• CST LAB 20th Jan
  • Decibel Scale
  • Reflection and transmission coefficients
  • Design a receiving antenna - Microstrip Patch Antenna
• CST LAB 27th Jan
  • Waveguide
  • Cutoff frequency depends on
  • CST simulation:
  • Plot the following results
• CST LAB 3rd Feb
  • Filters
  • Step Impedance Resonator
  • Assignment
• CST ViVa Questions
• LabView ViVa Questions

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CST LAB 20th Jan

Decibel Scale

Non Linear scale
How to convert simple scale to decibel scale ?

Reflection and transmission coefficients

S12, S21 formula

S11 : should be low (reflection coeff less than -10)
S21 : approx 0 (transmission coeff less than -3)

S11 should be above 10 (in magnitude)
S21 should be below 3 degree (in magnitude)

$$Reflectio{n}_{-}coeff=\frac{Energ{y}_{-}reflected}{Energ{y}_{-}incident}$$

$$Transmissio{n}_{-}coeff=\frac{Energ{y}_{-}transmitted}{Energ{y}_{-}incident}$$

Design a receiving antenna - Microstrip Patch Antenna

Frequency inversely proportional to wavelength (for free space)
h : ht of substrate
w : width for 50ohm corresponding line
Single port only S11 will be observed

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CST LAB 27th Jan

Optical fibre works on principle of Total Internal Reflection

Waveguide

Can be hollow or filled with dielectric, by this way we can control conducitivty of medium.
Waveguide acts as high pass filter

OFC Cables : Core + Clad

Different modes TEM

• T : Transverse
• E : Electric
• M : Magnetic

TE 10 : 1 => Half Sinusoidal (fundamental mode)

Magnetic field is perpendicular to the Electric Field.

TE 01 : Bidirectional (along yaxis)

m : No of modes
n : No of modes

Cutoff frequency depends on

1. mn
2. dimensions of waveguide (a,b) (transverse dimensions)
3. relative permittivity and permeability

EM wave does not enter waveguide (when we operate at lower frequency)

Electric field component in direction of propogation is zero.
For example if the wave is moving in z direction, E_z=0)

CST simulation:

Design waveguide in TE mode TM mode
TE 10 ( 0 to pi of sinx graph )

S21 : Shows Transmission (from port 2 to port 1)
S12 : Shows Transmission (from port 1 to port 2)

Calculate a, b, fr
What if we change the face chosen by 90degrees ?

Plot the following results

1. E-field
2. H-field
3. Surface Current
4. Power
5. Port Signal (input to output)
6. S11 graph

Maybe TE01 TE11 TH11
Next up : RF Filter

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CST LAB 3rd Feb

Lab opens at 9:40
Lab starts at 9:50

Filters

RF Filter
Types of Filter
Low pass, High pass, Band pass, Band stop

High impedance, Narrow width condutance
Low impedance broad width capacitor

Step Impedance Resonator

First layer : ground then microstrip line (1.5mm height), third layer 50ohm, then inductance, then capacitance at center,

Height of substrate : 1.5mm
Di-electric constant FR4 : 4.5

Assignment

Frequency 1GHz to 11GHz
Material : FR4 3.55, 0.5 0.8
ROgers RT 5880 0.5 1.5
Rogers RO
thickness =2mm

Roll No. Frequency Material Height
R1 1GHz FR4 0.5
R2 1GHz FR4 1.5
R3 1GHz RT 0.5
R4 1GHz RT 1.5

100,20 Z high low impedance

AIM
Calculation
Graph photo
Design photo

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CST ViVa Questions

Q1. Fullform of CST
Q2. What are filters ?
Q3. Why do we use CST ?
Q4. What is a waveguide ? Use of waveguide ?
Q5. What is mesh size ? For a PC with low RAM, should we increase or decrease the mesh size ?

LabView ViVa Questions

Q1. Fullform of LabView
Laboratory Virtual Instrument Engineering Workbench

Q2. When to use for loop, when to use while loop, which experiments used while loop.
Q3. Difference between while and for loop.
Q4. Name 10 components used in LabView

1. Filters
2. Simulate Signal
3. Numeric Constants
4. Graph Indicator
5. Mathematical constants
6. Case structures (for while loop)
7. Boolean
8. String
9. Array operations