In some embodiments, a transmitter has a first mode and a second mode. The transmitter is configured to repeatedly send discrete first wireless signals carrying transmitter identification information uniquely associated with the transmitter in the first mode and to send a second wireless signal carrying the transmitter identification information in the second mode. A receiver is configured to receive a wireless signal of the first wireless signals such that the receiver is activated by the wireless signal of the first wireless signal and, in response to receiving the wireless signal of the first wireless signals, to send a third wireless signal carrying the transmitter identification information to the transmitter. The transmitter is configured to transition from the first mode to the second mode in response to receiving the third wireless signal and determining that the third wireless signal includes the transmitter identification information uniquely associated with the transmitter.

An electronic patient monitoring system and method of operation that includes one or more generally non-metal, tamper-resistant patient identification and monitoring devices, an observer transmitter/receiver device configured to receive and detect one or more beacon signals that exceed a predetermined threshold from at least one of the not easily removable patient identification and monitoring devices, set a time to hold open a window for a response on the transmitter/receiver device, and send a request for information to the observer with the transmitter/receiver device, and a central computer system. Each of the transmitter/receiver device and the central computer system, including, at least, a computer processor, communications components and system software to communicate with the observer transmitter/receiver device at specified/predetermined time intervals to receive observer- and patient-specific information.

A technique for transmitting data from a passive radio device (100) is described. As to a method aspect of the technique, an antenna (102) of the passive radio device (100) is exposed to an incident radio signal (502). A frequency domain representation of the incident radio signal (502) comprised at least one muted gap between active subcarriers within a bandwidth of the incident radio signal (502). The incident radio signal (502) is backscattered from the antenna by modulating an impedance of the antenna according to the data using at least two different modulation frequencies that differ by less than the bandwidth.

Techniques for operating a navigation system are provided. An example method according to these techniques includes determining a first localization solution associated with a location of the vehicle in a navigable environment using a radar transceiver of the navigation system, determining a second localization solution associated with the location of the vehicle in the navigable environment using a LiDAR transceiver, a camera, or both of the navigation system, selecting a localization solution from the first and second localization solutions based on whether an accuracy of the first localization exceeds an accuracy of the second localization solution, and utilizing the selected vehicle localization solution for navigation of the vehicle through the navigable environment.

Inferring product activity includes providing a first product having an attached first harmonic tag; directing, at a first area in which the first product is located, a first transmitted signal of a first frequency; and receiving a first return signal of a first return frequency from the first harmonic tag, wherein the first harmonic tag, upon receiving the first transmitted signal, radiates the first return signal, such that the first return frequency is a harmonic of the first frequency. A computer can then infer, based on the first return signal, a first activity in which the first product is being used.

A method for determining an arrival-time of a rotor blade that includes attaching an RF reader to a stationary surface and an RF tag to the rotor blade. Time-of-flight data points are collected via an RF monitoring process that includes: emitting an RF signal from the RF reader and recording a first time; receiving the RF signal at the RF tag and emitting a return RF signal by the RF tag in response thereto; receiving the return RF signal at the RF reader and recording a second time; and determining the time-of-flight data point as being the duration occurring between the first time and the second time. The RF monitoring process is repeated until multiple time-of-flight data points are collected. A minimum time-of-flight is determined from the multiple time-of-flight data points, and the arrival-time for the rotor blade is determined as being a time that corresponds to the minimum time-of-flight.

A radio-frequency method for range finding includes modulating a reference signal having an intermediate frequency to a downlink signal having a carrier frequency using a clock signal. The downlink signal is transmitted to a tag using a transceiver. An uplink signal backscattered from the tag is received and demodulated using the clock signal. The uplink signal has a frequency that is a harmonic of the carrier frequency. A distance between the tag and the transceiver is calculated based on a phase of the demodulated uplink signal. A system for range finding includes a transceiver and a processor. The transceiver modulates a reference signal to a downlink signal and transmits the downlink signal. The transceiver receives and demodulates an uplink signal. The processor is configured to receive the demodulated uplink signal and calculate a distance between the tag and the transceiver using a phase of the demodulated uplink signal.

A radar system for interacting with navigation targets is provided. The radar system is configured to interact with navigation targets (target devices) that shift the phase of a received radar transmission to generate a phase shifted response signal. Phase shifters (e.g., silicon germanium phase shifters) are designed to assign specific frequency responses from one or more navigation modules to identify target locations. The radar module transmits at a modulated signal at first frequency, each navigation target receives the radar transmission, phase shifts the signal and returns the phase shifted signal. Where two or more navigation targets are used, each will apply a different phase shift to the received radar transmission, wherein the frequency identifies the navigation target devices. In a radar system, the modulated transmission signal is compared to the returned phase shifted signal to determine a frequency difference between the two signals.

A radar system for an autonomous driving vehicle (ADV) is disclosed. The system includes a target that includes a number of target elements disposed in a predetermined configuration on the target to collectively represent a radar readable code. The system further includes a radar unit included in the ADV and configured to: transmit a first electromagnetic (EM) signal to the target within a driving environment, receive a second EM signal reflected by the target, compute a radar cross section (RCS) signature based on the received second EM signal, generate a corresponding communication message based on the computed RCS signature, and transmit radar data that includes the communication message, where the ADV is controlled based on the communication message.

An electronic patient monitoring system and method of operation that includes one or more generally non-metal, tamper-resistant patient identification and monitoring devices, an observer transmitter/receiver device configured to receive and detect one or more beacon signals that exceed a predetermined threshold from at least one of the not easily removable patient identification and monitoring devices, set a time to hold open a window for a response on the transmitter/receiver device, and send a request for information to the observer with the transmitter/receiver device, and a central computer system. Each of the transmitter/receiver device and the central computer system, including, at least, a computer processor, communications components and system software to communicate with the observer transmitter/receiver device at specified/predetermined time intervals to receive observer- and patient-specific information.