JPS62108176A - Radar equipment - Google Patents

Abstract

PURPOSE:To highly precisely measure the range to a target body the relative speed to the target body which appears at a very near range and moves slowly, by providing a transmitter, a waveguide, a variable attenuator, etc. CONSTITUTION:Transmitted 1a RF power is passed from the terminal 1 to terminal 2 of a directional coupler 3a and from the terminal 1 to terminal 2 of a circulator 4a and radiated 5a. The radiated 5a RF power is reflected by a corner reflector 9 and part of the reflected RF power is received by a radiator 5a. The power is variable-attenuated 10a and applied to coaxial/ waveguide conversion 7a' through a unilateral tube 6a'. The received power is again applied to coaxial/waveguide conversion 7a when passing through a waveguide 8a and absorbed by the next unilateral tube 6a. On the other hand, the transmitted 1b RF power advances from the terminal 1 to terminal 2 of a coupler 3b. Moreover, an electric-field standing wave is produced by the progressive wave from the unilateral tube 6b side and reflected wave from the unilateral tube 6a side in a waveguide 8b. Then the distance to a target is found in the unit of 1/2 wavelength in accordance with the standing wave and, at the same time, the moving speed of the target can be found from the produced cycle of the trough of a standing wave.

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention relates to a radar device that measures with high precision the distance and relative speed to a target object that is close and whose distance is slowly changing. .

[Conventional technology]

Conventionally, in order to measure the distance to a target at close range, a pulse radar with an extremely small transmission pulse width was used to measure the round trip time of the pulse to the eyes, face, and body in order to reduce the period of no reception caused by strong leakage power. The method used was to measure the frequency difference between transmitted and transmitted signals using an FM-CW radar, similar to a radio altimeter. On the other hand, pulse radar measures the relative velocity of a target object by measuring the Doppler shift of the carrier frequency.

[Problem to be solved by the invention] However, with pulse radar, even if the transmission pulse width is reduced, distance measurement is only possible within 2 to 3 nSec at most, taking into account the recovery time of one receiving circuit. It is quite difficult to reduce the shortest distance to 1 m or less.

Even with FM-CW radar, the frequency measurement accuracy is limited to a few tens of cnL at most. In addition, the distance measurement accuracy is several tens of cIrL due to various error causes.
It is considerably difficult to do the following t'i. Besides, F.M.
-CW Measuring the relative velocity of a target object using radar is extremely difficult in principle.

In this way, the conventional technology has problems such as the inability to reduce the shortest distance that can be measured, the inability to obtain high distance measurement accuracy, and the difficulty in measuring relative velocity with FM CW radar. This invention attempts to solve this difficult problem.

[Means to solve all problems]

A transmitter that transmits CWO waves at two different frequencies; a waveguide that causes the radio waves transmitted by the transmitter to interfere with the received radio waves that are reflected from the target object and returns; and a waveguide that generates an electric field standing wave. The electric field standing wave generated by this waveguide is
Zero point detection that detects each type of frequency to obtain two video outputs with different temporal changes and detects the point where the difference between these two video outputs becomes zero when one frequency is gradually separated from the other. A circuit, a pulse timing circuit that measures the trough (zero point) of the electric field settled wave obtained when two types of frequencies are fixed, and this timing and the zero point detection: distance to the target object and movement of the target object. It is equipped with an arithmetic circuit that calculates speed.

[Effect J: The video voltage of the difference between the two measured video outputs is 2 when one wavelength is fixed and the other wavelength is gradually separated.
Due to the difference in the temporal changes of the two video outputs, the video voltage of the difference becomes zero at a certain wavelength corresponding to the distance from the measuring point of the electric field standing wave to the target. Therefore, the distance can be calculated from the wavelength at this time.

Next, the two video voltages change periodically due to the movement of the standing wave as the target object moves.

By measuring the rate of change, the relative speed of the target can be determined.

〔Example〕

FIG. 1 shows an embodiment of the invention. In the figure (1a)
*(Ie) is the wavelength λ1. λ2 transmitter, (1
b) is an FM transmitter whose wavelength gradually increases from λ1 to several λ1 and repeats this; (2) is a high frequency switch +
(3a).

(3b) is a directional coupler, (4a) + (4b) is a circulator + (5a), (5b) is a radiator with mutually orthogonal polarization planes, (6a), (63'), (6b) , (6
b') is an isolator, (7a).

