What is a Dielectric Resonator Antenna?
By: Peter McNeil
Dielectric Resonator Antennas (DRAs) are antennas formed from resonant dielectric radiators fed by a conductor carrying an RF signal. In this way, DRAs convert unguided waves transmitted by conductors to guided waves that are then emitted from the dielectric structure. As DRAs transmit through a dielectric there are no conductor losses and the potential for very high radiation efficiency when properly designed and manufactured.
DRAs can potentially be made smaller than comparable monopoles, dipoles, and patch antennas for millimeter-wave applications, as the size of a DRA is proportional to the free space wavelength of the resonant frequency divided by the square root of the effective relative permittivity (dielectric constant) of the dielectric material used. This is potentially advantageous for designs requiring extremely compact dimensions, as typical metallic antennas are proportional to the free space wavelength, and DRAs may be implemented at a fraction of the size.
If a low-loss dielectric is used, the radiation efficiency of a DRA may be much higher in the millimeter-wave spectrum than traditional metallic antennas as conduction losses increase with frequency. DRAs also offer a wide range of design freedom associated with the impedance bandwidth, dimensions, and material choice. DRAs may also be implemented with a variety of excitors, which can be chosen to optimize a design for given requirements. Moreover, the DRA gain, bandwidth, and polarization can all be controlled as design variables using various design techniques.
DRAs can be virtually any shape that is designed to resonate at the desired frequency, with each shape exhibiting tradeoffs of various performance factors and design/manufacturing complexity. DRAs may also be designed as an array for gain enhancement, a beamforming style antenna, or may even include active elements to enable beamsteering. An additional dielectric lens may be used in conjunction with a DRA to further enhance the gain/directivity or antenna pattern characteristics.
DRAs have traditionally been fabricated using machined ceramic materials with high dielectric constants and relatively low loss tangents. More recently, DRAs have been fabricated using polymer materials with much lower dielectric constants but are more readily fabricated into complex shapes to achieve various performance characteristics, such as supershaped DRAs and fractal DRAs with high impedance bandwidths. DRAs may also be developed using PCB or ceramic technologies, such as low temperature co-fired ceramic (LTCC) structures. Moreover, there have even been efforts to integrate DRAs on semiconductor die, but limitations and size constraints for on-chip DRAs tend to result in lower impedance bandwidths and gain. However, on-chip DRAs can also be made to operate at much higher frequencies, from tens to hundreds of gigahertz.
It is possible that DRAs may enable future millimeter-wave communication and radar technologies, such as millimeter-wave 5G and automotive radar.
Courtesy of everything RF