Quadrature Hybrid Coupler Research Articles

Design of a miniaturized 90-degree quadrature hybrid coupler with harmonic suppression ability using π-shaped lumped elements

This research presents a new design and fabrication of a quadrature hybrid coupler using π-shaped lumped elements. The proposed π-shaped elements have resulted in ultra-size reduction and harmonic suppression ability simultaneously. The proposed coupler correctly works at 800 MHz, the insertion loss is less than 0.15 dB and more than 26 dB, isolation and return loss are obtained at the operating frequency. The size of the proposed coupler is only 12.8 mm ×12.2 mm, which is equal to 0.046 λg × 0.044 λg, where λg is of the guided-wavelength at 800 MHz. The conventional coupler has a large size of 0.25 λg × 0.25 λg, which is equal to 68.5 mm × 68.5 mm. The proposed coupler provides about 96% size reduction compared to the conventional coupler. Moreover, the proposed quadrature hybrid coupler has wide harmonic suppression from 2.1 GHz to 10 GHz.

Design of a Microwave Quadrature Hybrid Coupler with Harmonic Suppression Using Artificial Neural Networks

In this paper, a compact and simple structure of an elliptic microstrip lowpass filter (LPF) is designed for harmonic suppression in microwave quadrature hybrid coupler (QHC) applications. A radial resonator and a rectangular resonator are used to produce an elliptic LPF. The proposed LPF is used on the outer sides of the branch line coupler, which has improved the coupler harmonic suppression. Furthermore, artificial neural networks (ANNs) are incorporated to improve the LPF design process. The LPF best structure is obtained using the proposed ANN model. The proposed LPF has a compact size, which only occupies 16.4 mm × 7.3 mm equals to 0.164 λg × 0.073 λg, has a cut frequency of 2.2 GHz, and shows a sharp transmission band with a roll-off rate of 158.3 dB/GHz. Finally, the deigned QHC operates correctly at 1 GHz, which shows high harmonic suppression ability. The proposed QHC provides wide suppression band from 2.25 GHz up to more than 14 GHz, which can effectively suppress 3rd, to 14th harmonics. The proposed coupler features desirable parameters of S11, S21, S31, and S41, with magnitude of −21 dB, −3.4 dB, −3.3 dB, and −22.5 dB, at the operating frequency. The proposed approach mitigates the complexity of the circuit fabrication, compared with the previous methods while achieved desirable performances for the proposed QHC.

Non-magnetic four-port electronic circulators based on 90∘\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$90^\\circ $$\\end{document} non-reciprocal phase-shifters

This paper presents a family of four-port electronic circulators adhering to a new topology symmetry that enables linear, low-loss transistor-based circuit implementations. The underlying principle of operation employs a property of the 90∘\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$90^\\circ $$\\end{document} non-reciprocal phase shifter (NRPS) derived in this article. Under quadrature excitation, the NRPS transfers or reflects exciting signals depending on their respective phase lead. The fundamental topology consists of two back-to-back quadrature hybrid couplers with a 90∘\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$90^\\circ $$\\end{document} NRPS connected in parallel over the line of symmetry, interrupting the circuit’s reciprocity to achieve circular propagation by bypassing or reflecting at the NRPS but not through. We break down the circuit into three fundamental four-port sub-circuits. The transfer function of the cascaded sub-circuits enables an analysis with specific hybrid couplers. It also allows a synthesis of other four-port passive sub-circuits that, with an NRPS, achieve a four-port circulator transfer function by solving a matrix equation. Some of the mathematical solutions have circuit realizations, which are adjusted quadrature hybrid structures that differ from each other by the characteristic impedance of their arms. Two familiar solutions, including the standard quadrature hybrid and a modified design with equal Z0\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$Z_0$$\\end{document}, λ/4\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\lambda /4$$\\end{document} arms, are simulated utilizing lossless lumped element arms and a 4-Path, 65-nm NMOS 90∘\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$90^\\circ $$\\end{document} NRPS. The simulation results verify the theoretical analysis and enable a comparison between the performance of the two circuit solutions around 1 GHz. The four-port circulator with equal arms is implemented on a PCB and measured, yielding better than 1.5 dB insertion loss between the circulator ports, over 17 dB port-to-port reverse isolation, and better than 20 dBr port matching around 1 GHz.

