Le Misure ad Alta Frequenza per le Applicazioni di Signal Integrity

METODOLOGIE E DISPOSITIVI DI MISURA
Linea di Ricerca A6:
MISURE PER LA CARATTERIZZAZIONE
DI COMPONENTI E SISTEMI
Responsabile: Prof. Gregorio Andria, Politecnico di Bari
Siena, 5-9 settembre 2011
MISURE PER LA CARATTERIZZAZIONE
DI COMPONENTI E SISTEMI
Le Misure ad Alta Frequenza per le
Applicazioni di Signal Integrity
Prof. Andrea Ferrero
Dip. Elettronica- Politecnico di Torino
Summary
•
•
•
•
•
•
Signal Integrity and Microwave
S-parameter: so what?
VNA Hardware Evolution
Error Models and Calibration Techniques
Interconnection and Fixture Design
Calibration design for the DUT
Le Misure ad Alta Frequenza per la Applicazioni di Signal
Integrity. A. Ferrero- Scuola di Dottorato I.Gorini 2011
Signal Integrity and Microwave
Le Misure ad Alta Frequenza per la Applicazioni di Signal
Integrity. A. Ferrero- Scuola di Dottorato I.Gorini 2011
Microwave Measurements
• Power Measurements
• Time Domain Signals
• Frequency Domain Linear Parameters:
– S parameters
Le Misure ad Alta Frequenza per la Applicazioni di Signal
Integrity. A. Ferrero- Scuola di Dottorato I.Gorini 2011
Few Remainders
Le Misure ad Alta Frequenza per la Applicazioni di Signal
Integrity. A. Ferrero- Scuola di Dottorato I.Gorini 2011
6
Few Remainders
• Linear Network: The ratio among voltages and currents
on the n ports DOES NOT depend on signal levels thus
the behaviour can be described as linear relationship
ie:
1
2
[M]
3
[M] becomes a
4 4x4 matrix
• Where M can be any relationship among any linear
combination of voltages and currents ie:
– V=Z * I
– I=Y*V
Here Y and Z are two examples of possible M matrix but
anyone is acceptable
Le Misure ad Alta Frequenza per la Applicazioni di Signal
Integrity. A. Ferrero- Scuola di Dottorato I.Gorini 2011
7
Scattering Paremeters Demystified
• Let’s take the following combinations of I and V:
V  ZR I
V  ZR I
a
,b 
ZR
ZR
• Where ZR is a parameter called Reference Impedance
than the Ohm law equivalent becomes:
V  RI  b  a
 is called Reflection
Coefficient

R  ZR

R  ZR
Le Misure ad Alta Frequenza per la Applicazioni di Signal
Integrity. A. Ferrero- Scuola di Dottorato I.Gorini 2011
Scattering Paremeters Demystified
• Let’s move to n-ports everything become
vectors and matricies:
 v1 
 i1 
 a1 
 b1 
v 
i 
a 
b 
v   2 , i   2 , a   2  , b   2 
 . 
.
 . 
 . 
 
 
 
 
v
i
a
 n
 n
 n
bn 

v  Zi  b  Sa
S is called Scattering
matrix
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Integrity. A. Ferrero- Scuola di Dottorato I.Gorini 2011
Signal Trasmission at High Frequency
• A structure where the Electromagnetic field
can propagate along an axis with a UNIFORM
transversal section is called Trasmission Line
Coax cable
Waveguide
Bifilar Line
IT’S ALL ABOUT FIELD CONFINEMENT
Le Misure ad Alta Frequenza per la Applicazioni di Signal
Integrity. A. Ferrero- Scuola di Dottorato I.Gorini 2011
Microstrip
So why S and not Z or Y?
Let’s take a transmission line:
I(z)
V(z)
l
Plane A
Plane B
z
• V and I are complex function of the position
while if:
Incident signal
•Zr = Appropriate constant of the
propagation called Line Characteristic
impedance Z then:

