Quadrature Coupler Research Articles

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 ㎓.

A 200–250-GHz Phase Shifter Utilizing a Compact and Wideband Differential Quadrature Coupler

This letter presents the design of a 200–250-GHz compact vector modulator (VM) phase shifter in a 0.13- <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \text{m}$ </tex-math></inline-formula> SiGe bipolar complementary metal-oxide-semiconductor (BiCMOS) technology. A compact, low-loss, and wideband differential quadrature coupler is used to generate differential I/Q signals. The design details of the millimeter-wave wideband differential coupler is presented and compared with other I/Q generators by the 3-D electromagnetic (EM)-simulated results. The VM core is realized by two variable gain amplifiers based on Gilbert cell architecture. The measured phase shifter shows a gain of −10.3 dB for the maximum gain setting at 230 GHz. The phase shifter shows a −17 dB of gain for full 360° phase tuning range and a 10 dB of gain control. The maximum rms gain error and the phase error are 1.25 dB and 10°, respectively, from 200 to 250 GHz. The chip consumes a dc power of 55 mW and occupies a core area of 0.09 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> .

A compact design of a wideband millimeter‐wave Butler matrix using integrated passive device technology

This study presents a compact, wideband, 4 × 4 Butler matrix using a two-metal-layer thin-film process for millimeter (mm)-wave 5G radio applications. Size reduction techniques are thoroughly discussed for size and performance optimization. A size-reduced quadrature coupler is designed with coplanar waveguide based length-reduced branch lines using capacitive loading effect from the ground bridges. A compact crossover is designed for a return loss of 20 dB or more with negligible crosstalk over a wide frequency range. The circuit components are arranged in an optimized space, allowing negligible coupling between nearby elements. The Butler matrix is fabricated on a quartz substrate at the center frequency of 28 GHz. The fractional bandwidth is 15.4% at a 15-dB return loss and insertion loss is measured in the range of 7.8–8.7 dB at the center frequency. The size of the core circuit is 3.375 × 2.100 m m 2 ${\rm{m}}{{\rm{m}}}^{2}$ , which corresponds to 0.469 × 0.292 λ g 2 ${\lambda }_{g}^{2}$ .

Design and Application of Novel Single- and Dual-Band Reconfigurable Microwave Components With Filter and Coupler Functions

In this article, novel single- and dual-band reconfigurable microwave component (RMC) designs with very compact circuit sizes are proposed, which can be reconfigured into multiple functions, including a bandpass filter, a bandstop filter, and a quadrature coupler. The proposed RMCs with filter and coupler functions are based on lumped elements and transistor-based switches such that they are very suitable for on-chip implementation. Specifically, the proposed 10-GHz RMC in GaAs can achieve the functions of a bandpass filter, a bandstop filter, and a quadrature coupler with a circuit size of only 1.8 mm <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\times1.35$ </tex-math></inline-formula> mm. On the other hand, the proposed 9.5/24-GHz RMC in GaAs can be reconfigured as either a dual-band bandpass filter or a dual-band quadrature coupler, while the circuit size is only 1.36 mm <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\times1.15$ </tex-math></inline-formula> mm. In addition, to demonstrate the possible application of the proposed RMC designs, a proof-of-concept 2.45-GHz radar system prototype based on a proposed 2.45-GHz RMC is implemented in PCB, which successfully integrates the functions of target speed detection and transmission in a single hardware.

Dual tuned 1H/31P quadrature microstripline-based transmit/receive switch for 7 Tesla magnetic resonance imaging

&lt;p&gt;&lt;span&gt;A dual tuned transmit/receive (T/R) Switch for 7 tesla magnetic resonance imaging&lt;/span&gt; (MRI) that is based on concentric microstripline (MSL) coupler is introduced. The proposed switch is designed using two concentric MSL quadrature couplers on the top and bottom faces of the switch. The switch can be used to handle two frequency signals to/from two radio frequency (RF) coils. In this article, a 1H/31P atomic nuclei are excited. The two MSLs on the upper face of the switch are designed to transmit 298 and 120.6 MHz signals into RF coils, whereas each of the identical upper and lower MSLs are used to receive these signals from the RF coils. This switch can be used to transmit/receive signals from two RF coils at the same time, one work with 1H and the second with 31P atomic nuclei, and without any tuning. The proposed switch has been designed and simulated using the electromagnetic microwave studio computer simulation technology (CST). It demonstrates good matching (≈17 dB), low insertion loss (≈0.3) and high isolation (&amp;gt;70) for the 1H and 31P magnetic resonance signals at transmit mode. During receive mode, It demonstrates good matching (&amp;gt;20 dB), low insertion loss (≈0.2) and high isolation (&amp;gt;70) for the 1H and 31P magnetic resonance signals.&lt;/p&gt;

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.

