Hybrid Coupler Research Articles

A New Diminutive Octa Polarization Reconfigurable Circular Patch Antenna

This proposes a new diminutive octa polarization reconfigurable circular patch antenna design. This new antenna can operate in eight different polarizing states (6 different angles of linear polarization and 2 circular polarization states) with the help of a reconfigurable probe feed network. The antenna comprises of a circular layer of radiation with four equally spaced slits at the boundary of the circular patch to obtain size reduction. The bias voltages of six pairs of PIN diodes are interval between each state. A 3 dB hybrid coupler and a RF switch are used to produce reconfiguration between circular polarization states of the right and left hand. The proposed antenna was designed using CST microwave studio, fabricated as a prototype model and tested which produces desired values for various parameters of antenna including compact size. The designed antenna operates within 2.4-2.5 GHz frequencies suitable for wireless applications.

Four‐hundred gigahertz broadband multi‐branch waveguide coupler

Terahertz technology is a hotspot in the current academic research. In this study, a 400 GHz broadband multi-branch waveguide hybrid coupler is designed, but it is very difficult to fabricate. In order to release the processing difficulty, a modified five-branch hybrid coupler has also been designed, fabricated and measured. The hybrid coupler consists of five modified branches and has been optimised to a great performance, which increases the operation bandwidth. Compared to the traditional five-branch hybrid coupler design, this structure has a wider operation bandwidth and the bandwidth is almost the same as traditional seven-branch hybrid coupler. Based on this model, the performance of the coupler is optimised by HFSS software. The measurement results show good performance that >18 dB return loss (S11) and isolation (S23), 90° ± 2° phase difference and 0.3 dB amplitude imbalance are obtained in the frequency range of 380–460 GHz, agreeing well with the simulation results.

Quad‐mode radial uniform circular array antenna for OAM multiplexing

This study presents a novel radial uniform circular array (UCA) antenna for quad-mode orbital angular momentum (OAM) multiplexing in the 5.2 GHz band. The antenna can simultaneously generate four OAM modes (±1, ±2) using two radial UCAs printed concentrically on a single substrate. Each UCA is connected to an individual dual-mode feeding network, and generates a pair of complementary OAM modes. The feeding network for each UCA consists of one quadrature hybrid coupler and two circular feedlines, and they can be integrated onto a single substrate. The measured radiation patterns and helical phase wavefronts show the successful generation of four OAM modes by the proposed antenna. The quad-mode OAM transmission test was performed using two prototypes of the proposed antenna, and good isolations >13.7 dB were obtained between four OAM mode channels, which demonstrates that the antenna can be successfully used for OAM multiplexing.

Single-Ended-to-Balanced Power Divider With Extended Common-Mode Suppression and Its Application to Differential $2\times4$ Butler Matrices

A new type of wideband single-ended-to-balanced (SETB) power divider (PD) is presented. The design achieves high level and extended frequency range of common-mode (CM) suppression. Slotline-to-microstrip transitions are essential parts of the design, for the CM signals will be terminated in the slotline and thus will be rejected. Slotline resonators are used to provide multiple resonances which form a constant passband. The design is verified via experiments and excellent performance is obtained, including 27 dB of CM rejection and 25 dB of mode-conversion suppression levels with 200% fractional bandwidth (0– $2f_{o}$ ). Based on this property, a differential $2\times4$ Butler matrix (BM) is presented using two SETB PDs and a 90° hybrid coupler. A differentially fed array, which is composed of four wideband linear-polarized elements and fed by the proposed differential BM, achieves a very low cross-polarization level due to the excellent CM suppression from the BM.

Analog 28 GHz LoS MIMO Relay System Using a 90° Hybrid Coupler

To enlarge the range of wireless fronthaul and backhaul communication links operating close to the millimeter-wave region, this letter presents a novel line-of-sight (LoS) multiple-input–multiple-output (MIMO) relay system. The analog relay system consists of a simple 90° hybrid coupler to separate two uncorrelated transmit data streams realizing a low complex and cheap system. The functional capability is proven within measurements of two independent 2 × 2 LoS MIMO links at 28 GHz connected by the relay system. A high decoupling of the two independent transmitted data streams of more than 27 dB after the 90° hybrid coupler and a high modulation error rate at the last receiver of around 22 dB could be reached for quadrature phase shift keying (QPSK) and 16-quadrature amplitude modulation (QAM) modulated signals.

