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