Reflected signal
• a and b function along the line become
simply:
a( z )  a(0)e  jkz , b( z )  b(0)e  jkz
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Integrity. A. Ferrero- Scuola di Dottorato I.Gorini 2011
11
Some usefull properties
a(z)
b(z)
Note that:
I(z)
Z
V(z)
if
Z  Z  Z R
b(l )
R  ZR
 (l ) 

a (l )
R  ZR

Z  Z R

 0  b(l )  b(0)  0
Z  Z R

b(0)
b(l )  2 jkl
 ( 0) 

e
0
a ( 0)
a (l )
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Integrity. A. Ferrero- Scuola di Dottorato I.Gorini 2011
12
The S-matrix of a transmission line
a1
a2
Z  Z R
b1
b2
l
Port 1
Port 2
s a   b  s a  s a
b  s
b  Sa   1    11 12   1    1 11 1 12 2
b2   s21 s22  a2  b2  s21a1  s22a2

s11 
b1
a1 a
 0, s21 
2 0
b2
a1 a
 e  jkl , s12 
2 0
b1
a2
 e  jkl , s22 
a1 0
b2
a2
0
a1 0
z
 0
S    jkl
e
So to completely describe the propagation along a trasmission line
we will need:
REFERENCE PLANES
REFERENCE IMPEDANCE
S-MATRIX
Le Misure ad Alta Frequenza per la Applicazioni di Signal
Integrity. A. Ferrero- Scuola di Dottorato I.Gorini 2011
e  jkl 

0 
Differential S-parameters
• What if instead of single ended voltages and
currents we wish to use differential ones and
associate the information to a couple of wires ?
I1
V1
V3
I2
V2
I3
I4
V4
Le Misure ad Alta Frequenza per la Applicazioni di Signal
Integrity. A. Ferrero- Scuola di Dottorato I.Gorini 2011
For Each Couple
V
djk
V
cjk
I
djk
I
cjk




V V
j k
(V V ) / 2
j k
(I  I ) / 2
j k
(I  I )
j k
14
WHY differential S-parameters?
• The differential mode Ed propagates mainly in the air
thus it suffers much less of dielectric loss and
anysotrtopy
• FR4 is a must for Digital application but FR4 is lossy
and anysotropic thus…
• Differental propagation became a must for high
speed digital systems
Le Misure ad Alta Frequenza per la Applicazioni di Signal
Integrity. A. Ferrero- Scuola di Dottorato I.Gorini 2011
Differential S-parameters
• What are the propagation properties and is it
usefull to have an “S-parameter equivalent”?
• Use a linear combination of V and I it’s just
another convention but to link it to
propagation became more tricky:
– Which Reference impedance we need to take?
– What if we wish to have some port left single
ended, i.e. an Operational Amplifier?
– Which are the properties of the new parameters?
Le Misure ad Alta Frequenza per la Applicazioni di Signal
Integrity. A. Ferrero- Scuola di Dottorato I.Gorini 2011
16
Mixed Mode S-parameter
• Traditional definitions are:
1
2
1

2
1

2
1

2
adjk 
bdjk
acjk
bcjk
( a j  ak )
( b j  bk )
BUT THESE ARE VALID
ONLY IF
( a j  ak )
Zcjk 
( b j  bk )
Zdjk
R
Real Only
2
 2R Real Only


S  MSM 1
Le Misure ad Alta Frequenza per la Applicazioni di Signal
Integrity. A. Ferrero- Scuola di Dottorato I.Gorini 2011
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Generalized Mixed Mode
I1
• In general we may have
adjk 
Rdjk
bdjk 
Rdjk
acjk 
bcjk 
Rcjk
Rcjk
I d 12
V d 12
I c1 2
V c1 2
Vdjk  I djk Z djk
I2
V2
2 Z djk
Vdjk  I djk Z djk
V1
p dif fe r e ntia l por ts
2 Z djk
I p-1
Vcjk  I cjk Z cjk
I d (p -1 ) p
V d (p -1 ) p
I c( p -1 )p
V c( p -1 )p
2 Z cjk
Vp-1
Ip
Vcjk  I cjk Z cjk
Vp
2 Z cjk
Ip+1

  (Ξ  Ξ S)(Ξ  Ξ S)  1
S
21
22
11
12
n-ports
Vp+1
n- p single e nde d por ts
In
Vn
BILINEAR MATRIX TRANSFORM
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Integrity. A. Ferrero- Scuola di Dottorato I.Gorini 2011
18
Impedance Measurements
R
Z
| |,F
Le Misure ad Alta Frequenza per la Applicazioni di Signal
Integrity. A. Ferrero- Scuola di Dottorato I.Gorini 2011
?
Impedance Measurements
R
Z
| |,F
Le Misure ad Alta Frequenza per la Applicazioni di Signal
Integrity. A. Ferrero- Scuola di Dottorato I.Gorini 2011
?
Let’s move to microwave
DownConversion and
Digitizing
ADC
ADC
Directional
Coupler
aa
Microwave
Source
bb
a
<-b

