Abstract: A hybrid radar receiver includes an antenna array for receiving an input signal having a radar signal from a signal emitter. Each array element outputs an analog signal on a respective data channel. For each data channel, an activatable A/D converter is provided. A dedicated hardware circuit, which typically includes a detector/log video amplifier that is coupled to a threshold/pulse digitizer, is included to determine when a radar pulse is being received. When the circuit determines that a pulse is being received, the circuit activates each A/D converter to generate a digital signal on each channel. When a pulse is not currently being received, the circuit deactivates each A/D converter and digital signals are not produced. Pulse parameter(s) generated by the hardware circuit and the digital signals on each channel are sent to a software equipped processor which implements a signal emitter identification algorithm.

Abstract: A device for activating a signal emitter for use in a firefighter locator system operates in conjunction with the firefighter's self-contained breathing apparatus (SCBA). The activation device includes a pressure sensor to monitor pressure on an air line that delivers air from the SCBA air tank to the SCBA air regulator. When the firefighter opens the SCBA air tank valve, pressure is sensed in the air line and the emitter is activated to transmit a signal. The signal is received by base stations that then use the signal to locate/track the signal emitter. Preferably, the activating system also includes a user operated reset button(s) and a shutoff circuit to allow the user to stop transmission of the signal by the signal emitter. The shutoff circuit is designed to stop transmission of the signal only after the air line has been depressurized and the reset button(s) is depressed.

Abstract: A wireless system and method for locating the position of a movable signal emitter located inside or adjacent to a structure includes establishing at least three base station sites at known locations around the structure. The signal emitter then transmits an omni-directional, low frequency, RF signal that is received at the base station sites. Phase information is measured at each base station site and communicated to a central processing site. At the central processing site, relative phase delays are used to geometrically calculate the position of the signal emitter.

Abstract: A geolocation system for locating a cellular phone in a service area includes an auxiliary receive channel incorporated into the cellular phone. A plurality of transmitters are mutually dispersed at known locations to transmit low frequency beacon signals into the service area. Each beacon signal includes an identifying characteristic that can be used to identify the particular transmitter the signal emanated from. The low frequency of the signal prevents urban features within the service area from acting as signal waveguides and altering the path of the signal. When the user dials a predetermined number such as “911”, the auxiliary receive channel is activated to receive the transmission signals and extract phase related information and the identifying characteristic from each signal. The extracted information is then transmitted to a base station using the cellular phone's normal communication link where the information is processed to determine the location of the cellular phone.

Abstract: A passive navigation system for an airborne platform includes an on-board computer having a database that contains preprogrammed information regarding pre-existing ground-based signal emitters (e.g. cell-phone, television and radio broadcast transmitters). For each emitter, the database includes the geolocation of the emitter and identifying signal characteristic(s) of each emitter's signal such as frequency, bandwidth and strength. An antenna array and digital receiver cooperate with the computer on the platform to passively receive signals from the emitters and determine a direction of arrival (DOA) for selected signals. The computer also extracts identifying signal characteristic(s) from selected received signals and matches them against the database information to ascertain the geolocation of the emitter that corresponds to the received signal. The platform location is then calculated from the DOA(s) and emitter geolocations using a triangulation-type algorithm.

Abstract: A system for tracking a moveable object such as a soldier in an urban environment includes a receiver that is positioned on the movable object and a plurality of signal transmitters. The transmitters are mutually dispersed at known locations within the urban environment and each transmitter is configured to generate a low frequency electromagnetic signal capable of penetrating into buildings in the urban environment. At the receiver, phase related information and the receiver location information are extracted from received signals and used to determine the location of the receiver. Phase related ambiguities can be eliminated by a processor to find the real receiver position using an algorithm such as the maximum likelihood method (MLM) algorithm. Once the real receiver position is calculated, it can be transmitted to a central location using a low probability of intercept (LPI) waveform to prevent hostile parties from intercepting the location of the soldier.

