Antennas and Microwaves

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For anyone unfamiliar with WinSpice3, it is a port of Berkeley’s Spice34f to the Windows platform by Mike Smith. It provides some good basic plotting routines, backed up by a powerful scripting language for post processing the raw Spice output.

A Vector Network Analyser (VNA) is a bench top instrument primarily used for characterising microwave networks and devices. A VNA measures the reflection and transmission coefficients of the device or network, by applying a known swept signal and measuring the response. The most common and intuitive format for the measured coefficients is Scattering parameters

The script file “VNA for WinSpice3” mimics the operation of a bench top VNA, calculating and plotting a full set of S-parameters for the 2-port device under test. In addition to the S-parameters the Noise Figure for the device is also plotted.

The screen shots below show the “control panel” within the script file together with some typical plots. The circuit analysed was a 2-stage PHEMT LNA, expand the thubnail at the bottom of the page to see the circuit. A zip file containing the script, user guide, quick start guide and example files can be found here: Download VNA.ZIP

WinSpice3 maybe downloaded from here : WinSpice3

VNA for WinSpice3

Control Panel section of the script file.

Noise Figure plot

Smith chart of input impedance

S11 Plot with markers

S21 Plot with markers

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Click Circuit To Enlarge