Microstrip line

     Microstrip line is a microwave transmission line composed of a single conductor band supported on a dielectric substrate. Planar structure transmission line suitable for making microwave integrated circuit. Compared with metal waveguide, it has the advantages of small volume, light weight, wide frequency band, high reliability and low manufacturing cost; However, the loss is slightly larger and the power capacity is small. In the early 1960s, due to the development of microwave low loss dielectric materials and microwave semiconductor devices, microwave integrated circuits were formed, which made microstrip lines widely used, and various types of microstrip lines appeared one after another. It is generally manufactured by thin film process. The dielectric substrate is made of materials with high dielectric constant and low microwave loss. The conductor shall have the characteristics of high conductivity, good stability and strong adhesion to the substrate. "

     The general transmission line is composed of two or more conductors to transmit transverse electromagnetic wave (TEM wave). The common transmission lines include double line, coaxial line, stripline and microstrip line. Among them, microstrip line is one of the most widely used planar transmission lines. Microstrip line can be fabricated by lithography and is easy to integrate with other passive and active devices, so it is widely used in printed circuit board.

     In precision circuit design, it is easy to ignore the electrical characteristics of printed circuit board itself, which may be harmful to the function of the whole circuit. If the electrical characteristics are properly designed, it will have the advantages of reducing interference and improving anti-interference. In high-speed circuits, printed traces should be treated as transmission lines. The commonly used transmission lines of printed circuit board are microstrip line and stripline. Microstrip line is a transmission line that uses dielectric to separate the conductor from the ground. The thickness and width of the printed trace, the thickness of the dielectric between the trace and the ground, and the dielectric constant of the dielectric determine the characteristic reactance of the microstrip line.