Microstrip line variants
This article describes microstrip line variants viz. inverted microstrip line, suspended microstrip line, shielded microstrip line. Advantages and disadvantages of microstrip line are mentioned below.
Microstrip is most popular structure used for RF design and product development due to easy in fabrication and complete
exposure for troubleshooting. High dielectric substrate will have very less RF circuit
size which helps concentrate energy between trace and ground.
Following are important microstrip variants used.
• inverted microstrip line
• suspended microstrip line
• shielded microstrip line
As shown in the fig-1, the ground plane and microstrip lie on the same one side. They both are separated by air dielectric. The height(h) is the combination of both substrate thickness as well as air dielectric.
This microstrip line variant is reciprocal to inverted microstrip line. In suspended microstrip line, microstrip trace and ground plane lie opposite to each other. The Air gap exists between substrate and the ground plane.
The shielded microstrip line variant is similar to basic microsrip line except the enclosure. The metallic enclosure will cover the entire structure and hence reduce the EMI(Electromagnetic Interference) due to shielding. This is the most realistic configuration as all the RF circuits are protected from environment and nearby RF circuits/systems.
Advantages of microstrip line
• Smaller size
• Easy to fabricate
• Easy to troubleshoot
Disadvantages of microstrip line
• Unwanted radiation in uncovered microstrip based configuration
• Higher loss
• Poor isolation among adjacent lines
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