The document discusses network analyzers, which are instruments used to measure the complex scattering parameters of networks. A network analyzer measures both the amplitude and phase of reflected and transmitted signals. It operates by sending a signal through a device under test and measuring the reflected and transmitted signals. Network analyzers have improved over time, with automation and computer correction increasing measurement accuracy and speed. Modern vector network analyzers can measure both single-port and dual-port networks.

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Network analyzer
C&T RF Antennas Inc
A network analyzer is a new type of instrument for measuring network parameters. It can directly
measure the complex scattering parameters of active or passive, reversible or irreversible
dual-port and single-port networks, and gives the amplitude and phase of each scattering
parameter Frequency characteristics. Network analyzers are based on four-port microwave
reflectometers (see Standing Wave and Reflectometry). In the mid-1960s automation, the use of
computers by a certain error model at each frequency point to correct the directional coupler
imperfection, mismatch and blowby caused by the error, so that the measurement accuracy is
greatly improved, The measurement accuracy of the most accurate measurement line technology
in the metering chamber can be achieved, while the measurement speed is increased by several
tens of times.
Introduction
Vector network analyzer, which comes with a signal generator that can scan a frequency band
frequency. If the single-port measurement, the excitation signal is added to the port, by
measuring the amplitude and phase of the reflected signal back, you can Determine the
impedance or reflex situation. For the two-port measurement, you can also measure the
transmission parameters. Because of the distribution of parameters such as obvious, so the
network analyzer must be calibrated before use.
Development process
Network analyzers are based on four-port microwave reflectometers (see Standing Wave and
Reflectometry). In the mid-1960s automation, the use of computers by a certain error model at
each frequency point to correct the directional coupler imperfection, mismatch and blowby
caused by the error, so that the measurement accuracy is greatly improved, The measurement
accuracy of the most accurate measurement line technology in the metering chamber can be
achieved, while the measurement speed is increased by several tens of times.
Parameter
The parameters (scattering parameters) are used to evaluate the performance of the DUT
reflected signal and the transmitted signal. The parameter is defined by the ratio of two complex
numbers and contains information about the amplitude and phase of the signal. The parameters

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are usually expressed as:
Output-input
Output: DUT port number of the output signal
Input: DUT port number of the input signal
For example, parameter S21 is the ratio of the output signal from port 2 on the DUT to the input
signal to port 1 on the DUT. Both the output signal and the input signal are represented by a
complex number.
When starting the Balancing-Unbalance conversion function, you can choose to mix the S
parameters.
Principle
When an interface of each port of an arbitrary multi-port network matches, the incident traveling
wave n input by the first port is scattered to all other ports and transmitted. If the first port of the
outgoing traveling wave m, then the mouth of the scattering parameters mn = m / n. A
dual-ported network has a total of four scattering parameters 11, 21, 12 and 22. When both
terminals match, 11 and 22 are the reflection coefficients for ports 1 and 2 respectively, 21 is the
transmission coefficient from 1 to 2, and 12 is the inverse transmission coefficient. When a port
terminal mismatch, the terminal reflected by the traveling wave again into the mouth. This can
be considered equivalently if the port is still matched, but a traveling wave m is incident on the
port. Thus, in any case, simultaneous equations of the equivalent incident and outgoing traveling
waves and scattering parameters for each port can be listed. Accordingly, all the network
characteristic parameters can be solved, such as input reflection coefficient, voltage standing
wave ratio, input impedance and various forward reverse transmission coefficients when the
terminal is mismatched. This is the most basic working principle of network analyzer [1]. A
single-port network can be considered as a special case of a dual-port network in which, except
11, constant 21 = 12 = 22. For a multi-port network, except one input and one output port, a
matching load can be connected to all the remaining ports, which is equivalent to a two-port
network. Taking each pair of ports as the input and output of the equivalent dual-port network in
turn, taking a series of measurements and listing the corresponding equations, all the two
scattering parameters of the port network can be solved to obtain all the characteristics of the
n-port network parameter. Figure left for the four-port network analyzer measuring S11 test unit
schematic, arrows indicate the path of the traveling wave. Signal source u output signal through
the switch S1 and directional coupler D2 input to the measured network port 1, which is the
incident wave a1. The reflected wave of port 1 (that is, the outgoing wave b1 of one port) is
transmitted to the measuring channel of the receiver via the directional coupler D2 and the
switch. The output of the signal source u is simultaneously transmitted to the reference channel
of the receiver via the directional coupler D1, which is proportional to a1. Thus, the dual channel
amplitude-phase receiver measures b1 / a1, that is, S11 is measured, including its amplitude and
phase (or real and imaginary parts). Measurement, the network port 2 connected to the
matching load R1, to meet the conditions specified by the scattering parameters. The other
directional coupler D3 in the system also terminates the matching load R2 to avoid adverse
effects. The remaining three S-parameter measurement principle and the same. Figure right to
measure the different Smn parameters should be placed when the switch position.

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Before the actual measurement, a series of measurements are made by the instrument with
three standard instruments of known impedance (for example, a short circuit, an open circuit,
and a matched load), called calibration measurements. From the measured results and the ideal
(no instrument error) should be compared to the results obtained by calculating the error model
of the error factor and stored in the computer, in order to test the measured error correction.
Click here for calibration and correction at each frequency point. Measurement procedures and
calculations are very complex, non-manual competence.
The above-mentioned network analyzer is called a four-port network analyzer because the
instrument has four ports, which are respectively connected to the signal source, the DUT, the
measurement channel, and the measured reference channel. Its disadvantage is the complex
receiver structure, the error model does not include the error generated by the receiver.
New development
1973 also developed a six-port network analyzer. It uses a directional coupler and hybrid
connector (magic) composed of a six-port network as a measurement unit, in addition to the two
ports were connected to the signal source and the DUT, the remaining four ports are connected
to the amplitude detector or power meter. By detecting the appropriate combination of the four
amplitudes, the mode and phase of the measured network scattering parameters can be
obtained. It eliminates the need to use sophisticated dual-channel receivers for phase
information, making the measurement system's hardware significantly simplified. In addition, it
has more than the required number of redundant measurement ports, which can be used to
check the reliability of measurements with redundant data. But it's computationally more
complex than a four-port network analyzer. Dual six-port network analyzer to measure dual-port
network, which uses a six-port network meter connected to the measured network port 1, the
other connected to the port 2 in the measurement process to avoid switching or artificial
inversion of the measured network The inputs and outputs further improve the measurement
accuracy.
Keywords:
Network Analyzer, RF Analyzer, Microwave Network Analyzer, Vector Network Analyzer, Wireless
Design and Test,