Directional coupler is used to couple the microwave power which may be unidirectional or bidirectional. Directional coupler characteristics software arm chain coupler v. Pdf design and characteristics of directional coupler based. It consists of two parallel striplines coupled over a length of approxi. Design and simulation of microstrip directional coupler with. If power is reflected back from the output port, the ideal directional coupler does not allow any. The filter structure is simply a conventional directional coupler. Simulated characteristics of a nonlinear directional. The nonlinear coupling characteristics of the nonparallel coupler due to photorefraction is investigated using coupled mode theory with a steplike refractive index profile. A directional couples is a device capable of extracting a part of a signal that travels over a transmission line or waveguide, leaving the rest of power not coupled direct route at the exit. The characteristics of a nonlinear directional coupler. Simulated characteristics of a nonlinear directional coupler.
Thinfilm directional couplers cp0805 and cp0603 test jig general description this jig is designed for the testing of cp0805 and cp0603 series directional couplers using a vector network analyzer. Rf couplers directional, bidirectional, dualdirectional. Directional coupler theory and definitions when power is introduced at the input port, all of the power appears at the output port except for the portion intended to be sampled. Amphenol offers broadband directional couplers for indoor applications. In this paper, a rigorous characterization of an optical wavelength filter is investigated through the cmt 12. The bethehole is a reverse coupler, as opposed to most waveguide couplers that use multihole and are forward couplers. The device couples part of the transmission power by a specific factor.
Pdf design and characteristics of directional coupler. Directional coupler deed to measure reflected power 7246. Design considerations for directional couplers dtic. The project microwave directional couplers was realized under the supervisor.
Simulated characteristics of a nonlinear directional coupler based optical switch baljit singh1. Measure the characteristics of a directional coupler. Bogaerts 1,2 1 ghent university imec, photonics research group, department of information technology, ghent, belgium 2 center for nano and biophotonics nb photonics, ghent, belgium we present a parameterized model for the directional couplers that accurately. To start the virtual experiment the user has to download the file directionalcoupler. But, how do we design a coupledline coupler with a specific coupling coefficient c. In this paper, we present a noble design of nonlinear directional coupler to reduce the optical switching power. Internal view of a typical coaxial coupler figure 3. It consists of a fr4 multilayer substrate, having 50.
Fabricated optical directional couplers with siwire waveguide and evaluated their fundamental characteristics. Abstractin this paper, a novel wideband directional coupler using coplanar waveguide. Demonstrated wavelengthselective characteristics of light output from long directional couplers. Directional coupler is a 4port waveguide junction consisting of a primary main waveguide and a secondary auxiliary waveguide. In this way, power entering the output port is coupled to the. Directional couplers and hybrids directional couplers and hybrids are used in a variety of important applications at microwave frequencies. Figure 1 schematic diagram of directional coupler 9 directional couplers have four ports as shown in figure 1. Power dividers and directional couplers are in all essentials the same class of device. Minicircuits full line of directional couplers, spanning 5 khz to 2 ghz, provide excellent performance.
The branchline coupler consists of four transmission lines, each a quarterwavelength long at the target frequency. The accuracy is due to dimensional tolerances that can be held for the spacing of the two. If the input is port 1, then the through port is port 2, the coupled port is port 3, and the isolation port is port 4. By analyzing the evenmode excited circuit of le directional coupler and that of parallel coupledline directional coupler with open ed and shorted terminations at each symmetrical plane, respectively, we can get the input admittances as blew 0 2 t jzc e jy etg 4 2 1 0 t z jy. Directional coupler in microwave working, internal structure and scattering parameters. Directional couplers can be realized in microstrip, stripline, coax and waveguide.
Prabhakar 1pg student of gujarat technological university, 2assistant professor at l. Directional coupler project rick campbell portland state university october 2012. Pdf directional couplers with linear and nonlinear elements. Diagram of a typical coaxial directional coupler figure 2.
