Abstract: Systems and methods for measuring air gaps between opposing surfaces of two structural components. In one application, such measurements are used to fabricate a shim that fills the air gap between two structural members, such as parts of an aircraft. The resonant inductive coupling-based sensing system has the capability to remotely measure an air gap using an on-board transmit system. Furthermore, the system has the capability to switch between multiple inductor-capacitor sets such as to simultaneously measure air gaps across an area so that a better profile of the air gap can be determined. The resonant inductive coupling-based gap sensor is configured as signal generating and signal sensing electronics printed or mounted on respective flexible substrates to provide a flexible and portable measurement solution.

Abstract: A transceiver assembly is configured to detect an object. The transceiver assembly includes a first transmit antenna array configured to transmit a first signal at a first frequency, a second transmit antenna array configured to transmit a second signal at a second frequency that differs from the first frequency, and a receive antenna array configured to receive a third signal at a third frequency that is a difference between the first frequency and the second frequency. The transceiver assembly detects the object in response to reception of the third signal by the receive antenna array.

Abstract: A transceiver assembly is configured to detect an object. The transceiver assembly includes a first transmit antenna array configured to transmit a first signal at a first frequency, a second transmit antenna array configured to transmit a second signal at a second frequency that differs from the first frequency, and a receive antenna array configured to receive a third signal at a third frequency that is a difference between the first frequency and the second frequency. The transceiver assembly detects the object in response to reception of the third signal by the receive antenna array.

Abstract: A method of detecting a compound in a material sample is presented. A transformation is generated from a set of IR spectra of a set of identified compounds, in which the compound is one of the set of identified compounds. The transformation is applied to an IR spectrum of the material sample to form a transformed IR spectrum. A decomposition is applied to the transformation. Results indicative of a presence or an absence of the compound are generated based on an output of the decomposition.

Abstract: Systems and methods for measuring air gaps between opposing surfaces of two structural components. In one application, such measurements are used to fabricate a shim that fills the air gap between two structural members, such as parts of an aircraft. The resonant inductive coupling-based sensing system has the capability to remotely measure an air gap using an on-board transmit system. Furthermore, the system has the capability to switch between multiple inductor-capacitor sets such as to simultaneously measure air gaps across an area so that a better profile of the air gap can be determined. The resonant inductive coupling-based gap sensor is configured as signal generating and signal sensing electronics printed or mounted on respective flexible substrates to provide a flexible and portable measurement solution.

Abstract: A method of detecting a compound in a material sample is presented. A transformation is generated from a set of IR spectra of a set of identified compounds, in which the compound is one of the set of identified compounds. The transformation is applied to an IR spectrum of the material sample to form a transformed IR spectrum. A decomposition is applied to the transformation. Results indicative of a presence or an absence of the compound are generated based on an output of the decomposition.

Abstract: An antenna. The antenna includes a plurality of loop antennas sharing a common gap. The antenna also includes a nonlinear mixing component connected to the gap and configured to collect energy from at least one of the plurality of loop antennas.

Abstract: A method of detecting a compound in a material sample is presented. A transformation is generated from a set of IR spectra of a set of identified compounds, in which the compound is one of the set of identified compounds. The transformation is applied to an IR spectrum of the material sample to form a transformed IR spectrum. A decomposition is applied to the transformation. Results indicative of a presence or an absence of the compound are generated based on an output of the decomposition.

Abstract: A passive difference-frequency tag including a first antenna on a substrate, the first antenna having a first frequency band, the first antenna having a first shape of a first bowtie with first rounded end caps and first ends opposed to each other. The passive difference-frequency tag also includes a second antenna on the substrate inside the first antenna. The second antenna has a second frequency band higher than the first antenna frequency band. The second antenna having a second shape of a second bowtie with second rounded end caps and second ends opposed to each other. A combination of the first antenna and the second antenna forms a plurality of multi-band antennas with a shared axis of symmetry. The passive difference-frequency tag also includes a diode assembly on the substrate, and connected to the first ends of the first antenna and to the second ends of the second antenna.

Abstract: A passive difference-frequency tag including a first antenna on a substrate, the first antenna having a first frequency band, the first antenna having a first shape of a first bowtie with first rounded end caps and first ends opposed to each other. The passive difference-frequency tag also includes a second antenna on the substrate inside the first antenna. The second antenna has a second frequency band higher than the first antenna frequency band. The second antenna having a second shape of a second bowtie with second rounded end caps and second ends opposed to each other. A combination of the first antenna and the second antenna forms a plurality of multi-band antennas with a shared axis of symmetry. The passive difference-frequency tag also includes a diode assembly on the substrate, and connected to the first ends of the first antenna and to the second ends of the second antenna.

