基于正交定向耦合器组合的微波功率测量方法

定向耦合器广泛应用于微波系统的功率测量.但定向耦合器的方向隔离度有限,两个方向的耦合输出信号存在一定程度地串扰,影响功率测量的准确性.为了解决这一问题,本文提出一种正交耦合测量方法.该方法采用一对相位差为90°的定向耦合器同时测量功率,通过对测量结果的计算处理,可消除方向串扰的影响.推导了正反向传输功率与正交耦合器组合功率测量值的关系,分析了正交偏差所产生的误差.为了确定耦合器的正交状态,提出了一种准确测量两个定向耦合器之间相位差的方法.实测表明正交耦合方法可有效提高功率和驻波比测量的准确性.     

波导平面电路定向耦合器及CAD

本文利用平面电路耦合孔阵作为波导侧壁耦合的定向耦合器电路;该平面电路具有调节耦合度方便、加工简单、生产成本低的特点.本文给出了计算机辅助设计的方法和测试结果.     

A 3-dB Quadrature Coupler Suitable for PCB Circuit Design

A quadrature 3-dB coupler, which combines the advantages of a coplanar waveguide and microstrip line structure suitable for single-layer substrate printed circuit board (PCB) circuit design is proposed. As compared to the conventional Lange coupler, the proposed coupler with the advantages of increasing the coupled linewidths and coupling spacing without using extra bonding wires can solve the drawbacks of Lange coupler. In addition, the proposed structure can easily be realized in a single-layer substrate by PCB manufacturing processes to eliminate the effects and uncertain factors from a multilayer substrate. Good agreements between the simulation and measurement in the frequency range from 0.45 to 5 GHz can be seen. With the operation bandwidth ranging from 1.8 to 2.8 GHz, the measured results of the return loss are better than 18.2 dB and insertion losses of coupled and direct ports are approximately$hbox 3 pm hbox 0.1~hbox dB$; the relative phase difference is approximately 89.8$^circ$. The dimension of the circuit is 2.7 cm$times,$1.6 cm$times,$0.08 cm.     

L波段小体积微带监测耦合器设计研究

提出了一种用于1/8监测网络的微带线定向耦合器,该微带线定向耦合器结构在传统的微带线定向耦合器两端加入补偿电容,具有高定向性,给出了物理模型,对该结构进行了理论分析,并设计制作和测量了该种耦合器。测量结果表明,该定向耦合器的耦合度为26dB,工作频带为1.2～1.4GHz,隔离度超过-53dB,性能指标明显优于传统结构的微带线定向耦合器。同时减小了微带线定向耦合器的尺寸。     

An all single-mode fiber Michelson interferometer sensor

A Michelson interferometer made from a single-mode fiber directional coupler with silver mirrors deposited on fiber ends is presented. This interferometer is simple to fabricate and has a theoretical visibility of unity, irrespective of the splitting ratio of the coupler. A theoretical analysis of its performance is described. Locking to quadrature was achieved by tuning the frequency of the laser source at 1.52μm. Results are presented for the interferometer operating over one kilometer of single-mode fiber, in a passive remote sensing configuration.     

2～12 GHz超宽带带状线定向耦合器的设计

根据带状线理论,设计了一种新型的带状线定向耦合器。通过将耦合带状线分段处理,根据每段带状线的耦合度,合理地设计每段耦合带状线的物理参数,拓宽了耦合器的工作频带。同时通过优化仿真,以补偿耦合器奇模与偶模之间相速度的差异,并抵消不连续性所带来的寄生参数的影响,从而提高定向耦合器的方向性。在设计过程中,借助Ansoft Designer软件进行初步优化仿真,最终电路版图以AutoCad格式导入到HFSS中进行进一步验证。     

A 3-dB Quadrature Coupler Using Broadside-Coupled Coplanar Waveguides

A 3-dB quadrature coupler which combines the advantages of broadside-coupling and coplanar waveguide structure suitable for a single-layer printed circuit board (PCB) circuit design is proposed. Compared to the recently published broadside-coupled structures, the proposed coupler can easily be realized in a single-layer substrate by using PCB manufacturing processes to eliminate the effects of uncertain factors from a multi-layer substrate. With the operation bandwidth ranging from 2.1 to 2.7 GHz, the measured return loss and isolation are all better than 19dB, and the insertion losses and relative phase difference between the direct and coupled ports are at 3.2 plusmn 0.1 dB and 90 plusmn 0.6deg, respectively. The dimension of the coupler is 2.1 cm times 1.9 cm.     

A Side-Arm-Switched Directional Coupler as a Single-Step Attenuator of High Long-Term Stability

This paper describes a single-step attenuator for values below 0.1 dB of very high long-term stability. This uses a directional coupler with a fixed short circuit at one coupled port and a switchable match-or-short at the other. The value of the attenuation step in the transmitting path is governed by the coupling and thus very small steps may be achieved readily. The attenuator is analyzed in full and relationships for a leaky directional coupler are given, together with a flowgraph model of a nonideal coupler.     