Le Misure ad Alta Frequenza per la Applicazioni di Signal
Integrity. A. Ferrero- Scuola di Dottorato I.Gorini 2011
2 port Measurements
 v1   z11
V  ZI     
v2   z21

v1
v2
z11 
, z21 
i1 i 0
i1
2
z12   i1 
z22  i2 
v1
v2
, z12 
, z22 
i2 i 0
i2
i 0
2
Le Misure ad Alta Frequenza per la Applicazioni di Signal
Integrity. A. Ferrero- Scuola di Dottorato I.Gorini 2011
1
i1 0
2 port Measurements
 b1   s11 s12   a1 
b  Sa     
 a 
b
s
s
 2   21 22   2 

b1
s11 
a1 a
S11
a1
2
b2
, s21 
a1
0
a2
b1
, s12 
a2
0
a1
b1
Le Misure ad Alta Frequenza per la Applicazioni di Signal
Integrity. A. Ferrero- Scuola di Dottorato I.Gorini 2011
b2
, s22 
a2
a 0
1
a1 0
S21
b2
The old questions of S-parameter Measurements
•
•
•
•
How can we generate microwave signals?
How can we sample microwave signals?
Where’s the reference plane ?
What’s the reference impedance?
Le Misure ad Alta Frequenza per la Applicazioni di Signal
Integrity. A. Ferrero- Scuola di Dottorato I.Gorini 2011
Plus new problems… for digital Low cost application
• How do I keep reasonable microwave signals
on non microwave substrate ?
• How can I make proper interconnections to
measure these signals ?
• How much accuracy can I accept ?
Le Misure ad Alta Frequenza per la Applicazioni di Signal
Integrity. A. Ferrero- Scuola di Dottorato I.Gorini 2011
VNA BASIC SCHEME
IF Digitizer
FOUR-CHANNEL MICROWAVE RECEIVER
am1
bm1
bm2
am2
DUT
PORT 1
BIAS 1
PORT 2
SIGNAL SEPARATION
BIAS 2
REFLECTOMETER
MICROWAVE
SOURCE
Le Misure ad Alta Frequenza per la Applicazioni di Signal
Integrity. A. Ferrero- Scuola di Dottorato I.Gorini 2011
26
VNA Source
• Synthetised Source (PLL+DDS)
•Very Broadband
•Very Fast Sweeping
•Power Leveled
•Low Phase Noise Not really Necessary
•High Repeatability
Agilent PNA Source block
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Integrity. A. Ferrero- Scuola di Dottorato I.Gorini 2011
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Signal Separation
•Provides a and b waves
separation
•Provides signal
excitation at DUT ports
•It may have also bias
tee and attenuators
bm1
am1
am2
bm2
MICROWAVE
SOURCE
Le Misure ad Alta Frequenza per la Applicazioni di Signal
Integrity. A. Ferrero- Scuola di Dottorato I.Gorini 2011
Receiver Block
• Typically two or three
downconversion
• Digital vectorial
measurement of mag and
phase
• Phase lock of the internal
source through receiver
signals
Le Misure ad Alta Frequenza per la Applicazioni di Signal
Integrity. A. Ferrero- Scuola di Dottorato I.Gorini 2011
Phase Lock through its receiver
Unlike the old VNA where the
source was autonomuos locked
and the receiver could be lock to
any microwave signal, modern
VNAs cannot work unless
their internal source is used.
As example:
You cannot use a VNA to measure
the signal coming out from a chip
where it’s clock cannot be lock to
an external refenrence
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Integrity. A. Ferrero- Scuola di Dottorato I.Gorini 2011
Today VNA Hardware:
4 Ports
4 Ref
4 Rec
2-ports
2 Ref
2 Rec
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Are 4 ports VNA enough?
Ex. Package/Socket footprint
Port 4 & Port 10
Port 2 & Port 8
