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 Abstract-A technique of dielectric perturbation in a dielectric resonator antenna (DRA) has been explored with specific application to filter out higher resonating modes causing unwanted radiations. This is especially conceived and conjectured for microstrip-fed cylindrical DRA (CDRA). Creating a protruded cavity in it filled with dielectric material of varying r is the primary mechanism. Effect of such perturbation has been experimentally demonstrated establishing air (r=1) as the simplest and most promising one for a specific application in weakening HEM21δ mode in it, recently identified as the source of cross-polar (XP) radiations. Physical insight into this new technique is also clarified. As much as 10 dB reduction in the principal plane XP values without affecting the primary radiations has been documented.