HervéGrabas Getting faster bandwidth Hervé Grabas 1 Present bandwith status Limiting factors Cables Board Bonding wires Input line Sampling capacitance and switch Getting faster bandwidth Hervé Grabas ID: 590488
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Slide1
Getting faster bandwidth
HervéGrabas
Getting faster bandwidth - Hervé Grabas
1Slide2
Present bandwith status
Limiting factors:CablesBoardBonding wiresInput line
Sampling capacitance and switch
Getting faster bandwidth - Hervé Grabas
2Slide3
Cable status
Getting faster bandwidth - Hervé Grabas
3
Safe to use cables under 30cm of length
Plot of the 3dB cutoff frequency of cable function of length Slide4
Board status
Getting faster bandwidth - Hervé Grabas
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On board
measurment
with 3Ghz network
analyser
2Ghz bandwidth measured with network analyzerSlide5
Board + Chip status
Getting faster bandwidth - Hervé Grabas
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500Mhz bandwidth measured with network analyzer
On board
measurment
with 3Ghz network
analyserSlide6
Board bandwith limitationGetting faster bandwidth - Hervé Grabas
6
Within the actual Psec3 tester board:
The signal goes through the 50Ohms to the chip
The signal returns via
gnd
on the board through all decoupling cap of all channels and the DAC.
The signal returns through the line to the connector
!
Decoupling cap shown here are on the board!Slide7
Board bandwidth fix
Getting faster bandwidth - Hervé Grabas
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Future Psec3 tester board:
The signal goes through the 50Ohms to the chip
The DAC is RF shielded by an inductance
The signal returns via the per-channel dedicated return line (no ground)Slide8
Chip on board bandwidth issueGetting faster bandwidth - Hervé Grabas
8
Psec3
tester
board with chip:
The signal goes through the 50Ohms to the chip
Due to parasitic capacitive ground coupling in the chip the RF signals illuminate the whole chip
The signal returns via the
less inductive ground pads to the connector.Slide9
Chip on board fix
Getting faster bandwidth - Hervé Grabas
9
Psec3
tester
board with chip fixed:
The signal goes through the 50Ohms to the
chip
Losses are minimized by having a single specific return pathSlide10
Package bandwidth & fixGetting faster bandwidth - Hervé Grabas
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With and without bonding wiresSlide11
Other bandwidth/losses issues?
Getting faster bandwidth - Hervé Grabas
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Line dimension: .8µm×3072µm
Line resistance: 146 ohms
Input line
Return lineSlide12
Where are we limited in bandwidthsummary
Factors
DescriptionQuantization
FixThe measurement in itself (cables)
Total cable size<30Small cables, loss substraction and calibrationThe boardReturn
path grounded
2Ghz
Dedicated return path
The bonding wires of package
Bandpass
filter
Cutoff
freq
~
1Ghz
Flip
chip
The input line of the chip
Parasitic
capacitance and resistance
C ~ 1.5pF
R~ 150Ohms
Higher metal level
Getting faster bandwidth - Hervé Grabas
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