A broadband circularly polarized reflector antenna with high isolation between transmitter and receiver channels is demonstrated theoretically and experimentally. The proposed antenna achieves $\vert S_{11}\vert dB, gain > 21 dBic (with a maximum value of 28 dBic) over the 4–8 GHz operating frequency range. A dual-polarized coaxial cavity antenna is designed to serve as the feed for the axis-symmetry reflector antenna. The inner conductor of the coaxial cavity antenna is extended to integrate the feed with the reflector; therefore, avoiding the use of mounting struts. The proposed configuration is used to realize an antenna subsystem for monostatic simultaneous transmit and receive (STAR)/full-duplex applications. The monostatic STAR operation is achieved by the use of a simple, low-loss beamformer network where hybrids and circulators are arranged to cancel any signal leakage from transmitting to receiving paths leading to high isolation. Practically, the proposed system achieves measured isolation >30 dB which is bounded by the amplitude and phase imbalances of the deployed commercial off-the-shelf components.

Broadband Reflector Antenna With High Isolation Feed for Full-Duplex Applications

An antenna feed system capable of simultaneously receiving and transmitting in multiple frequency bands is disclosed. In one embodiment, the feed system comprises a dielectric loading rod, an inner cylindrical waveguide, and one or more outer cylindrical waveguides. The dielectric loading rod lies along a central axis, as do the inner waveguide and outer waveguides. The axis of the inner waveguide and the rod may coincide. Each waveguide may be configured to receive and transmit a different frequency band simultaneously with the other waveguides. In addition, the axes of the outer waveguides also coincide with the central axis. The antenna feed system may further comprise one or more junctions disposed to propagate electromagnet radiation into and out of the inner waveguide and outer waveguides. A method and kit for simultaneously receiving and transmitting in multiple frequencies are also disclosed.

Method and apparatus for transmitting and receiving multiple frequency bands simultaneously

Based on a systematic analysis the design and experimental studies on a composite dual-frequency feed with a single radiating aperture are presented. The criterion for selecting the ratio of the diameter of the corrugated guide excited at the lower frequency in the dominant mode to that of the dielectric rod, axially located within the guide and excited at the higher frequency in the dominant mode, is discussed. The constructional features of a typical dual-frequency feed designed for operation at S and X bands (with 2.68 GHz and 9.375 GHz as center frequencies, respectively) are outlined. The measured radiation patterns show good symmetry and sidelobe suppression over 20-percent bandwidth in S and X bands and are in good agreement with calculated patterns.

Propagation and radiation characteristics of dielectric loaded corrugated dual-frequency circular waveguide horn feeds

An antenna feed in a satellite system that provides substantially equal E-plane and H-plane patterns. The feed includes outer and inner conductive walls that are coaxial, and define an outer waveguide therebetween and an inner waveguide within the inner conductive wall. The feed includes a first cylindrical waveguide section, a tapered waveguide section, and a second cylindrical waveguide section at the aperture of the feed. Downlink signals are in signal communication with the first cylindrical waveguide section so that the downlink signals are launched into the outer waveguide and out of the feed. Uplink signals received by the inner waveguide are directed to suitable uplink reception devices. One or both of the outer or inner conductive walls include an array of radially disposed iris pins at the aperture that interact with the uplink and/or downlink signals to provide beam symmetry or equal E-plane and H-plane patterns.

Dual frequency coaxial feed with suppressed sidelobes and equal beamwidths

Wideband Bi-Static and Monostatic Star Antenna Systems

The TE_{11} mode coaxial waveguide or horn radiator provides a natural geometry for multiple frequency confocal feeding of a paraboloid reflector antenna system. Its radiation patterns, however, are generally characterized by unequal E - and H -plane beamwidths and high E -plane sidelobe amplitudes. These characteristics become increasingly more obvious for coaxial radiators designed to illuminate reflector systems requiring feeds with reduced fields of view, such as the symmetrical paraboloid reflector antenna with large focal-length-to-diameter ratio or the offset paraboloid reflector antenna. Left uncorrected, these feed characteristics severely limit the available antenna performance. Incorporation of a radial reactive iris in the aperture plane of a TE_{11} mode coaxial radiator has been found to produce rotationally symmetric pattern characteristics with reduced sidelobe levels. This paper describes an approximate technique for determining the radiation patterns of a TE_{11} mode coaxial radiator with a radial aperture reactance. Experimental results are shown that reveal the pattern improvements predicted by the analysis. A multiple frequency coaxial feed that employs radial aperture reactances is capable of providing the aforementioned reflector systems with a high performance capability.

C. Profera

Papers

Improvement of TE 11 mode coaxial waveguide and horn radiation patterns by incorporation of a radial aperture reactance