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Evaluation and Analysis of Connector Performancefor the Spacewire Back Plane

Koji Shibuya Keitaro Yamagishi Hideyuki Oh-hashi Seiichi Saito Masaharu Nomachi

International SpaceWire Conference 2008 Nov.5 2008

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1. Introduction2. Connector Evaluation Board3. Transmission Characteristics Evaluation4. Crosstalk Evaluation5. Eye-Pattern Waveform Analysis6. Conclusion

Contents

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1. Introduction

Backplane System Backplane

Daughter board

Receiver

Connector

Driver

SpaceWire backplane system

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1. Introduction

-Connectors which have been selected by the space qualified are NOT designed　 for high-speed Signal Transmission purpose. impedance mismatching and crosstalk are generated

Evaluation and Analysis of Connector Performance is important.

ImpedanceMismatch

Crosstalk

SpaceWire backplane connectors

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2. Connector Evaluation Board

PCB2 (Daughter board)

Evaluation system for a backplane connector

PCB1(Backplane)

Connector for spacewire backplane

- PCB1 corresponds to a backplane.- PCB2 corresponds to a daughter board.

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2. Connector Evaluation Board

Measurement Setup

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3. Transmission Characteristics Evaluation

A B C D

E F G H

Differential Pairs

GND Pins

Pin assignment for the transmission characteristics evaluation

Edge ofdaughter board

D / HC / GB / FA / E

Backplane

Daughter board

Connector

D / HC / GB / FA / E

Backplane

Daughter board

Connector

Side view of evaluation board

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Measurement Results of Return Loss and Insertion Loss

Differential return loss (Sdd11) Differential insertion loss (Sdd21)

-Differences between different pin assignments become remarkable in frequency range higher than 1GHz.

- The pin assignments using the long pins for signals cause characteristic degradation.

0 2 4 6 8 10

-15

-10

-5

0

Frequency (GHz)

Sdd

21 (

dB)

ABCDEFGH

0 2 4 6 8 10

-30

-20

-10

0

Frequency (GHz)

Sdd

11 (

dB)

ABCDEFGH

3. Transmission Characteristics Evaluation

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4. Crosstalk Evaluation

Differential Pairs (Victim)

Aggressive signal pins

GND Pins

Pin assignment for crosstalk evaluation

Static signal pins

No GND pins around the victim

GND pins existing around the victim

a b c

d e

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Measurement Results of Crosstalk

0 2 4 6 8 10

-80

-60

-40

-20

0

Frequency (GHz)

Sds1

3 (d

B)

0 2 4 6 8 10

-80

-60

-40

-20

0

Frequency (GHz)

Sds1

3 (d

B)

abcde

Port 1 Port 2

Port 3 Port 4

GND

Port 1 Port 2

Port 3 Port 4

No GND pins around the victim GND pins existing around the victim

The pin assignment of the GND pins around the differential pair is effective to reduce the crosstalk from the other signal.( 15dB or more )

Crosstalk can be dramatically reduced by ground pins around victim.

4. Crosstalk Evaluation

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5. Eye-Pattern Waveform Analysis

Waveform Simulation Model

Assuming High Speed Back Plane System- 50 cm total trace- 3.125 Gbps data rate - 2 connectors

DifferentialTransmission

Lines

SignalSource

Received signal

Pin Assignment- E (shortest pin) and H (longest pin)

Connectormodel

Connectormodel

DifferentialTransmission

Lines

DifferentialTransmission

Lines

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5. Eye-Pattern Waveform Analysis

Pin Assignment E(Short pins)

Pin Assignment H(Long pins)

Results of Analysis

- Eye-Pattern of pin assignments E is better for transmission

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6. Conclusion

1. The pin assignments using the long pins for signals cause characteristic degradation.

2. The pin assignment of the GND pins around the differential pair is effective to reduce the crosstalk from the other signals.

3. The eye-pattern waveforms were shown by the simulation. the 3Gbps backplane transmission is possible using the connector selected by the space qualified design.

The connector selected by the space qualified design can use for the system of over Gbps high speed signal transmission via the backplane by suitable pin assignment design.