JP2007327930A - Correlation detection device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To allow a phase at a front end of a waveform to use a random chirped pulse in a correlation detection device for detecting the correlation between the reflection signal from a target to a transmission signal with a chirped pulse in which one cycle is delayed and the chirped pulse. <P>SOLUTION: A reference FM pulse generator 3 produces reference FM pulses (chirped pulses) to supply the pulses to a fixed delayed circuit 5 and a rectangular detection circuit 11. Transmission pulses output from the fixed delayed circuit are transmitted from a transmission antenna 7 to a target TG, and then are reflected by the target TG and received by a receiving antenna 9. As a result, received pulses are produced. The received pulses are rectangularly detected by the reference FM pulses in the rectangular detection circuit 11, and thereby the rectangular detection components x, y are obtained. When the timing between the reference FM pulses and the received pulses, the square root of the squared-sum of the correlation components X, Y which are obtained by integrating the rectangular detection components x, y with integrators 13, 15 corresponds to the amplitude a of the received pulse. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a detection device such as a radar or a sonar, and more particularly to a correlation type detection device that obtains a required detection signal by correlating a transmission signal and a reception signal.

As shown in FIG. 8, a conventional general correlation detection apparatus includes a pulse generator 103 that generates a transmission pulse S ₁ (t) synchronized with a trigger pulse P ₁ generated by a trigger generator 101, and a pulse generator. A transmission antenna 105 that transmits the transmission pulse S ₁ (t) generated by the device 103 toward the target TG, a reception antenna 107 that receives a reflected wave from the target TG, and a trigger generator 101 A variable delay circuit 109 that delays the trigger pulse P ₁ by “τ” to generate a delayed trigger pulse P _2; and a pulse generator 111 that generates a reference pulse S ₂ (t−τ) synchronized with the output of the variable delay circuit 109; The multiplier 113 that multiplies the reflected pulse R ₁ (t) received by the receiving antenna 107 and the reference pulse S ₂ (t−τ) generated by the pulse generator 111, and the output of the multiplier 113 is integrated. And an integrator 115. In practice, a power amplifier, a noise removal filter, and the like are further provided, but only basic components necessary for explaining the operation principle are shown here.

The operation of this correlation type detection apparatus will be described with reference to the timing chart of FIG. The trigger pulse P ₁ having the period T ₀ generated by the trigger generator 101 is supplied to the pulse generator 103, and the delay trigger pulse P ₂ is supplied to the pulse generator 111 by the variable delay circuit 109. The delay time of the variable delay circuit 109 is extended by a fixed time ΔT from ₀ every period T ₀ of the trigger pulse P ₁ , and when it reaches NΔT (N is a predetermined integer), the delay time is again increased by 0 to ΔT. Repeat the extension operation. Here, ΔT is set to 1 / m (for example, 1/100) of the time length of the transmission pulse S ₁ (t), for example.

The pulse generator 103 generates a transmission pulse S ₁ (t) synchronized with the rising edge of the trigger pulse P ₁ , and the transmission pulse S ₁ (t) is transmitted from the transmission antenna 105 toward the target TG. The transmission pulse S ₁ (t) is reflected by the target TG and received by the reception antenna 107, and a reception pulse R ₁ (t) is generated. On the other hand, the pulse generator 111 generates a reference pulse S ₂ (t) synchronized with the rising edge of the delay trigger signal P ₂ . The received pulse R ₁ (t) and the reference pulse S ₂ (t−τ) are multiplied by a multiplier 113, and the output is integrated by an integrator 115, as shown in the following equation [1]. An integral output V ₀ is obtained. The integrator 115 can be replaced by an LPF (low pass filter).

This expression [1] represents the delay correlation, and takes the maximum value when the timing of the reception pulse R ₁ (t) coincides with the timing of the reference pulse S ₂ (t−τ). Therefore, when the delay of the timing of the reception pulse R ₁ (t) with respect to the timing of the transmission pulse S ₁ (t) is t ₀ ,
τ = t ₀ Formula [2]
In this case, the timings of the reception pulse R ₁ (t) and the reference pulse S ₂ (t) coincide, and the integral output V ₀ takes the maximum value.

