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 a near-field probe having loops or coils of electrically-conductive material, where the near-field probe is configured to generate a magnetic field. The apparatus also includes a power amplifier configured to drive the near-field probe. The apparatus further includes a shunt capacitance coupled in parallel across the loops or coils of the near-field probe. The shunt capacitance and an inductance of the loops or coils of the near-field probe form part of a resistive-inductive-capacitive (RLC) network. The RLC network is configured to transform a smaller resistance of the near-field probe into a larger resistance. In some cases, the apparatus may include multiple near-field probes coupled in series, and the power amplifier may be configured to drive the multiple near-field probes. For each near-field probe, the apparatus may include a shunt capacitance coupled in parallel across the loops or coils of the near-field probe.

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: An apparatus includes a near-field probe having loops or coils of electrically-conductive material, where the near-field probe is configured to generate a magnetic field. The apparatus also includes a power amplifier configured to drive the near-field probe. The apparatus further includes a shunt capacitance coupled in parallel across the loops or coils of the near-field probe. The shunt capacitance and an inductance of the loops or coils of the near-field probe form part of a resistive-inductive-capacitive (RLC) network. The RLC network is configured to transform a smaller resistance of the near-field probe into a larger resistance. In some cases, the apparatus may include multiple near-field probes coupled in series, and the power amplifier may be configured to drive the multiple near-field probes. For each near-field probe, the apparatus may include a shunt capacitance coupled in parallel across the loops or coils of the near-field probe.

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: In some embodiments, a near-field sensor comprises an antenna system, transmit circuitry configured to transmit pulses via the antenna system, and receive circuitry configured to receive interrogation signals in response to transmitted pulses. The antenna system can include a first conductive path having one or more loops coupled together, and a second conductive path having one or more loops coupled together, wherein the first and second conductive path are electrically isolated from each other within the antenna system. The transmit circuitry can include a matching network to dissipate energy stored in the transmit circuitry following transmission of a pulse. The receive circuitry can include a suppression network configured to dissipate residual energy within the receive circuitry resulting from transmission of the pulse.

Abstract: An antenna system is provided comprising first, second, and third loop antennas, each antenna having a respective loop area and spaced apart from the other antennas. The first and third antennas are configured and driven to form a first independent balanced feed point that is substantially isolated from the second antenna, which is configured to be driven from a second balanced feed point. A sum of the first and second respective loop areas, at a sum port in operable communication with the first and second balanced feed points, is substantially equivalent to the third respective loop area. An automatic control system is configured to automatically and independently adjust, via the balanced feed points, at least one of amplitude and phase for at least one of the three loop antennas, to help to substantially maximize suppression of RFI for a sum of signals from the first and second balanced feed points.

Abstract: An antenna system comprising a plurality of loop antenna sets with each of the plurality of loop antenna sets disposed in one of a plurality of different parallel planes with each of the planes being spaced apart from another adjacent plane and wherein loop antenna set in the plurality of loop antenna sets comprises a plurality of loop antennas and wherein the plurality of loop antennas are configured such that the near field inductive coupling between the plurality of loop antenna sets is zero. The absence of inductive coupling between the loop elements provides a frequency-independent means for multiplexing signals for transmission and reception by the multiple loop antenna system.

Abstract: An antenna system is provided comprising first, second, and third loop antennas, each antenna having a respective loop area and spaced apart from the other antennas. The first and third antennas are configured and driven to form a first independent balanced feed point that is substantially isolated from the second antenna, which is configured to be driven from a second balanced feed point. A sum of the first and second respective loop areas, at a sum port in operable communication with the first and second balanced feed points, is substantially equivalent to the third respective loop area. An automatic control system is configured to automatically and independently adjust, via the balanced feed points, at least one of amplitude and phase for at least one of the three loop antennas, to help to substantially maximize suppression of RFI for a sum of signals from the first and second balanced feed points.

Abstract: A system for protecting radio frequency (RF) communications and related techniques includes generating masking signals at an RF device such as a radio frequency identification (RFID) card.