Abstract: A system and method for detecting a target object through foliage includes a transmitter for generating a low-frequency electromagnetic signal. The signal is directed toward a potential target object for reflection from the potential target object. The system further includes a plurality of mutually dispersed sensors for receiving the reflected signal from the target object. A mechanism is provided to determine the relative locations of the sensors. Signal information from the received signals is sent to a central processor. The central processor inputs the signal information into a beamformer algorithm such as the Maximum Likelihood Method (MLM) to reduce sidelobe ambiguities and resolve the true location of the target from the signal information.

Abstract: A system for tracking a moveable object such as a soldier in an urban environment includes a receiver that is positioned on the movable object and a plurality of signal transmitters. The transmitters are mutually dispersed at known locations within the urban environment and each transmitter is configured to generate a low frequency electromagnetic signal capable of penetrating into buildings in the urban environment. At the receiver, phase related information and the receiver location information are extracted from received signals and used to determine the location of the receiver. Phase related ambiguities can be eliminated by a processor to find the real receiver position using an algorithm such as the maximum likelihood method (MLM) algorithm. Once the real receiver position is calculated, it can be transmitted to a central location using a low probability of intercept (LPI) waveform to prevent hostile parties from intercepting the location of the soldier.

Abstract: An airborne radar antenna system for detecting a target in a volume includes a tethered aerostat and an antenna that is supported above ground by the aerostat. The aerostat-based antenna is used for transmitting and receiving a radar beam into the volume to detect the target. Additionally, the system includes a ground-based transmitter that generates a beacon signal which monitors the antenna configuration at the aerostat. A computer then evaluates the beacon signal to create an error signal which is used to maintain a predetermined configuration for the antenna. The system also includes mechanisms for orienting the radar beam along preselected beam paths between the antenna and the volume.

Abstract: An airborne radar antenna system for detecting a target in a volume includes a tethered aerostat and an antenna that is supported above ground by the aerostat. The aerostat-based antenna is used for transmitting and receiving a radar beam into the volume to detect the target. Additionally, the system includes a ground-based transmitter that generates a beacon signal which monitors the antenna configuration at the aerostat. A computer then evaluates the beacon signal to create an error signal which is used to maintain a predetermined configuration for the antenna. The system also includes mechanisms for orienting the radar beam along preselected beam paths between the antenna and the volume.

Abstract: A device for activating a signal emitter for use in a firefighter locator system operates in conjunction with the firefighter's self-contained breathing apparatus (SCBA). The activation device includes a pressure sensor to monitor pressure on an air line that delivers air from the SCBA air tank to the SCBA air regulator. When the firefighter opens the SCBA air tank valve, pressure is sensed in the air line and the emitter is activated to transmit a signal. The signal is received by base stations that then use the signal to locate/track the signal emitter. Preferably, the activating system also includes a user operated reset button(s) and a shutoff circuit to allow the user to stop transmission of the signal by the signal emitter. The shutoff circuit is designed to stop transmission of the signal only after the air line has been depressurized and the reset button(s) is depressed.

Abstract: A system and method for identifying the position of an airborne platform on a flight path includes at least three radar transceivers that are directed along respective beam paths to generate return signals. Each of the return signals respectively indicate a speed and a direction of the platform relative to points on the surface of the earth. A computer uses the return signal to establish a ground speed, an altitude and a direction of flight for the platform. This information is then used to identify the position of the platform on its flight path. Additionally, the system can include a last known position, or a site-specific radar clutter model, to establish a start point for the platform. The computer can then calculate the position of the platform relative to the start point.

Abstract: A system and method for identifying the position of an airborne platform on a flight path includes at least three radar transceivers that are directed along respective beam paths to generate return signals. Each of the return signals respectively indicate a speed and a direction of the platform relative to points on the surface of the earth. A computer uses the return signal to establish a ground speed, an altitude and a direction of flight for the platform. This information is then used to identify the position of the platform on its flight path. Additionally, the system can include a last known position, or a site-specific radar clutter model, to establish a start point for the platform. The computer can then calculate the position of the platform relative to the start point.