An implantable antenna for the applications of biomedical telemetry has been widely studied in the modern medical science. The purpose of this study is to design and fabricate an implantable antenna which exhibits enhanced bandwidth (25%) and miniaturization for the use of implantation. In this letter, the microwave dielectric ceramic (MgTa1.5Nb0.5O6) substrate which possesses high dielectric constant (εr = 28) and high quality factor is used as the substrate of the implantable antenna, a CPW-fed monopole dual spiral structure is adopted as the antenna pattern and fabricated by the print-screening technique. The effects of shape, length, size, and thicknesses of the proposed antenna would be evaluated and investigated in this letter. In addition, the center frequency is required to conform to the band (402 ~ 405 MHz) provided by Medical Implant Communication Services (MICS). From the experimental results of the proposed antenna immersed in phantom fluid, the optimum antenna exhibits a miniaturized volume of 288 mm3, bandwidth of 134 MHz (33%), return loss 16.32 db at 404 MHz, the SAR of 142 W/Kg, and gain of 16 db, respectively.