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Wir schaffen Wissen – heute für morgen
10. April 2023PSI, 10. April 2023PSI,
Paul Scherrer Institut
Status of CAVITY BPM RFFE & ADC
June 24, 2010
Markus Stadler
Talk agenda
M. Stadler Cavity BPM RFFE & ADC - Status Seite 2
•RFFE overview
•Mesurement results
•Redesign measures
•Performance expectation of BPM system
•Outlook
24.6.2010
Front-End redesig: RF section
LO generator
mixer
Range switch
3.3GHz BPF
IF amp. / filter
M. Stadler Cavity BPM RFFE & ADC - Status 24.6.2010 Seite 3
Prototype RFFE: System overview
Seite 4
• direct downconversion to (near) zero IF• tunable (in steps) LO frequency• tunable LO phase• on-board conversion clock generation for ADC
M. Stadler Cavity BPM RFFE & ADC - Status 24.6.2010
Pulse response
Seite 5
ADC output (ref-Q)
-14000
-12000
-10000
-8000
-6000
-4000
-2000
0
2000
4000
0 100 200 300 400 500 600
time (ns)
AD
C v
alu
es
• Baseline=ADC-offset
M. Stadler Cavity BPM RFFE & ADC - Status 24.6.2010
Distance measurement principle
Seite 6
0
2000
4000
6000
8000
10000
12000
14000
16000
0 200 400 600 800 1000 1200
time (ns)
AD
C v
alu
es
mag(REF)
mag(Y)
R
Y
)( mR
YkD YY Basic distance calculation:
R and Y are in ADC-LSB, ky is in μm
M. Stadler Cavity BPM RFFE & ADC - Status 24.6.2010
Jitter estimation (1)
Seite 7
Estimating position jitter from equivalent ADC input noise
)( 2
2
2
2
mYRR
Yk YRYDY Position jitter:
kY: proportionality constant (≈meas.range/2)
Y,R: Y- and Reference channel peak amplitudes (ADC LSB or volts)
σR, σY: ADC equivalent input noise (LSB rms or volts rms)
Estimation (rather than calculation) because only additive noise is considered !
M. Stadler Cavity BPM RFFE & ADC - Status 24.6.2010
Jitter estimation
Seite 8
RFFE / ADC total noise (ADC equivalent input noise)
CH RFFE 1 (μV-rms) RFFE 2 (μV-rms)
I_REF 172.5933 164.7761
Q_REF 163.8715 158.8132
I_Y 165.9212 177.2467
Q_Y 166.2281 163.8363
I_Z 163.6221 164.2646
Q_Z 160.906 166.5494
ADC (LTC2206) high gain mode (FS=1.5Vpp)
Measurement:
Calculation: System noise (figure) calculation yields 169 μV-rms
M. Stadler Cavity BPM RFFE & ADC - Status 24.6.2010
BPM Prototype Resolution Measurement (SLS-Linac)
Seite 9
:5SLS Reference
500 MHz
R FFE2
100 M H z R eference
REF (m onopole) cavityre f
z
y6
Virtex Eva l-B .
V irtex Eva l-B .
AD C6
SC LK
AD C -Input
M L550
AD C
SC LK
AD C -Input
M L550
Y (dipole) cavity
R FFE1
100 M H z R eference
ref
z
y
Measurement principle:
Measure of identical signals with two independend BPM Systems and correlate measured distances
measured D2 (μm)
measured D1 (μm)
Assuming identical distributions of measurements D1 and D2:
2
2121
DDVarDD
M. Stadler Cavity BPM RFFE & ADC - Status 24.6.2010
Example measurement series (1)
Seite 10
-3
-2
-1
0
1
2
3
0 50 100 150 200
bunch no.
measu
red
dif
fern
ce (
μm
)
Settings: 0.15nC / 400μm
ADC: High-Gain mode (FS=1.5Vpp)
jitter: 0.61 μm-rms (measured)0.62 μm (calculated)
M. Stadler Cavity BPM RFFE & ADC - Status 24.6.2010
Example measurement series (2)
Seite 11
Settings: 0.3nC / 500μm
ADC: High-Gain mode (FS=1.5Vpp)
-1.5
-1.0
-0.5
0.0
0.5
1.0
0 20 40 60 80 100 120 140 160
meas no.
