Dielectric resonator antenna

Lore & Background

The dielectric resonator antenna was first proposed by Robert Richtmyer in 1939. The first design and test of a DRA was carried out by Long et al. in 1982, using a leaky waveguide model and assuming a magnetic conductor model of the dielectric surface. In that initial investigation, Long et al. explored the HEM11d mode in a cylindrical ceramic block to radiate broadside. Three decades later, in 2012, Guha introduced another mode, HEM12d, which also produces an identical broadside pattern.

The antenna's operation has been described as resembling the antenna conceived by Marconi, with the difference that the inductive element is replaced by the dielectric material. The configuration offers a framework where the geometric symmetry of the electric field in free space is explicitly broken by a floating inductor-capacitor system with one end excited by a time-varying voltage source. The dimension of a DRA is on the order of λ₀/√εᵣ, allowing significant size reduction through high dielectric constants (εᵣ ≈ 10–100).

DRAs offer simple coupling schemes to nearly all transmission lines used at microwave and millimeter-wave frequencies, facilitating integration into planar technologies. The operating bandwidth can be varied over a wide range by choosing resonator parameters; for lower order modes, bandwidth can range from a fraction of a percent to about 20% or more. Multiple modes radiating identically have been successfully employed, such as a hybrid combination of a dielectric ring-resonator and an electric monopole, and multiple identical monopole-type modes in an annular shaped dielectric ring-resonator have been theoretically analyzed for use in ultra-wideband antennas.

Reader's Guide

The dielectric resonator antenna holds significance as a highly efficient alternative to metal antennas at high microwave and millimeter-wave frequencies, where conductor losses become problematic. Its lack of metal parts eliminates inherent conductor loss, leading to high radiation efficiency, a feature especially attractive for millimeter-wave antennas. The ability to reduce antenna size by choosing a high dielectric constant material (εᵣ ≈ 10–100) makes DRAs suitable for compact portable wireless devices and military millimeter-wave radar equipment.

The antenna's legacy includes its simple coupling to various transmission lines, allowing easy integration into planar technologies and straightforward experimental optimization. The bandwidth can be tailored over a wide range—from a fraction of a percent to over 20%—by selecting the dielectric constant and shaping the resonator. The use of multiple modes with identical radiation patterns, such as the HEM11d and HEM12d modes, and composite geometries like the dielectric ring-resonator with an electric monopole, has enabled wider bandwidth and ultra-wideband antenna designs. These features have established the DRA as a versatile and practical antenna type for modern high-frequency applications.

Did You Know?

• Long et al. performed the first design and test of a DRA in 1982, exploring the HEM11d mode in a cylindrical ceramic block.
• The size of a DRA is on the order of λ₀/√εᵣ, allowing significant miniaturization with high dielectric constants (εᵣ ≈ 10–100).
• The operating bandwidth of lower order DRA modes can be varied from a fraction of a percent to about 20% or more.