NETWORK ANALYSERSFME Presentation

Amala Putrevu

D018

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]

LIGHTWAVE ANALOGY

RF

Incident

Reflected

Transmitted

Lightwave

DUT

• Network analysis is concerned with the accuratemeasurement of the ratios of the reflected signal to theincident signal, and the transmitted signal to theincident signal. [1]

TYPES OF ANALYZERS

1. Scalar Network Analyser1. Only measures amplitude (i.e. scalar properties) of a device

2. Vector Network Analyzer1. 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 Analyzer1. Highly Specialised for Large Signal Analysis [2]

DEVICES TESTED BY VNA [2]

To verify specifications of building blocks in acomplex RF systems such as amplifiers and filtersin a transceiver

To ensure component or circuit cause no distortionin 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 energyefficiently (such as good matching antenna)

REASONS FOR TESTING EQUIPMENT USING VNA

BLOCK DIAGRAM [3]

WORKING

VNA Working can be understood in four phases:

• VNA Stimulus• Signal Separation• Receiver & Signal Detection• Processor & Display

WORKING: VNA ANALYSER STIMULUS1. 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

WORKING: SIGNAL SEPARATION

1. Called the test set

2. Has two main functions1. 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]

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

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]

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]

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