Network analyzer (electrical)
[1] Special types of network analyzers can also cover lower frequency ranges down to 1 Hz.
[2] These network analyzers can be used, for example, for the stability analysis of open loops or for the measurement of audio and ultrasonic components.
Six prominent VNA manufacturers are Keysight,[4] Anritsu, Advantest, Rohde & Schwarz, Siglent, Copper Mountain Technologies and OMICRON Lab.
For some years now, entry-level devices and do-it-yourself projects have also been available, some for less than $100, mainly from the amateur radio sector.
The basic architecture of a network analyzer involves a signal generator, a test set, one or more receivers and display.
In a SNA, the reference channel may go to a diode detector (receiver) whose output is sent to the signal generator's automatic level control.
The reference port will compensate for amplitude variations in the test signal at the measurement plane.
The usual method down converts the reference and test channels to make the measurements at a lower frequency.
There are some VNA architectures (six-port) that infer phase and magnitude from just power measurements.
With the levels of processing that are available today, some very sophisticated solutions are available in RF network analyzers.
Here the reflection and transmission data is formatted to enable the information to be interpreted as easily as possible.
The diagram shows the essential parts of a typical 2-port vector network analyzer (VNA).
The position of switch SW1 sets the direction that the test signal passes through the DUT.
Initially consider that SW1 is at position 1 so that the test signal is incident on the DUT at P1 which is appropriate for measuring
The third port of DC1 couples off the power reflected from P1 via A1 and PC1, then feeding it to test receiver 1 (RX TEST1).
The instantaneous value of phase includes both the temporal and spatial parts, but the former is removed by virtue of using 2 test channels, one as a reference and the other for measurement.
A vector network analyzer achieves highly accurate measurements by correcting for the systematic errors in the instrument, the characteristics of cables, adapters and test fixtures.
A modern network analyzer will have data stored about the devices in a calibration kit.
(Keysight Technologies 2006) harv error: no target: CITEREFKeysight_Technologies2006 (help) For the open-circuit, this will be some electrical delay (typically tens of picoseconds), and fringing capacitance which will be frequency dependent.
In some calibration kits, the data on the males is different from the females, so the user needs to specify the gender of the connector.
In other calibration kits (e.g. Keysight 85033E 9 GHz 3.5 mm), the male and female have identical characteristics, so there is no need for the user to specify the gender.
(Keysight Technologies 2003, p. 9) To avoid that work, network analyzers can employ automated calibration standards.
The network analyzer can read the characterization and control the configuration using a digital bus such as USB.
The Keysight 85055A verification kit includes a 10 cm airline, stepped impedance airline, 20 dB and 50 dB attenuators with data on the devices measured by the manufacturer and stored on both a floppy disk and USB flash drive.
Older versions of the 85055A have the data stored on tape and floppy disks rather than on USB drives.
Verification kits are also manufactured for other transmission lines such as waveguide which contain a known through mismatch and attenuations.
The three major manufacturers of VNAs, Keysight, Anritsu, and Rohde & Schwarz, all produce models which permit the use of noise figure measurements.
The vector error correction permits higher accuracy than is possible with other forms of commercial noise figure meters.
