A proximity measuring apparatus (70) comprises an interrogator (80) for generating an interrogation signal encoded with a reference signature code comprising concatenated codes and emitting it as interrogating radiation. It also incorporates a transponder (90) for receiving the interrogating radiation, demodulating it to extract its signature code and then remodulating it after a delay period to provide a signal for reemission as return radiation therefrom. The interrogator (80) receives return radiation at its antenna (260) and demodulates it to extract its signature code and then correlates the code with the reference code to determine mutual correlation thereof. The interrogator (80) incorporates a computer (290) for controlling a scan direction of the antenna (260) and for measuring time delay between emission of the interrogating radiation therefrom and receipt of corresponding return radiation. The computer (290) computes distance and relative bearing of a transponder (90) providing the return radiation from the scan direction and the time delay. The apparatus (70) may be used for improving road vehicle safety.

Proximity measuring apparatus

A method and system for wireless intrusion detection, prevention and security management. The method and system provides autonomous wireless intrusion detection and prevention, with minimal or no operator intervention. The method and system integrates a physical layer (e.g., OSI layer 1) a smart wireless radio frequency (RF) antenna subsystem with a data-link layer (e.g., OSI layer 2) wireless security system management platform.

Method and system for wireless intrusion detection, prevention and security management

A system and method for measuring current velocities using coded-pulse broadband acoustic signals. Autocorrelation of two phase coded pulses which are in the water during a single transmission cycle is used to calculate a Doppler frequency. The effective result is current profilers having improved profiling range and spatio-temporal resolution.

Broadband acoustic doppler current profiler

In recent years an abundance of technical papers and books have been written on several topics of radar signal processing. The detection of radar targets against ground and sea clutter is a problem of great interest in the radar community. The fusion of signals from different radar to improve detection performance is another relevant topic of research and application. These are two of several topics that have been extensively described in the technical literature. Needless to say that the consultation of technical references plays a key role in the daily work of researchers and engineers involved in the radar field. We collected almost 700 references in a single document to facilitate our work and the work of other colleagues of the radar community. The collection of references is by no means exhaustive; the period of screening mainly covers the last two decades.

Selected list of references on radar signal processing

A pulse driver (16) modulates the output of an RF oscillator (12) that is fed through a bi-directional RF quadrature network (18) to an antenna (20). After return from the target, the received signal comes through the antenna (20) and then through bi-directional RF quadrature network (18). The dual outputs of the bi-directional RF quadrature network (18)go to an in-phase peak-to-peak de tector (26) and a quadrature peak-to-peak detector (28), then to dual high-pass filters (30, 31) and dual amplifiers (32, 33) before arriving at a baseband quadrature network (36) that feeds into an SSB matrix (42) to yield the upper sideband an the lower sideband.

Ssb pulse doppler sensor and active reflector system

A CW radar transmitter is simultaneously frequency modulated with a sinusal wave and phase-modulated with a pseudorandom binary code. Both the frequency of the FM signal and the bits and bit duration in the binary code can be varied to change the resolution and range of the system.

Continuous wave correlation radar system

Interference between radar systems is eliminated by using shaped pulses. In one embodiment, the pulse has a cosine shape, in another a cos 2 shape and in a third embodiment a cos n shape. In yet another embodiment, a single sideband shaped pulse is employed.

Radar interference reduction

: The performance of moving target indication (MTI) systems for combat surveillance radars depends to a large extent on the clutter spectrum, which is especially important when the radar attempts to detect slowly moving ground targets. This spectrum has long been assumed to be Gaussian shaped. However, MTI system performance predicted by this assumption was not achieved in practice. This report describes the results of an investigation conducted to determine the performance to be expected from an MTI system. The approach used was to measure the clutter rejection ratios afforded by various high-pass filters. The signal was taken from the boxcar demodulator of an X-band radar observing different clutter targets under varying wind conditions. Clutter rejection ratios of 10 to 40 db were measured. These results were then used to obtain a theoretical expression for the clutter power spectrum. This expression differs from the usual Gaussian assumption. Some credence is given to the results by a direct spectral analysis performed on a clutter signal. Two methods of filtering clutter signals which will result in acceptable MTI performance are suggested in this report. The results of this investigation are significant in that they have led to establishing criteria for a better MTI system design.

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Clutter attenuation analysis

Interference between two or more radar systems operating on the same freqcy is eliminated by synchronizing the rotation of the scanning antennas. In another embodiment, each transmitter is blanked if the corresponding receiver detects an interfering signal from the other transmitter. In yet another embodiment, the transmitter pulses are not blanked but merely delayed, if a pulse is received from the interfering system.

Methods and apparatus for eliminating interference in radar systems

A dual frequency moving target radar system having a lower frequency chan which provides relatively good moving target detection in the presence of such obstacles as foliage and precipitation and a higher frequency channel which provides accurate location of targets wherein the Doppler signals from the two channels are correlated to provide suitable target identification which target and clutter are present in the same resolution cell The Doppler frequency is processed to distinguish the moving target from other returns Electroacoustic transducers can be used in either of said channels to aid in target identification

William Fishbein

Papers

Continuous wave correlation radar system

Radar interference reduction

Clutter attenuation analysis

Methods and apparatus for eliminating interference in radar systems

Dual frequency Doppler radar