RFmx and FetchSpectrum using Python

Hello

I'm trying to use RFmx through Python.NET.  The code works until I have try to catch the spectrum using FetchSpectrum():

# create the name of the variable before you pass it to the method .NET

spectrum = RFmxSpecAnMXSpectrum


# This does not work!

specAn.Spectrum.Results.FetchSpectrum (", timeout, spectrum)

Here's the complete code:

import clr

import sys


# location of the assemblies

assy_path = r'C:\Program files (x 86) \National Instruments\MeasurementStudioVS2010\DotNET\Assemblies\Current'

sys. Path.Append (assy_path)


CLR. AddReference ("NationalInstruments.RFmx.SpecAnMX.Fx40")

CLR. AddReference ("NationalInstruments.RFmx.InstrMX.Fx40")


from NationalInstruments import *.

from NationalInstruments.RFmx.InstrMX import *.

from NationalInstruments.RFmx.SpecAnMX import *.


# The VSA settings

resourceName = "5606_slave."

centerFrequency = 10.0e9        # Hz

referenceLevel = - 10            # dBm

externalAttenuation = 0.00      # dB

Timeout = 10                    seconds #.

span = 1.0e + 6                   # Hz

RBW = 100e3

averagingCount = 10


instrSession = RFmxInstrMX(resourceName, '')


# configuration VSA

rbwAuto = RFmxSpecAnMXSpectrumRbwAutoBandwidth.True

rbwFilterType = RFmxSpecAnMXSpectrumRbwFilterType.Gaussian

averagingEnabled = RFmxSpecAnMXSpectrumAveragingEnabled.False

averagingType = RFmxSpecAnMXSpectrumAveragingType.Rms

#specAn = instrSession.GetSpecAnSignalConfiguration ();

specAn = RFmxSpecAnMXExtension.GetSpecAnSignalConfiguration (instrSession)

specAn.ConfigureRF('',centerFrequency,referenceLevel,externalAttenuation)

specAn.Spectrum.Configuration.ConfigureSpan('', span)

specAn.Spectrum.Configuration.ConfigureRbwFilter (", rbwAuto, rbw, rbwFilterType)

specAn.Spectrum.Configuration.ConfigureAveraging (", averagingEnabled, averagingCount, averagingType)

specAn.SelectMeasurements (", RFmxSpecAnMXMeasurementTypes.Spectrum, bool ())

specAn.Commit ("")


# run acquisition

specAn.Initiate('','')


# find the peak power in the spectrum

_, pkAmp, pkFreq, freqRes = specAn.Spectrum.Results.FetchMeasurement (", timeout, float (), float (), float ())

Print "peak power: dBm {:0.2f} to {:0.6f} GHz'.format(pkAmp,pkFreq*1e-9)}}"


"""

A .NET method may require user pass the variable name that it wishes to

change as an argument. Python is not compatible "pass by reference", but the

the variable name must exist in python, before he can be handed over to the .NET method.

The .NET method will simply point to the new instance.


http://nbviewer.IPython.org/GitHub/jonnojohnson/Agilent/BLOB/master/Python_Automation/Python_Automation.ipynb

"""


# create the name of the variable before you pass it to the method .NET

spectrum = RFmxSpecAnMXSpectrum


# This does not work!

specAn.Spectrum.Results.FetchSpectrum (", timeout, spectrum)


instrSession.Close)

Here is the error:

Traceback (most recent call changed):

File "", line 3, in
specAn.Spectrum.Results.FetchSpectrum ("", timeout, spectrum)

ArgumentException: Object of type 'System.RuntimeType' cannot be converted to type ' NationalInstruments.Spectrum'1 [System.Single] & ".
at System.RuntimeType.TryChangeType (Object value, Binder binder, CultureInfo culture, Boolean needsSpecialCast)
at System.Reflection.MethodBase.CheckArguments (Object [] parameters, Binder binder, BindingFlags invokeAttr, CultureInfo culture, sig Signature)
at System.Reflection.RuntimeMethodInfo.InvokeArgumentsCheck (Object obj, BindingFlags invokeAttr, Binder binder, Object [] parameters, CultureInfo culture)
at System.Reflection.RuntimeMethodInfo.Invoke (Object obj, BindingFlags invokeAttr, Binder binder, Object [] parameters, CultureInfo culture)
to Python.Runtime.MethodBinder.Invoke (inst IntPtr, IntPtr args, kw, MethodBase info, methodinfo MethodInfo [] IntPtr)

Any ideas?