Analysis of grating-assisted directional couplers using theFloquet-Bloch theory

The Floquet-Bloch theory is used to develop a theory for grating-assisted directional couplers which predicts the coupled power and coupling lengths and is applicable to lossy waveguides. This theory views grating-assisted directional couplers as conceptually similar to conventional synchronous (nongrating) couplers. In the Floquet-Bloch analysis of the directional coupler, it is necessary to include both proper and improper space harmonics. The determination of which space harmonics are improper is critical to the understanding of the coupler performance. The choice of the improper space harmonics used for the analysis of the coupler is different from that used in contemporary papers     

A Novel 3-dB Directional Coupler With Broad Bandwidth and Compact Size Using Composite Right/Left-Handed Coplanar Waveguides

A wideband composite right/left-handed (CRLH) coplanar waveguide (CPW) coupler with 3-dB coupling value and quadrature phase difference is presented. Compared with the conventional edge-coupled CPW coupler, this symmetrical structure, consisting of a gap capacitor, a broadside-coupled capacitor, and a meandering short-circuited stub inductor, achieves wider operating bandwidth and larger coupling level. The 3-dB CRLH CPW coupler with 0.7mm spacing between coupled lines exhibits an amplitude balance of 2dB and a phase balance of 90⁰ plusmn 5⁰ from 3.2 to 7.6GHz. The coupled-line length and the port impedance of the proposed structure are approximately lambda/4 and 50Omega, respectively, which makes it more compact than the cascaded CRLH microstrip coupled-line coupler. To characterize this structure, the equivalent circuit model including the unique coupling mechanism within CRLH CPWs is established and verified by measurement. The signal with less dispersion on output ports is demonstrated based on the standard deviation of group delay time     

Transient Analysis of a Directional Coupler Using a Coupled Mlcrostrip Slot Line in Three-Dimensional Space (Short Paper)

In recent MIC techniques, double-sided MIC has been studied because its advantages in propagation characteristics are greater than that conventional MIC's. A coupled microstrip slotline is one of them. Its application to various circuit elements has often been discussed. But the coupled microstrip slotline is essentially three-dimensional structure, so the analysis demands a rigorous three-dimensional treatment. Also, the recent high-speed pulse technique demands analysis in the time domain. The present paper treats a directional coupler using the coupled microstrip slotline in three-dimensional space and time. The results of the directional coupler analysis is presented with the complicated time variation of the three-dimensional electromagnetic field. So, the mechanism of the directional coupling phenomena that is produced by the propagation characteristics of the even and odd modes is presented in the time domain, In particular, the instantaneous diagram of the Poynting vector details the energy flow in the transient process. For the analysis of the characteristics of the complex microwave device, these results present the utilities of the various field distributions that are obtained by the three-dimensional vector analysis in the time domain.     

Wide-Band Single-Side Band Subharmonic Mixer Constructed With Re-Entrant Couplers and Lumped-Element Coupler

This work presents a new configuration of single-side band (SSB) harmonically pumped mixer implemented by using two kinds of wide-band quadrature couplers to achieve the characteristics of wide operation bandwidth, high side band suppression and compact circuit size. A new type of 3 dB re-entrant microstrip coupler, which is easy to integrate with the surface-mounted devices, is adopted to achieve the required quadrature phase shifts of the radio frequency (RF) and local oscillation signals. The lump-element type of intermediate frequency coupler is not only able to have broadband characteristics and compact circuit size, but also provide the low-pass filtering function to eliminate the low-pass filter of the mixer in the conventional design. An experimental prototype of the proposed SSB mixer was manufactured. The measured conversion losses of the prototype, which includes the losses caused by couplers, are lower than 13 dB. It also shows greater than 20 dB side-band suppression over the RF frequency range of 2.2 to 2.85 GHz and the measured side-band suppression at some RF frequencies are up to 45 dB. The size of the S-band prototype fabricated on FR4 PCB is only about $40times 45 {rm mm}^{2}$.      