Port 6 & Port 12
GNDs
Port 1 & Port 7
Port 5 & Port 11
Port 3 & Port 9
Ports 1-6 are on the socket bottom
Ports 7-12 are on the socket top
 Differential pairs are used so:
 12-port data is required for channel modeling
 Data for a fully characterized 12-port DUT results in a
completely filled 12x12 matrix
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Integrity. A. Ferrero- Scuola di Dottorato I.Gorini 2011
12 ports VNA
2 Ref
2 Switched Rec
LEFT
PORTS
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Integrity. A. Ferrero- Scuola di Dottorato I.Gorini 2011
RIGHT
PORTS
33
12 ports VNA
2 Ref
2 Switched Rec
LEFT
PORTS
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Integrity. A. Ferrero- Scuola di Dottorato I.Gorini 2011
RIGHT
PORTS
Interfacing
• Repeatibility
• Custom Fixtures
• Standard Availability
Le Misure ad Alta Frequenza per la Applicazioni di Signal
Integrity. A. Ferrero- Scuola di Dottorato I.Gorini 2011
On Wafer
Le Misure ad Alta Frequenza per la Applicazioni di Signal
Integrity. A. Ferrero- Scuola di Dottorato I.Gorini 2011
Let’s summarize up to now
1.
2.
3.
4.
Directional Couplers have finite directivity and frequency depend
behaviour
Switches are not ideal and frequency dependent
Reference Plane position depends on cable, adapter
interconnections and so on
DownConversion and Digitizing problems like:
1.
2.
3.
4.
Source Phase Noise
Frequency accuracy and repeatibility
Non linearity of mixer/sampler
ADC Dynamic Range & Speed
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Integrity. A. Ferrero- Scuola di Dottorato I.Gorini 2011
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Cause of Uncertainty
• Systematic Errors (85%)
–
–
–
–
Microwave Components
Interconnections
Incorrect Standard Modeling
Calibration Algorithm
• Random Error (10%)
– Connection Repeatibility
– Frequency Stability
– Noise
• Drift (5%)
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Integrity. A. Ferrero- Scuola di Dottorato I.Gorini 2011
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Is Calibration fundamental?
• What if we would measure 30g of Ham with
the scale plate of 1 ton?
THIS IS THE SAME EFFECT OF
looking for
1m cable at 10GHz if we are
1 degree of phase shift on S11
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Integrity. A. Ferrero- Scuola di Dottorato I.Gorini 2011
Raw vs. Corrected Data
Le Misure ad Alta Frequenza per la Applicazioni di Signal
Integrity. A. Ferrero- Scuola di Dottorato I.Gorini 2011
How does the calibration work?
An error
model
A Specific
Algorithm
Le Misure ad Alta Frequenza per la Applicazioni di Signal
Integrity. A. Ferrero- Scuola di Dottorato I.Gorini 2011
A Standard
Sequence
Error Model
• Ipothesis
1. sampler (mixer),and all the other system components are
linear and invariant parts
2. The two half
are independent 4-port networks
which “talk” only through the DUT
am1
•
•
•
•
Let the half
8 unknowns:
a0, b0, a1, b1,a3, b3, a4, b4
The two acquire data are
proportional to b3, b4 :
am1=k1b3 , bm1=k2b4
b3 a3
bm1
b4 a4
DUT
b0
a0
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b1
a2
a1
b2
42
Error Model Definition II
b0   S 11
  