Optimizing ultra-wideband balanced power amplifiers through the selection of different output impedance transformation based on SiP techniques

In this paper, two improved ultra-wideband (UWB) balanced power amplifiers based on the flip-chip system-in-package technique and electronic design automation (EDA) are proposed. The conventional approach to system-on-chip (SoC) involves integrating all sub-circuit designs into a single manufacturing process. However, in radio frequency circuits, adopting the SoC approach necessitates intricate matching designs, leading to an increase in development costs. In this study, two types of SiGe unit power amplifiers attempted to achieve a flat S21 response using simpler matching for input/output. The cascode architecture was adopted as the main structure for the first type of unit power amplifier (type I). Subsequently, the design of the second type unit power amplifier was built upon the foundation of the first type, with the only difference being the implementation of two parallel cascode structures (type II), and the primary goal is to enhance both gain and output power compared to the first type. In addition, for this second type unit power amplifier, in conjunction with a quadrature hybrid coupler, the optimal impedance matching value was selected to maintain the flatness of gain across the entire UWB range. Furthermore, the poor performance of S11,22 of these two types of unit power amplifiers was improved by using quadrature hybrid couplers using the WIPD process combined with EDA simulation. Therefore, using flip-chip packaging technology can effectively reduce the increased wafer fabrication costs caused by complex matching designs in active circuits. This improved system has the potential to offer a new practical application for UWB power amplifier design.

A 50-67GHz Transformer-Based Six-Port Balanced-to-Unbalanced Quadrature Hybrid Coupler

A 50-67GHz Transformer-Based Six-Port Balanced-to-Unbalanced Quadrature Hybrid Coupler

Design and Optimization of Nine-Section Broadband Quadrature Hybrid Coupler Using Strip Line Structure Focused on Thru and Coupled Characteristics

Design and Optimization of Nine-Section Broadband Quadrature Hybrid Coupler Using Strip Line Structure Focused on Thru and Coupled Characteristics

A Compact Microwave Quadrature Hybrid Coupler Using Capacitive Composite Lines and Meandered Stubs

In this paper, a new structure of the quadrature hybrid coupler (QHC) with compact size is proposed using capacitive composite lines and meandered open stubs. The proposed coupler works at 1.6 GHz with a 0.4 GHz bandwidth, which shows 25% fractional bandwidth (FBW). The proposed QHC occupies only 15 mm × 15 mm (0.12 λ × 0.12 λ), while the typical QHC size is 32 mm × 32 mm (0.25 λ × 25 λ) at the same working frequency. In the designed structure, two symmetric meandered stubs and two symmetric π-shaped composite networks including capacitors and microstrip lines are applied together. The designed QHC has a small size and occupies only 22% of the area of the conventional QHC, resulting in a 78% size reduction. The designed prototype has been analyzed, fabricated and tested, and the experimental results verify the simulated and analysis results. The results show a better than 27 dB return loss, more than 28 dB isolation between the output ports and less than 0.4 dB insertion loss at the working frequency of 1600 MHz. With the achieved desirable specifications, the fabricated QHC is a suitable choice for wireless microwave applications.

Design of a Broadband Comparator Network at $X$-Band

This paper presents a novel broadband comparator network design operating at X-band. A multilayer aperture coupling scheme and shielding around the microstrip structures are utilized to achieve broadband performance. There are two main building blocks of the proposed comparator network. These are a quadrature hybrid coupler and a 90-degree phase shifter. These two main components are designed to have broadband performance so that the designed comparator would also have wideband performance. The proposed quadrature hybrid coupler achieves more than 19.7 dB return loss, a 0.75 dB amplitude imbalance, and 1.4 ° phase imbalance along the frequency band 5 GHz to 10 GHz. The 90-deg. phase shifter has less than -10 dB S11 in addition to having less than 1.6 °. phase error and 1.5 dB insertion loss within the frequency band 5 GHz to 9.9 GHz. The proposed comparator is acquired by combining the multiple quadrature hybrid couplers and phase shifters. The results of the manufactured and simulated comparator agree well with each other. The impedance bandwidth (VSWR<2) of the manufactured comparator is <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\%$</tex-math></inline-formula> 61 and operates from 5.26 GHz to 9.9 GHz. An 8x8 microstrip patch antenna array is designed and manufactured to verify the comparator network's sum and diff pattern forming capability. The far-field measurements of the proposed comparator combined with the 8x8 antenna array indicate that 36 dB null depth is acquired at the azimuth plane, and 40 dB null depth is achieved at the elevation plane.

