The sleeve-cage monopole and sleeve helix for wideband operation

We have found that the cage structure and multifilar helices are more amenable than single wire antennas to improvements in VSWR when parasitic wires are added. The helical configuration can be used to reduce the height of the antenna, but at the sacrifice of bandwidth. While the addition of the parasitic wires improves the overall bandwidth, the VSWR increases outside the design band. Fast integral equation solution techniques and optimization methods have been developed in the course of this work and have led to effective tools for designing broadband antennas.