JP3453080B2 - Millimeter wave radar - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a millimeter wave radar capable of detecting from short range to long range.

[0002]

2. Description of the Related Art As a millimeter wave radar system used in vehicles such as passenger cars, buses, trucks, etc., FM-CW,
Various proposals such as dual-frequency CW, pulse, pulse Doppler, spread spectrum, etc. have been made, and development has been made aiming at a maximum detection distance of about 300 m. On the other hand, it has been pointed out that it is important to detect a short distance of about several tens of cm to several cm when starting from the rear or turning left.

For example, in Japanese Patent Laid-Open No. 10-22864 , as shown in FIG. 17, a dielectric line is provided in a direction orthogonal to the dielectric strip 81, and a dielectric pattern for an RF choke is provided. A Gunn diode is connected, and a varactor diode is connected between the dielectric line and the RF choke dielectric pattern. A bias voltage is applied to the Gunn diode from the bias terminal 82, and a modulation signal is applied to the varactor diode from the terminal 83 to change the capacitance of the varactor diode and change the oscillation frequency of the Gunn diode. This patent application uses FM-CW. The oscillation output is transmitted from the transmission antenna 86 via the circulator 84 and the transmission dielectric resonator 85.
The radio wave reflected by the detection object is received by the receiving antenna 87, and the mixer 88 obtains the IF signal at the terminal 89.

[0004]

[Problems to be Solved by the Invention]
Most often used is the M-CW method, but FM-CW
Since the method is noise, it is difficult to detect highly accurate objects of a few meters or less.
Further, since the oscillation frequency of the oscillator is changed with time, there remains a problem in the detection distance accuracy in terms of frequency stability. The pulse method can stabilize the oscillating frequency, so it has good detection distance accuracy. However, millimeter waves are used to detect short distances on the order of several cm, and millimeter wave signals are generated using trigger pulses on the order of several ns. Need to be modulated. In order to modulate a millimeter wave with a pulse width on the order of several ns using a semiconductor element, a PIN diode which is commonly used at present in a pulse radar is used.
Since the minority carrier lifetime of the N diode is long on the order of several tens of ns, it is difficult to handle high-speed pulses of the order of several ns.

There are short-range radars that utilize light waves or ultrasonic waves, but there is a problem that light waves cause malfunctions due to rainwater, dew, fog, etc., and ultrasonic waves cause malfunctions due to temperature or wind.

The present invention solves the above-mentioned problems, and operates stably even in bad weather, maintains a maximum distance of about 300 m, and is several tens of centimeters, which has been difficult in the past.
The present invention provides a millimeter wave radar capable of detecting a short distance of approximately several cm with high accuracy.

[0007]

A millimeter wave radar according to a first aspect of the present invention comprises a millimeter wave band oscillator, a frequency conversion type pulse modulator for pulse-modulating an oscillation signal from the millimeter wave band oscillator, It is characterized by comprising a transmitting antenna for transmitting the millimeter wave band signal reflected by the frequency conversion type pulse modulator and a receiving antenna for receiving the reflected wave reflected by the detection object.

Due to this characteristic, from a short distance of several cm to several 1
Object detection up to a long distance of 00 m can be performed with high accuracy without noise. Further, since the present invention is a method of directly transmitting the oscillation output of the first millimeter waveband oscillator, the transmission output can be increased as compared with the case where an up-converted signal is used for the transmission wave. That is, when the up-converted output is used for the transmission wave, there is an insertion loss when the up-conversion is performed, and the transmission output becomes small. Therefore, a power amplifier for the transmission wave must be used to compensate for this. However, the present invention solves the problem by utilizing the high-power reflected wave generated when the high-speed operation element of the pulse modulator is mismatched as the transmitted wave of the radar, and further, the high performance of the radar and the low cost are achieved. Has been realized.

[0009] Millimeter-wave radar according to claim 2 of the present invention, the frequency conversion pulse modulator, Schottky diodes and FET (field effect transistor) or H
At least one of EMTs (high electron mobility transistors) is provided.

Due to this feature, the pulse modulator has a two-terminal semiconductor element such as a Schottky barrier diode, a FET (field effect transistor) or a HEMT (high electron mobility transistor), in which the minority carrier lifetime is as short as a few ps. ), A high-speed operation element such as a three-terminal semiconductor element is used, so that high-speed switching operation is performed and a millimeter wave pulse radar can be obtained.

In the millimeter wave radar according to a third aspect of the present invention, the frequency conversion type pulse modulator includes a circulator, and the circulator has an input port, an output port, and between the input port and the output port. It is characterized by having a control port.

[0012]

In the millimeter wave radar according to a fourth aspect of the present invention, the frequency conversion type pulse modulator has a minority carrier lifetime.
Frequency using a switching element with a life time of 10 ns or less
It is a number conversion type pulse modulator .

