Abstract: Methods and systems may image an object of interest using one or more probes. More specifically, such exemplary methods and systems may deliver electromagnetic energy (e.g., microwave energy) using a transmitting antenna to the object while activating a probe to interact with the scattered field and sampling the resulting scattered field using one or more receiving antennas. The sampled electromagnetic energy may then be used to reconstruct an image of the object.

Abstract: A new class of antennas and microwave components are introduced. In this approach a high-permittivity dielectric film is applied (i.e. printed) on a dielectric substrate, which may be grounded. By changing the shape of the high-permittivity film, different microwave devices (e.g. waveguides, filters, couplers, and antennas) are produced. By changing the size and permittivity of the high-permittivity film and dielectric substrate, these elements are designed at different frequencies for different applications. Highly-efficient microwave devices can result due to the absence of surface currents.

Abstract: Methods and systems may image an object of interest using one or more probes. More specifically, such exemplary methods and systems may deliver electromagnetic energy (e.g., microwave energy) using a transmitting antenna to the object while activating a probe to interact with the scattered field and sampling the resulting scattered field using one or more receiving antennas. The sampled electromagnetic energy may then be used to reconstruct an image of the object.

Abstract: A system and a method for measuring properties and health of structures are disclosed. The system comprises a number of sensors connected to a single antenna. Each sensor has a body that defines an electromagnetic resonator. The electromagnetic resonator produces a response signal in response to an interrogation signal. The body is coupled to the structure to so as to allow the parameters of interest alter the resonance properties of the electromagnetic resonators thereby altering the response signal. The sensor further includes a coupler that is coupled to the body. The coupler transfers the interrogation signal into the electromagnetic resonator and transfers the response signal from the electromagnetic resonator. The system further includes an interrogator that generates and transmits the interrogation signal to the sensor. The interrogator also receives the response signal.

Abstract: A system and a method for measuring properties and health of structures are disclosed. The system comprises a number of sensors connected to a single antenna. Each sensor has a body that defines an electromagnetic resonator. The electromagnetic resonator produces a response signal in response to an interrogation signal. The body is coupled to the structure to so as to allow the parameters of interest alter the resonance properties of the electromagnetic resonators thereby altering the response signal. The sensor further includes a coupler that is coupled to the body. The coupler transfers the interrogation signal into the electromagnetic resonator and transfers the response signal from the electromagnetic resonator. The system further includes an interrogator that generates and transmits the interrogation signal to the sensor. The interrogator also receives the response signal.

Abstract: A feedhorn driving method and apparatus allows the establishment of multiple phase centers using only a single multimode feedhorn. At least two higher-order modes are extracted from the feedhorn and weighted in amplitude and phase. The phase center separation is established in accordance with an assigned weights. The feedhorn has application in i.a. moving target indication systems.

Abstract: An antenna having a resonant structure, comprises an antenna element (11) and an adjacent electrode (17A) and control means (22,25) for changing a resonance frequency of the antenna element. The control means may comprise a conductive membrane (17A) spaced from the antenna element. The resonance frequency then is changed by flexing the membrane, conveniently by applying a potential difference between the membrane and an adjacent control electrode.

Abstract: An antenna having a resonant structure, comprises an antenna element (11) and an adjacent electrode (17A) and control means (22,25) for changing a resonance frequency of the antenna element. The control means may comprise a conductive membrane (17A) spaced from the antenna element. The resonance frequency then is changed by flexing the membrane, conveniently by applying a potential difference between the membrane and an adjacent control electrode.

Abstract: A feedhorn driving method and apparatus allows the establishment of multiple phase centers using only a single multimode feedhorn. At least two higher-order modes are extracted from the feedhorn and weighted in amplitude and phase. The phase center separation is established in accordance with an assigned weights. The feedhorn has application in i.a. moving target indication systems.

