Trans-directional Coupler Research Articles

Filtering coupler with tight coupling based on trans-directional coupler

Filtering coupler with tight coupling based on trans-directional coupler

Design of Active Integrated GNSS Antenna Based on the Impedance Transforming Quadrature Four-Feed Network

In the paper, a wideband miniaturized impedance-transforming quadrature four-feed network with a flat output phase difference is presented and applied to the design of an active integrated GNSS antenna where no extra impedance matching circuit is needed. The features of impedance transformation and flat output phase difference are achieved by the proposed miniaturized rat-race coupler. When combining the proposed rat-race coupler with two trans-directional (TRD) couplers, a four-feed network with stable sequential quadrature phase shifts is obtained in the whole GNSS band. Since the quadrature four-feed network has the feature of impedance transformation, integration with a low-noise amplifier (LNA) can be realized without extra impedance matching circuits, which reduce the overall size and losses. For validation, a simple rectangular patch is applied as the radiator, and the active prototype is fabricated. Measurement results show that over the entire GNSS band from 1.164 GHz to 1.610 GHz, the miniaturized integrated antenna exhibits a return loss of more than 10 dB, an axial ratio of less than 3 dB axial ratio, and a gain of greater than 16 dBic.

Deep-learning-based neural network for design of a dual-band coupled-line trans-directional coupler

Deep-learning-based neural network for design of a dual-band coupled-line trans-directional coupler

Theory of Doubly-Shielded Coupled Lines for Directional Couplers of Various Directivity Types With Impedance Transformation

Asymmetric coupled lines (CLs) with double shielding in an inhomogeneous dielectric medium are studied. They have specific properties that allow the creation of impedance-transforming directional couplers with a given directivity type. The proposed models and synthesis techniques take into account both electric asymmetry and dielectric inhomogeneity. Numerical simulations and measurements prove the correctness of the general theory, and the possibility of creating co-, contra-, and trans-directional couplers with impedance-transforming and phase-shifting properties. The results will be useful for finding new design solutions for next-generation microwave circuits.

Optimum Design of Multi-Section Asymmetrical Transdirectional Couplers with Port Impedance Matching up to S Band Frequency

The method of least squares is developed for the optimum design of multi-section asymmetrical transdirectional (ATRD) couplers with arbitrary port impedance matching. Firstly, transmission matrix of a section of coupler is obtained, then the transmission matrix of whole multi-section coupler is determined, from which the scattering matrix of device is obtained. An error function is then constructed by scattering parameters. According to design specifications, error function depends on physical parameters of coupler (such as widths, spacings and lengths of transmission line sections and capacitor values), of which minimum point gives optimum values of it’s dimensions and capacitors. Optimum design is carried out for a specified frequency response and bandwidth. Error minimization is implemented by the combination of genetic algorithm (GA) and conjugate gradient method (CGM). The design is verified by full-wave simulation software, fabrication and measurement. Several 3 dB, 6 dB and 10 dB couplers are designed with different bandwidths and port impedances. Compared to the proposed design method, design of asymmetrical multi-section couplers by full-wave simulation softwares is by trial and error and at best random and almost impossible because of extremely high CPU time due to the large number of parameters of coupler geometrical structure.

An experimental research of the ultra-wideband pulse propagation in a transdirectional coupler based on coupled striplines

An experimental research of the ultra-wideband pulse propagation in a transdirectional coupler based on coupled striplines

Synthesis of miniaturized filtering coupled‐line trans‐directional coupler with wide suppression band

In this paper, the synthesis of miniaturized filtering coupled-line trans-directional (CL-TRD) coupler with wide suppression band is presented. This coupler is formed by two parallel coupled lines, one capacitor-loaded coupled line, and four sub-circuits. With the introduction of the sub-circuits, extra transmission poles located at the cut-off frequency are generated, resulting in high frequency selectivity. Size reduction is also achieved. Design equations of the filtering CL-TRD coupler are derived using the even-odd mode decomposition analysis and design procedures are provided for guidance. For demonstration, a 3 dB prototype with a size of 0.46 λg × 0.21 λg is designed, fabricated and measured. The measured results validate the 32% bandwidth centered at 1 GHz with more than 10 dB return loss/isolation, less than 0.5 dB amplitude imbalance and 5° phase error. Besides, a 15 dB wide stopband from 1.18 to 5.07 GHz (5.07f0) is obtained with a sharped skirt selectivity.

