What is Stripline in microwave: Advantages and Disadvantages

A stripline is a planar microwave transmission line in which a conductive strip is embedded between two parallel ground planes within a dielectric material. Its advantages include excellent electromagnetic shielding and controlled impedance, whereas its disadvantages include fabrication complexity, higher dielectric losses, and difficult component accessibility.

Microwave Stripline Structure and field pattern

Stripline is a type of planar transmission line used in microwave applications. It’s created by etching a center conductor on a substrate. Essentially, it’s a structure where a center metal strip is sandwiched between two ground planes, one on top and the other on the bottom.

Figure 1: Normal stripline circuit with center metal strip sandwiched between two ground planes.

Here are some common types of striplines:

• Normal stripline
• Double conductor stripline
• Offset stripline
• Suspended stripline

Benefits or Advantages of Stripline

1. Good Electro-magnetic Shielding: The center metal structure provides excellent electromagnetic shielding.
2. Lower Attenuation Loss: Stripline generally exhibits lower attenuation loss compared to other transmission line technologies.
3. Better Isolation: It offers better isolation between circuits.
4. Wide Bandwidth: Stripline is capable of operating over a wide bandwidth.

Drawbacks or Disadvantages of Stripline

1. Complex and Expensive Fabrication: The structure is complex, making fabrication difficult and often more expensive.
2. Smaller Trace Width: The width of the stripline trace is smaller compared to a microstrip line with the same impedance (Z) and height (H). This can lead to the trace detaching from the dielectric substrate if not handled carefully.
3. Difficult Tuning and Troubleshooting: Because the entire structure is enclosed, tuning and troubleshooting can be challenging.

Summary

Stripline technology provides predictable signal transmission for RF and microwave circuits requiring controlled impedance and minimal electromagnetic radiation. Its transmission advantages support high-frequency communication and radar applications, although multilayer fabrication complexity and manufacturing cost should be considered.