With this feature, the oscillation signal of the millimeter-wave band oscillator is frequency-converted, and the output of one millimeter-wave oscillator can be used for transmission and for local oscillation of the receiver. Well
In addition, minority carrier lifetime is less than 10ns
Since a switching element is used, high-speed switching is impossible.
Can be realized easily.

A millimeter wave radar according to a fifth aspect of the present invention is a pulse signal that is different from a received signal received by the receiving antenna.
Providing a mixer that mixes with the signal modulated by the modulator
And are characterized .

Due to this characteristic, from a short distance of several cm to several 1
Object detection up to a long distance of 00 m can be performed with high accuracy without noise. Further, since the present invention is a method of directly transmitting the oscillation output of the millimeter waveband oscillator, the transmission output can be increased as compared with the case where an up-converted signal is used for the transmission wave. That is, when the up-converted output is used for the transmission wave, there is an insertion loss when the up-conversion is performed, and the transmission output becomes small. Therefore, a power amplifier for the transmission wave must be used to compensate for this. However, the present invention solves the problem by utilizing the high-power reflected wave generated when the high-speed operation element of the pulse modulator is mismatched as the transmitted wave of the radar, and further, the high performance of the radar and the low cost are achieved. Has been realized. Furthermore, one millimeter wave oscillator can be used for transmission and reception, and can be manufactured at low cost.

The millimeter-wave radar according to claim 6 of the present invention is to transmit the millimeter-wave band signals reflected by said frequency-converted pulse modulator to the transmitting antenna, the frequency conversion pulse <br/> scan modulation hand <br/> stage for transmitting a pulse signal modulated by the vessel to the mixer is characterized in that it is a band filter.

Due to this feature, transmission is performed by a bandpass filter.
It is possible to distinguish between the signal sent to the mixer and the signal sent to the mixer.
The output of the millimeter wave oscillator is used for transmission and the local oscillation of the receiver.
Can be used .

A millimeter wave radar according to a seventh aspect of the present invention is a millimeter wave band oscillator, a first NRD guide for guiding the output of the millimeter wave band oscillator to a first circulator, and the first circulator. A pulse modulator connected to the second circulator, a second NRD guide connecting the first circulator and the second circulator, a third NRD guide connected to the second circulator, and the third NRD guide. The transmission / reception antenna is connected, and the mixer is connected to the second circulator.

With this feature, one millimeter wave oscillator can be used for transmission and reception, and can be manufactured at low cost. Further, it can be configured with low loss and compact, and stable operation of millimeter waves can be obtained.

The millimeter wave radar according to claim 8 of the present invention
The frequency conversion type pulse modulator is
Toki barrier diode) and load resistance, and bias
Millimeter wave reflection by the SBD, millimeter depending on the state of voltage
The wave frequency conversion is controlled in a pulsed manner .

Further , the millimeter wave laser according to claim 9 of the present invention.
The frequency conversion type pulse modulator is an FET or
Includes either one of HEMT and load resistance, and FET
Or, in the state of bias voltage to either HEMT
Therefore, the error caused by either the FET or HEMT
Controlling re-wave reflection and millimeter-wave frequency conversion in pulses
Is characterized by .

[0023]

DESCRIPTION OF THE PREFERRED EMBODIMENTS (Embodiment 1) FIG. 1 shows a circuit diagram of Embodiment 1. The millimeter wave radar of FIG. 1 includes a millimeter wave band oscillator 1, a pulse modulator 2, a circulator 3, a transmitting antenna 5, a receiving antenna 6, a mixer 7, a local oscillator 8, an IF amplifier 9, a variable gain amplifier (AGC) 10, and a detection. Bowl 11,
It comprises a baseband (BB) amplifier 12. The millimeter waveband oscillator 1, the pulse modulator 2, the circulator 3, the transmitting antenna 5, the receiving antenna 6, the mixer 7, and the local oscillator 8 are connected using an NRD guide (non-radiative dielectric line) to form a millimeter wave circuit. Composed. A directional coupler 13 for guiding a part of the transmission signal to the mixer 7 is provided near the transmission antenna 5 and the reception antenna 6.

The millimeter-wave band oscillator 1 is composed of a frequency-stabilized Gunn oscillator using a Gunn diode, and obtains a 60 GHz band or 77 GHz band oscillation frequency signal. Pulse modulator 2
Is composed of an ASK modulator using a Schottky barrier diode (SBD) as shown in FIGS. In FIG. 2, the pulse modulator 2 is configured by using an NRD guide, and the NRD guide includes an upper conductor plate 101 and a lower conductor plate 102.
With a dielectric strip in between to provide a single mode operating band. The oscillation output of the millimeter waveband oscillator 1 is applied to the first NRD guide 103, and the oscillation output signal goes toward the circulator 104. The circulator 103 has an NRD guide 105 directed to the pulse modulator 2.
And an NRD guide 106 that outputs a modulated output signal are connected. The NRD guide 105 is connected to the pulse modulator 2 via the air gap 107.