Связанные линии с двойным экраном для СВЧ-мостов различного типа направленности с трансформирующими свойствами

Asymmetric coupled double-shielded lines in an inhomogeneous dielectric medium, which have special properties that allow us to create microwave hybrids of a given directionality type are investigated. For the first time, a new model and method of synthesis are proposed, which takes into account both the asymmetry and the inhomogeneity of the dielectric, which makes it possible to synthesize co-, counter- and transdirectional couplers that have both the transforming and required phase properties. The research results will be useful for finding new design solutions of the next generation microwave circuits.

An experimental research of the ultra-wideband pulse propagation in a transdirectional coupler based on coupled striplines

The propagation of short picosecond pulses in coupled strip lines with a phase velocity ratio of odd and even modes of 3:1 is considered. The feature of the separation of the input pulse between the three output ports without significant loss of energy due to reflection from the input in transdirectional couplers based on coupled strip lines is experimentally shown. As a result of the analysis, it was found that the spectral components of the pulse are separating between the ports of the transdirectional coupler.

A class of coupled-line trans-directional coupler with independent or simultaneous tuned frequency, coupling coefficient and phase difference

The paper reports on the design of coupled-line trans-directional (CL-TRD) coupler with independent or simultaneous tuned frequency, coupling coefficient and phase difference (PD). Based on the proposed structure, four kinds of couplers are exhibited, including a phase-tuned coupler with arbitrary frequency and coupling, a frequency-tuned coupler with arbitrary coupling and non-standard phase, a coupling-tuned coupler with arbitrary frequency and non-standard phase, a simultaneous frequency-, coupling- and phase-tuned coupler. In the section of theoretical analysis, rigorous closed-form design equations are derived using the even-odd mode analysis. For verification, four prototypes are designed, fabricated and measured. Three of them are couplers with independent frequency, coupling or phase tuned. The designed 3-dB frequency-tuned coupler exhibits a frequency tuning range of 58.8% with a PD of 60°. The coupling-tuned coupler shows a tuning range of 3–15 dB with a PD of 70°. The designed phase-tuned CL-TRD coupler can provide a PD from 45° to 135°. Finally, a coupler with simultaneously frequency-, coupling- and phase-tunable was implemented. It has a wide frequency tuning range from 1.2 GHz to 2 GHz with a tunable coupling from 3 dB to 15 dB, and a tunable PD from 45° to 135°.

Beamwidth-Enhanced Low-Profile Dual-Band Circular Polarized Patch Antenna for CNSS Applications

A low-profile dual-band circular polarized (CP) patch antenna with wide half-power beamwidths (HPBWs) is presented for CNSS applications. Simple stacked circular patches are used to achieve dual-band radiation. To enhance the HPBW for the two operation bands, a dual annular parasitic metal strip (D-APMS) combined with reduced ground plane (R-GP) is presented. A single-input feed network based on the coupled line transdirectional (CL-TRD) coupler is also proposed to provide two orthogonal modes at the two frequency bands simultaneously. Experimental results show that the 10 dB impedance bandwidth is 32.7%. The 3 dB axial ratio (AR) bandwidths for the lower and upper bands are 4.1% and 6.5%, respectively. At 1.207 GHz, the antenna has the HPBW of 123° and 103° in the xoz and yoz planes, separately. And the values are 127° and 113° at 1.561 GHz.

Design of Arbitrary-Phase-Difference Transdirectional Coupler and Its Application to a Flexible Butler Matrix

In this article, an arbitrary-phase-difference (A-PD) transdirectional (TRD) coupler is proposed and applied in the design of a flexible Butler matrix. The A-PD TRD coupler, which also features the characteristics of arbitrary power division and miniaturized size, is composed of four sections of coupled lines and four types of capacitors. Explicit equations for designing the A-PD TRD coupler were derived utilizing the even–odd mode decomposition analysis, and guidelines to obtain the circuit parameters were also given. To demonstrate the design procedure, examples of the proposed coupler are provided and the relevant studies on the coupler’s electrical parameters are conducted. By combining the proposed coupler with the TRD coupled-line-based crossovers and the −45° phase shifters, a miniaturized $4 \times 4$ Butler matrix with flexible output ports phase differences (−25°, 155°, −115°, and 65°) is implemented. It inherits the features of the TRD coupler including A-PD and compact size. At the center frequency, the measured amplitude and phase imbalances are less than 1.4 dB and 3.2°, respectively, between the output signals. Compared to state-of-the-art A-PD-coupler-based Butler matrix, the proposed structure shows a smaller size ( $1.35 \lambda _{g} \times 1.36 \lambda _{g}$ ) and a wider bandwidth (20%).