b1    S 21
b3   S 31
  
b4   S 41
a 3  Γ 3b 3
a 4  Γ 4b 4
S 12
S 22
S 32
S 42
S 13
S 23
S 33
S 43
S 14  a 0 
 
S 24  a1 
S 34  a 3 
 
S 44  a 4 
V m 1  k 3b3
V m 2  k 4b 4
4 port equation
Reflection Coefficients of the
downconversion part and
reading vs. wave
8 eq. with 10 unknowns. (a0, b0, a1, b1, a3, b3, a4, b4, Vm1, Vm2):
Let use Vm1 e V m2 as independent variables and called them:
am1=Vm1, bm1=Vm2, a1= a1DUT e b1= b1DUT we find the following model
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Error Model Definition III
b0   S 11
  
b1    S 21
b3   S 31
  
b4   S 41
S 12
S 22
S 32
S 42
S 13
S 23
S 33
S 43
b0
b1
b3
 S11a0
 S 21a0
 S31a0
 S12a1
 ....
 ....
b4
 S 41a0
 ....
S 14  a 0 
 
S 24  a1 
S 34  a 3 
 
S 44  a 4 
 S13a3
a 3  Γ 3b 3
a 4  Γ 4b 4
 S14a4
 S 44a4
b0
b1
b3
 S11a0
 S 21a0
 S31a0
 S12a1
 ....
 ....
 S133b3
 S 233b3
 S333b3
 S144b4
 S 244b4
 S344b4
b4
 S 41a0
 ....
 S 433b3
 S 444b4
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Error Model Definition IV
 S11a0
 S 21a0
 S31a0
 b0
 S 41a0
 S12a1
 S12a1
 S32a1
 S 42a1
 b1

S133b3

S 233b3
 ( S 233  1)b3




 ( S 444  1)b4
S 433b3
S144b4
S 244b4
S344b4
If we call am1 and bm1
  S11
 S
 21
 S31

 S 41
1  S12
0  S 22
0  S32
0  S 42
S144 
0 a0   S133
S 244  b3 
1 b0   S 233

S344  b4 
0  a1  ( S333  1)

  
( S 444  1)
0  b1   S 433
a0 
b 
b 
W 0   Q 3 
 a1 
b4 
 
b1 

Le Misure ad Alta Frequenza per la Applicazioni di Signal
Integrity. A. Ferrero- Scuola di Dottorato I.Gorini 2011
Vm1  am1  k3b3
Vm 2  bm1  k 4b4
am1  k1
b   
 m1   0
0  b3 
 
k2  b4 
45
The famous error box
a0 
b 
b3 
0

W
 Q 
 a1 
b4 
 
 b1 
am1  k1
b   
 m1   0
a0 
b 
 0   W 1QK 1 am1   Dam1 
b 
b 
 a1 
 m1 
 m1 
 
 b1 
0  b3 
b3 
   K 
k2  b4 
b4 
a0
b0
a1
 D11am1
 D21am1
 D31am1
 D12bm1
 D22bm1
 D32bm1
b1
 D41am1
 D42bm1
Shuffle the last 2
Equations and
rename as
bm1
a1
Le Misure ad Alta Frequenza per la Applicazioni di Signal
Integrity. A. Ferrero- Scuola di Dottorato I.Gorini 2011
 e11am1
 e21am1
 e12b1
 e22b1
46
The birth of the famous error box
Since we are in the S-parameter world the LINEAR RELATIONSHIP WHICH LINKS THE
MEASUREMENT TO THE ACTUAL WAVES WILL BE
bm1
a1


e11am1
e21am1
am1
Ideal
VNA


e12b1
e22b1
a1
Error
Box
E
bm1
Le Misure ad Alta Frequenza per la Applicazioni di Signal
Integrity. A. Ferrero- Scuola di Dottorato I.Gorini 2011
DUT
b1
47
Error Box Property
• It’s not an actual network but only a linear system model
• Every parameter is frequency dependent but time invariant
• Since the E parameters are more or less link with some
specifications of the coupler they are also called:
e11  ED
e22  ES
e21e12  ER

Directivit y
 SourceMatch

Le Misure ad Alta Frequenza per la Applicazioni di Signal
Integrity. A. Ferrero- Scuola di Dottorato I.Gorini 2011
Tracking
48
Two Port Error Model
Two error boxes on the right and left
a1m
a1DUT
b2DUT
b1m
b1DUT
a2DUT
TA
TDUT
2-ports Measured
S-matrix
b
Sm  mi
ij a
mj a
0
NOT POSSIBLE mi  j
b2m
-1
B
T
a2m
To apply this model, 4
independent readings
on each source position
are required
 bm1 
 am1 
b   Sm a 
 m2 
 m2 
b1'm   S 11m S 12m  a1' m 
 ' 
 ' ,
S
S
b2m   21m 22m  a 2m 
b1"m   S 11m S 12m  a1"m 
 " 
 " 
b2m   S 21m S 22m  a 2m 
 S 11m S 12m   b1'm b1"m   a1' m a1"m 
 '
S