The pulse modulator 2 is, as shown in FIG. 3, Teflon (Teflon is a registered trademark, and is officially referred to as "tetrafluoride".
Copper foil is etched into a substrate 108 ( which is "ethylene") to form a bias choke 109 and a low pass filter 110, which bias choke 109 and low pass filter 110.
A Schottky diode 111 is connected between the two. Here, as an example, the Teflon substrate 108 has a width of 2.
The bias choke has a width of 2.0 mm and a length of 1.0 mm, and a thick pattern portion having a width of 0.2 m.
A thin pattern having a length of 1.1 mm and a length of 1.1 mm is formed by repeating three steps. The low-pass filter 110 has a thick portion having a width of 2.0 mm and a length of 1.0 mm, and a wide portion having a width of 0.2 mm and a length of 1.
It consists of a thin part of 1 mm. Then, between the bias choke 109 and the low-pass filter 110, two electrodes 112 and 113 having a width of 1.4 mm and a length of 1.0 mm are formed with a gap of 0.4 mm formed therebetween.
And 113, the Schottky barrier diode 111 is connected. In this pulse modulator 2, a Teflon piece 114 is attached to the back surface of the mount of the Schottky barrier diode 111 to protect the Schottky barrier diode 111 from damage. Schottky barrier diode 1
A high dielectric constant thin film 115 is attached to the surface side (millimeter wave incident side) of the mount 11 to form a Schottky barrier diode having a small resistance and an NRD guide 105 having a high impedance.
It is consistent with. The thickness of the high dielectric constant thin film is about λ / 4
Is. Further, before and after the high dielectric constant thin film, a Teflon piece 116 is used.
Is attached to enhance the matching with the NRD guide.

Bias choke 109 of pulse modulator 2
Through the hole 118 of the lower conductor plate 102 by the wiring 117,
It is connected to the digital signal terminal 121 via the DC load resistor 119 and the DC load resistor 120. As an example, the DC load resistance 119 is 10Ω and the DC load resistance 120 is 50Ω.
Was set to. Further, the low-pass filter 110 is connected to the ground through the hole 123 of the lower conductor plate 102 by the wiring 122.

Therefore, the millimeter-wave band oscillator 1 is 60 GH
oscillates z, and the digital signal terminal 121 of the pulse modulator 2
When a negative polarity trigger pulse having a pulse width of 5 ns and a pulse repetition period of 1 μs is applied as a bias voltage, the Schottky barrier diode 111 operates as a detector because the bias voltage is in the ON state during the forward direction, and the millimeter waveband oscillator 1 The oscillation signal is absorbed by the DC load resistors 119 and 120 connected to the Schottky barrier diode.
Here, the DC load resistors 119 and 120 are set so that the forward / reverse bias application Schottky diode 111 and the pulse wave can be matched. On the other hand, when the bias voltage is in the reverse direction, the Schottky diode 111 is in the OFF state, so that the Schottky diode 111 does not operate as a detector, and the oscillation frequency signal of the millimeter waveband oscillator 1 incident on the pulse modulator 2 becomes unmatched and reflected. . ASK pulse modulation is performed by the above operation.

The pulse modulator 2 is an FET or HEMT.
A high-speed operation element such as a three-terminal semiconductor element can be used to form the structure shown in FIG. As shown in the circuit diagram of the pulse modulator 2, a modulation port 53 is arranged between the input port 51 and the output port 52 of the circulator 3, and the source / source of the 3-terminal semiconductor element 54 is connected to the modulation port 53.
Connect the drain terminal. A matching load resistor 56 is connected between the source and ground, a pulse signal is applied to the gate as a bias voltage from a terminal 58 via an RF choke 57, and a noise removing choke 5 is applied from a terminal 60 to the drain.
A millimeter wave band signal is applied via 9 to operate. Therefore, when the pulse signal applied to the gate is at a high level, the drain and source of the three-terminal semiconductor element are short-circuited, and the millimeter wave signal input to the drain is the matched load resistance 56.
Is absorbed by. When the pulse signal is at the low level, the drain and source are open, so the millimeter wave signal input to the drain is reflected, and as a result, the pulse modulated signal is obtained at the output port 52 of the circulator 3.

FIG. 5 shows an example in which the circuit shown in FIG. 4 is applied to a microstrip.
Is attached. Incidentally, 61 is a DC blocking capacitor, 6
2 shows a matching circuit. In the circuit of FIG. 5, the operation of the up converter is performed in the same manner as the circuit of FIG. Also, FIG. 6 shows NR
An example applied to the D guide is shown, and the same parts as in FIG. 4 are shown with a subscript b.

As described above, the millimeter waveband signal reflected by the pulse modulator 2 passes through the circulator 3 and is transmitted from the transmission antenna 5, and a part of the millimeter waveband signal is used as a reference wave by the directional coupler 13. Guided to Mixer 7.