Analysis and Implementation of a Dual-Band Coupled-Line Trans-Directional Coupler

This brief presents, for the first time, the analysis and implementation of a dual-band coupled-line trans-directional (CL-TRD) coupler. It is realized by cascading three periodically capacitor loaded coupled line segments, which are equivalent to a symmetric stepped impedance coupled line with a 180° difference between the even- and odd-mode electrical lengths. Explicit design equations of the proposed coupler were derived using the equivalent approach and the even-odd mode decomposition analysis. For demonstration, a 3-dB CL-TRD coupler operating at 0.9/2.4 GHz was designed. Under the criterion of | ${S} _{11}$ | ${S} _{21}$ | < −15 dB, the measured relative bandwidths are 37.8% and 10%, respectively, for the lower and upper bands. While for amplitude imbalance < 1 dB, the relative bandwidths are 35.6% and 8.3%, relatively, with the output ports phase differences of ± 90 ± 5°.

Wave properties of the group delay correctors based on coupled strip-lines with different inphase and antiphase wave phase velocities

ABSTRACTWe considered the effect of the imbalance of the inphase and antiphase electromagnetic wave phase velocities on wave properties of group delay time corrector circuits based on contradirectional and transdirectional couplers. We obtained equations for the analysis of the wave dissipation matrix frequency response as a function of the resistance of the elements defining the specified phase frequency response and group delay. In addition, we obtained the group delay time difference as 3 ns under return and minimum insertion losses in the range of 17–20 dB in the 0.35–0.7 GHz bandwidth. We showed that systems based on contradirectional couplers can exhibit a deviation of 20% in the phase velocity ratio of the inphase and antiphase waves without the degradation of the corrector performance. It was found that the increase in the imbalance of phase velocities results in the narrowing of the operating bandwidth, while a transdirectional coupler enables the increase of the passband while maintaining the specified return losses.

Coupled‐line trans‐directional coupler with arbitrary power divisions for equal complex termination impedances

In the study, a coupled line trans-directional (CL-TRD) coupler that allows for equal complex termination impedances with arbitrary power divisions is presented. It is composed of two pairs of coupled lines with an overall electrical length of 90°, two types of shunt capacitors and three pairs of short-circuited stubs. By adjusting the electrical length of each short-circuited stub, as well as the values of the shunt capacitors, arbitrary equal complex termination impedances and power divisions are achieved. Moreover, since capacitors are shunted between the coupled lines, the proposed CL-TRD coupler has an inherent feature of dc blocking. Design equations for the CL-TRD were derived using even-odd mode decomposition analysis. To validate the theory, several numerical examples extracted from the design procedure were listed. Eventually, two prototypes of the proposed CL-TRD coupler are fabricated, and experiments are carried out. The measured results indicate that the coupler is able to realise arbitrary power divisions for equal complex termination impedance with good matching and isolation.

Properties of multisection transdirectional coupled‐line couplers

This study is presented to explore the properties of multisection transdirectional coupled-line couplers (TRD CLCs) developed for bandwidth enhancement. Unlike conventional multisection contradirectional coupled-line couplers (CTD CLCs) comprising only CTD CLCs, the proposed multisection TRD CLCs may require the combination of transdirectional and CTD CLCs for some higher-order designs. The designs feature a central TRD CLC. A symmetrical structure with respect to the central coupler is proposed to meet the port assignments of transdirectional couplers with broadband performance on the magnitude difference as well as the phase difference of 90° between two output ports. It can offer multiple solutions for some multisection designs. Practical examples are presented for 3 dB multisection TRD CLCs with optimum coupling coefficients assigned to individual couplers to achieve maximum bandwidth. Periodic structures are used to implement coupled-line couplers. Simulation results indicate that the proposed multisection designs meet the required port assignments and offer wider bandwidth compared to a single design of the same coupling. The simulation results of the three-section design are verified experimentally and good agreement is observed.

