An apparatus for detecting a presence of an object can include a plurality of electrically conductive loops arranged in an array. The apparatus includes a sensor circuit configured to determine a characteristic associated with each of the plurality of loops. The apparatus includes a hardware processor configured to, for each loop of the plurality of loops, determine a parameter based on the characteristic associated with the loop and the characteristic associated with at least one adjacent loop. The hardware processor may be further configured to determine the presence of the object based on the parameter. The parameter may comprise a sum of a difference between the characteristic associated with the loop and a reference value for the characteristic, and a difference between the characteristic associated with each of the at least one adjacent loop and the reference value.

A technique relates to a microwave device. A pump resonator, at a first pump resonator end, is connected to both a dispersive nonlinear element and a first stub. The pump resonator, at a second pump resonator end, is capacitively coupled to a pump port, where the first stub is terminated in an open circuit. A quantum signal resonator, at a first quantum signal resonator end, is connected to both the dispersive nonlinear element and a second stub. The quantum signal resonator, at a second signal resonator end, is capacitively coupled to a signal port, where the second stub is connected to ground.

A disclosed indirect antenna testing apparatus may include (1) a Near Field Communication (NFC) interface that includes an NFC coil, the NFC interface dimensioned to receive a test NFC device while positioning the test NFC device within an effective range of the NFC coil, and (2) a Vector Network Analyzer (VNA) electrically coupled to the NFC coil and configured to (A) emit a signal via the NFC coil, and (B) monitor for a resonance from the test NFC device within at least one predetermined electromagnetic band. Various additional control devices, apparatuses, systems, and methods are also disclosed.

A system that incorporates the subject disclosure may include, for example, a circuit for receiving a request to initiate a first multiple-input and multiple-output (MIMO) communication session and a second MIMO communication session, and configuring a first antenna configuration and a second antenna configuration to enable the first MIMO communication session and the second MIMO communication session. The first MIMO communication session shares spectrum from the first antenna configuration and the second antenna configuration, and the second MIMO communication session utilizes spectrum from the second antenna configuration that differs from the shared spectrum. Other embodiments are disclosed.

A system that incorporates the subject disclosure may include, for example, a circuit for initiating a first multiple-input and multiple-output (MIMO) communication session with a primary base station, and initiating a second MIMO communication session with a first secondary base station of a plurality of secondary base stations without terminating the first MIMO communication session with the primary base station. The primary base station can include a primary antenna system having a first communication range, while each of the plurality of secondary base stations can include a secondary antenna system having a second communication range that is a subset of the first communication range of the primary antenna system. The plurality of secondary base stations can correspond to a plurality of small cell sites distributed within the first communication range of the primary base station. Other embodiments are disclosed.

A system that incorporates the subject disclosure may include, for example, a circuit for determining a magnitude difference between a first signal supplied to an antenna and a second signal radiated by the antenna, determining a phase difference between the first signal supplied to the antenna and the second signal radiated by the antenna, measuring a change in reactance of an antenna, detecting an offset in an operating frequency of the antenna based on one of the magnitude difference, the phase difference, the change in reactance, or any combination thereof, and adjusting a resonant frequency of the antenna to mitigate the offset in the operating frequency of the antenna. Other embodiments are disclosed.

A technique relates to a microwave device. A pump resonator, at a first pump resonator end, is connected to both a dispersive nonlinear element and a first stub. The pump resonator, at a second pump resonator end, is capacitively coupled to a pump port, where the first stub is terminated in an open circuit. A quantum signal resonator, at a first quantum signal resonator end, is connected to both the dispersive nonlinear element and a second stub. The quantum signal resonator, at a second signal resonator end, is capacitively coupled to a signal port, where the second stub is connected to ground.

A technique relates to a microwave device. A pump resonator, at a first pump resonator end, is connected to both a dispersive nonlinear element and a first stub. The pump resonator, at a second pump resonator end, is capacitively coupled to a pump port, where the first stub is terminated in an open circuit. A quantum signal resonator, at a first quantum signal resonator end, is connected to both the dispersive nonlinear element and a second stub. The quantum signal resonator, at a second signal resonator end, is capacitively coupled to a signal port, where the second stub is connected to ground.

In a general aspect, a method is described herein for detecting the phase properties of a radio frequency (RF) wave. The method includes generating an optical signal by interacting laser signals with a vapor of a vapor cell sensor. The optical signal is based on a transmission of one of the laser signals through the vapor. The method also includes altering an intensity of the optical signal by interacting a target RF electromagnetic field with a Rydberg electronic transition of the vapor. The target RF electromagnetic field includes a time series of RF pulses. The method additionally includes determining, by operation of a signal processing system, a magnitude of phase change in the time series of RF pulses. In some implementations, the method includes determining a phase of a target RF pulse in the times series of RF pulses.

In a general aspect, a system is described herein for detecting the phase properties of a radio frequency (RF) wave. The system includes a vapor cell sensor that contains a vapor and is configured to generate an optical signal in response to laser signals that interact with the vapor. The vapor has a Rydberg electronic transition that interacts with a target RF electromagnetic field, and the optical signal is based on a transmission of one of the laser signals through the vapor. The system also includes an optical detection system and a signal processing system. The optical detection system is configured to generate a detector signal in response to receiving the optical signal, and the signal processing system is configured to receive the detector signal and perform operations that determine a phase change of the target RF electromagnetic field.