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A New Suite of RF/Microwave Design Tools

An RF/microwave design solution constructed using advanced object-oriented programming methods for impressive performance, reliability and ease of use

June 1, 1998
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A New Suite of RF/Microwave Design Tools

Applied Wave Research Inc.
Redondo Beach, CA

Microwave Office is a completely new suite of RF/microwave design tools built from the ground up for operation in Windows® ’95 and NT environments. Included in the suite are the VoltaireXL™ linear and nonlinear circuit simulator and the EMSight™ full-wave, three-dimensional electromagnetic (EM) simulator. The entire design solution is constructed using advanced object-oriented programming methods that result in impressive performance, reliability and ease of use.

The Circuit Simulator

VoltaireXL is the first really new, big-league linear and nonlinear circuit simulator to be introduced in a decade. Unlike existing products, VoltaireXL is optimized for RF and microwave applications and uses the latest circuit simulation technology. The software includes nonlinear circuit simulation by the single- and

multitone harmonic balance Volterra series (both static and time varying); mixer analysis (also called conversion-matrix analysis); advanced, high speed linear analysis; and high speed noise analysis. Figure 1 shows a VoltaireXL display of the output spectrum from a single-stage GaAs MESFET amplifier. In addition, the simulator includes integrated schematic capture (including support for MMICAD and SPICE netlists). Figure 2 shows the schematic

representation of a distributed single-stage GaAs MESFET amplifier circuit. In the near future, the circuit simulator will include nonlinear oscillator, noise (including phase and mixer noise) and stability analyses.

While existing harmonic balance simulators are built on top of the code developed originally for analog circuit simulation, VoltaireXL has been developed specifically for RF and microwave applications. This configuration makes it considerably faster than existing products — virtual real-time tuning of simple nonlinear circuits with harmonic balance is possible.

Many of VoltaireXL’s capabilities are simply unavailable in existing simulators. For example, Volterra series analysis, which is a factor of 10- to 100-times faster than a multitone harmonic balance technique, is the fastest way to analyze intermodulation (IM) in near-linear circuits. Moreover, this analysis integrates easily with linear analysis, allowing noise figure and other linear characteristics, such as gain and port SWR, to be optimized simultaneously with IM. The simulator uses the time-varying Volterra series for mixer IM analysis — the only accurate and practical way to solve this problem. Anyone who has spent an entire weekend (if not an entire week) running a three-tone mixer IM analysis only to obtain nonsensical results will be pleased to see an accurate calculation of mixer IM emerge from VoltaireXL in minutes rather than hours.

Of course, multitone harmonic balance analysis has its place. VoltaireXL’s multitone harmonic balance capability makes use of the latest simulation technology. Thus, multitone analysis, which has been painfully slow in the past, is significantly faster.

VoltaireXL uses a super-fast, object-driven approach that allows users to tune circuits in real time using sliders that control parameter values. The simulator’s linear, nonlinear and noise analyses are extraordinarily fast because circuit equations are formed directly from the schematic representation without an intervening netlist. Furthermore, because of the way the circuit equations are formulated, it is possible to tune and optimize circuit parameters in real time even in very large and complex circuits — one of VoltaireXL’s most startling capabilities. For example, a slider is used to vary a stub length and, as the slider is moved, the circuit’s response change is displayed on a Smith chart or Cartesian graph.

The linear frequency domain simulator includes an extensive catalog of models for lumped and distributed elements including microstrip, stripline, coplanar and other common elements for building high frequency circuits. A linear-only version of the simulator (VoltaireLS™) also is available.

THE EM SIMULATOR

In cases where the most suitable model is not available or proximity effects undermine the accuracy of the models, users can defer to the EMSight full-wave EM simulator. EMSight (introduced originally in late 1997) has been upgraded and enhanced with the release of version 2.0. (Microwave Office includes this latest version of EMSight.) Enhancements to the simulator include bidirectional DXF and GDSII translators, internal ports (both probe feeds and gap ports) and extended antenna support, including E-field near-field animation, probe feed ports, far-field plots for directivity (right-hand circular polarization, left-hand circular polarization, Ef and Eq) and a new graph type specialized for antenna plots. EMSight also contains lumped-element parameter extraction (SPICE netlist output); a simple schematic-driven linear circuit simulator used to connect EM blocks and add internal lumped elements; improved simulation time estimation; improved visualization capabilities, including standing-wave plots, intensity color mapping settings and vector or scalar display of currents and E-fields; and variable via meshing. (Improved meshing meshes only the outer surfaces of vias.) Figure 3 shows a typical EMSight simulation of an L-band microstrip patch antenna including the probe feed.

One of the problems inherent in existing simulators has been the slow pace at which they adopt new technology as it becomes available. Because the simulator suite is written in object-oriented C++, Microwave Office incorporates new methods easily as they become available. Updates to VoltaireXL include genuine improvements in usefulness, speed and efficiency — not simply cosmetic improvements to the user interface.

Conclusion

Microwave Office operates under both Windows ’95 and NT 32-bit environments. It is optimized for these operating systems, not ported to them. As a result, both VoltaireXL and EMSight can be used efficiently with inexpensive Pentium machines and, hence, Microwave Office does not require an expensive UNIX workstation. VoltaireXL’s schematic-capture environment is simple and intuitive yet has wide capability. Pricing is $8500 for the VoltaireLS linear simulator only, $12,500 for the EMSight EM simulator only, $14,300 for the linear simulator and EMSight (Microwave Office LS), and $20,300 for the linear/nonlinear simulator and EMSight (Microwave Office XL). Evaluation copies of the software can be downloaded from the company’s Web site at http://www.appwave.com.

Applied Wave Research Inc.,
Redondo Beach, CA
(310) 370-2496.

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