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Understanding the
Fundamental Principles
of Vector Network Analysis


Application Note 1287-1
Table of Contents




Page

Introduction 2
Measurements in
Communications Systems 2
Importance of Vector
Measurements 4
The Basis of Incident and
Reflected Power 5
The Smith Chart 5
Power Transfer Conditions 6
Network Analysis Terminology 9
Measuring Group Delay 11
Network Characterization 12
2




Introduction Network analysis is the process by which designers and manufacturers
measure the electrical performance of the components and circuits used in
more complex systems. When these systems are conveying signals with
information content, we are most concerned with getting the signal from
one point to another with maximum efficiency and minimum distortion.
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.

In this application note, the fundamental principles of vector network
analysis will be reviewed. The discussion includes the common parameters
that can be measured, including the concept of scattering parameters
(S-parameters). RF fundamentals such as transmission lines and the
Smith chart will also be reviewed.

Hewlett-Packard Company offers a wide range of both scalar and vector
network analyzers for characterizing components from DC to 110 GHz.
These instruments are available with a wide range of options to simplify
testing in both laboratory and production environments.



Measurements in In any communications system, the effect of signal distortion must be
Communications considered. While we generally think of the distortion caused by nonlinear
Systems effects (for example, when intermodulation products are produced from
desired carrier signals), purely linear systems can also introduce signal
distortion. Linear systems can change the time waveform of signals
passing through them by altering the amplitude or phase relationships
of the spectral components that make up the signal.

Let's examine the difference between linear and nonlinear behavior
more closely.

Linear devices impose magnitude and phase changes on input signals
(Figure 1). Any sinusoid appearing at the input will also appear at the
output, and at the same frequency. No new signals are created. Both active
and passive nonlinear devices can shift an input signal in frequency or
add other frequency components, such as harmonic and spurious signals.
Large input signals can drive normally linear devices into compression or
saturation, causing nonlinear operation.


Figure 1.
Linear versus
Nonlinear A * Sin 360