Refinements to the Design of Traveling-Wave Waveguide Slot Arrays

A traveling-wave array of longitudinal slots in the broad wall of a waveguide offers greater impedance bandwidth compared to standing-wave slot arrays. Narrow-beam applications typically require a main beam at a chosen off-broadside direction and low sidelobes in other directions. Since a portion of the input power is dissipated in a load, wideband performance is achieved at the expense of reduced radiation efficiency. Without compensation for the effects of the array element radiation pattern, conventional array synthesis approaches produce sidelobe levels that do not meet the original specification. Existing remedial design techniques use optimization to address either sidelobe performance, impedance bandwidth or efficiency. This paper presents a new design approach that not only ensures that sidelobes specifications are met, but also achieves good impedance matching and high efficiency. The procedure is demonstrated using a 21-element array in standard X-band waveguide and performance is validated though both simulation and measurement.