The reflected wave reflected by the sensing object is received by the receiving antenna 6 and input to the mixer 7. The received signal, the local oscillation signal from the local oscillator 8 and a part of the reference wave supplied by the directional coupler 13 are input to the mixer 7, and the mixer 7 operates as a down converter to generate an intermediate frequency signal. Output. Here, the local oscillator 8 is composed of a frequency-stabilized Gunn oscillator by a Gunn diode similarly to the millimeter waveband oscillator 1, and the mixer 7 is composed of a balanced mixer to perform heterodyne reception. The intermediate frequency signal further includes an IF amplifier 9, a variable gain amplifier (AGC) 10, a detector 11, a baseband (B
B) The reference wave pulse P is output to the output terminal 15 through the amplifier 12.
1 and the reflected wave pulse P2 are obtained.

As shown in FIG. 7, by measuring the time difference Δt (s) between the reference wave pulse P1 and the received wave pulse P2,
The distance R (m) to the detected object can be calculated from the equation (1).

R = Δt · c / 2 (1) where c is the speed of light (m / s) The maximum detection distance (Rmax) of this millimeter wave radar is the pulse repetition period (tp) applied to the pulse modulator 2. ) Is obtained by the equation (2).

Rmax = tp · c / 2 (2) Further, the minimum detection distance (Rmin) is obtained from the pulse width (tw) applied to the pulse modulator 2 by the equation (3).

Rmin = tw · c / 2 (3) The pulse modulator 2 of the present invention is a two-terminal semiconductor device such as a Schottky barrier diode, or an FET (field effect transistor) or a HEMT (high electron mobility transistor). Since the NRD guide ASK modulator is operated by an external modulation method using a high-speed operation element such as a three-terminal semiconductor element, the minority carrier lifetime is several p
Since it is very short on the order of s, a high-speed switching operation is performed, and it has a high-speed performance with a sufficient margin for a transmission speed of 400 Mbps, so that a minimum detection distance of several cm can be obtained.

The millimeter waveband oscillator 1 of the present invention is composed of a frequency-stabilized Gunn oscillator, and the pulse modulator 2 is A
Since it is composed of an SK modulator, the frequency fluctuation is small, and the measurement error is ± ± from several cm to several tens of meters as shown in FIG. 8 (horizontal axis shows detection distance, vertical axis shows error).
It is 2 cm or less, and the distance to the detection object can be detected with high accuracy.

Further, since the present invention is a system for directly transmitting the oscillation output of the millimeter waveband oscillator, the transmission output can be increased as compared with the case where the up-converted signal is used as the reference wave. That is, when the up-converted output is used for the transmission wave, there is an insertion loss when the up-conversion is performed, and the transmission output becomes small. Therefore, a power amplifier for the transmission wave must be used to compensate for this. However, the present invention is problematic in that the bias voltage applied to the high-speed operation element that constitutes the pulse modulator is temporally controlled, and the high-power reflected wave when the high-speed operation element is mismatched is used as the reference wave of the radar. In addition to this, we have realized higher radar performance and lower costs. (Embodiment 2) In Embodiment 2 of the present invention, the millimeter wave radar includes an oscillator 21, a first circulator 22, a second circulator 23, a frequency conversion pulse modulator 24, as shown in FIG. Mixer (down converter) 25
And a bandpass filter 26 and an antenna 27.

The oscillator 21 is constructed by using a Gunn diode.
And oscillates a millimeter-wave band signal, and this oscillating signal
Frequency conversion pulse modulator 24 via the circulator 22
Is supplied to. Frequency conversion pulse modulator 24 is shot
It consists of a barrier barrier diode (SBD)
As shown in Fig. 10 (a), there is no
The modulated continuous wave signal CW is converted to the intermediate frequency signal P_IFApplied as
In addition, as shown in FIG. 10B, the pulse width tw, pulse
Negative polarity trigger pulse with a repetition period tp
Pressure V_BIs applied as. Schottky barrier diode
Operates as a frequency converter when the bias voltage is in the forward direction
The millimeter wave matching circuit is set so that According to
The frequency conversion pulse modulator 24 has a first circular
At the same time that the oscillation signal of the oscillator 21 is applied via the controller 22.
And the intermediate frequency signal P_IFAnd forward bias voltage V_BMark
Then, the frequency conversion pulse modulator 24 changes the frequency.
It operates as a pulse converter and the millimeter-wave band frequency signal is
Its frequency (f_RF) And the intermediate frequency (f_IF) Of sum and difference
Frequency (f_RF± f_IF) Component. This frequency
The split signal is the first circulator 22 and the second circulator.
After passing through the filter 23, it is guided to the bandpass filter 26. band
The center frequency of the bandpass filter 26 is the millimeter-wave band signal of the oscillator 21.
Since it is set to the frequency of the signal, the sum and difference frequencies
(F_RF± f_IF) Signal is reflected by the bandpass filter 26.
It The reflected sum and difference frequencies (f_RF± f _IF) Ingredients
Issue via the second circulator 23 to the station of the mixer 25
It is added as a local oscillation signal.

