QUCS Installation and Usage

QUCS Installation and Usage (LAB 0)

• QUCS (Quite Universal Circuit Simulator) installation is detailed for Windows
• QUCS can be installed from the provided SourceForge link
• To launch, search "QUCS" in the Start menu and click the QUCS icon, or find "qucs.exe" in the installation directory
• Creating a QUCS Project involves opening QUCS, navigating to File > New > Project, selecting a name/location, setting the project type to Schematic, and clicking OK
• QUCS Project files are saved with the ".sch" extension
• The Components library contains circuit elements like resistors, capacitors, and voltage sources
• Components are added by dragging them onto the schematic editor
• The Wire tool connects components
• The Ground symbol from the library is used to ground circuits
• Simulation settings are accessed via Simulate > Simulation Settings, where the simulation type (e.g., Transient, AC, DC) and parameters are set
• Simulating is done through Simulate > Run Simulation
• QUCS will simulate the circuit and subsequently create a ".dpl" file
• Errors or warnings should be inspected in the .dpl file, fixed, and the simulation re-run
• Results plotting is available under Diagrams, where the plot type (e.g., Cartesian Plot) and X/Y axes are configured

Simple Transmission Line in the Time Domain (LAB 1)

• A circuit composed of a voltage generator, transmission line and load resistor is used
• A Voltage Pulse source is selected, and its parameters are configured
• The pulse width is set to 1 ms for step function response investigation
• A transmission line component is selected
• A load resistor is placed
• Transient simulation parameters are adjusted and final time and time step are configured appropriately
• V1 and V2 markers are attached to the transmission line's input and output ports
• Traces V1.Vt and V2.Vt are selected for plotting
• Waveform cursors can be used to find where the step is detected
• Using a 1m line, the velocity of propagation is Vp = 1/ (3.3 x 10 -9 ) = 3 x 10 8 m/s
• RG-58 coaxial cable is modeled, the velocity factor is set to 0.66c
• Velocity factor (VF) is the ratio of a waves speed through a medium to the speed of light in a vacuum
• Incorporate the equation into the schematic
• Alter the lines physical length to 'trueL'
• Equivalent length is put into the transmission components length property
• A 1m line introduces a 5ns delay, corresponding to a 0.66c propagation velocity

RF Circuit Design with QUCS (LAB 2)

• A circuit with two power sources and a transmission line is drawn
• Power sources are selected and adjusted
• The transmission line component is placed between the power sources
• The S parameter simulation is performed by adjusting its parameters
• Time and time step are set
• It should be simulated error free
• Graph S[1,1] in linear scale is drawn using Cartesian plot
• The output needs to be displayed in dB by using the insert equation option
• Graph dBS11 is drawn
• In Edit properites, the values need to be changed
• The Smith chart needs to be drawn and the output observed
• The S[1,1] & Z[1,1] values are observed by attaching markers
• Change the impedance value to make an unmatched impedance
• The port parameters with matched and unmatched impedance are observed
• Cartesian plot and Smith chart are plotted for graph for S[1,1], S[1,2], S[2,1], and S[2,2] by taking suitable limits

Matching Circuit Design (LAB 3)

• A circuit composed of two power sources and a transmission line is designed
• Power sources are selected and adjusted
• The Transmission line is placed
• An S-parameter simulation is ran
• A dBsll equations are added
• dBSll is plotted for each of the cases and tabulated for different frequencies

E-H Field Pattern Plot for Rectangular Waveguide (LAB 4)

• Uses MATLAB for rectangular waveguide TEmn and TMmn mode E-H field pattern plot
• clc, close all commands used to clear command window and close open figures
• The waveguide dimensions and constants are defined
  • a = 2.286cm (x-direction length)
  • b = a/2 cm (y-direction length)
  • f = 45 GHz (frequency)
  • c = 3e8 m/s (light speed)
• The mode of choice selection prompts the user to choose either TE or TM
• Specific mode values should be input
• When an incorrect choice is made a "wrong choice" message will appear
• Wave propagation parameters and calculations for Z-direction
  • fc is calculated
  • Wavelength and constants for permittivity and permeabiliy set
• If TE is chosen and m and n are 0, returns "Does not exited"
• If the cut off frequency is higher than frequency of use then the operation cannot work and returns a statement on operation and cut off frequencies
• Field expression for TEmn calculation
• Quiver will plot the E-field, H-field and E-H field on the from, top and side view
• An elif statement contains information for if choice is not 1 i.e. must be 2
• TM or transverse magnetic mode has similar cut of conditions applied
• The field of TMmn or transverse magnetic mode is calculated, and then Quiver will plot the E-field, H-field and E-H field on the from, top and side view

Rectangular Waveguide Analysis with CST (LAB 5)

