JP2968639B2 - FM radar module - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an FM radar module which constitutes an FM radar device used for an alarm system for preventing a rear-end collision of a vehicle.

[0002]

2. Description of the Related Art An on-vehicle radar device mounted on a vehicle such as a passenger car and used for an alarm device for collision prevention and collision prevention is required to detect a very short distance of about several tens of centimeters, so that an extremely high resolution is required. In this regard, the FM radar form is preferable to the pulse radar form. In addition, since the farthest measurement range to a target such as a preceding vehicle is at most several hundred meters, it is necessary to avoid interference with existing microwave band communication facilities and to reduce the size of the antenna. ,
Use of the millimeter wave band is preferred.

Conventionally, a module portion including an FM signal generator, a transmission / reception antenna and a mixer in the above-mentioned FM radar apparatus is based on a microstrip or waveguide waveguide as shown in FIGS. It is configured. FIG.
In the case of, the FM signal in the millimeter wave band generated by the FM signal generator 51 is divided by the power divider 52 composed of a coupler or the like. Represents the mixer 55 as a local signal.
Is supplied to one of the input terminals. The reflected wave received by the receiving antenna 54 is supplied to the other input terminal of the mixer 55, and generates a beat signal by mixing with the local signal. The frequency of the beat signal output from the mixer 55 is detected by the FFT processing circuit, converted into a distance from the object that has generated the reflected wave by the microprocessor, and displayed on the display.

In the case of FIG. 6, a millimeter-wave band FM signal generated by an FM signal generator 61 is divided by a power divider 62, and one of the signals is passed through a circulator 63 to an outside from a transmitting / receiving antenna 64. While being radiated, the other is supplied to one input terminal of the mixer 65 as a local signal. The reflected wave received by the transmitting / receiving antenna 64 is supplied to the other input terminal of the mixer 65, and generates a beat signal by mixing with the local signal. In the radar modules shown in FIGS. 5 and 6, appropriate portions, for example,
An isolator is arranged between the FM signal generator and the power divider.

[0005]

The conventional FM radar modules shown in FIGS. 5 and 6 are required to be further reduced in size and cost, including reduction in the number of parts.

[0006]

According to the FM radar module of the present invention, a transmitting antenna and a receiving antenna are installed as a transmitting / receiving antenna and a waveguide for connecting the transmitting / receiving antenna and the FM signal generator is provided. By arranging the non-linear elements constituting the mixer, the size and the cost can be reduced while reducing the number of components such as the power divider and the circulator.

[0007]

The FM signal generated by the FM signal generator is supplied to a transmission / reception antenna through a waveguide such as a waveguide in which a mixer including a non-linear element such as a Schottky barrier diode is disposed in the middle. And emitted from here. The portion of the radiated FM signal that is reflected by the object is received as a reflected wave by the transmitting / receiving antenna, and reaches the mixer in the waveguide by following the reverse path to the radiation.
The beat signal is generated by being mixed with the FM signal supplied from the FM signal generator.

FIG. 1 is a plan view showing the configuration of an FM radar module according to one embodiment of the present invention, and FIG. 2 is an equivalent circuit thereof. Referring to FIG. 1 and FIG.
The M radar module includes an FM signal generator 11, an antenna 12 for both transmission and reception, a waveguide 13, and a mixer 14.

The waveguide 13 is a rectangular millimeter wave band waveguide formed in the metal block 10, and its distal end has a width and a height that are both linear toward the distal end. It is connected to an increasing quadrangular pyramid horn antenna 12.
The FM signal generator 11 includes a Gunn diode GD that generates a millimeter wave band signal, and a varactor diode VD for frequency modulation that changes the oscillation frequency of the Gunn diode GD almost linearly. It is composed of a planar circuit in which a bias supply line and a modulation signal supply line are formed by thin conductors for supplying a bias voltage and a modulation voltage to the element. Similarly, the mixer 14
Each of them also has a Schottky barrier diode SBD mounted thereon, and is constituted by a planar circuit in which conductor thin sections are formed that also serve as a bias supply path and a signal path for extracting a beat signal.

As shown in FIG. 3, an example of a planar circuit constituting the FM signal generator 11 is tetrafluoroethylene (TFE).
And the like, and a bias supply line and a modulation signal supply line formed by conductor thin pieces 11b and 11c formed on the surface of the dielectric substrate. This planar circuit is held outside the waveguide 13 indicated by the dashed line while maintaining a small gap of less than a half wavelength of the FM signal in the vertical and horizontal directions in the cavity formed in the metal block 10. The propagation of the FM signal in the millimeter wave band along this planar circuit is suppressed.

A metal stud STD serving as a sheet sink and a grounding mechanism for one terminal is inserted into the metal block 10 by being screwed into a screw hole formed on the side.
The Gunn diode GD held at the tip of this stud is positioned in the waveguide 13 shown by a dashed line,
The other terminal of this Gunn diode is electrically connected to the conductive foil 11b for bias supply. The varactor diode VD is positioned in the waveguide 13 while being held between the conductor thin pieces 11b and 11c of the planar circuit.

