Ring Coupler Research Articles

Dual-band devices based on coupled striplines for different power distribution in the frequency bands

The approach to the development of dual-band power distribution devices with different power division ratios in different frequency bands, based on the method of a dual-frequency equivalent replacement, is considered in the article. For its implementation, an equivalent four-terminal network based on a section of coupled microstrip transmission lines is proposed in addition to the T- and P-type circuits. Relations for calculating the electrical parameters of the circuit elements of these four-pole devices are obtained. The relations allow replacing the transmission line section with different values of the wave impedance in different frequency bands. The electrical length of such a section can vary and be different from p/2. Examples of modeling of non-equilateral power distribution devices with unequal branches such as two-channel balanced dividers and a ring divider (ring coupler) with power division coefficients of 2.0 and 1.0 in frequency bands with center frequencies of 2.0 and 3.6 GHz are given. Experimental measurement of characteristics of the designed models of the two devices showed good agreement between the experiment and the simulation results.

Performance Analysis of 180° HRR Coupler Used for Direction Finding with an Antenna Array

This paper presents the performance analysis of hybrid rat race coupler, widely used in radio frequency (RF)/wireless communication systems to couple the power in the desired way. The hybrid ring coupler consists of 4 ports, two for the input signals and two for the output signals, where sum and difference patterns of the applied two signals can be obtained at two output ports and usually called sum and difference ports. In this work, the couplers have been designed and simulated at central frequencies (fo) of 2.4 and 10 GHz using different types of substrates such as RT Duroid 5880 and FR4. Furthermore, the coupler has been used for direction finding (angle-of-arrival estimation) application, where we combine the designed hybrid rat race coupler with a simple two antenna elements array (at fo=10GHz and RT Duroid =2.2) and fabricate the circuit in order to validate the performance of the coupler by measuring the direction of arrival (DoA) from and ports. The obtained results show that good performance can be achieved with the designs considered in this paper.

A compact arbitrary power division coupler with nonstandard phase-difference

This paper presents a new coupler configuration which can be designed with both arbitrary power division and nonstandard phase difference at the output ports. The planar coupler ring is composed of four section microstrip lines and an open stub resulting in ease of fabrication. Its circuit parameters can be easily determined by the derived closed-form equations and the corresponding performance in terms of power division ratio, output phase difference, and the tunable parameters is mainly analyzed. Compared with the previous counterparts, its bandwidth and area have obvious superiority. For experimental verification, two prototypes, operating at 1 GHz, have been designed and implemented in microstrip process. One demonstrates a 45° phase difference with equal outputs and the other is designed for a 105° phase difference with 6.02 dB power division ratio. The design theory has been supported with good agreement between the simulated and measured responses.

Design of A Compact Single-Balanced Mixer for UWB Applications

The design and implementation aspects of a new single-balanced mixer for ultra-wideband (UWB) applications are presented in this study. The proposed mixer utilizes a miniaturized UWB ring coupler as a balun, consisting of a pair of in-phase and inverted-phase transitional structures. The well-balanced UWB performance of the ring coupler, aside from the optimized diode matching, results in improved conversion loss and inter-port isolations for a wide bandwidth. The size of the implemented single-balanced diode mixer is reduced to about 60% of the area of the conventional single-balanced ring diode mixer. The measured results of the proposed mixer exhibit an average conversion loss of 7.5 dB (minimum 6.7 dB) and a port-to-port isolation of greater than 18 dB over a UWB frequency range of 3.1–10.6 GHz. The measured results agree well with the simulated results.

Reduced Hybrid Ring Coupler Using Surface Micromachining Technology for 94-GHz MMIC Applications

In this study, we developed a reduced 94 GHz hybrid ring coupler on a GaAs substrate in order to demonstrate the possibility of the integration of various passive components and MMICs in the millimeter-wave range. To reduce the size of the hybrid ring coupler, we used multiple open stubs on the inside of the ring structure. The chip size of the reduced hybrid ring coupler with multiple open stubs was decreased by 62% compared with the area of the hybrid ring coupler without open stubs. Performance in terms of the loss, isolation, and phase difference characteristics exhibited no significant change after the use of the multiple open stubs on the inside of the ring structure. The reduced hybrid ring coupler showed excellent coupling loss of 3.87±0.33 dB and transmission loss of 3.77±0.72 dB in the measured frequency range of 90–100 GHz. The isolation and reflection were −48 dB and −32 dB at 94 GHz, respectively. The phase differences between two output ports were 180°±1° at 94 GHz.

