Patent ID: 8344943

Claim:
A retrodirective antenna comprising: (a) a transmit antenna array having at least one row of N transmit elements with each transmit element located in a first common plane at a common transmit radial distance from a center of the transmit antenna array, and each transmit element having a common spacing with its neighboring transmit elements over a defined angular transmit range, and each having a defined transmit azimuth position around the center of the transmit antenna array; (b) a receive antenna array having at least one row of N receive elements with each receive element located in a second common plane spaced from the first common plane, and each receive element having common receive radial distance from a center of the receive antenna array, wherein the center of the receive antenna is located along a line that extends through the center of the transmit antenna array and is perpendicular to the plane of the transmit antenna array, and wherein each of the N transmit elements have a corresponding receive element, and wherein each of the corresponding transmit and receive elements have azimuth positions selected from the group consisting of (1) matching azimuth positions and (2) azimuth positions that are offset by a fixed amount which is less than the difference in azimuth positions between neighboring transmit elements; (c) radio-frequency electronic components that join corresponding transmit and receive elements and drive each transmit element with a desired waveform such that retrodirectivity is provided between the received and transmitted radiation patterns, wherein either the “N” transmit elements or the “N” receive elements have “endfire” radiation patterns and are located on a horizontal plane while the other of the “N” receive elements or “N” transmit elements have “broadside” radiation patterns and are located on a surface of a cylinder, wherein the cylinder has an axis that is perpendicular to the plane.