Theory and simulation of 3 mm conical horn focusing lens antennas

The design of focusing lens based on traditional ray path method is introduced. The performances of 3 mm focusing lens antennas are simulated by using electromagnetic simulation software. Antennas with different spread angles (12,20,30) of horn are simulated. Its concluded that the actual focal length increases and approaches to the value designed gradually when the spread angle of horn increases, and the ray path method can be applied when the electromagnetic wavelength is short enough compared with the horn aperture. The E-field on the focal planes of the three antennas is presented and the focal spot of the antenna with 30 spread angle is smaller than twice the electromagnetic wavelength.