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ECS644U/ECS752P
Microwave & Millimetrewave Electronics
Assignment 4: Antennas Lab Measurements & Amplifiers
Requirements
Software: CST Studio Suite
Hardware: Vector Network Analyser
Introduction (Antennas Lab Measurements)
The vector network analyser (VNA) is a very useful, and widely used tool for characterising devices at microwave and millimetre-wave frequencies. It is especially useful for measuring the network parameters of a device and in particular the S-Parameters. This is because it is relatively easy to measure the reflection and transmission of power at different frequencies.
Introduction (Amplifiers)
The use of amplifiers for increasing signal power is almost ubiquitous through all applications involving RF, microwave and millimetre-wave applications. The development of solid-state technology in the last half century has enabled the use of a range of different devices, with transistor amplifiers being amongst the most useful of these. Almost all wireless communications technologies make use of amplifiers, and the design of microwave amplifiers is an in-demand profession for RF engineers. Future technologies at mm-Wave (such as automotive radar and higher frequency WiFi) will require the use of new types of amplifiers. In this lab amplifier design assignment, basics are explored from stability and impedance matching, through to design, simulation.
Pre-lab assignment
Read through and understand this document. Dr SaeJune Park
Report Format and writing (30 marks)
Follow the format presented in the sample report. Top marks will be awarded to well-presented reports:
• with a front cover (title of the report, module, student number, name, email)
• with good length (concise, yet clearly explained results and concepts – not too long!);
• with high-quality images and plots. (No photos or screenshots except for Smith Chart form VNA measurements) If necessary, plot multiple curves on a single graph, e.g. if you have results for length, ? = 1, 2, 3 cm, then plot all three results curves on the same graph. You are encouraged to use Excel, Origin Pro, MATLAB, Mathematica to plot high-quality graphs.
• learn to use equation editor in Word. (No hand drawings)
• with systemic analysis
• with solid conclusions
Part A Antennas Lab Measurement: Vector Network Analyser (40 marks)
In part A, some of the basic functionality of the VNA are explored. The Lab demonstrators introduce the VNA and show how it is calibrated, and then used to measure some simple transmission lines.
Describe the procedure used to make the measurement and discuss the following concepts: (10 marks)
• Calibration
• Reflection (S11)
• Transmission (S21)
Simulate the measured microstrip line using CST. Dimensions of the device can be found in the lecture slides (Week 10). (10 marks) Compare your simulation results to the measured results by attaching S11 and S21 graphs of both simulation and measurement (10 marks) and describe the difference with your understanding (10 marks).
Part B Antennas Lab Measurement: S-parameters (40 marks)
S-parameters of a microstrip line are measured using the VNA in this lab.
- Attach measured S-parameter graphs (S11 and S21) of your transmission line and filter and analyse the behaviour of the devices in terms of the reflection, impedance matching, and transmission. (10 marks)
- Attach measured S-parameter graphs (S11 and S21) of your transmission line and filter with your finger loaded and analyse the behaviour of the device in terms of the reflection, impedance matching, and transmission. (10 marks)
- Attach measured S-parameter graphs (S11 and S21) of your transmission line with vertically loaded copper tape and analyse the behaviour of the device in terms of the reflection, impedance matching, and transmission. (10 marks)
- Attach measured S-parameter graphs (S11 and S21) of your transmission line with horizontally loaded copper tape and analyse the behaviour of the device in terms of the reflection, impedance matching, and transmission. (10 marks)
Part C Antennas Lab Measurement: Smith Chart (40 marks)
Smith Chart in the VNA is used to visually test the impedance matching properties of your devices (both microstrip line and stub-filter) with the presence of your finger and copper tape with two different configurations (vertical and horizontal loading).
Describe how the Smith Chart setting on a VNA is used to explore impedance matching of your device and describe your understanding of 6 different cases with the Smith Chart you measured. 1. Just transmission line (5 marks) 2. With your finger on the transmission line (5 marks) 3. With copper tape loaded in the horizontal direction (5 marks) 4. With copper tape loaded in the vertical direction (5 marks) 5. Stub filter (10 marks) 6. Stub filter with your finger on (10 marks)
Part D Theory: Unilateral Amplifier Stability (40 marks)
1. Show that for a unilateral device where S12 = 0, the μ-parameter test implies that |S11| < 1 and |S22| < 1 for unconditional stability. Note that the μ-parameter test is formulated as: (20 marks)
2. Using the μ-parameter test or otherwise, determine the relative stability of the three devices in the table below. The first one has S11 = 0.xxx where xxx as usual – the last 3 (three) digits in your student ID. Which of the devices is the most stable? (20 marks)
Part E Simulations: Real Amplifier Parameters (40 marks)
You would have been provided with the Hittite HMC636ST89 amplifier.
You can find the S-Parameter file for the amplifier on QMPlus -> Assignment 4 -> HMC636ST89 _S_Parameters.s2p
Import the S-Parameter file into CST through the "Data Import" option in CST Circuits & Systems.
1. Determine the stability of the device (10 marks).
2. Does the unilateral assumption hold (10 marks).
3. What is the maximum available gain (10 marks).
4. Discuss and Analyse 1-3 (10 marks).
Part F Design and Simulation: Amplifier (40 marks)
Using open-circuited shunt stubs in the matching sections and Hittite HMC636ST89 amplifier data, please, design and simulate in CST:
Import the S-Parameter file into CST through the "Data Import" option in CST Circuits & Systems.
1. Matching Networks (20 marks) at f0 = 1.xxx GHz, where xxx as usual –the last 3 (three) digits in your student ID.
2. CST Simulations (10 marks)
3. Discuss and Analyse 1-2 (10 marks).
Part G Conclusions (30 marks)
Weight: 30% towards the course grade