JP2006317162A - Radar equipment - Google Patents

Abstract

[PROBLEMS] It is possible to automatically minimize radio wave wraparound at low cost without bothering human hands. Furthermore, for example, when the thickness of a bumper changes due to aging, or a bumper with a different material is replaced. It is an object of the present invention to provide a radar apparatus that can minimize the wraparound of radio waves.
A radar apparatus that detects a surrounding object by transmitting and receiving a radar beam through a member disposed in front of an antenna, wherein a transmission unit that transmits a transmission beam modulated at a reference frequency from the antenna; A reception unit that receives a reception beam reflected by the object, and a signal processing unit that calculates a distance to the object based on a time difference between the transmission beam and the reception beam; the signal processing unit further includes a reception beam Based on this, the reference frequency is controlled so that the reflection loss from the member is minimized.
[Selection] Figure 2

Description

  The present invention relates to a radar apparatus for detecting surrounding objects.

  A radar device mounted on a vehicle is installed at a position where it cannot be directly seen from the outside, such as the back side of a bumper. The bumper is made of a material such as a resin that transmits electromagnetic waves. However, depending on the positional relationship between the antenna and the bumper, the radio wave emitted from the transmitting antenna is reflected by the bumper and wraps around the receiving antenna, reducing the detection power. There was a problem that it would end up. In order to reduce the wraparound of the radio wave, a method for manually fine-tuning the fixed position of the radar apparatus has been developed (see, for example, Patent Document 1).

The adjustment method disclosed in Patent Document 1 temporarily fixes the radar device at a predetermined position of the vehicle so as to be finely adjustable, and changes the fixed position of the radar device within a finely adjustable range while operating the radar device. It is. A dummy target is installed in the detection target area of the radar device, and its reflection level is monitored. While changing the relative angle between the antenna and the bumper, the control voltage of the automatic gain control amplifier is taken out and the amplification level of the reflection level is monitored, and the fixed position of the radar device is determined at the position when the amplification level is judged to be the smallest. Determine. As a result, the wraparound of the radio wave due to the reflection of the bumper can be minimized.
JP 2002-71788 A

  However, in the conventional configuration, the fine adjustment work of the fixed position of the radar apparatus becomes complicated and expensive. This is because, in addition to the need to install a dummy target in the detection area, it is necessary for a human to manually fine-tune the fixed position.

  The present invention solves such a conventional problem, and can automatically minimize the reflection loss in the bumper at a low cost without bothering human hands, and further, for example, the thickness of the bumper due to secular change. An object of the present invention is to provide a radar device that can minimize the wraparound of radio waves even when the frequency has changed or when the bumper is replaced with a different material.

  In order to solve the above-described conventional problems, a radar apparatus according to the present invention is a radar apparatus that detects surrounding objects by transmitting and receiving a radar beam through a member disposed in front of an antenna, and modulates at a reference frequency. A transmission unit that transmits the transmitted beam transmitted from the antenna, a reception unit that receives the reception beam reflected by the object, and a signal processing unit that calculates a distance to the object based on a time difference between the transmission beam and the reception beam; The signal processing unit further controls the reference frequency based on the received beam so that the reflection loss from the member is minimized.

  With this configuration, the center frequency of the radar beam can be automatically set to a frequency at which the reflection loss at the bumper is minimized. Therefore, unlike the conventional case where a dummy target is installed in the detection area or when a human performs fine adjustment of the fixed position of the radar device manually, the radio wave is automatically circulated without bothering human hands. In addition, even when the relative position between the radar and the bumper changes due to secular change, it is possible to always minimize the wraparound of radio waves.

  According to the radar apparatus of the present invention, by automatically setting the center frequency of the radar beam to an optimum value, it is possible to easily keep the reflection loss in the bumper of the radar beam at a minimum state. As a result, the power of the transmitted radar beam can be radiated to the outside of the bumper as much as possible to increase the maximum detection distance of the radar device, and the signal-to-noise ratio of the received radar beam can be improved. It is possible to more accurately detect an object existing in the.

  Hereinafter, a radar apparatus according to an embodiment of the present invention will be described with reference to the drawings.

