Instrument drivers link the microwave design system with nonlinear test.
Instrument Drivers Link the Microwave Design System with Nonlinear Test
While vector network analyzers, spectrum analyzers and digital sampling oscilloscopes are used for different tasks, they are used the same way throughout the design process.
High performance digital sampling oscilloscopes have repetitive bandwidths into the low mm-wave frequency bands. They also are used for design verification. Waveform data are read from one of the oscilloscope's memory traces into the microwave design system directly over an IB connection. Upon entering the CAE environment, the Fourier coefficients of the waveform data are calculated automatically. Both the time-domain and frequency-domain representations then are stored for access by the simulator or post-processor. The Fourier coefficients then can be attached to a frequency-domain voltage stimulus in a harmonic balance simulation, as shown in Figure 2.
Nonlinear Source Impedance
One additional refinement to a waveform stimulus is the inclusion of an arbitrary nonlinear impedance. Users of the microwave design system can define a level-dependent source impedance using equations on the schematic diagram, or draw impedance values directly from a look-up table.
S-parameters are the single most accurate, universal format for exchanging high frequency circuit information. They are used extensively in lieu of equivalent models for transistors and other components. The CAE link to S-parameters is well-suited for both design verification and modeling.
Spectrum Analyzer Links
Spectrum analyzer data are useful for design verification. Plotting a measured spectrum on the same graticule as the corresponding harmonic balance simulation result is the most direct method of comparing measured vs. modeled performance. However, spectrum analyzer data lack phase information. The phase relationships between harmonics are critical in nonlinear circuits where devices may, or may not, be operating past their breakdown regions, depending on the instantaneous amplitude of the waveform. Phase information of arbitrary signals is only available through Fourier techniques, such as the one built into the oscilloscope driver.
New instrument drivers have been developed for the microwave design system. The measured data that is imported into the CAE environment will improve not only the quality of circuit simulations, but also a design's technical documentation.
The new instrument drivers are available immediately for the HP series 300 and 400 workstations and are included with the HP microwave design system software.
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|Article Type:||product announcement|
|Date:||Apr 1, 1991|
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