Here, if the distance from the correlation type detector to the target TG is L, and the propagation speed of the radio wave is c,
_{L = c × t 0/2} ··· formula [3]
It becomes. In FIG. 9, τ = 3ΔT Equation [4]
In this case, the delay t ₀ (= 3ΔT) of the received pulse and τ coincide with each other. In FIG. 9, sinusoidal monopulses are shown as the transmission pulse S ₁ (t) and the reference pulse S ₂ (t−τ). As the waveforms of these pulses, a stepped frequency modulation format / linear frequency is used. Some use waveforms such as a modulation format, a code phase modulation format, and a code carrier modulation format.

  However, since this correlation type detection apparatus requires two pulse generators, the configuration becomes complicated and the apparatus becomes large. In addition, since the waveforms generated by the two pulse generators must be adjusted to be the same, there are problems such as not only the number of manufacturing steps but also aging.

Therefore, the inventor of the present application has proposed a correlation type detection apparatus that can solve such a problem (see Patent Document 1). The correlation-based detection system, as shown in FIG. 10, a trigger generator 201 that period (interval) to generate a variable trigger pulse P _11, the reference pulse S ₁₂ that is synchronized with the rising edge of the trigger pulse P ₁₁ (t- a pulse generator 203 that generates τ), a fixed delay circuit 205 that delays the reference pulse S ₁₂ (t−τ) by a predetermined time T ₀ to generate a transmission pulse S ₁₁ (t), and a transmission pulse S ₁₁ (t) Is transmitted to the target TG, a receiving antenna 209 that receives a reflected wave from the target TG, a reflected pulse R ₁₁ (t) received by the receiving antenna 209, and a reference pulse S ₁₂ ( A multiplier 211 that performs multiplication with t) and an integrator 213 that integrates the output of the multiplier 211 are provided. Here, τ in the reference pulse S ₁₂ (t−τ) is a time delay of the reference pulse S ₁₂ with respect to the transmission pulse S ₁₁ .

The operation of this correlation type detection apparatus will be described with reference to the timing chart of FIG. The period of the trigger pulse P ₁₁ generated by the trigger generator 201 is set to T ₀ as an initial value, extends by ΔT for each subsequent trigger pulse generation, and reaches the initial value again when reaching T ₀ + NΔT (N is a predetermined integer). It repeats extending from T ₀ by ΔT. Here, the initial value T ₀ is equal to the delay time of the fixed delay circuit 205. Similarly to FIG. 9, ΔT is set to 1 / m (eg, 1/100) of the time length of the transmission pulse S ₁₁ (t), for example.

The pulse generator 203 generates a reference pulse S ₁₂ (t−τ) synchronized with the rising edge of the trigger pulse P ₁₁ and supplies it to the fixed delay circuit 205 and the multiplier 211. The transmission pulse S ₁₁ (t) output from the fixed delay circuit 205 is transmitted from the transmission antenna 207 toward the target TG. Then, it is reflected by the target TG and received by the reception antenna 209, and a reception pulse R ₁₁ (t) is generated. The received pulse R ₁₁ (t) and the reference pulse S ₁₂ (t−τ) are multiplied by a multiplier 211, the output is integrated by an integrator 213, and the integrated output shown in the following equation [5] V ₁ is obtained.

This equation [5], like equation [1], represents the delay correlation, and the maximum value is obtained when the timing of the received pulse R ₁₁ (t) and the timing of the reference pulse S ₁₂ (t−τ) coincide. Therefore, the equations [2] and [3] are established as in the correlation type detection apparatus shown in FIG. FIG. 11 shows a case where equation [4] holds. Furthermore, although extended by ΔT the cycle of the trigger pulse P ₁₁ in FIG. 11 from T ₀ to T ₀ + n.DELTA.T, it may be reduced from T ₀ + n.DELTA.T until T ₀ by ΔT reversed.