  FIG. 1 is a diagram illustrating a position where a radar apparatus is installed in a vehicle, and is installed on the back side of a bumper at the front of the vehicle. As indicated by the dotted line in the figure, in this case, three radar apparatuses are installed. However, a desired number of radar apparatuses are installed depending on the region to be detected.

  FIG. 2 is a block diagram showing the configuration of one of the radar devices in FIG. 1 as seen from above. Note that the radar apparatus in this embodiment is a pulse system. Here, the distance detection operation of the object by the radar apparatus will be described with reference to the block diagram of FIG.

  The radar apparatus 1 is roughly divided into a transmission unit 2, a reception unit 3, and a signal processing unit 4. First, in the transmission unit 2, a pulse signal for modulation is generated by the pulse generator 5. On the other hand, a high-frequency continuous wave is generated by the oscillator 6 and input to the splitter 7 to be divided for transmission and reception. Next, a pulse signal for modulation and a high-frequency continuous wave are input to the transmission mixer 8, and a high-frequency modulation pulse is generated by a multiplication operation. After being amplified by the transmission power amplifier 9, it is further amplified by the transmission antenna 10 and emitted as a transmission beam, transmitted through the bumper 20 and emitted outside the vehicle.

  If there is any object ahead of the emitted light, the transmission beam is irradiated on the object, and a part of the irradiated transmission beam is reflected and returns to the radar apparatus again. The reception antenna 11 receives this as a reception beam, amplifies it, and further amplifies it by a reception LNA (low noise amplifier) 12. This is input to the reception mixer 13 together with the high-frequency continuous wave generated by the oscillator 6 and divided by the splitter 7, and a baseband signal is output by a multiplication operation in the same manner as the transmission mixer 8. This baseband signal is input to the detector 14 and a demodulated pulse is output. The signal processor 4 can calculate the distance to the object by obtaining the time difference between the modulated pulse and the demodulated pulse.

  The problem here is the reflection loss of the radar beam at the bumper 20. Since the bumper 20 is usually made of resin, it transmits radio waves, but there is a component that reflects without transmitting part of it, and the amount obtained by subtracting such reflection loss from the input radar beam is the bumper 20. Will be emitted outside the vehicle. The less this reflection loss, the more the power of the transmitted radar beam is radiated to the outside of the vehicle, which can contribute to the improvement of the maximum detection distance of the radar device and the signal-to-noise ratio of the received radar beam. An existing object can be detected more accurately.

  The factors that determine the reflection loss in this bumper are the thickness, shape, relative dielectric constant of the bumper 20, the distance between the antenna (transmitting antenna 10 and receiving antenna 11) and the bumper 20, and the frequency of the radar beam. It is closely related. In the present embodiment, the greatest feature is to minimize the reflection loss of the radar beam at the bumper 20 by optimizing the center frequency of the radar beam that can be controlled most easily among these parameters. is there.

  For this purpose, the signal processing unit 4 controls the reference frequency of the oscillator 6 to an optimum value so that the reflection loss from the bumper is minimized based on the received beam. Hereinafter, the operation of the signal processing unit 4 optimizing the reference frequency of the oscillator 6 will be described with reference to the flowchart of FIG.

  First, at step 301, the reference frequency f0 of the oscillator 6, the frequency bandwidth fw to be swept, and the frequency step width Δf are determined. Although fw and Δf are determined based on the specifications of the oscillator to be used, the more accurate the frequency can be optimized as fw is larger and Δf is smaller. f0 is a typical frequency in the oscillator to be used. Alternatively, if the thickness and dielectric constant of the bumper are known, the frequency f obtained by the following equation (2) may be set to f0.

  In general, when a radar beam is incident on a dielectric material such as resin, most of the incident radio wave is transmitted, that is, the reflection is minimized when the thickness of the dielectric material is half of the waveguide wavelength (wavelength in the dielectric material). Become. At this time, when the thickness of the bumper is t, the relative permittivity is εr, the in-tube wavelength of the bumper is λg, the center frequency of the radar beam is f, and the speed of light is c, the following relationship is established.

t = λg / 2 = λ / (2 · √ (εr)) = c / (2 · f · √ (εr)) (1)
When the above equation is modified, equation (2) is obtained.

f = c / (2 · t · √ (εr)) (2)
Next, in step 302, initial setting of parameters is performed. The frequency fmin of the oscillator 6 when taking the amplitude Amin is set to f0−fw / 2 which is an initial value of the frequency f sweeping the frequency f of the oscillator 6, the minimum amplitude Amin of the demodulated pulse due to reflection from the bumper 20 is set to 100, and f0. Set to.