Ah! That's about all. Here's what worked:

spectrum = NationalInstruments.Spectrum [System.Single] (0)

_, spectrum is specAn.Spectrum.Results.FetchSpectrum('',timeout,spectrum)

Here is the result and the final code for future reference:

import clr

import sys

Import os

import matplotlib.pyplot as plt

Import numpy as np

# To Program Files Windows environment variable

Program_Files = os.environ ['ProgramFiles (x 86) ""]
assy_path = os.path.join (program_files,
"National Instruments",.
"MeasurementStudioVS2010,"
"DotNET"
"Assemblies."
'Current')

sys. Path.Append (assy_path)

CLR. AddReference ("NationalInstruments.Common")
CLR. AddReference ("NationalInstruments.RFmx.SpecAnMX.Fx40")
CLR. AddReference ("NationalInstruments.RFmx.InstrMX.Fx40")

from NationalInstruments.RFmx.InstrMX import *.
from NationalInstruments.RFmx.SpecAnMX import *.
import NationalInstruments
Import System

# The VSA settings
resourceName = "5606_slave."
centerFrequency = 25.0e9 # Hz
referenceLevel = #-10 dBm
externalAttenuation = # 0.00 dB
Timeout = 10 # seconds
span = 1.0e + 6 # Hz
RBW = 100e3 # Hz
averagingCount = 10

instrSession = RFmxInstrMX(resourceName, '')

# Get the model number
_, Model = instrSession.GetInstrumentModel (", Str())

# configuration VSA
rbwAuto = RFmxSpecAnMXSpectrumRbwAutoBandwidth.True
rbwFilterType = RFmxSpecAnMXSpectrumRbwFilterType.Gaussian
averagingEnabled = RFmxSpecAnMXSpectrumAveragingEnabled.False
averagingType = RFmxSpecAnMXSpectrumAveragingType.Rms
specAn = RFmxSpecAnMXExtension.GetSpecAnSignalConfiguration (instrSession)
specAn.ConfigureRF('',centerFrequency,referenceLevel,externalAttenuation)
specAn.Spectrum.Configuration.ConfigureSpan('', span)
specAn.Spectrum.Configuration.ConfigureRbwFilter (", rbwAuto, rbw, rbwFilterType)
specAn.Spectrum.Configuration.ConfigureAveraging (", averagingEnabled, averagingCount, averagingType)
specAn.SelectMeasurements (", RFmxSpecAnMXMeasurementTypes.Spectrum, bool ())
specAn.Commit ("")

# run acquisition
specAn.Initiate('','')

# get x data
spectrum = NationalInstruments.Spectrum [System.Single] (0)
_, spectrum is specAn.Spectrum.Results.FetchSpectrum('',timeout,spectrum)

# get data
analogwaveform = NationalInstruments.AnalogWaveform [System.Single] (0)
_, analogwaveform is specAn.Spectrum.Results.FetchPowerTrace('',timeout,analogwaveform)

close a session #.
instrSession.Close)

# calculate the frequency and power
startFrequency = spectrum. StartFrequency
frequencyIncrement = spectrum. FrequencyIncrement
sampleCount = spectrum. SampleCount
stopFrequency = startFrequency + frequencyIncrement *(sampleCount+1)
freqArray = np.linspace (startFrequency, stopFrequency, sampleCount)
current = list (analogwaveform. GetRawData())

results of tracking #.
XScale = 1e-3
PLT. Plot ((freqArray-centerFrequency) * XScale, Power, LineWidth = 2.0)
#plt.ylim(referenceLevel-100.,referenceLevel)
PLT.yticks (NP.linspace(referenceLevel-100.,referenceLevel,11))
PLT.xticks(NP.linspace(-span,span,11)/2*XScale)
PLT. XLIM(-span/2*XScale,span/2*XScale)
PLT. Grid (true)
PLT.xlabel (' from center frequency (kHz) ")
PLT.ylabel ('Power (dBm) ")
PLT.title ("{} {:0.6f} GHz spectrum".format(model,centerFrequency*1e-9), fontsize = 'medium')
PLT. Show()

Tags: NI Software

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