A Nonstandard Phase-Difference Ring Coupler for Unequal Power Division

ABSTRACTA planar ring coupler with nonstandard phase difference and an unequal power division ratio is proposed in this article. The circuit topology of this coupler is similar to the traditional coupler, which consists of four arms in microstrip implementation. The design parameters of this coupler can be determined easily by closed-form equations. Based on standard microstrip technology, the interrelated constraint between phase difference and realizable power division ratio has been investigated. The fractional bandwidth analysis in terms of phase difference and power division is provided. Two prototypes with this proposed structure, operating at 1 GHz, have been designed, simulated, and implemented using microstrip lines. The measurement shows good agreement with the numerical results, which demonstrates the validity of this design.

Highly sensitive refractive index sensing by fast detuning the critical coupling condition of slot waveguide ring resonators.

We experimentally investigate refractive index sensing in silicon slot waveguide ring resonators by the detection of the giant shift of the ring transmission spectrum envelope enabled by the following specific conditions: the slot waveguide cross section as well as the ring couplers have been designed to lead to a V-shaped microring resonator spectrum modulated by the classical frequency comb and exhibiting quality factor peaks of 2000-6000 around λ=1.5 μm. By tracking the spectrum envelope wavelength shift, sensitivity up to S=1,300 nm per refraction index unit (RIU) is reported when the slots are filled by liquids with refraction index values close to 1.33.

A MINIATURIZED 3-DB MICROSTRIP TRD COUPLED-LINE RAT-RACE COUPLER WITH HARMONICS SUPPRESSION

A miniaturized microstrip rat-race coupler with harmonics suppression is proposed by using shorted trans-directional (TRD) coupled lines. The shorted TRD coupled lines consist of a set of capacitor-loaded λ/4 coupled microstrip lines with two shorts, which are used to replace the 3λ/4 uniform transmission-line section (UTLS) in the traditional 3λ/2 ring coupler for miniaturization. To attain perfect matching for any coupling factor of the TRD coupled lines, shorted TRD coupled lines are synthesized and the design equations are derived. To further reduce the ring size, T-type transmission- line equivalent circuits are also adopted to replace the λ/4 UTLS and associated with a transmission zero for harmonic attenuation. Using the proposed method, a microstrip ring coupler with 26.7% circuit size of a traditional one is fabricated and tested. The measured results show that the bandwidth for the return loss of better than 10 dB is 43.9% and that for isolation of better than 20 dB is 18.7% with a maximum isolation of 40.6 dB. There is no spurious passband up to the sixth harmonic of the design center frequency with more than 20 dB suppression from the third to fifth harmonics.

Compact rat‐race ring coupler with meander high‐impedance transmission line and port impedance matching

A novel compact rat-race ring coupler with meander high-impedance transmission line and port impedance matching is presented in this Letter. First, a ring coupler with high port impedance is designed using meander lines. Secondly, an impedance matching section is designed to match the high port impedance to ordinary 50 Ω. The proposed coupler effectively reduces occupied area to 16.8% of conventional one. The design is validated both by simulation and measurement.

Two axis direction finding antenna system using sum–difference patterns in X band

ABSTRACTThis work proposes the direction finding antenna system in two axis (θ1, θ2) in X band using sum (Σ) and difference (Δ) patterns of received signal. Direction finding system is constructed by implementing the microstrip patch antenna array and 180° hybrid rat race ring coupler which generates Σ and Δ patterns of received RF signal. Initially, direction of arrival (DOA) is obtained in one axis, (θ1), vertical direction, using the Σ–Δ patterns of antenna array of two elements. Using the equations of Σ and Δ of two input signals, radiation patterns at different θ values have been observed in simulation and compared with measured pattern values of constructed circuit. By taking the ratio of Δ to Σ patterns, DOA has been estimated of designed circuit. Another circuit similar to first circuit, oriented at 90° (horizontal direction) has been implemented to estimate the DOA (θ2) in other axis. By taking the 3D radiation patterns of each circuit in anechoic chamber, both circuits are measured for performance; and from 0 to ±40°, DOA has been observed with rms error of less than 5° in both axis. At 10 GHz operating frequency, experimental results, using material RT Duroid 5880, show that satisfactory performance can be achieved with proposed setup. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:2085–2092, 2015

Effect of Hartree-Fock exact exchange on intramolecular magnetic coupling constants of organic diradicals.

