Hybrid Coupler Research Articles

Hybrid-pair ratio adjustable power splitters for add-on RF shimming and array-compressed parallel transmission.

A ratio adjustable power splitter (RAPS) circuit was recently proposed for add-on RF shimming and array-compressed parallel transmission. Here we propose a new RAPS circuit design based on off-the-shelf components for improved performance and manufacturability. The original RAPS used a pair of home-built Wilkinson splitter and hybrid coupler connected by a pair of connectorized coaxial cables. Here we propose a new hybrid-pair RAPS (or HP-RAPS) circuit that replaces the home-built circuits with two commercially available hybrid couplers and replaces connectorized cables with interchangeable microstrip lines. We derive the relation between the desired splitting ratio and the required phase shifts for HP-RAPS and investigate how to generate arbitrary splitting ratios using paired meandering and straight lines. Several HP-RAPSs with different splitting ratios were fabricated and tested on the workbench and MRI experiments. The splitting ratio of an HP-RAPS circuit has a tan or cot dependence on the meandering line's additional length compared to the straight line. The fabricated HP-RAPSs exhibit accurate splitting ratios as expected (<4% deviations) and generate transmit fields that well agree with predicted fields. They also demonstrated a low insertion loss of 0.33 dB, high output isolation of -26 dB, and acceptable impedance matching of -16 dB. A novel HP-RAPS circuit was developed and implemented. It is easy-to-fabricate/reproduce with minimal expertise. It also preserves the features of the original RAPS circuit (ratio-adjustable, small footprint, etc.) with lower insertion loss.

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.

A review of hybrid couplers: State‐of‐the‐art, applications, design issues and challenges

AbstractIn recent years, the hybrid branch‐line coupler has attracted much attention due to its appealing features such as of low cost and ease in fabrication for wireless communications. The fifth‐generation cellular networks promise to support several wireless technologies by capitalizing a multitude of frequencies and increase data rates. To achieve that, the butler matrix technique can be used to enhance both bandwidth and data rate with the implementation of beamforming. Conventional hybrid couplers are the main component to build a butler matrix, but they are generally bulky in size and narrow in bandwidth. Moreover, requirements imposed by newer wireless technologies makes the efforts in improving size compactness and bandwidth even more challenging. On the other hand, several techniques have been proposed in literature to solve both issues. This study focuses on the design challenges and issues of hybrid coupler designs and technologies, besides underlining their promising potential. In this context, several techniques for hybrid coupler to achieve the required bandwidth and size reduction are highlighted, such as the T‐shape, meander line, two sections, three‐section, and parallel couple lines.

A SIMPLE POWER – BASED DIRECTION OF ARRIVAL SENSOR

In this paper, a simple power - based Direction of Arrival (DoA) sensor is investigated. This sensor is applied in direction finding systems working at 2.6 GHz. The proposed sensor can determine the DoA via a simple formula compared to the algorithms – based methods. The sensor structure consists of simple components: two receiving antennas and a power dividers which have a good isolation between output ports based on hybrid couplers (HCs). With the range of simulation DoA from 0o to 35o, the proposed sensor yields the error of less than 5o.

Analysis and Performance Assessment of a Real-Time Correction Pseudo-Correlation Microwave Radiometer for Medical Applications

A new configuration of a pseudo-correlation type radiometer is proposed for a microwave biomedical application, such as diabetic foot neuropathy. The new approach as well as its simulated performance are thoroughly assessed using commercial off-the-shelf components and custom designed subsystems. We configured a pseudo-correlation receiver, centred at 3.5 GHz, to validate the proposal, comparing its simulated response with a measured alternative based on a 90∘ hybrid coupler pseudo-correlation prototype. We custom designed a balanced Wilkinson power divider and a 180∘ hybrid coupler to fulfil the receiver’s requirements. The proposed configuration demonstrated an improved noise temperature response. The main advantage is to enable the recalibration of the receiver through simultaneous measurable output signals, proportional to each input signal, as well as the correlated response between them.

Circularly polarized antenna array based on hybrid couplers for 5G devices

This paper depicts a wideband circularly polarized (CP) antenna for 5G devices. The antenna array has a 3D structure including four simple printed dipole elements with directional radiations, high gain, and high efficiency. It achieves a CP by using the sequential rotation (SR) feeding based on 90°-3dB hybrid couplers in the proposed feeding network. The antenna array bandwidth is wide, 26.7%, with an operating frequency band from 3.35 GHz to 4.35 GHz. The antenna achieves a high peak gain of 10.73 dBi and high efficiency of 93.75%. Besides, the antenna gain is stable over the operating bandwidth (BW). At the centre operating frequency of 3.75 GHz, the angle of circular polarization is 51°. The antenna is designed and fabricated on the Rogers 4003 C substrate. The measured S11 is well matching with the simulation results. With the above characteristics, the proposed antenna can be a suitable candidate for 5G devices.