Design and fabrication of a compact branch-line hybrid coupler with a balanced phase using a new microstrip structure for GSM applications

A novel microstrip quadrature hybrid coupler is mathematically designed, optimized and fabricated in this work. The physical structure of the proposed coupler is new and it occupies a very small area of 0.01 λg2. The novel stubs embedded inside the conventional rectangle are connected parallel lines. The ends of these stubs are connected to a solid rectangle, which make the overall structure different from the previous works. Our branch-line coupler is designed to work at 1.8 GHz for GSM applications. The phase imbalance between S21 and S31 is only 0.01°, which is very small compared to the previous works. Another advantage of the presented coupler is its high isolation, which is about 40 dB. Meanwhile, other parameters such as common port return loss and coupling factors are desired. To design this coupler, two low-loss lowpass filters (LPFs) are designed and embedded in the main structure. A mathematical design method is presented to decrease the losses, where a 0.002 dB insertion loss for the LPF is achieved. We measured the presented structure. The measurement results verifies the simulations with high accuracy. Therefore, due to having a novel structure, very small size, the lowest phase shift, good isolation and good return loss the proposed coupler can be easily used in RF communication systems.

A Passive Wideband Noise-Canceling Mixer-First Architecture With Shared Antenna Interface for Interferer-Tolerant Wake-Up Receivers and Low-Noise Primary Receivers.

Wake-up receivers (WuRX) present an opportunity to reduce average power consumption of IoT transceivers, however achieving sensitivity and interferer tolerance while providing wideband matching and sharing an antenna interface present a significant challenge for existing architectures. This paper presents a primary/WuRX which utilizes a quadrature hybrid coupler based N-Path mixer first architecture to simultaneously achieve low noise, wideband matching and a shared antenna interface. The passive-mixer first approach and a two-code modulated multi-tone signaling scheme provide interferer tolerance in the WuRX. The paper analyzes gain/power trade-offs in the proposed architecture in the context of noise impact with multi-tone WuRX signaling. The proposed architecture is implemented in 65 nm CMOS and occupies 2.25 mm 2. The primary RX achieves 3.8 dB NF and 0.75 dBm out-of-band P1dB with 440μW power consumption. The WuRX achieves -86 dBm sensitivity for 10kb/s data rate and up to -40 dB signal-to-interferer ratio (SIR) with 171μW power consumption.

Design of a Three-Branch Line Quadrature Hybrid Coupler with Reduced Size

This paper presents a design of a three-branch line quadrature hybrid coupler with reduced size implemented in the microstrip line. The designed coupler is to be used in the feeding of a crossed-dipole circularly polarized antenna for receiving GNSS signals at 1.16-1.61 ㎓. The performances of the two- and three-branch line couplers are investigated first. Characteristic impedances of the three branch lines are adjusted for a better balance in coupling coefficients. To reduce the size of the three-branch line coupler, the main lines are meandered inward and outward using the optimized coupler. Meandering reduces the size of the quadrature hybrid coupler by 35.2% in one direction. The outward-meandered coupler shows slightly larger bandwidth than the inward-meandered design. The outward-meandered coupler shows magnitude and phase imbalances of 0.36 ㏈/0.7° at 1.16 ㎓, and 0.43 ㏈/0.8° at 1.61 ㎓.

Single-Ridge Waveguide Compact and Wideband Hybrid Couplers for X/Ku-Band Applications

Hybrid couplers are important devices that combine or divide signals in various microwave applications. Wideband performance, low losses and small size are key features in most modern radar and communication systems. This paper presents a new geometry for single-ridge, air-filled waveguide quadrature hybrid couplers at the X/Ku band on a single layer using multiple pairs of slots cut on a common ridge coupling section. Bandwidth can be progressively extended by increasing the number of slot pairs. Two designs characterized by compact size and state-of-the-art performance are proposed, leading to a fractional bandwidth up to 46.88% and a maximum dimension of 1.18 wavelengths. A tolerance analysis is presented to highlight the design robustness and reliability.

