Abstract: An antenna system is provided that includes a coaxial cable, an antenna, a reflector wall, and a slot wall. The reflector wall is formed of a conductive material connected to a conductive shield to extend in an axial direction, is separated from an antenna conductor by a second dielectric material in a radial direction relative to the antenna conductor, and partially surrounds the antenna conductor in the radial direction from a first angle to a second angle when projected into a radial plane. The slot wall is formed through a portion of the conductive shield to expose a dielectric material from a third angle to a fourth angle when projected into the radial plane, is formed on a first side relative to a base. The first angle, the second angle, the third angle, and the fourth angle are defined relative to a common axis parallel to the radial plane.

Abstract: An antenna system is provided. The antenna system includes a coaxial cable, an antenna, and an impedance matching structure. The coaxial cable includes a center conductor extending a length of the coaxial cable, a dielectric material surrounding the center conductor along the length of the coaxial cable, and a conductive shield surrounding the dielectric material along the length of the coaxial cable. The antenna includes a conductor having an electrical length of half a wavelength at a selected operating frequency. The impedance matching structure includes a second center conductor mounted between an end of the center conductor of the coaxial cable and a feed end of the antenna. The impedance matching structure is configured to match an impedance of the coaxial cable to an impedance of the antenna.

Abstract: An antenna includes a first dipole arm and a second dipole arm. The first dipole arm is connected to a first conductor and is formed of a first conducting material. The first dipole arm extends in an axial direction from the first conductor. The second dipole arm is connected to a second conductor that is distinct from the first conductor and is formed of a second conducting material. The second dipole arm extends in the axial direction from the second conductor and is wound around the first dipole arm to form a number of loops. The second dipole arm does not contact the first dipole arm. An axial length of the second dipole arm in the axial direction is less than 90% of an axial length of the first dipole arm in the axial direction.

Abstract: A balun includes a center conductor, a dielectric material, a tapered wall, a ring, and a prong. The center conductor extends a length of the balun. The dielectric material surrounds the center conductor along the length of the balun. The tapered wall forms a portion of a tube between a first wall and a second wall. The first wall is opposite the second wall. The tapered wall is formed of a conductive material. The portion of the tube forms a slot exposing the dielectric material. The ring connects to the second wall of the tapered wall and is formed of the conductive material. The ring forms a tube surrounding the center conductor and the dielectric material. The prong connects to the ring to extend toward the first wall and is formed of the conductive material. The prong extends over a portion of the dielectric material exposed by the slot.

Abstract: An antenna includes a first dipole arm and a second dipole arm. The first dipole arm is connected to a first conductor and is formed of a first conducting material. The first dipole arm extends in an axial direction from the first conductor. The second dipole arm is connected to a second conductor that is distinct from the first conductor and is formed of a second conducting material. The second dipole arm extends in the axial direction from the second conductor and is wound around the first dipole arm to form a number of loops. The second dipole arm does not contact the first dipole arm. An axial length of the second dipole arm in the axial direction is less than 90% of an axial length of the first dipole arm in the axial direction.

Abstract: An antenna system is provided that includes a coaxial cable, an antenna, a reflector wall, and a slot wall. The reflector wall is formed of a conductive material connected to a conductive shield to extend in an axial direction, is separated from an antenna conductor by a second dielectric material in a radial direction relative to the antenna conductor, and partially surrounds the antenna conductor in the radial direction from a first angle to a second angle when projected into a radial plane. The slot wall is formed through a portion of the conductive shield to expose a dielectric material from a third angle to a fourth angle when projected into the radial plane, is formed on a first side relative to a base. The first angle, the second angle, the third angle, and the fourth angle are defined relative to a common axis parallel to the radial plane.

Abstract: A balun includes a center conductor, a dielectric material, a tapered wall, a ring, and a prong. The center conductor extends a length of the balun. The dielectric material surrounds the center conductor along the length of the balun. The tapered wall forms a portion of a tube between a first wall and a second wall. The first wall is opposite the second wall. The tapered wall is formed of a conductive material. The portion of the tube forms a slot exposing the dielectric material. The ring connects to the second wall of the tapered wall and is formed of the conductive material. The ring forms a tube surrounding the center conductor and the dielectric material. The prong connects to the ring to extend toward the first wall and is formed of the conductive material. The prong extends over a portion of the dielectric material exposed by the slot.