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.

Miniaturized microstrip patch antenna with high inter‐port isolation for full duplex communication system

In this paper, an antenna is presented for in-band full duplex technology. This antenna includes a microstrip patch and a new 180° hybrid coupler. The designed 180° hybrid coupler has new structure that miniaturizes the entire system and also eliminates the self-interference signal that leaks from transmitter to receiver. In this antenna, at 2.4 GHz, an isolation between transmit and receive ports is more than 79 dB. Additionally, in this antenna, the measured inter-port isolation is better than 68, 72, and 74 dB for 80, 50, and 20 MHz bandwidths respectively in 10 dB return loss impedance. The dimensions of the designed antenna are 68 mm × 60 mm, and in compare with similar designed antenna is considerably smaller (more than 60%) with acceptable isolation.

Reconfigurable diplexer using hybrid couplers and perturbed TE012 cavities

AbstractA continuously tunable Ku-band waveguide diplexer is proposed in this paper. This diplexer is based on a hybrid coupler topology and is composed of an input filter centered at 11.9 GHz with a 200 MHz bandwidth, a pair of ladder-type hybrid couplers, and a pair of tunable filters. This diplexer can provide two bandpass channels (channels 1 and 2) that can continuously go from a state where the bandwidths of channels 1 and 2 are maximum (up to 140 MHz) and minimum (down to 40 MHz), respectively, to another configuration where the bandwidth of channel 1 is the largest and the bandwidth of channel 2 is the narrowest. We propose a tunable filter based on TE012 mode circular cavities that are perturbed by low-loss dielectric inserts to obtain such performance. The resonant frequency of these cavities can be continuously tuned between 11.8 and 12 GHz due to the linear movement of the dielectric perturber. The design process for these components is presented and a breadboard device has been manufactured and measured to prove the concept. Different measured configurations of the diplexer are demonstrated, showing that the 200 MHz operating bandpass between 11.8 and 12 GHz can be efficiently separated into two tunable channels. The measured bandwidth of channels 1 and 2 in the manufactured diplexer can be tuned from 135 to 40 MHz (and vice versa) while maintaining an average guard band between the channels of approximately 26 ± 7 MHz. The obtained bandwidth tuning ratios are 3.2 for the highest channel and 3.1 for the lowest channel.

Design and analysis of 3D-printed hybrid couplers for D-band applications

AbstractThis work focuses on the impact of the build orientation on additively manufactured waveguide-based hybrid couplers for D-band frequency range and relates it to other sources of uncertainty within the overall manufacturing process and measurement instrumentation for the D-band frequency range. The designed specimens are first printed from UV curable photopolymer resin and subsequently metal coated by an electroless silver plating process, which in turn is improved by making use of the slotted waveguide approach. Although the requirements toward geometrical precision to achieve phase errors below 10° are in an order of 0.1 mm, a desktop grade DLP printer is utilized in this work in order to point out the prospects and limitations of additive manufacturing. Furthermore, waveguide paths with bends are part of the model and their impact on the measured attenuation is estimated explicitly.Despite this narrow field of tolerances, one specimen could have been realized, which achieves a measured output magnitude imbalance of 0.7 dB over the frequency range from 120 to 155 GHz while at the same time exhibiting a phase deviation of only &lt;10° from the desired 90°. With these demonstrated results, the proposed approach provides suitability for future applications in the D-band frequency range.

Waveguide Hybrid Septum Coupler

The design of a patented broadwall waveguide hybrid coupler, derived from the working principle of a septum polarizer, is presented. This E-plane coupler requires a single and large aperture in the common broadwall of the two parallel waveguide transmission lines to function, facilitating its manufacturing and assembly. The working principle of this hybrid coupler is detailed, supported by equations making a link with the well-known 3-dB tandem coupler and enabling the definition of a good starting point for optimization purposes. The concept is further validated through the design, manufacture, and test of a prototype working over the frequency range 17.3-20.2 GHz. Good results are obtained over a fractional bandwidth of 19.4% (17.2-20.9 GHz) with axial ratio and return loss (RL) better than 0.5 and 24 dB, respectively. This operating range may be extended up to about 27% (16.8-22.0 GHz) for less demanding applications (axial ratio below 3 dB and RL better than 20 dB). This is a promising solution for the design of advanced feed systems and beamforming networks part of communication satellite payloads.