On the other hand, when the reverse bias voltage is applied to the Schottky barrier diode, the frequency conversion pulse modulator 24 does not operate as an up-converter, so that the millimeter waveband frequency signal applied to the Schottky barrier diode does not match. The light is reflected at this portion, passes through the first circulator 22 and the second circulator 23, and then is guided to the bandpass filter 26. Since the center frequency of the band-pass filter 26 is set to the frequency of the millimeter-wave band signal of the oscillator 21, the millimeter-wave band frequency signal guided to the band-pass filter 26 passes through the band-pass filter 26 and is transmitted from the antenna 27 to the antenna 27 of FIG. It is emitted as a radar transmission signal P _T as shown in c). Then, the reflected wave from the detected object is heterodyne-detected with the frequency signals of the sum and difference by the balance mixer type down converter constituted by the Schottky barrier diode, and as a result, the reception output P _R shown in FIG. 10D is obtained. To be Distance R from radar to detected object
(M) is represented by the above equation (1), where Δt (s) is the time difference between the time when the transmitted wave is emitted and the time when the reflected wave arrives, and c (m / s) is the speed of light. In addition, the maximum detection distance Rma of the millimeter wave radar from the pulse repetition period tp
x can be obtained from the equation (2), and the pulse width t
The minimum detection distance Rmin from w can be obtained by the above equation (3).

Further, since the present invention is a method of directly transmitting the oscillation output of the millimeter waveband oscillator, the transmission output can be increased as compared with the case where the up-converted signal is used as the reference wave. That is, when the up-converted output is used for the transmission wave, there is an insertion loss when the up-conversion is performed, and the transmission output becomes small. Therefore, a power amplifier for the transmission wave must be used to compensate for this. However, the present invention is problematic in that the bias voltage applied to the high-speed operation element that constitutes the pulse modulator is temporally controlled, and the high-power reflected wave when the high-speed operation element is mismatched is used as the reference wave of the radar. In addition to this, we have realized higher radar performance and lower costs.

The millimeter wave radar according to the second embodiment of the present invention is an NRD.
A guide (non-radiative dielectric line) is used to configure as shown in the plan view of FIG. 11 and the three-dimensional view of FIG. The NRD guide is used as a transmission line in the millimeter wave band such as the 35 GHz band and the 60 GHz band, and is formed by inserting a rectangular dielectric strip in a cut parallel plate waveguide. As shown in FIG. 13, the NRD guide is an upper conductor plate 31 made of a good conductor / non-magnetic material such as aluminum, copper, or brass, which is vertically arranged in parallel at a predetermined interval and has a thickness of about 4.0 mm.
And a lower conductor plate 32, a rectangular rod-shaped dielectric strip 33 having a height a and a width b is arranged. The dielectric strip 33 has a low dielectric constant of 3.0 or less at a high frequency such as a millimeter wave band, for example, a Teflon of 2.04, 2.1.
When a dielectric such as polyethylene of 2.56 or polystyrene of 2.56 is used and the free space wavelength of the signal frequency is λ ₀ ,
Height a of the dielectric strip 33 is near, the width b of a = 0.45λ ₀ is the dielectric constant When epsilon _r,

[0042]

[Equation 1]

Is set to In the 60 GHz band, when Teflon is used as the dielectric strip, the height a =
Set to 2.25mm, width b = 2.5mm, 55GH
A single mode operating band is obtained from z at 65.5 GHz.

The millimeter-wave radar of the present invention is constructed by using the NRD guide as a transmission line, and the Gunn diode oscillator 21 is shown in FIG. 14 (a) from the other direction of the Gunn diode oscillator 21 part of FIG. 11 and FIG. Shows a three-dimensional view of
Further, as shown in a partial cross-sectional view of the Gunn diode oscillator in FIG. 14B, the Gunn diode 41 is enclosed in a cylindrical porcelain package and has an H-shaped cross section, and a λ / 4 step low-pass filter is provided. The metal piece 42 made of brass is mounted on the side surface and laterally loaded between the upper conductor plate 31 and the lower conductor plate 32.

