Course: BEng (Hons) in Electrical and Electronic Engienering

1. EEEC6430310
Electromagnetic Fields and Waves
Faculty of Engineering and Computer Technology
Laboratory Manual
Lecturer: Ravandran Muttiah BEng (Hons) MSc MIET
Year/Semester: Year 2 / Semester 1
Academic Session: 2020/2021
The information in this documentis important and should be noted by all students undertaking the
Bachelor of Engineering (Honours) in Electrical and Electronic Engineering
Approved by Coordinator: Endorsed By Dean:
------------------------------------------ __________________

2. AIMST University Faculty of Engineering and Computer Technology
BEng (Hons) in Electrical and Electronic Engineering Electromagnetic Fields and Waves 1
𝑍L
Mini Project 2 - Impedance Matching With A Double Stub Tuner
Theory
In some instances, the distance determined for the single stub tuner may not be
convenient for implementation. In those cases, a double stub tuner may be required as
shown in figure 1. In designing double stub tuners, the distances 𝑑stub1 and 𝑑stub2 are
pre-determined by the designer.
A double stub transmission line impedance matching network is composed of two short
circuited sections of transmission line, separated by a length of transmission line, placed
along the main signal line. The short circuited sections provides an equivalent shunt
susceptance. The short circuited sections are attached perpendicular to the main line as
shown in figure 1. The construction of the short circuited section is similar to the main
line.
The load impedance is typically dependent on the frequency of operation. The distance,
𝐿stub1 , can be moved back and forth to get a wide range of susceptance values. The
distance 𝐿stub1 and 𝐿stub2 can be found in terms of fractions of wavelength of the signal
being transmitted using a Smith chart.
The values of the lumped parameter components can be calculated using the susceptances
determined from the Smith chart.
Figure 1: Double stub short circuit tuner
𝑍o
𝐿stub1
𝐿stub2
𝑑stub1
𝑑stub2

3. AIMST University Faculty of Engineering and Computer Technology
BEng (Hons) in Electrical and Electronic Engineering Electromagnetic Fields and Waves 2
Objectives
The objective of this experiment is to become acquainted with double stub impedance
matching. Demonstrate your ability to design and construct the double stub tuner and to
view the function of the matching stub. The stub tuner transmission line impedance
matching networks are designed given load components at specified frequencies.
Specification
Design a Double Stub Tuner
Design a 50 Ω microstripline double stub transmission line impedance matching network
to match a 50 Ω source and line to a load with a resistance 𝑅 = 25 Ω in series with a
capacitance, 𝐶 = 33 pF. Let the distance between the load to the stub closest to stub be
𝑑stub1 = 0.250 λ and the short circuit stub length closest to the load be 𝐿stub1 = 0.204 λ.
The relative permittivity of the G-10 printed circuit board is 𝜀r = 4.5. Metal thicknesses
of 1.37 mm are typically for 1 oz copper plating. Use a Smith chart to design the
matching network at 965 MHz. Verify the matching network at 965 MHz using Agilent
ADS software package. How reasobale will the match be at 500 MHz ? Plot 𝑆11 in both
rectangular and Smith chart formats as well as the Standing Wave Ratio (SWR).
Replace the Stubs With Lumped Parameter Passive Components
Re-design the matching network by replacing the stubs with lumped parameter passive
components (i.e. inductor and capacitor).
Measure the Impedance Matched Networked
Verify the re-designed network at 965 MHz using the Agilent ADS software package.
How reasonable will the match be at 500 MHz ? Plot 𝑆11 in both rectangular and Smith
chart formats as well as the SWR. Compare the results of double stub of microstripline
and passive components.
Report
Write a laboratory report on this project.
(1) Explain in detail about the theory of double stub tuner for the designed impedance
matching circuit with the theoretical calculations of component values.
(2) Discuss the method of productions and fabrications of double stub tuners, and
comment on the test results.
(3) Prepare slides for presentation and demonstration of this project.