Airborne multi-mode radiating and receiving system

In a phased array antenna for a monopulse radar, the antenna elements in such antenna being arranged in n upper rows above a horizontal centerline and n lowers rows below such centerline, in each one of such rows there being an equal number of antenna elements to the left and to the right of a vertical centerline, a constrained feed for each one of the antenna elements, such feed comprising:

• a. a waveguide ladder network, responsive to radio frequency energy to be transmitted, for dividing such energy into an upper and a lower pair of waveguides, the radio frequency energy in the upper pair to be divided between the antenna elements in the n upper rows and the radio frequency energy in the lower pair to be divided between the antenna elements in the n lower rows;
• b. n waveguide-to-stripline couplers disposed along one waveguide in each pair thereof and m waveguide-to-stripline couplers disposed along the other waveguide in each pair thereof, where m is equal to, or less than, n,
• c. 2n stripline ladder networks, each one thereof responsive to the radio frequency energy in a different one of the n upper and lower paths, for further dividing the radio frequency energy in each one of such paths into four serial feed striplines, a first pair of such striplines including a primary and a secondary feed directed toward the antenna elements to the left of the vertical centerline of a row of such elements and a second pair of such striplines including a primary and a secondary feed directed toward the antenna elements to the right of such centerline in the same row;
• and,
• d. stripline coupling means, responsive to the radio frequency energy in each one of the first and the second pair of serial feed striplines, for coupling radio frequency energy to, respectively, the antenna elements to the left and to the right of the vertical centerline in each row of antenna elements.