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Microwave Calculatorcalcufrnd

Chinmoy Saha Anjan Debnath Soumya Banerjee Soumyajit Gupta Heritage Institute of Technology

ECE Department [email protected] [email protected] [email protected] [email protected]

Abstract According to IEEE, microwaves are EM waves in the frequency range of 3 to 30 GHz. But in practice, the frequency range is from 1 GHz to 300 GHz (30 cm to1mm). However, microwave really indicates thewavelengths in the micron ranges. This meansmicrowave

frequencies are up to infrared and visible light regions.They have a myriad of applications in communication.

Due to their short wavelengths, small and realisableantennas can be used now-a-days. Moreover, since thelower frequency spectrum is overcrowded, the use of microwaves is becoming more and more important today.

Key Words:Microwave,Waveguide,Resonator,Antenna,TransmissionLine,Tee,Wave Propagation

1. Introduction

μCAL is a microwave calculator developed in VisualBasic and uses HFSS for animated images of microwavestructures in action. It calculates the design parameters

based on the specification inputs. Waveguide,Transmission Line, Antenna, Devices and Propagationhave been included.

Using μCAL, we can get parameters to which will aidin the design of these devices and structures. We've alsoincorporated animated pictures that will illustrate allthese structures making it easier to visualise their working.

1.1.Waveguides

Both waveguide and transmission line can be used toguide EM energy from one point (generator) to another (load). However there are subtle differences betweenthem. case of the former. In the first place, atransmission line can support only a transverseelectromagnetic (TEM)

wave, whereas a waveguide can support many possiblefield configurations. Second, at microwave frequencies(roughly 3-300 GHz), transmission lines becomeinefficient due to skin effect and dielectric losses;waveguides are used at that range of frequencies toobtain larger bandwidth and lower signal attenuation.Moreover, a transmission line may operate from dc (f =0) to a very high frequency; a waveguide can operate

only above a certain frequency called the cutoff frequency and therefore acts as a high-pass filter. Thus,waveguides cannot transmit dc, and they becomeexcessively large at frequencies below microwavefrequencies.

Although a waveguide may assume any arbitrary butuniform cross section, common waveguides are either rectangular or circular.

1.2. Cavity Resonator

Resonators are primarily used to store energy. At highfrequencies (100 MHz above) the RLC elements areinefficient when used as resonators because the circuitsize becomes excessively large. Therefore at highfrequencies RLC resonant circuits are replaced by cavityresonators.

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A cavity resonator is a metallic enclosure thatconfines the electromagnetic energy. The stored electricand magnetic energies inside the cavity determine itsequivalent inductance and capacitance. The energydissipated by the finite conductivity of the cavity wallsdetermines its equivalent resistance. In practice, therectangular-cavity resonator and circular-cavity

resonator are commonly used in many microwave applications.

The only difference between the structures of waveguides and cavity resonators are the open waveportsare absent in cavity resonators, unlike waveguides.

1.3. Antenna

The IEEE Standard Definitions of Terms for Antennas defines the antenna as “a means for radiatingor receiving radio waves.”[Bal] In other words, antennais a n impedance matching structure between free-spaceand a

radiating source, as shown in Figure 1[Bal] .To achieve maximum power transfer,the antenna

performs the matching of system impedance with theimpedance of the ambiance to which the radiation isreleased.

Radiation is basically the phenomenon of inability of a structure to sustain energy,released duringelectronic transition from high energy orbits to lowenergy orbits, within itself and the capability of sharingthis energy with the surrounding medium.

What makes radiation to occur is charge motion

through a curve,bend,discontinuity of any type or asudden termination etc. that makes the charge to undergoacceleration or deceleration; which acts as forbinger of radiation. Application of time harmonic alternatingexcitation does the purpose.

1.4. Transmission LineTransmission line is one of the most important

guided media for distribution of power (at low

frequencies) or for communication (at high frequencies).Different types of transmission lines in use today aretwisted pair cable, co-axial cable, two-wire line, planar line, microstrip line etc.

