General Dynamics Corporation, Electronics Division

USA As Represented by Secretary of the Navy

General Dynamics Corporation

Eugene L Rope

Gus P Tricoles

Roy S Luoma

Gary L Vance

Jonathan Roussos

Dary R Stewart

A radome diagnostic system comprises a rotatably mounted turntable having support memebers for supporting a radome in a radome support area on the turntable, and a scanning assembly on the turntable for supporting a probe antenna in the radome support area and for translating the probe antenna in perpendicular x and y directions to cover a predetermined planar scanning area. A reference antenna is mounted on the turntable to provide a reference signal, and both the reference antenna and the probe antenna are connected to a suitable receiver for receiving signals from them and for suitably analyzing the collected data. A transmitter is located at a position remote from the turntable to direct radiation towards a radome mounted on the turntable. The probe antenna will detect radiation as degraded or modified by the effect of the presence of the radome in the radiation path. The reference antenna receives unperturbed radiation.

Radome diagnostic system

A vehicle-mounted passive synthetic aperture system for locating sources of electromagnetic radiation having a given wavelength .lambda.. The system includes first and second receiving antennas, a phase sensitive receiver and a signal processor. The first and second antennas are mounted to a vehicle and spaced apart from each other in the principle direction of motion associated with the vehicle. The first and second antennas respectively provide first and second received signals in response to a wavefront of electromagnetic radiation having the given wavelength .lambda.. The phase sensitive receiver is coupled to the first and second antennas and responds to the first and second received signals by providing a phase difference signal that indicates a phase difference .phi. between the wavefronts of the radiation of the given wavelength received by the respective first and second antennas when the received radiation is radiated spherically from its source. The speed of the vehicle also is measured. The signal processor processes the phase difference signal in combination with the measured vehicle speed to provide imaging signals for an object-space display of an image of the source of the electromagnetic radiation in relation to the location of the vehicle. The image is displayed. The system of the present invention effectively uses the motion of the vehicle to synthesize an aperture. The synthesized aperture is long relative to the spacing between the receiving antennas (which spacing is limited by vehicle size) so that angular resolution is greater than that of a fixed antenna system with a baseline length equal to the spacing between the receiving antennas of the present system.

Passive synthetic aperture system for imaging a source of

An antenna-radome structure that functions as a self-referencing interferometer, including a radome having a leading edge and including a plurality of longitudinally disposed slabs of dielectric material having a front edge adjacent the leading edge of the radome; and a corresponding number of antennas disposed normal to the longitudinal axis of the radome and respectively embedded in or placed on the surface of each corresponding dielectric slab. Each antenna is located at a distance from the front end of the corresponding dielectric slab corresponding to a maximum of intensity in an intensity fringe pattern produced by interference between free space waves of a predetermined frequency incident upon the dielectric slab and waves guided by the dielectric slab in response to the incident waves. The thickness of each dielectric slab is tapered for reducing sidelobe levels in the far field pattern of the antenna. A metal foil covers the rear end of each slab for reducing backlobes in the far field antenna pattern and for reducing reflection of the guided waves. Wires are embedded in or placed on the surface of each dielectric slab for defining the shape of the far field of the antenna and for reducing sidelobe levels in the far field pattern of the antenna. Additional antennas may be disposed normal to the longitudinal axis of the radome.

Integrated antenna-radome structure that functions as a self-referencing

A vehicle-mounted passive synthetic aperture system for locating a source of electromagnetic radiation having a given wavelength .lambda.. The system includes first and second receiving antennas, a phase sensitive receiver and a signal processor. The first and second antennas are mounted to a vehicle and spaced apart from each other in the principle direction of motion associated with the vehicle. The first and second antennas respectively provide first and second received signals in response to electromagnetic radiation having the given wavelength .lambda.. The phase sensitive receiver is coupled to the first and second antennas and responds to the first and second received signals by providing a phase difference signal that indicates a phase difference that is proportional to the difference between the respective ranges from the first and second antennas to the source of the received radiation when the received radiation is radiated spherically from its source. The signal processor is coupled to the receiver for processing the phase difference signal in combination with the measured speed of the vehicle to determine the range and direction from the vehicle to the source of the electromagnetic radiation. The system of the present invention effectively uses the motion of the vehicle to synthesize an aperture. The synthesized aperture is long relative to the spacing between the receiving antennas (which spacing is limited by vehicle size) so that angular resolution is greater than that of a fixed antenna system with a baseline length equal to the spacing between the receiving antennas of the present system.

Passive synthetic aperture system for locating a source of

A direction finding antenna system including a self-referencing interferometer for determining the direction of a source that emits plane wave radiation. The interferometer includes a slab of dielectric material for passing incident plane waves and for guiding coherent waves excited by the incident plane waves, whereby the guided waves interfere with the incident plane waves passing through the slab to form intensity fringe patterns, wherein the fringe spacing in a given dimension along the non-incident surface of the slab equals 2.pi.(K.sub.g -K.sub.o sin .theta.).sup.-1, wherein K.sub.g is the propagation constant of the dielectric material, K.sub.o is the propagation constant of free space, and .theta. is the angle between the normal to the incident surface of the slab and the direction of the incident plane waves. The interferometer further includes an array of sensors distributed on the non-incident surface of the slab for providing sensing signals that indicate the intensity of the interfering waves at predetermined locations on the non-incident surface of the slab. The antenna system is particularly useful in a randome of a guided missile or aricraft.

