In this paper, we present a waveguide-fed hollow cylindrical dielectric resonator antenna (CDRA) with dual-band operation and its modified structure for wider bandwidth and enhanced gain operation. The distinctive nature of the structure provides two bands having resonant frequencies at 8.46 GHz and 9.24 GHz with maximum gains of 5.37 dBi and 6.86 dBi respectively with a single dielectric resonator antenna (DRA). The dual-band is achieved due to the resonance of DRA and the air column inside it. Excellent coupling is achieved in both bands. The dual-band structure is modified by changing the volume of the air column inside the CDRA keeping all other parameters constant to result in a wider band and high gain antenna. A bandwidth of 7.9% with a resonant frequency of 9.0 GHz and a maximum gain of 8.14 dBi is obtained for the modified structure.