Differential-Mode to Common-Mode Conversion Detector Based on Rat-Race Hybrid Couplers: Analysis and Application to Differential Sensors and Comparators

A microwave device able to detect differential-mode to common-mode conversion (or vice versa) in a four-port balanced circuit is proposed. For mode conversion detection, the balanced circuit should be fed by a differential-mode signal, generated by means of a rat-race balun from a single-ended signal. By connecting the pair of output ports of the balanced circuit under test to one of the two pairs of isolated ports of a second rat-race coupler, conversion to the common-mode (if it exists) can be detected and recorded in the $\Sigma $ -port. Since the signal level at the output (single-ended) port depends on mode conversion efficiency, the complete two-port structure, including the pair of rat-race couplers plus the balanced circuit in between, can be used as a comparator or differential microwave sensor based on mode conversion. In such a sensor, the working principle is symmetry disruption (caused, e.g., by an asymmetric dielectric load), and the output variable is the transmission coefficient, related to the level of asymmetry. A detailed analysis, considering an arbitrary unbalanced four-port test structure (to account for symmetry disruption), is carried out. Then, such analysis is particularized to the case of a pair of unbalanced and uncoupled matched lines, and the conditions for sensitivity optimization are obtained. Finally, a differential sensor and comparator based on a pair of balanced (and meandered) matched lines, designed according to the guidelines for sensitivity optimization, is fabricated and validated.

Radio Frequency Energy Harvesting System Making Use of 180° Hybrid Couplers and Multiple Antennas to Improve the DC Output Voltage

This paper introduces the implementation and experimental results obtained with a radio frequency energy harvester system. A radio frequency combining power circuit based on the characteristic of the 180o hybrid coupler to combine energy is proposed here to be used in radio frequency energy harvesting schemes. Through experimental validations, this proposal demonstrates to offer important advantages compared with other radio frequency energy harvesters found in the literature, including a harvesting voltage enhanced, ease implementation, since is not require any modification in the hybrid coupler,and multi-band function using wideband antennas. The system is designed to harvest energy in the GSM, UMTS, and Wi-Fi frequency bands. The validation of the proposed system using four receiving antennas showed a direct current harvested voltage of 301 mV at 2.5 GHz for an input power of -7 dBm. In addition,the terms of accumulated voltage gain and cumulative efficiency are introduced to evaluate the performance of the proposed combining circuit in radio frequency harvesting schemes.

A planar ultra‐wide band asymmetric rat‐race hybrid coupler

In this article, an asymmetric ultra-wideband rat-race hybrid coupler with 180° phase shift is proposed. The primary goal of this work is to design a planar ultra-wideband hybrid coupler with a microstrip structure by avoiding via holes and multi-layer design. The bandwidth of an asymmetric ring hybrid is enhanced using shorted coupled lines, perturbation impedance techniques, and matching stubs. This hybrid coupler was designed and fabricated using Taconic TLX-8 substrate with a thickness of 0.5 mm. The results of the simulation and measurement are promising and meet the desired specifications. This hybrid coupler yields a fractional bandwidth of 56% at the center frequency of 5.95 GHz based on ±1 amplitude imbalance between two output ports.

Compact Antenna for Picosatellites Using a Meandered Folded-Shorted Patch Array

The design and operation of a compact antenna array offering circularly polarized (CP) radiation for picosat and other small satellites for communication applications is presented. The proposed array combines the folded-shorted patches (FSPs) and meandering for antenna miniaturization. Realization of CP is achieved by a compact and planar feed circuit consisting of a network of meander-shaped 90° and 180° hybrid couplers, which can provide quadrature feeding of the FSP elements and can be integrated onto the backside of the antenna ground plane, which is only 5 × 5 cm2. Agreement in terms of the simulations and measurements is observed with realized gain values of more than 3 dBic at 1.065 GHz and with an antenna size of 0.17 λ 0 × 0.17 λ 0.

GHz Low-Loss Acoustic RF Couplers in Lithium Niobate Thin Film.

We present the first group of GHz low-loss acoustic radio frequency (RF) couplers using the fundamental symmetric (S0) mode in X-cut lithium niobate thin films. The demonstrated multistrip couplers (MSCs) significantly surpass the insertion loss (IL) and the operating frequency of the previous works in more compact structures, thanks to the large electromechanical coupling and low loss of S0 in lithium niobate. The design space of S0 MSCs is first explored. Devices with different coupling factors are fabricated using different numbers of strips. Based on the S0 testbed with an IL of 4.5 dB at 1 GHz, the hybrid coupler shows an IL of 7.5 dB, while the track changer shows an IL of 5.1 dB, over a 3-dB fractional bandwidth of 8%. Couplers at different frequencies (between 0.75 and 1.55 GHz) are also investigated. Upon further optimizations, the S0 MSC platform can potentially enable low-loss wideband signal processing functions toward an RF acoustic component kit.