Abstract: Systems and methods for generating radio frequency signals and/or microwave signals using a tunable optical source. An optical frequency comb including multiple optical components is received or generated based on an optical signal. A subset of optical components is selected from the multiple optical components. A detector array having two or more square law detectors is uniformly illuminated with the subset of optical components. Each square law detector of the detector array outputs an electrical signal having a difference frequency corresponding to a difference in frequency between the subset of optical components. A radio frequency or microwave output signal with a narrow bandwidth centered at a target frequency is generated by coherently summing each of the output signals output by the square law detectors.

Abstract: An antenna. The antenna includes a plurality of loop antennas sharing a common gap. The antenna also includes a nonlinear mixing component connected to the gap and configured to collect energy from at least one of the plurality of loop antennas.

Abstract: A method and apparatus for detecting an energetic material on a surface. Electromagnetic radiation is generated. A beam of the electromagnetic radiation is transmitted from a handheld device towards the surface. Reflected electromagnetic radiation from the beam reflecting off of the surface is detected at the handheld device to generate test data. The test data is analyzed at a base unit that is separate from the handheld device to determine whether the energetic material is present on the surface.

Abstract: A method and apparatus for detecting an energetic material on a surface. Electromagnetic radiation is generated. A beam of the electromagnetic radiation is transmitted from a handheld device towards the surface. Reflected electromagnetic radiation from the beam reflecting off of the surface is detected at the handheld device to generate test data. The test data is analyzed at a base unit that is separate from the handheld device to determine whether the energetic material is present on the surface.

Abstract: A coherent fiber array is used to optically detect a radiometric event. The coherent fiber array has a dome-shaped detection surface and a planar output surface. Optical energy from the radiometric event is detected at the dome-shaped detection surface and transferred to the output surface. The coherent fiber array retains directionality of the radiometric event while transferring the optical energy from the dome-shaped detection surface to the planar output surface.

Abstract: A method of evaluating a composite structure in which a portion of the structure is imaged and subsequently transformed to provide a 2D output of the angular distribution of features, eg a 2D FFT. A weighting function is applied to the output to compensate for variation in the angular density of pixel population. The weighted output is then used to provide an angular distribution of feature intensity. The structure can be imaged in two or more intersecting planes to allow a 3D determination of feature direction to be obtained.

Abstract: A coherent fiber array is used to optically detect a radiometric event. The coherent fiber array has a dome-shaped detection surface and a planar output surface. Optical energy from the radiometric event is detected at the dome-shaped detection surface and transferred to the output surface. The coherent fiber array retains directionality of the radiometric event while transferring the optical energy from the dome-shaped detection surface to the planar output surface.

Abstract: A method and apparatus for detecting non-linear tags. In one advantageous embodiment a system for detecting non-linear tags has a transmitter and a receiver. The transmitter transmits a plurality of electromagnetic signals having a first frequency and a second frequency. The receiver monitors for an electromagnetic signal having a frequency equal to a difference between the first frequency and a second frequency that is generated by a non-linear tag in response to receiving the plurality of electromagnetic signals, wherein the non-linear tag is detected when the electromagnetic signal is detected by the receiver.

Abstract: A method and apparatus for detecting objects located underground. In one advantageous embodiment, a detection system detects objects having electrical non-linear characteristics located underground. The detection system comprises a transmitter unit, a receiver, and a processor. The transmitter transmits a plurality of pulsed radio frequency signals having a first frequency and a second frequency into a ground. The receiver monitors for a response radio frequency signal having a frequency equal to a difference between the first frequency and a second frequency, wherein the response radio frequency signal is generated by an object having the non-linear conductive characteristics in response to receiving the plurality of electromagnetic signals. The processor is connected to the transmitter unit and the receiver, wherein the processor controls an operation of the transmitter unit and the receiver, wherein the object is detected when the response radio frequency signal is detected by the receiver.

Abstract: A method and apparatus for detecting objects located underground. In one advantageous embodiment, a detection system detects objects having electrical non-linear characteristics located underground. The detection system comprises a transmitter unit, a receiver, and a processor. The transmitter transmits a plurality of pulsed radio frequency signals having a first frequency and a second frequency into a ground. The receiver monitors for a response radio frequency signal having a frequency equal to a difference between the first frequency and a second frequency, wherein the response radio frequency signal is generated by an object having the non-linear conductive characteristics in response to receiving the plurality of electromagnetic signals. The processor is connected to the transmitter unit and the receiver, wherein the processor controls an operation of the transmitter unit and the receiver, wherein the object is detected when the response radio frequency signal is detected by the receiver.