전자전용 S&amp;C 대역 GaN 반도체 고출력증폭기 설계 및 제작

This paper describes the design and measurement results of an S to C-band gallium-nitride (GaN) solid-state power amplifier (SSPA) for an electronic warfare jammer. The S to C-Band GaN SSPA is fabricated, without wideband isolator, with multiple combined of 80 W GaN module using wide-band impedance matching topology and Super CMC (S-CMC) carrier structure, and designed small-sized broadband matching circuit using a cascaded 90° hybrid coupler for improve impedance mismatching performance between GaN DRA and GaN HPA. The S to C-band GaN SSPA for the electronic warfare, with a continuous wave (CW) RF injection condition over a frequency range of 2 to 6.5 GHz, demonstrated performance with a saturated average output power of 225 W (330 W peak output power), 21.39 % power added efficiency (PAE). Furthermore, with 1 % duty &amp; 10 µs PW Pulse RF injection condition over an operation frequency range, it had performance with a saturated average output power of 287 W (404 W peak output power).

Elliptically Bended Coupler with Arbitrary Power Division

In this paper, we propose a 1.8 GHz microwave coupler with arbitrary power division. It consists of a wideband unequal power division hybrid coupler with higher-order harmonic filtering that covers all GSM (0.8 GHz – 1.9 GHz) and WiFi (2.4 GHz) bands. The architecture consists of a 4 port unequal power division, which is usually of the 0° and 180° coupler types.

Wideband High-CMRR Fully Differential Couplers Using Multimode Star-Junction

This article presents novel wideband fully differential hybrid and rat-race couplers whose design methodologies are based on the multimode star junction. The couplers benefit from the even and odd modes of the slotted-microstrip sections that constitute the junction to realize compact equivalent transmission lines, while they exploit the characteristics of the slotline to achieve differential ports with wideband performance and high common mode rejection ratio (CMRR). The differential signals are extracted through slotline to coupled-microstrip line transitions that maintain the phase relation between the ports. Measurements, which are in good agreement with electromagnetic (EM) and circuit simulations, confirm the theoretical predictions. The proposed hybrid coupler has 12% and 33.3% 15-dB return loss (RL)/isolation and 3-dB fractional bandwidths (FBWs), respectively, $0.6\lambda _{g} \times 0.6\lambda _{g}$ size, and 0.6-dB insertion loss (IL). While the proposed rat-race coupler has 32.5% and 35% 15-dB RL/isolation and 3-dB FBWs, respectively, $0.7\lambda _{g} \times 0.7\lambda _{g}$ size, and 0.6-dB IL. For both structures, the CMRR exceeds 50 dB at the operating frequency and the CM rejection FBW exceeds 300%.

The Influence of changes in the dielectric constant on Return loss, Vswr, Isolation and Phase Difference Microstrip Hybrid Coupler For Coastal Radar Applications

This study aims to determine the effect of changes in perubahan value changes in the Hybrid coupler on the return loss, insertion loss, coupling factor and the isolation value at the 3 GHz frequency which is applied to coastal radar. the type of antenna used is a microstrip patch antenna. The material used to design the antenna is FR4 with a substrate thickness of 1.6 mm and has a value of er r = 4.3. This study designed a microstrip branch line coupler with a T-Junction that works at a frequency of 3 GHz with both loss values ​​for (Tx) and (Rx), namely 3 dB and a phase difference of 90 °. The steps taken are after obtaining the length and width values ​​from the formula, then these values ​​are simulated after obtaining the correct value of 3 GHz, then an experiment is carried out with the dielectric constant values ​​of 4.1, 4.3 and 4.6.

Load-tolerant external matching unit based on a wideband hybrid coupler for the ICRH system of DTT

In the first phase of the Divertor Tokamak Test Facility (DTT), the goal of coupling a RF power of 3 MW to the plasma will be reached with a single ICRH module constituted by 4 generators, 2 or 4 External Matching Units (EMU) and 2 antennas. The operation with high levels of RF power into ELMy H-mode plasmas requires a robust and reliable Load-Tolerant EMU. Currently the most appropriate solution, ensuring a VSWR at the generators under the safety threshold of 1.5:1, will be based on a Wideband 2-section coaxial Hybrid Coupler operating in the frequency range of 60−90 MHz. HFSS and CST-MS simulation software was used for the optimization of the characteristic impedances and lengths of the transversal and longitudinal branches aimed to achieve excellent performance (amplitude and phase balance at the output ports, and low reflection at the input port) over the entire frequency range. The analysis has been carried out for Zo = 50 Ω and 30 Ω coaxial transmission lines in terms of S-parameters and electric field. Several good solutions with an amplitude imbalance about ±0.25 dB and a return loss lower than −20 dB in a large part of the frequency range will be presented. Then a simulation of the overall (end-to-end) EMU (Wideband Hybrid Coupler with shifter, stub and service stub in each of the 2 output branches) exploiting a suitable circuital solver of Ansys Electronics tool of HFSS, has been implemented. The resilience of the EMU has been tested determining the VSWR in input and the amplitude balance at the outputs for a typical resistive and reactive loading variation occurring during ELMs at f = 75 MHz and compared with the results at 65 MHz and 85 MHz.

