Overview of green electronics

Preliminary design for the electronics used in 40m green locking.

Contents

Overview of green electronics
VCO for frequency tracking
PDH box
frequency counter
digital channel assign
wideband RFPD for green PLL
1. frequency response
2. noise performance
DC PDs
1. PDA36A
digital front end filters
Thermal feedback LPF
1. circuit diagram
2. expected transfer function of compound frequency actuator
Function Generator
Summing Amplifier
1. Diagram
2. noise performance
Temperature Controller for doubling oves
RF stuff
RS232 serial device server
Vertex BeatBox

VCO for frequency tracking

VCO range

Synergy VCO part number XXX has 1.2MHz/V VCO range.

Filter respons

80MHz LIGO VCO box is used to readout the frequency of the beat signal precisely.

Noise performance

Capture range and Lock range

According to a simple calculations...

lock detection and boost

rms detection

PDH box

Filter Shape

Open loop transfer function

Measured on 22 Dec 2015, with the average level of green transmission at 0.457.

Noise performance

LPF for RF cutoff

Remotely controlled Boost switch

frequency counter

SR620 is employed to read out the frequency of the beat signal.

setting parameters
readout range		MHz
DAC bit resolution
noise

digital channel assign

wideband RFPD for green PLL

A Silicon photodiode with the diameter of 10mm is used. To have a fast response up to about 1MHz -150V is applied onto the photo diode.

The schematic is available on svn

EG&G SGD-444A Si PIN PD SGD-444A.pdf

frequency response

noise performance

Here is the noise model for the RFPD using liso.

DC PDs

PDA36A

The PDA36A is an amplified, switchable-gain, silicon detector designed for detection of light signals over 350 – 1100nm wavelength range.

parameters
Detector	Si PIN
trans impedance gain	1.5k - 475k (switchable)	[V/A]
responsibility	0.3	[A/W] at 532 nm
output impedance	50	[Ohm]
Output Voltage	0-5	[V] with 50 Ohm termination
Band Width	17	[MHz]
Dark noise		nV/sqrtHz

digital front end filters

anti-aliasing filter
anti-imaging filter
whitening filter

Thermal feedback LPF

circuit diagram

expected transfer function of compound frequency actuator

Function Generator

To get a phase modulation imposed on the end IR lasers, a function generator is needed.

SR___

Summing Amplifier

In order to send a feedback signal and modulation signal to the laser PZT at the same time, it is desired to have a summing amplifier. The amplifier should handle the signal from DC to 200kHz. Currently this is taken place by SR560.