In many applications such as automobiles on busy highways, if a lot of vehicles on road are equipped with Doppler radars to help improve driving safety, no matter human-driven or auto-driven, if the radars use same frequency band, avoiding interference between them is a hard task. Assigning distinct frequencies is one of the solutions, however not only it wastes expensive spectrum resource, but also the task itself to dynamically assign frequency to vehicles randomly come together becomes a hard one to do. The disclosed invention of Doppler group radar will allow radar devices to work together using shared frequency band without interfering one another, without sacrificing performance, and without much increase in costs.

A water surface and underwater dual-purpose automatic positioning and tracking system and method, which belongs to the field of marine environment observation technologies. The positioning and tracking system includes: a rope winding and unwinding structure, arranged on a main hull structure; where the rope winding and unwinding structure includes a rope roller and a winding and unwinding rope wound around the rope roller; an auxiliary positioning remote control ship, located outside a main body of the main hull structure, where the auxiliary positioning remote control ship is in transmission and fixed connection with the winding and unwinding rope away from the rope roller; communication control units, arranged on the main hull structure and the auxiliary positioning remote control ship; and an automatic positioning tracker unit, arranged on the hull structure, where the automatic positioning tracker unit is in remote communication connection with the communication control units.

A real-time location system including a backbone communication network having a plurality of network access point devices and a real-time location system server, a plurality of monitor devices where each monitor device being located at a location around a facility, each of the plurality of monitor devices being configured to transmit a unique monitor identification code using a secondary transmission technology, each of the monitor identifications codes being mapped to a single location in the facility at which a monitor device is located, each of the monitor devices further being configured to transmit an RF beacon using a first RF protocol, and at least one tag being configured to receive, detect and retransmit the monitor identification code back to at least one of the plurality of monitor devices using a second RF protocol.

An underwater transmitter may generate underwater pressure waves that encode bits of data. The pressure waves may travel to, and created minute vibrations in, the water's surface. An airborne radar may detect radar signals that reflect from the water's surface. The surface vibrations may modulate the phase of the reflected radar signal. The radar receiver may, based on the variation in the phase of the reflected radar signal, decode the data that was initially encoded in the underwater pressure waves. The underwater pressure waves may be frequency modulated, such as by orthogonal frequency-division multiplexing. Alternatively, the surface vibrations may be detected by a camera, interferometer or other light sensor. Alternatively, the pressure waves may propagate through a media other than water. For instance, the pressure waves may propagate through bodily tissue, or may propagate through oil or a liquid fracking mixture in an oil or gas well.

An underwater transmitter may generate underwater pressure waves that encode bits of data. The pressure waves may travel to, and created minute vibrations in, the water's surface. An airborne radar may detect radar signals that reflect from the water's surface. The surface vibrations may modulate the phase of the reflected radar signal. The radar receiver may, based on the variation in the phase of the reflected radar signal, decode the data that was initially encoded in the underwater pressure waves. The underwater pressure waves may be frequency modulated, such as by orthogonal frequency-division multiplexing. Alternatively, the surface vibrations may be detected by a camera, interferometer or other light sensor. Alternatively, the pressure waves may propagate through a media other than water. For instance, the pressure waves may propagate through bodily tissue, or may propagate through oil or a liquid fracking mixture in an oil or gas well.

The present disclosure relates to a location determination system that includes acoustic transmitting devices (104), location tags (112), and a wireless mesh network (106), where the wireless mesh network uses battery-powered devices. A location tag receives acoustic signals (e.g., ultrasound signals) from an acoustic transmitting device. Clocks from members of the wireless mesh network are synchronized by observation of clock pairings, each clock pair formed by respective clocks in a transmitting device that transmits a message and a receiving device that receives the message. By analyzing the observed clock pairings, a best fit between the clock pairings may be determined. After selecting a reference clock, an acoustic transmission schedule may be propagated to the respective acoustic transmitting device.

A transmitter is disclosed. The transmitter includes a clock configured to generate one or more output clock signals. The transmitter further includes at least one frequency divider configured to generate a plurality of divided frequencies based on the one or more output clock signals, and a modulator. The transmitter also includes at least one antenna or transducer configured to transmit modulated data. The transmitter includes a memory configured to store instructions, and at least one processor configured to execute instructions performing operations including mapping data to a decimal code value of a plurality of decimal code values, converting the decimal code value to a shrinking base system, and selecting a set of frequencies among the plurality of divided frequencies based on the code value corresponding to the shrinking base system for the decimal code value. The modulator may be configured to modulate the decimal code value using the set of frequencies.

An assembly and method for detecting cross bores and the location of underground pipe system assets includes an acoustic generator placed within an interior of the sewer system and an acoustic receiver placed within proximity of the lateral(s) of the pipe system. The acoustic generator generates an acoustic signal to transmit through the interior of a sewer pipe of the sewer system. A controller detects, in response to the acoustic receiver hearing the acoustic signal, a location of the underground pipe.

An assembly and method for detecting cross bores and the location of underground pipe system assets includes an acoustic generator placed within an interior of the sewer system and an acoustic receiver placed within proximity of the lateral(s) of the pipe system. The acoustic generator generates an acoustic signal to transmit through the interior of a sewer pipe of the sewer system. A controller detects, in response to the acoustic receiver hearing the acoustic signal, a location of the underground pipe.

An unmanned underwater vehicle (UUV) is equipped with a GPS, heading sensor, depth and altitude sensors, and an acoustic navigation system. The UUV is deployed in the vicinity of the target location and releases an acoustic transponder (beacon). Using the acoustic navigation system with the GPS reference, the UUV conducts a survey to determine the horizontal location of the beacon on the seafloor and calculates a relative position between the beacon and the target. The UUV can plan a travel path allowing it to relocate the target, using the beacon as a navigation aid. The UUV can submerge to target depth and search for the target using a forward looking sensor. Once the target is acquired on the sensor, the UUV can home to the target.