Simulation Design of 3dB Orthogonal Directional Coupler

Directional couplers can isolate, mix, and orient signals, and play an important role in RF circuits. In this paper, the quadrature coupler is firstly analyzed theoretically. According to the results of the theoretical analysis, a microstrip 3dB quadrature directional coupler with a new structure based on 2.2GHz is designed using ADS after the design objective is given. After repeated simulation optimization, the coupling degree is optimal.

Continuous-Mode Hybrid Asymmetrical Load- Modulated Balanced Amplifier With Three-Way Modulation and Multi-Band Reconfigurability

This article introduces a novel high-order load modulation power amplifier (PA) architecture, i.e., continuous-mode hybrid asymmetric load modulated balanced amplifier (H-ALMBA). The two sub-amplifiers (BA1 and BA2) of the balanced topology in an LMBA are set as peaking amplifiers with different thresholds when cooperating with the control amplifier (CA) as the carrier, forming a hybrid load modulation behavior between Doherty and ALMBA. Compared to standard LMBA, the proposed H-ALMBA has a three-way load modulation with CA, BA1 and BA2 through proper amplitude control and phase alignment. Thus, this new mode offers extended power back-off range and enhanced back-off efficiency without suffering from difficulty and complexity in wideband design as imposed on three-way Doherty PAs. Based on comprehensive theoretical derivation and analysis, the proposed H-ALMBA is designed and implemented using commercial GaN transistors and wideband quadrature couplers. Moreover, the continuous-mode matching is applied to the carrier amplifier achieving a maximized wideband efficiency at power back-off. This is the first time that continuous mode and ALMBA have been used in combination, and very satisfactory results have been achieved, exhibiting the highest 10-dB OBO drain efficiency (DE) ever reported for wideband load-modulation PAs. The developed prototype experimentally demonstrates wide bandwidth from <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$1.7 - 3.0$ </tex-math></inline-formula> GHz. The measurement exhibits an efficiency of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$63 - 81\%$ </tex-math></inline-formula> at peak output power, <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$51 - 62\%$ </tex-math></inline-formula> for 5-dB OBO, and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$50 - 66\%$ </tex-math></inline-formula> for 10-dB OBO within the design bandwidth. When stimulated by a 20-MHz long term evolution (LTE) signal with 10.5-dB peak to average power ratio (PAPR), a <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$50 - 55\%$ </tex-math></inline-formula> average efficiency is measured over the entire bandwidth at an average output power around 32 dBm.

Novel Passive Vector-Sum Reconfigurable Filtering Phase Shifter With Continuous Phase-Control and Tunable Center Frequency

In this article, a novel reconfigurable filtering vector-sum phase shifter (RFPS) with a continuous phase shift range of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\ge 300^{\circ }$ </tex-math></inline-formula> and tunable operating frequency range from 1.05 to 1.3 GHz is proposed. It consists of two identical wideband Wilkinson power dividers (or power combiners) (WPDs) and a reconfigurable filtering quadrature coupler (RFQC) that is connected between the two WPDs. Through the first WPD, the split waves are fed into the RFQC and are then combined at the output ports of the RFQC. The phase of the combined waves can be continuously tuned by adjusting different combinations of coupling types between interstage resonators of the RFQC, and the resulted output waves are then summed up through the second WPD with the desired output phase. Different from the conventional active vector-sum phase shifter, the vector summing is realized by the proposed RFQC and is a pure passive design, resulting in a low-cost, low-noise, easy-design, and highly flexible system. A prototype is designed and fabricated to demonstrate the proposed technique. Detailed theoretical analysis and design procedure have been given. The experimental results show that the proposed RFPS features the continuous phase-control range of more than 300° with a tunable filtering response covering the frequency range from 1.05 to 1.3 GHz.

Design and analysis of noninverting single-spiral CMOS Wilkinson power dividers and their quadrature couplers and baluns

Design and analysis of noninverting single-spiral CMOS Wilkinson power dividers and their quadrature couplers and baluns

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.

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.

Reflection-Type Phase Shifter Integrated With Tunable Power Attenuation Mechanism for Sub-6 GHz Wireless Applications

An integrated configuration of the reflection-type phase shifter (RTPS) and attenuator with simultaneous phase and amplitude control is presented for a phased-array front-end beamforming. The phase shift function of the RTPS adopts a quadrature coupler with high/low pass lumped elements and the corresponding π-type C–L–C loads. An RF tuner is subsequently incorporated into the 90° coupler to provide an energy reduction path and applied at the intermediate inductor of the coupler, thereby enabling a tunable transmission power. The merged coupler/RF-tuner realizes a matched and symmetrical structure with less impact on the load impedance variation, which can be regarded as part of the RTPS that performs RF signal degradation and maintains phase shift tuning. Furthermore, the π-type attenuator is incorporated into the RTPS to obtain an adequate power control range for the side-lobe suppression of the beamforming network. The simulated and measured results demonstrate the feasibility and suitability of the network for the proposed merged configuration applied to the phased-array system.