(7a'), (7b), (7b') are coaxial/waveguide converters with built-in buffer resistors, (8a),
(8b) has a length ratio.

A waveguide made to have an internal wavelength ratio equal to λ1Tλ2, (9) a corner reflector attached to the surface of a moving target, (10a) and (10b) automatic reflection according to the distance to the target. Attenuation! Variable attenuator that changes k and maintains t received power almost constant* (11a)+
(11b) is inserted into the waveguides (8a) and (8b), and the probe + (12a
)+ (12b) is a detector.

(i3a) + (13b) is a video amplifier, (14
a), (14b) are changeover switches, α1 is a subtraction circuit tu
e is a zero point detection circuit, (17a) and (17b) are saturation amplifiers, and aS is a pulse timing circuit.

It is a calculation circuit for distance and speed. In addition, the RF' circuit between A-A' and B-B' in Figure 2 is a waveguide (8a) and (8b).
All except for 1 are composed of coaxial circuit components.

From the transmitter (1aX or (1b)) to the glove (11
a) up to (11b), and probe (11a)
) (or (11b)) to the radiator (5aX or U (
The electrical length up to 5b)) is A (or B) because it is simple.
from C (tfc is D) and from C (or D) to A
' (or B') are equal to the electrical lengths 11 and 12, respectively.

Now, the RF power of wavelength λ1 transmitted from the transmitter (1a) is passed from terminals 1 to 2 of the directional coupler (3a) to terminals 1 to 2 of the circulator (4a), and the RF power of the radiator (5
a) is radiated into the air. on the other hand! Directional coupler (3a
), and a portion of the RF power appearing at terminal 3 passes through the isolator (6a) to the coaxial/waveguide converter (7a).
), and after passing through the waveguide (8a), it is converted back into a coaxial mode by the coaxial/waveguide converter (7a) and absorbed by the next isolator (6a').

The RF power radiated from the radiator (5a) is reflected by the corner reflector (9), and part of it is received by the radiator (5a). The received power goes from terminal 2 to terminal 3 of the circulator (4a), is attenuated to an appropriate value by a variable attenuator (1Oa), passes through an isolator (6a'), and is guided by a coaxial/waveguide converter (7a'). Converted to tube mode.

When the received power converted to the waveguide mode passes through the waveguide (8a), it is converted back to the coaxial mode by the coaxial/waveguide converter (7a) and absorbed by the secondary isolator (6a). By the way, a part (traveling wave) of the transmitted power entering the waveguide (8a) from the isolator (6a) side
An electric field standing wave is generated by the isolator (6a'J) and the received power (reflected wave).Now, a variable attenuator is installed so that the intensity of the reflected wave is sufficiently small compared to the intensity of the traveling wave. Assuming that the amount of attenuation (10a) is given, this electric field standing wave 1Eal is 1Eal= ka (1+αasinβIJ)
(11 However, +ka + αa is a constant, αa (1, β
1 = 2π/λ1゜1 = h + Is If the electric field is picked up by the globe (11a), detected by the detector (12a), and amplified by the video amplifier (13a), λ1 changes as l changes. A voltage that changes sinusoidally with a period of /2 is obtained (Figure 2).

On the other hand, the RF power transmitted from the transmitter 1 (1b) passes through terminals 1 to 3 of the p high frequency switch (2) to the directional coupler (
3b) terminals 1 to 2 are the same as the A system, and there is an isolator (6b) in the waveguide (8b).
An electric field standing wave is generated by the traveling wave that enters from the b) side and the reflected wave that enters from the isolator (6b) side. This 'electric field standing wave (6) bl is IEbl = k
b (1+αhain2βg) +21
However, kbsαb is a constant, αb(1, β=2π/λ.

1=lz+ls, and a voltage that changes sinusoidally with a period of λ/2 as l changes is obtained at the output end of the video amplifier (151) (FIG. 2).

Now, assuming that the circuit is designed and adjusted so that both the traveling wave and the reflected wave have the same intensity in the A system and the B system, then in the first and second equations, ka =
kb *αa=αb. Therefore, in such a state, if the outputs of the video amplifiers (13a) and (13b) are respectively led to the subtraction circuit α9 through terminals 3 and 2 of the switches (14a) + (14b), the output terminal has E(λ). 〆th (r+β)AI blood (bar β)/(An output of 31 is obtained (Fig. 2). Therefore, λ is gradually increased from λ1.