Twisted pair cables and co-axial cables are usedin Ethernet technology in Computer Networks (Thicknet,Thinnet, or 10BaseT). Co-axial cables, two-wire line,

planar line, microstrip lines are commonly used now-a-days for power distribution and data communication.

Transmission lines consist of one or two sets of conductors, upon a layer of the substrate, which is adielectric material. On the other side of this substrate, wehave another layer of conductor, which acts as ground,and hence as a reference with respect to the signalcarried by the opposite conductor.

Transmission line characteristics depend uponResistance per unit length (R), Inductance per unit length(L), Conductance per unit length (G), and Capacitance

per unit length (C), which, in turn, depends upon parameters such as length, breadth, diameter of the wire,

conductivity, permittivity, permeability etc. of thesubstrate dividing the conductor and the ground, and theconductor. It must be noted that these R, L, G, C

parameters, are not lumped parameters, rather they aredistributed parameters.

Figure 2 [sadik]shows the R,L,G,C parameters of atwo wire transmission line.

1.5. Waveguide TeeIn microwave circuits, a waveguide or

coaxial-line junction with three ports is commonlyreferred to as a tee junction.It is a device meant for signal division or unification with phase characteristicsgoverned by the geometry of the device. From the S-

parameter theory of a microwave junction it is evidentthat a tee junction should be characterized by a matrix of third order containing nine elements, six of which should

be independent.An E-plane tee is a waveguide tee in which the axis

of its side arm is parallel to the E field of the main guide.When the waves are fed into the side arm (port 3), thewaves appearing at port 1 and port 2 of the collinear armwill be in opposite phase and in the same magnitude.

Figure 2: Distributed parameters of a two wiretransmission line

Figure 1: Antenna as a transitional device



An H-plane tee is a waveguide tee in which the axisof its side arm is “shunting” the E field or parallel to theH field of the main guide. If two input waves are fed into

port 1 and port 2 of the collinear arm, the output wave at port 3 will be in phase and additive. On the other hand, if the input is fed into port 3, the wave will split equallyinto port 1 and port 2 in phase and in the same

magnitude.A magic tee is a combination of the E-plane tee and

H-plane tee. The magic tee is commonly used for mixing, duplexing and impedance measurements.

1.6. Microwave Propagation

Fundamentally the microwave communication in freespace can be classified into there categories-

1.Line of Sight communication, which is the directcommunication between two antennas, situated somedistance apart on the earth surface and they have a lineof sight between them.

2.Ionospheric propagation, which is used for longdistance communication. It depends upon the reflectingcharacteristics of Ionosphere.

3.Satellite communication, which is also used for long distance communication. The artificial satellites areused as transponders, which perform the function of frequency translation between uplink and downlink frequencies alongwith reflecting uplink frequencies todownlink.

2. Motivation

This software will be useful to both students andengineers. The students, who has studied waveguides

and cavity resonators, often have difficulties, visualizingthe variations of E-fields and H-fields in differentmodes. The package includes animated diagrams of thefield variations in different modes, which will help thestudents to visualize the concepts. Also they can be ableto solve different numerical problems by providing thesystem specifications to the software.

The engineers also have tasks of designing thedifferent devices such as waveguides, antennas etc. Theycan get the required parameters from the software whenthey provide the system specifications.

3. Implementation of System

The software has two distinct functional parts, one part is the calculation of parameters from the givenspecifications. Another part is the pictorial part, wherethe simulated pictures of the system is shown.

3.1. Development

Visual Basic 6.0 was used to develop the overallgraphical user interface, as well as, for calculating the

parameters from the required specifications.High Frequency Structure Simulator (HFSS) was used

to draw the simulated diagrams of the correspondingsystems.

3.2. Working

At the first interactive menu, there is a provision for using username and password, in order to make sureunauthorized people can't use the software. Once this has

been cleared, the main page for selecting the differentdevices comes.

At this window, one can select the required device frocalculation of parameters. Figure 3 shows the differenttypes of devices present.

