Evaluation and Analysis of Connector Performance for the Spacewire Back Plane

SpaceWire interconnection using a backplane which makes a system compact has been investigated. In the backplane interconnection system, high-speed signals are connected between daughter boards via connectors and a backplane. The connectors used to interface the daughter boards and the backplane are key components because the impedance mismatching and the transmission loss in the connector might cause serious waveform distortions of high-speeds signal. In this paper, connectors for the backplane, which have been selected by the space qualified design and compactness, are modelled for various cases of signal and ground pin assignment by the measurement of S-parameters. And, then, the evaluation and the analysis are carried out by the SPICE simulation of the signal transmission between daughter boards via the connectors on the backplane. It was found that the crosstalk is generated at the connector and the characteristic impedance of the connector changes according to the pin assignment. Further, it was confirmed that the investigated connector can be used in backplane systems up to 3Gbps when the pin assignment is designed suitable. 1 CONNECTOR EVALUATION BOARD For on-board equipment, higher-speed signal interconnections are required due to increasing data rates between the boards in the equipment. High-speed SpaceWire interconnection using a backplane which makes a system compact and highperformance has been investigated. The connectors on the backplane are key components because the impedance mismatching and the transmission loss of the connector might cause serious waveform distortions of high-speed signals. Because no high speed backplane connector with space qualified design was found, a backplane connector without guarantee of high frequency performance was selected from the point of view of space use and compactness for SpaceWire backplane interconnection. In order to evaluate the connector, a pair of printed circuit boards (PCBs) has been developed, one PCB corresponds to a backplane and another PCB corresponds to a daughter board. The backplane connector has four row of conducting pins, and consists of a right angle plug and a receptacle. The plug is mounted on the daughter board and the receptacle is mounted on the backboard, respectively. The signal pins of backplane connector are connected to the SMA connectors on the PCB edges through micro-strip lines on PCBs. Fig.1 shows a photograph of the PCBs for evaluation of the backplane connector. Fig.1: PCBs for Evaluation of a backplane connector The pin assignment of the connector can cause the changes of the transmission characteristics and the crosstalk. Eight differential mode signal paths with different pin assignment of signal and ground are arranged within the backplane connector. Fig.2 shows the variations of the pin assignment. Fig.3 shows another differential mode signal path within the same connector surrounded by five single pin signal paths. The arrangement of Fig.3 is used for the evaluation of crosstalk (the differential path is a victim and single pin of a, b, c, d, and e are aggressive). Edge of daughter board