Equal Split Wilkinson Power Divider - Project Report

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Equal Split Wilkinson Power Divider - Project Report

  1. 1. Design of EqualSplit WilkinsonPower Divider Submitted by Bhanwar Singh, ECE 4th Year, En. No. 08116009 J.Muralidhara Chary, ECE 4th Year, En. No. 08116019 Under the guidance of Dr. M. V. Kartikeyan
  2. 2. DEPARTMENT OF ELECTRONICS AND COMPUTER ENGINEERING INDIAN INSTITUTE OF TECHNOLOGY ROORKEE ROORKEE – 247667 AcknowledgementWith deep sense of gratitude, we express our humble thanks unto ouresteemed supervisor, Dr. M.V. Kartikeyan (Professor, Department of Electronicsand Computer Engineering), for assigning us this project and hence helping usto learn. His valuable guidance helped us to carry out this work under hiseffective supervision.We also express our heartiest gratitude to our friends for their invaluable adviceandencouragement.J.Muralidhara CharyBhanwar Singh Place:IIT Roorkee
  3. 3. Table of Contents1. Introduction……………………….….……..……………………….….…..……..…………..………… 5
  4. 4. 2. Problem Statement……………….…...…………………………………………………………………53. Theory...……….………..………………………………………………………….….…..……...…...… 64. Calculation and Simulation…….….………..………..…………...………..…………………………..... 85.Results……………………………………………………………………………………………………95. Conclusion...…………………………………………………………………………….…..…………. 10
  5. 5. AbstractPower dividers (also power splitters and, when used in reverse, powercombiners) are passive devices used in the field of radio technology. Theycouple a defined amount of the electromagnetic power in a transmission line toanother port where it can be used in another circuit. Directional couplers andpower dividers have many applications, these include; providing a signalsample for measurement or monitoring, feedback, combining feeds to and fromantennas, antenna beam forming, providing taps for cable distributed systemssuch as cable TV, and separating transmitted and received signals on telephonelines. The Wilkinson divider splitter / Wilkinson combiner is a form of powersplitter / power combiner that is often used in microwave applications. It usesquarter wave transformers, which are easily fabricated as quarter wave lines onprinted circuit boards and as a result it offers the possibility of proving a verycheap and simple splitter / divider / combiner while still providing high levelsof performance.
  6. 6. Introduction
  7. 7. With The Rapid Development in wireless/wireline communications, their functions arefurther enhanced, and the applications are also broadened. For industrial systems,however, circuits/devices with much more stringent requirements are suffering fromthe system cost, compactness, stability, reliability, and other specifications , ascompared with those systems like consumer electronics. It is known that any wireless /wireline (RF) system is generally composed of passive and active circuits . Amongvarious RF passive circuits, Wilkinson power divider is a basic and importantcomponent in application to RF power amplifiers, mixers, phased-array antennas, andmany kinds of equipment. Problem StatementDesign of Equal -Split Wilkinson power divider of Frequency 2.4 GHz.Specifications are:1. Source Impedance = 50 ohms.2. Load Impedance = 50 ohms3. Substrate permittivity = 3.384. Thickness of substrate = 1.524 mm5. Thickness of conductor = 0.15 mmSimulate the circuit of Equal -Split Wilkinson power divider and plot the graphs ofvariousS parameters.
  8. 8. TheoryThe mostly used one is the three port network equal two way divider. It isalso called 3 dB power divider.In this type of dividers, there are four different sections.1-) Input port2-) Quarter-wave transformers3-) Isolation resistors4-) Output portsInput and output ports are identical and the value of the impedances ofthem are Zo. Quarterwave transformer parts are called as quarter-wavetransformer because of the length of these parts. The length of these partsare equal to the one fourth of the wavelength of the electromagnetic wave,which is propagating in this three port network. This length is also related tothe operation frequency.Wavelength * Frequency = Phase velocity (Usually the speed of light)
