Source code for

.. module::
touchstone (:mod:``)

Touchstone class

.. autosummary::
    :toctree: generated/


Functions related to reading/writing touchstones.

.. autosummary::
    :toctree: generated/

import re
import os
import zipfile
import numpy
import numpy as npy

from six.moves import xrange

from ..util import get_fid
from import Network
from ..frequency import Frequency
from import Media, DefinedGammaZ0
from .. import mathFunctions as mf

[docs]class Touchstone: """ class to read touchstone s-parameter files The reference for writing this class is the draft of the Touchstone(R) File Format Specification Rev 2.0 [#]_ and Touchstone(R) File Format Specification Version 2.0 [##]_ .. [#] .. [##] """
[docs] def __init__(self, file): """ constructor Parameters ------------- file : str or file-object touchstone file to load Examples --------- From filename >>> t = rf.Touchstone('network.s2p') From file-object >>> file = open('network.s2p') >>> t = rf.Touchstone(file) """ fid = get_fid(file) filename = ## file name of the touchstone data file self.filename = filename ## file format version. # Defined by default to 1.0, since version number can be omitted in V1.0 format self.version = '1.0' ## comments in the file header self.comments = None ## unit of the frequency (Hz, kHz, MHz, GHz) self.frequency_unit = None ## number of frequency points self.frequency_nb = None ## s-parameter type (S,Y,Z,G,H) self.parameter = None ## s-parameter format (MA, DB, RI) self.format = None ## reference resistance, global setup self.resistance = None ## reference impedance for each s-parameter self.reference = None ## numpy array of original s-parameter data self.sparameters = None ## numpy array of original noise data self.noise = None ## kind of s-parameter data (s1p, s2p, s3p, s4p) self.rank = None ## Store port names in a list if they exist in the file self.port_names = None self.comment_variables=None self.load_file(fid)
[docs] def load_file(self, fid): """ Load the touchstone file into the interal data structures """ filename=self.filename # Check the filename extension. # Should be .sNp for Touchstone format V1.0, and .ts for V2 extension = filename.split('.')[-1].lower() if (extension[0] == 's') and (extension[-1] == 'p'): # sNp # check if N is a correct unmber try: self.rank = int(extension[1:-1]) except (ValueError): raise (ValueError("filename does not have a s-parameter extension. It has [%s] instead. please, correct the extension to of form: 'sNp', where N is any integer." %(extension))) elif extension == 'ts': pass else: raise Exception('Filename does not have the expected Touchstone extension (.sNp or .ts)') linenr = 0 values = [] while (1): linenr +=1 line = fid.readline() if not type(line) == str: line = line.decode("ascii") # for python3 zipfile compatibility if not line: break # store comments if they precede the option line line = line.split('!',1) if len(line) == 2: if not self.parameter: if self.comments == None: self.comments = '' self.comments = self.comments + line[1] elif line[1].startswith(' Port['): try: port_string, name = line[1].split('=', 1) #throws ValueError on unpack name = name.strip() garbage, index = port_string.strip().split('[', 1) #throws ValueError on unpack index = int(index.rstrip(']')) #throws ValueError on not int-able if index > self.rank or index <= 0: print("Port name {0} provided for port number {1} but that's out of range for a file with extension s{2}p".format(name, index, self.rank)) else: if self.port_names is None: #Initialize the array at the last minute self.port_names = [''] * self.rank self.port_names[index - 1] = name except ValueError as e: print("Error extracting port names from line: {0}".format(line)) # remove the comment (if any) so rest of line can be processed. # touchstone files are case-insensitive line = line[0].strip().lower() # skip the line if there was nothing except comments if