Directional coupler dc is a passive, reciprocal, fourport device, where one port is isolated from the input port. Directional coupler tends to be used for 4port devices that are only loosely coupled that is, only a small fraction of the input power appears at the coupled port. The general concepts about multisection directional coupler, and also for our focus threesection are mentioned in the previous design part. The following figure shows the image of a directional coupler. A directional coupler is a reciprocal network where in theory all ports are ideally matched and the circuit itself is theoretically lossless 7. Coupling properties are discussed using the conventional coupled mode theory and band diagrams calculated by a mix of the planewaveexpansion method and an e. The optical switching characteristics of threeor multiwaveguide nonlinear directional couplers in linear or circular coupling configurations have also been studied 34567 8 91011. Rick campbell portland state university october 2012. Forward wave sampled wave through wave isolated wave 12 3 4 figure 1 directional coupler model. Directional couplers can be designed using microstrip, stripline, coax, or waveguide technology.
The model of a directional coupler is shown in figure 1. All four ports are ideally matched, and the circuit is ideally lossless. Directional couplers are specified in terms of the coupling accuracy at the frequency band centre. Directional couplers are passive reciprocal networks, which you can read more about on our page on basic network theory. Project example directional coupler design signal flow graphs, evenmode oddmode transmission line theory, smatrix, linear algebra go straight from maxwells equations to.
It is explicitly shown by example that the radiation modes that take part in the coupling are just those needed to form the guided modes of the composite doubleguide. The forward travelling wave goes into port 1 and exit from port 2. The importance of directivity is illustrated in the following example. Directional coupler power dividers and directional couplers a directional coupler is a passive device which couples part of the transmission power by a known amoun t ou t through another port, often by using two transmissio n lines set close enough together such that energy passing through one is coupled to the other. Osa analysis of a directional coupler by coupled modes. The coupling system usually happens within a quarterwavelength or on different quarterwavelength portions of the device. The way a directional coupler functions can be depicted as shown in fig. Port 3 is the coupled port 9 where a portion of the power applied to port 1 appears depending on coupling factor. Coaxial directional couplers are offered for use at frequencies from 100 khz to 50 ghz, and can be obtained with any of the standard or precision miniature coaxial figure 1. Design and characteristics of directional coupler based. The performance of the directional coupler is usually evaluated by its directivity between port 3 and 4. Teppati et al broadband coaxial directional couplers for highpower applications 997 broadband coaxial coupler prototypes has been constructed and measured, demonstrating very good agreement with simulations and confirming the validity of the proposed design method. Occasionally, a requirement arises that requires a dual directional coupler monitoring power in the same signal direction. The characteristics of a nonlinear directional coupler with.
The derivation of the relevant equations is, unfortunately, rather lengthy, so for simplicity we base the analysis on scalar theory, and concentrate on the central region of the device where the guides run parallel. Design, simulation and development of wideband directional coupler at s band 1mr. Merrimac catalog directional couplers yield good unittounit phase and amplitude uniformity. The directivity is a calculated parameter from isolation and coupling factor and shows how. Since, the objective is to design the directional coupler for irnss receiver where the received power is in terms of mw, microstrip coupler is selected. Merrimac directional couplers are available in four different classes. Found extremely short coupling lengths 10 um, which means that they can be used as compact power dividers or combiners. The directional coupler and the travelingwave directional filter made of coupled slowwave microstrip lines are proposed and their characteristics discussed. Merrimac directional couplers are precision devices carefully designed for monitoring incident and reflected power. Power dividers and directional couplers are passive devices used mostly in the field of radio. The calculated results show no significant degradation of the performance of the device when less than 3. There is high isolation between the coupled port and the output of the mainline.
It is equal to the theoretical minimum mainline insertion loss. In the terminology of the directional coupler, we say that port 1 is the input port, port 2 is the through port, port 3 is the coupled port, and port 4 is the isolation port. It provides the ability to measure forward and reflected power levels. The couplers can be broadly categorized by type, frequency or coupling factor. Design and characteristics of directional coupler based filters. Directional, bi directional, dual directional and rf taps. Bethehole is a waveguide directional coupler, using a single hole, and it works over a narrow band. The branchline coupler is used to generate quadrature signals for our qam radio. Two have the characteristic impedance of the terminations ports p 1p 4 and two have one that is reduced by 1v2 or is 35. Key characteristics of a directional coupler include coupling coefficient.
Directional, bidirectional, dualdirectional and rf taps. Other directional coupler characteristics include its general utilization of the distributed properties of microwave circuits. Directional coupler is used to couple the microwave power which may be unidirectional or bi directional. Influence of a directional couplers parameters on the results of forward and reflected power measurements white paper products. Some commonly used schematics for the dc are shown in figure 9. Unrestricted parameters of a directional coupler 01. Many reference papers for directional coupler have been studied. Optical directional coupler based on siwire waveguides. This paper describes the fabrication and characteristics of a twodimensional photoniccrystal slab directional coupler with a coupling length of 31mm.
