the free-space wavelength. Moreover, the coupler can suppress second harmonic components by 20 dB while maintaining similar measured performance compared to the conventional branch-line hybrid coupler.

HIGH EFFICIENCY KA-BAND MMIC SSPA POWER COMBINER FOR NASA'S SPACE COMMUNICATIONS

In this paper, we will review the design, construction and performance of the two-way Ka -band waveguide branch-line and asymmetric magic- T based unequal power combiners. The manufactured combiners were designed to combine input signals that are equal in phase and with an amplitude ratio of two. Next, the design, construction and performance of a three-way branch-line unequal power combiner, achieved by serially interconnecting two 2-way branch-line hybrids and optimizing the dimensions using software tools, is presented. The application of the two-way and three-way combiners for combining the output from two or three MMIC PAs was demonstrated. The observed efficiencies for all three power combining configurations are 90 percent or greater at Ka -band (31.8 to 32.3 GHz).

Dual-band microwave duplexer based on spiral resonators (SR) and complementary split ring resonators (CSRR)

In this work, a microstrip dual-band microwave duplexer implemented by means of a pair of dual-band branch-line hybrid couplers and a pair of dual-band band-stop filters is presented. The hybrid couplers are implemented by using complementary split ring resonators (CSRRs), etched in the ground plane, while the band-stop filters are made of spiral resonators (SRs) coupled to the host line. The measured duplexer characteristics are good and the device is compact by virtue of the small electrical size of the employed resonant elements. From this paper, it is clear that CSRRs and SRs are useful particles for the design of dual-band microwave systems requiring various microwave components.

Miniaturization and harmonic suppression of the branch-line coupler based on radial stubs

In this article, a compact branch-line hybrid coupler (BLC) which can suppress upper order harmonics of the conventional BLC is proposed. By adding a radial stub in the center of each branch, a compact BLC which can suppress the upper order harmonics are achieved. The proposed BLC is designed and simulated at 0.93GHz. The proposed structure is 27% of the conventional BLC, while maintaining the characteristics of the conventional BLC at the center frequency. There are two transmission zeroes at 3.6 and 5.6GHz. The third upto seventh harmonic are suppressed at least 20dB.

Planar Multi-Band Microwave Components Based on the Generalized Composite Right/Left Handed Transmission Line Concept

This paper is focused on the design of generalized composite right/left handed (CRLH) transmission lines in a fully planar configuration, that is, without the use of surface-mount components. These artificial lines exhibit multiple, alternating backward and forward-transmission bands, and are therefore useful for the synthesis of multi-band microwave components. Specifically, a quad-band power splitter, a quad-band branch line hybrid coupler and a dual-bandpass filter, all of them based on fourth-order CRLH lines (i.e., lines exhibiting 2 left-handed and 2 right-handed bands alternating), are presented in this paper. The accurate circuit models, including parasitics, of the structures under consideration (based on electrically small planar resonators), as well as the detailed procedure for the synthesis of these lines using such circuit models, are given. It will be shown that satisfactory results in terms of performance and size can be obtained through the proposed approach, fully compatible with planar technology.

Microwave Dual-Band Bandpass Planar Filters Based on Generalized Branch-Line Hybrids

A new class of microwave dual-band bandpass planar filter is reported. It uses an original generalized branch-line hybrid topology devised here, operating as dual-passband transversal filtering section. This type of filter network, under feedforward signal-interaction concepts, enables dual-band bandpass filtering actions with transmission zeros to be generated. Some design formulas and guidelines helping to synthesize the proposed dual-passband transversal filtering section are given. Furthermore, to prove its practical viability, theoretical, simulated and experimental results of two manufactured sharp-rejection dual-band bandpass microstrip filter prototypes are shown.

Analysis of miniaturized 3 dB branch-line hybrid couplers using distributed MIM capacitors

This letter presents the trade-off between size reduction and electrical performance of miniaturized branch line couplers using distributed capacitors placed in the inner open area of the hybrid. Based on single, double, and triple II-section approximations of the quarter wavelength transmission lines of a conventional design with high impedance lines and shunt metal-insulator-metal (MIM) capacitors, size reduction as well as electrical performance are compared both in simulation and experimentally. The miniaturized triple-section hybrid achieves similar bandwidth performance as the conventional 3 dB branch line hybrid coupler, but with a 61.2% smaller footprint. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52: 1553–1556, 2010; Published online in Wiley InterScience (www.interscience. wiley.com). DOI 10.1002/mop.25273

Equivalent Transmission-Line Sections for Very High Impedances and Their Application to Branch-Line Hybrids with Very Weak Coupling Power

As operating frequency is raised and as more integration with active and passive elements is required, it becomes difficult to fabricate more than 120 <TEX>${\Omega}$</TEX> characteristic impedance of a mierostrip line. To solve this problem, an equivalent high impedance transmission-line section is suggested, which consists mainly of a pair of coupled-line sections with two shorts. However, it becomes a transmission-line section only when its electrical length is fixed and its coupling power is more than half. To have transmission-line characteristics(perfect matching), independently of coupling power and electrical length, two identical open stubs are added and conventional design equations of evenand odd-mode impedances are modified, based on the fact that the modified design equations have the linear combinations of conventional ones. The high impedance transmission-line section is a passive component and therefore should be perfectly matched, at least at a design center frequency. For this, two different solutions are derived for the added open stub and two types of high impedance transmission-line sections with 160 <TEX>${\Omega}$</TEX> characteristic impedance are simulated as the electrical lengths of the coupled-line sections are varied. The simulation results show that the determination of the available bandwidth location depends on which solution is chosen. As an application, branch-line hybrids with very weak coupling power are investigated, depending on where an isolated port is located, and two types of branch-line hybrids are derived for each case. To verify the derived branch-line hybrids, a microstrip branch-line hybrid with -15 dB coupling power, composed of two 90<TEX>$^{\circ}$</TEX> and two 270<TEX>$^{\circ}$</TEX> transmission-line sections, is fabricated on a substrate of <TEX>${\varepsilon}_r$</TEX>= 3.4 and h=0.76 mm and measured. In this case, 276.7 <TEX>${\Omega}$</TEX> characteristic impedance is fabricated using the suggested high impedance transmission-line sections. The measured coupling power is -14.5 dB, isolation and matching is almost perfect at a design center frequency of 2 GHz, showing good agreement with the prediction.