The intramolecular magnetic coupling constant (J) of diradical systems linked with five- or six-membered aromatic rings was calculated to obtain the scaling factor (experimental J/calculated J ratio) for various density functional theory (DFT) functionals. Scaling factors of group A (PBE, TPSSh, B3LYP, B97-1, X3LYP, PBE0, and BH&HLYP) and B (M06-L, M06, M06-2X, and M06-HF) were shown to decrease as the amount of Hartree-Fock exact exchange (HFx) increases, in other words, overestimation of calculated J becomes more severe as the HFx increases. We further investigated the effect of HFx fraction of DFT functional on J value, spin contamination, and spin density distributions by comparing the B3LYP analogues containing different amount of HFx. It was revealed that spin contamination and spin densities at each atom increases as the HFx increases. Above all, newly developed BLYP-5 functional, which has 5% of HFx, was found to have the scaling factor of 1.029, indicating that calculated J values are very close to that of experimental values without scaling. BLYP-5 has potential to be utilized for accurate evaluation of intramolecular magnetic coupling constant (J) of diradicals linked by five- or six-membered aromatic ring couplers.

AN IMPROVED DESIGN OF DUAL-BAND 3 DB 180° DIRECTIONAL COUPLER

A novel design concept of dual-band 180◦ hybrid ring coupler is presented in this paper. Coupler is a key element in front-end building blocks of wireless transceiver systems such as industrial systems and consumer electronic devices. The proposed design is realized by combining multiple arbitrary length transmission lines operating at two frequencies with one dual-band 180◦ phase shifter. The even-odd mode method is applied to derive the design equations for proposed dual-band 3dB 180◦ directional coupler. Based on the analysis, it is found that the realizable frequency ratio of the proposed coupler is very flexible (i.e., the ratio between the two operating frequencies). Moreover, the 180◦ phase shifter features arbitrary characteristic impedance (i.e., its characteristic impedance can be arbitrarily chosen), which further ensures the easy implementation of proposed structures. To prove the design concept, full-wave electromagnetic simulations are performed to design a dual-band ring hybrid coupler working at 0.9 and 1.98GHz. An experimental prototype is fabricated on Rogers RT/Duroid 5880 board. The measurement results match well with the theoretical and numerical ones.

Comments on ‘planar wideband in‐phase power divider/combiner using modified Gysel structure’

A design of a wideband in-phase power divider/combiner has been presented in Abbosh and Henin (2013). The authors based their design on the traditional Gysel power divider structure and modifled the isolation resistors and the line impedances to obtain the proposed divider. As a matter of fact, it can be shown that the suggested modiflcations of Gysel power divider can be derived as a special case of the more generalised studies in the literature. This communication shows how the results of Abbosh and Henin can be reproduced in a more generalised form from the previous studies of the modifled Gysel power divider structure. The close relation between the proposed divider and the classical ring coupler is also manifested.

Single Longitudinal Mode Fiber Laser Based on Saturated Absorber

In order to realize single longitudinal mode (SLM) output, an erbium-doped fiber (EDF) laser with fiber ring cavity is proposed which uses an un-pumped EDF saturated absorber as a SLM selector. Ring cavity length, coupler ratio and insertion loss which affect ring cavity filter performance are analyzed theoretically and simulated numerically. Un-pumped EDF length and Er3+ concentration are analyzed theoretically and simulated. Research shows that, the bigger coupling output ratio of ring cavity, the greater transmission peak; the greater mode line width; the shorter ring cavity length, the wider free spectral range; the bigger coupling loss, the smaller transmission peak; when the difference between two cavities length is big, cursor effect is not obvious. Laser threshold increases with absorber length increasing; the bigger saturated absorber concentration, the higher laser threshold.

Wideband Hybrid Ring Coupler Based on Half-Mode Substrate Integrated Waveguide

A substrate integrated waveguide ring coupler and a half-mode substrate integrated waveguide ring coupler in X-band are designed from the principle of traditional 180 ° hybrid ring coupler. The HMSIW hybrid ring coupler, adopted closed side to closed side designing for connections of HMSIW branches, is proposed for the first time. It has 24.6% bandwidth for the amplitude imbalance of coupling coefficient less than ±0.5 dB and phase differences between outputs are 15.0 ° ~ -5.8 ° and 175.5 ° ~ 189.7 ° for the in-phase and the out-of-phase operations, respectively, which shows much better performance than SIW coupler.

