JPH1090393A - Signal detector pulse-width continuously variable correlation - Google Patents

Abstract

PROBLEM TO BE SOLVED: To respectively improve the distance resolution and sensitivity of a correlation signal detector at short and long distances by widening the pulse width of a prearranged waveform signal wherever a prescribed period is repeated. SOLUTION: A variable pulse width generating circuit 4 outputs a variable period trigger signal 2A having a variable period TE as a prearranged waveform signal 3A, the pulse width of which is successively widened at every period, and a multiplication circuit 14 inputs a shaped and amplified 15 correlation signal 15A. In addition, a power amplifier circuit 6 inputs a fixed delay signal 5A which is obtained by delaying 5 the output of the circuit 4 by a fixed delaying amount DF and the prearranged waveform signal delayed by the amount FD is transmitted to a transmission antenna while the period is successively elongated by t at every variable period TE of the trigger signal 2A with transmitting signal 6A. Therefore, the receiving signal 13A obtained by a reception antenna 12 signals received from objects 9A and 9B buried underground is delayed from the correlation signal 15A by the amount FD and a multiplication signal 14A and search signal 17A become a search signal subjected to correlation detecting processing and equivalent processing. Therefore, when the distance is short (long), a correlation detected signal having a narrow (wide) pulse with and high distance resolution (sensitivity) is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in a correlation type signal detection apparatus for obtaining a required detection signal by correlating with a received signal using a promised waveform at the time of transmission.

[0002]

2. Description of the Related Art Conventional types of such devices include a reflection type signal detection device and a transmission type signal detection device. Underwater and aerial objects using sound waves or ultrasonic reflected waves, such as marine radars that detect relative distance conditions and underground survey radars that detect the status of buried objects under the ground surface, geological changes, relative distance conditions, etc. There are fish finder and sonar etc. that detect the situation, relative distance situation, etc. As the transmission type signal detection device, the buried object condition in the underground route between the required points by the transmitted wave of the radio wave (also called the passing wave)
There are transmission / reception opposing detection radars and borehole radars that detect a stratum change or the like by transmitted waves, and transmission / reception opposing detection sonars that detect underwater objects and aerial objects using transmitted waves of sound waves or ultrasonic waves.

In this type of signal detection device, the configuration of a correlation function used to increase the signal detection capability is as follows:
A method is mainly used in which a correlation with a reception signal obtained in each signal detection cycle is superimposed a plurality of times to obtain a detection signal.

However, in order to obtain an effective correlation result, a waveform having a specific promise (referred to as a promised waveform in the present invention) is transmitted as a transmission waveform, and is obtained by a reflected wave or a transmitted wave. The received signal is used as the correlated signal, and the signal obtained by delaying the promised waveform by a small amount of time in each signal detection cycle is used as the correlation signal, and the correlation is obtained.
It is conceivable to adopt a configuration in which a signal due to interference interference or environmental noise is removed, and a detection signal with a good S / N is obtained from a weak reception signal with a bad S / N. Even if the value is reduced, the detection distance can be increased.

[0005] As the promised waveform, a specific promise can be used for amplitude change, period change, phase change, number of pulses, pulse interval, and the like. There is a waveform in a pulse format, and a waveform with a complicated promise is a waveform in a stepped frequency modulation format, a linear frequency modulation format, a code phase modulation format, a code carrier modulation format, or the like.

Japanese Patent Application Nos. 4-76155 and 4-111554 have filed applications for a correlation-type signal detection device provided with such a function of detecting a correlation signal using a promised waveform.
8. Japanese Patent Application Nos. 4-120034 and 4-1487
There are 63.

[0007]

In the conventional correlation type signal detection apparatus, Japanese Patent Application Nos. 4-76155 and 4-1 have been disclosed.
15548, Japanese Patent Application No. 4-120034 and Japanese Patent Application No. Hei 4-124
As described in 148873, the signal detection is performed by changing the promised waveform to a variable period, or using the received signal including the promised waveform as a correlated signal, and multiplying the transmission signal by a fixed delay correlation signal to obtain a signal. Efficient with a simple configuration.

[0008] In this state, short-distance portions and long-distance portions are always performed with the same resolution and detection capability, and ultimately cannot be said to have ideal performance.
If possible, the sensitivity is sufficient at short distances.
Rather, it is better to increase the sensitivity and to increase the sensitivity at long distances in order to increase the detection capability even at the expense of resolution.