An Ultra-Compact Full-Band Waveguide Quadrature Hybrid Coupler

This work proposes an easily scalable quadrature hybrid coupler (QHC) topology with two symmetric stepped apertures that originate a square coaxial-like mid-section. This new configuration enables an ultra-compact design, three times shorter than equivalent structures, having 40% of fractional bandwidth with 25 dB of matching/isolation and 1 dB of axial ratio (AR). The impedance transformers can be easily redesigned to meet other requirements related to electrical performance or even other desired coupling values. For verification purposes, a prototype at <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Ku</i> -band was manufactured and measured showing good agreement with simulation results.

Low-Profile Wideband Solar-Cell-Integrated Circularly Polarized CubeSat Antenna for the Internet of Space Things

This paper proposes a low-profile wideband circularly polarized (CP) antenna using solar cell patches as radiation elements and a sequentially rotated feeding network for CubeSat applications. To realize a wide axial ratio (AR) bandwidth with a compact size, a sequentially rotated feeding network was designed by modifying a quadrature hybrid coupler and a rat-race coupler that has a small change in phase difference even when the frequency changes. A wideband CP patch array antenna was designed by combining a C-shaped slot-coupled solar cell patch in conjunction with a novel feeding network. The overall size of the proposed CP CubeSat antenna is 100 &#x00D7; 100 &#x00D7; 7.2 mm³ (0.83 &#x03BB;_o &#x00D7; 0.83 &#x03BB;_o &#x00D7; 0.06 &#x03BB;_o at 2.5 GHz). Solar cells occupy 79% of the antenna area, enabling efficient energy harvesting. The &#x2013;10 dB impedance bandwidth is 1.98&#x2013;3.0 GHz, which is a fractional bandwidth of approximately 41.0%. The 3-dB AR and 3-dB gain bandwidths are 1.98&#x2013;3.0 GHz (41.0%) and 1.82&#x2013;2.98 GHz (46.6%), respectively. The proposed CP solar patch array antenna demonstrates a constant radiation pattern within the &#x2013;10 dB impedance bandwidth. The proposed CubeSat antenna is suitable for use in an Internet of Space Things (IoST) autonomous communication system.

A Millimeter-Wave Mutual-Coupling-Resilient Double-Quadrature Transmitter for 5G Applications

This article presents a wideband energy-efficient transmitter (TX) for 5G mm-wave phased-array systems. It features an advanced double-quadrature direct upconverter (DQ-DUC) to improve its in-band linearity and spectral purity. The proposed TX architecture incorporates an efficiency-enhanced balanced power amplifier (EEBPA) that mitigates VSWR fluctuations in phased-array systems while enhancing efficiency at power back-off (PBO). The EEBPA comprises two identical series-Doherty power amplifiers (PAs) combined through a quadrature hybrid coupler forming a balanced PA. The proposed DQ-DUC consists of a pair of I/Q modulators and the proposed EEBPA’s quadrature combiner to further suppress the I/Q image. To verify the proposed techniques, a 40-nm CMOS prototype is implemented. It delivers 20 dBm <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$P~_{\text {1 dB}}$ </tex-math></inline-formula> with 40%/31% drain efficiency at <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$P~_{\text {1 dB}}$ </tex-math></inline-formula> /6-dB PBO. The measured TX output reflection coefficient is better than −18 dB over a 22.5–30-GHz band. Its intrinsic LO feedthrough and image-rejection ratio for a 100-MHz tone spacing over a 24–30-GHz band are better than −45 dBc/50 dB, respectively, without calibration. The average error vector magnitude (EVM) is better than −27.1 dB without digital pre-distortion for an eight-carrier “100-MHz 64-QAM OFDM” signal with an 800-MHz aggregated bandwidth while generating an average output power of 8.4 dBm with 10.8% drain efficiency. Its maximum forward-power/EVM deviations are better than 0.3/1.65 dB, respectively, for a “100-MHz 64-QAM” signal under a voltage standing wave ratio of 3.

