Perform a Source and Receiver Power Cal using SCPI

'Session to VISA Default Resource Manager

Private defRM As Long

'Session to VNA

Private viPNA As Long

'VISA function status return code

Private status As Long

Private Sub Form_Load()

defRM = 0

End Sub

Private Sub cmdRun_Click()

' String to receive data from the VNA.

' Dimensioned large enough to receive scalar comma-delimited values

' for 21 frequency points (20 ASCII characters per point)

Dim strReply As String * 420

Dim strStimulus, strCalValue

Dim strResult As String

' Open the VISA default resource manager

status = viOpenDefaultRM(defRM)

If (status < VI_SUCCESS) Then HandleVISAError

' Open a session (viPNA) to the VNA at "address 16" on the VISA

' interface configured as "GPIB1" on this PC.  This could be a

' VISA LAN Client pointing to the SICL LAN Server on the VNA, or

' an actual GPIB interface on this PC connected to the VNA GPIB

' (in which case the power meter would need to be connected to a

' different GPIB interface on the VNA, such as the Keysight 82357A

' USB-to-GPIB).

status = viOpen(defRM, "GPIB0::16::INSTR", 0, 0, viPNA)

If (status < VI_SUCCESS) Then HandleVISAError

' Set the number of sweep points to 21 on Channel 1.

status = myGPIBWrite(viPNA, "SENS1:SWE:POIN 21")

If (status < VI_SUCCESS) Then HandleVISAError

' Specify the GPIB address of the power meter

' that will be used in performing the calibration.

status = myGPIBWrite(viPNA, "SYST:COMM:GPIB:PMET:ADDR 13")

If (status < VI_SUCCESS) Then HandleVISAError

' Turn use of the loss table OFF (this assumes there is

' virtually no loss in the RF path to the power sensor

' due to a splitter, coupler or adapter).

status = myGPIBWrite(viPNA, "SOUR:POW:CORR:COLL:TABL:LOSS OFF")

If (status < VI_SUCCESS) Then HandleVISAError

' Turn frequency checking OFF (so one power sensor is used for the entire cal

' acquisition sweep regardless of frequency span).

status = myGPIBWrite(viPNA, "SOUR:POW:CORR:COLL:FCH OFF")

If (status < VI_SUCCESS) Then HandleVISAError

' Specify a nominal power accuracy tolerance (NTOLerance) in dB for the calibration,

' and the maximum number (COUNt) of iterations to adjust power at each point,

' attempting to achieve within tolerance of the desired power.  If at any stimulus

' point the power fails to reach within the set tolerance of the desired power

' after the maximum number of iterations, the power at that point will be set to the

' value determined by the last iteration (the Source Power Cal dialog box will

' indicate the FAIL, but we can still apply the cal if desired when it's complete).

' Each iteration is based upon a SETTLED power reading (see comments preceding the

' next two commands below).

status = myGPIBWrite(viPNA, "SOUR1:POW2:CORR:COLL:ITER:NTOL 0.1")

If (status < VI_SUCCESS) Then HandleVISAError

status = myGPIBWrite(viPNA, "SOUR1:POW2:CORR:COLL:ITER:COUN 3")

If (status < VI_SUCCESS) Then HandleVISAError

' The worst-case window of power uncertainty (for a calibration which meets

' tolerance) is the sum of the iteration tolerance and the power meter settling

' tolerance (which is described below).

' At each stimulus point, the VNA takes power meter readings and determine when

' they have settled by comparing the magnitude difference between consecutive

' readings versus a nominal dB tolerance limit (NTOLerance) on that magnitude

' difference.  When consecutive readings are within tolerance of each other, or

' if they are not within tolerance but we've taken a maximum number of readings

' (COUNt), the VNA does a weighted average of the readings taken at that stimulus

' point and that is considered our settled power reading.

status = myGPIBWrite(viPNA, "SOUR1:POW2:CORR:COLL:AVER:NTOL 0.1")

If (status < VI_SUCCESS) Then HandleVISAError

status = myGPIBWrite(viPNA, "SOUR1:POW2:CORR:COLL:AVER:COUN 5")

If (status < VI_SUCCESS) Then HandleVISAError

' Specify if the cal power level is offset (positive value for a gain, negative

' value for a loss) from the VNA port power setting on the channel when no source

' power cal is active.  This is to account for components between the VNA test

' port and cal reference plane.  In this example, we will calibrate at the VNA

' test port, so there is no offset (it is zero).

status = myGPIBWrite(viPNA, "SOUR1:POW2:CORR:OFFS 0 DB")

If (status < VI_SUCCESS) Then HandleVISAError

' Show the source power cal dialog during the source power cal acquisition.

' (this is the default, so this command is only necessary if this setting

' may have been changed beforehand, perhaps by another program).

status = myGPIBWrite(viPNA, "SOUR1:POW2:CORR:COLL:DISP ON")

If (status < VI_SUCCESS) Then HandleVISAError

' Clear the VNA’s SCPI status registers because we are going to be monitoring

' the event status register to detect when the OPC bit gets set indicating

' the cal ACQuire completed.

status = myGPIBWrite(viPNA, "*CLS")

If (status < VI_SUCCESS) Then HandleVISAError

' Setting the I/O timeout value to 6000 milliseconds (6 seconds), because the

' VNA may take up to that amount of time to respond to some commands/queries

' while the cal ACQuire is progressing.

status = viSetAttribute(viPNA, VI_ATTR_TMO_VALUE, 6000)

If (status < VI_SUCCESS) Then HandleVISAError

' Specify the method (type of device) that will be used to perform the cal.

