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Can Defected Ground Structures (DGS) reliably achieve a 3:1 bandwidth (e.g., 3–9 GHz) in a simple planar monopole, or are they more suited for narrower band applications?

I'm trying to design a compact UWB planar monopole (3–9 GHz) and have read that etching slots or patterns in the ground plane (DGS) can enhance bandwidth. Most papers show improvements of a few hundred MHz. Is it realistic to expect DGS alone to enable a full 3:1 bandwidth from a basic geometry, or is its role more about fine-tuning the match and suppressing specific harmonics within an already wideband antenna? What types of DGS patterns (U-slot, dumbbell, periodic) are most effective for broadband applications?

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By Dharnas Answered 1 year ago

In my UWB work, DGS is a powerful fine-tuning tool, not a primary bandwidth creator. A basic planar monopole (e.g., a semicircular or elliptical patch) can inherently achieve 3:1 bandwidth with a properly designed feed and ground plane cutback. The role of DGS is to improve the match in difficult bands and suppress unwanted harmonics or coupling. For instance, a U-shaped slot in the ground beneath the feed line can introduce an additional resonance to fill in a dip in the S11 curve. I use DGS as the final step after optimizing the radiator shape. For true ultra-wideband, focus first on the radiator's tapered impedance transition to free space. Then, use a parameter sweep on a simple DGS (like a rectangular slot) to smooth the impedance match across the entire band.

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