People's living standards have been continuously improving, and the economic level has improved, so that more people have the money to buy cars. When you buy a car, have you thought about the connectors used in these car parts? Connector products used in automobiles are mostly high-speed connectors. When developing a high-frequency vehicle connection system, the design issues of accuracy, mechanical strength and overall applicability when used in harsh environments are the primary consideration. If you want to achieve interference-free data communication of symmetrical high-frequency electrical signals through cables and interfaces, the following five characteristics are very important.
1. Constant impedance on the transmission line;
2. The dielectric loss of insulating materials is small;
3. The connector adopts a good low-resistance terminal connection;
4. Paired signal conductors are regularly stranded;
5. The shielding part is covered repeatedly.
In the car, the signal is transmitted to the relevant USB control unit, such as the "main unit", through a shielded USB cable. This connection is tested to various automotive application specifications. In the case of complete shielding, this connector can also meet the USB high-speed transmission standard of 480MBit/s. This ensures stable impedance from the USB interface to the control unit and good electromagnetic compatibility.
Electromagnetic compatibility is also critical to the quality of connector technology. To demonstrate this performance, the USB interface in operation has been tested according to the corresponding electromagnetic compatibility standards. Considering the data transmission rate, the corresponding USB high-speed data transmission system should be developed according to the high-frequency parameters. According to the SAE/USCAR-30 draft/08-2006 specification, some of the main high-frequency parameters described in the USB2.0 revision are as follows:
1. Impedance range (90±15%);
2. Propagation delay (<26ns);
3. Propagation delay difference (<100ps);
4. Attenuation rate (<5.8dB, f=400MHz);
5. Shielding range (lower limit 20dB, 30MHz~1GHz).
Impedance discontinuities in the propagation path will cause reflection losses and signal distortion. With the help of time domain reflectometry (TDR), the impedance value can be displayed directly as a function of time, so that the value can be monitored at all times for compliance with the specified system tolerances of the USB system. In addition to these parameters, the attenuation rate is also one of the nominal values ​​that has an important impact, interconnect attenuation will cause signal distortion and affect the power design of the system.
An electronic data link must accomplish two main tasks: one is data transmission, and the other is not affecting the surrounding environment. Therefore, care must be taken to ensure a very low inductive interconnection between wire and connector shields and between connector and connector shields. The shielding effectiveness parameter provides an indication of the shielding quality of passive components such as connectors, cables and connector assemblies. Shielding effectiveness provides a range of parameters over which EMI can be eliminated. The reduction of the absolute emission value and the increase of the interference immunity depend not only on the design of the connector, but also on the connection concept between the shields.