Analysis Issues
There are several issues you should be aware of before using the ABS technique; see below for more information.
You should be aware that circuits with multiple box resonances make it difficult for an ABS analysis to converge. The frequency band for an adaptive sweep should not contain multiple box resonances. If multiple box resonances are present, the number of discrete full analysis points goes up dramatically and synthesis of the data becomes very difficult. If you do not know how to identify box resonances, see Box Resonances for a detailed discussion of box resonances.
Adaptive data, resulting from an ABS analysis, is either de-embedded or non-de-embedded. With other analysis types, when the de-embedding option is enabled (default), then both de-embedded and non-de-embedded response data is calculated and available for display and output. This is not true for an adaptive sweep.
In an adaptive sweep, if you run with de-embedding enabled, de-embedded data is available for the whole band. Non-de-embedded data is available only for the discrete data points at which full analyses were performed while synthesizing the response.
If you wish to have non-de-embedded data for the whole frequency band, you must perform an adaptive sweep with the de-embed option disabled. See the EM Options page of the Circuit Settings dialog box (Circuit - Settings) for details on how to disable the de-embedding option.
For more information about de-embedding, see De-embedding.
As part of the de-embedding process, em also calculates the transmission line parameters, Z0 and Eeff. You should be aware that when running an ABS analysis these parameters are only calculated for the discrete data points at which a full analysis is run. If you need the transmission line parameters at more data points, analyze the circuit using a non-ABS analysis.
Current density data is calculated for your circuit when the Compute Current Density option is enabled in the EM Options page of the Circuit Settings dialog box. For non-ABS sweeps, current density data is calculated for all the response data. For an adaptive sweep, the current density data is only calculated for the discrete data points, therefore, your plot in the current density viewer shows a coarse resolution of your frequency band.
If you wish to calculate the current density data at more points in your band, run a non-ABS sweep for the points in question with the Compute Current Density option enabled.
Please note that when the value of the S-parameters is close to 1 (0 dB) over the entire band you may have small ripples or oscillations in the S-parameter values. This is due to the rational fitting model having too many degrees of freedom when trying to fit a straight line. If this is a problem, it is recommended that you analyze the frequency band in which this occurs with another type of sweep.
When you specify an optional output file for your project, you may select which type of data to output from an adaptive sweep. The data selection is controlled by the Include Adaptive Data checkbox in the File Entry dialog box. If this checkbox is selected, which is the default, then all the adaptive data from an ABS analysis is included in the output file. If this checkbox is cleared, then only the data for the discrete data points is included in the output file. We recommend leaving this box checked.