Compact size IMT-2000 microstrip antenna for repeater and base stations

We propose a compact size microstrip antenna which can be used for IMT-2000 repeaters and/or base stations. Instead of an expensive Teflon substrate, we use the much lower priced FR-4 substrate. Although the use of a high relative permittivity (/spl epsiv//sub r/=4.7) substrate usually restricts the operation bandwidth, 20 dB return loss bandwidth (VSWR<1.2) is obtained over the frequency range assigned for Korean IMT-2000 (1.92 GHz - 2.17 GHz) by using the structure similar to that proposed by S.D. Targonski et al., (see IEEE Trans. on Antennas and Propagation vol.46, no.9, p.1245-51, 1998). The feedline for the near-resonant size aperture is split into two and has rectangular stubs below the aperture for broadband operation. A parameter study for variations of stub width and length is performed for optimization. The designed microstrip antenna has been fabricated. The simulated impedance is compared with the measured impedance over the frequency range of interest. The simulated radiation pattern is also compared with the measured one. The cross-polarization level is very low and the antenna size is 37 mm /spl times/ 41 mm /spl times/ 19 mm (compact). The simulated return loss and radiation pattern are in good agreement with the measured ones.