[0009]

SUMMARY OF THE INVENTION The present invention relates to the present invention as described in Japanese Patent Application Nos. 4-76155, 4-115548, 4--120034 and 4-148763. Upon obtaining a required detection signal by correlating a reception signal obtained by transmitting a transmission signal using a promised waveform signal that repeats at a predetermined cycle with a correlation signal using the promised waveform signal, In the detection signal device in which the period of the signal is extended or shortened, and either the transmission signal or the correlation signal is delayed by a predetermined fixed delay amount to obtain the detection signal, the pulse width of the promised waveform signal is Each time it is repeated at a predetermined cycle, it is sequentially expanded.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment will be described below with reference to FIG. 2 of the first embodiment. The first embodiment shown in FIG. 2 is an underground radar for exploring the ground from the air, and has the simplest promise of a one-cycle waveform as shown in FIG. The configuration is such that the correlation is obtained as a waveform, and the signals of each section are shown in FIG.

A variable period trigger signal having a variable period TE sequentially extended by a small amount of time Δt at each time of the period by a variable period trigger generation circuit 2 in which the generation period of the trigger changes with the voltage of the trigger period control signal circuit 1 2A, and this variable period trigger signal 2A is applied to a pulse width control signal generation circuit 3, and the pulse width generated by the pulse width variable pulse generation circuit 4 is sequentially reduced by a small amount Δρ at each time of the period. Promised waveform signal 3A with expanded pulse width
Create

Therefore, for example, when the initial pulse width is 2 ns, the pulse width of the promised waveform signal 3A is sequentially increased and the final period is set to 6 ns. To decide.

The variable period trigger generation circuit 2 has, for example, Δ
This is a pulse generation circuit combining a clock circuit of t and a counting circuit. When T = Δt × n is set as an initial value, n is a fixed amount and n + 1, n + 2, n + 3,.
r, n + (r + 1), n + (r + 2),... n + (n−
2) Counting up to n + (n-1) and n + n, and obtaining a cycle of each time, generates a pulse signal of a variable cycle that sequentially extends by a small amount of time Δt within a period of T to (T + Δt × n). Δt is 1 / m of TPX which is the time length of the promised waveform signal 3A, for example, 1
/ 10.

The output of the variable pulse width pulse generation circuit 4 is
As shown in FIG. 3, for example, the pulse width control signal generation circuit 3 first sets the time length of the promised waveform signal 3A to TP.
X, and the cycle of the variable cycle trigger signal 2A is T
+ Δt × 1, the time length of the promised waveform signal 3A is T
PX + Δρ × 1 and the next cycle is T + Δt × 2
, The time length of the promised waveform signal 3A is represented by TPX + Δρ ×
The pulse width is sequentially increased by Δρ in each cycle of the period.

FIG. 5 (a) shows a situation where the pulse width of the variable pulse width pulse generating circuit 4 is variable. Usually, for example, a line is varied linearly from 2 ns to 6 ns like a straight line a. Depending on the case, it is also possible to change and use the convex curve b or the concave curve c according to each detection purpose.

Further, as shown in FIG.
Steps from s to 6 ns may be changed stepwise.

FIG. 5C illustrates the effect of changing the pulse width of the variable pulse width pulse generating circuit 4 as shown in FIGS. 5A and 5A. Considering this, at the beginning of the variable period of the variable period trigger generation circuit 2, a good resolution can be obtained because the pulse width generated by the pulse width variable pulse generation circuit 4 is narrow, and at a long distance, the variable trigger generation circuit 2 Indicate that the pulse width becomes wider as the variable period advances, so that good sensitivity can be obtained.

The correlation signal circuit 15 shapes or amplifies the promised waveform signal 3A generated by the variable pulse width pulse generation circuit 4 into a predetermined waveform, or the like, and correlates the correlation signal 15A.
Is output and given to one multiplication input of the multiplication circuit 14.

The fixed delay circuit 5 is a circuit for delaying the output of the variable pulse width pulse generation circuit 4 by a predetermined fixed delay amount FD, and is, for example, a delay circuit using a coaxial line or the like. The power is supplied to the power amplification circuit 6.

In the case of the first embodiment shown in FIG. 2, the fixed delay amount of the fixed delay circuit 5 is set to a fixed delay amount FD corresponding to one period of the initial period T of the variable period trigger generation circuit 2. is there. Therefore, the fixed delay signal 5A provided to the power amplifier circuit 6 is such that the promised waveform signal 3A is always delayed by the same fixed delay amount FD as the initial period T for each variable period TE.

The correlation signal 15A applied to one input of the multiplication circuit 14 does not receive the fixed delay amount FD.
Appears without delay for each E.

That is, the transmission signal 6A is a promised waveform obtained by delaying the variable trigger signal 2A by the fixed delay amount FD, which is the same as the initial period T, while sequentially extending the period by Δt at each time of the variable period TE of the variable trigger signal 2A. Signal of transmitting antenna 7
The received signal 13A (noise signal is omitted) obtained from the received signal 12A received by the receiving antenna 12 similarly appears as a signal delayed by Δt each time, For signal 15A,
This means that the delay is always delayed by the same fixed delay amount FD as the initial period T.

