Abstract: Various illustrative embodiments disclosed herein generally pertain to detecting defects by using a radio-frequency debugging signal transmitted by a transmitting antenna array towards a receiving antenna located in a far-field region of the transmitting antenna array. The radio-frequency debugging signal, which is configured to provide information pertaining to a signal radiation distribution of the transmitting antenna array, is received in the receiving antenna and conveyed to a test unit. The test unit digitizes the received radio-frequency debugging signal to obtain a digital dataset and applies a back-propagation algorithm to the digital dataset for deriving a reconstructed near-field representation of the transmitting array.

Abstract: Illustrative embodiments disclosed herein pertain to a thermal imaging system that includes a thermal imaging sheet having an array of thermal unit cells for generating a thermal footprint in response to receiving an RF signal. The thermal footprint is composed of an array of hotspots having a first set of hotspots indicative of a radiation characteristic of a first polarization component of the RF signal, and a second set of hotspots indicative of a radiation characteristic of a second polarization component of the RF signal. Each thermal unit cell includes a first RF antenna and a second RF antenna oriented orthogonal with respect to each other. The first RF antenna includes a terminating resistor that generates a hotspot among the first set of hotspots and the second RF antenna includes another terminating resistor that generates a hotspot in the second set of hotspots.

Abstract: Illustrative embodiments disclosed herein pertain to a thermal imaging system that includes a thermal imaging sheet having an array of thermal unit cells for generating a thermal footprint in response to receiving an RF signal. The thermal footprint is composed of an array of hotspots having a first set of hotspots indicative of a radiation characteristic of a first polarization component of the RF signal, and a second set of hotspots indicative of a radiation characteristic of a second polarization component of the RF signal. Each thermal unit cell includes a first RF antenna and a second RF antenna oriented orthogonal with respect to each other. The first RF antenna includes a terminating resistor that generates a hotspot among the first set of hotspots and the second RF antenna includes another terminating resistor that generates a hotspot in the second set of hotspots.

Abstract: Various illustrative embodiments disclosed herein generally pertain to detecting defects by using a radio-frequency debugging signal transmitted by a transmitting antenna array towards a receiving antenna located in a far-field region of the transmitting antenna array. The radio-frequency debugging signal, which is configured to provide information pertaining to a signal radiation distribution of the transmitting antenna array, is received in the receiving antenna and conveyed to a test unit. The test unit digitizes the received radio-frequency debugging signal to obtain a digital dataset and applies a back-propagation algorithm to the digital dataset for deriving a reconstructed near-field representation of the transmitting array.

Abstract: Various illustrative embodiments disclosed herein generally pertain to an RF reflector incorporating a number of reflection apodization elements, each of which is mounted upon a signal reflecting surface of the RF reflector with an inner edge in substantial contact with an inner portion of the signal reflecting surface and an outer edge elevated above a peripheral portion of the signal reflecting surface. The outer edge is elevated to a height corresponding to a quarter-wavelength of a predefined wavelength. This arrangement bestows a gradually variant reflectance characteristic to the RF reflector, with the inner edge of each reflection apodization element providing substantially the same amount of reflectance as the signal reflecting surface of the RF reflector and the outer edge providing substantially no reflectance at the peripheral portion of the signal reflecting surface.

Abstract: A scanning panel for use in a microwave imaging system captures a microwave image of a target using two complementary arrays of antenna elements. Each of the antenna elements in a first array is capable of being programmed with a respective phase delay to direct a transmit beam of microwave illumination toward the target in a transmit beam pattern, and each of the antenna elements in a second array is capable of receiving reflected microwave illumination reflected from the target in a receive beam in a receive beam pattern complementary to the transmit beam pattern. The microwave image of the target is formed at an intersection between the transmit beam and the receive beam.

Abstract: A microwave imaging system suppresses sidelobes in a microwave image captured using a sparse antenna array using an illumination system that operates in two different illumination modes. The antenna array including subarrays of antenna elements arranged in a sparse geometry to form complementary subarray patterns. The illumination system operates in a first mode to transmit microwave illumination to both of the complementary subarray patterns of the antenna array and receive reflected microwave illumination from both of the complementary subarray patterns of the antenna array to produce a first receive signal. The illumination system further operates in a second mode to transmit microwave illumination to a first one of the complementary subarray patterns of the antenna array and receive reflected microwave illumination from a second one of the complementary subarray patterns of the antenna array to produce a second receive signal.