  In step 303, the signal processing unit 4 calculates the demodulation pulse amplitude due to reflection from the bumper 20 when the frequency of the oscillator 6 is f, and stores it in the variable A. Here, since the approximate distance from the antenna to the bumper is known if the mounted vehicle type is determined, the pulse signal delayed by that distance is determined as the reflected wave from the bumper. In step 304, the amplitude A obtained in step 303 is compared with Amin. If A <Amin, the process proceeds to step 305. Otherwise, the process proceeds to step 306.

  In step 305, f is substituted for fmin, and in step 306, the frequency step width Δf is added to f. Next, in step 307, f is compared with f0 + fw / 2 which is the final value of the frequency to be swept. If f> f0 + fw / 2, the process ends; otherwise, the process returns to step 303. By setting fmin obtained by repeating steps 303 to 307 as the oscillator frequency, the reflection loss of the radar beam at the bumper 20 is minimized.

  As described above, according to the present embodiment, by automatically setting the center frequency of the radar beam to an optimum value, the reflection loss in the bumper of the radar beam can be minimized, and the transmitted radar beam can be minimized. Maximum power can be radiated outside the bumper. As a result, the maximum detection distance of the on-vehicle radar can be extended and the signal-to-noise ratio of the received radar beam can be improved, so that a target that exists farther can be detected more accurately.

  In addition, the optimal frequency setting is performed without bothering human hands, unlike when a dummy target is installed in the detection area as in the past or when a human performs manual fine adjustment of the fixed position of the radar device. Since it can be executed automatically, it can contribute to cost reduction.

  Furthermore, there is an advantage that the optimum value setting of the frequency can be executed anytime after installing the radar device and the bumper. As a result, even when the thickness of the bumper has changed due to aging, for example, or when the bumper has been replaced with a different material, it is possible to always minimize the wraparound of the radio wave by setting the optimum value of the frequency as needed. it can. Therefore, it is possible to detect a target that is always farther away more accurately.

  Furthermore, when considering application of the radar apparatus to a plurality of car manufacturers and a plurality of vehicle types, the thickness of the bumper, the relative permittivity, the shape, and the distance between the antenna and the bumper vary depending on the vehicle type. According to the radar apparatus of the present invention, the optimal radar beam frequency setting absorbs the above-described parameter differences for each vehicle type, minimizes the reflection loss in the bumper, and always provides the object by the radar apparatus under the best conditions. Detection can be performed. Thus, mass production of a single product can contribute to cost reduction.

  Although the pulse radar has been described as an example this time, the radar system is not limited to this, and can be applied to any other radar system.

  The radar apparatus according to the present invention has an effect that the reflection loss of the radar beam in the bumper can be easily kept at a minimum state by automatically setting the center frequency of the radar beam to an optimum value. In addition to a radar device that is mounted on the vehicle and detects surrounding obstacles, it is also useful as a detection radar device or the like for finding a person who has left the building through the wall of the building when a disaster occurs.

The figure which shows the installation position in the vehicle of the radar apparatus concerning embodiment of this invention The block diagram which shows the structure of the radar apparatus concerning embodiment of this invention Flowchart showing the flow of operation in which the signal processing unit 4 optimizes the reference frequency of the oscillator 6

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Radar apparatus 2 Transmission part 3 Reception part 4 Signal processing part 5 Pulse generator 6 Oscillator 7 Splitter 8 Transmission mixer 9 Transmission power amplifier 10 Transmission antenna 11 Reception antenna 12 Reception LNA
13 Receiver Mixer 14 Detector 20 Bumper

Claims (1)

A radar apparatus that detects a surrounding object by transmitting and receiving a radar beam through a member disposed in front of an antenna, wherein the transmission unit transmits a transmission beam modulated at a reference frequency from the antenna, and the transmission beam A reception unit that receives a reception beam reflected by the object, and a signal processing unit that calculates a distance to the object based on a time difference between the transmission beam and the reception beam,
The signal processing unit further controls the reference frequency so as to minimize a reflection loss from the member based on the received beam.

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