Vector network analyzers

01

Plan the calibration and its standards

Anritsu's VectorStar calibration guide describes SOLT (Short-Open-Load-Thru) as a defined-standards calibration: because each standard's behaviour is specified in advance by data or models, measuring them lets the VNA solve all error terms. In Anritsu's words, “The load behavior largely sets the directivity terms, the short and open together largely determine source match and reflection tracking and the thru largely determines transmission tracking and load match.” [1]

Standards are defined either by models (a line length plus frequency-dependent inductance for shorts or capacitance for opens; line length, shunt capacitance, resistance and series inductance for loads) or by .s1p files. Anritsu reports that .s1p definitions can substantially narrow uncertainty, and that below about −50 dB reflection coefficient uncertainties are high with either method. A sliding load can replace the fixed load but still needs a fixed load at low frequencies (below 4 GHz for V connectors, 2 GHz for others), and an unknown reciprocal thru can stand in where a real thru is impractical, at somewhat lower accuracy. [1]

Keysight adds that changing the IF bandwidth after calibration leaves the accuracy uncertain, so settle measurement settings before calibrating. [2]

Give the supplier the frequency range, number of ports, connector types or fixtures, devices to be measured (filters, amplifiers, cables, antennas), required dynamic range and accuracy, measurement speed, calibration kits or electronic calibration needed, and time-domain or other options.

02

Set IF bandwidth and averaging for noise and speed

Keysight's VNA help explains that the receiver's IF filter bandwidth can be set down to 1 Hz; each tenfold reduction in IF bandwidth lowers the noise floor by 10 dB, but narrower IF bandwidths lengthen sweep time. Averaging, by point or by sweep, gives the same general noise reduction and is more effective for minimising very low noise, though Keysight says “Generally, Averaging takes slightly longer than IF bandwidth reduction to lower noise”. [2]

Editorial calculation: reducing IF bandwidth from 10 kHz to 100 Hz is two decades, lowering the noise floor by about 20 dB and, since each point's measurement time rises as bandwidth falls, lengthening the sweep accordingly. [2]

Rigol, the supplier linked to this page, lists DNA800 and DNA5000/6000 series vector network analyzers. [3]

03

Choose port count and test-set architecture

Copper Mountain Technologies' VNA series comparison sorts its analyzers by port and path architecture. Its 1-port VNAs/reflectometers cover 1 MHz–14 GHz and connect directly to the antenna or device without a test cable; its TR series are 2-port, 1-path instruments for 50 MHz–3.5 GHz; its Value series are 2-port, 2-path portable VNAs for 100 kHz–18 GHz at a measurement speed of 25 µs per point; its Select series offer 2 to 16 ports over 9 kHz–18 GHz, also at 25 µs per point; and its Advanced series cover 100 kHz–22 GHz with a typical dynamic range of 135 dB at 10 Hz IF bandwidth, with measurements up to 330 GHz using compatible frequency extenders. [4]

Check which calibration types, such as the SOLT calibration described above, the chosen architecture supports. [1] The 135 dB figure is quoted at 10 Hz IF bandwidth, which ties dynamic range to the IF bandwidth and sweep-time trade described above. [2] [4]

Editorial calculation: at 25 µs per point a 1,601-point sweep takes about 40 ms before any averaging; reducing IF bandwidth to reach the stated dynamic range lengthens that time.

Give the supplier the number of ports, the frequency range, whether full 2-path correction is needed and the dynamic range at the IF bandwidth you will use, and ask for the sweep time at your point count.

04

Compare what suppliers offer

The supplier linked to this page lists vector network analyzers; its card links to the page reviewed.

Ask any supplier for frequency range, ports, dynamic range and trace noise at stated IF bandwidths, output power range, measurement speed per point, calibration methods and kits supported, connector types, time-domain and fixture de-embedding options, and calibration certificate.

05

Trace the analyzer blocks

This is a functional reference built from the sources cited; it is not one maker's specification.

06

Fill the specification fields with values for your devices

A VNA quotation needs values for your devices and fixtures. The table explains each field, gives published values where a reviewed source states them, and says what to obtain from the supplier.

07

Send the device and accuracy data together

Paste it into your enquiry below or into an email to a maker, then replace every bracket.

Devices: [type; frequency range; ports]
Connectors: [types; fixtures]
Accuracy: [dynamic range; uncertainty]
Speed: [points; sweep time]
Calibration: [method; kits]
Options: [time domain; de-embedding]

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