Best layout and performance are achieved with at least a 4-layer multilayer board, where there is a ground plane layer, a power supply layer, and two signal layers.

电路板至少需要4层才能实现最佳布局和性能：一个接地层、一个电源层和两个信号层。

youdao

The two bottom layers, called the physical layer protocols, take care of the actual signal transfer over the network cable.

称为 物理层协议的两个底层处理网络电缆上的实际信号传输。

youdao

An intricate set of metal layers focuses and manipulates incoming radio waves, allowing the tag to send back a clear signal.

这套装置以一系列精巧的金属片来聚焦和操控入射的无限电波，使标签将清晰的信号反射回来。

youdao

Chief technical officer Nigel Gilhespy says the fabric is made of five layers of fabric, three of which are conductive, which means they create an electrical signal and perform a high-tech function.

CNN: From chemistry to catwalk

This image sensor layers the pixel section containing formations of back-illuminated structure pixels onto chips containing the circuit section for signal processing, which is in place of supporting substrates for conventional back-illuminated CMOS image sensors.

ENGADGET: Sony's new cameraphone CMOS jams bigger gear into the same space (video)