Beam Diagnostics for JLAB

John Musson

JLAB I&C Group

Overview● Beamline Sensors

● Signals, Noise, and Input Parameters

● Tutorial● Receiver Electronics

● Algorithms● Bench Testing

● New M15

● Conclusions

● References

Typical Beamline Sensors

M15 “can” Pillbox Cavity

Cavity Response

Click to edit Master text stylesSecond level

● Third level● Fourth level

● Fifth level

___________________Courtesy Jürgen Schreiber, ECFA/DESY LC workshop, Amsterdam, April 1-4, 2003

Cavity BPM: X, Y, and I

TM010 Mode for I

TM110 Mode for X & Y

Slugs provide proper excitation, reducing TM010 x-talk

Nominal output: 54nV-uA/um (-132 dBm)…per MAFIA simulations

A Tutorial: Signals and Noise● Resolution is determined by

signal-to-noise ratio● Fancy algorithms help w/

filtering/integration, etc.

but physics prevails.● So, what is noise? Signal?● Also, what is meant by

“Dynamic Range?”● AKA “Linearity”

Required Input Parameters● Dynamic Range

● Imin and Imax

● Resolution/Accuracy● Determines SNR

– Based on physics and algorithm

● Output Rate● Ultimate system BW and output sample

rate

● Isolation● Crosstalk and rejection of “systematics”

Tests for these parameters are relatively standardized and routine!!

Rx Design Parameters(Signal Level)

Determine Sensor output for given beam conditions

Match Rx with sensor and SNR requirements (mostly driven by THD specs.).

0.0001 0.0010 0.0100 0.1000 1.0000 10.0000 100.0000 1000.0000

-200.00

-150.00

-100.00

-50.00

0.00

50.00Nominal Sensor Response vs. Beam Current

M15 (4-Wire)Cavity BCMCavity BPM (1mm offset)

Beam Current, uA

No

min

al

RF

Ou

tpu

t, d

Bm

Click to edit Master text stylesSecond level

● Third level● Fourth level

● Fifth level

Example: Recent Beam Test

M15 w/ Prototype Electronics, 5/11

1 1 0 1 0 0 1 0 0 0 1 0 0 0 0 1 0 0 0 0 0 1 0 0 0 0 0 0

- 1 8 0

- 1 7 0

- 1 6 0

- 1 5 0

- 1 4 0

- 1 3 0

- 1 2 0

- 1 1 0

- 1 0 0

- 9 0

- 8 0

M i n i m u m D e t e c t a b l e S i g n a l ( M D S ) v s . B a n d w i d t h

C o n t o u r e d f o r V a r i o u s N o i s e F i g u r e s

N F = 0 d BN F = 1 0 d BN F = 2 0 d BN F = 3 0 d B

B a n d w i d t h , H z

MD

S,

dB

m

Noise Floor for 50 Ohm System

Phase Measurement Drives SNR

SNR determines ability to resolve +/- phase at low end:

Click to edit Master text stylesSecond level

● Third level● Fourth level

● Fifth level

Identical to BPSK BER analysis

Click to edit Master text stylesSecond level

● Third level● Fourth level

● Fifth level

http://www.siemens-cn.com

Extra SNR (~ 13 dB) is needed for angular demodulation, since it is non-linear (“threshold ing”)

www.eetimes.com

Extra Baggage....

QWEAK Example

...

QWEAK Design Parameters

Determine Sensor output for given beam conditions

Match Rx with sensor and SNR requirements for double-difference of 1%

0.0001 0.0010 0.0100 0.1000 1.0000 10.0000 100.0000 1000.0000

-200.00

-150.00

-100.00

-50.00

0.00

50.00Nominal Sensor Response vs. Beam Current

M15 (4-Wire)Cavity BCMCavity BPM (1mm offset)

Beam Current, uA

No

min

al

RF

Ou

tpu

t, d

Bm

Click to edit Master text stylesSecond level

● Third level● Fourth level

● Fifth level

Noise BW = 100 kHzKTB = -124 dBm (perfect 290K Rx)

Min SNR = -20 dBm - (-124) = 104dB

Rx Preliminary Performance Quantity (1 Hz BW) Max Gain Min Gain

Noise Figure 2 dB 3 dB

Channel Gain 108 dB 48 dB

Input IP3 -70 dBm -57 dBm

MDS (ADC- limited) -170 dBm -133 dBm

F.S. Input -72 dBm -37 dBm

Output SNR 1 Hz 71 dB 96 dB

100 kHz 21 dB 46 dB

0.1% THD Range 10 dB-Hz 30 dB-Hz

1% THD Range 30 dB-Hz 50 dB-Hz

(dB-Hz = |MDS| - |20log(THD)| - |IIP3|)

Signal Level M15 (4-wire sum) BCM Cavity BPM, 1mm

-62 dBm 5 uA 80 nA 3 uA

-112 dBm 17 nA 250 pA 11 nA

-143 dBm 505 pA 8 pA 319 pA

PCB Layout

PC-104 IOC

4 Independent, identical DDC receiver chains. Shield covers should provide ~70 dB of isolation

Functional Description

Click to edit Master text stylesSecond level

● Third level● Fourth level

● Fifth level

Firmware: SystemVue + AHDL

EPICS Interface / Calibration

Algorithm Dependence

Position=

Position=logX a

X b

Accuracy and noise sensitivity are affected

Analog Receiver Architecture

R F I N D O W N C O N V E R S I O NM I X E R ( S ) D E M O D U L A T O R

I F B A S E B A N DP R O C E S S O R

B A S E B A N DD A T A O U T

L O

L O C A LO S C I L L A T O R ( S )

Low-Level RF Workshop, JLAB 2001

KC9KEP, ARRL

Look in your parents' attic!

