DAZZLER
TM
system manual Part I : installation & operation 8.6
item value meaning
TXtal 32.66 µs duration of acoustic interaction
Fdata 45 MHz sampling frequency
Fc 85.93 MHz RF or acoustic frequency at 800 nm
gendel 1.45 µs generation delay
Table 8.2: RF cycle parameters for model HR25-800
8.6 RF cycles description
The oscillograms shown are based on a standard HR25-800 Dazzler crystal, Table 8.2 gives the
necessary parameters to define the wave generation.
8.6.1 Single cycles
This is the normal mode of operation where one RF cycle is started by an external trigger .
Refer to the Figure 8.1 next.
• the bottom yellow trace (C1 scope channel) shows the attenuated RF output.
• the blue trace (C3 channel) shows trigina which is the reshaped trigger pulse
6
• the red trace (C2) displays gate which is the logic signal indicating that the RF gener-
ation is active
7
. gate occurs after a programmable delay, here set at about 30µs.
• the green trace (C4) shows the protectp signal, see Figure 8.7.4.
• Figure 8.2 shows similar conditions but for the time scale and green trace showing
highwhenA. The RF signal (yellow trace) is slightly late with respect to gate. The
delay between the rising edge of trigger and the start of RF generation depends of the
sampling frequency (Fdata) and varies from 300ns to 2.3µs. This delay is called gendel.
• Figure 8.3 has similar conditions as in Figure 8.1, except that the trigger mode has been
changed to no delay mode: notice the small delay between trigger and trigina,
• on Figure 8.3 between trigina and gate and between gate and the start of the RF
signal. The delays depend of the sampling period 1/F data.
• these delays are ”lumped” in the T
prog
control found in the Trig&Mode panel. Originally,
T
prog
meant the propagation time between the transducer face and the optical face where
the acoustic wave is reflected. It now includes all the irreducible delays.
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The trigger pulse applied to the BNC goes through a Schmitt trigger and a retriggerable monostable.
The blocking period is set with a jumper 10 µs or 0.5 µs used in the RF board circuits. Any value in that range
can be obtained by changing a special jumper.
7
Due to the pipelined DAC with digital filtering, the actual RF signal is 48 samples late at the output. This
delay is significant but is only one contribution to T
prog
..
V3.00 - 8
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April 2019 (ContentsTable) (FiguresTable) 82/94
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