When E(λ) reaches zero, if this is detected by the t-th zero point detection circuit aQ, then from λ at this time, E(λ) becomes zero in the arithmetic circuit α. +
15=l −1h, Eri, radiator (5a).

(5b), the distance to the corner reflector (9) of the target object can be determined.

Second, high frequency switch (2) and selector switch (1)
4a) and (14b) are switched to the arrow side, and at the same time the attenuation 21 of the variable attenuators (10a) and (10b'') is reduced so that the intensity of the traveling wave and the intensity of the reflected wave become almost equal.

Electric field standing wave IEa'1- in waveguides (8a) and (8b)
IEb'l is IE a'lx k a"pkβ111
(5) Ig b'l= kb'1g
1n /211 (6) However, k
a'+k b' is a constant, β1=2r/λ1. β2−
2π/λ2, the electric field is picked up by the probes (11a) and (11b), and the detectors (12a) and (12b)
The signal is detected by the video amplifier (13a) + (13
If amplified in b), the trough (zero point) of the standing wave will change as l changes.
are respectively λ1/2. A voltage that is repeated at a period of λ2/2 is obtained.

These are connected via the terminals 3 to 1 of the switch (14a) and (14b) to the saturation amplifier (17a) and (1
7b), the target object is 1/2 at these output terminals.
Every time the wavelength is shifted, a spike-like output voltage is generated such that the tortoise pressure value decreases to near zero once (FIG. 2).

If λ2 is set to be 1, for example, 5 inches larger than λ1, a spike voltage will occur 19 times in the B system while it occurs 20 times in the A system.

That is, spike-like voltages occur in the A system and the B system at the same time every 2G (λ1/2)=19 (λ2/2). Therefore, the secondary pulse timing circuit α barrel measures the times at which spike-like voltages are generated in the A system and the B system, and determines the time at which both coincide. When both agree! =10λI X n (
71 However, since it is clear that n is expressed as a positive integer, the first-order arithmetic circuit α1
2, and compare the value of l obtained based on formula 1 + 41 with lf of formula (7) to find the value of n, and calculate the number of spike-like voltages that occur over the course of one hour from system A (or system B).
system) and multiplying that number by λ1/2 (or λ2/2) to find the instantaneous distance of the target object in units of 1/2 wavelength. Also, the moving speed of the target object is determined from one cycle of repetition of the t-spike voltage.

However, the determination of whether they are approaching or separating is based on equation (4).
1 for each measurement data of several times.

〔Effect of the invention〕

According to this invention, 2f4! The distance to the target object can be determined in units of 172 wavelengths based on the electric field standing waves obtained for similar frequencies, and the moving speed of the target object can be determined from the period of occurrence of the troughs of the standing waves, resulting in high accuracy. It is possible to provide a close-range radar that requires distance measurement and low-velocity detection.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing one embodiment of the present invention. FIG. 2 is a diagram showing an explanation of the operation. The diagrams of lE, I, IEbl, and E(λ) are based on equations 111 and 12). and the third
) is a drawing of the formula. In the figure (1a), (1c) t! Each wavelength λ1. λ2
transmitter. (1b) is an FM transmitter whose wavelength changes continuously from λ1 *(8a), (8b) are waveguides, (10a) t
QOb) is a variable attenuator + (11a), (11b
) is a detector* QS is a subtraction circuit Iαe is a zero point detection circuit,
α・ is a pulse timing circuit, (11 is an arithmetic circuit. In the figures, the same reference numerals indicate the same or equivalent parts.

Claims (1)

[Claims] A transmitter that transmits CW radio waves of two types of frequencies, and these two
Two waveguides that generate an electric field standing wave by interfering with a part of the transmitted wave (progressive wave) and the received wave (reflected wave) for each type of frequency, and these two types of electric field standing waves. a subtraction circuit that obtains the difference between the two video outputs detected by the detectors, a variable attenuator that adjusts the intensity of the received waves, and a subtraction circuit that detects one of the two types of frequencies from the other. A zero point detection circuit that detects the zero point of the output of the subtraction circuit obtained when the frequency is gradually separated from , and a trough (zero point) of the electric field standing wave obtained when both of the two types of frequencies are fixed. It comprises a pulse timing circuit, and an arithmetic circuit that calculates the distance to the target object and the moving speed of the target object in units of 1/2 wavelength by the timing of the pulse timing circuit and the zero point detection of the zero point detection circuit. A radar device.