1. Electronics: Demod + 4Q FE
Jo van den Brand, Second V+ review
Info on demodulator:
Info on front-end system:
11/10/2018

2. Demodulator boards Design Q2, Q3 2006 Prototype Q1 2007
2+2 Boards Q2 2007
Improvements 2007
Amplifier (noise)
PCB length
8.35 MHz (band filter)
11/10/2018
Han Voet, VU Amsterdam

3. Test results Conversion gains Cross talk
Apply MHz on Ref, MHz on RF
Low 2.75, mid low 25, mid high 230, high 2000
Cross talk
Apply 6.26 MHZ (8.35 MHz) to both reference inputs. Apply RF signal one channel (vertical/horizontal).
Board 4, 5: H/V I & Q out < 0.3% of V/H
I & Q phase 90 degree phase shift
Measured with a 50 Hz beat frequency output signal on the I & Q outputs
Phase deviation smaller than 1.5 degr
Equivalent input noise
1 nV/rtHz (to be confirmed)
RF input: white noise Hz – 20 MHz, mV RMS
11/10/2018
Discussion: replace all demod boards

4. 4Q FE – Modeling
Henk Groenstege
TINA-TI
Multisim
11/10/2018

5. Modeling Model agrees with data DC 2x lower RF 100 nV/rtHz
1/f noise amplifier
resistor noise
diode cap.
Model agrees with data
DC 2x lower
RF 100 nV/rtHz
(was 130 nV/rtHz)
Gives 2.5 pA/rtHz
Optimize both DC and RF
11/10/2018

6. Front-end amplifiers Non-linear design determined by
Diode
Capacitance
Leakage current
Feedback resistor (white noise)
Feedback capacitance
Desired bandwidth
Desired gain factor
1/f noise
Amplifier
Voltage noise
Current noise
Input capacitances
Gain-bandwidth product
Under consideration
OPA 846
OPA 657
AD 8675 (6V)
ADA
AD 829
Avoid switching in front-end
(stray capacitance)
11/10/2018

7. Photo diodes Si PIN YAG 444-4AH Si Centronic QD50-3T InGaAs Q3000
11 mm diameter
0.45 A/W
Rev. bias 180 V (power!)
10 pF
Si Centronic QD50-3T
IR enhanced
0.22 A/W
Rev. bias 15 V (GEO)
InGaAs Q3000
3 mm diameter
0.90 A/W
Rev. bias 10 V
< 225 pF
24 ns rise time
In discussion with various suppliers:
OSIOptoelectronics
Centronic
Hamamatsu
11/10/2018

8. InGaAs Simulation InGaAs Unacceptable performance at 6 Mz
Bandwidth limited < 400 kHz
InGaAs
3mm diameter type?
Ordered: will be tested
11/10/2018

9. 4Q FE: outside Dimensions of box roughly the same (48 * 100 * 170 mm)
Mounting tube (30 mm) on front
Same connectors and supply and steering voltages
Bias control & monitoring
New LF outputs
Same detector (YAG 444-4), but rotated to + orientation
Simple overload indication (LEDs)
Spares: orientation x
New: orientation +
11/10/2018

10. 4Q FE: inside Total redesign (old → new): First stage 2 kV/A → 10 kV/A
DC output amp. 5*, roll off at 100 Hz to 1*, passive pole at 35 Hz (if load > 50 kΩ) → cable driver 1*, pole at 100 kHz.
Extra LF outputs, 1 Hz to 100 kHz.
HF outputs amp. 20*, second order high pass 30 kHz, assumed BW 25 MHz → amp. 4*, 800 kHz … 25 MHz.
Bias monitor
Output with a scale -1/40, -200 V bias gives +5V.
11/10/2018

11. Status / issues Front-end electronics Prototypes have been constructed
No switching in transimpedance stage
Two FE versions
Low power: ≤ 3 mW
High power: ≤ 30 mW
Switching possible after first stage
DC filter 3.3 kHz LP
Prototypes have been constructed
Detector board, with first stage pre-amp
Driver board
contains the cable drivers
differential amplifiers for the hor. and vert. outputs
bias generation, etc
Further studies ongoing
Improve performance
Decide on configuration
Decisions needed on switching DC and RF
Anticipate meeting in January 2008
11/10/2018

12. Planning Discuss switching, etc. Replacement of demodulator boards
11/10/2018

13. Summary Demodulator boards Front-end electronics Planning
First systems delivered
Discuss production of additional boards
Front-end electronics
Simulation models in place
Amplifiers
Diodes
Test performance
Planning
Delivery prototype in March 2008
Delivery all boards in July 2008
11/10/2018

14. Results
1/f
Affected by C
Noise R2
Noise R1
11/10/2018

15. Noise sources Resistors R1 and R2 (10 k) Low pass filters Diode noise
Noise = 4R kT BW = 4(10.000)(1.38 10-23 J/K)(295 K)(1 Hz) = 1.6  V2
Low pass filters
fR1 = 1/2R1C2 = 1/2 ( )(1.5  F)=10.6 MHz
fR2 = 1/2R2C1 = 1/2 ( )(10  10-9 F)=1.6 kHz
Diode noise
Dark current 1nA (use 180 G on –180V)
Diode capacity 10 pF
Amplifier noise
Use pspice amplifier model
Includes 1/f noise, etc.
11/10/2018