According to this correlation type detection device, since only one pulse generator is required, the above-described problem of the general correlation type detection device can be solved. However, in this correlation type detector, the reference pulse S ₁₂ (t-τ) needs to have the same waveform every time, but a chirp pulse (linear frequency modulation wave) is adopted as the reference pulse S ₁₂ (t-τ). When doing so, there are the following problems.

When generating a chirp pulse, a VCO (Voltage Controlled Oscillator) is used as the pulse generator 203. A general VCO is the front end of an output signal when the operation is started or when the control voltage is changed discontinuously. 11 (hereinafter referred to as the initial phase) is not constant and changes randomly. Therefore, as shown in FIG. 11, when the reference pulse S ₁₂ (t-τ) is generated intermittently, In addition, the initial phase of the reference pulse S ₁₂ (t-τ) changes randomly. Therefore, for example, in FIG. 11, if the reference pulse S ₁₂ (t−τ) is a chirp pulse, the timing of the reference pulse S ₁₂ (t−τ) and the reflected pulse R ₁₂ ( Even if the timing of t) coincides, if there is a phase difference between these waveforms, the integrated output V ₁ becomes small according to the phase difference. For this reason, it cannot be said that the timing of the reference pulse S ₁₂ (t−τ) and the timing of the reflected pulse R ₁₂ (t) coincide with each other when the integrated output V ₁ becomes maximum.

In order to solve this problem, it is necessary to use a specially designed VCO that has a constant initial phase and obtains the same waveform every time as the pulse generator 203, so that the cost is high. There is a problem of becoming.
Japanese Patent No. 3182448

  The present invention has been made to solve such a problem, and an object of the present invention is to generate a plurality of reference waveforms having a predetermined time length so that a time interval periodically changes, and A means for generating a delayed waveform by delaying a reference waveform for a predetermined time; a means for transmitting a transmission signal corresponding to the delay waveform; and a reflected waveform or a transmitted wave from a target of the transmission signal to receive a received waveform In a correlation type detection device that obtains a required detection signal by taking a correlation between the generating means and the reference waveform and the received waveform, a waveform having a random front end can be used as the reference waveform. .

According to the first aspect of the present invention, there is provided means for generating a plurality of reference waveforms having a predetermined time length and having a random phase at the front end of the waveform so that the time interval changes periodically, and the reference waveform is determined in advance. Means for generating a delayed waveform by delaying time; means for transmitting a transmission signal corresponding to the delay waveform; means for receiving a reflected wave or transmitted wave from a target of the transmission signal and generating a received waveform; A correlation type comprising: means for quadrature detection of the received waveform using the reference waveform; and means for obtaining a detection signal irrelevant to the random phase based on the quadrature output component subjected to the quadrature detection. It is a detection device.
According to a second aspect of the present invention, in the correlation type detection apparatus according to the first aspect, the time length of the reference waveform also changes in accordance with the change of the time interval.
According to a third aspect of the present invention, in the correlation type detection device according to the first aspect, the reference waveform is a frequency modulation wave.

(Function)
According to the present invention, even if the phase of the front end of the reference waveform changes randomly, a detection signal irrelevant to the random phase can be obtained based on the orthogonal output component obtained by orthogonal detection of the received waveform using the reference waveform.

  According to the present invention, means for generating a plurality of reference waveforms having a predetermined time length so that the time interval changes periodically, means for generating a delayed waveform by delaying the reference waveform for a predetermined time, A means for transmitting a transmission signal corresponding to the delay waveform; a means for receiving a reflected wave or a transmitted wave from a target of the transmission signal to generate a reception waveform; and a correlation between the reference waveform and the reception waveform. In the correlation type detection apparatus that obtains a required detection signal by taking the waveform, a waveform having a random front end phase can be used as a reference waveform.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a block diagram showing a basic configuration of a correlation type detection apparatus according to an embodiment of the present invention. This correlation type detector includes a trigger generator 1 that generates a trigger pulse P ₂₁ having a variable period (interval), and a reference FM pulse S ₂₂ (t−) synchronized with the rising edge (or falling edge) of the trigger pulse P _21. FM wave generator 3 for generating τ), a fixed delay circuit 5 for delaying the reference FM pulse S ₂₂ (t−τ) by a certain time T ₀ and transmitting pulse S ₂₁ (t), and transmission pulse S ₂₁ ( a transmitting antenna 7 for transmitting t) toward the target TG, a receiving antenna 9 for receiving a reflected wave from the target TG, and a received pulse R ₂₁ (t) received by the receiving antenna 9 as a reference FM pulse S ₂₂ Quadrature detector 11 that performs quadrature detection by (t-τ), a pair of integrators 13 and 15 that integrate a pair of quadrature detection components of quadrature detector 11, respectively, and outputs 2 of the outputs of integrators 13 and 15. A pair of square calculation circuits 17 and 19 for calculating the power, and an adder 21 for adding the outputs of the square calculation circuits 17 and 19, And a square root calculating circuit 23 which calculates the square root of the sum of the adder 21. Here, the integrators 13 and 15 can be replaced by LPF. Further, τ of the reference FM pulse S ₂₂ (t−τ) is a time delay of the reference FM pulse S _{22 with} respect to the transmission pulse S ₂₁ as in the case of FIG.

