Design of Sleeve Dipole Antenna for Suppressing Leakage Current on a Coaxial Cable

A small sleeve dipole antenna (SDA) for a suppressing leakage current on a coaxial cable is presented in this letter. The upper radiating element of the proposed antenna is modified into a helical shape to reduce the antenna size. For good impedance matching performance, a coaxial-type short stub is inserted inside the sleeve. Leakage current on the outer conductor of a coaxial cable due to miniaturization and the sleeve structure is suppressed by using an L-shaped open stub inside the sleeve. The designed small SDA is miniaturized by up to 34.8% compared to a normal SDA. Input impedance is matched below S11 of -20 dB at 1.5 GHz, and the measured -10-dB bandwidth is 70 MHz (4.6%). The average leakage current on the outer conductor of the coaxial cable is 5.1 dB lower than a normal.