For both Waveguide and Cavity Resonator, they aredivided into two types, Rectangular and Circular. Whenthe length, breath or radius if the waveguide is inputalong with the operating frequency, and the relative

permittivity, the different Electric and Magnetic fieldcomponents are calculated. Among other parameters,one can calculate guide frequency, phase velocity, groupvelocity, intrinsic wave impedance, Q factor (for thecavity resonator) and other parameters. The softwarealso displays the electric and magnetic field variations inall the directions for a particular mode selected.

<Attach a still b/w pic of HFSS simulation and provide the correct FIG#>

The different antennas included in the software are patch, horn, log periodic, helical, small dipole and loop.

For patch antenna, one needs to first select what kindof a patch it is, whether it is rectangular, circular or triangular. Then when the substrate properties are inputalong with the dimensions of the patch, one can calculatethe resonant frequency for the antenna. Click on thewaveform button to see the electric field distributionwhen the antenna is radiating.

Figure 3: Different types of devices present in thesoftware



For Horn antenna, provide the input whether theantenna is sectoral E plane, sectoral H plane or Pyramidal. Then provide the dimensions and operatingwavelength to get outputs such as HPBW for both E & H

planes, Directivity and Power Gain. Click on thewaveform button to watch the E field distribution in thehorn antenna.

For Helical antenna, we are taking as input thenumber of turns in the antenna, spacing between eachturn, diameter of the helix, and the wavelength of thesignal used. Once these have been inputted, click on the“Calculate” button. The software provides as output, thetotal length of antenna, total length of wire, pitch angle,HPBW, FNBW, Axial ratio and directivity of antenna.

For Dipole antenna, the input parameters are lengthof the antenna and the wavelength of the signal. Theoutputs provided here are radiation resistance, effectivearea of the antenna, HPBW, directivity, and waveimpedance.

For Loop antenna, the different input parameters areradius of the antenna and wavelength of the signal. Thenclick on “Calculate” button to calculate the various

parameters. We get effective area of the antenna,radiation resistance, circumference of the antenna,direcivity, HPBW as outputs.

There are four types of Transmission Lines includedin the software, namely Co-axial, Two-wire, Planar andMicro-strip.

For Co-axial, Two-wire, & Planar lines, we take theinputs the dimensions of the wire, conductor conductivity, medium conductivity, relative permittivityand permeabilities of the conductor and the di-electricmedium. Once they have been inputted, click on“Calculate”. The software calculates R,L,G, C for the

lines, attenuation and propagation constants,characteristic impedance, reflection coefficient andVSWR of the transmission lines.

For Micro-strip line, we have provided features for shielded strip line, micro-strip, and parallel strip line.Here we take inputs of the dimensions of thetransmission lines such as width of strip, thickness of substrate & strip line, relative permittivity and

permeability of the substrate. Then, click on “Calculate”.As output, the software provides the correspondingcharacteristic impedances.

The different features available under the waveguidetee section are the S-parameters of different waveguidetees, as well as the waveforms of the different tees.

Select the type of Tee to be used and it shows thediagram & S-parameter of the same. Then click on“Waveform” to generate the corresponding waveform.

In the wave propagation section, three features areincluded, they are Ionospheric propagation, Line-of-sight

propagation and Satellite communication.In Ionospheric Propagation, we have calculated

parameters such as MUF, Critical Frequency, SkipDistance, etc from inputs such as Maximum IonicConcentration, Operating frequency etc. In Line if Sight

Propagation, we have calculated parameters such ascalculation of Radio horizon, and also we haveimplemented the Friis Transmission Formula. In theSatellite Propagation option, we have implementedorbital characteristics such as orbital velocity, orbital

period from the orbital radius. In the communication part, we have calculated the path loss, C/No (depending

upon temperature) receiving antenna gain & received power.

8.1.1. Third-order headings. Third-order headings, asin this paragraph, are discouraged. However, if you mustuse them, use 10-point Times, boldface, initiallycapitalized, flush left, preceded by one blank line,followed by a period and your text on the same line.

9. Printing your paper

Print your properly-formatted text on high-quality,

8.5 x 11-inch white printer paper. A4 paper is alsoacceptable, but please leave the extra 0.5 inch (1.27 cm)at the BOTTOM of the page. If the last page of your

paper is only partially filled, arrange the columns so thatthey are evenly balanced if possible, rather than havingone long column.