measu
rem
en
t d
iffe
rnece (
μm
)
jitter: 0.33 μm-rms (measured)0.28 μm (calculated)
M. Stadler Cavity BPM RFFE & ADC - Status 24.6.2010
RFFE Pulse Linearity Measurements
Seite 12
-4 -3 -2 -1 0 1 2 3 4-3
-2
-1
0
1
2
3
4
RFFE input peak voltage (Vp)
AD
C d
iffer
etia
l inp
ut v
olta
ge (
V)
ADC FS
Prototype System pulse linearity:
M. Stadler Cavity BPM RFFE & ADC - Status 24.6.2010
Front-End redesig: Local temperature control
• Prototype RFFE temperature dependence suggests that temperature should be stabilized to better than 0.5 ºC
• In redesigned RFFE several local temperature control loops applied
Measured amplitude temperature dependence of prototype RFFE
20
22
24
26
28
30
32
0 20 40 60 80 100 120 140
time (min)
Tem
p (
°C)
0.47
0.472
0.474
0.476
0.478
0.48
0.482
0.484
0.486
0.488
0.49
0 20 40 60 80 100 120 140
time (min)C
H1,
CH
2 am
plit
ud
es (
Vp
)
1.011
1.012
1.013
1.014
1.015
1.016
1.017
1.018
0 20 40 60 80 100 120 140
time (min)
CH
2/C
H1
Temperature:
Absolute amplitude drift (incl. switch-on drift):
Drift of amplitude ratio:
Ca. 0.1% per deg-C
M. Stadler Cavity BPM RFFE & ADC - Status 24.6.2010 Seite 13
Conclusion from Measurements
Seite 14
• Measurement jitter is < 1 μm
• Measured jitter in good agreement with calculation
• Temperature sensitivity needs improvement
• Linearity is within 2%
• Additive noise sources in signal chain dominate the jitter performance
• Synthesizer phase noise / timing jitter do not significantly degrade performance
→Redefinition of charge ranges improves resolution
→local temperature control
Measurements on prototype system suggest the following conclusions:
→not much margin ! Difficult to measure
→simple and cheap PLL-synthesizers can be retained
M. Stadler Cavity BPM RFFE & ADC - Status 24.6.2010
Front-End Redesign (1)
Seite 15
• RFFE control via single I2C-bus• Temperature controlled critical circuit parts• 216 MHz machine reference (previously 81MHz)• IF-amplifier redesigned providing gain control (Pick-up tolerances)• Redefinition of charge ranges• Hot-Swap controlling
Main RFFE design changes:
M. Stadler Cavity BPM RFFE & ADC - Status 24.6.2010
Front-End redesign (2)
• RF Phase Control (360 deg)
• RF frequency control (9MHz steps)
• Conversion Clock Phase Control
• 12 Local Temperature Stabilizaiton areas on the PCB (analog or digital) around sensitive circuit parts
• Charge Range control (3 ranges from 0.1 to 1nC, 1 low charge range)
• 160MHz / +12dBm ADC clock output
Main RFFE design changes:
M. Stadler Cavity BPM RFFE & ADC - Status 24.6.2010 Seite 16
Front-End redesig: Local temperature control
Local temperature control circuit:
•Temperature sensitive circuits are locally heathed at 2-5ºC above their free-running steady state temperature.
•This will consume about 300mA of extra current (whole RFFE)
• Temperature stabilization: analog or digital control
• Temperature readout resolution 0.04 ºC
M. Stadler Cavity BPM RFFE & ADC - Status 24.6.2010 Seite 17
Front-End redesig: RF section
Prototype: 2 charge ranges
Upper range: 0.3-1nC
Lower range: 0.1-0.33nC
→ Charge ratio =3.3
Redesigned: 3+1 charge ranges
Upper range: 0.48-1 nC
Mid range: 0.22-0.48 nC
Low range: 0.1-0.21 nC
(additional range: <0.1 nC)
→ charge ratio =2.1
sp litte rin p u t B P F
S P 4 T S P 4 T
Max position jitter ~ (charge ratio) · (meas. range)
M. Stadler Cavity BPM RFFE & ADC - Status 24.6.2010 Seite 18
Linearity dictates ≈0dBm at full-scale offset and charge
Minimum pickup sensitivity:
0dBm at mixer RF-port @ max. beam offset and upper bound of lowest charge range
(WITHOUT an RF amplifier)
In our case (2.2dB cable loss for 6m of RF cable and 0.21nC bunch charge):•6 mV/(nC·um) for ±1000 um•3 mV/(nC·um) for ±500 um
Cable loss RF-path loss
Pick-Up sensitivity for lower charge ranges
First priorities to maintain resolution at lower charge ranges (<0.1nC) would be: • Reduce losses in cable and RFFE RF-part• Increase pick-up sensitivity
M. Stadler Cavity BPM RFFE & ADC - Status 24.6.2010 Seite 19
Redesigned RFFE block diagram
M. Stadler Cavity BPM RFFE & ADC - Status 24.6.2010 Seite 20
Expected Performance of 2nd Prototype
Seite 21
Single bunch resolution (μm-rms)
Performance estimation based on calculations and measurements on 1st prototype:
Temperature sensitivity <0.3 %/ºC
linearity <2%
Bunch to bunch crosstalk
<1 μm (digital comp.)
For a complete list of performance numbers see project doc.
Charge Range
Charge (nC)
Beam offset (μm)
10 1000
high1.00 0.23 0.25
0.47 0.48 0.54
mid0.47 0.23 0.25
0.22 0.48 0.54
low0.22 0.28 0.31
0.10 0.60 0.67
M. Stadler Cavity BPM RFFE & ADC - Status 24.6.2010
Outlook
Seite 22
Status Start date End date
Schematic drawing Review
PCB layout Started Jul 2010
Mechanical drawings(shield, front-panel
Aug 2010
PCB assembly Aug 2010
Laboratory tests Sept 2010
Tests (SwisFEL 250MeV injector)
Sept 2010 (?)
Tests FLASH Nov 2010 (?)
M. Stadler Cavity BPM RFFE & ADC - Status 24.6.2010
Seite 23
Thanks !
M. Stadler Cavity BPM RFFE & ADC - Status 24.6.2010