Communications: directive radio wave systems and devices (e.g. – Directive – Beacon or receiver
Patent
1997-06-17
1998-09-08
Tarcza, Thomas H.
Communications: directive radio wave systems and devices (e.g.,
Directive
Beacon or receiver
342 22, 342 94, 342126, 342137, G01S 1300, G01S 1308, G01S 124
Patent
active
058051104
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to high resolution, short range radar systems, and more particularly to ultra-wide band radars for imaging short range fields.
2. Description of Related Art
Short range finding applications in the prior art have typically been implemented using either ultrasound technology, or frequency modulated continuous wave (FMCW) radar. For instance, range finding used in fluid level sensors for large tanks in the prior art have involved FMCW radar level sensing. However, this technology, which relies on measuring changes in the beat frequencies detected for transmitted and received waves, requires very linear voltage controlled oscillators at microwave frequencies. This technology is very tough to implement with the precision desired in level sensing technology. Thus, prior art FMCW radars have been limited in resolution to several inches and are relatively expensive.
Another technology used in level sensing is ultrasound. However, ultrasound technology suffers a number of disadvantages. In particular, for fluid level sensors, the ultrasound may erroneously pick up a level of foam, rather than a level of actual liquid. Also, it does not penetrate vapors, like gasoline or steam, which may be trapped in a tank. Furthermore, any soil on the sensors will prevent its operation. Also, ultrasound is inherently difficult to use for precision measurements, because the speed of sound varies with temperature and humidity by as much as 10% in normal operating conditions.
Accordingly, it is desirable to provide a range finding system, or imaging system which operates over a short range, has low cost, and provides excellent accuracy.
SUMMARY OF THE INVENTION
The present invention provides a radar range finder and hidden object locator based on ultra-wide band radar with a high resolution swept range gate. The device generates an equivalent time amplitude scan with a typical range of 1 inch to 20 feet, and an analog range resolution as limited by a jitter of on the order of 0.01 inches. A differential sampling receiver is employed to effectively eliminate ringing and other aberrations induced in the receiver by the near proximity of the transmit antenna, so a background subtraction is not needed, simplifying the circuitry while improving performance. Uses of the invention include a replacement of ultrasound devices for fluid level sensing, automotive radar, such as cruise control and parking assistance. Also, this technology can be used when positioned over a highway lane to collect vehicle count and speed data for traffic control. Other uses include active suspension systems sensing, occupant position sensing, and other applications where the precise range to an object needs to be determined. The radar range finder makes an excellent fluid and solids level sensor for petroleum storage tanks, industrial mixing vats, and grain silos. Its amplitude display also indicates the presence or absence of objects located behind barriers, such as studs behind walls and rebar in concrete. The output can also be correlated with similar units at different spatial locations to provide synthetic beam forming for narrow beam applications and for imaging.
The invention can be characterized as an apparatus for detecting characteristics of objects within a field. The apparatus comprises a transmitter which transmits the sequence of electromagnetic pulses in response to a transmit timing signal. A receiver samples echoes of the sequence of electromagnetic pulses which are generated by objects within the field. The receiver samples these echoes using a differential sampling receiver having a transformerless differential input with high common mode rejection which reduces ground currents coupled from the transmit pulse through the apparatus structure.
According to one aspect of the invention, the receiver includes waveguide cavities for the transmit and receive antennas. The antennas comprise AC coupled monopoles with resistive loading formed within the respective ca
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Phan Dao L.
Sartorio Henry P.
Tarcza Thomas H.
The Regents of the University of California
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