Abstract: An antenna system is provided. The antenna system includes a coaxial cable, an antenna, and an impedance matching structure. The coaxial cable includes a center conductor extending a length of the coaxial cable, a dielectric material surrounding the center conductor along the length of the coaxial cable, and a conductive shield surrounding the dielectric material along the length of the coaxial cable. The antenna includes a conductor having an electrical length of half a wavelength at a selected operating frequency. The impedance matching structure includes a second center conductor mounted between an end of the center conductor of the coaxial cable and a feed end of the antenna. The impedance matching structure is configured to match an impedance of the coaxial cable to an impedance of the antenna.

Abstract: Microwave examination of individuals is carried out by transmitting microwave signals from multiple antenna locations into an individual and receiving the backscattered microwave signals at multiple antenna locations to provide received signals from the antennas. The received signals are processed to remove the skin interface reflection component of the signal and the corrected signal data are provided to a hypothesis testing process. In hypothesis testing for detecting tumors, image data are formed from the test statistic used to perform a binary hypothesis test at each voxel. The null hypothesis asserts that no tumor is present at a candidate voxel location. The voxel threshold is determined by specifying a false discovery rate to control the expected proportion of false positives in the image. When the test statistic value associated with a voxel is greater than the threshold, the null hypothesis is rejected and the test statistic is assigned to the voxel.

Abstract: A system and a method are provided for estimating the average dielectric properties of a plurality of regions in space. The application of this technique is illustrated for determining the average properties of breast tissue. The knowledge of average properties is important when UWB microwave radar signal processing algorithms are used for tumor detection and localization. The method is an extension of a time-domain inverse scattering algorithm based on the finite-difference time-domain method. A hybrid conjugate gradient optimization is used to minimize a cost function defined between a measured and a calculated total electromagnetic field at a series of antennas. The output of the method is an average set of electromagnetic material parameters that describe specific regions of interest in either a non-dispersive heterogeneous medium or a dispersive heterogeneous medium.

Abstract: Microwave imaging via space-time beamforming is carried out by transmitting microwave signals from multiple antenna locations into an individual to be examined and receiving the backscattered microwave signals at multiple antenna locations to provide received signals from the antennas. The received signals are processed in a computer to remove the skin interface reflection component of the signal at each antenna to provide corrected signal data. The corrected signal data is provided to a beamformer process that time shifts the received signals to align the returns from a scatterer at a candidate location, and then passes the time aligned signals through a bank of filters, the outputs of which are summed, time-gated and the power therein calculated to produce the beamformer output signal at a candidate location. The beamformer is then scanned to a plurality of different locations in the individual by changing the time shifts, filter weights and time-gating of the beamformer process.

Abstract: Microwave imaging via space-time beamforming is carried out by transmitting microwave signals from multiple antenna locations into an individual to be examined and receiving the backscattered microwave signals at multiple antenna locations to provide received signals from the antennas. The received signals are processed in a computer to remove the skin interface reflection component of the signal at each antenna to provide corrected signal data. The corrected signal data is provided to a beamformer process that time shifts the received signals to align the returns from a scatterer at a candidate location, and then passes the time aligned signals through a bank of filters, the outputs of which are summed, time-gated and the power therein calculated to produce the beamformer output signal at a candidate location. The beamformer is then scanned to a plurality of different locations in the individual by changing the time shifts, filter weights and time-gating of the beamformer process.

Abstract: A microwave antenna for use in a system for detecting an incipient tumor in living tissue such as that of a human breast in accordance with differences in relative dielectric characteristics. In the system a generator produces a non-ionizing electromagnetic input wave of preselected frequency, usually exceeding three gigahertz, and that input wave is used to irradiate a discrete volume in the living tissue with a non-ionizing electromagnetic wave. The illumination location is shifted in a predetermined scanning pattern. Scattered signal returns from the living tissue are collected and processed to segregate skin tissue scatter and to develop a segregated backscatter or return wave signal; that segregated signal, in turn, is employed to detect any anomaly indicative of the presence of a tumor or other abnormality in the scanned living tissue.