Communications: directive radio wave systems and devices (e.g. – Return signal controls external device – Radar mounted on and controls land vehicle
Reexamination Certificate
2002-03-22
2003-07-01
Tarcza, Thomas H. (Department: 3662)
Communications: directive radio wave systems and devices (e.g.,
Return signal controls external device
Radar mounted on and controls land vehicle
C342S071000, C342S072000, C342S02500R
Reexamination Certificate
active
06587072
ABSTRACT:
FIELD OF INVENTION
This invention relates to a short-range pulse-compression radar system particularly suitable for fabrication as an integrated circuit.
BACKGROUND OF INVENTION
A need exists for a short-range radar system, which, for example, is suitable for automotive and other commercial applications. Such a system would be enabled to sense the proximity of other vehicles and objects, moving or stationary, within a range radius of about 0.15 meters to 30 meters or beyond. Radar systems having automotive application have been proposed in the prior art, including systems utilizing radar for automatic braking, as well as warning the operator of the vehicle of an impending danger or obstruction such as an animal or person in the roadway.
In addition to object range detection, it is also useful to be able to distinguish or resolve the distance between two objects in very close proximity (e.g. when they are approximately 15 centimeters apart). An intelligent radar detection system comprises a number (one or more) of sensors that operate as a transceiver for electromagnetic energy. The sensors typically transmit and receive electromagnetic energy of a defined frequency and power via an antenna over a defined spatial area. In turn, the system receives echo signals from partial reflections of any illuminated objects in that area. The ability of the sensor to resolve two or more objects closely situated in the illuminated area leads to the descriptive name of high-resolution radar (HRR).
The prior art also refers to high range resolution mono-pulse radar systems which are designated (HRRM). See, for example, a text entitled, “Radar Handbook”, Second Edition, by Merrill Skolnik, published by McGraw Hill, Inc. (1990). This text gives descriptions of radar systems, including high-resolution systems. As one can ascertain, there is a large potential market for automotive radars as well as for other commercial applications. Such applications include, but are not limited to, automatic door openers, sanitary facilities, electronic boundary detectors or fences, electronic camera focusing, navigation devices, parking aid sensors, and a host of other potential uses. However, in order to create a system for such markets, a technical solution must be provided that is not only capable of operating with the required degree of performance, but also offers a potential route to lower cost sensors. The price reduction should be able to take advantage of economies of scale and other established high volume manufacturing techniques. In addition, the sensor architecture should be sufficiently flexible to offer multiple operating modes to enable varying application and custom requirements depending upon the intended end use.
The prior art was cognizant of the need for low cost, high-resolution radars. Reference is made to U.S. Pat. No. 6,067,040 entitled, “Low Cost High Resolution Radar for Commercial and Industrial Applications”, issued on May 23, 2000 to K. V. Puglia. The patent describes a low cost, high-resolution radar based detection system, which has a pulse repetition frequency generator connected to first and second narrow pulse modulators. The system employs a transmit channel which is connected to the first narrow pulse modulator and emits pulse modulator carrier based transmit signals having a prescribed frequency and a prescribed duration. The receive channel is connected to the second narrow pulse modulator. There is a time delay circuit which delays the output of the second pulse modulator to the receive channel and a mixer which mixes a portion of one of the pulse modulated carrier based transmit signals reflected from an object with the output of the second narrow pulse modulator.
PCT application entitled, “Sensor for Measuring a Distance from an Object” No. WO 00/43801 having a priority date of Jan. 20, 1999 and filed for Martin Reiche describes a sensor for measuring the distance from an object. The apparatus includes an oscillator which generates a carrier signal. A first modulation switch modulates pulses on a carrier signal and generates a first pulse signal. The first pulse signal is emitted in the direction of the object. The first pulse signal is reflected by the object and delayed by a propagation time. A power divider positioned between the oscillator and the first modulation switch transmits the carrier signal to a second modulation switch. The second modulation switch modulates the pulses on to the carrier signal and generates a second pulse signal that is delayed by a variable delay. One compares the delay of the second pulse signal with the propagation time of the first pulse signal to detect the propagation time and determine the distance to the object.
An aspect of the invention is to increase the pass-band transmission loss of the modulation switches by providing for a third modulation switch which is positioned between the oscillator and the power divider. As one can see from the above-noted techniques, the typical operating scenario presented in the above systems are based on a combination of discrete circuit components combined with distributed transmission line elements on a soft substrate. These prior art approaches can lead to a combination of manufacturing tolerance issues and operating scenarios that compromise the performance of the sensor. It is understood that the design and assembly of the sensor based on discrete components leads to a relatively large device. The functional operation of the sensors is restricted for both size and cross constraints as each additional circuit block is relatively expensive to add. The use of distributed transmission line circuitry is a common technique for the design of high frequency microwave and millimeter circuits, but is based on the fundamental assumption that standing waves are present in the circuit. This assumption no longer holds true under short pulse conditions, and can lead to transient and short-term circuit effects that reduce the operating margin and compromise sensor performance. Lastly, the mid- to long-range operation of the short pulse sensor is not optimum due to two issues. The energy received by the sensor from partial reflection of the detected objects varies as an inversely proportional function of the fourth power of the object's range. As the range increases, the ability of the sensor to detect objects rapidly decreases as a function of the greatly reduced energy incident upon, and reflected from objects. Conventionally, there are two limitations that restrict the amount of energy (power) that may be transmitted by the sensor: the ability to discriminate between two targets (range discrimination) is a function of the pulse-length in pulsed-radar systems, and the chirp or frequency modulation bandwidth in a CW radar system. A longer pulse length increases the amount of energy transmitted by the sensor with a consequent reduction in the ability of the sensor to discriminate between closely located objects. Also, the interval between pulses (or pulse repetition frequency (p.r.f)) may not be reduced indiscriminately to increase the transmitted energy for the need to maintain an unambiguous range measurement. In addition, the sensor is susceptible to in-band interference sources that produce and transmit electromagnetic energy in the same portion of the electromagnetic spectrum as that of the sensor. The forms of the interfering sources include CW or pulsed transmission by other systems, mutual interference from a second sensor or sensor system operating with the same or similar purpose, self-jamming through imperfect isolation between the transmit and receive port antennae, and wide-band thermal noise.
Thus, one can readily understand that these problems increase with such sensor devices that are used in, for example, the automotive industry. For example, hundreds of cars on a single highway may all be generating and receiving signals operative in the same radar range or at similar frequency bands.
In accordance with an aspect of the present invention; a variable length pulse is introduced that increa
Egri Robert
Gresham Robert Ian
Alsomiri Isam
M/A-Com Inc.
Tarcza Thomas H.
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