Matt, Lisa

With the fixed laser calibrator head we could finally make a measurement of the RF signal chain of the IMC LSC RFPD (24.078 MHz, S/N: S1203396).

- Laser Head: 4 mW @ 980 nm;
- Laser Head RF input calibration: 13e-3 W/V;
- LSC RFPD DC Transimpedance = 200 Ohm;
- LSC RFPD RF Transimpedance = 476 Ohm;

 Calibration using the DC response 

* Measured REFL_DC = 480 counts

=> Resp = 480/(1638 [counts/V] * 200 [V/A] * 4e-3 [W]) = 0.37 [A/W] 

 RF Signal chain 

- RF input modulation to the Laser Head Calibrator: 0.1 Vptp sine @ 24.078473 MHz;

=> Expected RF to the demod board = 476 [V/A] x 0.37 [A/W] x 13e-3 [W/V] x 0.1 [Vptp] = 230 mVptp

* Measured RF_in to the demod board: 240 mVptp

=> Expected I/Q monitor of the demod board = 10 (demod board gain) x 1/2 (mixer) x 240 [mV] = 1.2 Vptp  @ 100 Hz

* Measured I/Q monitors of the demod board: 1.3 Vptp
* Measured TEST1 input of the common board: 1.3 Vptp


The measured values are withing 10% of what we expected.