A method for launching a round from an airborne platform, receiving a plurality of RF signals at the round, determining an amount of time between a first and second received RF signal, where the second signal is a multi-path signal and the first signal is a direct path signal. An altitude of the round is determined based on the delay between the first and second received signal and aligning the round's flight path with an initial velocity vector of the aircraft platform to reduce dispersion. The round can include a plurality of sensors for detecting the RF signals. The second received RF signal may be a multi-path signal having been reflected off of the earth's surface or another object on the earth's surface. The altitude of the round can be determined using the known altitude of the airborne platform, the delay of time between the first and second received signals, and the speed of light.

Methods, apparatus and systems for wireless sensing based on linkwise motion statistics (link-MS) are described. In one example, a described method comprises: determining a plurality of heterogeneous wireless devices of a wireless sensing system in a venue; determining a plurality of device-links each of comprises two of the heterogeneous wireless devices, one functioning as a transmitter and the other functioning as a receiver; for each respective device-link of the plurality of device-links, transmitting a respective wireless signal from a respective transmitter of the respective device-link through a wireless multipath channel of the venue, wherein the wireless multipath channel is impacted by a motion of an object in the venue, receiving the respective wireless signal by a respective receiver of the respective device-link through the wireless multipath channel, wherein the respective received wireless signal differs from the respective transmitted wireless signal due to the wireless multipath channel of the venue and the motion of the object, obtaining a respective time series of channel information (TSCI) of the wireless multipath channel based on the respective received wireless signal of the respective device-link, computing a respective link-MS for the respective device-link based on the respective TSCI; performing a sensing task associated with the motion of the object based on at least one of: all the TSCI or all the link-MS; and computing a location in the venue associated with the sensing task based on all the link-MS.

A radar system and method are provided for reducing multipath interference signals. The multipath interference signals can be reduced by the radar system emitting electromagnetic waves that creates a null in the direction of expected multipath interference signals, such that the multipath interference signals are void (or substantially void) from signals received by the radar system.

A method for radio measuring applications, wherein a first radio node functions as an initiator and a second radio node as a transponder, each radio node has its own timer and a data interface, in a first step, the initiator transmits a first carrier frequency as an initial signal and the initial signal is received by the transponder during a first reception period, in a second step, a response signal with a second carrier frequency is transmitted by the transponder and the response signal is received by the initiator during a second reception period. The initial signal and the response signal are coherent at least during each sequence of steps, the carrier frequency of the initial signal is changed within one predetermined frequency domain with each repetition.

A mechanism is provided to determine if a short-range automotive radar detection is a direct reflection or an indirect (also known as “multipath”) reflection from a physical target object. The multipath information is further used to perform a height estimation of the object. Embodiments provide a radar system having a range resolution smaller than a path difference between the direct reflection path and the indirect reflection path. Both range separation techniques and Doppler separation techniques are utilized to provide a reliable and accurate estimation of the height of the object.

A method includes receiving a first wireless signal detected by a first device in an environment, the first wireless signal including a first distortion pattern caused by an object moving in the environment, receiving a second wireless signal detected by a second device in the environment, the second wireless signal including a second distortion pattern caused by the object moving in the environment, determining, by comparing the first distortion pattern to the second distortion pattern, that the first distortion pattern and the second distortion pattern correspond to a same movement event associated with the object moving in the environment, determining a timing offset between the first device and the second device based on information associated with the first distortion pattern and the second distortion pattern, and determining, based on the timing offset, temporal correspondences between data generated by the first device and data generated by the second device.

An interactive system includes a device configured to output a signal toward a surface such that the signal reflects off the surface at an angle and along a path of travel, and such that an object that interrupts the path of travel of the signal causes a return signal to travel in a reverse direction along the path of travel for receipt by the device. The interactive system also includes a control system communicatively coupled to the device. The control system is configured to receive data from the device, in which the data is associated with the receipt of the return signal by the device, and determine a position of the object relative to the device based on the data.

A passive radar comprises a reception antenna for a signal transmitted by a non-cooperative transmitter, the received signal comprising a static contribution related to propagation of the signal transmitted through a multi-path propagation channel and a dynamic contribution related to propagation of echoes of the transmitted signal from a moving target. The passive radar also comprises a reception chain that includes an analogue-digital converter capable of outputting a digitised signal, a moving target detection unit, a digitised signal processing unit configured to determine an estimation of the static contribution during a calibration phase of the passive radar, a transmission chain that can output an analogue signal representative of the estimation of the static contribution, and a directional coupler configured to output the signal received during the calibration phase of the passive radar to the reception chain.

A system and method for locating radio-frequency identification tags within a predetermined area. The method can incorporate sub-threshold superposition response mapping techniques, alone, or in combination with other methods for locating radio-frequency identification tags such as but not limited to time differential on arrival (TDOA), frequency domain phase difference on arrival (FD-PDOA), and radio signal strength indication (RSSI). The system can include a plurality of antennas dispersed in a predefined area; one or more radio-frequency identification tags; a radio-frequency transceiver in communication with said antennas; a phase modulator coupled to the radio-frequency transceiver; and a system controller in communication with said transceiver and said phase modulator. Calibration techniques can be employed to map constructive interference zones for improved accuracy.

In a general aspect, various fields of a PHY frame are used for motion detection. In some aspects, a first training field and a second, different training field are identified in a PHY frame of each wireless signal transmitted between wireless communication devices in a wireless communication network. A first time-domain channel estimate and a second time-domain channel estimate are generated for each wireless signal. The first time-domain channel estimate is based on a first frequency-domain signal included in the first training field, while the second time-domain channel estimate is based on a second frequency-domain signal included in the second training field. A determination is made whether motion has occurred in a space during the time period based on the first time-domain channel estimates, and a location of the motion within the space is determined based on the second time-domain channel estimates.