' Choose from power meter (PMETer), power meter and receiver (PMReceiver)

' or just receiver (RECeiver).

' PMReceiver uses the power meter for the first iteration of each point and

' the VNA's reference receiver for subsequent iterations, so is much faster

' than using power meter only.  But the power meter accounts for compression

' when calibrating at the output of an active device, whereas the reference

' receiver cannot unless it is coupled to the cal reference plane (on a VNA

' which allows direct access to the receivers).

' Perform the source power cal acquisition sweep using the sensor attached to

' Channel A of the power meter (asking for an OPC reply when it’s done).  This

' assumes that the power sensor is already connected to Port 2 of the VNA.

' We'll put up an hourglass cursor while waiting for the acquire to complete.

Screen.MousePointer = vbHourglass

status = myGPIBWrite(viPNA, "SOUR1:POW:CORR:COLL:ACQ PMET,'ASEN','Port 2',ASYNchronous;*OPC")

If (status < VI_SUCCESS) Then HandleVISAError

' Other valid selections would be the following:

‘ This mode uses Power Meter and Reference Receiver

'status = myGPIBWrite(viPNA, "SOUR1:POW:CORR:COLL:ACQ PMR,'BSEN','Port 2',ASYN;*OPC")

' This mode uses VNA receiver only (no power meter)

'status = myGPIBWrite(viPNA, "SOUR1:POW:CORR:COLL:ACQ REC,'b1','Port 2',ASYN;*OPC")

' Polling in a loop to detect when the OPC bit (bit 0, weight value 1) gets

' set in the Event Status Register indicating the ACQuire finished.  In this

' type of loop is where you could do other operations in-between the polling

' (like having your program’s user-interface still respond to user input).

' If instead of Visual Basic you are programming in C or C++, as an

' alternative to having a polling loop like this, you could set up an SRQ

' handling function in your program (for example, see the documentation

' supplied with your vendor’s implementation of VISA on how to register for

' callback when an SRQ event occurs).

Do

   status = myGPIBWrite(viPNA, "*ESR?")

   If (status < VI_SUCCESS) Then HandleVISAError

   status = myGPIBRead(viPNA, strReply)

   If (status < VI_SUCCESS) Then HandleVISAError

   esrByte = CByte(strReply)

Loop While (esrByte And 1) = 0

' Change mouse cursor from hourglass back to normal

Screen.MousePointer = vbDefault

' Conclude the calibration.  This applies the cal data to VNA channel memory,

' and turns the correction ON for Port 2 on Channel 1,

' but does NOT save the calibration.

status = myGPIBWrite(viPNA, "SOUR1:POW2:CORR:COLL:SAVE")

If (status < VI_SUCCESS) Then HandleVISAError

' At this point, if you choose to save the instrument state as a ".CST" file,

' the calibration will be saved with the instrument state in that file.

' Prepare for doing data transfer in ASCII format.

status = myGPIBWrite(viPNA, "FORM:DATA ASCII")

If (status < VI_SUCCESS) Then HandleVISAError

' Read the stimulus values from Channel 1.

status = myGPIBWrite(viPNA, "SENS1:X?")

If (status < VI_SUCCESS) Then HandleVISAError

status = myGPIBRead(viPNA, strReply)

If (status < VI_SUCCESS) Then HandleVISAError

' Tokenize the reply string into an array containing the values

strStimulus = Split(strReply, ",")

' Read the source power correction data.

status = myGPIBWrite(viPNA, "SOUR1:POW2:CORR:DATA?")

If (status < VI_SUCCESS) Then HandleVISAError

status = myGPIBRead(viPNA, strReply)

If (status < VI_SUCCESS) Then HandleVISAError

' Tokenize the reply string into an array containing the values

strCalValue = Split(strReply, ",")

' Print the data using a message box (here, Chr returns the ASCII characters

' for Tab (9) and Linefeed (10)).

strResult = "Stimulus" & Chr(9) & Chr(9) & "Cal Value" & Chr(10)

For i = 0 To UBound(strStimulus)

strResult = strResult & Val(strStimulus(i)) & Chr(9) & Val(strCalValue(i)) & Chr(10)

Next

MsgBox strResult

End Sub

Private Function myGPIBWrite(ByVal viHandle As Long, ByVal strOut As String) As Long

' The "+ Chr$(10)" appends an ASCII linefeed character to the

' output, for terminating the write transaction.

myGPIBWrite = viVPrintf(viHandle, strOut + Chr$(10), 0)

End Function

Private Function myGPIBRead(ByVal viHandle As Long, strIn As String) As Long

myGPIBRead = viVScanf(viHandle, "%t", strIn)

End Function

Sub HandleVISAError()

Dim strVisaErr As String * 200

Call viStatusDesc(defRM, status, strVisaErr)

MsgBox "*** Error : " + strVisaErr, vbExclamation

' Close the resource manager session (which also closes

' the session to the VNA).

If defRM <> 0 Then Call viClose(defRM)

End

End Sub

Public Sub Wait(ByVal mS_delay As Long)

Dim t0 As Single

t0 = Timer

Do While Timer - t0 < mS_delay / 1000

Dim dummy As Integer

dummy = DoEvents() ' if we cross midnight, back up one day

If Timer < t0 Then t0 = t0 - 86400

Loop

End Sub