eval_controlled_pwl()

Evaluates the piece-wise linear response of system when supplied with N pairs of data points in vector format

Syntax
eval_controlled_pwl( pwlvector, xin, [stretch], [scale] ) where pwlvector is a list( in1, out1, ..., inN, outN)

Arguments

Examples

The response of a system described by the three-point PWL vector
list( in 1 , out 1 , in 2 , out 2 , in 3 , out 3 ) to input xin , stretch , and scale is
xout = eval_controlled_pwl( list(in 1 , out 1 , in 2 , out 2 , in 3 , out 3 ), xin, stretch, scale )

• The input is stretched up to
  xin ^~ = min( xin*stretch, stretchEps ) where stretchEps is an internal limit generated when stretch is too close to zero.
• The proper bin for xin ^~ is detected using the three corner points along input axis: in ₁ , in ₂ , and in ₃ , which may be out of order in the list() or file forms.
• If xin ^~ falls within bounded limits, e.g., in ₁ and in ₃ , then xout ^~ is computed using linear equation:
  (xout ^~ - out 3 ) * (in 1 - in 3 ) = (xin ^~ - in 3 ) * (out 1 - out 3 ) else, if it falls in either of the two unbounded sections with nearest data point in _i , out _i , then constant extrapolation is done as follows:
  xout ^~ = out i
• If scale factor is defined, it is used on the raw output. If not, scale is assumed to be unity. Thus:
  xout = xout ^~ * scale
  Given:
  pwlvector = list( 2, 4, 3, -1, -1, 3 )
  xin=1
  stretch=0.75
  scale=3.0
  xin ^~ = 3/4
  which falls within input side range (-1,2] with output side range (3, 4] . Thus,
  xout~ = (3/4 - (-1))/(2 - (-1)) * (4 - 3) + 3
  = 7/12 * 1 + 3
  = 43/3
  xout = 43/3 * 3.0
  = 43

Notes/Equations

1. This function exists in ADS primarily to emulate the behavior of piece-wise linear (PWL) behavior of single input, single output controlled voltage and current sources of the Cadence Spectre library. For further information about the sources cccs , ccvs , vccs , and vcvs , see the Cadence Spectre simulator's analog library documentation.
2. This function supports PWL values either directly in list() or indirectly in file format. For PWL files, the following approach is recommended to create a list-based entry for the SYM function:
   pwlData = read_data("file","<pwlvector_filename>","sppwl")
   pwlIn = dstoarray(pwlData,"inputPWL")
   pwlOut = dstoarray(pwlData,"outputPWL")
   xout = eval_controlled_pwl(list(pwlIn, pwlOut), xin[, stretch[, scale]])
   In this case the list() function concatenates the two vectors pwlIn and pwlOut by interleaving the values as expected by eval_controlled_pwl().
   A PWL file is a simple ASCII data file containing two columns, for input and output values marking corner points of the function. This file may contain comment lines preceded by the ";" character. No explicit format information is expected from such a file. An example of a PWL file is:
   ; PWLfile
   ; Input Output
   2 4.0
   3 -1.0
   -1 3.0
   The file contents are equivalent to
   list( 2, 4.0, 3, -1.0, -1, 3.0 ) Data points may be supplied out of order in either list or file format. The function automatically checks for duplicate points, which it tolerates, for ambiguity, such as one-to-many input-output mapping causing an error when encountered.
3. Default value of stretch is 1.0, but if a value is supplied and found to be too close to zero, its effective value is limited to a small non-zero number. This prevents interpolation errors due to infinitesimal shrinkage of input xin by the stretch factor. It ensures that xin ^~ is truly 0.0 only when xin is 0.0.
4. Only the real part of a complex input variable is affected by the PWL. The imaginary part merely gets stretched and scaled.