Here, the trigger generator 1, the fixed delay circuit 5, the transmission antenna 7, and the reception antenna 9 have the same configuration as the means of the same name in FIG. Further, the FM wave generator 3 is constituted by a cascade connection circuit of a sawtooth wave generator 3a and a VCO 3b. Further, as shown in FIG. 2, the quadrature detector 11 includes a power distributor 31 that distributes the power of the reference FM pulse S ₂₂ (t), and a power distributor 33 that distributes the power of the received pulse R ₂₁ (t). The phase shifter 35 that shifts one of the power distributed by the power distributor 31 by 90 °, the other power distributed by the power distributor 31, and one of the power distributed by the power distributor 33. It comprises a multiplier 37 for multiplying, and a multiplier 39 for multiplying the output of the phase shifter 35 and the other of the power distributed by the power distributor 33.

The operation of this correlation type detection apparatus (FIG. 1) will be described with reference to the timing chart of FIG. The period of the trigger pulse P ₂₁ generated by the trigger generator 1 is set to T ₀ as an initial value, and is extended by ΔT for each subsequent pulse generation. When reaching T ₀ + NΔT (N is a predetermined integer), the initial value T is again reached. Repeat the extension from ₀ by ΔT. Here, the initial value T ₀ is equal to the delay time of the fixed delay circuit 5. Similarly to FIG. 9, ΔT is set to 1 / m (for example, 1/100) of the time length of the transmission pulse S ₂₁ (t), for example. In this embodiment, as will be described later, the reference FM pulse S ₂₂ (t−τ) is generated over the entire period from the trigger pulse P ₂₁ to the next trigger pulse P ₂₁ , and is shown in FIG. Compared to the case where only a part of the period from the trigger pulse P ₁ to the next trigger pulse P ₁ is generated, the energy efficiency can be improved.

Sawtooth generator 3a is fed to VCO3b generates a sawtooth wave that is synchronized to the rising edge of the trigger pulse P _21, VCO3b the reference FM pulse S ₂₂ (t having a frequency corresponding to the amplitude of the sawtooth wave -τ) is generated and supplied to the fixed delay circuit 5 and the quadrature detection circuit 11. The transmission pulse S ₂₁ (t) output from the fixed delay circuit is transmitted from the transmission antenna 7 toward the target TG. Then, it is reflected by the target TG and received by the receiving antenna 9, and a reception pulse R ₂₁ (t) is generated. The reception pulse R ₂₁ (t) is subjected to quadrature detection by the quadrature detector 11 with the reference FM pulse S ₂₂ (t−τ), thereby obtaining quadrature detection components x and y. Next, the quadrature detection components x and y are integrated by the integrators 13 and 15 to obtain correlation values X and Y.

