The WFS2 Transimpedance has been measured to determine if it also suffers from the same 200MHz oscillations seen in WFS1 sensor head
The attached plots (pdf attached) show that the 29.5 MHz peak needs tweaking in Q2 and Q1 seems to have a much lower transimpedance than other quadrants. The table below summarises the resonances and notches of the ckt
| WFS2 |
Pole(MHz) |
Z(Ohms) |
Notch (MHz) |
Z(Ohms) |
| Q1 |
29.63 |
576 |
59.25 |
0.76 |
| Q2 |
28.5 |
862 |
59.0 |
1.41 |
| Q3 |
29.8 |
766 |
59.25 |
1.05 |
| Q4 |
29.8 |
704 |
59.0 |
1.09 |
The peak at 10MHz is much sharper than the similar peak at 13MHz in the case of WFS1. Is this a matter for some concern?
The 200MHz oscillation once again exists in Q2, Q3 and Q4. This sensor head will also require the same treatment as WFS1.
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I have shifted the Jenne laser back to the small table where we do RF PD characterisation (RFPD table). I found several 25pin D-type connector cables, connected them in tandem and am using that to power the WFS2 sensor head at the RFPD table.
The set up is ready for looking at the RF response of the WFS sensors. Will continue tonight.
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