Abstract: An electronically-steered phased array antenna comprises a plurality of antenna elements, each in the form of a resonant structure, and circuitry for changing resonance frequencies of the antenna elements so as to steer a radiation or reception beam/lobe of the phased array antenna. The antenna elements may comprise a plurality of microwave patch antenna elements each overlying one of a plurality of conductive membranes, but spaced therefrom. The resonance frequency then is changed by flexing the membrane, conveniently by applying a potential difference between the membrane and an adjacent ground plane. Additional or alternatively, phase shifting may be effected by adjusting a propagation delay of each of a plurality of feed lines coupled to the antenna elements, conveniently by means of one or more such membranes disposed adjacent each of the feed lines.

Abstract: A compact high efficiency waveguide feed for reflector antennas includes a dielectric loaded aperture at its end for radiating energy to the reflector. The feed comprises a circular waveguide that carries the dominant TE11 mode, and terminates in a dielectric rod with an end cap. The exposed length of the dielectric rod between the end cap and the waveguide end constitutes a cylindrical aperture that radiates towards the reflector. The end cap and dielectric aperture dimensions are optimized for reflector high efficiency. Its small diameter provides an extremely compact feed, which reduces the sidelobes and operates well with both deep and shallow reflectors. As a result, high efficiency and low sidelobe performance can be obtained with symmetric centre fed reflectors.

Abstract: An end fire microstrip antenna which is particularly suitable for low-profile applications comprises a dielectric substrate having a first surface and an opposite surface. A driven element, a microstrip fedline and a plurality of (parasitic) director elements are provided on the first surface. These elements extend in the same plane and are spaced apart from each other in a longitudinal or end-fire direction of the antenna. Likewise, the director elements are spaced apart from each other in arrow extending in the end-fire direction. The antenna further comprises a ground plane provided on the second surface. The driven element comprises a conductive strip connected at one end to the microstrip feedline and open-circuit at its opposite end. It has at least one undulation in such same plane. The undulation has at least one limb extending transversely to the end-fire direction. A conductive reflector element may be provided behind the driven element.

Abstract: A switched beam antenna comprising several spiral arms with a common axis of rotation and respective inner ends angularly spaced around a common circle generates high gain directional beams at an angle away from the antenna axis. Beam scanning is accomplished by rotating the feed to the arms by means of a commutator circuit. Intermediate beams may be generated by feeding two adjacent antenna terminals simultaneously but with an appropriate phase shift. A comparator may be provided to compare signals from several arms and select the arm yielding maximum signal strength.

Abstract: A dipole feed for a paraboloidal reflector antenna uses a conical reflector to direct the radiation of the dipole towards the concave reflecting surface of the parabola. The size and apex angle of the conical reflector are optimized to yield the desired feed pattern, the optimization parameters depending on the reflector size and focal length and being obtained numerically or experimentally to maximize reflector gain.

Abstract: A novel scanning array antenna is provided with improved gain characteristic which enable a compact form to be employed. The resonant azimuthal modes of separate antenna elements are selected to satisfy certain mathematical relationships which, in effect, form a directional beam which can be steered by a relatively small number of phase shifters. An example of antenna structure is an array of circular microstrip patch in the form of concentric disks each in resonance at one of the azimuthal modes under the disk cavity.

Abstract: The antenna feed includes a waveguide radiator with a conductive flange positioned about the waveguide near its radiating end. The flange includes one or more corrugations which each have tapered walls and which is truncated at its root and crest by a flat or curved plane. The corrugations thus may have a trapezoidal cross-section or a curved root and crest cross-section. The curvature may be sinusoidal.

Abstract: The antenna feed includes a waveguide radiator with a conductive flange positioned about the waveguide near its radiating end. A dielectric element is positioned about the waveguide between the flange and the radiating end and establishes the dielectric surface impedance seen by the waveguide. The dielectric element may consist of one or more layers of dielectric material to form a composite dielectric. One of the layers may be an air gap adjacent to the flange. The size and position of the flange and dielectric element will control the radiation pattern of the beam from the feed.