This paper presents a design of a new dual-polarized monopulse reflector antenna for W-band seeker applications. The monopulse pattern is realized using a new dual-polarized single-aperture multi-mode horn fed by four square waveguides. Existing designs of a single-aperture multi-mode horn can operate with single polarization only. The dimensional parameters of the proposed horn are adjusted iteratively to obtain required sum and difference patterns and low input reflection coefficient. The designed feed has the following sum and difference pattern characteristics: sum channel gain of 18.2dBi, gain taper in the E-and H-planes of 11.6dB and 12.4dB at 22.3°; difference channel gain of 16.8dBi, gain taper in the E-and H-planes of 2.8dB and 4.4dB at 22.3°, and null depth of greater than 50dB. A high-performance W-band monopulse seeker antenna is realized by combining the designed feed horn with a 50-wavelength Cassegrain reflector. The designed seeker antenna has sum pattern gain of 42.2dBi, beamwidth of 1.41°, cross-over angle of 1.61°, null depth of 49.7dB, and side-lobe level of-16.8dB.

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The lens antenna is one of favorable types of antenna at millimeter-wave frequencies since it is structurally simple and of small size. This paper presents a design of a high-performance 35GHz monopulse lens antenna with high aperture efficiency and low sidelobes for missile seeker applications. First, a lens is designed based on the antenna requirements. Next, a monopulse feed is designed utilizing tapered dielectric rods. For ease in the implementation of the monopulse comparator network, a 5-element configuration is adopted where the sum-channel element is separated from difference-channel elements. Finally the monopulse feed and the lens are combined to complete the antenna design. The designed antenna with a 16-wavelength diameter aperture has the sum-channel performance of 32.3dBi gain, 4.24° beamwidth,-28.4dB sidelobe level, and the difference-channel performance of 29.0dBi gain, 2.36° cross-over angle,-23.5dB sidelobe level, and null depth of greater than 40dB.

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