In recent years, the range of applications for microstrip antennas has been expanding rapidly and so has the complexity of the antenna configuration. Multilayer printed-circuit antennas have been gaining much attention because they can improve antenna characteristics such as bandwidth and side lobe levels. They are also well-suited for multi-frequency operation as well as dual polarization. Frequency adjustment of these antennas can be obtained by loading the antenna with shorting pins or varactor diodes. Because of the complexity of the configurations, these antennas are often designed based on laboratory experimentation. Lacking a versatile CAD tool, the range of applications for these multilayer antennas has not been exploited to the fullest.