10. Page numbering

Number your pages lightly, in pencil, on the upper right-hand corners of the BACKS of the pages (for example, 1/6, 2/6; or 1 of 6, 2 of 6; and so forth). Pleasedo NOT write on the fronts of the pages, nor on thelower halves of the backs of the pages. Do not

automatically paginate your pages. Note thatunnumbered pages that get out of order can be verydifficult to put back in order!

11. Illustrations, graphs, and photographs

All graphics should be centered. Your artwork must be in place in the article (preferably printed as part of thetext rather than pasted up). If you are using photographsand are able to have halftones made at a print shop, use a100- or 110-line screen. If you must use photos, theymust be pasted onto your manuscript. Use rubber cementto affix the halftones or photos in place. Black and

white, clear, glossy-finish photos are preferable to color.Supply the best quality photographs and illustrations possible. Penciled lines and very fine lines do notreproduce well. Remember, the quality of the book cannot be better than the originals provided. Do not usetape on your pages!

11.1. Color images in proceedings



The use of color on interior pages (that is, pages other than the cover of the proceedings) is prohibitivelyexpensive. Interior pages may be published in color onlywhen it is specifically requested and budgeted for by theauthors. DO NOT SUBMIT COLOR IMAGES INYOUR PAPER UNLESS SPECIFICALLYINSTRUCTED TO DO SO.

11.2. Symbols

If your word processor or typewriter cannot produceGreek letters, mathematical symbols, or other graphicalelements, please use pressure-sensitive (self-adhesive)rub-on symbols or letters (available in most stationerystores, art stores, or graphics shops).

11.3. Footnotes

Use footnotes sparingly (or not at all!) and place themat the bottom of the column on the page on which they

are referenced. Use Times 8-point type, single-spaced.To help your readers, avoid using footnotes altogether and include necessary peripheral observations in the text(within parentheses, if you prefer, as in this sentence).

12. References

List and number all bibliographical references in 9- point Times, single-spaced, at the end of your paper.When referenced in the text, enclose the citation number in square brackets, for example [1]. Where appropriate,include the name(s) of editors of referenced books.

[1]RameshGarg,PrakashBhartia,InderBahl,Apisak

Ittipiboon,Microstrip Antenna design Handbook,ArtechHouse,Boston,London[2] David.M.Pozar,Microwave Engineering,John Wiley&sons,Inc;NewYork.Chichester.Weinheim.Brisbane>Singapore.[3]ConstantineA.Balanis,Antenna Theory:Analysis anddesign,Wileyinterscience,JohnWiley&Sons,Inc.Hoboken,New Jersey[4]ConstantineA.Balanis,ModernAntennaHandbook,JohnWiley&Sons,Inc.Hoboken,New Jersey&Canada[5]ConstantineA.Balanis,PanyiotisI.Ioannides,IntroductiontosmartAntennas,MorganandClaypoolPublishers,UnitedStatesofAmerica[6]JRJames&PSHall,HandbookOfMicrostripAntennas,Pe

terPersgrinusLtd.onbehalfoftheIEE,London,UnitedKingdom.[7]NMarcuvitz,WaveguideHandbook,PeterPersgrinusLtd.onbehalfoftheIEE,London,UnitedKingdom.[8]PrakashBhartia,InderBahl,MicrowaveSolidStateCircuitDesign,JohnWiley&Sons,Inc.Hoboken,NewJersey&Canada.[12]Y.T.Lo,S.W.Lee,AntennaHandbook:FundamentalsAndMathematicalTechniques,Chapman&Hall,NewYork,NY

[13]Abramowitz, M. and I.A. Stegun, Handbook of Mathematical Functions, National Bureau of Standards,Applied Math. Series #55, Dover Publications, 1965,[14]Matthew N.O.Sadiku

13. Copyright forms and reprint orders

You must include your signed copyright release formthat will be available in Author's Package when yousubmit your finished paper. We MUST have this form

before your paper can be published in the proceedings.

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