AppCAD is an easy-to-use program that provides you with a unique suite of RF design tools and computerized Application Notes to make your wireless design job faster and easier. AppCAD’s unique, interactive approach makes engineering calculations quick and easy for many RF, microwave, and wireless applications. AppCAD is useful for the design and analysis of many circuits, signals, and systems using products from discrete transistors and diodes to Silicon and GaAs integrated circuits. The keyword for AppCAD is easy – no circuit files, no manuals – just quick and easy.

System Requirements

AppCAD is designed to run on all 32-bit Windows® operating systems. AppCAD has been verified to run on these operating systems:

• Windows 2000

• Windows XP

• Windows NT4 with Service Pack 6 or later

• Windows Me

• Windows 98 – All versions

• Windows 95 – Windows 95 version 4.00.950c or later

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VisSim is an award winning program for the modeling and simulation of complex dynamic systems. This includes the ability to construct and simulate block diagrams. The visual block diagram interface offers a simple method for constructing, modifying and maintaining complex system models. The simulation engine provides fast and accurate solutions for linear, nonlinear, continuous time, discrete time, time varying and hybrid system designs. With VisSim, users can quickly develop software or “virtual” prototypes of systems or processes to demonstrate their behavior prior to building physical prototypes. Built-in integration tools allow users to communicate seamlessly with MATLAB and Mathcad. A VisSim/SIMULINK Translator™ allows SIMULINK users to import SIMULINK block diagrams directly into VisSim.
The user builds his system model by selecting predefined blocks from a block library and simply wiring the blocks together. Each block of the diagram performs a function. Users can also create custom blocks in C, Fortran or Pascal and add them to the VisSim block library. After the model is built, you click the “Go” button and the results of the simulation are interactively displayed.source

HbFree is intended for simulation of radio frequency (RF) and microwave (MW) analog non-autonomous circuits under multi-tone excitations. It was developed for MW mixers and power amplifiers design.Package contains free version of harmonic balance simulator program “HaBala”, Spice-to-Habala translator “s2h” and a few utilities. It allows the following components to be used: R,L,C, transmission lines (lossless for now), V and I sources, Diodes and MESFETs. “HaBala” simulator implements piecewise harmonic balance technique with 2-D FFT to handle a few monocrome sources. Input language is very close to SPICE, output format is SPICE ASCII RAW. “HaBala” simulator itself allows additional elements to be used: S- and Y- matrices of 2N-poles, strip- and microstrip transmission lines, some discontinuities. But these elements are not implemented in “s2h” translator and will be available later. source

Agilent RF Design Environment (RFDE) is a software design platform for large-scale RF/mixed-signal IC designs in the Cadence environment. It integrates Agilent’s leading RF simulation technologies into the Cadence industry-standard analog/mixed signal design flow framework.

All embedded in Cadence Affirma Analog Design Environment, RFDE consists of five combined parts:

• ADSsim, which includes the following analysis and simulation tools from Agilent’s ADS: DC, AC/S-parameter, harmonic balance, circuit envelope, transient / convolution, parameter sweep, parameter optimization, and Monte Carlo yield analysis.
• Data Display, which includes Measurements expressions, probe circuit, auto display, and snapshot mode.
• adsLib, which includes RF sources, Circuit components, System components, Microstrip and Multilayer components.
• Wireless Test Benches offering system-level wireless signal sources and standards measurements.
• Momentum, a fully integrated planar electromagnetic simulator for passive circuit analysis.

RF Design Environment makes available important frequency-domain and mixed-domain simulation technologies; optimization and statistical design tools; additional device, system, and behavioral models; and powerful data display and post-processing.

All of these features provide valuable benefits to the large-scale RF and mixed signal IC designers. These benefits are provided within the Cadence design flow and Cadence simulation user interface – and side by side with established Cadence tools such as Spectre and Spectre RF.

RFDE is embedded in the Cadence Affirma Analog Design Environment and is accessible to designers the same way as Cadence Composer schematic editor, Assura/Diva layout verification, and Spectre/SpectreRF. Simulations are set up using Affirma, in the same way that simulations are set up for Spectre RF and other simulators. Simulation states can be saved and other features in the Cadence design environment are also available.

RF Design Environment: Simulation Technologies

The simulator technologies in RF Design Environment use a mature and robust frequency domain simulator and mixed-domain solutions that take advantage of the strengths of both time-domain and frequency-domain simulation.

Harmonic Balance Simulator provides frequency-domain, steady-state, large signal analysis of non-linear circuits excited with multi-tone sources. Harmonic Balance (HB) is used to simulate noise, gain compression, harmonic distortion, oscillator spurs, phase noise, and intermodulation products in non-linear circuits much faster than SPICE-based simulators.

Harmonic Balance is best applied to circuits with two or more large signal tones (multiple tones, frequency translation, mixers, detectors, and multipliers) with frequencies that do not need to be co-periodic. It can handle frequency domain models including transmission lines, microstrip lines and N-ports. It is very useful on oscillator and VCO design and analysis.

Amplifier compression, harmonic distortion, oscillator spurious, phase noise, and mixer inter-modulation products are other types of analysis that HB performs extremely well.

Circuit Envelope simulation uses an advanced time-swept harmonic balance simulation technique. It enables analysis of time-varying carriers such as PLL, AGC, VCO, VCA, modulators, and the like.source

RFSim99 is a free linear S-parameter based circuit simulator offering schematic capture, simulation, 1 port and 2 port S-parameter display and file support, tolerance analysis, stability circles, and much more.It can cost large sums of money to get a workstation seat at some of the high end simulation and analysis software suites. But the underlying mathematics that these programs use is not secret, it is in the public domain and there are low cost or shareware packages that will do the same computations. Often they lack the features and the extensive user interfaces, but the internal engines are running the same equations.

For low frequency or time domain simulations there are versions of SPICE freely available. For RF simulations the field is smaller, but one free program that repeatedly crops up in the listings is RFSim99.

RFSim99 works with S-parameters. This means that not only will it simulate and analyse circuits built out of its internal library of components, but that it can accommodate any circuit block or stage for which these are known. S-parameters are easily measured with a network analyser, so RFSim99 avoids the problems of many packages by not being bound to third party models. As well as the features one would expect to see, such as schematic drawing and graphical analysis, there are a few really good extras, such as an integrated filter design tool and the ability to run tolerance sweeps.

RFSim99 was written by Stewart Hyde. The embedded link to his web site is no longer valid, but at pRF we were so impressed by the program that we tracked him down.
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