R F I N B A S E B A N DP R O C E S S O R

D A T A O U T

L O 1

A D C N C O

I

Q

c o s

s i n

Digital Receiver Architecture

Low-Level RF Workshop, JLAB 2001

Nearly always integer math!!!

Arctan

I/Q Sampling / Detection

t I N P U T S I G N A L

S A M P L I N G : f S = 4 x f C

D E C I M A T I O N B Y 2

M U L T I P L Y B Y + / - 1

D I G I T A L F I L T E R

t S

( a )

( b )

( c )

( d )

( e )

tt S

tt S

tt S

tt S

fI N P U T S P E C T R U M

fS A M P L I N G : f S = 4 x f C

fD E C I M A T I O N B Y 2

fM U L T I P L Y B Y + / - 1

fD I G I T A L F I L T E R

f c

f c f s - f c f s + f c 2 f s - f c

f c f s - f c f s + f c 2 f s - f c

f s - 2 f c f s 2 f s - 2 f c

( a )

( b )

( c )

( d )

( e )

Time Domain Frequency Domain

Think of N, S, E, W cardinal point sampling

Harmonic Sampling

Over-rotation leads to aliasing

B

C

D

Scheme works for any 2π + (2N-1) * π/2

A

Harmonic Sampling

f

I F I N P U T

f c

( a )

f

L O C L O C K

3 f s

( b )2 f sf s

f

S A M P L E D I F

( c )3 f s - f c 4 f s - f c 5 f s - f cf c - 2 f s f c - f s f c

ADC Clock can be much lower than IF, to a point.......Jitter and Nyquist

Analog sampling ~ 100+ years old! Mark Kahrs, et al.

www.analog.com

Cost Benefit

Undersampling

Information BW still greatly OS!

Filtering / Energy Extraction

Cascaded Integrator Comb (CIC)

Finite Impulse Response (FIR)

Large number of taps usually required

Large latency.......Quality of Service

Control-feedback

Infinite-Impulse (IIR)

Emulates RLC and Xtal filters well....low latency

Frequency Discriminator

Courtesy Kawakatsu LaboratoriesQ⋅dI− I⋅dQ

I 2Q2

CORDIC Algorithm

COordinate Rotation DIgital Computer– Jack E. Volder, The CORDIC Trigonometric Computing Technique, IRE Transactions on

Electronic Computers, September 1959 – Ray Andraka, A Survey of CORDIC Algorithms for FPGA Based Computers, FPGA '98.

Proceedings of the 1998 ACM/SIGDA sixth international symposium on Field programmable gate arrays, Feb. 22-24, 1998, Monterey, CA. pp191-200.

● Iterative method for determining magnitude and phase angle– Avoids multiplication and division

● Nbits+1 clock cycles per sample● Can also be used for vectoring and linear

functions (eg. y = mx + b)

Concept

● Exploits the similarity between 45o, 22.5o, 11.125o, etc. and Arctan of 0.5, 0.25, 0.125, etc.

● Multiplies are reduced to shift-and-add operations

[ ] [ ]

−

⋅=θθ

θθx,yx',y'

cossin

sincos [ ][ ]i

iiiii

iiiiii

dxyKy

dyxKx−

+

−+

⋅⋅+=

⋅⋅−=

2

2

1

1

Angle Tan ( ) Nearest 2-N

Atan ( )

45 1.0 1 45

22.5 0.414 0.5 26.6

11.25 0.199 0.25 14.04

5.625 0.095 0.125 7.13

2.8125 0.049 0.0625 3.58

1.406125 0.0246 0.03125 1.79

0.703125 0.0123 0.01563 0.90

Y

X

Binary search, linked to sgn(Y)

Successively add angles to produce unique angle vector

Resultant lies on X (real) axis

≥−<+

=0,1

0,1

i

ii yif

yifd

)2arctan(1i

iii dzz −+ ⋅−=

∑ −⋅=i

iid )2arctan(φ

Functionally.....

with a residual gain of 1.6

New Diagnostic Receiver Parameters

Low Noise Floor

Facilitate low beam currents

Ability to perform Y-factor noise calibrations

4-Channel design, for cavity and differential measurements

All digital, for re-configuration and pre-processing

Onboard IOC (PC-104) for lower cost, maximum flexibility

Relatively inexpensive, using consumer electronics

Accurate / repeatable AGC

M15 w/ Prototype Electronics 5/11

System Test: Beam vs Wire● Although beam is favored, it is

often inconclusive● Beam motion and size can not be

separated

G-Line Bench Tests of M15

M15 Stripline (Evtushenko)

Conclusion

● Aggressively persuing Beam Diagnostics Development

● MOU Draft underway with Bergoz● New M15 to see battle, soon....● Rx elctronics to be used for '0L02,

M55/M56, etc.