Millimeter-Wave Printed-RGW Hybrid Coupler With Symmetrical Square Feed

In this letter, a new hybrid coupler with symmetrical square feed using printed ridge gap waveguide (RGW) technology is introduced and investigated. This structure can find important applications in beamforming network designs. The proposed coupler has a compact size of $1.12\lambda _{g} \times 1.12\lambda _{g} \times 0.14\lambda _{g}$ and shows promising results at millimeter-wave Ka -band around 30 GHz, especially in terms of amplitude balance bandwidth and loss. The simulated results are compared with the measured data and a good agreement is achieved.

Polarization-Insensitive Rectenna Arrays With Different Power Combining Strategies

This letter presents two 2 × 2 polarization-insensitive dual-polarized rectenna arrays with different power combining strategies for wireless power transmission applications. With a dual-polarized antenna array, the incident wave can be received and decomposed into the horizontally and vertically polarized components, which are equally redistributed by a hybrid coupler. By this means, the efficiency of the rectenna, in which the power is equally input to the two rectifiers in parallel, is independent of the incident wave's polarization. Based on the equal power routing mechanism, two rectenna arrays using the RF and dc combining strategies are designed and analyzed. Measurement results show that both rectenna arrays are insensitive to the incident wave's polarization, and have their own advantages and disadvantages.

Performance Aspects of Multiband Microwave Planar Devices for Wireless Applications

The RF front end receiver plays a key role to fulfill the demands of the numerous applications in the wireless communication .This article of lettering portrays about the analysis of planar microstriplines based multiband passive microwave devices which are simulated in ADS (Advanced Design System) software. Also we have designed a multiband band pass filter, and multiband hybrid coupler which are essential in the front ends design of receivers such as software defined radio and cognitive radio. Here BPF covers the frequency range from 400 MHz-2GHz and hybrid coupler covers from 1-5GHz. With the use of these components the single band RF front end will become the multiband front end receiver architecture.

Suspended plate antenna with circular polarization and configurable sense of rotation

Introduction: Circular polarization antennas (CPA) are able to reduce the “Faraday rotation” effect due to the ionosphere, which causes a significant power losses compared to the case of using linear polarization antennas (LPA) [1]-[2]. Therefore, these antennas are widely used for space telemetry applications of satellites, space probes and ballistic missiles among others [2]. Furthermore, suspended plate antennas (SPA) offer the possibility to obtain largest levels of maximum gain and impedance bandwidth compared to those obtained with conventional technologies. Likewise, it is useful to be able to select the most appropriate sense of rotation, depending on the propagation conditions in the up/down links. Objective: To design a CPA with configurable sense of rotation for small satellite applications, using SPA technology, such that it has gain and bandwidth levels higher than those obtained with conventional technologies.
 Method: The antenna design is based on models proposed in the literature, through which an initial geometry consisting of a suspended patch with an L-shaped feeder and a hybrid coupler is designed. Subsequently, geometry optimization by parametric analysis is carried out with appropriate electromagnetic simulators. 
 Results: The proposed design has an impedance bandwidth of 34.39% and a maximum gain of 8.75 dBi at a frequency of 2.35GHz.
 Conclusions: The L-shaped feeder technique for suspended patches improves the behavior of the antenna in axial ratio, impedance and maximal gain.

Dual-polarized, monostatic antenna array with improved Tx–Rx isolation for 2.4 GHz in-band full duplex applications

AbstractThis paper presents a two-elements based, dual polarized, single layer, patch antenna array with improved isolation between transmit (Tx) and receive (Rx) ports for 2.4 GHz in-band full duplex (IBFD) or simultaneous transmit and receive wireless applications. The differential feeding deployed at the Rx port effectively suppresses the coupling which is termed as self-interference from the Tx port to achieve high Tx–Rx interport isolation. A simple 3 dB/180° ring hybrid coupler with nice amplitude and phase balance characteristics has been used for differential Rx operation. The mathematical description for a differential feeding based self-interference cancellation mechanism is also presented for the proposed dual polarized IBFD antenna array. The measurement results for the implemented prototype of the antenna array demonstrate very nice levels of Tx–Rx interport isolation. The implemented single layer, compact antenna array presents 10 dB return-loss bandwidth of more than 50 MHz for both Tx and Rx ports. The prototype achieves >80 dB peak interport isolation and 75 dB (65 dB) isolation in 20 MHz (50 MHz) bandwidth.

Linear-Polarization-Insensitive Rectenna Design for Ground-to-Air Microwave Power Transmission

This paper presents a linear-polarization-insensitive rectenna for the ground-to-air microwave power transmission (MPT). With an integration of a hybrid coupler and a dual-linearly-polarized (DLP) antenna, a linearly-polarized (LP) incident wave can be decomposed by the antenna polarization tilts into the horizontally-polarized (HP) and the vertically-polarized (VP) components, correspondingly, which are then distributed evenly through the hybrid coupler as the inputs of two successive lumped rectifiers. Thus, RF-to-dc power conversion efficiencies (PCEs) of the presented DLP rectenna maintain insensitive to its incident LP polarization tilts. An aperture-coupled feeding mechanism and lumped matching networks are employed to enable the compact DLP rectenna design for practicality. Both theoretical analysis and experimental results validate that the RF-to-dc PCEs of the DLP rectenna keeps stable high regardless of its LP polarization tilts, which demonstrates a prospect for the ground-to-air MPT applications.