Bragg reflection waveguide composite structures

The Bragg reflection waveguide directional coupler is analyzed rigorously in terms of the normal modes of the complete structure. A perturbation analysis leading to an explicit expression for the coupling constant in a general configuration with nearly degenerate modes is performed. The results are compared to those for a conventional directional coupler structure. It is shown that the bandlike dispersion diagram arising from the periodic lateral confining media is responsible for the unique features of the coupling constant and coupling length that are observed     

A directional coupler of a vertically installed planar circuitstructure

A 3-dB directional coupler is described which is fabricated by installing a vertical second printed circuit board on a main printed circuit board. The added vertical substrate significantly increases the freedom of design parameters. Coupling parameters are easily controlled by changing either the dielectric constants or the thicknesses of the substrates. This makes almost any coupling constant available along with good isolation and a suitable input impedance. The three-dimensional structure also makes a good use of space, resulting in a compact circuit structure. Experimental results agree well with a numerical calculation based on the boundary-element method and show the relaxed tolerances possible in fabrication. Effective permittivities and characteristic impedances for both even and odd modes were obtained and were substituted into the scattering matrix to obtain the parameters for a symmetrical directional coupler. A simplified design chart is also provided showing the dependence of characteristic impedances for odd and even modes on substrate thicknesses used     

A Compact Highly Reconfigurable CMOS MMIC Directional Coupler

This paper presents a tunable CMOS directional coupler that utilizes lumped-element L-C sections. The lumped-element approach used to build the directional coupler makes it possible to integrate the coupler onto a single monolithic microwave integrated circuit (MMIC), as it occupies a small area compared to printed designs. The directional coupler uses varactors and tunable active inductors (TAIs) to synthesize the series and shunt reactances, respectively, which allows extensive electronic control over the coupling coefficient, while insuring a low return loss and a very high isolation. Furthermore, using varactors and TAIs allows the directional coupler to be reconfigured for operation over a wide range of frequencies. Moreover, the symmetric configuration of the coupler allows it to switch from forward to backward operation by simply exchanging the bias voltages applied across the series varactors. The MMIC coupler was fabricated in a standard 0.13-mum CMOS process and operates from a 1.5-V supply. The circuit occupies 730 mum times 600 mum, and is capable of achieving tunable coupling coefficients from 1.4 to 7.1 dB, while maintaining an isolation higher than 41 dB. The MMIC coupler is also capable of operating at any center frequency over the 2.1-3.1-GHz frequency range with higher than 40-dB isolation. The coupler achieves a -4.1-dBm 1-dB compression point while operating from a 1.5-V supply.     

Modified 1×2 directional coupler waveguide modulator

A novel 1×2 Ti:LiNbO3 modified directional coupler modulator is demonstrated. The 3 dB operating point requires no bias voltage. The device has a lower switching voltage requirement than a conventional directional coupler.     

A New Directional Coupler Design with High Directivity for PCS and IMT‐2000

This paper proposes a new design of directional couplers with high directivity for personal communication services (PCS) and International Mobile Telecommunications‐2000 (IMT‐2000). The directional coupler is used to check and verify the power, frequency, and antenna reflection of a signal at transmission stations for mobile communications. The performance requirements of directional couplers are a strong coupling to reduce the effect on the transmitted power and high directivity to suppress the interference of the reflected signals and reduce the errors in communication. So far, various architectures have been proposed to gain high directivity, and there have been many studies used to obtain a strong coupling. However, conventional architectures for high directivity and strong coupling have a directivity of only about 20 dB, and there have been difficulties to achieve the higher directivity of 30 dB suitable for PCS and IMT‐2000. This paper proposes a new architecture of directional couplers based on a grounding composed of strip lines, and compares the test results of this directional coupler with conventional ones. The results show that the proposed directional coupler has a directivity of more than 30 dB and is adequate for PCS and IMT‐2000.     

An Inductor-Loaded Microstrip Directional Coupler for Directivity Enhancement

A directivity-enhancement technique is demonstrated for a microstrip directional coupler. By loading the coupler with shunt inductors, the phase velocities of the even and odd modes are altered in such a way that an isolation null is achieved. Compared with other compensation techniques for directivity enhancements, the proposed method provides the advantages of being simple yet easily application to high frequencies. For a 10 dB directional coupler at 0.9 GHz, a maximum directivity improvement of nearly 38 dB is measured over the conventional counterpart.      

Hybrid-Ring Directional Coupler for Arbitrary Power Divisions

A directional coupler in the form of a hybrid ring is described in this paper. A theoretical analysis using the scattering matrix has been carried out and experimental verification of the theoretical result has been achieved in a stripline network. Simple design equations which enable one to design a directional coupler with any degree of coupling have been derived. This coupler differs from the commonly used couplers in that the voltages at the output arms are either in-phase or opposite-phase with respect to each other. In addition, its geometrical symmetry makes it very convenient for use in symmetrical networks, particularly as a power divider in antenna feeding systems.     

S-band reflection type variable attenuator

A reflection type variable attenuator is described in this letter. The main component of the circuit is a microstrip 3 dB quadrature coupler. The coupler is used in conjunction with two varactor diodes to vary the attenuation from 2.2 dB to 17 dB over a 40% bandwidth (2.8-4.2 GHz). If married with a programmable voltage controller, the proposed design will provide a low-cost solution for applications with narrow instantaneous bandwidth