Horn Antenna with Miniaturized Size and Increased Gain by Loading Slow-Wave Periodic Metal Blocks

An H-plane horn antenna with miniaturized size and increased gain is reported, which is realized by loading slow wave structures (SWSs) inside the shortened horn cavity. The SWSs in the form of periodic metal blocks can decelerate the phase velocity of the electromagnetic wave traveling to the radiating aperture. So the phase difference between the center and the edges of the aperture enlarged by the shortened longitudinal dimension can be compensated, and the longitudinal length of the horn antenna is significantly reduced. Meanwhile, uniform magnitude distribution of electric fields on the aperture is achieved by cleverly designing the heights of embedded blocks. Thus, the realized gain and aperture efficiency are maximized. The proposed horn antenna is easily fabricated by standard mechanical manufacture process. The longitudinal length of the prototype is 33.3% less than the original horn antenna with the same aperture size. Moreover, the average gain is 1.7 dB higher than the original horn, while maximized aperture efficiency up to 80.7% is achieved.