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Cable status Getting faster bandwidth - Hervé Grabas3 Safe to use cables under 30cm of length Plot of the 3dB cutoff frequency of cable function of length
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Getting faster bandwidth - Hervé Grabas 1
Getting faster bandwidth
HervéGrabas
Getting faster bandwidth - Hervé Grabas 2
Present bandwith status
Limiting factors:CablesBoardBonding wiresInput lineSampling capacitance and switch
Getting faster bandwidth - Hervé Grabas 3
Cable status
Safe to use cables under 30cm of length
Plot of the 3dB cutoff frequency of cable function of length
Getting faster bandwidth - Hervé Grabas 4
Board statusOn board measurment with 3Ghz network analyser
2Ghz bandwidth measured with network analyzer
Getting faster bandwidth - Hervé Grabas 5
Board + Chip status
500Mhz bandwidth measured with network analyzer
On board measurment with 3Ghz network analyser
Getting faster bandwidth - Hervé Grabas 6
Board bandwith limitation
Within the actual Psec3 tester board:1. The signal goes through the 50Ohms to the chip2. The signal returns via gnd on the board through all decoupling cap of all channels
and the DAC.3. The signal returns through the line to the connector
!Decoupling cap shown here are on the board!
Getting faster bandwidth - Hervé Grabas 7
Board bandwidth fix
Future Psec3 tester board:1. The signal goes through the 50Ohms to the chip2. The DAC is RF shielded by an inductance3. The signal returns via the per-channel dedicated return line (no ground)
Getting faster bandwidth - Hervé Grabas 8
Chip on board bandwidth issue
Psec3 tester board with chip:1. The signal goes through the 50Ohms to the chip2. Due to parasitic capacitive ground coupling in the chip the RF signals illuminate the
whole chip3. The signal returns via the less inductive ground pads to the connector.
Getting faster bandwidth - Hervé Grabas 9
Chip on board fix
Psec3 tester board with chip fixed:1. The signal goes through the 50Ohms to the chip2. Losses are minimized by having a single specific return path
Getting faster bandwidth - Hervé Grabas 10
Package bandwidth & fixWith and without bonding wires
Getting faster bandwidth - Hervé Grabas 11
Other bandwidth/losses issues?
Line dimension: .8µm×3072µmLine resistance: 146 ohms
Input line
Return line
Getting faster bandwidth - Hervé Grabas 12
Where are we limited in bandwidthsummary
Factors Description Quantization Fix
The measurement in itself (cables)
Total cable size <30 Small cables, loss substraction and calibration
The board Return 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 ~ 1.5pFR~ 150Ohms
Higher metal level