The transmission-line and the cavity model are utilized in the calculation of the impedance and radiation characteristics of a rectangular microstrip patch antenna. Single, 2×1, 2×2, 4×2, and 8×8 microstrip patch array antennas were desinged and their input impedance and radiation patterns are measuered in the frequency range of 9 GHz to 18 GHz. The Size of the single patch antenna in Ku band is 5.35×7.5㎟, and that of 8×8 microstrip patch array antenna is 10.64×11.3㎠. The measured resonance frequency of the array antenna with uniform current distribution is 18.24 GHz, its gain 26.47dB, and main-to-sidelobe ration 12dB, while the calculated value is 18.44GHz, 24.89dB, and 13dB, respectively. A broadside Dolph-Tschebyscheff array of 8×8 element with a main-to-side lobe ratio of 22dB is designed in Ku-band and the measured value of main-to-sidelobe ratio is 15dB. The 7dB difference between the calculated value and the measured value is due to the power division errors of the power divider.
