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AmplifierS2D (S2D File Amplifier, Polynominal Model for Nonlinearity)


Available in ADS

Name Description Units Default
S2DFile Filename for S2D data; enumerated as: S2D filename, File Based None s2dfile.s2d
SSFreq Small signal frequency for interpolating S-parameters; enumerated as: auto, freq, _freq1, _freq2, _freq3 None auto ††
InterpMode Interpolation mode; enumerated as: Linear, Cubic Spline, Cubic, Value Lookup, .... , Value None Linear
InterpDom Interpolation geometry; enumerated as: Data Based, Rectangular, Polar, DB None Data Based
GCFreq ††† Reference frequency for gain compression; must be a positive real number if specified
VarName Name of 1st multi-dimensional variable; use if present in S2D file None None
VarValue Value of 1st multi-dimensional variable; use real or integer values only Integer None
iVarN Name of Nth multi-dimensional variables N={2,...,N}; use if present in S2D file None None
iValN Value of Nth multi-dimensional variables N={2,...,N}; use real or integer values only Integer None
ImpNoncausalLength ‡‡ Non-causal function impulse response order Integer None
ImpMode ‡‡ Convolution mode Integer None
ImpMaxFreq ‡‡ Maximum frequency to which device is evaluated
ImpDeltaFreq ‡‡ Sample spacing in frequency Integer
ImpMaxOrder ‡‡ Maximum allowed impulse response order Integer None
ImpWindow ‡‡ Smoothing window None None
ImpRelTol ‡‡ Relative impulse response truncation factor None None
ImpAbsTol Absolute impulse response truncation factor Integer None

The "S2D Filename" option allows the entry of an S2D file directly. The "File Based" option enables the use of a DataAccessComponent (DAC) for reading in non-S2D file based data.

†† Implies "_freq1" for non-DC part of HB/CE/LSSP simulations. It implies "freq" for all other simulations. For multitone simulations setting SSFreq=_freq1 explicitly gives better results. In general "_freqX" allows the specification of any one of the X tones in an X-tone Harmonic Balance simulation, e.g. selecting SSFreq=_freq2 sets the small-signal frequency of interest to be the second tone of a 2+ tone HB simulation.

††† If manually specified, this frequency must explicitly exist in the S2D file. No interpolation or extrapolation is done along frequency axis for estimating compression characteristics.

If multi-dimensional VAR statements are present in the S2DFile, then these variables are required to be listed in iVarN as indicated in note 8] and corresponding values assigned to them using the iValN parameter. Note that VarName and VarValue serve as iVar1 and iVal1 respectively because of historical reasons.

‡‡ These parameters are also used as specifications for the Amplifier and Amplifier2 components.

Range of Usage

S2D gain compression valid parameter ranges:
GCOMP3: IP3 > 1DBC + 10.6
GCOMP4: IP3 > PS + 8.6
GCOMP5: PS > 1DBC + 3
GCOMP6: PS > 1DBC + 3, IP3 > 1DBC + 10.6

  1. AmplifierS2D is a data-based behavioral model that can represent fundamental tone(s), odd-order harmonics and odd-order intermodulation products of a circuit level amplifier. This model accepts S2D data profiles which can be generated using the AmplifierS2D_Setup component as shown in the design CKT_S2D_extraction.dsn in the example project AmpS2D_prj . Various examples of the use of AmplifierS2D are also provided in this project.
  2. An S2D file, named * . s2d , contains small-signal 2-port S-parameter data with optional noise parameters. In addition, it contains small-signal S-parameter data blocks, noise data blocks, and one of seven possible gain compression blocks {GCOMP1, ... , GCOMP7}. For information regarding the small- or large-signal S-parameter *.s2d data format, refer to S2D Format. The AmplifierS2D model only uses data related to amplifier modeling; it ignores frequency translation data that may be contained in a generic S2D file. The referenced S2D file should reside in the data subdirectory of the current project. The AmplifierS2D_Setup extractor model can be used to automatically generate S2D files.
  3. The AmplifierS2D model blocks DC. For CE simulations, baseband signals are blocked.
  4. For small signal simulations such as AC and S-parameter analyses, AmplifierS2D uses only the small signal ACDATA section of the S2D file. For small signal simulations SSFreq is effectively set to freq internally regardless of user defined enumeration. The GCFreq parameter has no effect on small signal simulations and may be left unassigned.
    For large signal simulations, SSFreq may be defined using any of the five possible enumerations with the following effects:
    • SSFreq = auto implies first HB/Envelope tone. This implies that the reference value for small signal S-parameters is fixed at the 2- port values for _freq1 regardless of the operational compression frequency GCFreq . This is the desirable setting for single tone HB/Envelope simulations.
    • SSFreq = freq implies that the amplifier will be sensitive to small signal values based on individual input tones. This setting is desirable for multi-tone HB / Envelope analyses.
    • SSFreq = _freqN, N={1,2,3}, provides a special provision allowing you to select the small signal value at the first, second, or third HB/Envelope tone on file as the reference for all incoming tones in a generic HB simulation.