• It is analyzed using CST simulator.
• set the frequency to 8-12 GHz
• A rectangular will be drawn
• The material (Alumina 99.5% (loss free))
• The waveguide will be hollowd by drawing a smaller matric inside the waveguide
• Ports are connected to the design
• Double click on the edges
• E field (V/m), H field (A/m) values for every frequency (8 – 12 GHz) are noted down
• Radiation pattern is viewied in the in far field view in 3D

CST Antenna Analysis: Monopole and Dipole (LAB 6)

• It familiarizes the user with CST Software for both Monopole and Dipole analysis
• For Monopole length of the wire, frequency, and calculating the length is shown
• The Monopole frequency is 2.4GHz
• Simulation template, creating cilinders and groundplanm and subraction modelling is shown
• The value of S-parameters and VSWR are taken down
• The direction, E-Field and H-field are found
• The Dipole parameters are found which include Center frequency,Dipole length,Wire Diameter and Feed Gap
• A new template needs to be opened and the range of frequency needs to be set
• Orientation set on Z
• Vacuum is the material
• Clicks pick edges
• Tetrahedral is set
• the solver starts

Dipole Antenna MATLAB Implementation (LAB 7 & 8)

• It is found via MATLAB implementation to produce both the field pattern and power pattern, where the values of wavelength, dipole length, and current are entered
• Polar plots are used to represent the data

Typical Antenna System Radiation Pattern and Beam Width in MATLAB (LAB 9)

• It is implemented via MATLAB to work out the radiation pattern of a typical antenna system and find the half-power beam width and first null beam width
• The normalized radiation intensity uses U (0)=cos²(0).cos² (30), 0≤0≤90° 0≤≤360°. Where a program to plot can find half power beam width and first null beam width

Key Information:

• Calculation to calculate power radiated
• How to call HPBW

Radiation Pattern, Directivity, Kraus, and Tai & Pereira (LAB 10)

• MATLAB is implementing to obtain the radiation pattern of a typical antenna systems
• It compares the Exact and approximate values of maximum directivity using Kraus and Tai & Pereira for U (Θ) with N varying from 1 to 2
• The key equation is represented is; THE NORMALIZED RADIATION INTENSITY OF AN ANTENNA IS REPRESENTED U
• When finding HPBW

Co/Cross-Polarization of a Sectoral Antenna (LAB 11)

• Explore co/cross-polarization concept in sectoral antenna
• Objective: Determine polarization of antenna.
• Components: KPS, RKO, VSWR meter, detector, sectoral horn.
• Block diagram illustrates setup.
• Theory:
  • Polarization is a key antenna characteristic.
  • Plane electromagnetic waves travel in one direction with perpendicular electric and magnetic fields.
  • Linear polarization doesn't require alignment with horizontal or vertical axes.
  • Elliptical polarization occurs when E field components are 90° out of phase with unequal magnitudes.
  • Antenna polarization is the polarization of radiated fields in the far field.
• Procedures:
  • Set KPS to 3/4th mode for maximum amplitude at 0°.
  • Record amplitude in CRO or VSWR meter.
  • Connect sectoral horn in E plane to diode detector and VSWR meter.
  • Rotate sectoral horn from 0° to 360° in 20° steps, noting dB values in VSWR meter.
  • Change sectoral horn to H plane, noting dB values in VSWR meter from 0° to 360°. Polarization pattern needs to be ploted which show different angles and values against decibels

Gain Measurement by Substitution (LAB 12)

• The aim is measuring antenna gain the substitution method
• Components: KPS, RKO, VSWR meter, frequency meter, standard/test antennas.
• Block diagram illustrates the setup.
• Theory:
  • Peak gain can be measured with the Friis transmission equation and a standard antenna.
  • Gain standard antennas have known gain and polarization (typically linear).
  • Common types: thin half-wave dipole (2.15 dB peak gain), pyramidal horn (15-25 dB peak gain).
  • Standard antenna replaces test antenna for fixed power transmission.
• Friis equation: PR = PT GT Gr λ2 / (4ΠR)2
• Gain of the test antenna: GT = GR2 PR2 / PR
• Gain in decibels: [GT]dB = [GR]dB + 10log10(PR2 / PR)
• Procedure:
  • Use matching and different transmitting antennas
  • Initial setup with standard gain antennas for both TX/RX
  • Set TX antenna to transmit defined output
  • Measure received power (RX) with the same angel
  • Rotate antenna to certain degrees and measure the received power
  • Find the peak by repeating these actions
  • Replace the TX antenna with a RX antenna for step 6 onwards

Radiation Pattern Study of End Fire and Broad-Side Arrays (LAB 13)

• Study and plot End fire/Broad-side array radiation patterns using MATLAB
• MATLAB implementation to obtain the radiation pattern for a planar array
• Definition of End Fire Array: Array with max radiation in direction of array line (0° & 180°)
• Definition of Broad-Side Array: phase angle makes max perpendicular to line of array, which is usually measured at 90°& 270°
• Equation is input and it is ploted and found