International SpaceWire Conference 2008 Nov.5 2008

Evaluation and Analysis of Connector Performance for the Spacewire Back Plane

Koji Shibuya Keitaro Yamagishi Hideyuki Oh-hashi Seiichi Saito Masaharu Nomachi 1

Contents

1. Introduction 2. Connector Evaluation Board 3. Transmission Characteristics Evaluation 4. Crosstalk Evaluation 5. Eye-Pattern Waveform Analysis 6. Conclusion 2

1. Introduction

SpaceWire backplane system

Driver Receiver Daughter board Backplane System

Connector

Backplane 3

1. Introduction

SpaceWire backplane connectors Impedance Mismatch Crosstalk

-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.

4

2. Connector Evaluation Board

Evaluation system for a backplane connector

PCB2 (Daughter board) PCB1 (Backplane) Connector for spacewire backplane - PCB1 corresponds to a backplane.

- PCB2 corresponds to a daughter board. 5

2. Connector Evaluation Board

Measurement Setup

6

3. Transmission Characteristics Evaluation

Pin assignment for the transmission characteristics evaluation

Edge of daughter board A B C D E F G H Differential Pairs GND Pins

Side view of evaluation board

7

3. Transmission Characteristics Evaluation

Measurement Results of Return Loss and Insertion Loss

0 0 -10 -5 -20 -30 0 A B C D E F G H 2 4 6 8 10 Frequency (GHz) Differential return loss (Sdd11) -10 -15 A B C D E F G H 0 2 4 6 8 Frequency (GHz) Differential insertion loss (Sdd21) 10 -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.

8

4. Crosstalk Evaluation

Pin assignment for crosstalk evaluation

No GND pins around the victim GND pins existing around the victim Differential Pairs (Victim) GND Pins Aggressive signal pins Static signal pins a b c d e 9

0 -20 4. Crosstalk Evaluation Port 1 Port 3

Measurement Results of Crosstalk

0 Port 2 Port 4 -20 a b c d e Port 1 GND Port 3 -40 Port 2 Port 4 -40 -60 -60 -80 0 2 4 6 Frequency (GHz) 8 10 No GND pins around the victim -80 0 2 4 6 8 10 Frequency (GHz) 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.

10

Differential Transmission Lines Signal Source 5. Eye-Pattern Waveform Analysis

Waveform Simulation Model Connector model

Differential Transmission Lines

Connector model

Received signal Differential Transmission Lines  Assuming High Speed Back Plane System -

50 cm

total trace

3.125 Gbps

data rate -

2 connectors

 Pin Assignment -

E (shortest pin)

and

H (longest pin)

11

5. Eye-Pattern Waveform Analysis

Results of Analysis Pin Assignment E (Short pins) Pin Assignment H (Long pins)

- Eye-Pattern of pin assignments E is better for transmission 12

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 .

13