Touchstone

Reads Touchstone files into AxisArrays. Supports Sonnet parameter sweeps.

What's a Touchstone file?

The gory details:

• Touchstone v1.1 specification
• Touchstone v2.0 specification

Usage

To load a Touchstone file with extension .s1p, .s2p, .s3p, etc. into an AxisArray, it could not be any easier:

julia> using Touchstone, FileIO, AxisArrays

julia> A = load(joinpath(Pkg.dir("Touchstone"), "test", "paramsweep", "BusResonator_17_param01.s2p"))
6-dimensional AxisArray{Float64,6,...} with axes:
    :format, Symbol[:mag, :angle]
    :parameter, Symbol[:S]
    :to, Base.OneTo(2)
    :from, Base.OneTo(2)
    :f, [6.0, 6.05, 6.1, 6.15, 6.2, 6.25, 6.3, 6.35, 6.4, 6.45  …  15.55, 15.6, 15.65, 15.7, 15.75, 15.8, 15.85, 15.9, 15.95, 16.0]
    :BusLengthControl, [100.0]
And data, a 2×1×2×2×798×1 Array{Float64,6}:
[:, :, 1, 1, 1, 1] =
  1.0  
 -3.613

[:, :, 2, 1, 1, 1] =
  2.039e-5
 75.309

...

Notice how some parameter appeared as a fourth dimension? That parameter was included as a comment by Sonnet when the .s2p file was exported. Here's the fun part. If you have a parameter sweep or even a multi-parameter sweep saved as a collection of .s2p files in a folder, for example as exported by Sonnet, you can use loadset to import everything into one AxisArray:

julia> loadset(joinpath(Pkg.dir("Touchstone"), "test", "paramsweep"))
6-dimensional AxisArray{Float64,6,...} with axes:
    :format, Symbol[:mag, :angle]
    :parameter, Symbol[:S]
    :to, [1, 2]
    :from, [1, 2]
    :f, [6.0, 6.05, 6.1, 6.15, 6.2, 6.25, 6.26015, 6.27006, 6.27975, 6.28922  …  15.5886, 15.6, 15.65, 15.7, 15.75, 15.8, 15.85, 15.9, 15.95, 16.0]
    :BusLengthControl, [100.0, 600.0, 1100.0, 1600.0, 2100.0, 2600.0, 3100.0, 3600.0, 4100.0, 4600.0, 5100.0]
And data, a 2×1×2×2×8561×11 Array{Float64,6}:
[:, :, 1, 1, 1, 1] =
  1.0  
 -3.613

[:, :, 2, 1, 1, 1] =
  2.039e-5
 75.309   

...

Note that sometimes Sonnet will save files with different frequency axes in one parameter sweep depending on what adaptive band synthesis chose to do. If this happens, all of the frequency axes are merged, and missing values are interpolated. Linear() or Constant() (nearest-neighbor) interpolation may be chosen using the interp keyword argument in loadset.

The parameter is kept as a separate axis so that you can load S-parameters, Y-parameters, Z-parameters and the like into one AxisArray.

You can convert between the various formats (RealImag, dBAngle, MagAngle):

julia> reformat(RealImag, A)
6-dimensional AxisArray{Float64,6,...} with axes:
    :parameter, Symbol[:S]
    :to, Base.OneTo(2)
    :from, Base.OneTo(2)
    :f, [6.0, 6.05, 6.1, 6.15, 6.2, 6.25, 6.3, 6.35, 6.4, 6.45  …  15.55, 15.6, 15.65, 15.7, 15.75, 15.8, 15.85, 15.9, 15.95, 16.0]
    :BusLengthControl, [100.0]
    :format, Symbol[:real, :imag]
And data, a 1×2×2×798×1×2 Array{Float64,6}:
[:, :, 1, 1, 1, 1] =
 0.998012  5.17103e-6

[:, :, 2, 1, 1, 1] =
 5.17103e-6  0.900621

...

Take care as the axes are reordered, so it is better to use the special Axis-based indexing (e.g. A[Axis{:format}(:mag), ...]).

Once you have imported the data and formatted it to your liking then you can:

• Plot heatmaps with, for example, one axis as frequency and one axis as a swept parameter, etc.
• Do peak-finding as a function of a swept parameter
• Do other fun things

Caveats

Touchstone v2 is not yet supported.