Feature: RF
Simulation in ADS Sys-parameter datasets are native to Keysight Genesys and SystemVue but do not work in Keysight ADS (advanced design system). Tere is a workaround for importing a sys-parameter dataset into ADS that allows it to perform noise, distortion and compression simulations that involve the Amplifier2 model. Amplifier2 is native to Keysight ADS
and provides similar functionality to sys-parameter models; see Figure 8. Te schematic also contains two data access components, DAC1 and DAC2, used to associate the sys-parameter data with the Amplifier2 model. Te noise figure, OIP3 and OP1dB
data are formatted into a text file and are associated with the Amplifier2 model using the DAC1 component. Te DAC2 component is used to associate the S-parameter data with the Amplifier2
model, resulting in an Amplifier2 model in ADS that can be used for all the simulations discussed here, but in the Keysight ADS. Care must be taken with this method:
When performing RF power sweeps where the Amplifier2 model is being driven heavily into compression, the simulated performance tends to deviate significantly from observed measured performance. Also, an Amplifier2 model that uses S-parameter data along with noise, distortion and compression data is best suited to devices that have good baseline input and output return loss (S11 and S22); this is the case for most Analog Devices RF amplifiers that do not require external RF matching components. A simpler Amplifier2 model can be
created by adding scalar gain to the DAC1 component and omitting the S-parameter data – i.e., DAC2.
New vs old tools Sys-parameter datasets represent a new and useful RF amplifier simulation tool. They are more powerful than S-parameters, which do not model noise, distortion or compression, but are not as elaborate as X-parameter models, which can improve model-level-dependent behaviour such as AM-PM distortion and ACLR. However, sys-parameter models are presented in a simple tabular format (Table 1) and can easily be created by combining S-parameter data with noise figure, OIP3 and OP1dB data. Comparisons of simulated and
measured data show excellent conformance. While sys-parameter models cannot be used in ADS, a relatively easy process can be followed to migrate the datasets using the Amplifier2 model structure, which is native to Keysight ADS.
Table 1: A typical sys-parameter dataset
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