High-Pass Directional Couplers using a Simple Linear Coupling Function

An analysis of four-arm symmetrical networks such as a branched directional double stub coupler or the hybrid ring (rat race) is presented. The input wave is broken into an even and an odd mode and the vector amplitude out the various arms is computed from the sums or differences of the reflection or transmission coefficients for the two modes. A zero decibel directional coupler is described and its possible use as a duplexer is proposed. The design of multiple stub directional couplers for any degree of coupling is discussed. A method of computing the bandwidth of all these couplers is outlined, and the bandwidth curves, the power out the various arms with respect to frequency of the zero decibel coupler, are computed. A tabulation is made for six different 3 db couplers (even-power split) and their standing wave ratio, evenness of power split and isolation of the fourth arm as a function of frequency assuming perfect performance at the band center.

Single-mode integrated-optic directional couplers on electro-optic substrates can be used to realize photonic space-division multiplexers/switches with low cross-talk level and switching voltage. This paper describes briefly the methods which have been used by the present authors to design 2x2 and 4x4 switch matrices oir LiNbO3 substrates. A computer-aided analytical model has been developed to obtain the two-dimensional distribution of Ti-concentration and refractive index profiles for arbitrary waveguide geometry, Ti-film thickness and processing conditions. The matrix method which is a simple analytical tool for layered structures has been employed to study the wave propagation through Ti indiffused LiNb03 waveguides and directional couplers. The data for refractive index profile required as the input for running the computer program implementing the matrix method were obtained from the above computer-aided analysis. The computed results of Ti-concentration, refractive index profiles and the critical coupling length of directional couplers were validated with available experimental data. Due attention has also been paid to reduce the radiation loss from waveguide bends and to incorporate the polarization dependence in the design of directional couplers. The electrode structure and its placement on Ti:LiNb03 waveguides have been optimized for a 5V switching voltage. The effects of buffer layer and I/O fiber-to-waveguide coupling have also been considered to estimate the total loss. Necessary data generation in appropriate format for electron beam masks for Ti-waveguides and electrode patterns has been completed, and the fabrication of masks is now in progress. A simplistic design of 8x8 switch matrix has also been included.

This paper covers development trends in communication and radar electronic warfare (EW). Threat scenario and role of EW sensors in developing Electronic Order of Battle (EOB) are described. EW is subdivided into Electronic Support Measure (ESM), Electronic Counter Measure (ECM) and Electronic Counter-counter Measure (ECCM) systems. Developments in communication ESM and ECM systems and their constituents are described. Under COM ECM, jammer system configuration and realisation of the constituent subsystems, jamming strategies used for effectively countering various types of communications are described. Developments in critical subsystems and configurations of typical radar EW systems are discussed. Finally the status of the indigenous developments in ESM, ECM and integrated systems are described.

As one of the key component of photonic crystal optical circuit devices, the directional coupler is investigated. We explain the reason the directional coupler consisting of an ordinary symmetric parallel waveguide cannot have a high extinction ratio and a small coupling length simultaneously. To realize both characteristics simultaneously, we propose a novel directional coupler structure. By numerical calculation, we show the possibility of a directional coupler with a high extinction ratio (-24 dB) and a small coupling length (18a).

Power systems are special multi-agent systems with nonlinear coupling function and symmetric structures. This paper extends these systems to a class of multi-agent systems with mismatched parameters, linear coupling function, and asymmetric structures and investigates their velocity synchronization via sampled position data. The dynamics of the agents is adopted as that of generators with mismatched parameters, while the system structures are supposed to be complex. Two distributed linear consensus protocols are designed, respectively, for multi-agent systems without or with communication delay. Necessary and sufficient conditions based on the sampling period, the mismatched parameters, the delay, and the nonzero eigenvalues of the Laplacian matrix are established. It is shown that velocity synchronization of multi-agent systems with mismatched parameters can be achieved if the sampled period is chosen appropriately. Simulations are given to illustrate the effectiveness of the theoretical results.

In this work we present the study of step-index channel directional couplers which can be fabricated on a buffer planar guide in a such a way that they can be properly designed to support separable modal fields, though the index profile is non separable. The main advantage of this approach is the great simplicity in the analysis, design and fabrication of the directional couplers, or other different integrated strucutures, since it is possible to apply, for instance, the effective index method obtaining a quasi-exact solution for the modal fields. Analytical and numerical results will be presented to confirm that an accurate design of the operation properties of the directional coupler can be achieved.© (2003) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

A novel compact easy-to-manufacture design of 20 dB directional coupler has been proposed for a high power operation within frequency band 4-12GHz. In order to obtain the broadband frequency response a three-section asymmetric coupled strip-line directional coupler has been chosen. The periodic structures are introduced on the outer edges of coupled strip-lines to improve directivity and isolation of coupler. The successfully fabricated and tested coupler shows high electrical performances. The proposed 20 dB directional coupler provides within frequency band 4-12 GHz the coupling characteristic imbalance 0.5 dB, isolation 35 dB, directivity 15 dB and VSWR <; 1.35. The allowable input power of directional coupler is up to 100 W. The coupler dimensions are 39 × 35 × 26 mm.