On‐chip miniaturised wideband rat‐race coupler using integrated passive device technology

In this study, a miniaturised wideband rat-race coupler using glass integrated passive device (GIPD) technology is studied. The circuit miniaturisation is achieved using slow-wave synthesised coplanar waveguides (CPWs). For wideband operation, a compact CPW phase inverter is developed and integrated. At the centre frequency, 12 GHz, the proposed rat-race coupler is only 6.5% the size of a conventional 1.5-λg ring coupler with the same GIPD technology; the fractional bandwidths, on the other hand, reach 65 and 32%, respectively, at the sum and difference ports. The coupler shows good amplitude and phase balances, with the transmission loss around 0.7–1.1 dB at the centre frequency.

Dual-Band Ring Coupler Based on the Composite Right/Left-Handed Folded Substrate-Integrated Waveguide

In this letter, a dual-band ring coupler based on the folded substrate-integrated waveguide (FSIW) is proposed. The artificial structure, the composite right/left-handed (CRLH) transmission lines were implemented in the FSIW by loading the interdigital capacitors in the middle metallic layer to generate a left-handed passband region below the cutoff frequency of the ordinary waveguide ${\rm TE}_{10}$ mode for coupler miniaturization. The FSIW is the folded counterpart of the substrate-integrated waveguide (SIW) and thus can prevent the CRLH transmission lines from radiation loss by shielding the interdigital capacitors in the waveguide. Besides, the FSIW-based coupler is able to eliminate the electromagnetic interference (noise) with adjacent objects and lend itself to multilayer circuit integration. A ring coupler that operates at 4.3 and 7.6 GHz was developed and experimentally verified. To the best of the authors' knowledge, it is the first time that a dual-band rat-race was implemented and reported based on the CRLH-FSIW structure.

BROADBAND AND SMALL-SIZE 3-DB RING COUPLER

A topology for a 3-dB broadband and small-size ring coupler is proposed. It consists of fully-distributed Composite Right-/Left-Handed phase shifters and a Lange coupler. For the fabricated coupler, the frequency bandwidth is one octave, centered on 1.5GHz, while the footprint area is reduced to 25%, compared to the conventional ring coupler topology. The experimental results are in good agreement with the expected ones, obtained by electromagnetic simulation.

Analysis of a Substrate Integrated Waveguide Hybrid Ring (Rat-Race) Coupler

This paper presents an efficient analysis of a substrate integrated waveguide (SIW) single-layer hybrid ring coupler (rat-race) for millimeter-wave and microwave applications. The scattered field from each circular cylinder is expanded by cylindrical eigenfunctions with unknown coefficients that have been solved by electric and magnetic tangential boundary on each metallic via. The coupler S-matrix is calculated by using mode matching that uses the cylindrical vector expansion analysis to minimize the computational time and provides more physical insight. To achieve higher bandwidth, the radiuses of the coupler under analysis have been optimized in Matlab code by invasive weed optimization (IWO) method, and the results have been verified by CST package. The return loss and the isolation are less than −15 dB, and −18 dB, respectively. The insertion loss is divided equally-3±0.2 dB, with0±5and180±10degrees in output ports over the operating frequency bandwidth and the agreement of phase differences in output ports has been examined objectively by feature selective validation (FSV) technique.

SIW-Fed Yagi Antenna and Its Application on Monopulse Antenna

Planar Yagi antennas are commonly hard to possess simple structure, high gain, and broad bandwidth at the same time. In this letter, a new substrate integrated waveguide (SIW)-fed Yagi antenna is proposed with nonplanar director element, and it achieves bandwidth of 25.7% and gain of 9.46 dBi at 10.0 GHz. Integrated of an SIW hybrid ring coupler, a Yagi monopulse antenna is designed. Measured gain of the sum pattern is higher than 13 dBi, whereas the maximum null depth of the difference pattern is lower than ${-}$ 20 dB in 9.4–10.05 GHz. This type of monopulse antenna presents an excellent candidate in directional-finding system.