Therefore, the promised waveform signal 3A applied to one input side of the multiplication circuit 14, that is, the correlation signal 15
As viewed from A, the received signal 13A given as a correlated signal to the input of the other multiplication circuit 14 becomes a signal delayed by a time corresponding to the initial period T for each of the variable periods TE. 15A of the second and subsequent correlation signals
Are successively delayed by Δt, and the received signal 13A is received at the time sequentially advanced by Δt at each time of the variable period TE.
A for the promised waveform signal 2A, the underground objects 9A and 9B
Of the received signals 9a and 9b appear at times sequentially shifted up by Δt.

For this reason, the multiplication signal 14A corresponds to the reception signal 1
The correlation signal 15A has a variable period TE with respect to 3A, that is,
Since it is obtained as a signal of an amplitude value obtained by multiplying the amplitude value of each signal while being shifted backward by Δt for each detection cycle, the multiplication signal 14A and the detection signal 17A are eventually
A detection signal that has undergone processing equivalent to the correlation detection processing is obtained.

In this case, the detection signal 17A is obtained from the output of the multiplying circuit 14 through the integrating circuit 16 and the sample holding circuit 17, but is replaced by a low-pass filter or the like instead of the integrating circuit 16 and the sample holding circuit 17. Alternately, a similar result is obtained.

For example, when the variable period TE becomes twice as long as the first fixed period T, the correlation detection processing for the detection distance range corresponding to the first fixed period T is completed.

In the first embodiment shown in FIG. 2, the fixed delay circuit 5 is provided between the variable pulse width pulse generating circuit 4 and the power amplifier circuit 6 so as to provide a fixed delay. 5 is removed and the fixed delay circuit 5 is provided between the reception antenna 12 and the RF amplification circuit 13 or between the RF amplification circuit 13 and the multiplication circuit 14 to fix the reception signal 12A or the reception signal 13A. Even when the delay signal is configured to be delayed, the time relationship between the correlated signal, that is, the reception signal 13A and the correlation signal 15A given to the multiplication circuit 14 is as follows:
This is the same as the case of the first embodiment in FIG. 2, and a detection signal on which similar correlation detection processing has been performed is obtained.

In the first embodiment shown in FIG. 2, the fixed delay circuit 5 is inserted into the transmission / reception system from the variable pulse width pulse generation circuit 4 to the RF amplifier circuit 13 through the transmission antenna 7 to achieve the object. However, even if the fixed delay circuit 5 is inserted between the pulse width variable pulse generation circuit 4 and the correlation signal circuit 15 as in the third embodiment of FIG. By generating a pulse signal of a variable period that is sequentially shortened by a small amount of time Δt within a period, in contrast to the case of the first embodiment of FIG. 2 every period from the period T, the first embodiment of FIG. A detection signal that has undergone exactly the same correlation detection processing as in the example is obtained.

In the second embodiment of FIG. 1, the fixed delay circuit 5 is divided into two, one is a fixed delay circuit 5X between the power amplifier circuit 6 and the transmitting antenna 7, and the other is a receiving antenna 12
The fixed delay circuit 5Y is inserted between the RF amplifier circuit 13 and the fixed delay circuit 5Y.

This not only exhibits exactly the same effect as the fixed delay circuit 5 inserted in the transmission / reception system as in the first embodiment shown in FIG. 2, but also provides the necessary power amplification circuit 6 and transmission antenna 7 and This is practical because the length of the cable between the receiving antenna 12 and the RF amplifier circuit 13 can also be used as a delay circuit.

In the fourth embodiment shown in FIG. 8, a fixed delay is performed by a trigger signal. Instead of the fixed delay circuit 5 in the first embodiment shown in FIG. 2, a variable period trigger generation circuit 2 and a pulse width variable pulse are used. Trigger fixed delay circuit 1 between generation circuit 4
9 to obtain the fixed delay signal 5A of FIG.

The fifth embodiment shown in FIG. 9 is similar to the fourth embodiment shown in FIG. 8 except that the fixed delay is performed by a trigger signal. However, the variable period trigger generation circuit 2 and the pulse width variable correlation signal generation circuit are used. A trigger fixed delay circuit 19 is provided between the control circuit 20 and the control circuit 20.

In the case of the fourth embodiment shown in FIG. 8 and the fifth embodiment shown in FIG. 9, a pulse width variable correlation generating circuit 20 and pulse width control signal generating circuits 3X and 3Y are newly required.
The trigger fixed delay circuit 19 has a feature that it can be easily constituted by a digital circuit or the like, for example, like a monostable circuit.