len(line) == 0: continue # grab the [version] string if line[:9] == '[version]': self.version = line.split()[1] continue # grab the [reference] string if line[:11] == '[reference]': # The reference impedances can be span after the keyword # or on the following line self.reference = [ float(r) for r in line.split()[2:] ] if not self.reference: line = fid.readline() self.reference = [ float(r) for r in line.split()] continue # grab the [Number of Ports] string if line[:17] == '[number of ports]': self.rank = int(line.split()[-1]) continue # grab the [Number of Frequencies] string if line[:23] == '[number of frequencies]': self.frequency_nb = line.split()[-1] continue # skip the [Network Data] keyword if line[:14] == '[network data]': continue # skip the [End] keyword if line[:5] == '[end]': continue # the option line if line[0] == '#': toks = line[1:].strip().split() # fill the option line with the missing defaults toks.extend(['ghz', 's', 'ma', 'r', '50'][len(toks):]) self.frequency_unit = toks[0] self.parameter = toks[1] self.format = toks[2] self.resistance = toks[4] if self.frequency_unit not in ['hz', 'khz', 'mhz', 'ghz']: print('ERROR: illegal frequency_unit [%s]', self.frequency_unit) # TODO: Raise if self.parameter not in 'syzgh': print('ERROR: illegal parameter value [%s]', self.parameter) # TODO: Raise if self.format not in ['ma', 'db', 'ri']: print('ERROR: illegal format value [%s]', self.format) # TODO: Raise continue # collect all values without taking care of there meaning # we're seperating them later values.extend([ float(v) for v in line.split() ]) # let's do some post-processing to the read values # for s2p parameters there may be noise parameters in the value list values = numpy.asarray(values) if self.rank == 2: # the first frequency value that is smaller than the last one is the # indicator for the start of the noise section # each set of the s-parameter section is 9 values long pos = numpy.where(numpy.sign(numpy.diff(values[::9])) == -1) if len(pos[0]) != 0: # we have noise data in the values pos = pos[0][0] + 1 # add 1 because diff reduced it by 1 noise_values = values[pos*9:] values = values[:pos*9] self.noise = noise_values.reshape((-1,5)) if len(values)%(1+2*(self.rank)**2) != 0 : # incomplete data line / matrix found raise AssertionError # reshape the values to match the rank self.sparameters = values.reshape((-1, 1 + 2*self.rank**2)) # multiplier from the frequency unit self.frequency_mult = {'hz':1.0, 'khz':1e3, 'mhz':1e6, 'ghz':1e9}.get(self.frequency_unit) # set the reference to the resistance value if no [reference] is provided if not self.reference: self.reference = [self.resistance] * self.rank
[docs] def get_comments(self, ignored_comments = ['Created with skrf']): """ Returns the comments which appear anywhere in the file. Comment lines containing ignored comments are removed. By default these are comments which contain special meaning withing skrf and are not user comments. """ processed_comments = '' if self.comments is None: self.comments = '' for comment_line in self.comments.split('\n'): for ignored_comment in ignored_comments: if ignored_comment in comment_line: comment_line = None if comment_line: processed_comments = processed_comments + comment_line + '\n' return processed_comments
[docs] def get_comment_variables(self): ''' convert hfss variable comments to a dict of vars:(numbers,units) ''' comments = self.comments p1 = re.compile('\w* = \w*') p2 = re.compile('\s*(\d*)\s*(\w*)') var_dict = {} for k in re.findall(p1, comments): var, value = k.split('=') var=var.rstrip() try: var_dict[var] = p2.match(value).groups() except: pass return var_dict
[docs] def get_format(self, format="ri"): """ returns the file format string used for the given format. This is useful to get some information. """ if format == 'orig': frequency = self.frequency_unit format = self.format else: frequency = 'hz' return "%s %s %s r %s" %(frequency, self.parameter, format, self.resistance)
