Optimized High Gaussicity Smooth Spline-Profile Feed Horns for Terahertz Defog Camera

This paper presents the design of smooth spline-profile feed horns for a novel terahertz passive imaging application—a terahertz defog camera suitable for indoor fire environment monitoring. A method has been proposed which, for a particular desired imaging spatial resolution, can optimize the horn profile for good radiation symmetry and high Gaussicity. The simulated results achieve a Gaussian coupling efficiency exceeding 98%, a gain of 25.3 dBi, a -10 dB HPBW of 9.3°, peak cross-polarizations below -28 dB, and sidelobes at the -30 dB level at 94Ghz. Furthermore, the imaging performance of a focal-plane-array-fed terahertz defog camera is well tested, proving that a smooth-walled spline-profile horn is an easier-processing alternative to the corrugated horn for wideband terahertz millimeter-wave applications.