1. Authors C. Rivetta– Fermilab. F. Arteche , F. Szoncso, - CERN
Noise Immunity Analysis of Forward Hadron Calorimeter Front-end Electronics.
Authors
C. Rivetta– Fermilab.
F. Arteche , F. Szoncso, - CERN
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2. OUTLINE 2-Noise considerations 3-Thermal noise
1- Introduction
2-Noise considerations
3-Thermal noise
4-Multi-transmission line model
5-Surface transfer impedance
6-Common mode rejection
Examples
7-External electromagnetic field
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8th Workshop on Electronics for LHC Experiments
COLMAR - France, September 2002

3. 1.INTRODUCTION
The goal of this study is to establish the susceptibility level to electromagnetic noise of the HF CMS calorimeter.
Characterise the influence of topology and parameters on the overall FEE noise
Thermal Noise
Conductive Common Mode (CM) Noise
Electromagnetic Interference (EMI)
Generate a software tool to assist:
The analysis of cable quality.
Analysis of common mode effects on sensitive equipment.
Conducting & radiated coupling through cables.
8th Workshop on Electronics for LHC Experiments
COLMAR - France, September 2002

4. 1.INTRODUCTION PMTs / QIE distance is 4 meters.
Dy7
Rgnd
QIE sig.
QIE ref.
Anode
Dy8
PMT HV Cc
PMTs / QIE distance is 4 meters.
QIE:Sample Charge integrator with ADC
QIE is a differential current mode amplifier.
QIE input impedance 50 or 93 Ohms.
Asymmetric dynamic range.
Gain: 1fC/LSB
Sampling freq.: 40MHz.
8th Workshop on Electronics for LHC Experiments
COLMAR - France, September 2002

5. 2. NOISE CONSIDERATIONS
Low level signal processing of FEE is defined by the noise
Noise at output is composed by several factors
Power Spectrum nth(t)
nCM(t) and nEMI(t) in frequency domain
Criteria generally used
8th Workshop on Electronics for LHC Experiments
COLMAR - France, September 2002

6. 3. THERMAL NOISE 8th Workshop on Electronics for LHC Experiments
COLMAR - France, September 2002

7. 3. THERMAL NOISE Cables with low impedance increse the thermal noise
ENC L
Cables with low impedance increse the thermal noise
There exists a critical length for the cable where the noise does not increase.
Measured by T. Zimmermann, Fermilab
8th Workshop on Electronics for LHC Experiments
COLMAR - France, September 2002

8. 3. MULTI-CONDUCTOR TRANSMISSION LINE MODEL
TEM mode
R,L,C,G line parameter matrices per unit length
V,I voltage & currents vectors
Solution:
Terminal Boundary conditions
Frequency domain
Time domain ) , ( 1 t z I 2 3 n D + .. . V
8th Workshop on Electronics for LHC Experiments
COLMAR - France, September 2002

9. 4. SURFACE TRANSFER IMPEDANCEVt
Zt(w)=Vt(w)/I(w)
8th Workshop on Electronics for LHC Experiments
COLMAR - France, September 2002

10. 4. SURFACE TRANSFER IMPEDANCEV2
Environment
Inner Conductors V1 R2 R1 L2 L1
I0* Zt2
I0* Zt1 V0 I2 I0 I1
U0* Yt2
U0* Yt1
C20
C12
C10
CS0 RS LS
Shield
Outer System
Inner System
8th Workshop on Electronics for LHC Experiments
COLMAR - France, September 2002

11. 4. SURFACE TRANSFER IMPEDANCE
Zd (w ) Diffusion coupling due to skin effect (LF)
Mh - Aperture coupling (HF)
Mb - Braid inductance (HF)
Define the amount of noise coupled to the internal conductors
It is a characteristic parameter of shielding cable
8th Workshop on Electronics for LHC Experiments
COLMAR - France, September 2002

12. 4. COMMON MODE REJECTION Rgnd : 100ohms, 1Kohms, 10Kohms
Vcm
QIE sig.
QIE ref.
PMT Cc Cp
Rgnd : 100ohms, 1Kohms, 10Kohms
Cp -Parasitic capacitance of PMT, board and connections
Cc- Compensation capacitance
Coaxial cable RG-58
8th Workshop on Electronics for LHC Experiments
COLMAR - France, September 2002

13. 4. COMMON MODE REJECTION
8th Workshop on Electronics for LHC Experiments
COLMAR - France, September 2002

14. 4. COMMON MODE REJECTION
8th Workshop on Electronics for LHC Experiments
COLMAR - France, September 2002

15. 4. COMMON MODE REJECTION
8th Workshop on Electronics for LHC Experiments
COLMAR - France, September 2002

16. 5. EXTERNAL ELECTROMAGNETIC FIELD
External magnetic field
Voltage generator (VF)
External electric field
Current generator (IF)
VF, IF are dependent of system geometry.
Applicable for near fields & far fields -weak coupling.
Example:
Far-field, E=100uV/m
(EN A)
8th Workshop on Electronics for LHC Experiments
COLMAR - France, September 2002

17. 5. EXTERNAL ELECTROMAGNETIC FIELD
8th Workshop on Electronics for LHC Experiments
COLMAR - France, September 2002

18. 5. EXTERNAL ELECTROMAGNETIC FIELD
8th Workshop on Electronics for LHC Experiments
COLMAR - France, September 2002

19. 5. FUTURE WORKS
Final conclusions about sensitivity to CM and EM interference
Extend the analysis to different HF cable prototypes.
Include studies of near fields
Electric field
Magnetic field
Extend to time domain solutions
Transient effects
8th Workshop on Electronics for LHC Experiments
COLMAR - France, September 2002

20. 5. CONCLUSIONS
The analysis allows to quantify effects of parasitic elements and unbalances on HF configuration.
The system is very sensitive to parasitic elements that unbalance the differential topology
Proper selection of final cable
Influence of Rgnd is important at low frequency
8th Workshop on Electronics for LHC Experiments
COLMAR - France, September 2002