Abstract: Described is a simultaneous transmit and receive antenna system having a ring array of transmit antenna elements and a receive antenna element disposed on an axis that is perpendicular to and passing through the center of the ring array. Alternatively, the ring array includes receive elements and a transmit antenna element is disposed on the axis perpendicular to the ring array. Opposite antenna elements in the ring array differ in phase by 180° so that a radiation pattern null occurs at the antenna element at the center of the ring array. Also included are at least one ground plane and an electrically-conductive cylinder disposed on the perpendicular axis inside the ring array to provide a high degree of isolation between the transmit and receive antenna elements. The system may be configured for wireless communications, for example, according to WIFI IEEE standard 802.11 or WIMAX IEEE standard 802.16.

Abstract: Described is a simultaneous transmit and receive antenna system having a ring array of transmit antenna elements and a receive antenna element disposed on an axis that is perpendicular to and passing through the center of the ring array. Alternatively, the ring array includes receive elements and a transmit antenna element is disposed on the axis perpendicular to the ring array. Opposite antenna elements in the ring array differ in phase by 180° so that a radiation pattern null occurs at the antenna element at the center of the ring array. Also included are at least one ground plane and an electrically-conductive cylinder disposed on the perpendicular axis inside the ring array to provide a high degree of isolation between the transmit and receive antenna elements. The system may be configured for wireless communications, for example, according to WIFI IEEE standard 802.11 or WIMAX IEEE standard 802.16.

Abstract: A microwave diplexer apparatus for handling simultaneously two independent polarized transmitted signals at one frequency and two independent polarized received signals at a lower frequency. In the transmit mode of operation, a pair of input signals are applied to a first orthogonal mode transducer wherein the electric fields of the signals are established at right angles to each other. The orthogonal, linearly-polarizer signals are then transformed by a pin/ridge-loaded circular polarizer device to oppositely-rotating circularly-polarized signals and coupled via an antenna port of a second orthogonal mode transducer to an antenna for transmission to a desired target.

Abstract: A microwave diplexer apparatus for handling simultaneously two independent polarized transmitted signals at one frequency and two independent polarized received signals at a lower frequency. In the transmit mode of operation of the diplexer apparatus, a pair of input signals to be transmitted to a target are applied to a first orthogonal mode transducer wherein the electric fields of the signals are established at right angles to each other. The orthogonal linearly-polarized signals are then transformed by a pin/ridge-loaded circular polarizer device to oppositely-rotating circularly-polarized signals and coupled via an antenna port of a second orthogonal mode transducer to an antenna for transmission to the desired target.

Abstract: A broadband microwave polarizer device for introducing a differential phase shift between orthogonal components of linear orthogonally-polarized signals, the differential phase shift being relatively constant over a wide range of frequencies, for example, a range of frequencies of 5.925GHz to 6.425GHz.The polarizer device includes a section of waveguide having two opposing rows of pins at inner surface regions thereof, in a first common plane, and two opposing ridges at other inner surface regions thereof in a second common plane transverse to the first plane. By appropriate design of the pins and ridges, a relatively constant resultant phase shift .phi..sub.R may be achieved over the abovementioned bandwidth. The value of .phi..sub.R may be approximated byA.sub.O -B.sub.O +(A.sub.1 -B.sub.1)(f-f.sub.O) + (A.sub.2 -B.sub.2)(f-f.sub.O).sup.2,where f is a selected frequency of the orthogonally-polarized signals, f is the center frequency of the operating frequency bandwidth of the polarizer device, A.sub.O, A.