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1
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
2
1. Introduction2. Connector Evaluation Board3. Transmission Characteristics Evaluation4. Crosstalk Evaluation5. Eye-Pattern Waveform Analysis6. Conclusion
Contents
3
1. Introduction
Backplane System Backplane
Daughter board
Receiver
Connector
Driver
SpaceWire backplane system
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.
ImpedanceMismatch
Crosstalk
SpaceWire backplane connectors
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.
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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.
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