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A compact planar ultra-wideband (UWB) antenna with continuously tunable, independent band-notches for cognitive radio applications is presented. The antenna is fabricated using a copper cladded substrate. A radiating patch with an inverted rectangular T-slot is etched on the top side of the substrate. A straight rectangular strip with a complete gap is embedded into the T-slot. By placing a single varactor diode across this gap, a frequency-agile band-notch function below 5 GHz is realized. On the bottom side of substrate, a U-shaped parasitic element having an interdigitated-structure is placed beneath the radiating patch. The second narrow band-notch is created by inserting a second varactor diode into the gap on one leg of the parasitic element. It has a frequency agile performance above 5 GHz. The presence of the interdigitated structure suppresses higher-order resonant modes and enhances the tunability of the notched bandwidth. Because these antenna structures naturally block DC, a very small number of lumped elements are required. The experimental results, which are in good agreement with their simulated values, demonstrate that both band-notches can be independently controlled and the entire frequency-agile fractional bandwidth is as high as 74.5 %, demonstrating a very wide notched frequency-agile coverage. Index Terms-Band-notch filters, frequency agile, frequency tunable, planar antennas, UWB antennas I. INTRODUCTION ltra-wideband (UWB) technology has been widely applied in wireless sensor networks, biomedical and healthcare wireless systems, and some other in-house devices in radar detecting, locating, and communications [1]. These applications benefit from the unique features of low-power spectral density and consumption associated with UWB

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