On one surface of the metal piece 42, as shown in FIG.
As shown in (c), the microstrip low-pass filter line 4 formed by etching has a λ / 4 choke pattern.
A Teflon substrate 43 having a thickness of 0.13 mm, on which No. 4 is formed, is attached, and a bias voltage is applied to the Gunn diode 41 via the microstrip low-pass filter line 44,
A 59 GHz band oscillation signal is obtained from the Gunn diode oscillator 21. This oscillation signal is guided to the NRD guide 28a via the metal strip resonator 47 in which the metal strip 46 is formed on the Teflon substrate 45 shown in FIG. 14 (d). The metal strip resonator 47 can determine the oscillation frequency according to the width c, the length d of the metal strip 46 and the thickness e of the Teflon substrate. For example, the thickness e of the Teflon substrate is set to 0.
265 mm, the width c of the metal strip is 1.4 mm,
When the length d changes from 1.5 mm to 2.5 mm, 5
Can be changed from 5GHz to 63GHz, 60G
Oscillation output 6 that almost covers the band of Hz band NRD guide
0 mW or more is obtained. Here, it is desirable to insert a mode suppressor 29 at the tip of the NRD guide 28 in contact with the metal strip resonator 47 in order to suppress unnecessary modes generated at the coupling portion. The metal strip resonator 46 is adjusted to a target frequency of 59 GHz band by changing the length of the metal strip. In this example, 58.36 GHz or 5
It was adjusted to 9.15 GHz.

A ceramic resonator 48 having a high Q for frequency stabilization is arranged near the NRD guide 28a so as to be side-coupled, and the ceramic resonator 48 operates with the length of the upper and lower conductor plates as the resonator length. By doing so, frequency stabilization is achieved. The ceramic resonator 48 has a high-Q ceramic disk 48a in the center, and is sandwiched by Teflon disks 48b and 48c at the top and bottom. The ceramic disk 48a is positioned at the center of the upper and lower conductor plates to eliminate radiation. . Ceramic disc 48
For a, the resonator length can be shortened and the resonance frequency can be increased by reducing the thickness t, and when the thickness is 0.47 mm, the resonance frequency is 59 GHz.

As shown in FIG. 11, the ceramic resonator 48 has a distance g from the NRD guide 28a of 1.35 m.
The standing wave ratio was set to 2. Further, the distance z from the mode suppressor end face of the NRD guide 28 to the center of the ceramic resonator 48 is set to a position where the ceramic resonator 48 locks. The locking positions were 6.0 mm and 6.5 mm. At the time of rocking, even if the frequency axis (SPAN) of the spectrum analyzer was set to 50 kHz, fluctuations in the oscillation frequency were not observed, and the waveform was clean.

In the ceramic resonator 48, alumina or the like can be used as a substitute for the ceramic disc, and polyethylene, polystyrene, boron nitride, etc. can be used as a substitute for the Teflon disc. The shape can be elliptical, triangular, or rectangular other than circular, but circular is the easiest to manufacture. Further, the ceramic resonator 48 may have a structure in which one of the upper side and the lower side is supported by a Teflon disk so that the ceramic disk is located in the center of the upper and lower conductor plates, and the other is a space. In this case, the ceramic disk should have a dielectric constant close to infinity.

As described above, the ceramic resonator 48 has a ceramic disk 48a, which is a relatively hard dielectric material having a high Q, in the middle, and the upper and lower parts are Teflon disks 48b, 4 which are soft dielectric materials having a lower dielectric constant than ceramics.
The ceramic disk 48a is located at the center of the upper and lower conductor plates so as to be sandwiched by the 8c. The ceramic resonator 48 is preferably formed in a circular shape, and the circumference thereof is preferably covered with a ring-shaped Teflon tube (not shown) made of a dielectric material having a low dielectric constant. The Teflon tube prevents the ceramic resonator 48 from losing its shape, and
Prevents the influence of humidity inside the D guide transmitter and NRD guide receiver due to condensation. The resonance frequency of the ceramic resonator 48 is determined by the interval between the upper and lower conductor plates having the resonator length in the direction of the interval between the upper and lower conductor plates, including the thickness t, and the frequency at which this interval electrically becomes an integral multiple of a half wavelength. Resonates with. Since the ceramic resonator 48 resonates with TE ₍₀₂ δ), it is possible to increase the resonance frequency by thinning the ceramic disk 48a. While adjusting the overall height of the ceramic resonator 48 to a distance between the upper and lower conductor plates of 2.25 mm, the ceramic disk 48a is made thin, and the Teflon disk 48b,
The resonance frequency is adjusted by increasing the thickness of 48c. The resonance frequency in the 59 GHz band is obtained by setting the thickness of the ceramic disk 48a to 0.47 mm.

The oscillation signal input to the NRD guide 28a is guided to the frequency conversion pulse modulator 24 by the first circulator 22 and input through the NRD guide 28b. The frequency conversion pulse modulator 24 is configured as shown in FIG. 15, and is configured almost the same as the pulse modulator of FIGS. 2 and 3 described in the first embodiment, but the signal applied to the bias choke is different. There is. That is, as shown in FIG. 13, the unmodulated continuous wave of FIG. 10A is applied to the IF application terminal 130 and the bias terminal 131 of FIG.
The trigger pulse of (b) is applied.