      Note Leaving the default value of SSFreq=auto enables the AmplifierS2D instance to function adequately and conveniently for small signal SP/AC as well as single tone HB/Envelope simulations. For multi-tone large signal simulations, SSFreq should be set to freq to allow small signal frequency sensitivity.

  5. For large-signal frequency analysis such as those based on Harmonic Balance, the small-signal S-parameters are used in conjunction with gain compression information in the GCOMPx block. Only odd-order harmonics are modeled during such large-signal simulations because information about even-order harmonics cannot be derived from the GCOMPx specification.
  6. If gain compression information is presented in the GCOMP7 format at multiple frequencies, the AmplifierS2D GCFreq parameter must be assigned to one of the explicitly defined large-signal frequencies of the * .s2d file. The data model does not interpolate across large-signal frequencies so any violation of this requirement will result in termination of the simulation. This model resolves conflicts between user-assigned GCFreq values and large-signal frequency points in GCOMP7-based S2D files as shown in Using GCFreq to Resolve GCOMP7 Frequency Conflicts.
    Using GCFreq to Resolve GCOMP7 Frequency Conflicts
    Number of GCOMP7 blocks Large signal frequencies (s2dfreq) specified in S2D file? GCFreq specified on AmplifierS2D? GCFreq = one s2dfreq? Simulation Result. Compression data used at ...
    0 N/A any N/A N/A
    1 no no N/A simulation frequency
    yes N/A GCFreq
    yes no N/A s2dfreq
    yes no N/A. Simulation terminated with error message.
    yes GCFreq = s2dfreq
    > 1 no no N/A simulation frequency
    yes N/A GCFreq. Use first available power sweep from GCOMP7
    yes no N/A N/A. Simulation terminated with error message.
    yes no N/A. Simulation terminated with error message.
    yes GCFreq = s2dfreq
  7. For good performance using AmplifierS2D, include multiple GCOMP7 blocks at closely-spaced frequencies.
  8. AmplifierS2D can access multi-dimensional S2D files as shown in BEH_S2D_HB_1tone.dsn of the example project AmpS2D_prj. Previous versions of this component required a DataAccessComponent (DAC) for accessing multi-dimensional data. A DAC is no longer necessary to access S2D data from a single file. Please note that multiple S2D files cannot be fed to the same AmplifierS2D component in the course of a single simulation. When S2D data is available in multiple files, consolidate the S2D data into one file and use this master file as the input to AmplifierS2D. Relevant sections of this new file can now be conveniently accessed using the VarName, VarValue and iVar2, iVal2 through iVar10 and iVal10 parameters of the component. Automatic multi-dimensional S2D file generation is facilitated by using the AmplifierS2D_Setup component.
  9. The S21 values expressed in the GCOMP7 block are not absolute values of S21 at the various input power PIN levels. They are differential values in dB domain between power-swept S-parameters at the frequency of the GCOMP7 block and the small-signal S-parameters at the same frequency in the ACDATA block of the *.s2d file. The formats in which ACDATA and GCOMP7 data are represented in the same file may differ and may be in any of the forms DB / MA / RI. When calculating GCOMP7 values manually, exercise care to convert absolute values of both large- and small-signal S-parameters to the dB domain before subtracting the small-signal S-parameters from the large-signal S-parameters to obtain the numeric values in the GCOMP7 section.
  10. AmplifierS2D is implemented using the SML Amplifier model. However, the gain compression information available via an S2D file is limited to the forward transmission characteristic defined by S21. If an application requires the knowledge and use of all four 2-port S-parameter variations but not the use of harmonics, consider using the AmplifierP2D model. If even-order harmonics must be modeled but sweeps of frequency are not required, consider using the AmpH1H2 model instead.
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