Waveform Engineering and Behavioral Modeling
The traditional RF power amplifier designer has relied for years on current-voltage characteristics, S-parameters, load-pull, AM-AM and AM-PM behavior, scalar power and output spectrum to design their non-linear devices. It is only recently that companies like Mesuro (acquired by Focus Microwaves in 2015) have developed WaveForm Engineering techniques driving both the measurement and mathematical analysis required for engineers to optimize at all stages of the development, which includes transistor optimization, circuit design, and system integration.
The 'Cardiff Model Lite' is a third order formulation that allows the extension of S-Parameters under Large Signal operation. It is a Polyharmonic Distortion (PHD) based behavioral model formulation, based upon the harmonic superposition principle, as shown below:
The following diagram shows the basic components of this system:
To extract the Cardiff Model Lite, a fundamental tone drives the device, which is itself simultaneously stimulated with a small signal tone at each harmonic frequency. The internal independent phase controllable source of the network analyzer is used as the stimulus.
The phase of this generator is swept with at least 6 different phases measured to allow the model to predict performance correctly.
This perturbation process can be completed on both sides of the device. If a device performing in non-50Ω conditions is considered, a Cardiff Model + behavioral model is generated, using load pull data analysis.
Cardiff Model Unit
The Cardiff Model Unit can be added to an existing VNA, and modeling results extracted in ADS or Microwave Office.
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Cardiff Model Lite
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