Vector Network Analyser for Microwave Measurement (Network Analysis, types of analysers, working, s-parameter measurement using VNA, MVNA applications)

1. NETWORK ANALYSERS
FME Presentation
Amala Putrevu
D018

2. NETWORK ANALYSIS
1. Used by designers to measure the electrical performance of
devices
2. When systems are conveying signals with information content, we
need
1. maximum efficiency
2. minimum distortion.
3. Vector network analysis is a method of accurately characterizing
such components by measuring their effect on the amplitude and
phase of swept-frequency and swept-power test signals. [1]

3. LIGHTWAVE ANALOGY
• Network analysis is concerned with the accurate
measurement of the ratios of the reflected signal to the
incident signal, and the transmitted signal to the
incident signal. [1]
RF
Incident
Reflected
Transmitted
Lightwave
DUT

4. TYPES OF ANALYZERS
1. Scalar Network Analyser
1. Only measures amplitude (i.e. scalar properties) of a device
2. Vector Network Analyzer
1. Measure amplitude and phase (i.e. vector properties) of device under test
2. AKA Gain-phase meter or automatic network analyzer
3. Large Signal Network Analyzer
1. Highly Specialised for Large Signal Analysis [2]

5. DEVICES TESTED BY VNA [2]

6. REASONS FOR TESTING EQUIPMENT USING
VNA
To verify specifications of building blocks in a
complex RF systems such as amplifiers and filters
in a transceiver
To ensure component or circuit cause no distortion
in the transmission of communications signals
•Linear : constant amplitude, linear phase /
constant group delay versus frequency
•Nonlinear : harmonics, intermodulation,
compression, AM-to-PM conversion
To ensure good matching for absorbing energy
efficiently (such as good matching antenna)

7. BLOCK DIAGRAM [3]

8. WORKING
VNA Working can be understood in four phases:
• VNA Stimulus
• Signal Separation
• Receiver & Signal Detection
• Processor & Display

9. WORKING: VNA ANALYSER
STIMULUS
1. VNA is an active instrument
2. Generates test signal and then measures the response
3. Sources can be
1. Open Loop VCO
1. Good Phase Noise Performance
2. Low Frequency Accuracy and Flexibility
2. Digitally synthesized
1. More Expensive than VCO
2. Provide exact Frequency signal

10. WORKING: SIGNAL SEPARATION
1. Called the test set
2. Has two main functions
1. Measure a portion of the incident signal to provide a reference for what is
termed “ratioing”. This can be accomplished by using
1. Splitters [Broadband but introduce a loss of 6 dB]
2. Directional Couplers [Low loss, high directivity, used only in microwave range]
2. Separate the incident (forward) and reflected (reverse) travelling waves at the
input of the DUT.
1. Couplers are preferred [directional, low level of loss]

11. WORKING: SIGNAL DETECTION
1. First Stage: Radio Receiver with demodulator/detector
2. Receiver preferred – Tuned Radio Receiver [Best sensitivity,
spurious signal rejection]
3. Based on Superheterodyne principle
4. Apply the signal output from receiver to the analogue to digital
converter
5. Both magnitude and phase information extracted from the
Intermediate Frequency (IF) signal
6. Digital Signal Processing techniques can be used to analyser the
signal further

12. WORKING: DISPLAY
1. Necessary to display the signal in a format that can be interpreted
2. The reflection and transmission data is formatted to enable the
information to be interpreted as easily as possible.
3. Most RF network analyzers incorporate features including linear
and logarithmic sweeps, linear and log formats, polar plots, Smith
charts, etc. Trace markers, limit lines and also pass / fail criteria
may also be added in many instances [3]

15. UNIQUE MVNA APPLICATIONS
1. Antenna Characterization
2. Quasi-Optics Transmission-Reflection and Radar modelling
3. Material Characterization without and with Magnetic Fields
4. Waveguide and Cavities setups [5]

16. REFERENCES
[1] http://cp.literature.agilent.com/litweb/pdf/5965-7917E.pdf
[2] http://www.radio-electronics.com/info/t_and_m/rf-network-analyzer/
analyser-basics-tutorial.php
[3] http://www.microwaves101.com/encyclopedias/network-analyzer-
measurements
[4] http://commons.wikimedia.org/wiki/File:Vna3.png
[5] http://www.abmillimetre.com/Application.htm