Template_Lowpass.py

# -*- coding: utf-8 -*-
"""
Created on Thu Sep  3 16:18:47 2020

@author: Marc Bodem

Template for Calling CST from Python
- Lowpass Filter (Design Studio)
- Parameter Sweep to load several sample points
- change 6 parameters
- Obtain S-Parameter values

"""
import sys
sys.path.append(r"C:\Program Files (x86)\CST Studio Suite 2020\AMD64\python_cst_libraries")
import cst
import cst.interface
import cst.results
import numpy as np
import scipy.stats
import time
import shutil

start = time.time()

# Local path to CST project file --> Please adapt
cst_path = r'D:\Documents\Vorlagen\CST_Python_Interface' # path
cst_project = '\S-Parameter Lowpass' # CST project

cst_project_path = cst_path + cst_project + '.cst'
cst_result_folder = cst_path + cst_project + '\Result'


# Delete all old results (if exist)
try:
    shutil.rmtree(cst_result_folder)
except OSError as e:
    print(e)
else:
    print("The results directory is deleted successfully")


# Define random list of unifrom distributed sample points
Nmc = 3 # number of sample points
Nuq = 6 # number of parameters per sample point
means = [6.8, 5.1, 9.0, 1.4, 1.4, 1.3] # mean values for parameters
sample_list = []
for nuq in range(Nuq):
    mu = means[nuq]; uq = 0.2;
    samples_k = scipy.stats.uniform.rvs(mu-uq*mu,2*uq*mu,Nmc)
    sample_list.append(samples_k) 
sample_list = np.array(sample_list).T   


# Define list with frequency points of interest, here 0-7 GHz, Number of calculated points are set to 7001 in CST file, to get the desired frequencies.
freq_range = [0,1,2,3,4,5,6,7]
freq_range_pos = np.array(freq_range)*1000


# Initialize lists with S-parameter results
S_all = []
S_real_all = []
S_imag_all = []
SdB_all = []


# Open CST as software
mycst=cst.interface.DesignEnvironment()

# Open CST Project
mycst1=cst.interface.DesignEnvironment.open_project(mycst,cst_project_path)

#Delete All Sequences before starting to get a fresh file
delete ='Sub Main() \n ParameterSweep.DeleteAllSequences() \nEnd Sub'
mycst1.schematic.execute_vba_code(delete, timeout=None)

for i in range(len(sample_list)):
   #VBA Add Sequence
   createSequence = 'Sub Main () \n ParameterSweep.AddSequence('+str(i)+') \n End Sub' 
   #VBA Add Parameters to Sequence. For each Parameter combination you want to test, create 1 sequence
   add_Para_L1 = 'Sub Main () \n ParameterSweep.AddParameter('+str(i)+',"L1",'+str(True)+','+str(sample_list[i][0])+','+str(sample_list[i][0])+','+str(1)+') \n End Sub'
   add_Para_L2 = 'Sub Main () \n ParameterSweep.AddParameter('+str(i)+',"L2",'+str(True)+','+str(sample_list[i][1])+','+str(sample_list[i][1])+','+str(1)+') \n End Sub'
   add_Para_L3 = 'Sub Main () \n ParameterSweep.AddParameter('+str(i)+',"L3",'+str(True)+','+str(sample_list[i][2])+','+str(sample_list[i][2])+','+str(1)+') \n End Sub'
   add_Para_W1 = 'Sub Main () \n ParameterSweep.AddParameter('+str(i)+',"W1",'+str(True)+','+str(sample_list[i][3])+','+str(sample_list[i][3])+','+str(1)+') \n End Sub'
   add_Para_W2 = 'Sub Main () \n ParameterSweep.AddParameter('+str(i)+',"W2",'+str(True)+','+str(sample_list[i][4])+','+str(sample_list[i][4])+','+str(1)+') \n End Sub'
   add_Para_W3 = 'Sub Main () \n ParameterSweep.AddParameter('+str(i)+',"W3",'+str(True)+','+str(sample_list[i][5])+','+str(sample_list[i][5])+','+str(1)+') \n End Sub'
   
   #excute VBA Code above
   mycst1.schematic.execute_vba_code(createSequence, timeout=None)
   mycst1.schematic.execute_vba_code(add_Para_L1, timeout=None)
   mycst1.schematic.execute_vba_code(add_Para_L2, timeout=None)
   mycst1.schematic.execute_vba_code(add_Para_L3, timeout=None)
   mycst1.schematic.execute_vba_code(add_Para_W1, timeout=None)
   mycst1.schematic.execute_vba_code(add_Para_W2, timeout=None)
   mycst1.schematic.execute_vba_code(add_Para_W3, timeout=None)
   
#Start Solver
solve = 'Sub Main () \n ParameterSweep.Start \nEnd Sub'
mycst1.schematic.execute_vba_code(solve, timeout=None)

#Delete All Sequences
mycst1.schematic.execute_vba_code(delete, timeout=None)

#get Project for results
project = cst.results.ProjectFile(cst_project_path, allow_interactive=True)

#get schamatic
schematic = project.get_schematic()


# Evaluate each sample point in CST
for i in range(len(sample_list)):
    #k = i+1 because run Ids start at 1 and 0 is the current run
    k=i+1
    #get the actual results
    results = schematic.get_result_item('Tasks\\SPara1\\S-Parameters\\S2,1',k)
    #get frequencies
    freqs = results.get_xdata()
    #get S-Parameter values
    S_Para = results.get_ydata()

    # Initialize value list for one MC sample point over all frequency points
    freq_pos = []
    freq = []
    S = []
    SdB = []
    S_real = []
    S_imag = []
    
    
    # Get results for each freq. point of interest from CST
    for j in range(len(freq_range)):
        freq_pos_j = freq_range_pos[j]
        freq_pos.append(freq_pos_j)
        
        freq_value_j = freqs[freq_pos_j]
        freq.append(freq_value_j)
        
        S_real_j = S_Para[freq_pos_j].real
        S_real.append(S_real_j)
        
        S_imag_j = S_Para[freq_pos_j].imag
        S_imag.append(S_imag_j)
        
        S_j=np.sqrt(S_real_j**2+S_imag_j**2)
        S.append(S_j)
        
        S_dB_j = 20*np.log10(S_j)
        SdB.append(S_dB_j)
    
    
    # Add results to the lists for all sample points
    S_all.append(S)
    S_real_all.append(S_real)
    S_imag_all.append(S_imag)
    SdB_all.append(SdB)
    

#close CST
cst.interface.DesignEnvironment.close(mycst) 
    
# Return results
print('\n frequency range in GHz:', freq_range)
print('frequency range as positions in CST:', freq_pos)
print('S-parameter:',S_all)
print('S-parameter (real part):',S_real_all)
print('S-parameter (imag part):',S_imag_all)
print('S-parameter (in dB):',SdB_all)

# Return runtime
end = time.time()
print('\n Runtime: {:5.3f}seconds'.format(end-start))