Π-type reconfigurable coupler based on a complementary tunable method

A complementary tunable method is proposed based on the Hybrid coupler. The odd-even mode analysis shows that the method can achieve continuously tunable power division ratio by changing two transmission lines in the circuit, and it can achieve larger tunable range by improving the complementary tunable method based on the cascaded Hybrid coupler. Using the improved method, a novel π-type reconfigurable coupler, which works at 2.45 GHz, is designed by replacing transmission lines with π-type circuit. The power division ratio of the fabricated reconfigurable coupler is changed in the range of −20.5–21.3 dB, with the bias voltage being 0∼6 V; meanwhile, the isolation and return loss are above 20 dB.

3-D Printed Directional Couplers in Circular Waveguide

The design of an additively manufactured circular waveguide 3-dB hybrid directional coupler is proposed and demonstrated. Asymmetric corner radius perturbations at the in-plane orthogonal junction of the four waveguides along with curvilinear inductive posts designed to interact with the TE <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</sub> mode of the circular waveguide are used to facilitate directivity and isolation. Capacitive waveguide perturbations at each of the four ports provide impedance matching. The proposed design is engineered to operate within V-band from 57 to 64 GHz and provide both 10-dB isolation and return loss and a 90° phase difference between the direct and coupled ports. A commercially available stereolithography (SLA) printer is used to fabricate the hybrid coupler as well as the rectangular-to-circular tapered mode transducers and the thru, reflect, line (TRL) calibration components required for experiments. The printed couplers are metallized using an electroless silver plating process by a closed-loop bidirectional multiport pump-driven fluidic system. Results from the experiment and the simulation are provided.

Filter-Free Photonic Image-Rejection Down-Conversion for Distributed Antenna Applications

Photonics-assisted frequency conversion based on cascaded modulators is an effective way to satisfy the requirements of distributed antenna array applications. A filter-free photonic image-rejection down-converter with immunity to dispersion-induced power fading is proposed and demonstrated. The radio frequency (RF) signal from the distributed antenna unit is injected into a dual-drive Mach–Zehnder modulator (DDMZM) through an electrical 90° hybrid coupler (HC), and a single-sideband (SSB) signal is realized. It is then transmitted to the center office by an optical fiber link. At the center office, the modulated RF signal is injected into a dual-polarization dual-parallel MZM (DP-DPMZM) after a polarization controller (PC). Afterwards, an LO signal remodulates it through the Y-DPMZM, and carrier-suppressed SSB modulation is fulfilled via another electrical 90° HC. After the power splitting, quadrature I and Q IF signals can be obtained by a photonics-based continuously adjustable phase shifter. Through a combination of the I/Q IF signals with a low-frequency electrical 90° HC, a photonics image-rejection down-converter based on phase cancellation is realized. Moreover, no optical filter is required; thus, the image-rejection down-converter can work with a large bandwidth. The proposed filter-free photonic image-rejection down-converter is theoretically analyzed and experimentally verified.

Flexible millimeter‐wave Butler matrix based on the low‐loss substrate integrated suspended line patch hybrid coupler with arbitrary phase difference and coupling coefficient

In this paper, a millimeter-wave Butler matrix with flexible phase differences is proposed using the substrate integrated suspended line technology. To begin with, a low-loss substrate integrated suspended line (SISL) circular patch coupler consisting of four circular sectors is presented, achieving arbitrary phase difference and coupling coefficient by adjusting the angle and radii of the sectors. Based on the proposed coupler, two prototypes of the SISL Butler matrix are designed, fabricated and measured for the demonstration. In prototype I, the crossovers are removed and a flexible phase difference is obtained with an area size of 2.5 λg × 2.8 λg. In prototype II, both the crossovers and 45° phase shifters are removed and the phase differences of ±45° and ±135° are obtained with an area size of 1.86 λg × 2.24 λg. Low crosstalk between components and minimal radiation loss can be achieved by the SISL self-packaged characteristic and electromagnetic shielding. For both prototypes, the measured insertion losses are less than 2 dB at 26 GHz, including the loss of transitions and connectors, and the measured phase errors are less than ±10° within a bandwidth of more than 10%. The proposed Butler matrix shows the advantages of compact size, low loss and high integration.