The operation so far will be described in detail using mathematical expressions.
The reference FM pulse S ₂₂ (t−τ), the transmission pulse S ₂₁ (t), and the reception pulse R ₂₁ (t) are represented by the following equations [6], [7], and [8], respectively. However, in these equations, for the sake of convenience, the amplitude of the reception pulse R ₂₁ (t) is “a”, and the other amplitudes are “1”.
S ₂₂ (t−τ) = cosφ ₂ (t−τ) (6)
S ₂₁ (t) = cosφ ₁ (t) Expression [7]
R ₂₁ (t) = acosφ ₁ (t−τ ₀ ) Equation [8]

“Τ ₀ ” in Expression [8] is a time difference between the direct wave and the reflected wave, and corresponds to the distance L from the correlation type detection device to the target TG. The sign of the transmission pulse S ₂₁ (t) and the reference FM pulse S ₂₂ (t−τ) is distinguished as “φ ₁ ” and “φ ₂ ” because the transmission pulse S ₂₁ (t) is one cycle. This is because it corresponds to the previous reference FM pulse S ₂₂ (t−τ) and the initial phase is randomly different.

In the received pulse R ₂₁ (t), the amount to be obtained is τ ₀ and a, and therefore, the correlation with the reference pulse S ₂₂ (t−τ) is taken. First, since the output x of the multiplier 37 of the quadrature detector 11 is a value obtained by multiplying S ₂₂ (t−τ) and R ₂₁ (t), the following equation [9] is obtained, and the output of the multiplier 39 is S _{Since 22} (t−τ) is a value obtained by multiplying a signal (= sinφ ₂ (t−τ)) 90 ° phase-shifted and R ₂₁ (t), the following equation [10] is obtained.
x = (a / 2) [cos {φ ₁ (t−τ ₀ ) −φ ₂ (t−τ)} + cos {φ ₁ (t−τ ₀ ) + φ ₂ (t−τ)}] Equation [9]
y = (a / 2) [sin {φ ₁ (t−τ ₀ ) −φ ₂ (t−τ)} + sin {φ ₁ (t−τ ₀ ) + φ ₂ (t−τ)}} [Ten]

By integrating the quadrature detection outputs x and y by the integrators 13 and 15, the second terms of the equations [9] and [10] disappear, so that the outputs X and Y of the integrators 13 and 15 are X = (a / 2) cos {φ ₁ (t−τ ₀ ) −φ ₂ (t−τ)} Expression [11]
Y = (a / 2) sin {φ ₁ (t−τ ₀ ) −φ ₂ (t−τ)} Expression [12]
It becomes.

Here, as shown in FIG. 4, when the frequency f of the reference FM pulse S ₂₂ (t−τ) is repeatedly swept up from the frequency f ₀ to f ₀ + B during the time T,
f (t) = {(B / T) t + f ₀ } Expression [13]
Therefore, the angular frequency ω (t) is given by ω (t) = 2πf (t) = 2π {(B / T) t + f ₀ } Equation [14]
Therefore, the phase φ (t) is expressed by the following equation [15].

Here, θ is a random initial phase. Therefore,
φ ₁ (t−τ ₀ ) = 2π {(B / 2T) (t−τ ₀ ) ² + f ₀ (t−τ ₀ )} + θ ₁ Formula [16]
φ ₂ (t−τ) = 2π {(B / 2T) (t−τ) ² + f ₀ (t−τ)} + θ ₂ Formula [17]
It becomes.

Now, when the delay time τ of the reference FM pulse matches the delay time τ _{0 of the} received pulse,
τ = τ ₀ Formula [18]
φ ₁ (t−τ ₀ ) −φ ₂ (t−τ) = θ ₁ −θ ₂ = θr Equation [19]
Since θ ₁ and θ ₂ are random, θr is also random. In the case of FIG. 3, the timing of the nth reference FM pulse matches the timing of the (n−1) th received pulse. Here, although the length of the FM pulse differs by ΔT between S ₂₁ and R ₂₁ , ΔT is sufficiently smaller than T ₀ and can be ignored.

Substituting equation [19] into equations [11] and [12], X = (a / 2) cosθr... Equation [20]
Y = (a / 2) sinθr Expression [21]
It becomes.

