Four quadrant diode front end module

for the Virgo linear alignment

Due to lack of spare parts, new quadrant diode front ends for use of the Virgo Linear Alignment were fabricated. In these new modules the orientation of the four quadrant diode is kept to the diagonal position, what is called the x-orientation. These modules are mechanically and electrically compatible with the existing modules. This type is V1 or spare module (April 2007).

V1 (spare):
Module description
Main board schematics
Main board Gerber plots
Detector board schematics

V1+:
One module exists that uses the V1 boards, but has the plus configuration of the four quadrant detector. It also contains the electronics for proper subtraction of the quadrant's signals. It does not contain the upgrades of the V2 module. It uses the same cables, power supply etc..

V2 (plus configuration):
Virgo aims for higher laser power in 2008. Two new type of front ends are being develloped: a 3 mW and a 30 mW optical power type. The orientation of the four quadrant diode is changed from the x-orientation to the + orientation. The DC outputs will have a larger range than the spare modules. The hf outputs (horizontal and vertical) contain a bandfilter with a center frequency of 6.24 MHz or 8.35 MHz. The filters can also be bypassed. The DC or quadrant outputs have whitening filters, giving an extra amplification above 10 Hz.
Main differences with V1 are:

+ orientation of the four quadrant detector
6.26 MHz band filter for the HF outputs
whitening filter for the DC outputs: adjustable extra gain between 10 Hz and 2 kHz
higher DC output level (up to 10 V with high impedance ADCs)
much better cooling of the four quadrant detector
adjustable current limit for the detector supply
isolated mounting to prevent ground loops
single 12 V supply

Documentation:
Module description (April 2009)
Module types (4 aug 2008)
pictures and instructions for mounting and disassembly (1 aug 2008)
Main board schematics
Main board layout
Detector board schematics
Detector board layout
Mechanical drawings (1 aug 2008)

Demodulator board documentation

Virgo homepage
Virgo hardware page (login requiered)
Jo vd Brand's homepage

You can mail

suggestions for this page to: Henk Groenstege .

april 2009