WFS1 Transimpedance
The attached plots show the location of the ~29.5 MHz pole and the 59 MHz notch for each quadrant of the WFS1 Sensor head.
| WFS1 |
Pole (MHz) |
Z(Ohms) |
Notch (MHz) |
Z(Ohms) |
| Q1 |
28.89 |
598 |
60.38 |
0.83 |
| Q2 |
29.20 |
513 |
57.70 |
0.57 |
| Q3 |
29.63 |
681 |
59.63 |
0.89 |
| Q4 |
28.89 |
609 |
58.13 |
0.78 |
As may be seen from the above table, these frequencies will need to be adjusted in some cases.
From the plots we can see that, when there is no attenuation set on the attenuator AT65-0263 (ref D990249-A), the MAX4107 oscillations are seen in Q2,Q3,Q4 quadrants at around 200 MHz.
Rana suggested, from his previous encounter with this circuit, that the solution is to remove the second MAX4106 and the attenuator on the RF line to avoid this oscillation.
A look at the circuit board shows that some of the inductors have not been mounted. That explains the presence of only one notch though the schematic shows two.
 
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