Abstract: An antenna system comprising a plurality of loop antenna sets with each of the plurality of loop antenna sets disposed in one of a plurality of different parallel planes with each of the planes being spaced apart from another adjacent plane and wherein loop antenna set in the plurality of loop antenna sets comprises a plurality of loop antennas and wherein the plurality of loop antennas are configured such that the near field inductive coupling between the plurality of loop antenna sets is zero. The absence of inductive coupling between the loop elements provides a frequency-independent means for multiplexing signals for transmission and reception by the multiple loop antenna system.

Abstract: An antenna for protecting radio frequency communications includes a masking portion to broadcast a masking signal including a first loop and a second loop connected to the first loop, wherein a current supplied to the masking portion flows in opposite polarity in each of the first and second loops. The antenna includes a reader loop to receive a response signal from a responder and decoupled from the masking signal, wherein the masking signal masks the response signal about the responder.

Abstract: An antenna includes a first loop defining a first enclosed area and having a first phase center point, a second loop coupled to the first loop and disposed substantially parallel to the first loop, the second loop defining a second enclosed area, and a third loop coupled to the first loop and the second loop and substantially parallel to the first loop, the third loop defining a third enclosed area with a plurality of adjuster elements coupled to at least one of the first loop, the second loop, or the third loop to provide an adjustable loop and configured to expand or contract the enclosed area of the adjustable loop.

Abstract: A system for protecting radio frequency (RF) communications and related techniques includes generating masking signals at an RF device such as a radio frequency identification (RFID) card.

Abstract: An antenna for protecting radio frequency communications includes a masking portion to broadcast a masking signal including a first loop and a second loop connected to the first loop, wherein a current supplied to the masking portion flows in opposite polarity in each of the first and second loops. The antenna includes a reader loop to receive a response signal from a responder and decoupled from the masking signal, wherein the masking signal masks the response signal about the responder.

Abstract: An adjustable antenna enables far-field radiation from the antenna to be reduced, minimized, and/or substantially eliminated while near-field radiation from the antenna may be substantially maintained. In some embodiments, an antenna includes a first loop defining a first enclosed area and having a first phase center point defined by the geometric center point of the first enclosed area, a second loop coupled to the first loop and disposed substantially parallel to the first loop, the second loop defining a second enclosed area and a second phase center point defined by the geometric center point of the second enclosed area, and a third loop coupled to the first loop and the second loop and substantially parallel to the first loop, the third loop defining a third enclosed area and a third phase center point defined by the geometric center point of the third enclosed area.

Abstract: A radio-frequency identification (RFID) inlay is provided that is substantially isolated from the environment in proximity to one side of the device. A radio-frequency identification (RFID) inlay is provided including a two-port microchip having a first and a second port, a first antenna coupled to the first port of the two-port microchip, a ground-plane, a first high-impedance body disposed substantially parallel to the first antenna and between the first antenna and the ground-plane, the first high-impedance body insulated from the ground-plane. The RFID inlay further includes a second antenna coupled to the second port of the two-port microchip, and a second high-impedance body disposed substantially parallel to the second antenna and between the second antenna and the ground-plane, the second high-impedance body insulated from the ground-plane.

Abstract: A radio-frequency identification (RFID) inlay is provided that is substantially isolated from the environment in proximity to one side of the device. A radio-frequency identification (RFID) inlay is provided including a two-port microchip having a first and a second port, a first antenna coupled to the first port of the two-port microchip, a ground-plane, a first high-impedance body disposed substantially parallel to the first antenna and between the first antenna and the ground-plane, the first high-impedance body insulated from the ground-plane. The RFID inlay further includes a second antenna coupled to the second port of the two-port microchip, and a second high-impedance body disposed substantially parallel to the second antenna and between the second antenna and the ground-plane, the second high-impedance body insulated from the ground-plane.

Abstract: An antenna is provided including a first loop having at least one first conductor and a second loop having at least one second conductor, the second conductor connected to the first conductor. The first loop has a first enclosed area defined by the area inside the perimeter of the first loop and a first phase center point defined by the geometric center point of the first enclosed area. The second loop is coupled to the first loop and is disposed a distance from and substantially parallel to the first loop. The second loop has a second enclosed area substantially equal to the first enclosed area and a second phase center point. A line normal to the plane of the first loop passes through the first and second phase center points. The first and second loops are disposed to substantially reduce the far-field illumination, while substantially maintaining the near-field illumination at effective radio frequency identification system operational levels.