  9. 9. Why the quarter-wave transformers are used in the circuit? The reason forthis leads us to understand the matching conditions for this network.Matching of the output ports is necessary for the better power transfer frominput to output, because if the output ports are matched, the reflectedpower from the network when we input some amount of power is zero. Thismeans, there is no reflection from the outputs and all of the power istransmitted to the output ports. Consider the case of inputing power at port1 and terminate the ports 2 and 3 with the reference loads. Then thereflected power for inputing power at port-1 is zero ( S11 = 0 ). All thepower is transferred at that frequency. The quarter-wave transformer partleads to the matched ports. Isolation resistor is to isolate the output ports. Ifthere is a coupling effect between output ports or in other words, the powercomes from one output port has an effect on other output port, the perfectdivision of the power cannot be possible. This isolation resistor avoids thecouplingeffects of the output ports. Output ports are the ports that divided powercomes to. These ports have the same impedance value with the input portsimpedance.To analyze the Wilkinson power divider, even-odd mode analysis method isused. In even-odd mode analysis the aim is finding the S-parameters of thedivider. S-parameters give all voltage and power information about thenetwork we consider. To find S-parameters, from the definition of them, weshould input power at a port and measure the contributions of that power tothe other ports. In even-odd mode analysis, the superposition of the twomodes is inputing power at port-2 and finding the effects at all ports. Firstof all our circuit becomes symmetric, made symmetric with respect to theaxis at the middle. This symmetricity makes the analyze easy. An ideal half-split power divider would divide incident power at port 1 equally betweenports 2 and 3. The S-matrix for the ideal Wilkinson divider is given below:
  10. 10. This ideal Wilkinson power divider would have perfect matching at all ports (S11= 0, S22 = 0,S33=0). Also, there would be perfect isolation between ports 2 and 3 (S23 = 0).The insertion loss between ports 1 and 2 should be 1/√2 , and the insertionloss between ports 1 and 3 should be 1/√2 (|S12| = |S13| = 1/√2 ). Even-oddmode analysis can be used to derive the proper three-port circuit to use tocreate the ideal Wilkinson power divider. The results are shown below, in Figure1.For this project, Z0 is 50 Ω and f = 2.4 GHz. This results in the following groupof idealvalues at λ/4, presented in Table 1:
  11. 11. Calculation and SimulationThese values were used as the first-cut microstrip design in ADS . Thesevalues were thenconverted to microstrip line values using LINECALC. These resultingmicrostrip widths andlengths were used in generating the layout for the circuit. After severalrounds of tweakingthe circuit, the following schematic was generated.1.Calculation of Width and Length of MicrostripBased on the specification given in the problem statement, width and length ofthe microstriplines are calculated. According to it – Zo = 50 Ohm, Frequency, fo = 2.4 GHz Substrate Permittivity, ɛ r = 3.38 Thickness of Substrate, d = 1.524 mm Thickness of Conductor = 0.15 mm
  12. 12. ADS provides a LineCalc utility to calculate the width, w and length, l in mils accordingto your specifications. Using LineCalc:For Zo=50 Ohm, at λ/4 W=3.37 mm, L= 19.19mmFor Z= √2Zo=70.71 Ohm at λ/4 W= 1.56mm, L=19.86 mm2.Schematic Design Figure 2 : Simulation CircuitThis schematic was then converted into a layout, and the final layout ispresented below, inFigure 3.
  13. 13. Figure 3 : Layout ResultsThe circuit’s three main S-parameters were plotted S11 ,S12,S23 and S31.These indicatematching, power division, and port isolation, respectively. m1 freq= 2.466GHz dB(S(2,1))=-3.042 0 m1 -5 dB(S(3,1)) dB(S(2,1)) dB(S(1,1)) -10 -15 -20 -25 1.0 1.5 2.0 2.5 3.0 3.5 4.0 freq, GHz
  14. 14. Conclusion:The schematic of equal split Wilkinson power divider was drawn and the layoutwas generated.The results of the project were in agreement to the theoretical available results,so the various S parameters were plotted as shown above.

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