1. 1 Evaluation and Analysis of Connector Performance for the Spacewire Back Plane Koji Shibuya Keitaro Yamagishi Hideyuki Oh-hashi Seiichi Saito Masaharu Nomachi International SpaceWire Conference 2008 Nov.5 2008

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

3. 3 1. Introduction Backplane System Backplane Daughter board Receiver Connector Driver SpaceWire backplane system

4. 4 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. Impedance Mismatch Crosstalk SpaceWire backplane connectors

5. 5 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.

6. 6 2. Connector Evaluation Board Measurement Setup

7. 7 3. Transmission Characteristics Evaluation A B C D E F G H Differential Pairs GND Pins Pin assignment for the transmission characteristics evaluation Edge of daughter board Side view of evaluation board

8. 8 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. 3. Transmission Characteristics Evaluation

9. 9 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

10. 10 Measurement Results of Crosstalk No GND pins around the victimGND 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

11. 11 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 Differential Transmission Lines Signal Source Received signal  Pin Assignment - E (shortest pin) and H (longest pin) Connector model Connector model Differential Transmission Lines Differential Transmission Lines

12. 12 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

13. 13 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.