Design of a Dual-Band Quadrifilar Helix Antenna Using Stepped-Width Arms This communication proposes the design of a quadrifilar helix antenna (QHA) with stepped-width arms and a meander feeding network. The stepped-width arms are applied to reduce the antenna size and adjust the frequency interval for dual-band operation. The feeding network includes a 90°-hybrid chip coupler and two meander lines that are designed to give a 180°-phase delay. The proposed QHA is optimized using a genetic algorithm (GA) and then fabricated to measure its performances in a full anechoic chamber. The results demonstrate that the proposed antenna is suitable to be used for dual-band global positioning system (GPS) applications.