It means there is no coupling due to third order nonlinearity and hence directional coupler should behave like a linear directional coupler. However, as it can be seen from figure 1 directional coupler has an important parameter, length. A directional coupler is an electronic component having fourport circuits with one port being isolated from the input port and another being considered as a through port. The device is normally used to split the input signal and distributed power. Broadband silicononinsulator directional couplers using.
Rf directional coupler basics tutorial rf directional couplers are passive devices that couple power travelling through the device to another port enabling the signal to be used in another circuit. Broadband silicononinsulator soi directional couplers are designed based on a combination of curved and straight coupled waveguide sections. For a 20 dbthree sections edge coupled line directional coupler, constructed as a stripline with ground plane, spacing of b3. Pdf the characteristics of a slotcoupled directional coupler. A directional coupler is an electronic component having fourport circuits with one port. Directional couplers an overview sciencedirect topics. Broadband coaxial directional couplers for highpower.
The coupling process is explained by the mutual coupling of modes of a single waveguide that is due to the presence of the other waveguide. Design and simulation of microstrip directional coupler. Theoretical and experimental results for a 10db coupler at 10 ghz are. A graph of the theoretical insertion loss db vs coupling db for a dissipationless coupler is shown in figure 2. Microwave engineering directional couplers tutorialspoint. Broadband silicononinsulator directional couplers using a.
A schematic representation of the coupler is as follows. Published specifications for directional couplers usually include coupling, directivity, insertion loss, main line and auxiliary line vswr, bandwidth, frequency. Crucially, a directional coupler will ideally sample power in only one direction, discriminating between forward and backward traveling signals. To study the switching properties of nldc, coupled mode theory. The coupledline couplerif our design rules are followedresults in an ideal directional coupler. Diagram of a typical directional coupler the basic construction of a coupledline directional coupler can be seen in figure 1, which illustrates a typical coaxialline, microwave directional coupler such as might be used for microwave applications. Directivity is a measure of how well the coupler isolates two oppositetraveling forward and reverse signals at the coupled port. Analysis of a directional coupler by use of rigorous coupledmode theory is presented. The theoretical insertion loss db vs coupling db for a dissipationless coupler is shown in. Pdf analysis and design of slotcoupled directional couplers. What is an rf directional coupler electronics notes. As an analysis of a threesection coupler given c 1 c 3, c 2 values we can calculate the coupling coefficient of the whole coupler as following.
Multihole waveguide directional couplers abstract the directional couplers are inherently assumed as fourport devices, which consisted of two transmission lines that are electromagnetically. These structures exhibit interesting characteristics not readily available in conventional transmission lines. Coupling values merrimac catalog couplers are available in 6, 10. If power is reflected back from the output port, the ideal directional coupler does not allow any of the reflected power to appear on the secondary line. Design, simulation and development of wideband directional. One key feature of directional couplers is that they only couple power flowing in one direction. The selectivity with which the coupler can select between forward and reverse waves is called the directivity, and it is usually the most important factor in selecting a directional coupler.
Project example directional coupler design signal flow graphs, evenmode oddmode transmission line theory, smatrix, linear algebra go straight from maxwells equations to basic rlc circuit theory, and from there quickly to a complete, buildable design. Wavelengthdependent coupling characteristics in two. The origin of the name comes from a paper published by h a bethe, titled theory of diffraction by small holes, published. There exist many empirical formulas for the characteristic impedance of the line. Here for better coupling, our length consideration is l 4. Suppose we want to measure the power traveling down a transmission line terminated by unknown impedance. For most directional couplers, the features which are desired are high. Key characteristics of a directional coupler include coupling coefficient, coupling flatness, mainline loss and directivity, defined on the next page. Figure 3 shows the transmitted and coupled normalized power of the nonlinear directional coupler, when the nonlinear coupling coefficients k 3 0, and k 4 0. Although this would seem to be a particularly mundane and simple task, these devices are both very important in microwave systems, and very. Transformerbased, ltcc, striplinemicrostrip, bridge, and mmic designs.
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