Rohde & Schwarz R&S FSP Series, Operating Manual

Page: 759 / 796

Operating Manual 1164.4556.12 - 06 7.25
R&S FSP Remote Control – Programming Examples
More Complex Programming Examples
7.3.9 Measuring the Magnitude and Phase of a Signal
(I/Q Data Acquisition)
Due to the R&S FSP's internal architecture, it is capable of measuring and output-
ting the magnitude and phase of a signal in addition to its power values. This opens
up a variety of possibilities for more in-depth analysis (FFT, demodulation, etc.).
For details on signal processing and the relation between sampling rate and maxi-
mum bandwidth refer to chapter
6 , section “TRACe:IQ Subsystem” on page 6.238 .
The following maximum bandwidths are possible in this measurement depending on
the selected sampling rate:
The following example shows the steps necessary to collect data at a predefined
sampling rate and read it from the I/Q memory.
Data is output in the form of voltage values referring to the analyzer input.
Data can be read in binary or ASCII format.
In binary format, the length information carried in the message header is evaluated
and used for calculating the x-axis values.
In ASCII format, only a list of voltage values is output.
Binary data is read in three steps:
1. The number of digits carrying the length information is read.
2. The length information itself is read.
3. The trace data is read.
This procedure is necessary with programming languages like Visual Basic which
support only structures of identical data types (arrays), whereas the binary data for-
mat uses different data types in the header and the data section.
REM ************************************************************************
Public Sub ReadIQData()
'--------- Create variables -----------------------------------------------
Dim IData(131072) As Single 'Buffer for floating-point
'I data (= 128*1024 bytes)
Dim QData(131072) As Single 'Buffer for floating-point
'Q data (= 128*1024 bytes)
'Note:
'Visual Basic cannot read in data volumes larger than 128k
'words!
Dim digits As Byte
'No. of digits as length
Dim IQBytes As Long
'Length of trace data in bytes
Dim IQValues As Long
'No. of meas. values in buffer
asciiResult$ = Space$(6553600) 'Buffer for ASCII I/Q data
The arrays for measured data are dimensioned in such a way that they can
accommodate the I/Q data of the R&S FSP (2 * 128 k * 4 byte).