[docs] def get_sparameter_names(self, format="ri"): """ generate a list of column names for the s-parameter data The names are different for each format. posible format parameters: ri, ma, db, orig (where orig refers to one of the three others) returns a list of strings. """ names = ['frequency'] if format == 'orig': format = self.format ext1, ext2 = {'ri':('R','I'),'ma':('M','A'), 'db':('DB','A')}.get(format) for r1 in xrange(self.rank): for r2 in xrange(self.rank): names.append("S%i%i%s"%(r1+1,r2+1,ext1)) names.append("S%i%i%s"%(r1+1,r2+1,ext2)) return names
[docs] def get_sparameter_data(self, format='ri'): """ get the data of the s-parameter with the given format. supported formats are: orig: unmodified s-parameter data ri: data in real/imaginary ma: data in magnitude and angle (degree) db: data in log magnitute and angle (degree) Returns a list of numpy.arrays """ ret = {} if format == 'orig': values = self.sparameters else: values = self.sparameters.copy() # use frequency in hz unit values[:,0] = values[:,0]*self.frequency_mult if (self.format == 'db') and (format == 'ma'): values[:,1::2] = 10**(values[:,1::2]/20.0) elif (self.format == 'db') and (format == 'ri'): v_complex = ((10**values[:,1::2]/20.0) * numpy.exp(1j*numpy.pi/180 * values[:,2::2])) values[:,1::2] = numpy.real(v_complex) values[:,2::2] = numpy.imag(v_complex) elif (self.format == 'ma') and (format == 'db'): values[:,1::2] = 20*numpy.log10(values[:,1::2]) elif (self.format == 'ma') and (format == 'ri'): v_complex = (values[:,1::2] * numpy.exp(1j*numpy.pi/180 * values[:,2::2])) values[:,1::2] = numpy.real(v_complex) values[:,2::2] = numpy.imag(v_complex) elif (self.format == 'ri') and (format == 'ma'): v_complex = numpy.absolute(values[:,1::2] + 1j* self.sparameters[:,2::2]) values[:,1::2] = numpy.absolute(v_complex) values[:,2::2] = numpy.angle(v_complex)*(180/numpy.pi) elif (self.format == 'ri') and (format == 'db'): v_complex = numpy.absolute(values[:,1::2] + 1j* self.sparameters[:,2::2]) values[:,1::2] = 20*numpy.log10(numpy.absolute(v_complex)) values[:,2::2] = numpy.angle(v_complex)*(180/numpy.pi) for i,n in enumerate(self.get_sparameter_names(format=format)): ret[n] = values[:,i] return ret
[docs] def get_sparameter_arrays(self): """ Returns the s-parameters as a tuple of arrays, where the first element is the frequency vector (in Hz) and the s-parameters are a 3d numpy array. The values of the s-parameters are complex number. usage: f,a = self.sgetparameter_arrays() s11 = a[:,0,0] """ v = self.sparameters if self.format == 'ri': v_complex = v[:,1::2] + 1j* v[:,2::2] elif self.format == 'ma': v_complex = (v[:,1::2] * numpy.exp(1j*numpy.pi/180 * v[:,2::2])) elif self.format == 'db': v_complex = ((10**(v[:,1::2]/20.0)) * numpy.exp(1j*numpy.pi/180 * v[:,2::2])) if self.rank == 2 : # this return is tricky; it handles the way touchtone lines are # in case of rank==2: order is s11,s21,s12,s22 return (v[:,0] * self.frequency_mult, numpy.transpose(v_complex.reshape((-1, self.rank, self.rank)),axes=(0,2,1))) else: return (v[:,0] * self.frequency_mult, v_complex.reshape((-1, self.rank, self.rank)))
[docs] def get_noise_names(self): """ TODO: NIY """ TBD = 1
[docs] def get_noise_data(self): """ TODO: NIY """ TBD = 1 noise_frequency = noise_values[:,0] noise_minimum_figure = noise_values[:,1] noise_source_reflection = noise_values[:,2] noise_source_phase = noise_values[:,3] noise_normalized_resistance = noise_values[:,4]
[docs] def is_from_hfss(self): ''' Check if the Touchstone file has been produced by HFSS Returns ------------ status : boolean True if the Touchstone file has been produced by HFSS False otherwise ''' if self.comments is None: return False if 'exported from hfss' in str.lower(self.comments): return True return False
