Abstract: A system/device, such as a gradiometer probe for detecting RF signals, or for example for explosive detection, has the shape of the coils in its adjustment mechanism that minimizes the cross-talk between the receiver probe (Rx) and the transmitting antenna (Tx) in such a way as to minimize (or reduce) the areas where the distance between the coils during the adjustment is the smallest. Moving coils along the plain of the coils is one mechanism of achieving it. Having the coils of different shapes, e.g., circular receiver and oval transmitter coils, is another. Many shapes are possible, including circular, oval, elliptical, and polygonal, to give a few examples. In some embodiments both of these methods/approaches are combined in a single device.

Abstract: An apparatus includes an antenna, a transmitter configured to generate an outgoing electrical signal, and a receiver configured to receive an incoming electrical signal. The apparatus also includes a transformer configured to couple the antenna and the transmitter such that the outgoing electrical signal causes the antenna to radiate outgoing electromagnetic energy, couple the antenna and the receiver such that the incoming electrical signal is based on incoming electromagnetic energy received by the antenna, and electrically isolate the transmitter and the receiver. The antenna may include inner and outer compensating coils, the compensating coils may be configured to additively radiate the outgoing electromagnetic energy, and the incoming electrical signal may be based on a difference between the incoming electromagnetic energy as received by the compensating coils.

Abstract: An apparatus includes an antenna, a transmitter configured to generate an outgoing electrical signal, and a receiver configured to receive an incoming electrical signal. The apparatus also includes a transformer configured to couple the antenna and the transmitter such that the outgoing electrical signal causes the antenna to radiate outgoing electromagnetic energy, couple the antenna and the receiver such that the incoming electrical signal is based on incoming electromagnetic energy received by the antenna, and electrically isolate the transmitter and the receiver. The antenna may include inner and outer compensating coils, the compensating coils may be configured to additively radiate the outgoing electromagnetic energy, and the incoming electrical signal may be based on a difference between the incoming electromagnetic energy as received by the compensating coils.

Abstract: A noise cancelling gradiometer probe includes an insulating material having a first side and a second side; a first, second, third and fourth coaxial cables forming a first, second, third and fourth loops, respectively, where a portion of each of the first, second, third and fourth loops is locating on the first side of the insulating material and a portion of the first, second, third and fourth loops is locating on the second side of the insulating material.

Abstract: A system includes a table and a material detection system. The material detection system includes a transmit chain configured to generate first radio frequency (RF) signals and a transmit probe configured to transmit the first RF signals towards an item through open space. The material detection system also includes a receive probe configured to receive second RF signals from the item through open space, where the second RF signals have one or more characteristics indicative of one or more materials within the item. The material detection system further includes a receive chain configured to process the second RF signals and at least one processing device configured to identify the one or more materials within the item using nuclear quadrupole resonance (NQR) spectrometry based on the processed second RF signals. The transmit and receive probes are positioned in an upper portion of the table.

Abstract: A system/device, such as a gradiometer probe for detecting RF signals, or for example for explosive detection, has the shape of the coils in its adjustment mechanism that minimizes the cross-talk between the receiver probe (Rx) and the transmitting antenna (Tx) in such a way as to minimize (or reduce) the areas where the distance between the coils during the adjustment is the smallest. Moving coils along the plain of the coils is one mechanism of achieving it. Having the coils of different shapes, e.g., circular receiver and oval transmitter coils, is another. Many shapes are possible, including circular, oval, elliptical, and polygonal, to give a few examples. In some embodiments both of these methods/approaches are combined in a single device.

Abstract: A system includes a table and a material detection system. The material detection system includes a transmit chain configured to generate first radio frequency (RF) signals and a transmit probe configured to transmit the first RF signals towards an item through open space. The material detection system also includes a receive probe configured to receive second RF signals from the item through open space, where the second RF signals have one or more characteristics indicative of one or more materials within the item. The material detection system further includes a receive chain configured to process the second RF signals and at least one processing device configured to identify the one or more materials within the item using nuclear quadrupole resonance (NQR) spectrometry based on the processed second RF signals. The transmit and receive probes are positioned in an upper portion of the table.

Abstract: Antenna structures including two anti-symmetrically wound transformers to compensate for stray radiation. In one example an antenna structure includes a transformer assembly connected between an antenna and first and second balanced signal contacts, the transformer assembly including first and second transformer cores independently positionable in space relative to one another, a pair of primary windings connected to the antenna in parallel with one another, and a pair of balanced secondary windings connected in parallel with one another between the first and second balanced signal contacts.

Abstract: A noise cancelling gradiometer probe includes an insulating material having a first side and a second side; a first, second, third and fourth coaxial cables forming a first, second, third and fourth loops, respectively, where a portion of each of the first , second, third and fourth loops is locating on the first side of the insulating material and a portion of the first , second, third and fourth loops is locating on the second side of the insulating material.

Abstract: A system and method for detecting a nucleus of interest in a chemical using a nuclear quadrupole resonance transition. An excitation pulse is used to excite one or more nuclei of interest, if they present in a sample, to an excited state, the energy of which depends on the magnetic field in the sample. The magnetic field in the sample is modulated, after the end of the excitation pulse, while the nuclei of interest decay from the excited state, so that the radiation they emit is frequency modulated. The frequency modulation is detected in the emitted radiation. In some embodiments a DC magnetic field is applied to the sample, during the application of the excitation pulse, to tune the frequency of the transition being excited.

Abstract: Examples of passive diode-based transmitter detuning circuits and low-voltage active diode-based and receiver detuning circuits are provided.

Abstract: A system and method for detecting a nucleus of interest in a chemical using a nuclear quadrupole resonance transition. An excitation pulse is used to excite one or more nuclei of interest, if they present in a sample, to an excited state, the energy of which depends on the magnetic field in the sample. The magnetic field in the sample is modulated, after the end of the excitation pulse, while the nuclei of interest decay from the excited state, so that the radiation they emit is frequency modulated. The frequency modulation is detected in the emitted radiation. In some embodiments a DC magnetic field is applied to the sample, during the application of the excitation pulse, to tune the frequency of the transition being excited.

Abstract: Examples of passive diode-based transmitter detuning circuits and low-voltage active diode-based and receiver detuning circuits are provided.

Abstract: Antenna structures including two anti-symmetrically wound transformers to compensate for stray radiation. In one example an antenna structure includes a transformer assembly connected between an antenna and first and second balanced signal contacts, the transformer assembly including first and second transformer cores independently positionable in space relative to one another, a pair of primary windings connected to the antenna in parallel with one another, and a pair of balanced secondary windings connected in parallel with one another between the first and second balanced signal contacts.

Abstract: The location of a transmitter transmitting a signal may be estimated by receiving the signal at each receiver of a plurality of receivers, where the receivers are in motion relative to the transmitter. The following are performed for pairs of receivers to yield phase differences: establishing a first phase offset of the signal as received at a first receiver; establishing a second phase offset of the signal as received at a second receiver; and determining a phase difference corresponding to the pair of receivers in accordance with the first phase offset and the second phase offset. A location of the transmitter is estimated in accordance with the plurality of phase differences.