Compact wideband and harmonic suppressed quadrature coupler using susceptance loaded coupled lines

AbstractIn the paper, a novel type of quadrature coupler with the features of wideband, arbitrary harmonic suppression and small size is proposed, for the first time, by employing susceptance loaded coupled lines. Design equations are derived using the even‐odd mode decomposition analysis. The discussions on arbitrary couplings and harmonic suppressions are also investigated. For demonstration, a prototype with a second harmonic suppression was fabricated and measured. The overall size is 0.19λg × 0.27λg, which is smaller than most of the reported wideband quadrature couplers. Measurement results show that the fractional bandwidth of 40% is obtained under the condition of 15‐dB return loss/isolation, 1‐dB amplitude imbalance, and 90° ± 5° phase difference. The proposed coupler can be a good candidate for wideband applications without using the multi‐cascading and complex miniaturization method.

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.

Slotline‐based frequency‐reconfigurable quadrature coupler with wide tunable range and simple tuning mechanism

AbstractFrequency‐reconfigurable couplers presented before show some shortages such as limited tunable range and complex tuning mechanism. To address these problems, a frequency‐reconfigurable coupler with wide tuning range is proposed based on a slotline structure. A T‐shaped shorted feeding line with certain impedance transform is connected to each port of the coupler. Beneath the shorted end, the slotline structure is utilized to transfer the signal coupled from the feeding line. The 3‐dB quadrature coupler performance is achieved by setting different widths of the slotlines. To tune the frequency, a varactor with tuning capacitance is loaded at the center of each shorted feeding line. Equivalent circuit is given by transmission line model to verify the design concept. For demonstration, the coupler is fabricated and measured. Good agreements between the simulation and measurement and a wide frequency tunable range from 1.2 to 2.6 GHz are achieved based on a single tuning mechanism.

An Interstage-Reflectionless V-Band Radiometer With Capacitor-Reused Absorptive Matching in 0.13-μm SiGe BiCMOS

A <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${V}$ </tex-math></inline-formula> -band heterodyne radiometer in SiGe BiCMOS employing a capacitor-reused absorptive inter-stage matching network is firstly proposed, which prevents from employing a circulator, a resistive attenuator or two quadrature couplers in the conventional high-sensitivity cascaded receiver. This radiometer consists of a five-stage low noise amplifier (LNA) with the proposed reflectionless output matching network (RLMN), and a double-balanced Gilbert mixer stage with integrated Marchand baluns. In the RLMN, the capacitor for in-band matching is reused as an impedance inverter in the lossy absorptive network to eliminate reflections. Utilizing the reflectionless LNA, the radiometer eliminates the out-of-band reflected signals round the interfaces of LNA and mixer. Fabricated in a <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$0.13~\mu \text{m}$ </tex-math></inline-formula> SiGe BiCMOS technology, the reflectionless LNA achieves a gain of 31.9 dB@56 GHz, an absolutely stable operation in-band and 11 times larger stability factor out-of-band than conventional LNAs. Moreover, the implemented heterodyne radiometer achieves a noise equivalent temperature difference (NETD) of 0.3 K which is even comparable with wideband direct-detection radiometers.

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.

Wideband circularly polarized antenna with metallic walls for L-band applications

PurposeTo achieve right-hand circular polarization (RHCP), a 3-dB Wilkinson power divider with a λ/4 phase shifter is used. The crossed-dipoles are placed at almost λ/4 elevation on the ground plane and connected to two coaxial cables. Experiments show that the impedance bandwidth of 49.40% (913.7–1,513.1 MHz) and axial ratio bandwidth (ARBW) of 22.88% (1,145.8–1,441.8 MHz) are achieved.Design/methodology/approachIn this study, a wideband crossed-dipole antenna with circularly polarized (CP) radiation for L-band satellite and radar applications is presented. The proposed CP antenna comprises two orthogonally placed printed dipoles, a quadrature coupler and a box-shaped ground plane.FindingsFurthermore, by fixing the box-shaped ground plane under the radiators, 5.13 dBic RHCP peak gain at 1,300 MHz and maximum half-power beamwidth (HPBW) of 84.5° at 1,170 MHz are realized for the antenna.Originality/valueEight metallic walls are connected to four corners of the substrate to stabilize the radiation properties in this study. Results show that the ARBW and front-to-back ratio are improved and the maximum HPBW around 127° across the operating frequency band is achieved. The proposed CP antenna is a good candidate for Global Positioning System (GPS) L2 (1.227 GHz), GPS L5 (1.176 GHz) and air route surveillance radar system at 1,215–1,390 MHz frequency band.

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.