Abstract: A reflectarray utilizes switching devices with non-ideal impedance characteristics to vary the impedance of reflecting elements. The antennas of the reflecting elements are configured as a function of the impedance of the non-ideal switching devices to provide optimal phase-amplitude performance. In particular, the antennas are configured such that the impedance of each antenna is proportional to the square root of the impedance of the non-ideal switching devices when in an on state and when in an off state.

Abstract: An inspection system uses microwave radiation to capture a microwave image of a transportable item. The system includes a transmit scanning panel including a transmit array of transmit antenna elements, each being programmable with a respective phase delay to direct a transmit beam of microwave radiation toward a target of the transportable item for transmission of the microwave radiation through the target. The system further includes a receive scanning panel including a receive array of receive antenna elements, each being programmable with a respective phase delay to receive a receive beam of microwave radiation from the target. A processor measures the amplitude and phase of the microwave radiation in the receive beam to determine a relative value of a pixel within the microwave image of the transportable item based on a reference value of the pixel.

Abstract: A technique for imaging an object with a coherent beam of electromagnetic radiation involves sequencing at least a portion of the coherent beam through a set of orthogonal transverse spatial modes and summing the output signals that result from set of orthogonal transverse spatial modes. To create an image of an object, the coherent beam is applied to multiple spots on the object and sequenced through the same set of orthogonal transverse spatial modes at each spot. The output signals generated from the sequencing are summed on a per-spot basis.

Abstract: A security inspection system uses microwave radiation to image targets on a human subject or other item. The system includes an array of antenna elements that are programmable with a respective phase delay to direct a beam of microwave illumination toward a target on the human subject or item. The antenna elements are further capable of receiving reflected microwave illumination reflected from the target. A processor is operable to measure an intensity of the reflected microwave illumination to determine a value of a pixel within an image of the human subject or item. Multiple beams can be directed towards the human subject or item to obtain corresponding pixel values for use by the processor in constructing the image.

Abstract: A nonpolarization-dependent method and apparatus for optical sampling of a user optical signal of a known frequency range (e.g., corresponding to 1550 nm wavelength) uses a probe signal in an unsplit form and applies a conversion {e.g., by sum frequency generation (SFG)} operation in a first stage to the probe signal and to a first polarization component of the user optical signal (e.g., ‘s’ component) to produce a first component of an output signal. In a second stage, a second polarization component of the user optical signal (e.g., ‘p’ component) is rotated by 90° to align with the first polarization component and then converted by mixing with the unsplit probe signal to produce a second component of an output signal. The first and second output component signals are both added and measured using a photomultiplier tube (PMT) or an avalanche diode.

Abstract: A nonlinear crystal has increased spectral acceptance. The nonlinear crystal includes a plurality of domains. The domains are arranged serially across the nonlinear crystal. The domains have alternating polarity. The poling periods of the domains are varied across the nonlinear crystal so as to provide nonuniform chirping of phase matching of focused optical signals propagated through the nonlinear crystal.

Abstract: A lanthanum aluminate (LaAlO3) substrate on which thin films of layered perovskite copper oxide superconductors are formed. Lanthanum aluminate, with a pseudo-cubic perovskite crystal structure, has a crystal structure and lattice constant that closely match the crystal structures and lattice constants of the layered perovskite superconductors. Therefore, it promotes epitaxial film growth of the superconductors, with the crystals being oriented in the proper direction for good superconductive electrical properties, such as a high critical current density. In addition, LaAlO3 has good high frequency properties, such as a low loss tangent and low dielectric constant at superconductive temperatures. Finally, lanthanum aluminate does not significantly interact with the superconductors. Lanthanum aluminate can also be used to form thin insulating films between the superconductor layers, which allows for the fabrication of a wide variety of superconductor circuit elements.

