A pyramidal horn monopulse array is proposed for working at Ka-band with circular polarization (CP) characteristic The array is composed of 28 elements with a 28-way waveguide power divider network The element has a pyramidal horn with a rectangular waveguide, which is placed downside the horn There is a 45 - inclined slot cut in the wide wall of the rectangular waveguide The inclined slot can convert the excitation into two orthogonal modes with equal amplitude, and 90 - out of phase is produced due to difierent propagation constants of the two modes in the pyramidal horn Therefore, the antenna can achieve CP by using a compact structure without polarizer This paper also provides procedure of the compact power divider network for synthesizing monopulse pattern This monopulse array has excellent performance: The simulated and measured re∞ection coe-cients of the sum port and difierence port of the array are below i15dB, the side lobe level of array less than i27dB, and axial ratio < 3dB in the mainlobe beamwidth The simulated and measured results are in good agreement

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Horn-Based Circular Polarized Antenna Array with a Compact Feeding for Ka-Band Monopulse Antenna

This paper presents design considerations and measured results for a two element 8 to 12 GHz horn antenna array for transmit/receive applications requiring high isolation. Circular polarization is achieved by incorporating a five layer meanderline circular polarizer over the aperture of the horn antenna. The measured axial ratio for operational antennas including protective radomes is less than 0.85 dB over the entire frequency band. The antennas are fitted with waveguide-to-coax adapters and achieve a VSWR ≤ 1.5∶1 in the fully assembled condition. Installed isolation of better than 78 dB is achieved over most of the frequency band at a prescribed antenna separation of 500 mm.

A. J. Booysen

Papers

Design and development of an 8 to 12 GHz circularly polarized two element horn antenna array with high isolation