An example of a planar circuit constituting the mixer 14 is as follows.
As shown in FIG. 4, a dielectric substrate 14a and a conductive thin plate 14 for bias supply formed on the surface of the dielectric substrate 14a.
b, 14c and the like. This planar circuit is
Outside the waveguide 13 shown by the dashed line, the metal block 1
It is held in a cavity formed in the space 0 with a small gap of less than a half wavelength of the FM signal in the vertical and horizontal directions, and the propagation of the FM signal along this planar circuit is suppressed. That is, the conductor thin pieces 14b and 14c of this planar circuit
The cavity in the metal block forms a low-pass filter exemplified as a choke coil in the equivalent circuit of FIG. Schottky barrier diode SBD
Are positioned in a waveguide 13 indicated by a dashed line while being held between conductor thin sections of a planar circuit.

Referring to FIGS. 1 and 2, the FM signal generator 1
1 propagates through the waveguide 13 and passes through the mixer 14 while undergoing some passage loss due to the partial conversion to a harmonic by the Schottky barrier diode SBD. The light reaches the transmitting / receiving antenna 12, from which it is radiated to the outside. The portion of the radiated FM signal that is reflected by the object is received as a reflected wave by the transmitting / receiving antenna 12, and the waveguide 13 is turned in the opposite direction to the radiation.
And reaches the Schottky barrier diode SBD of the mixer 14. The Schottky barrier diode SBD mixes the FM signal received as the reflected wave with the FM signal being supplied from the FM signal generator 11 to generate a beat signal having a difference frequency. The beat signal is taken out of the module through a coaxial line 15 which also serves as a bias supply line and a signal line for taking out the beat signal.

In the above, a configuration in which a non-linear element such as a Schottky barrier diode is mounted on a planar circuit inserted into a waveguide has been exemplified. However, without interposing such a planar circuit, a non-linear element such as a Schottky barrier diode is directly arranged in the waveguide, or is arranged in a coaxial / waveguide converter connected to the waveguide. It is also possible to adopt a configuration in which The same applies to the FM signal generator.

Further, between the FM signal generator and the mixer,
A configuration may be adopted in which appropriate components such as an isolator are added as necessary.

[0016]

As described in detail above, the present invention
The M radar module has a transmitting / receiving antenna and a transmitting / receiving antenna.
Since the nonlinear element that constitutes the mixer is arranged in the waveguide that connects to the M signal generator, parts such as power dividers and circulators that were conventionally required can be reduced, and the size can be reduced accordingly. And cost reduction can be realized.

[Brief description of the drawings]

FIG. 1 is a plan view showing a configuration of an FM radar module according to one embodiment of the present invention.

FIG. 2 is an equivalent circuit diagram of the FM radar module of FIG. 1;

FIG. 3 is a plan view showing an example of a plane circuit constituting the FM signal generator 11 of FIG. 1;

FIG. 4 is a circuit diagram showing an example of a planar circuit constituting the mixer 14 of FIG.

FIG. 5 is a block diagram illustrating an example of a configuration of a conventional FM radar module.

FIG. 6 is a block diagram showing another example of the configuration of the conventional FM radar module.

[Explanation of symbols]

 Reference Signs List 11 FM signal generator 12 Transmitting / receiving antenna 13 Waveguide 14 Mixer 15 Coaxial line

Continuation of the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) G01S 7/00-7/42 G01S 13/00-13/95

Claims (4)

(57) [Claims] 1. An FM signal generator for generating an FM signal whose frequency changes with time, a transmitting antenna for radiating the FM signal, a receiving antenna for receiving the radiated FM signal, and radiating from the transmitting antenna. An FM radar module including a mixer for mixing an FM signal to be transmitted and an FM signal received by the receiving antenna to generate a beat signal, the antenna for transmitting and receiving the transmitting antenna and the receiving antenna.
Antenna and the antenna for both transmission and reception and the FM signal generator
While connecting with a pipe, the mixer is placed inside the waveguide.
The mixing, the mixer comprises a mixing diode and a mixing diode;
Positioning the waveguide at a predetermined location inside the waveguide
The conductor forming the waveguide outside the waveguide
To form a gap less than half a wavelength of the FM signal
Or a planar circuit that includes a bias supply line
And the FM signal generator comprises a frequency modulation diode,
A predetermined frequency modulation diode inside the waveguide.
At the point and outside this waveguide
Between the conductor forming the waveguide and the half wavelength of the FM signal
Bias supply line that is held while forming a gap less than
FM Les characterized and that a planar circuit including a road
Loader module. 2. The FM signal generator according to claim 1, wherein the FM signal generator is screwed to a wall of the waveguide.
Generates a high-frequency signal fixed to the tip of the heat dissipation stud
FM radar further comprising a diode
module. 3. A waveguide according to claim 1 , wherein said waveguide has a rectangular cross-sectional shape kept constant in the length direction.
FM radar characterized by a rectangular waveguide
Wool. 4. The rectangular waveguide according to claim 1, wherein the transmitting / receiving antenna is provided at a tip end of the rectangular waveguide.
The angle from which the width and height are linearly enlarged in the length direction from the minute
FM radar characterized by a conical horn antenna
Device.