Microstrip Line Variants: Inverted, Suspended, and Shielded

This article discusses various microstrip line variants, including the inverted microstrip line, suspended microstrip line, and shielded microstrip line.

The advantages and disadvantages of microstrip lines are also mentioned. Microstrip is a very popular structure for RF design and product development due to its ease of fabrication and accessibility for troubleshooting. Using a high dielectric substrate results in a smaller RF circuit size, which helps concentrate energy between the trace and ground plane.

The following are important microstrip variants:

• Inverted microstrip line
• Suspended microstrip line
• Shielded microstrip line

Inverted Microstrip Line

As shown in the figure, the ground plane and microstrip lie on the same side, separated by air. The height (h) represents the combined thickness of the substrate and the air dielectric.

Suspended Microstrip Line

This microstrip line variant is, in a sense, the opposite of the inverted microstrip line. In a suspended microstrip line, the microstrip trace and ground plane are positioned opposite each other, with an air gap existing between the substrate and the ground plane.

Shielded Microstrip Line

The shielded microstrip line variant is similar to a basic microstrip line but includes an enclosure. The metallic enclosure covers the entire structure, reducing EMI (Electromagnetic Interference) due to shielding. This is a realistic configuration because RF circuits are often protected from the environment and nearby RF circuits/systems by being enclosed.

Advantages of Microstrip Line

• Smaller size
• Easy to fabricate
• Easy to troubleshoot

Disadvantages of Microstrip Line

• Unwanted radiation in uncovered microstrip-based configurations
• Higher loss
• Poor isolation among adjacent lines