Annular slot monopulse antennas

This paper describes the design and performance of annular slot planar arrays which generate pencil beams and monopulse tracking beams in both principal planes. These planar arrays consist of a transmission line in the form of a radial waveguide whose upper plate contains annular groups of linear slots. Monopulse operation is obtained by dividing the transmission line into four independently excited quadrants, each of which is propagating a field configuration identical to the dominant H01radial waveguide mode. The antennas radiate linear polarization. In contrast with many other types of two-dimensional waveguide slot arrays, the antennas can be fabricated inexpensively. Small diameter versions are shown to possess the following electrical and mechanical advantages when compared to a dish antenna of comparable size: 1) better gain through increased aperture efficiency, 2) improved backlobe suppression, and 3) compact size and lower weight. The experimental design was done at X-band.