Design method of novel multilayer, broadband six port microstrip directional coupler at VHF- UHF range for high power applications is given. Directional coupler is modeled and simulated with the method of moments based planar electromagnetic simulator on a two-layer Alumina substrate. It is shown that the high directivity and desired coupling level of the directional coupler are maintained within 300MHz of bandwidth using the proposed design method in this paper. Results of this work can be used in the design of broadband directional couplers for high power RF/Microwave applications.

This paper reports a new design of microstrip directional coupler with high directivity. This directional coupler uses corrugated coupled lines and floating conductor in the ground plane of microstrip to enhance coupling. Based on this structure, directional coupler having 4.4% bandwidth has been designed at 4500 MHz with 10 dB coupling and 35 dB directivity. The designed directional coupler has been fabricated and tested for the validity of the design. Measured results are presented in this paper.

We design and compare the splitting ratio wavelength flatness of directional coupler (DC), Mach-Zehnder directional coupler (MZDC), and tandem MZDC. All coupler responses are analyzed, and tandem MZDC performance is the best in the wavelength insensitivity compared with the other two. An MZDC with any coupling ratio could be utilized to match the maximum flatness in a 40-nm wavelength range. To extend a broad flatness range, the tandem MZDC is proposed and still follows the Mach Zehnder structure taking two MZDCs as couplers connected through a decoupled region. Unlike DC, MZDC with the flat wavelength response has a non-linear output phase. Hence, using two wavelength-insensitive MZDCs as the coupling function in a tandem MZDC could demonstrate a more extensive decoupled phase term to maximize the flat wavelength response. The tandem MZDC theoretically demonstrates the splitting ratio with 100-nm flatness in the wavelength range from 1250 nm to 1350 nm. Finally, a point spread function through the tandem MZDC shows a 24-dB signal-to-noise ratio improvement in optical coherence tomography applications.

A multi-element directional coupler is considered as a cascaded set of 2-element directional couplers, each of which, at the design frequency, is perfect in match and directivity. A characteristic impedance matrix and a voltage transfer matrix may be defined for each of the basic 2-element couplers, and these are analogous to the characteristic impedance and the propagation coefficient in iterative 4-terminal network theory. The voltage transfer matrix is shown to be a linear function of the cosine and sine of a certain angle which is related in a simple way to the coupling factor of the elemental coupler. This function has algebraic properties analogous to those of complex numbers. In particular, the use of de Moivre's theorem is shown greatly to simplify the design of multi-element couplers. An example is given of the design of a 5-slot 3 dB coupler (a binomial slot hybrid).

Directional couplers based on antiresonant reflecting optical waveguides (ARROW) have been fabricated and tested. The exchange of power from one waveguide to the other could be well controlled by adjustment of geometrical parameters such as the coupling length and/or the etch depth of the rib ARROW waveguide. Simulations based on the beam propagation method yield good agreement with measurement data and has been found to be indispensable for accurate design and analysis of ARROW directional couplers. Owing to the ARROW structure, the directional couplers presented have the feature that they also perform the polarizing function.

This paper describes a design of microstrip rectangular disk quadrature directional couplers on the basis of a modified eigenfunction expansion method with consideration of frequency dependences of an effective width and an effective relative permittivity of a microstrip disk circuit. Using this approximate method, we can optimize the disk configuration of directional couplers in a reasonable computational time. The validity of the design method is examined by comparison with the numerical results by the FDTD method.

In this paper, the performance analysis on hybrid plasmonic waveguide (HPW)-based symmetrical directional coupler (DC) is proposed, which contains two parallel arms. In this analysis, one HPW arm performs as an input port and bar (parallel) output port; another HPW arm doings as a cross output port. The principle of DC is satisfied by the coupling of transverse magnetic field (TM) from the bar port to cross port. In the proposed DC, the mode characteristic parameters such as normalized mode area and propagation length are calculated by finite element method (FEM), and performance of the device is analyzed by certain parameters such as propagation loss, cross-talk, insertion loss, and coupling ratio. Hence, the proposed DC is designed with low cross-talk, low insertion loss, low propagation loss, and high propagation length, which could be appropriate for ultra-dense photonic integrated circuits (PICs).KeywordsOptical waveguidesDirectional couplerFinite element method

Experimental design and operation of a directional fiber coupler having identical-output ratio is successfully fabricated. The coupling region is imposed by fusion temperature 800-1350 0 C injecting the Hydrogen gas at 1Atm. Concurrently the coupled-mode theory is used to model power transfer between the waveguides by using transfer matrix method. By 1mW source input power to one of three input ports, it shows that power propagation among three coupled fibers is normalized; the optical fiber are nearly identical and a similar separation between them. The matrix configuration of 3X3 is also used to calculate the polarization effect of directional fiber coupler. It is found that the incident power polarized with various angle causes power output at both three output ports decrease exponentially. This 3X3 directional fiber coupler design is a significant passive component for various functions power splitter and routers.