OPTION 008 RF PROFILES AND COMPLEX SWEEP
Annex-B-14
Tutorial examples for sequence sweep
Example 1: System immunity test
Problem:
A digitally stepped signal is required to test the immunity of a system to RF signals applied at
harmonics of the internal clock frequencies of a unit under test. The test requires that the first 20
harmonics are checked and that the signal is swept 10 kHz either side of the nominal clock
frequency. The unit under test contains clock frequencies of 8 MHz (for the microprocessor) and
10 MHz.
Solution:
Set the signal generator to provide a frequency modulated signal from the internal triangle source
at a rate of 20 Hz and a deviation of 10 kHz.
Use the segmented sweep facility to set up Segment Number 0 to start at 8 MHz with a step size of
8 MHz, a step time of 100 ms and a stop frequency of 160 MHz.
Set up Segment Number 1 to start at 10 MHz with a step size of 10 MHz, a step time of 100 ms
and a stop frequency of 200 MHz.
Create a sequence sweep using Segment Number 0 and Segment Number 1. Set the sweep trigger
to continuous.
If the sweep is now started it will generate a stepped sweep alternating between harmonics of the
8 MHz and 10 MHz clock and the FM signal will sweep the frequency over a range of
±
10 kHz.
The FM signal will nominally sweep linearly over the 10 kHz range twice in each direction on
each step since the modulation rate is 20 Hz and the step time is 100 ms.
Example 2: Blocking performance test
A radio is being tested for blocking performance. The radio is tuned to 356.55 MHz and
uses 12.5 kHz channel spacing. A sweep is required which extends from 10 MHz below
the wanted channel to 10 MHz above the wanted channel but excludes the adjacent and
next adjacent channels. The RF level is required to be set to -37 dBm during the sweep.
Solution:
Set Segment Number 0 to start at 346.55 MHz, stop at 356.5125 MHz with a step size of 12.5 kHz
and a step time to 100 ms to allow enough time for the radio to respond. The RF level should be
set to -37 dBm.
Set Segment Number 1 to start at 356.5875 MHz, stop at 366.55 MHz with a step size of
12.5 kHz, a step time of 100 ms and an RF level of -37 dBm.
Set up Segment Number 2 with a start frequency of 356.5125 MHz, a stop frequency of
356.5875 MHz at step size of 100 kHz and a step time of 100 ms. Set the RF level to -144 dBm.
Set up a sequence sweep using Segment Numbers 0, 2 and 1. The signal generator will now
sweep from 346.55 MHz to 356.5125 MHz at -37 dBm, then turn the carrier off, step to
356.5875 MHz, turn the carrier on and then sweep to 366.55 MHz as required.
Complex sweeps
RF profiles, offset and sequence sweep
The sequence sweep can be combined with the RF profile and RF offset facility to provide a swept
signal source where the signal generator displays the RF level at the output of an external
frequency dependent amplifier or attenuator.
To set up a sweep of this type use the required sequence sweep, and RF profile and RF offset can
be set up as previously described. If the required RF offset and RF profile are then enabled and
the sequence sweep selected a complex sweep incorporating all these facilities can be generated.