As described above, the outputs X and Y of the integrators 13 and 15 are irrelevant to the frequency of the reference FM pulse, and have values that change depending on the random phase difference θr. Then, when the outputs X and Y of the integrators 13 and 15 are squared by the square calculation circuits 17 and 19 and added by the adder 21, the added value is X ² + Y ² = (a / 2) ² {cos ² θr + sin ² θr} = (a / 2) ² Formula [22]
Thus, the randomly changing phase difference θr disappears. Therefore, since the output of the square root calculation circuit 23 is (a / 2), “a” is obtained.

As described above, according to the correlation detection device of the present embodiment, the received pulse R ₂₁ (t) is quadrature detected by the reference FM pulse S ₂₂ (t−τ), and the quadrature detection components x and y are integrated. By calculating the sum of squares and further calculating the square root, a required detection signal can be obtained even using a general VCO 3b whose initial phase changes randomly. Further, according to the correlation type detection device of the present embodiment, the reference FM pulse S ₂₂ (t−τ) is generated over the entire period from the trigger pulse P ₂₁ to the next trigger pulse P _21. High energy efficiency. In the above description, a chirp pulse (linear frequency modulation wave) is generated by the VCO 3b based on the output waveform of the sawtooth wave generator 3a. However, a staircase wave is generated instead of the sawtooth wave generator 3a. By using a waveform generator having an arbitrary shape with respect to time and amplitude characteristics such as a sine wave generator and a sine wave generator, a frequency modulation wave with arbitrary time to frequency characteristics such as a stepped frequency modulation format and a sine wave frequency modulation format from the VCO 3b. May be generated.

[First embodiment]
FIG. 5 is a block diagram of a millimeter wave radar which is a first embodiment of a correlation type detection apparatus according to the present invention. In this figure, the same reference numerals as those in FIG.

This millimeter wave radar includes a PC (personal computer) 51 having a function of generating a trigger pulse P ₂₁ and a function of calculating a sum of squares of an integral value of quadrature detection output and a function of calculating a square root thereof. The VCO 3b oscillates at a frequency near 76 GHz. The output of the VCO 3b is distributed to the isolator 55 and the mixer 61 by the coupler 53. A transmission pulse that is an output of the isolator 55 is transmitted from the transmission antenna 7 toward a target (not shown). The reflected wave from the target is received by the receiving antenna 9 to become a received pulse, amplified by the high frequency amplifier 65, and input to the mixer 67. The output of the 76.5 GHz local oscillator 57 is supplied to the mixer 67 through the power distributor 59, and the received pulse carrier wave is converted to an intermediate frequency of 500 MHz. The output of the mixer 67 is amplified by the intermediate frequency amplifier 71, delayed by a fixed time (6.8 μsec) by the delay line 5, and then input to the quadrature detector 11.

  The output of the local oscillator 57 is also supplied to the mixer 61 through the power distributor 59, where it is mixed with the reference pulse from the coupler 53 and converted to an intermediate frequency of 500 MHz. The output of the mixer 61 is amplified by the intermediate frequency amplifier 63 and input to the quadrature detector 11.

  In the quadrature detector 11, the quadrature detection components x and y are calculated by the operation described with reference to FIGS. 2 and 3, and the quadrature detection components x and y are amplified by the amplifiers 73 and 75, and the low pass filter (LPF). Only the low frequency components 13 and 15 are extracted, and the output is input to the PC 51. The PC 51 calculates the sum of squares of the input signal and its square root.

  FIG. 6 shows an actual measurement value of an echo signal from a transmission line (a stranded wire having a diameter of 3 cm) 798 m ahead detected by the millimeter wave radar of FIG. 5 and can be detected very clearly.

[Second Embodiment]
FIG. 7 is a block diagram of an underground exploration radar which is a second embodiment of the correlation type detection apparatus according to the present invention. In this figure, the same or corresponding elements as those in FIG. This underground exploration radar also includes a PC 51, amplifiers 73 and 75, and LPFs 13 and 15 as in the millimeter wave radar shown in FIG.

  When an extremely wide-band radar signal is handled like a ground penetrating radar, it is technically difficult to realize a wide-band quadrature detector, so that the quadrature detector 11 is fixed by configuring as shown in FIG. The one corresponding to the frequency (here 1.2 GHz) is sufficient.