Mechanically Reconfigurable Linear Phased Array Antenna Based on Single-Block Waveguide Reflective Phase Shifters With Tuning Screws

This work presents the design and prototyping of a reconfigurable phased array in Ku band (16 to 18 GHz) implemented in waveguide technology. The design is based on the use of a novel seamless waveguide module integrating four reconfigurable phase shifters to adjust the relative phase shift between the unitary elements of a linear array, which are illuminated uniformly by a corporate waveguide feeding network. The phase shifters are implemented by a 90° hybrid coupler in waveguide technology where two of its ports are loaded with a tunable reactive load, implemented in this proof of concept with a tuning screw. The four phase shifters have been manufactured in a single part using direct metal laser sintering, avoiding the losses related to bad electric contacts and misalignments associated to multipart devices. This also simplifies the assembly of the full phased array, leading to a modular approach with three parts whose design can be addressed separately. The experimental results for the complete array antenna show great performance and demonstrate that the main-lobe of the radiation pattern can be effectively scanned continuously between the angles -25° and 25°, with a high efficiency in the whole design band thanks to the proposed waveguide implementation.

Compact Metamaterial Based $4\times4$ Butler Matrix With Improved Bandwidth for 5G Applications

This paper proposes a novel compact 4 × 4 butler matrix (BM) with improved bandwidth based on open-circuit coupled-lines and interdigital capacitor unit-cell to develop composite right/left handed (CRLH) transmission-line (TL) metamaterial structure. The BM is implemented by the combination of compact 3dB quadrature hybrid couplers, 0dB crossover and 45° phase shifter on a single FR4 substrate (er = 4.3 and h = 1.66 mm). The simulated and measured result shows that the return loss and isolation loss are better than 14 dB at all the ports, good insertion loss of -7 ± 2dB, which cover the frequency range of 3.2 GHz to 3.75 GHz. The phase difference of -45°, 135°, -135° and +45° are achieved with a maximum average phase tolerance of 5°. The overall dimension of the BM is 70mm × 73.7mm, which shows the compactness of the proposed design that is 75% size reduction and 8.2 times improvement in the bandwidth (550MHz) as compared to conventional BM. The CST microwave studio is used to design and perform the simulations. Additionally, the simulated and measured scattering parameters and phase differences show that they are in good agreement. This compact and improved bandwidth of the proposed BM is suitable for 5G antenna array beamforming network.

Two-Tone Excited Hybrid-Coupler-Based Intermodulation Generator for High-Isolation Wireless Sensing Applications

An intermodulation generator is designed and presented with integration of a hybrid coupler and two identical Schottky diodes (i.e., D1 and D2). The connection polarities of D1 and D2 to the direct and coupled ports of hybrid coupler are opposite for its rapid realization of balanced intermodulation generation. Due to the superior coupling characteristics of hybrid coupler, it can distribute an incident two-tone signal to the direct and coupled ports evenly for D1 and D2, and deliver the balanced intermodulation generations to the isolation port highly insulated from its incident port. Two identical quarter-wavelength shorted stubs at the fundamental frequency are implemented by suppressing the second-order spectrums for an enhancement of the balanced intermodulation generations. Both theoretical analysis and experiments validate the presented intermodulation generator design, which can highly isolate its incidences (the two tones) and outputs (the intermodulation generations) for the future high-isolation wireless sensing applications.

Simplified implementation of millimetre‐wave zero‐bias detector for an accurate detection in six‐port‐based receivers

In this Letter, a simplified design approach for zero-bias power detectors suited for integration in six-port receiver architectures is presented. The proposed concept uses the quadrature hybrid coupler as an effective way to improve the input impedance matching and linearity performance. The proposed solution has been experimentally validated through its implementation into a 60 GHz six-port receiver prototype to investigate its performance in detecting various M-ary quadrature amplitude modulation (M-QAM) signals. The obtained measurement results show a high accurate and linear detection responses for all investigated M-ary QAM modulation techniques (4-QAM, 16-QAM, 32-QAM). The variation in the error rates of the demodulated signals at the adjacent differential outputs is minimal (<1%), and the maximum error rate achieved does not exceed 5%. The obtained precision and linearity performances make the proposed structure highly suitable for the emerging millimetre-wave six-port receiver front-ends.