References[ 1 ] R . A n d r a k a , “ A S u r v e y o f C O R D I C A l g o r i t h m s f o r F P G A B a s e d

C o m p u t e r s , ” 1 9 9 8 P r o c . O f A C M / S I G D A 6 t h I n t l . S y m p . O n F P G A s , M o n t e r e y , C A . , F e b . 2 2 - 2 4 , 1 9 9 8 . p p . 1 9 1 - 2 0 0 .

[ 2 ] R . G . L y o n s , U n d e r s t a n d i n g D i g i t a l S i g n a l P r o c e s s i n g 2 n d E d . , N e w J e r s e y , P r e n t i c e H a l l , 2 0 0 4

[ 3 ] M . F r e r k i n g , A n D i g i t a l S i g n a l P r o c e s s i n g i n C o m m u n i c a t i o n s S y s t e m s . N e w Y o r k : C h a p m a n a n d H a l l , 1 9 9 4 .

[ 4 ] R . B a i n e s , “ T h e D S P B o t t l e n e c k ” I E E E C o m m u n i c a t i o n s M a g a z i n e , V o l . 3 3 , N o . 5 , M a y , 1 9 9 5 . P p 4 6 - 5 4 . .

[ 5 ] R . N . M u t a g i , “ U n d e r s t a n d i n g t h e S a m p l i n g P r o c e s s , ” R F D e s i g n M a g a z i n e , S e p t . 2 0 0 4 , p p . 3 8 - 4 8 .

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[ 7 ] R . G . V a u g h a n , ” T h e T h e o r y o f B a n d p a s s S a m p l i n g , ” I E E E T r a n s . O n S i g n a l P r o c . , V o l . 3 9 , N o . 9 , S e p t . 1 9 9 1 .

[ 8 ] J . M u s s o n , T . A l l i s o n , R . F l o o d , J . Y a n , “ R e d u c t i o n o f S y s t e m a t i c E r r o r s i n D i a g n o s t i c R e c e i v e r s T h r o u g h t h e U s e o f B a l a n c e d D i c k e S w i t c h i n g a n d Y - F a c t o r N o i s e C a l i b r a t i o n s , ” P r o c . o f 2 0 0 9 P a r t i c l e A c c e l e r a t o r . C o n f . , V a n c o u v e r , B C , . C A . , M a y . 2 0 0 9 .

[ 9 ] M . K a h r s , “ A p p l i c a t i o n s o f R F a n d M i c r o w a v e S a m p l i n g , ” 2 0 0 3 I E E E M T T - S D i g e s t , 2 0 0 3 .

[ 1 0 ] R . C a l i , G . F e r r a r i , “ A l g o r i t h m s f o r C o m p u t i n g P h a s e a n d A G C i n D i g i t a l P L L R e c e i v e r s , ” R F D e s i g n M a g a z i n e , O c t . 1 9 9 2 . p p . 3 3 – 4 0

[ 1 1 ] E . T a c c o n i , C . C h r i s t i a n s e n , “ A W i d e R a n g e a n d H i g h S p e e d A u t o m a t i c G a i n C o n t r o l , ” P r o c . o f 1 9 9 3 P a r t i c l e A c c e l e r a t o r . C o n f . v o l . 4 , p p . 5 7 0 – 5 7 8 , J u l . 1 9 9 3 . P p . 2 1 3 9 - 2 1 4 1 .

[ 1 2 ] L . C o u c h , D i g i t a l a n d A n a l o g C o m m u n i c a t i o n S y s t e m s , 3 r d E d . , N e w Y o r k , M a c m i l l a n a n d C o l l i e r , 1 9 9 0 .

[ 1 3 ] J . V u o r i , J . S k y t t a , “ I m p l e m e n t a t i o n o f a D i g i t a l P h a s e - L o c k e d L o o p U s i n g C O R D I C A l g o r i t h m , ” P r o c . 1 9 9 6 I E E E I S C A S , A t l a n t a , G A . , 1 9 9 6 , p p . 1 6 4 - 1 6 7

[ 1 4 ] B . B r a n n o n , “ D e s i g n U n d e r s t a n d i n g t h e E f f e c t s o f C l o c k J i t t e r a n d P h a s e N o i s e o n S a m p l e d S y s t e m s , ” E D N M a g a z i n e , D e c . , 2 0 0 4 , p p . 8 7 –9 6 .

[ 1 5 ] F . E . T e r m a n , E l e c t r o n i c a n d R a d i o E n g i n e e r i n g , 4 t h E d . , , N e w Y o r k , M c G r a w - H i l l , 1 9 5 5