Abstract: A nonlinear crystal has increased spectral acceptance. The nonlinear crystal includes a plurality of domains. The domains are arranged serially across the nonlinear crystal. The domains have alternating polarity. The poling periods of the domains are varied across the nonlinear crystal so as to provide nonuniform chirping of phase matching of focused optical signals propagated through the nonlinear crystal.

Abstract: A nonpolarization-dependent method and apparatus for optical sampling of a user optical signal of a known frequency range (e.g., corresponding to 1550 nm wavelength) uses a probe signal in an unsplit form and applies a conversion {e.g., by sum frequency generation (SFG) }operation in a first stage to the probe signal and to a first polarization component of the user optical signal (e.g., ‘s’ component) to produce a first component of an output signal. In a second stage, a second polarization component of the user optical signal (e.g., ‘p’ component) is rotated by 90° to align with the first polarization component and then converted by mixing with the unsplit probe signal to produce a second component of an output signal. The first and second output component signals are both added and measured using a photomultiplier tube (PMT) or an avalanche diode.

Abstract: A lanthanum aluminate (LaAlO3) substrate on which thin films of layered perovskite copper oxide superconductors are formed. Lanthanum aluminate, with a pseudo-cubic perovskite crystal structure, has a crystal structure and lattice constant that closely match the crystal structures and lattice constants of the layered perovskite superconductors. Therefore, it promotes epitaxial film growth of the superconductors, with the crystals being oriented in the proper direction for good superconductive electrical properties, such as a high critical current density. In addition, LaAlO3 has good high frequency properties, such as a low loss tangent and low dielectric constant at superconductive temperatures. Finally, lanthanum aluminate does not significantly interact with the superconductors. Lanthanum aluminate can also be used to form thin insulating films between the superconductor layers, which allows for the fabrication of a wide variety of superconductor circuit elements.

Abstract: A lanthanum aluminate (LaAlO3) substrate on which thin films of layered perovskite copper oxide superconductors are formed. Lanthanum aluminate, with a pseudo-cubic perovskite crystal structure, has a crystal structure and lattice constant that closely match the crystal structures and lattice constants of the layered perovskite superconductors. Therefore, it promotes epitaxial film growth of the superconductors, with the crystals being oriented in the proper direction for good superconductive electrical properties, such as a high critical current density. In addition, LaAlO3 has good high frequency properties, such as a low loss tangent and low dielectric constant at superconductive temperatures. Finally, lanthanum aluminate does not significantly interact with the superconductors. Lanthanum aluminate can also be used to form thin insulating films between the superconductor layers, which allows for the fabrication of a wide variety of superconductor circuit elements.

Abstract: A lanthanum aluminate (LaAlO3) substrate on which thin films of layered perovskite copper oxide superconductors are formed. Lanthanum aluminate, with a pseudo-cubic perovskite crystal structure, has a crystal structure and lattice constant that closely match the crystal structures and lattice constants of the layered perovskite superconductors. Therefore, it promotes epitaxial film growth of the superconductors, with the crystals being oriented in the proper direction for good superconductive electrical properties, such as a high critical current density. In addition, LaAlO3 has good high frequency properties, such as a low loss tangent and low dielectric constant at superconductive temperatures. Finally, lanthanum aluminate does not significantly interact with the superconductors. Lanthanum aluminate can also used to form thin insulating films between the superconductor layers, which allows for the fabrication of a wide variety of superconductor circuit elements.

Abstract: A lanthanum aluminate (LaAlO3) substrate on which thin films of layered perovskite copper oxide superconductors are formed. Lanthanum aluminate, with a pseudo-cubic perovskite crystal structure, has a crystal structure and lattice constant that closely match the crystal structures and lattice constants of the layered perovskite superconductors. Therefore, it promotes epitaxial film growth of the superconductors, with the crystals being oriented in the proper direction for good superconductive electrical properties, such as a high critical current density. In addition, LaAlO3 has good high frequency properties, such as a low loss tangent and low dielectric constant at superconductive temperatures. Finally, lanthanum aluminate does not significantly interact with the superconductors. Lanthanum aluminate can also used to form thin insulating films between the superconductor layers, which allows for the fabrication of a wide variety of superconductor circuit elements.