Antenna system employing a self-referencing microwave interferometer for

A passive system and method for enabling the display of an image of the location of emitters of electromagnetic radiation that is effective in the lower portion of the HF band. The system essentially includes an array of antennas for receiving electromagnetic radiation from emitters, and for providing a received signal from each emitter in response to the received radiation; a receiver system coupled to each antenna of the array for measuring the phase and intensity of each received signal, and for providing separate coherent phase signals and amplitude signals that respectively indicate the measured phase and intensity; and a signal processor coupled to the receiver system for processing the coherent phase signals and amplitude signals to provide an image signal for generating an image of the emitters. A display device, such as a cathode ray tube or a graph plotter, is coupled to the signal processor for displaying the image of the location of the emitters in response to the image signal.

Determining the location of emitters of electromagnetic radiation

A method and apparatus for measuring radiant energy scattering characteristics of a test panel of dielectric material over a sphere are disclosed. The test panel is supported on a turntable at a position on the axis of the turntable. The turntable has a first antenna radially mounted thereon for rotation therewith and directed toward the position of the supported test panel. A second antenna is mounted for selective positioning along a circular arc within a plane that includes the axis of the turntable, which arc extends at least ninety degrees from said axis, wherein the second antenna is radially directed toward the position of a test panel that is axially supported on the turntable at all positions along said arc. The test panel support is rotated with respect to the turntable to selectively position the test panel at a predetermined incidence angle with respect to the first antenna. The turntable is rotated with respect to the second antenna to selectively position the test panel at an angle with respect to the axis of propagation of the second antenna that is equal to and opposite the predetermined incidence angle. Radiation transmitted between the first and second antenna is measured with the test panel in the supported position at each of a plurality of predetermined equal and opposite incidence angles with respect to the first and second antennas; and radiation transmitted between the first and second antennas is measured at each of the plurality of predetermined incidence angles when the test panel is not supported on the turntable. The second antenna is position at a plurality of positions along the circular arc at various ones of the predetermined incidence angles at which measurements are made as described above. Further measurements are made, both with the test panel in its supported position on the turntable and with test panel absent, of the radiation transmitted between the first and second antennas at the plurality of positions along the circular arc at the various ones of the predetermined incidence angles. The reflectance characteristics of the test panel are then determined by subtracting the measurements taken without the test panel in place from those taken with the test panel supported on the turntable.

Three-dimensional measurement of radiant energy scattering

A method and apparatus for measuring radiant energy scattering characteristics of a test panel of dielectric material over a circular arc are disclosed. The test panel is supported on a turntable at a position on the axis of the turntable. The turntable has a fist antenna radially mounted thereon for rotation therewith and directed toward the position of the supported test panel. The test panel support is rotated with respect to the turntable to selectively position the test panel at a predetermined incidence angle with respect to the first antenna. The turntable is rotated with respect to a second antenna which is in a fixed stationary position and directed toward the supported position of the test panel to selectively position the test panel at an incidence angle with respect to the axis of propagation of the second antenna that is equal to and opposite the predetermined incidence angle. Radiation transmitted between the first and second antennas is measured with the test panel in the supported position at each of a plurality of predetermined equal and opposite incidence angles with respect to the first and second antennas; and radiation transmitted between the first and second antennas is measured at each of the plurality of predetermined incidence angles when the test panel is not supported on the turntable. The reflectance characteristics of the test panel are then determined by subtracting the measurements taken without the test panel in place from those taken with the test panel supported on the turntable.

Measurement of radiant energy scattering characteristics with a

A method for determining antenna near-fields from measurements on a spherical surface. Phase and intensity values are measured by scanning a probe antenna over a spherical surface. The method applies both to planar or conformal antennas. The spherical surface may be in the Fresnel or Fraunhofer regions. The field at the antenna is computed utilizing the complex conjugate of the measured field. As a result, the source antenna at the point at which the antenna radiating field is evaluated is inside the measurement surface. Far-field patterns can be computed from the near-fields reconstructed from the spherical hologram surface.

Method for determining antenna near-fields from measurements on a

A radome having arrays of thin strips of dielectric material on both the inside and outside walls of a conical shell defined by a sheet of dielectric material for compensating for the polarization dependent phase delay of the radome shell is disclosed. The strips of the outside array are supported edgewise on the outside wall and are normal thereto. The outside strips are equally spaced from each other, and disposed so that the intersection of lines extending therefrom is at the vertex of the shell. The strips of the inside array are supported edgewise on the inside strips wall. The inside strips are spaced from one another and tilted from the inside wall at an angle of approximately 45 degrees in a direction away from the vertex of the shell. Each of the inside strips is a frustum of a cone disposed with its axis along the axis of the shell. The tilt of the inside strips increases the transmittance bandwidth of the radome and further decreases dependence of phase delay upon the angle of incidence.

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El Cajon, CA, United States of America

Eugene L Rope