[docs] def get_gamma_z0(self): ''' Extracts Z0 and Gamma comments from touchstone file (is provided) Returns -------- gamma : complex numpy.ndarray complex propagation constant z0 : numpy.ndarray complex port impedance ''' def line2ComplexVector(s): return mf.scalar2Complex(npy.array([k for k in s.strip().split(' ') if k != ''][self.rank*-2:], dtype='float')) with open(self.filename) as f: gamma, z0 = [],[] for line in f: # HFSS adds gamma and z0 data in .sNp files using comments. # NB : Each line describe gamma and z0 up to 4 ports # for N > 4, gamma and z0 are given by additional lines if '! Gamma' in line: _line = line.replace('! Gamma', '').rstrip() # case of Nport > 4 for _ in range(self.rank // 5): _line += next(f).replace('!', '').rstrip() gamma.append(line2ComplexVector(_line)) if '! Port Impedance' in line: _line = line.replace('! Port Impedance', '').rstrip() # case of Nport > 4 for _ in range(self.rank // 5): _line += next(f).replace('!', '').rstrip() z0.append(line2ComplexVector(_line)) # If the file does not contain valid port impedance comments, set to default one if len(z0) == 0: z0 = self.resistance #raise ValueError('Touchstone does not contain valid gamma, port impedance comments') return npy.array(gamma), npy.array(z0)
[docs]def hfss_touchstone_2_gamma_z0(filename): ''' Extracts Z0 and Gamma comments from touchstone file Takes a HFSS-style touchstone file with Gamma and Z0 comments and extracts a triplet of arrays being: (frequency, Gamma, Z0) Parameters ------------ filename : string the HFSS-style touchstone file Returns -------- f : numpy.ndarray frequency vector (in Hz) gamma : complex numpy.ndarray complex propagation constant z0 : numpy.ndarray complex port impedance Examples ---------- >>> f,gamm,z0 = rf.hfss_touchstone_2_gamma_z0('line.s2p') ''' ntwk = Network(filename) return ntwk.frequency.f, ntwk.gamma, ntwk.z0
[docs]def hfss_touchstone_2_media(filename, f_unit='ghz'): ''' Creates a :class:`` object from a a HFSS-style touchstone file with Gamma and Z0 comments Parameters ------------ filename : string the HFSS-style touchstone file f_unit : ['hz','khz','mhz','ghz'] passed to f_unit parameters of Frequency constructor Returns -------- my_media : object the transmission line model defined by the gamma, and z0 comments in the HFSS file. Examples ---------- >>> port1_media, port2_media = rf.hfss_touchstone_2_media('line.s2p') See Also --------- hfss_touchstone_2_gamma_z0 : returns gamma, and z0 ''' ntwk = Network(filename) freq = ntwk.frequency gamma = ntwk.gamma z0 = ntwk.z0 media_list = [] for port_n in range(gamma.shape[1]): media_list.append(\ DefinedGammaZ0( frequency = freq, gamma = gamma[:, port_n], z0 = z0[:, port_n] ) ) return media_list
[docs]def hfss_touchstone_2_network(filename, f_unit='ghz'): ''' Creates a :class:`~skrf.Network` object from a a HFSS-style touchstone file Parameters ------------ filename : string the HFSS-style touchstone file f_unit : ['hz','khz','mhz','ghz'] passed to f_unit parameters of Frequency constructor Returns -------- my_network : skrf.Network object the n-port network model Examples ---------- >>> my_network = rf.hfss_touchstone_2_network('DUT.s2p') See Also --------- hfss_touchstone_2_gamma_z0 : returns gamma, and z0 ''' my_network = Network(file=filename, f_unit=f_unit) return(my_network)
def read_zipped_touchstones(ziparchive, dir=""): """ similar to, which works for directories but only for touchstones in ziparchives Parameters ---------- ziparchive : zipfile.ZipFile an zip archive file, containing touchstone files and open for reading dir : str the directory of the ziparchive to read networks from, default is "" which reads only the root directory Returns ------- dict """ networks = dict() for fname in ziparchive.namelist(): # type: str directory, filename = os.path.split(fname) if dir == directory and fname[-4:].lower() in (".s1p", ".s2p", ".s3p", ".s4p"): network = Network.zipped_touchstone(fname, ziparchive) networks[] = network return networks