"  '
" 
S
b
b
a
a
 21m 22m   2m 2m   2m 2m 
Le Misure ad Alta Frequenza per la Applicazioni di Signal
Integrity. A. Ferrero- Scuola di Dottorato I.Gorini 2011
1
49
FULL 2-Ports Error Model
1
b
b1DUT  T A11 T A12  b1m 
1  1m 
a
  T T  a   T A a 
 1m 
 1DUT   A 21 A 22   1m 
1
8 error terms, but
a
a2DUT  T B 11 T B 12  a2m 
1  2m 
b
  T T  b   T B b 
 2m 
 2DUT   B 21 B 22   2m 
7 UNKNOWS TO GET
Tdut
TA, TB are the transmission matrix equivalent of the two E matrices of left
and right side while Tm is the transmission matrix equivalent of Sm
bm1 
am 2 
a   Tm b 
 m1 
 m2 
Le Misure ad Alta Frequenza per la Applicazioni di Signal
Integrity. A. Ferrero- Scuola di Dottorato I.Gorini 2011
a
b1m 
1  2m 

  T ATDUT TB 

a1m 
b2m 
50
Most USED 2-port Calibrations
• TSD-TRL (Thru, Short, Delay or Thru, Reflect,
Line)
• LRM (Line, Reflect, Match)
• SOLR (Short, Open, Load, Reciprocal)
• SOLT (Short, Open, Load, Thru)
MANDATORY FOR 3 samplers VNAs
Le Misure ad Alta Frequenza per la Applicazioni di Signal
Integrity. A. Ferrero- Scuola di Dottorato I.Gorini 2011
51
SOLT
• The old good cal: Short, Open, Load and Thru
• It measures 3 standards at port 1, 3 at port 2
and the THRU.
• It obviously overdetermed with the 8 port
model (10 equations for 8 unknows)but it’s
the proper choice for the 3-sampler
architecture
Le Misure ad Alta Frequenza per la Applicazioni di Signal
Integrity. A. Ferrero- Scuola di Dottorato I.Gorini 2011
52
Thru Reflect Line
• The Thru and Line must have the same
geometry
I.e. REFERENCE IMPEDANCE
• Normally the Reference plane it’s placed in
the middle of the THRU
• The system Reference impedance IS THE
Characteristic impedance of the LINE
• Known 1 port Standard TSD
• Unknown 1 port standard -> TRL
Le Misure ad Alta Frequenza per la Applicazioni di Signal
Integrity. A. Ferrero- Scuola di Dottorato I.Gorini 2011
53
TSD-TRL II
• The length diff from the THRU
and the LINE should avoid l/2
and its multiple
• To have broadband TRL more
line are usefull (different line
lenght)
• Side Result: The propagation
constant of the line comes
from free
54
Coax On-Board Simple Calibration Structures
Thru and Line
Structures
Reflect and Match
Structures
Le Misure ad Alta Frequenza per la Applicazioni di Signal
Integrity. A. Ferrero- Scuola di Dottorato I.Gorini 2011
55
Le Misure ad Alta Frequenza per la Applicazioni di Signal
Integrity. A. Ferrero- Scuola di Dottorato I.Gorini 2011
VNA Noise
THE GOOD OLD 8510:RAW DATA NOISE
-50dB ->
-50dB ->
Le Misure ad Alta Frequenza per la Applicazioni di Signal
Integrity. A. Ferrero- Scuola di Dottorato I.Gorini 2011
Repeatability an example:APC7mm
A close look to the
connector
Le Misure ad Alta Frequenza per la Applicazioni di Signal
Integrity. A. Ferrero- Scuola di Dottorato I.Gorini 2011
58
Repeatibility Model
Le Misure ad Alta Frequenza per la Applicazioni di Signal
Integrity. A. Ferrero- Scuola di Dottorato I.Gorini 2011
Multifinger On wafer probes
• Probe landing repeatibility
• Probe Coupling
Le Misure ad Alta Frequenza per la Applicazioni di Signal
Integrity. A. Ferrero- Scuola di Dottorato I.Gorini 2011
Standard Accuracy
• Standard Model
• Model Identification
• Parameter Accuracy
Le Misure ad Alta Frequenza per la Applicazioni di Signal
Integrity. A. Ferrero- Scuola di Dottorato I.Gorini 2011
Standard Model: Open
C  C0  C1 f  C2 f  C3 f
2
t,g
•How do we get Cj ?
•FEM Methods which are
based on mechanical
dimensions
Le Misure ad Alta Frequenza per la Applicazioni di Signal
Integrity. A. Ferrero- Scuola di Dottorato I.Gorini 2011
3
Apc7mm Open
Repeatability effects
Le Misure ad Alta Frequenza per la Applicazioni di Signal
Integrity. A. Ferrero- Scuola di Dottorato I.Gorini 2011
Standard Model: 40ps line
Le Misure ad Alta Frequenza per la Applicazioni di Signal
Integrity. A. Ferrero- Scuola di Dottorato I.Gorini 2011
Multiport VNA Calibration
•
•
•
•
A new errror model is necessary
Multiport standard may be required
Calibration Algorithm must be found
Cannot be a simple extension of the 2 port
ones
Le Misure ad Alta Frequenza per la Applicazioni di Signal
Integrity. A. Ferrero- Scuola di Dottorato I.Gorini 2011
Multiport Calibration
We do not have
multiport
standards
We may not
have Thrus
We cannot
connect one port
to any others
Le Misure ad Alta Frequenza per la Applicazioni di Signal
Integrity. A. Ferrero- Scuola di Dottorato I.Gorini 2011
Classical multiport error model
 Complete reflectometer
multiport architecture: two
directional couplers @ each
port
 Error box extension as
1 0
0 k
22