A Compact Trans-Directional Coupler With Wide Frequency Tuning Range and Superior Performance

In this paper, a compact coupled-line trans-directional (TRD) coupler with wide continuous frequency tuning range and superior performance is presented. The proposed tunable TRD coupler is composed of three coupled lines, two shunt stubs, and three types of varactors. By providing suitable reverse bias voltages on these varactors, the operating frequency of the proposed TRD coupler can flexibly be adjusted as desired. Moreover, better impedance match and port isolation are maintained at all tuning center frequencies. A theoretical analysis using the even–odd mode theory is presented to clarify the influence of the design parameters on the minimum and maximum operating frequencies. It is exhibited that the proposed TRD coupler has approximately 150% frequency tuning range in ideal conditions. Due to the manufacturing limitation, a microstrip TRD coupler with a tunable frequency of 1.0–2.5 GHz (85.7%) is designed and fabricated. The measured results show that the proposed TRD coupler can be tuned from 1.0 to 2.5 GHz with more than 27 dB return loss and more than 35 dB isolation in the entire tuning range, agreeing well with the simulation results.

Trans‐directional coupler with adjustable coupling coefficients and reconfigurable responses

The study presents the theoretical and experimental study of a trans-directional coupler with adjustable coupling coefficient and reconfigurable responses. The proposed coupler is composed of coupled lines, capacitors, varactor and inductors. By connecting different inductors through switches for the circuit implementation, and using varactor as compensation capacitor, the coupling coefficient of the proposed coupler can be easily controlled. It also features balanced output ports power distribution, high isolation, good return loss, and consistent output ports phase difference. In addition, when no inductors connected, the proposed coupler is reconfigured to be a crossover. Closed-form design equations are derived by utilising the even–odd mode method. Based on these analytical equations, an experimental prototype is designed, fabricated and characterised. The measured results show that the coupling coefficient of the coupler can be adjusted from −3 to −40 dB with good isolation and return loss performances.

Modified coupled line trans‐directional coupler with arbitrary power divisions and its application to a 180° hybrid

A modified trans-directional (TRD) coupler for designing compact coupled line 180° hybrid with non-interspersed input/output ports is proposed. The modified TRD coupler which is composed of a coupled line and three different shunt capacitors features the characteristic of arbitrary power division and dc blocking. Design equations for the modified TRD coupler are derived using the ABCD matrix. Based on the modified TRD coupler and combined with the coupled line contra-directional (CTD) coupler, a novel coupled line 180° hybrid is constructed. It inherits the characteristics of the modified TRD coupler including arbitrary power division and dc blocking. Moreover, the input and output ports of the 180° hybrid are non-interspersed. In the topology of the proposed 180° hybrid, no bond wires, via holes or multilayer structures are required. The configuration of the 180° hybrid is analysed and the design equations are derived. Using the design equations, the coupling coefficients of the CTD and the modified TRD coupler can be flexibly chosen according to different fabrication conditions. As an example to validate the feature of the proposed 180° hybrids, two prototypes with 3 and 6 dB coupling coefficients are devised. The measured results are in good agreement with the simulated ones.

Novel dual-band antenna for multi-mode GNSS applications

A novel dual-band antenna is proposed for mitigating the multi-path interference in the global navigation satellite system (GNSS) applications. The radiation patches consist of a shorted-annular-ring reduced-surface-wave (SAR-RSW) element and an inverted-shorted-annular-ring reduced-surface-wave (ISAR-RSW) element. One key feature of the design is the proximity-coupled probe feeds to increase impedance bandwidth. The other is the defected ground structure band rejection filters to suppress the interaction effect between the SAR-RSW and the ISAR-RSW elements. In addition, trans-directional couplers are used to obtain tight coupling. Measurement results indicate that the antenna has a larger than 10 dB return loss bandwidth and a less than 3 dB axial-ratio (AR) bandwidth in the range of (1.164–1.255) GHz and (1.552–1.610) GHz. The gain of the passive antenna in the whole operating band is more than 7 dBi.