A near object detection (NOD) system includes a plurality of sensors, each of the sensors for providing detection coverage in a predetermined coverage zone and each of the sensors including a transmit antenna for transmitting a first RF signal, a receive antenna for receiving a second RF signal and means for sharing information between each of the plurality of sensors in the NOD system.

Near object detection system

A continuous wave Doppler radar system having a transmitter module and a receiver module is provided for automotive vehicles. Each module includes an antenna system, including a horn, a lens, and a waveguide system, which is attached to a monolithic microwave integrated circuit (MMIC) chip that provides all necessary electronic functions. Each MMIC chip may be attached to a metal base heat sink, which may be conveniently connected to a base plate heat sink that holds the entire radar assembly. The transmitter module includes a voltage controlled oscillator (VCO) that generates a VCO frequency signal which is amplified and switched sequentially to three multiplier chains for transmission in three different directions. Each transmit signal is taken off the MMIC chip by a dielectric waveguide and directed to the antenna system. The receiver module includes three receivers that are selected sequentially to provide a beam azimuth scanning function. A reference local oscillator is provided at the VCO frequency by electromagnetic radiative coupling from the VCO of the transmitter module. Information on the location and relative speed of a radar target are obtained by comparing the frequency of the signal reflected by the target with the frequency of the signal radiated by the transmitter module. Quadrature mixers are used for each receiver channel to output low frequency data signals containing amplitude and phase information on the received reflected signal. Radar directional discrimination is achieved by sequential selection of the mixer output signals.

Doppler radar system for automotive vehicles

Two novel image processing techniques have been developed to refocus a moving target image from its smeared response in the synthetic aperture radar (SAR) image which is focused on the stationary ground. Both approaches may be implemented with efficient fast Fourier transform (FFT) routines to process the Fourier spatial spectrum of the image data. The first approach utilizes a matched target filter that is derived from the signal history along the range-Doppler migration path mapped onto the SAR image from the moving target trajectory in real space. The coherent spatial filter is specified by the apparent target range in the image and the magnitude of the relative target-to-radar velocity. The second approach eliminates the range-dependence by reconstructing the moving target image from a spectral function that is obtained from the SAR image data spectrum via a spatial frequency coordinate transformation.

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Theory of synthetic aperture radar imaging of a moving target

A relatively narrow beam of either RF or optical electromagnetic radiation is scanned over a relatively wide azimuthal range. The return signal is processed to detect the range and velocity of each point of reflection. Individual targets are identified by clustering analysis (102) and are tracked (106) in a Cartesian coordinate system using a Kalman filter. The threat to the vehicle for a given target is assessed (116) from estimates of the relative distance, velocity, and size of each target, and one or more vehicular devices are controlled (120) responsive to the assessment of threat so as to enhance the safety of the vehicle occupant. In a preferred embodiment, a quantized linear frequency modulated continuous wave RF signal is transmitted from and received by a multi-beam antenna having an azimuthal range of at least +/- 100 degrees and an individual beam width of approximately 10 degrees.

Predictive collision sensing system

A radar detection process includes computing a derivative of an FFT output signal to detect an object within a specified detection zone. In one embodiment, a zero crossing in the second derivative of the FFT output signal indicates the presence of an object. The range of the object is determined as a function of the frequency at which the zero crossing occurs. Also described is a detection table containing indicators of the presence or absence of an object within a respective radar beam and processing cycle. At least two such indicators are combined in order to detect the presence of an object within the detection zone.

Radar detection method and apparatus

An FM/CW radar system is disclosed for determining a safe stopping distance between a moving vehicle and a potential obstacle. The radar signal is modulated linearly over several slopes. A microstrip phased array transmit/receive antenna is also disclosed having a hybrid tap, corporate feed structure. Signals from the antenna are amplified and filtered, and passed through an analog to digital converter to a signal processor, which performs a Fast Fourier Transform on the signals to convert them from time domain data to frequency domain data. The frequency domain data is then used to solve target range and doppler equations, determine safe stopping distances, and sound or display alarms if the safe stopping distance has been violated. A sensitivity control adjusts for road conditions or operator reaction time variations.

