Signal Integrity Analysis Of Mini SAS Connector

In the era of low-speed when the clock frequency is only kHz or MHz in the past,we pay the main attention to the design of the circuit function and logic, defaulting that signal can be accurately transmitted from a transmitter to a receiver. Nowadays, with the development of information technology and electronic technology, interconnection devices tend to miniaturization and high speed, and signal edge becomes steeper,causing that the effective frequency is more and more fast. Using traditional methods to design the product may lead to signal integrity problem caused by transmission line effect. Therefore, it is essential and necessary to solve the signal integrity problem for high speed interconnect system.Connector is an electronic device which connects the interconnection circuit through the spread of electrical signals. It is responsible for signal, electric energy and electromagnetic energy transmission within the system and between system and system.So it is very important for improving the transmission performance of each system to solve the signal integrity problem of the connector.This paper, combining the theory of signal integrity analysis, takes the Mini SAS external connector as the research object, and studies the influence of key structure position on the signal integrity, which is easy to cause impedance mutations in the high-speed interconnection structure of the entire connector, such as connecting fingers and pads of paddle card, the connecting structure between pin and connecting fingers,and solder joints between pads and cables, and so on. Firstly, by using threedimensional high frequency structure simulator, the connector is simulated to analysis its time-domain characteristics, such as impedance, and frequency-domain characteristics, such as S-parameters. Then, the TRL calibration method is used to calibrate the system which contains the entire connector, and a test fixture is designed exclusively for this connector. Finally, vector network analyzer is used to test the high-speed connector, and by comparing S-parameters of test with S-parameters of simulation, verify the availability and accuracy of the simulation results.Through the research of this paper, the main conclusions are as follows: 1) Sparameters of test are consistent with S-parameters of simulation. The simulation method and the simulation result are available and actual. 2) Reducing the width ofconnecting fingers and pads of paddle card can effectively increase the impedance, in order to achieve the effect of impedance matching. 3) Cutting off the remaining structure of the connection between pin and connecting fingers can increase impedance up to about 90 ohm, and can eliminate the resonance. 4) The effect of solder joints on SI is mainly reflected by the impedance mutations. Under the condition that solder joints can completely wrap the cable, solder joints size should be as small as possible in order to enhance overall transmission performance of interconnect structure.