Linear-polarization metasurface converter with an arbitrary polarization rotating angle

This paper presents a new design of linear-polarization metasurface converter with arbitrary polarization rotating angle. The linear-polarization conversion is achieved by first separating the linearly polarized incident wave into two orthogonal circularly polarized waves, then adding an additional phase to one of the circularly polarized waves, and finally recombining these two circularly polarized waves into a linearly polarized wave and reflecting it towards free space. A practical unit cell operating at 10 GHz with sandwich structure is applied to realize the linear-polarization metasurface converter, which consists of a top-layer square patch, a middle-layer ground plane, a bottom-layer 90° quadrature hybrid coupler, and two vias connecting the top layer and bottom layer. The proposed linear-polarization metasurface converter is analyzed theoretically and demonstrated by both simulating and experimental results.

Design of wideband multi-layer quadrature hybrid couplers with butterfly shaped resonators

AbstractIn this paper, a wideband quadrature hybrid coupler is presented. The proposed structure has a multi-layer microstrip topology. In this topology, there are three substrate layers including prepreg material and four conductive layers. In order to achieve equal power division between through and coupled arms of the directional coupler while maintaining a 90° phase shift, aperture coupling between the resonators located at both top and bottom layers is utilized. So as to avoid any unwanted effects of prepreg material in such multilayer topology, via shielding around resonators are inserted. In this study, coupling from input ports to output ports is accomplished by the shielded butterfly shaped slot etched to the ground layer of top and bottom layers. The proposed design operates within 3–12 GHz. The acquired phase imbalance between the coupled ports is &lt;±2.5°. The results of the manufactured quadrature hybrid coupler agree well with the simulated results.

Current-Injected Load-Modulated Outphasing Amplifier for Extended Power Range Operation

In this letter, the power range to be covered with maximized efficiency by a two-way outphasing power amplifier (PA) is significantly extended, thanks to a proposed architecture with the injection of an external signal. Using a reactively terminated quadrature hybrid coupler (QHC) as nonisolating combiner, the Chireix topology is transformed into a slight variation in the load-modulated balanced amplifier (LMBA) when the auxiliary branch is activated. This combined load-modulated (LM) strategy provides a nearly resistive loading of the individual outphasing PAs over a wide power range. An appropriate output network, approximating a class-E/F2 operation of the selected GaN-HEMT device under such loading condition, leads to remarkable drain efficiency figures at deep output power back off (OPBO). Values higher than 80%, 70%, and 60% have been measured at power levels 9.5, 13.3, and 15 dB below its peak (45.7 dBm), respectively. A 5-MHz Long Term Evolution (LTE) signal with a peak-to-average power ratio (PAPR) as high as 12.65 dB has been reproduced with an average efficiency above 62% and worst-case adjacent channel leakage ratio (ACLR) of −31 dBc.

A Compact Wideband Millimeter-Wave Quadrature Hybrid Coupler Using Artificial Transmission Lines on a Glass Substrate

In this letter, a compact branch-line-based quadrature hybrid coupler using a line miniaturization technique for a 28-GHz application is presented. Coplanar waveguide-based artificial transmission lines are used in the miniaturization, and T-equivalent circuit models are exploited to elaborate on the optimization method. A multistage T-model is utilized to eliminate the need for lumped elements, improve bandwidth performance, and simplify the fabrication process. To validate the proposed approach, the designed quadrature hybrid coupler was fabricated on a glass substrate. The measured insertion loss and phase difference at 28 GHz were 3.86 dB, 3.94 dB, and 90.4°, respectively. The output amplitude imbalance was within a 1-dB range from 25.3 to 31.0 GHz, and the total device area, excluding the measurement pad, was $1.15\times0.98$ mm2.

Antenna rectifier using quadrature hybrid coupler for power‐harvesting applications

This article presents the design, simulation, fabrication, and measurement of a compact power-harvesting circuit. A quadrature hybrid coupler is used for this harvesting circuit because of its advantageous matching, high isolation, and lossless characteristic. It properly feeds the bridge rectifier, combining the signals received with two antennas. The bridge rectifier component is a turnout full-wave rectification from a two-wire alternative current input. The measurements found output power to be −25.5 dBm using a 5 KΩ load resistor, at 5 GHz. The transmitter antenna input power level is 7 dBm, at 50 cm distance. Both results of the Friis Equation and the measurements are in agreement. According to the results, the power-harvesting circuit can operate for wireless local area network sensor applications.