Getting faster bandwidth HervéGrabas Getting faster bandwidth - Hervé Grabas1
Present bandwith status Limiting factors: Cables Board Bonding wires Input line Sampling capacitance and switch Getting faster bandwidth - Hervé Grabas2
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
Board status Getting faster bandwidth - Hervé Grabas4 On board measurment with 3Ghz network analyser 2Ghz bandwidth measured with network analyzer
Board + Chip status Getting faster bandwidth - Hervé Grabas5 500Mhz bandwidth measured with network analyzer On board measurment with 3Ghz network analyser
Board bandwith limitation Getting faster bandwidth - Hervé Grabas6 Within the actual Psec3 tester board: 1.The signal goes through the 50Ohms to the chip 2.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!
Board bandwidth fix Getting faster bandwidth - Hervé Grabas7 Future Psec3 tester board: 1.The signal goes through the 50Ohms to the chip 2.The DAC is RF shielded by an inductance 3.The signal returns via the per-channel dedicated return line (no ground)
Chip on board bandwidth issue Getting faster bandwidth - Hervé Grabas8 Psec3 tester board with chip: 1.The signal goes through the 50Ohms to the chip 2.Due to parasitic capacitive ground coupling in the chip the RF signals illuminate the whole chip 3.The signal returns via the less inductive ground pads to the connector.
Chip on board fix Getting faster bandwidth - Hervé Grabas9 Psec3 tester board with chip fixed: 1.The signal goes through the 50Ohms to the chip 2.Losses are minimized by having a single specific return path
Package bandwidth & fix Getting faster bandwidth - Hervé Grabas10 With and without bonding wires
Other bandwidth/losses issues? Getting faster bandwidth - Hervé Grabas11 Line dimension:.8µm×3072µm Line resistance: 146 ohms Line dimension:.8µm×3072µm Line resistance: 146 ohms Input line Return line
Where are we limited in bandwidth summary FactorsDescriptionQuantizationFix The measurement in itself (cables) Total cable size<30Small cables, loss substraction and calibration The boardReturn path grounded 2GhzDedicated return path The bonding wires of package Bandpass filterCutoff freq ~ 1GhzFlip chip The input line of the chip Parasitic capacitance and resistance C ~ 1.5pF R~ 150Ohms Higher metal level Getting faster bandwidth - Hervé Grabas12