  In this subsurface radar, the VCO 3b generates an FM pulse of 1.3 to 1.8 GHz, and the local oscillator 57 generates a sine wave of 1.2 GHz. The output of the VCO 3b is distributed to the mixers 67 and 81 by the power distributor 59, and the output of the local oscillator 57 is distributed to the mixer 81 and the quadrature detector 11 by the coupler 53. In the mixer 81, the output of the VCO 3b and the output of the local oscillator 57 are mixed, and the output is supplied to a BPF (band pass filter) 83 having a pass band of 100 to 600 MHz. In the BPF 83, the output of the VCO 3b and the transmission pulse of 100 to 600 MHz, which is the beat frequency component of the local oscillator 57, are extracted, and the transmission pulse is transmitted from the transmission antenna 7 toward the target (not shown) through the delay line 5. Is done.

  The reflected wave from the target is received by the receiving antenna 9 to become a received pulse, amplified by the high frequency amplifier 65, and input to the mixer 67. In the mixer 67, the received pulse and the output of the VCO 3b are mixed, and the output is supplied to the BPF 85 whose center passband is 1.2 GHz. The BPF 85 extracts a 1.2 GHz signal that is a beat frequency component of the received pulse and the output of the VCO 3b, thereby obtaining a received pulse frequency-converted to 1.2 GHz. This received pulse is input to the quadrature detector 11 and quadrature detected by the output of the local oscillator 57 supplied to the quadrature detector 11 through the coupler 53.

  As described above, according to the present embodiment, the positions of the VCO 3b and the local oscillator 57 are changed with respect to FIG. Become. The delay line 5 may be connected between the mixer 81 and the BPF 83, between the reception antenna 9 and the high frequency amplifier 65, or between the high frequency amplifier 65 and the mixer 67.

It is a block diagram which shows the basic composition of the correlation type detection apparatus of embodiment of this invention. It is a block diagram which shows the structure of the quadrature detector in FIG. It is a timing chart which shows operation | movement of the correlation type detection apparatus of embodiment of this invention. It is a figure which shows the correspondence of the time and frequency of a reference | standard FM pulse in embodiment of this invention. 1 is a block diagram of a millimeter wave radar that is a first embodiment of a correlation type detection apparatus according to the present invention; FIG. It is a figure which shows the measured value of the echo signal from the 798-m ahead transmission line (twisted pair wire with a wire diameter of 3 cm) detected with the millimeter wave radar of FIG. It is a block diagram of the underground exploration radar which is 2nd Example of the correlation type detection apparatus which concerns on this invention. It is a block diagram which shows the basic composition of the conventional common correlation type detection apparatus. It is a timing chart which shows operation | movement of the correlation type detection apparatus shown in FIG. It is a block diagram which shows the basic composition of the correlation type detection apparatus which reduced the pulse generator. It is a timing chart which shows operation | movement of the correlation type detection apparatus shown in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Trigger generator, 3 ... Reference | standard FM pulse generator, 5 ... Fixed delay circuit, 7 ... Transmitting antenna, 9 ... Receiving antenna, 11 ... Quadrature detector, 13, 15 ... integrator, 17, 19 ... square calculation circuit, 21 ... adder, 23 ... square root calculation circuit.

Claims (3)

  Means for generating a plurality of reference waveforms having a predetermined time length and having a random phase at the front end of the waveform so that the time interval changes periodically; and delaying the reference waveform by a predetermined time Means for generating, means for transmitting a transmission signal corresponding to the delayed waveform, means for receiving a reflected wave or transmitted wave from a target of the transmission signal and generating a received waveform, and the received waveform as the reference A correlation type detection apparatus comprising: means for performing quadrature detection based on a waveform; and means for obtaining a detection signal irrelevant to the random phase based on the quadrature output component subjected to quadrature detection. The correlation type detection apparatus according to claim 1,
The correlation type detecting apparatus according to claim 1, wherein a time length of the reference waveform changes according to a change in the time interval. The correlation type detection apparatus according to claim 1,
5. The correlation type detection apparatus according to claim 1, wherein the reference waveform is a frequency modulation wave.

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