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PyLab-VCO.php    11107 Bytes    04-08-2022 11:51:33


Python Lab Experiments - THE VCO Testbench


Arduino Lab Automation Example / Exercise




Arduino and Python in da Lab




✈ Minimum Equipment List (MEL)




DEVICESREMARKS
Power SupplyPower to supply the VCO, e.g. Supplymod
Power Supplysets the Tuning Voltage for VCO, e.g. Samroimod
Powermetermeasures the VCO Output Power, e.g. Levelmod
Frequency Countermeasures the VCO Frequency, e.g. Countermod


We used only Arduino™ based devices here, as this simplifies the Python Script.
(PyVISA is covered in a later exercise).




✈ Goal • learning content




• Control multiple devices in a loop
• Plot graphs with multiple axis
• Calculate the VCO gain, Kvco [MHz/V], to be used for PLL loop filter dimensioning.




🐍 The Python Script




# -*- coding: utf-8 -*-
"""
Created on Thu Jun 23 07:16:00 2022

@author: r_57, cp-9

ETH Zürich, Quantumoptics 2022
"""

import serial
import time
import matplotlib.pyplot as plt


supply = serial.Serial(port='COM10', baudrate=115200, timeout=.1)
samroi = serial.Serial(port='COM4', baudrate=115200, timeout=.1)
level = serial.Serial(port='COM9', baudrate=115200, timeout=.1)
counter = serial.Serial(port='COM11', baudrate=115200, timeout=.1)
time.sleep(5)

command = 0
befehl = "VSET:"
r = []
u = []
p = []
s = []
x = []
y = []
Vstart = 0.0           				#set min voltage
voltage = Vstart
Vstop = 15.0             			#set max voltage
xlabel = ("Tuning Voltage [V]")    	#define name of the x-axis
ylabel = ("Level [dBm]")    		#define name of the y-axis
plotname = ("JTOS-150") 			#define name of the plot
dBmmin = -60              			#set min 
dBmmax = 10  
poweroffset = 10
rising = 0.1
frequency = 0
frequenc = 0

def write_read_Supplymod(x):
    supply.write(x.encode('utf-8'))
    time.sleep(0.05)
    data = []
    line = (supply.readline())
    while len(line) > 0:
        data.append(line)
        line = supply.readline()
        line = line.decode('utf-8')
    return data

def write_read_Samroimod(x):
    samroi.write(x.encode('utf-8'))
    time.sleep(0.05)
    data = []
    line = (samroi.readline())
    while len(line) > 0:
        data.append(line)
        line = samroi.readline()
        line = line.decode('utf-8')
    return data

def write_read_Levelmod(x):
    level.write(x.encode('utf-8'))
    time.sleep(0.05)
    data = []
    line = (level.readline())
    while len(line) > 0:
        data.append(line)
        line = level.readline()
        line = line.decode('utf-8')
    return data

def write_read_Countermod(x):
    counter.write(x.encode('utf-8'))
    time.sleep(0.05)
    data = []
    line = (counter.readline())
    while len(line) > 0:
        data.append(line)
        line = counter.readline()
        line = line.decode('utf-8')
    return data

def readempty(x):
        time.sleep(1)
        x = b'ava'
        while x != b'':
            x = supply.readline()
            #print(x)
            
        x = b'ava'
        while x != b'':
            x = samroi.readline()
            #print(x)
            
        x = b'ava'
        while x != b'':
            x = level.readline()
            #print(x)
            
        x = b'ava'
        while x != b'':
            x = counter.readline()
            #print(x)
        
        supply.readline()
        samroi.readline()
        level.readline()
        level.readline()
        counter.readline()
        

try:
    readempty(x)
    freq = str(write_read_Countermod('F?'))
    freq = freq[3:-9]
    frequency = (float(freq)/1000000)  
    write_read_Levelmod('*SP1!')
    
    while voltage <= Vstop:
        
        if frequency >= 76:
            write_read_Levelmod('*SP2!')
            
        if frequency >= 126:
            write_read_Levelmod('*SP3!')
            
        frequenc = frequency
        
            
        write_read_Samroimod(befehl + str(voltage))
        time.sleep(5)
        
        dBm = str((write_read_Levelmod('*LVL?')))
        dBm = str((write_read_Levelmod('*LVL?')))
        while dBm == ('[]'):
            dBm = str((write_read_Levelmod('*LVL?')))
            
            
        freq = str(write_read_Countermod('F?'))
        
        
        dBm = dBm[3:-6]                  #throw away unnessecary characters
        dBm = float(dBm) + poweroffset
        freq = freq[3:-9]
        
        
        frequency = (float(freq)/1000000)
        
        increase = (frequency - frequenc) / rising
        
       
        
        print(increase)
        print(voltage)
        print(frequency)
        print(dBm)
        print()
        

        r.append(voltage)   			#create list measurement values
        u.append(dBm)
        p.append(frequency)
        s.append(increase)
        
        voltage += rising              	#increase voltage
        
                   
            
        
    x = [float(i) for i in r]   		#string to float conversion
    y1 = [float(i) for i in u]    
    y2 = [float(i) for i in p]
    y3 = [float(i) for i in s]

   
    
    #####Plot erstellen:#####
    
    fig, ax1 = plt.subplots()

    ax1.set_xlabel('Tuning Voltage [V]')
    ax1.set_ylabel('Frequency [MHz]', color ='green')
    ax1.plot(x, y2, color= 'green')
    ax1.plot(x, y3, color = 'blue')

    ax2 = ax1.twinx()  
    ax2.set_ylabel('Power [dBm]', color ='red')  
    ax2.plot(x, y1, color = 'red')
    

    fig.tight_layout()
    plt.show()
               
    
        
finally:
    print('finally')
    supply.close()
    write_read_Samroimod('VSET:0.0')
    samroi.close()
    level.close()
    counter.close()
  




✈ The Result : JTOS-150




Python Lab Experiments - THE VCO Testbench


Horizontal : Tuning Voltage
Red Trace : Pwer [dBm], left
Green Trace : Frequency [MHz], right
Blue Trace : VCO Gain [MHz/V], right




✈ Share your thoughts



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