Agilent Appcad

Software fom Agilent covering Transmission lines, Transistor Parameters, cascaded noise etc. Its not ADS, but its free!
Download Link - 14MB

TXLine - Transmission Line Calculator

This free software from AWR analyses/synthesises microwave transmission lines for microstrip, stripline, coplanar and slotline.
Download v1.1 Here, or Newer 2003 Version

RFSim99 - Microwave Circuit Simulator

This free shareware from HyDesign can perform linear S-parameter simulation, tolerance analysis, stability circles, matching, tuning and filter design.
Download Here - 2MB

QUCS - Circuit Simulator

Quite Universal Circuit Simulator is an Open Source circuit simulator for Windows, Mac and Linux with schematic capture, s-parameters, flexible graphing.
Download Link

Sonnet Lite

Sonnet Lite is a free, limited capacity, version of a professional EM Solver for microstrip and stripline design.
Download Link

LTSpice - aka SwitcherCAD

Free Spice-based simulator from Linear Technology with full schematic entry, libraries, custom symbols etc.
Download Link ~5MB

Analog Devices

Free tools for DDS, rf calculators etc.
Download Link

L-Band Synthesiser

As described in the June-2006 Scatterpoint, software for the 'Simple and Cheerful L Band Synthesiser' is here

CAD Software Links

Our own maintained Links page to professional Microwave software
Microwave CAD Suppliers

Feko Lite

Feko Lite is a free, limited capacity, version of a professional EM Solver for Antenna design.
Download Link

Super Filter design program called "LC" or "Elsie"

This very useful program from Jim Tonne WB6BLD has a free version, and his website has other handy utilities.

G4JNT Software Archive

Courtesy of Andy Talbot G4JNT, useful Beacon related utilities.
Download Link

Paul Wade W1GHZ (ex N1BWT) "On-line Microwave Antenna Book"

This large and thorough work is split into sections for easy downloading.
Link to table of contents of the "Microwave Antenna Book"

SABOR design aid for horns, dishes etc

From Madrid University: SABOR

AADE Filter Design

Free lumped/crystal filter design and analysis: