Seminario d’Eccellenza “ITALO GORINI”
Scuola di Dottorato
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
Seminario d’Eccellenza “ITALO GORINI”
Le Misure ad Alta Frequenza per le Applicazioni di Signal Integrity
MISURE PER LA CARATTERIZZAZIONE DI COMPONENTI E SISTEMI
Prof. Andrea FerreroDip. Elettronica- Politecnico di Torino
Le Misure ad Alta Frequenza per la Applicazioni di Signal Integrity. A. Ferrero- Scuola di Dottorato I.Gorini 2011
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
6
Few Remainders
Le Misure ad Alta Frequenza per la Applicazioni di Signal Integrity. A. Ferrero- Scuola di Dottorato I.Gorini 2011
7
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:
• Where M can be any relationship among any linear combination of voltages and currents ie:– V=Z * I– I = Y * VHere Y and Z are two examples of possible M matrix but
anyone is acceptable
[M] [M] becomes a 4x4 matrix
1
2
3
4
Le Misure ad Alta Frequenza per la Applicazioni di Signal Integrity. A. Ferrero- Scuola di Dottorato I.Gorini 2011
Scattering Paremeters Demystified
• Let’s take the following combinations of I and V:
• Where ZR is a parameter called Reference Impedance than the Ohm law equivalent becomes:
R
R
R
R
Z
IZVb
Z
IZVa
,
R
R
ZR
ZR
abRIV
G is called Reflection Coefficient
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:
SabZiv
baiv
nnnn b
b
b
a
a
a
i
i
i
v
v
v
.,
.,
.,
.2
1
2
1
2
1
2
1
S is called Scattering matrix
Le Misure ad Alta Frequenza per la Applicazioni di Signal 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 Microstrip
EEE
E
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
11
So why S and not Z or Y?
Let’s take a transmission line:
z
I(z)
V(z)
Plane A Plane B• V and I are complex function of the position
while if:• Zr = Appropriate constant of the
propagation called Line Characteristic impedance then:
• a and b function along the line become simply:
Z
jkzjkz ebzbeaza )0()(,)0()(
l
Reflected signalIncident signal
Le Misure ad Alta Frequenza per la Applicazioni di Signal Integrity. A. Ferrero- Scuola di Dottorato I.Gorini 2011
12
Some usefull propertiesNote that:
I(z)
V(z) Z
0)(
)(
)0(
)0()0(
0)0()(0)(
)()(
2
jkl
R
R
R
R
R
ela
lb
a
b
blbZZ
ZZ
ZR
ZR
la
lbl
ZZZ
if
a(z)
b(z)
Le Misure ad Alta Frequenza per la Applicazioni di Signal Integrity. A. Ferrero- Scuola di Dottorato I.Gorini 2011
The S-matrix of a transmission line
zPort 1 Port 2
RZZ
l
0
0jkl
jkl
e
eS
So to completely describe the propagation along a trasmission line we will need:
REFERENCE PLANES
REFERENCE IMPEDANCE
S-MATRIX
0,,,002
222
02
112
01
221
01
111
2221212
2121111
2
1
2221
1211
2
1
1122
a
jkl
a
jkl
aaa
bse
a
bse
a
bs
a
bs
asasb
asasb
a
a
ss
ss
b
bSab
a1
b1
a2
b2
Le Misure ad Alta Frequenza per la Applicazioni di Signal Integrity. A. Ferrero- Scuola di Dottorato I.Gorini 2011
14
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 ?
V1
I1
V2
I2
V3
I3
V4
I4
)(
2/)(
2/)(
kIjIcjk
IkIjIdjk
IkVjVcjk
VkVjVdjk
V
For Each Couple
Le Misure ad Alta Frequenza per la Applicazioni di Signal Integrity. A. Ferrero- Scuola di Dottorato I.Gorini 2011
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
E Ec
Ed
Le Misure ad Alta Frequenza per la Applicazioni di Signal Integrity. A. Ferrero- Scuola di Dottorato I.Gorini 2011
16
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
17
Mixed Mode S-parameter
• Traditional definitions are:
1MSMS
)(
2
1
)(2
1
)(2
1
)(2
1
c
c
d
d
kjjk
kjjk
kjjk
kjjk
bbb
aaa
bbb
aaa
Only Real R2Z
Only Real 2
RZ
d
c
jk
jk
BUT THESE ARE VALID ONLY IF
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
• In general we may have Vd12
Id12
Vc12
Ic12
Vd(p-1)p
Id(p-1)p
Vc(p-1)p
Ic(p-1)p
n-portsp differential ports
n-p single ended ports
Vp-1
Vp+1
Ip+1
Ip
Vn
In
I2
V2
I1
V1
Ip-1
Vp
1)121
)(222
(
2
2
2
2
c
ccccc
c
ccccc
d
ddddd
d
ddddd
SΞ
1ΞSΞ
1ΞS
jk
jkjkjkjkjk
jk
jkjkjkjkjk
jk
jkjkjkjkjk
jk
jkjkjkjkjk
Z
ZIVRb
Z
ZIVRa
Z
ZIVRb
Z
ZIVRa
BILINEAR MATRIX TRANSFORM
Le Misure ad Alta Frequenza per la Applicazioni di Signal Integrity. A. Ferrero- Scuola di Dottorato I.Gorini 2011
Impedance Measurements
R ?
| |,F
Z
Le Misure ad Alta Frequenza per la Applicazioni di Signal Integrity. A. Ferrero- Scuola di Dottorato I.Gorini 2011
Impedance Measurements
R ?
| |,F
Z
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
ADCADC
Directional Coupler
G
aa bb
a<-b
Microwave Source
Le Misure ad Alta Frequenza per la Applicazioni di Signal Integrity. A. Ferrero- Scuola di Dottorato I.Gorini 2011
2 port Measurements
02
222
02
112
01
221
01
111
2
1
2221
1211
2
1
1122
,,,
iiiii
vz
i
vz
i
vz
i
vz
i
i
zz
zz
v
vZIV
Le Misure ad Alta Frequenza per la Applicazioni di Signal Integrity. A. Ferrero- Scuola di Dottorato I.Gorini 2011
2 port Measurements
02
222
02
112
01
221
01
111
2
1
2221
1211
2
1
1122
,,,
aaaaa
bs
a
bs
a
bs
a
bs
a
a
ss
ss
b
bSab
S11 S21a1
b2
a1
b1
Le Misure ad Alta Frequenza per la Applicazioni di Signal Integrity. A. Ferrero- Scuola di Dottorato I.Gorini 2011
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
26
VNA BASIC SCHEME
REFLECTOMETER
bm1am1 bm2 am2
FOUR-CHANNEL MICROWAVE RECEIVER
PORT 1 PORT 2
DUT
MICROWAVESOURCE
BIAS 1 BIAS 2
IF Digitizer
SIGNAL SEPARATION
Le Misure ad Alta Frequenza per la Applicazioni di Signal Integrity. A. Ferrero- Scuola di Dottorato I.Gorini 2011
27
VNA Source
Agilent PNA Source block
• Synthetised Source (PLL+DDS)• Very Broadband• Very Fast Sweeping• Power Leveled• Low Phase Noise Not really Necessary
• High Repeatability
Le Misure ad Alta Frequenza per la Applicazioni di Signal Integrity. A. Ferrero- Scuola di Dottorato I.Gorini 2011
Signal Separation
MICROWAVESOURCE
bm1
am1
bm2
am2
Receiver Block
• Provides a and b waves separation
• Provides signal excitation at DUT ports
• It may have also bias tee and attenuators
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 internalsource through receiversignals
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 thesource was autonomuos lockedand the receiver could be lock to any microwave signal, modernVNAs cannot work unlesstheir internal source is used.As example:You cannot use a VNA to measurethe signal coming out from a chipwhere it’s clock cannot be lock toan external refenrence
Le Misure ad Alta Frequenza per la Applicazioni di Signal Integrity. A. Ferrero- Scuola di Dottorato I.Gorini 2011
Today VNA Hardware:
31
2-ports2 Ref2 Rec
4 Ports4 Ref4 Rec
Le Misure ad Alta Frequenza per la Applicazioni di Signal Integrity. A. Ferrero- Scuola di Dottorato I.Gorini 2011
Are 4 ports VNA enough?
Differential pairs are used so:12-port data is required for channel modelingData for a fully characterized 12-port DUT results in a
completely filled 12x12 matrix
Ex. Package/Socket footprint
Port 1 & Port 7
Port 3 & Port 9
Port 5 & Port 11
Port 2 & Port 8
Port 4 & Port 10
Port 6 & Port 12
Ports 1-6 are on the socket bottomPorts 7-12 are on the socket top
GNDs
Le Misure ad Alta Frequenza per la Applicazioni di Signal Integrity. A. Ferrero- Scuola di Dottorato I.Gorini 2011
12 ports VNA
33
2 Ref
2 Switched Rec
LEFTPORTS
RIGHTPORTS
Le Misure ad Alta Frequenza per la Applicazioni di Signal Integrity. A. Ferrero- Scuola di Dottorato I.Gorini 2011
12 ports VNA
2 Ref
2 Switched Rec
LEFTPORTS
RIGHTPORTS
Le Misure ad Alta Frequenza per la Applicazioni di Signal Integrity. A. Ferrero- Scuola di Dottorato I.Gorini 2011
Interfacing
• Repeatibility• Standard Availability• Custom Fixtures
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. Directional Couplers have finite directivity and frequency depend behaviour
2. Switches are not ideal and frequency dependent3. Reference Plane position depends on cable, adapter
interconnections and so on4. DownConversion and Digitizing problems like:
1. Source Phase Noise2. Frequency accuracy and repeatibility3. Non linearity of mixer/sampler4. ADC Dynamic Range & Speed
37
ACCURACY ???
Le Misure ad Alta Frequenza per la Applicazioni di Signal Integrity. A. Ferrero- Scuola di Dottorato I.Gorini 2011
Lab Care
Calibration
Cause of Uncertainty
• Systematic Errors (85%)– Microwave Components – Interconnections– Incorrect Standard Modeling– Calibration Algorithm
• Random Error (10%)– Connection Repeatibility – Frequency Stability– Noise
• Drift (5%)
38
Le Misure ad Alta Frequenza per la Applicazioni di Signal Integrity. A. Ferrero- Scuola di Dottorato I.Gorini 2011
Is Calibration fundamental?
• What if we would measure 30g of Ham with
the scale plate of 1 ton?
THIS IS THE SAME EFFECT OF 1m cable at 10GHz if we are
looking for 1 degree of phase shift on S11
Le Misure ad Alta Frequenza per la Applicazioni di Signal 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
A Standard Sequence
ExampleTRLThru
ReflectLine
Le Misure ad Alta Frequenza per la Applicazioni di Signal Integrity. A. Ferrero- Scuola di Dottorato I.Gorini 2011
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
42
DUT
b2
a2
a3
b1
a1
a0
b0
b3 a4b4
• 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
am1 bm1
Le Misure ad Alta Frequenza per la Applicazioni di Signal Integrity. A. Ferrero- Scuola di Dottorato I.Gorini 2011
Error Model Definition II
0 011 12 13 14
1 121 22 23 24
31 32 33 343 3
41 42 43 444 4
b aS S S Sb aS S S S
S S S Sb aS S S Sb a
43
4 port equation
Reflection Coefficients of the downconversion part and reading vs. wave
3 3
4 4
a b
a b3
4
Γ
Γ
1 3 3
2 4 4
m
m
V k b
V k b
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
Le Misure ad Alta Frequenza per la Applicazioni di Signal Integrity. A. Ferrero- Scuola di Dottorato I.Gorini 2011
Error Model Definition III
0 011 12 13 14
1 121 22 23 24
31 32 33 343 3
41 42 43 444 4
b aS S S Sb aS S S S
S S S Sb aS S S Sb a
44
4440414
0313
0211
4143131120110
....
....
....
aSaSb
aSb
aSb
aSaSaSaSb
444433430414
443433330313
442433230211
441433131120110
....
....
....
bSbSaSb
bSbSaSb
bSbSaSb
bSbSaSaSb
3 3
4 4
a b
a b3
4
Γ
Γ
Le Misure ad Alta Frequenza per la Applicazioni di Signal Integrity. A. Ferrero- Scuola di Dottorato I.Gorini 2011
Error Model Definition IV
45
44443343142041
44343323132031
442433231112021
441433131120011
)1(
)1(
bSbSaSaS
bSbSaSaS
bSbSbaSaS
bSbSaSbaS
4
3
444343
434333
424323
414313
1
1
0
0
4241
3231
2221
1211
)1(
)1(
00
00
10
01
b
b
SS
SS
SS
SS
b
a
b
a
SS
SS
SS
SS
4
3
1
1
0
0
b
b
b
a
b
a
QW
4412
3311
bkbV
bkaV
mm
mm
If we call am1 and bm1
4
3
2
1
1
1
0
0
b
b
k
k
b
a
m
m
Le Misure ad Alta Frequenza per la Applicazioni di Signal Integrity. A. Ferrero- Scuola di Dottorato I.Gorini 2011
The famous error box
46
4
3
1
1
0
0
b
b
b
a
b
a
QW
4
3
4
3
2
1
1
1
0
0
b
b
b
b
k
k
b
a
m
m K
1421411
1321311
1221210
1121110
mm
mm
mm
mm
bDaDb
bDaDa
bDaDb
bDaDa
1
1
1
11
1
1
0
0
m
m
m
m
b
a
b
a
b
a
b
a
DQKW 1
1221211
1121111
beaea
beaeb
m
mm
Shuffle the last 2 Equations and rename as
Le Misure ad Alta Frequenza per la Applicazioni di Signal Integrity. A. Ferrero- Scuola di Dottorato I.Gorini 2011
The birth of the famous error box
47
am1a1
IdealVNA
bm1
ErrorBoxE
b1
DUT
1221211
1121111
beaea
beaeb
m
mm
Since we are in the S-parameter world the LINEAR RELATIONSHIP WHICH LINKS THE MEASUREMENT TO THE ACTUAL WAVES WILL BE
Le Misure ad Alta Frequenza per la Applicazioni di Signal Integrity. A. Ferrero- Scuola di Dottorato I.Gorini 2011
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:
48
TrackingEee
hSourceMatcEe
yDirectivitEe
R
S
D
1221
22
11
Le Misure ad Alta Frequenza per la Applicazioni di Signal Integrity. A. Ferrero- Scuola di Dottorato I.Gorini 2011
Two Port Error Model
49
To apply this model, 4 independent readings on each source position are required
NOT POSSIBLE
TA TDUT T-1B
a1m
b1m
a1DUT
b1DUT
b2DUT
a2DUT
b2m
a2m
Two error boxes on the right and left
2
1
2
1
m
m
m
m
a
a
b
bSm
' ' " "1 1 1 111 12 11 12
' ' " "21 22 21 222 2 2 2
,m m m mm m m m
m m m mm m m m
b a b aS S S SS S S Sb a b a
1' " ' "11 12 1 1 1 1
' " ' "21 22 2 2 2 2
m m m m m m
m m m m m m
S S b b a aS S b b a a
2-ports Measured S-matrix
0m
m
m
jiaj
ai
b
ijSm
Le Misure ad Alta Frequenza per la Applicazioni di Signal Integrity. A. Ferrero- Scuola di Dottorato I.Gorini 2011
FULL 2-Ports Error Model
11 1 1111 12
21 221 1 1
DUT m mA AA
A ADUT m m
b b bT TT
T Ta a a
50
1
2 2 2111 12
21 222 2 2
DUT m mB BB
B BDUT m m
a a aT TT
T Tb b b
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
1 21
1 2
m mA DUT B
m m
b aT T T
a b
2
2
1
1
m
m
m
m
b
a
a
bTm
8 error terms, but
7 UNKNOWS TO GET Tdut
Le Misure ad Alta Frequenza per la Applicazioni di Signal Integrity. A. Ferrero- Scuola di Dottorato I.Gorini 2011
51
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
52
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
53
Thru Reflect Line
• The Thru and Line must have the same geometryI.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
54
TSD-TRL II
• The length diff from the THRU and the LINE should avoid /2l 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
Le Misure ad Alta Frequenza per la Applicazioni di Signal Integrity. A. Ferrero- Scuola di Dottorato I.Gorini 2011
55
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
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
58
A close look to theconnector
Le Misure ad Alta Frequenza per la Applicazioni di Signal Integrity. A. Ferrero- Scuola di Dottorato I.Gorini 2011
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
,t g
33
2210 fCfCfCCC
• 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
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 cannot connect one port
to any others
We may not have Thrus
What if:
?Calibration cannot be based on
a fixed sequence A general formulation must be
found !
Le Misure ad Alta Frequenza per la Applicazioni di Signal Integrity. A. Ferrero- Scuola di Dottorato I.Gorini 2011
Classical multiport error model
67
nnm
m
m
00
0
0
00
22
11
M
nnk
k
00
0
0
001
22
K
nnh
h
h
00
0
0
00
22
11
H
nnl
l
l
00
0
0
00
22
11
L
Complete reflectometer multiport architecture: two directional couplers @ each port
Error box extension as
4n -1 unknowns
Le Misure ad Alta Frequenza per la Applicazioni di Signal Integrity. A. Ferrero- Scuola di Dottorato I.Gorini 2011
Partial Reflectometer error model
68
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 Integrity. A. Ferrero- Scuola di Dottorato I.Gorini 2011
The new formulation
69
The partial reflectometer multiport system has two states, for each i port:
STATE A STATE B
Le Misure ad Alta Frequenza per la Applicazioni di Signal Integrity. A. Ferrero- Scuola di Dottorato I.Gorini 2011
The cal equation becomes
• And the de-embedding is:
70
“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
6n -1 unknowns
Based on S parameters Always defined for any standardsCan be used to find H,L,M,K,F,G during the cal As well as to find dut S matrix during the measurement
Le Misure ad Alta Frequenza per la Applicazioni di Signal Integrity. A. Ferrero- Scuola di Dottorato I.Gorini 2011
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
71
Let’s combine everything and design
a cal to fit the DUT
Le Misure ad Alta Frequenza per la Applicazioni di Signal Integrity. A. Ferrero- Scuola di Dottorato I.Gorini 2011
Example: Design CAL for the DUT
72
P_1
P_2
P_3
P_4
Le Misure ad Alta Frequenza per la Applicazioni di Signal Integrity. A. Ferrero- Scuola di Dottorato I.Gorini 2011
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
P1 P5
P2 P6
P3 P7
P4 P8
LSM
LSM
LSM
LSM
Rec
Rec
Rec
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
• Calibration Procedure:– Thru Port 1, 5– Thru Port 2, 6– Thru Port 3, 7– Thru Port 4, 8– Recip 1, 2– Recip 3, 4– Recip 6, 7– Reflect Port 1, Reflect Port 5– Reflect Port 2, Reflect Port 6– Reflect Port 3, Reflect Port 7– Reflect Port 4, Reflect Port 8– Load Port 1, Load Port 5– Load Port 2, Load Port 6– Load Port 3, Load Port 7– Load Port 4, Load Port 8
Structure 1
Structure 2
Structures 3
Structures 4
4 separate 2-port LSM/LRM calibrations linked with reciprocal thru standards
• No wasted probe touchdowns
• Never move probe tips in x or y direction
• Full characterization of every port
• Could provide more accurate calibrations
Le Misure ad Alta Frequenza per la Applicazioni di Signal Integrity. A. Ferrero- Scuola di Dottorato I.Gorini 2011
1
2
3
4
5
6
7
8
Probe Touchdown 4
GND SIG TERM
8-Port LRM/LSM Standards (Probe tip Calibration)
Minimize probe tip Xtalk
1
2
3
4
5
6
7
8
Probe Touchdown 1
X Length
1
2
3
4
5
6
7
8
Probe Touchdown 3
X Length
1
2
3
4
5
6
7
8
Probe Touchdown 2
Le Misure ad Alta Frequenza per la Applicazioni di Signal Integrity. A. Ferrero- Scuola di Dottorato I.Gorini 2011
Socket/Board Setup Close-up
Cal StandardsOn Socket PROBESLand Places
On Board PROBESLand 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 manyissues 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
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Le Misure ad Alta Frequenza per la Applicazioni di Signal Integrity. A. Ferrero- Scuola di Dottorato I.Gorini 2011
Acknoledgements
• Valeria Teppati, Serena Bonino Politecnico of Torino
• Marco Garelli HFE
• Brett Grossmann, Tom Ruttan, Evan FledellIntel Corp
• Jon MartensAnritsu Corp
• Dave BlackhamAgilent
THANK YOU