Safe stopping distance detector, antenna and method

Recently, considerable interest has been expressed in the use of radar to detect underground targets both small (e.g., antipersonnel mines) and large (e.g., buried vehicles). Particular interest has been directed at airborne SAR for this purpose. Several important issues requiring study include the scattering signature of objects buried in soil media, the attenuation and scattering of radar energy in inhomogeneous soils, and the impact of clutter (and particularly the impact of surface clutter layover) on subsurface target detection and recognition. To address these issues, a radar ground penetration experiment was conducted in the desert near Yuma, AZ from June 4 to 15, 1993. In this experiment a number of large and small targets of various shapes were buried at depths up to 3 m, and data was collected using several air- and ground-based radars using both real and synthetic aperture data processing. The variety of radars available covered the range from 20 to 1500 MHz. The data collected was calibrated with sufficient accuracy to permit the measurement of in situ radar signatures, allowing the calculation of ground penetration losses. Data from this test have been analyzed to develop a phenomenological understanding of soil penetration losses and clutter backscattering, and to investigate the characteristic signatures of specific buried targets. These data are compared to laboratory soil measurements and modeling studies. This paper will describe the experiment, sensors, sample radar measurements and some of the results of the data analysis.

Results of the June 1993 Yuma ground penetration experiment

Considerable interest has been expressed in the use of radar to detect underground targets both small (e.g., antipersonnel mines) and large (e.g., buried vehicles). Particular interest has been directed at airborne SAR for this purpose. Several important issues requiring study include the scattering signature of objects buried in soil media, the attenuation and scattering of radar energy in inhomogeneous soils, and the impact of clutter (and particularly the impact of surface clutter layover) on subsurface target detection and recognition. To address these issues, a radar ground penetration experiment was conducted in the desert near Yuma, AZ from June 4-15, 1993. In this experiment a number of large and small targets of various shapes were buried at depths up to 3 m, and data was collected using several air- and ground-based radars using both real and synthetic aperture data processing. The variety of radars available covered the range from 20 to 1500 MHz. The data collected was calibrated with sufficient accuracy to permit the measurement of in situ radar signatures, allowing the calculation of ground penetration losses. Data from this test have been analyzed to develop a phenomenological understanding of soil penetration losses and clutter backscattering, and to investigate the characteristic signatures of specific buried targets. These data are compared to laboratory soil measurements and modeling studies. This paper describe the results of the modeling and SAR data analysis.

Results on ground penetration SAR phenomenology from June 1993 Yuma experiment

A small minefield was deployed in the desert near Yuma Arizona in June 1993. Radar data of this minefield was collected by ground based and airborne radar sensors. The mine field consists of M-20 metal and M-80 plastic anti-armor mines and Valmara-69 anti-personnel mines. The mines were deployed on the surface and buried at three different depths. Images and analysis of the minefield, which are derived from data collected by the SRI FOLPEN II synthetic aperture radar, are presented here. The minefield was imaged over three bands form 100 to 500 MHz and at various depression angles with this radar sensor. The image analysis is compared to the modeling results of surface and buried mine like objects. We also show the results of a new Radio Frequency Interference (RH) rejection algorithm and the imagequality improvement we achieved. 1 . INTRODUCTION A ground penetration experiment was conducted in June of 1993 near Yuma Arizona[1]. In this experiment, a large number of targets of various shapes and sizes were both buried and placed on thesurface. Among these objects were tactical targets like mines and 5-ton trucks, and canonical targets like

Detection of surface and buried mines with an UHF airborne SAR

Many different sensors and systems, from sonar to machine vision, have been installed on ground vehicles and automobiles. This paper describes the use of radar to improve driving safety and convenience. Radars are valuable sensors for all weather operation and experiments with automotive radar sensors have been conducted for over 40 years. This paper shows the advantages and disadvantages of applying microwave and millimeter wave radar to obstacle detection and collision avoidance in a roadway environment. The performance differences between avoidance and warning sensors are discussed and a problem set is devised for a typical forward-looking collision warning application. Various radar systems have been applied to this problem that include pulse and continuous wave transceivers. These system types are evaluated as to their suitability as a collision warning sensor. The various possible solutions are reduced to a small number of candidate radar types, and one such radar was chosen for full scale development. A low cost frequency modulated/continuous wave radar system was developed for automotive collision warning. The radar is attached to the sun visor inside the vehicle, and has been in operation for over four years. The radar monitors the range and range-rate of other vehicles and obstacles, and warns the driver when it perceives that a dangerous situation is developing. A system description and measured data is presented that shows how the 24.075 to 24.175 GHz band can be used for an adequate early warning system.

Theodore O. Grosch

Papers

Safe stopping distance detector, antenna and method

Results of the June 1993 Yuma ground penetration experiment

Results on ground penetration SAR phenomenology from June 1993 Yuma experiment

Detection of surface and buried mines with an UHF airborne SAR

Radar sensors for automotive collision warning and avoidance