Abstract:
An improved vehicle radar system and control aids the vehicle driver during both parking and back-up maneuvers. The radar system is equipped with both long range and short range radar detection antennas, an RF switch for selecting the active antenna, and a range bin having a depth that is adjustable “on the fly”. The back-up aid function is provided by activating the RF switch to select the long range antenna and setting the range bin to a relatively large depth to cover the long range in a short time. The parking aid function is provided by activating the RF switch to select the short range antenna, and setting the range bin to a relatively short depth to achieve high close range accuracy.

Description:
TECHNICAL FIELD 
     This invention relates to automotive radar systems of the type in which the detection range is divided into multiple contiguous range bins, and more particularly to a radar control that provides both back-up aid and parking aid functions. 
     BACKGROUND OF THE INVENTION 
     Object detection and ranging systems have been applied to motor vehicles for aiding the driver when the vehicle is being operated in reverse. A first type of system, generally referred as a back-up aid, is designed to aid the driver by detecting foreign or unexpected objects in the path of the vehicle; in this type of system, the detection range must be relatively extensive, but the ranging accuracy can be relatively coarse. A second type of system, generally referred to as a parking aid, is designed to aid the driver by indicating how close the rear bumper is to an object such as another vehicle during parking maneuvers; in this type of system, the detection range can be relatively shallow but must also be relatively wide, and the ranging accuracy needs to be relatively fine. Since the design requirements of parking aids and back-Lip aids are so different, it has been considered impossible to provide both functions with a single non-scanning radar sensor. Thus, the current trend is to equip the vehicle with a radar sensor for the back-up aid function, and with a series of lower cost ultrasonic sensors for the parking aid function. However, it would be desirable from the standpoint of both cost and performance to be able to achieve both parking and back-up aid functions with a single radar system. 
     SUMMARY OF THE INVENTION 
     The present invention is directed to an improved vehicle radar system and control for aiding the vehicle driver during both parking and back-up maneuvers. According to the invention, the radar system is equipped with both long range and short range radar detection antennas, an RF switch for selecting the active antenna, and a range bin having a depth that is adjustable “on the fly”. The back-up aid function is provided by activating the RF switch to select the long range antenna and setting the range bin to a relatively large depth to cover the long range in a short time. The parking aid function is provided by activating the RF switch to select the short range antenna, and setting the range bin to a relatively short depth to achieve high close range accuracy. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 schematically depicts a motor vehicle and radar detection patterns for achieving back-up and parking aid functions according to this invention. 
     FIG. 2 is a block diagram of a radar system that develops and utilizes radar detection patterns as depicted in FIG. 1 for providing back-up and parking aid functions according to this invention. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring to the drawings, and more particularly to FIG. 1, the reference numeral  10  generally designates a radar system installed in a motor vehicle  12  to perform both parking and back-up aids for the vehicle driver. The system  10  illuminates or radiates radar energy to the rear of the vehicle  12  and receives radar energy returned from objects in a detection area. As explained below in detail, the system  10  includes first and second antennas (also referred to herein as long and short range antennas) for receiving the returned radar energy, each such antenna being designed to receive radar energy in particular pattern within the illuminated region. The receive antennas receive radar energy in characteristic patterns that in the usual case are laterally symmetrical about the central axis  14 . The first or long range antenna is sensitive to radar energy in a long range pattern as generally depicted by the reference numeral  16  for use in performing the back-Lip aid function, whereas the second or short range antenna is sensitive to radar energy in a short range pattern as generally depicted by the reference numeral  18  for use in performing the parking aid function. In a typical mechanization, for example, the pattern  16  supports a detection range of 0.0-6.0 meters and the pattern  18  supports a detection range of 0.0-1.4 meters, the pattern  18  having much wider coverage in the immediate vicinity of tile vehicle  12 . 
     FIG. 2 depicts tile radar system  10  in block diagram form. The transmitting antenna for illuminating the area to the rear of the vehicle  12  is designated by the reference numeral  20 , and the long range and short range receiving antennas are designated by the reference numerals  22  and  24 , respectively. In general, tile detection range of each of tile antennas  22 ,  24  is subdivided into a number of contiguous regions of increasing range relative to the vehicle  12 , and a range bin of a given depth is scanned in range to cover the respective regions. According to this invention, however, the range bin used to scan the detection region of the long range antenna  22  is deeper than the range bin used to scan the detection region of the short range antenna  24 . In this way, both patterns may be scanned in a similar amount of time, the relatively deep range bin used to scan detection region of long range antenna  22  provides acceptable ranging accuracy for the back-up aid function, and the relatively shallow range bill used to scan the detection region of short range antenna  24  provides acceptable ranging accuracy for the parking aid function. For example, the long range antenna  22  may be scanned with a 20 centimeter range bin to limit back-LIP aid ranging error to 10 centimeters or less, and the short range antenna  24  may be scanned with a 10 centimeter range bin to limit parking aid ranging error to 5 centimeters or less. 
