Agilent Technologies VXI E1439 - Manual (Page 36)

26
Using the Agilent E1439
Delay and phase in triggered measurements
trigger_delay = -2 (a pre-trigger delay of 2)
Because the filter_bw is 4 with decimation on, there are 16 input samples for every output sample
for a decimation rate of 2
4
.
The phase returned is the phase of the LO at the actual trigger point, not the desired trigger point.
The following example illustrates how age1439_phase_actual_get might be used. In this
example, the input signal is a sine wave at a frequency of 4 MHz. The module is set up as follows:
frequency_center = 4.5 MHz
filter_bw = 4 (2.4 MHz span)
filter_decimate = 1 (on)
trigger_type = 1 (ADC trigger)
trigger_delay = -32 (a pre-trigger delay of 32)
trigger_adclevel = 0
data_type = 1 (complex)
After the measurement is completed, call age1439_delay_actual_get and age1439_phase_
actual_get. In this example, the values returned happened to be:
delay_actual = 16
phase_actual = 19697
trigger_delay_actual=8 (or 8/16=1/2 output samples)
trigger
level
1 2 3 4
desired trigger
actual trigger signal
trigger_delay_actual=0 (or 0/16=0 output samples)
1 2 3 4
trigger_delay_actual=4(or 4/16=1/4output samples)
1 2 3 4
desired trigger
desired trigger
actual trigger
actual trigger
trigger
level
trigger
level