K  


0 
 
0
m11 0
h11 0   0 
l11 0   0 
 0 m
0 h

0 l

 


22
22
22






  L

  M 

 H






 0


0


0




 
 0
 0   0 lnn 
 0
 0 k nn 
  0 hnn 

4n -1 unknowns
Le Misure ad Alta Frequenza per la Applicazioni di Signal
Integrity. A. Ferrero- Scuola di Dottorato I.Gorini 2011
 
0 
 

 

 0 
 0 mnn 
67
Partial Reflectometer error model
 Partial reflectometer
multiport architecture: two
directional couplers @ each
port are not always available
 This architecture has the
advantages of costs (n-2
couplers are saved) and
speed
 The model for these case must be:
 of general validity (i.e. not valid for only one calibration algorithm and scalable)
 compatible with the complete reflectometer one
 easy to be calibrated
Le Misure ad Alta Frequenza per la Applicazioni di Signal
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68
The new formulation
 The partial reflectometer multiport system has two states, for each i
port:
STATE A
Le Misure ad Alta Frequenza per la Applicazioni di Signal
Integrity. A. Ferrero- Scuola di Dottorato I.Gorini 2011
STATE B
69
The cal equation becomes
• And the de-embedding is:
6n -1 unknowns
 Based on S parameters
 Always defined for any standards
 Can be used to find H,L,M,K,F,G during the cal
 As well as to find dut S matrix during the measurement
“A Novel Calibration Algorithm for a Special Class of Multiport Vector Network Analyzers”,Ferrero, A.; Teppati, V.; Garelli, M.; Neri, A.
IEEE Transactions on Microwave Theory and Techniques, Volume 56, Issue 3, March 2008
Le Misure ad Alta Frequenza per la Applicazioni di Signal
Integrity. A. Ferrero- Scuola di Dottorato I.Gorini 2011
70
Dynamic Calibration
Since no constrains are given on the standard type and
the math can combine whatever sequence, the
calibration becomes dynamic i.e. the software can
generate the standard sequence which gives a set of
enough linear independent equations as well as it
accomplished for:
–
–
–
–
Connectors at each ports
Available standards USE ONLY 1 or 2 ports ONES !!
User interconnection description
Use of particular two port pairs self calibration
Le Misure ad Alta Frequenza per la Applicazioni di Signal
Integrity. A. Ferrero- Scuola di Dottorato I.Gorini 2011
71
Example: Design CAL for the DUT
P_2
P_1
P_4
P_3
Le Misure ad Alta Frequenza per la Applicazioni di Signal
Integrity. A. Ferrero- Scuola di Dottorato I.Gorini 2011
72
An Example a Socket Measurement
Le Misure ad Alta Frequenza per la Applicazioni di Signal
Integrity. A. Ferrero- Scuola di Dottorato I.Gorini 2011
8-ports Socket Setup
Le Misure ad Alta Frequenza per la Applicazioni di Signal
Integrity. A. Ferrero- Scuola di Dottorato I.Gorini 2011
Calibration Design
LSM
P1
P5
Rec
P2
LSM
LSM
P6
Rec
P3
P7
Rec
P4
Le Misure ad Alta Frequenza per la Applicazioni di Signal
Integrity. A. Ferrero- Scuola di Dottorato I.Gorini 2011
LSM
P8
8-Port LRM/LSM Multi-Calibration Matrix with Reciprocal Thrus