This frequency conversion pulse modulator is shown in FIG.
6, a three-terminal semiconductor device 140 such as a FET (field effect transistor) or HEMT (high electron mobility transistor) is used, and the input end port 51 and the output end port of the first circulator 22 are formed. A modulation port 53 is arranged between 52, and the frequency conversion pulse modulator 24 is connected to the modulation port 53. 3-terminal semiconductor device 1
As shown in FIG. 16, the circuit diagram of the frequency conversion pulse modulator 24 composed of 40 connects the gate / source terminal of the three-terminal semiconductor element 140 to the modulation end port 53 of the first circulator 22. A millimeter wave band signal is applied to the gate, and the unmodulated continuous wave signal of FIG. 10A is applied to the drain from the terminal 142 as an intermediate frequency signal. Further, the pulse of FIG. 10B is applied as a bias voltage from the terminal 141 to the drain. In the frequency conversion pulse modulator 24 having this configuration, when a millimeter waveband oscillation signal is applied to the input end port 51 and a pulse is applied to the terminal 141, when the GaAsFET is used as the three-terminal semiconductor element 140, the pulse signal is at the “Low” level. At (−several V), the resistance between the drain and the source of the three-terminal semiconductor element 140 becomes high, and the transmission wave input to the three-terminal semiconductor element 140 is reflected and output to the output port 52. On the other hand, if the pulse signal is "High
At the h ″ level (+ several V), the drain-source region becomes a non-linear region, and the sum and difference frequency signals of the millimeter waveband oscillation signal and the intermediate frequency signal are obtained at the output end port 52. Based on the above operation A frequency conversion pulse modulator is constructed.

As described above, the sum signal and the difference signal, which are frequency-converted by the frequency conversion pulse modulator 24, are directed to the band pass filter 26 through the second circulator 23 and the NRD guides 28c and 28d. Band pass filter 2
6 has a center frequency of 60.625 GHz and a bandwidth of 2 GH
It is composed of a three-stage Chebyshev filter of z, 0.5 dB ripple, passes only the millimeter wave band oscillation frequency signal, is transmitted to the transmitting antenna 27, and the millimeter wave is transmitted from the transmitting antenna 27. The sum signal and the difference signal of the frequency conversion pulse modulator 24 are reflected by the bandpass filter 26 and input to the mixer 25 via the second circulator 23.

The radio waves reflected by the detection object are received by the antenna, and are sent to the second circulator 23 and NRD guide 28e.
To the mixer 25 via. As shown in FIG. 12, the mixer 25 has a structure in which detection is performed by the Schottky barrier diode 61, and a Teflon piece 62 is attached to the back surface of the mount of the Schottky barrier diode 61 to protect the Schottky barrier diode 61 from damage. Further, a high dielectric constant thin film is attached to the surface of the mount of the Schottky barrier diode 61 (millimeter wave band signal incident side) to match the Schottky barrier diode having a low resistance and the NRD guide 28 having a high impedance. The thickness of the high dielectric constant thin film is about λ / 4. Furthermore, a Teflon chip 63 is attached after the high dielectric constant thin film to further enhance the matching with the NRD guide.

The millimeter wave band signal is down-converted by mixing the sum signal and the reflected wave by the mixer 25, and the original IF signal is obtained at the terminal 64. After that, although not shown, an IF amplifier 9, a variable gain amplifier (AGC) 10, a detector 11, and a baseband (BB) amplifier 12 are provided as in the first embodiment, and a reference wave pulse and a received wave pulse are output from an output terminal 15. To get Then, the distance to the detection object is detected.

Since the present invention directly transmits the oscillation output of the millimeter wave oscillator, the transmission output can be increased as compared with the case where the up-converted signal is used for the transmission wave. That is, when the up-converted output is used for the transmission wave, there is an insertion loss when the up-conversion is performed, and the transmission output becomes small. Therefore, a power amplifier for the transmission wave must be used to compensate for this. However, the present invention has a problem in that the bias voltage applied to the frequency conversion pulse modulator is temporally controlled, and the high-power reflected wave generated when the frequency conversion pulse modulator is mismatched is used as the transmission wave of the radar. In addition to this, we have realized high performance and low cost of the radar.

[0056]

As described above, according to the present invention, it is possible to detect an object from a short distance of several cm to a long distance of several hundred m with high accuracy and without noise. In addition, the pulse modulator has a short carrier life time of a few ps order, such as a two-terminal semiconductor device such as a Schottky barrier diode, or FET (field effect transistor) or HE.
Since a high-speed operation element such as a 3-terminal semiconductor element such as MT (high electron mobility transistor) is used, high-speed switching operation is performed and a millimeter wave pulse radar can be obtained. Further, the millimeter wave radar of the present invention can be constructed compactly, and stable millimeter wave operation can be obtained. Further, in the present invention, the longest detection distance is 1 of the pulse cycle.
From / 2, the shortest detection distance can be detected up to 1/2 of the pulse width. Further, according to the present invention, one millimeter wave oscillator can be used for transmission and reception, and can be manufactured at low cost. Further, the millimeter wave signal can be up-converted and pulse-modulated.

