- 2071 Magh · 5 marks
Short note: Strip-lines against micro-strips
Short answer
Stripline has a central strip between two ground planes, giving pure TEM propagation, no dispersion or radiation, but harder fabrication. Microstrip has a strip on a substrate over one ground, giving quasi-TEM behavior with dispersion and radiation, but easy fabrication and surface mounting. Microstrip is common for MMICs and antennas; stripline suits filters, couplers and high-isolation circuits.
Write a short note on microwave strip-lines against micro-strips.
Stripline and microstrip are planar transmission lines made by etching copper strips on dielectric substrates. They are used in microwave integrated circuits.
Stripline (triplate) Microstrip
==================== ground
| dielectric εr | ____ strip (w)
| ▬▬▬ strip | | dielectric εr | h
| | ================= ground
==================== ground
| Feature | Stripline | Microstrip |
|---|---|---|
| Structure | Strip between two grounds, fully inside the dielectric | Strip on top of the substrate, one ground below |
| Mode | Pure TEM | Quasi-TEM (fields partly in air) |
| Effective εr | εeff = εr | 1 < εeff < εr |
| Dispersion | None | Present at high frequency |
| Radiation | None (shielded) | Some radiation from open top |
| Losses | Lower radiation loss | Higher (radiation, surface waves) |
| Fabrication | Harder (multilayer, buried) | Easy, single-layer PCB |
| Mounting components | Difficult (buried strip) | Easy (surface mount, tuning) |
| Bandwidth | Very wide | Wide |
| Uses | Couplers, filters, power dividers | MMICs, patch antennas, amplifiers |
Choice: microstrip is the most popular because it is cheap and components are easy to mount. Stripline is chosen where isolation, low radiation and no dispersion are needed, for example in high-performance couplers and filters.
✓ Answer checked by Claude Opus 5.5 (high effort)
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