•
Port 1
Port 2
Port 3
Port 4
Port 5
Port 6
Port 7
Port 8
Port 1
X
Recip
X
X
2P_LSM
X
X
X
Port 2
Recip
X
X
X
X
2P_LSM
X
X
Port 3
X
X
X
Recip
X
X
2P_LSM
X
Port 4
X
X
Recip
X
X
X
X
2P_LSM
Port 5
2P_LSM
X
X
X
X
X
X
X
Port 6
X
2P_LSM
X
X
X
X
Recip
X
Port 7
X
X
2P_LSM
X
X
Recip
X
X
Port 8
X
X
X
2P_LSM
X
X
X
X
4 separate 2-port LSM/LRM calibrations linked with
Calibration Procedure:
reciprocal thru standards
– Thru Port 1, 5
– Thru Port 2, 6
Structure 1
• No wasted probe touchdowns
– Thru Port 3, 7
– Thru Port 4, 8
• Never move probe tips in x or y direction
– Recip 1, 2
Structure 2
– Recip 3, 4
• Full characterization of every port
– Recip 6, 7
• Could provide more accurate calibrations
– Reflect Port 1, Reflect Port 5
– Reflect Port 2, Reflect Port 6
Structures 3
– Reflect Port 3, Reflect Port 7
– Reflect Port 4, Reflect Port 8
– Load Port 1, Load Port 5
– Load Port 2, Load Port 6
Structures 4
– Load Port 3, Load Port 7
– Load Port 4, Load Port 8
8-Port LRM/LSM Standards
(Probe tip Calibration)
Probe Touchdown
1
Probe Touchdown 3
1
5
1
5
2
6
2
6
3
7
3
7
4
8
4
8
X Length
X
Length
Probe Touchdown
4
Probe Touchdown
2
1
5
2
6
7
3
7
8
4
8
1
5
2
6
3
4
Le Misure ad Alta Frequenza per la Applicazioni di Signal
Integrity. A. Ferrero- Scuola di Dottorato
I.Gorini
2011 tip
Minimize
probe
Xtalk
GND
SIG
TERM
Socket/Board Setup Close-up
On Socket PROBES
Land Places
Cal Standards
On Board PROBES
Land Places
Le Misure ad Alta Frequenza per la Applicazioni di Signal
Integrity. A. Ferrero- Scuola di Dottorato I.Gorini 2011
Socket-Board Data
SDD11-SDD22-SDD33-SDD44
Le Misure ad Alta Frequenza per la Applicazioni di Signal
Integrity. A. Ferrero- Scuola di Dottorato I.Gorini 2011
Socket-Board Data
SDD12 - SDD34
Le Misure ad Alta Frequenza per la Applicazioni di Signal
Integrity. A. Ferrero- Scuola di Dottorato I.Gorini 2011
Socket-Board Data
SD14 – SD23 (Far End Xtalk)
Le Misure ad Alta Frequenza per la Applicazioni di Signal
Integrity. A. Ferrero- Scuola di Dottorato I.Gorini 2011
Socket-Board Data
SD13 – SD24 (Near End Xtalk)
Bottom Board
Top Board
Le Misure ad Alta Frequenza per la Applicazioni di Signal
Integrity. A. Ferrero- Scuola di Dottorato I.Gorini 2011
Conclusion
• Modern Calibration Technology solves many
issues in multiport structure S parameter
measurements
• Proper design of the measurement bench
dramatically improves data accuracy
• Modern Software are today available to
handle the measurement complexity
Le Misure ad Alta Frequenza per la Applicazioni di Signal
Integrity. A. Ferrero- Scuola di Dottorato I.Gorini 2011
83
Acknoledgements
• Valeria Teppati, Serena Bonino
Politecnico of Torino
• Marco Garelli
HFE
• Brett Grossmann, Tom Ruttan, Evan Fledell
Intel Corp
• Jon Martens
Anritsu Corp
• Dave Blackham
Agilent
Le Misure ad Alta Frequenza per la Applicazioni di Signal
Integrity. A. Ferrero- Scuola di Dottorato I.Gorini 2011