[Brief description of drawings]

FIG. 1 is a block diagram of a millimeter wave radar according to a first embodiment of the present invention.

FIG. 2 is a perspective view in which the millimeter wave radar according to the first embodiment is applied to an NRD guide.

FIG. 3 shows a plan view of a frequency conversion pulse modulator used in the first embodiment.

FIG. 4 shows a circuit diagram of a pulse modulator used in the first embodiment.

FIG. 5 shows a diagram in which a pulse modulator is configured by a microstrip.

FIG. 6 shows a diagram in which a pulse modulator is configured with an NRD guide.

FIG. 7 is a waveform diagram illustrating the operation of the first embodiment.

FIG. 8 is a diagram illustrating a measurement error according to the first embodiment.

FIG. 9 shows a block diagram of a second embodiment of the present invention.

FIG. 10 is a waveform diagram illustrating the operation of the second embodiment.

FIG. 11 is a plan view in which the millimeter wave radar according to the second embodiment is applied to an NRD guide.

FIG. 12 is a three-dimensional view in which the millimeter wave radar according to the second embodiment is applied to an NRD guide.

FIG. 13 is a diagram illustrating an NRD guide.

FIG. 14 shows an NRD guide cubic diagram near the Gunn diode oscillator.

FIG. 15 shows an NRD guide cubic diagram near a frequency conversion pulse modulator.

FIG. 16 shows a circuit diagram of a frequency conversion pulse modulator.

FIG. 17 shows a configuration of a conventional millimeter wave radar.

[Explanation of symbols]

1 Millimeter wave oscillator 2 pulse modulator 3 circulator 4 band filter 5 transmitting antenna 6 receiving antenna 7 Mixers 8 Local oscillator 9 IF amplifier 10 AGC 11 detector 12 BB amplifier 21 oscillator 22 First Circulator 23 Second Circulator 24 upconverter 25 Mixers 26 band filters 27 antenna

Continuation of front page (56) Reference JP-A-7-77576 (JP, A) JP-A-8-181509 (JP, A) JP-A-6-216654 (JP, A) JP-A-6-268445 (JP , A) JP-A-6-268446 (JP, A) JP-A-8-152470 (JP, A) JP-A-6-214008 (JP, A) JP-A-6-268447 (JP, A) JP-A-6-268447 (JP, A) 7-209409 (JP, A) JP-A-7-140228 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) G01S ⁷ /00-7/42 G01S 13/00-13 / 95

Claims (9)

(57) [Claims] 1. A millimeter waveband oscillator, a frequency conversion type pulse modulator for pulse-modulating an oscillation signal from the millimeter waveband oscillator, and a millimeter waveband signal reflected by the frequency conversion type pulse modulator. A millimeter wave radar comprising a transmitting antenna and a receiving antenna for receiving a reflected wave reflected by a detection object. 2. The frequency conversion type pulse modulation means comprises at least one of a Schottky diode, a FET (field effect transistor) and a HEMT (high electron mobility transistor). Millimeter wave radar. 3. The frequency conversion type pulse modulator comprises a circulator, and an input port for the circulator,
The millimeter wave radar according to claim 2, further comprising an output port and a control port between the input port and the output port. 4. The frequency conversion type pulse modulator has a small number of keys.
Use a switching element with a carrier lifetime of 10 ns or less
The millimeter wave radar according to claim 2, wherein the millimeter wave radar is a frequency conversion type pulse modulator . 5. A reception signal received by the reception antenna,
It includes a mixer that mixes with the signal modulated by the pulse modulator.
The millimeter wave radar according to claim 1, wherein the millimeter wave radar is provided. 6. A transmitting millimeter wave band signal reflected by the frequency conversion pulse modulator to the transmitting antenna, the frequency-varying
Den pulse modulated signal to the mixer in the replaceable pulse modulator
Millimeter wave radar according to claim 5 reaching means, characterized in that a band filter. 7. A millimeter waveband oscillator, a first NRD guide for guiding the output of the millimeter waveband oscillator to a first circulator, a pulse modulator connected to the first circulator, and the first circulator. A second NRD guide connecting the circulator and the second circulator, a third NRD guide connected to the second circulator, and the third NRD
A millimeter wave radar comprising a transmission / reception antenna connected to a guide and a mixer connected to the second circulator. 8. The frequency conversion type pulse modulator is an SBD.
(Schottky barrier Diode) and load resistance,
Depending on the state of the bias voltage, the millimeter wave response by the SBD
Characterized by pulse-like control of radiation and millimeter wave frequency conversion
The millimeter wave radar according to claim 1. 9. The frequency conversion type pulse modulator is an FET.
Alternatively, one of HEMT and load resistance is included, and F
State of bias voltage to either ET or HEMT
Depending on the condition, either the FET or the HEMT is used.
Controlling millimeter wave reflection and millimeter wave frequency conversion in a pulsed manner
The millimeter wave radar according to claim 1, wherein