     Referring specifically to FIG. 2, the transmitter antenna  20  is coupled to a transmitter circuit  26  including a code clock  28 , a code generator  30 , a data generator  32 , an Exclusive-OR gate  34 , a Local Oscillator (LO)  35 , a 0° Power Divider  36  and a controlled phase modulator circuit (ΔØ)  38 . Briefly, code generator  30 , under control of code clock  28 , generates a maximal length pseudo-noise ranging code on line  39 , which is mixed with the output of data generator  32  by Exclusive-OR gate  34 . The output of Local Oscillator  35 , split by Power Divider  36 , is applied as an input to phase modulator  38 , which modulates the oscillator signal in accordance with the output of Exclusive-OR gate  34 . 
     The receive antennas  22 ,  24  are coupled to a radio frequency switch (RF-SW)  40  that couples the signal output of a selected receiver antenna to a receiver circuit  42  that demodulates and integrates a portion of the received signal corresponding to a selected range bin to determine the presence of any objects therein. The Output of RF-SW  40  is initially coupled to a low noise amplifier (LNA)  44 , and then applied as an input to the controlled phase modulator (ΔØ)  46 , which modulates the received signal with the output of code generator  30 , as variably delayed by programmable delay unit  48 . The delay imposed by delay unit  48  corresponds to the time of flight delay associated with an object to be detected in a selected range bin, and if the received signal matches that time delay, the output of phase modulator  46  will contain the data stream of data generator  32 , modulated on a carrier wave at the frequency of the Local Oscillator  35 . The Output of phase modulator  46  is then split by 0° Power Divider  50 , and applied to the I and Q demodulators  52  and  54 , which reproduce the data on lines  56  and  58 , through the operation of 90° Power Divider  60 , which splits and phase shifts the Output of Local Oscillator  35 . The data signals on lines  56 ,  58  are then amplified and band-pass filtered by blocks  62 ,  64  to extract the fundamental frequency of the data stream, envelope detected by diodes  66 ,  68 , and then summed at summing junction  70  to form a DC signal on line  72  corresponding to the amplitude of radar illumination reflected from one or more objects in the selected range bin. The signal on line  72  is then integrated by integrator  74 , and compared to a threshold level (THR) by comparator  76  to determine if there is an object in the selected range bin. A l:n multiplexer  78  directs the comparator Output to a suitable register for further processing. 
     In addition to the above-described elements, the radar system  10  includes a sequencer  80  coupled to the delay unit  48 , an integrator reset switch  82 , the code clock  28 , multiplexer  78  and RF-SW  40 . The sequencer  80  is micro-processor based, and controls the operation of such elements to select an appropriate range bin and to scan such range bin to detect the presence and range of one or more objects in the desired detection region. In general, process carried out by sequencer  80  involves closing reset switch  82 , adjusting the code signal delay of delay unit  48  to change the range bin position, starting a dwell timer, and re-opening the reset switch  82  to permit integrator  74  to integrate the signal on line  72 . When the dwell timer reaches the retrieved dwell time, the multiplexer  78  is controlled to save the output of comparator  76 , and the process repeated until the entire detection region of the received signal has been scanned. See, for example, the U.S. Pat. No. 5,731,781, issued on Mar. 24, 1998, and incorporated herein by reference. 
     In implementing the present invention, the sequencer  80  additionally controls RF-SW  40  to select the long or short range antenna  22 ,  24 , and controls the pseudo-noise ranging code to select the corresponding range bin. In the illustrated embodiment, the output frequency of code clock  28  is designed to produce a 10 centimeter range bin for the parking aid function, and the range bin is doubled to 20 centimeters for the back-up aid function by passing the output of code clock  28  through the divide-by-two circuit  82  before applying it to code generator  30 . To this end, the sequencer  80  controls the operation of switch  84  via line  86  to select the appropriate range bin size. Alternatively, of course, the code clock  28  or code generator  30  may be programmable to enable “on-the-fly” selection of the range bin size by sequencer  80 . In a typical implementation, the parking and back-up aids are enabled whenever the reverse transmission range of the vehicle  12  is selected, and sequencer  80  is preferably operated to periodically switch between the back-up aid and parking aid modes of operation so that both functions are provided at essentially the same time. Alternatively, the functionality may be selected based on the reverse speed of the vehicle, with the parking aid being activated at very low speeds, and the back-up aid being activated at higher speeds. In any event, the single radar system  10  achieves both back-up aid and parking aid functions, contributing to a cost effective and high performance configuration. 
     While described in reference to the illustrated embodiments, it is expected that various modifications in addition to those mentioned above will occur to those skilled in the art. For example, two or more systems may be applied to a vehicle if desired to extend the overall lateral detection range. Additionally, it will be understood that the various system parameters disclosed herein are exemplary, and may be adjusted as required to satisfy the requirements of a given installation. Accordingly, it will be understood that the scope of this invention is not limited to the illustrated embodiments and that systems and methods incorporating such modifications may fall within the scope of this invention, which is defined by the appended claims.