In circuit board design, microstrip and stripline are two common transmission lines used to transmit signals respectively. Although they are similar in many respects, there are significant differences in their physical structure, transmission rate, characteristic impedance, etc.
This article will introduce the basic concepts, characteristics and application scenarios of microstrip and stripline, and compare their advantages and disadvantages, so as to help designers choose the appropriate transmission line when designing PCB circuits.
Microstrip line (table bottom trace):
Microstrip line is a transmission line that separates the metal track from the ground plane. Due to its miniaturization and ease of integration, microstrip line is widely used in high-speed digital, radio frequency and microwave circuits. The main component of the microstrip line is a single-layer and double-layer metal track with a narrow width and relatively small thickness, which is usually designed to be stacked on the surface or internal layer of the PCB board.
The characteristic impedance of the microstrip line changes with the change of the wire diameter and the dielectric constant, and the change of the characteristic impedance can be realized by adjusting the width, plate thickness or dielectric constant of the microstrip line. For microstrip lines, in general, higher characteristic impedance and transmission rate can be achieved by independent layers or layered technology, which can eliminate the magnetic field interference generated between the lines, which is the microstrip line main advantages.
Stripline (inner layer routing):
Stripline is also a transmission line using metal conductors, and it is also one of the common structures in PCB circuits. The stripline structure is different from the microstrip line and consists of a wide metal path made of metal foil. Compared with microstrip, the structure of stripline board is simpler and can be realized by designing with only one layer of printed circuit board (PCB).
The characteristic impedance of the stripline changes with the change of wire diameter and dielectric constant, and the change of its characteristic impedance can be realized by adjusting the width, height or distance between the stripline and the ground plane. Due to the simple structure of the transmission line of the stripline, relatively less processing technology is required in the circuit design and production, which makes the stripline easier to produce than the microstrip line, and it is also relatively low cost.
Comparison of the advantages and disadvantages of microstrip lines and striplines:
There may be some differences between microstrip and stripline in terms of characteristic impedance, transmission rate, structure and performance. A few pros and cons of comparing microstrip and stripline are listed below:
1. Characteristic impedance: The characteristic impedance of the microstrip line varies relatively greatly, and is susceptible to electromagnetic interference between nearby lines. Therefore, some special technologies are required to overcome these problems. The characteristic impedance of the stripline has small changes and strong anti-interference ability, so it is often used in the design of high-density circuit boards.
2. Transmission rate: Under the same conditions, microstrip lines can usually achieve higher transmission rates. Because the structure of the microstrip line can reduce the signal-to-noise ratio and cross-interference, it is especially important for high-speed digital and high-frequency radio frequency circuits. The transmission rate of the stripline is lower than that of the microstrip line.
3. Structure: The structure of the microstrip line is relatively complicated. Since the transmission line structure of the microstrip line is layered, it requires designers to spend more energy on design and manufacture. In contrast, the structure of the stripline is simple, easy to handle and produce, and also saves some cost and process problems.
4. Performance: Microstrip line has good anti-electromagnetic interference ability, high characteristic impedance and better transmission rate, and is suitable for high-speed digital and high-frequency radio frequency circuits. Stripline has a small characteristic impedance change, is easy to handle and produce, and is more suitable for low-speed digital and analog circuits.
It should be noted that when selecting a transmission line, it should be selected according to the design and application needs. In addition to microstrip and stripline, you can also choose transmission lines, such as coaxial cables, parallel lines, etc. For general circuit board design, microstrip and stripline are one of the most commonly used and reliable solutions, and designers must weigh their advantages and disadvantages and choose them according to actual needs.
From this we can conclude that microstrip and stripline are two commonly used PCB transmission lines . Although they have great differences in structure, characteristic impedance, transmission rate, anti-interference ability and manufacturing cost, they are both Each has its own advantages and application scenarios. When selecting PCB transmission lines, microstrip lines or striplines should be selected according to the requirements and special needs of the actual application environment, so as to achieve better results for the high-speed, high-quality and high-reliability transmission of the circuit.
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