R&S ESU Series Operating Manual page 690

R&S ESU
6.20.3 TRACe:IQ Subsystem
The commands of this subsystem are used for collection and output of measured IQ measured data. A
special memory is therefore available in the instrument with 16M words for the I and Q data. The mea-
surement is always performed in the time domain (span = 0 Hz) at the selected center frequency. The
number of samples to be collected can be set. The sampling rate can be set in the range from 10 kHz to
81.6 MHz; when channel filters are used, the sampling rate depends on the filter involved and can be
determined via a special command depending on the setting used. Prior to being stored in memory or
output via GPIB, the measured data is corrected by an equalizer filter in terms of frequency response.
Depending on the sample rate, the following maximum bandwidths can be obtained during the measure-
ment.
Sample rate Sample rate
(from) (to)
81.6 MHz 40.8 MHz
40.8 MHz 20.4 MHz
20.4 MHz 10.2 MHz
10.2 MHz 5.1 MHz
5.1 MHz 2.55 MHz
2.55 MHz 1.275 MHz
1.275 MHz 0.6375 MHz
0.6375 MHz 318.75 kHz
318.75 kHz 159.375 kHz
159.375 kHz 79.6875 kHz
79.6875 kHz 39.84375 kHz
39.84375 kHz 19.921875 kHz
19.921875 10 kHz
kHz
Fig. 6.45 shows the analyzer hardware from the IF section to the processor. The IF filter is the resolution
filter of the R&S ESU with bandwidths selectable from 300 kHz to 50 MHz. The A/D converter samples
the IF signal (20.4 MHz) at a rate of 81.6 MHz.
The digital signal is down-converted to the complex baseband, lowpass-filtered, and the sampling rate is
reduced, i.e. the output sampling rate is set between 10.0 kHz and 81.6 MHz in steps of 0.1 Hz. This
avoids unnecessary oversampling at narrower bandwidths, which saves processing time and increases
the maximum recording time. Since the sample rate can be programmed quasi-continuously, even sam-
pling rates, which cannot be derived by direct division of the 81.6 MHz, can be set.
The I/Q data are written to a memory of 16M words. The data can then be read out from these areas in
blocks that are 512 k words each. The memory is hardware-triggered.
Operating Manual 1302.6163.12 - 03
Max. bandwidth Notes
30 MHz Half-band filter at half the sample rate
(81.6 MHz)
0.68 sample rate
0.8 sample rate
0.8 sample rate
0.8 sample rate
0.8 sample rate
0.8 sample rate
0.8 sample rate
0.8 sample rate
0.8 sample rate
0.8 sample rate
0.8 sample rate
0.8 sample rate
Remote Control – Description of Commands
TRACe Subsystem
6.251