A flat aperture waveguide sidewall-emitting twist-reflector (FAWSET) antenna, having an E-plane sectoral flare having a depth merely the H-plane width of the waveguide. Extending the E-plane sectoral flare is a twist-reflector tilted from one sidewall of the E-plane flare and a trans-reflector extending from another opposing sidewall of the E-plane flare. An angle between distal end of the twist-reflector and the trans-reflector is a function of the frequency of the incoming wave.