The above description has been made using the monocycle signal shown in FIG. 4A, but the unipolar signal shown in FIG.
Even when the chirp signal of FIG. 2 and the coded signal of (d) are used, the width of the cycle Ta shown in FIG. Similar results are obtained.

In the case of a detection device for performing an underground exploration using a transmitted wave as shown in FIG. 6, the trigger cycle control signal circuit 1 provided in either the transmission side circuit unit 50 or the control / display circuit unit 70 And the pulse width variable pulse generation circuit 4, the correlation signal circuit 15, and the fixed delay circuit 5 to obtain the correlation signal 15A and the fixed delay signal 5A. The multiplication signal 14A is obtained by the multiplication circuit 14 provided to obtain the detection signal 17A subjected to the correlation detection processing, or in the same configuration, the fixed delay circuit 5 is connected to the reception antenna 12 and the reception side. It is moved between the RF amplifier circuit 13 of the circuit section 60 or between the RF amplifier circuit 13 and the multiplication circuit 14 provided in the reception circuit section 60 or the control / display circuit section 70. By configuring is not able to obtain a detection signal subjected to similar correlation detection processing.

[0037]

According to the present invention, a promised waveform whose pulse width is increased by a small amount at each time of a cycle is used as a transmission signal and a correlation signal, and a reception signal is multiplied by the correlation signal as a correlated signal. Based on the signal obtained
Since the target correlation detection signal is obtained by performing the correlation detection processing, a correlation detection signal with a high distance resolution can be obtained due to a narrow pulse width especially at a short distance.

At a long distance, a transmission signal having a wide pulse width is used, so that a highly sensitive correlation detection signal can be obtained.

[Brief description of the drawings]

FIG. 1 shows a block diagram of a first embodiment of the present invention.

FIG. 2 shows a block diagram of a second embodiment of the present invention.

FIG. 3 shows an operation waveform diagram of a main part of the first embodiment of the present invention.

FIG. 4 shows a signal waveform diagram of a main part of the prior art.

FIG. 5 shows an operation explanation and a conceptual explanation diagram of a main part of the present invention.

FIG. 6 shows a block diagram of the prior art.

FIG. 7 shows a block diagram of a third embodiment of the present invention.

FIG. 8 shows a block diagram of a fourth embodiment of the present invention.

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

[Explanation of symbols]

 1 Trigger cycle control signal 2 Variable cycle trigger generation circuit 2A Variable cycle trigger signal 3, 3X, 3Y Pulse width control signal generation circuit 3A Promising waveform signal 4 Pulse width variable pulse generation circuit 5, 5X, 5Y Fixed delay circuit 5A Fixed delay signal 6 Power amplifying circuit 7 Transmitting antenna 8 Transmitting electromagnetic wave 9A, 9B Underground object 10 Ground surface 11 Underground 12 Receiving antenna 12A Received signal 13 RF amplifier 13A Received signal 14 Multiplication circuit 14A Multiplication signal 15 Correlation signal circuit 15A Correlation signal 16 Integrator 16A Integral signal 17 Sample holding circuit 17A Detect signal 18 Display 19 Trigger fixed delay circuit 20 Pulse width variable signal generator 50 Transmitter circuit 60 Receiver circuit 70 Control / display circuit 100 Underground radar

Claims (2)

[Claims] 1. A transmission signal having a promised waveform that repeats at a required period is transmitted, a reception signal obtained by a reflected wave or a transmitted wave of the transmission signal is set as a correlated signal, and the promised waveform is converted at each time of the period. A correlation-type signal detection device that obtains a required detection signal in correlation with the correlation signal having
A promised waveform signal means for obtaining a signal of the promised waveform as a variable period (hereinafter, referred to as a promised waveform signal) as a variable period in which the period is sequentially extended or shortened, and a pulse width of the promised waveform signal for each time of the period From a narrow pulse width to a wide pulse width sequentially to obtain a promised waveform signal of continuously variable pulse width, and a promised waveform signal via a delay path or a delay circuit having a predetermined fixed delay amount. Delayed, transmission signal means for obtaining the transmission signal based on the promised waveform signal, or correlation signal means for obtaining the correlation signal, and correlation signal means for obtaining the correlation signal based on the promised waveform signal, or Transmission signal means for obtaining the transmission signal, multiply the amplitude of the correlated signal and the amplitude of the correlation signal, based on the signal of the multiplied amplitude value,
A pulse width continuously variable correlation type signal detection device, comprising: multiplication means for obtaining the detection signal. 2. The transmission signal unit according to claim 1, further comprising a pulse width continuously variable transmission unit that changes only the pulse width of the transmission signal of the promised waveform signal from a narrow pulse width to a wide pulse width at each time of the period. Pulse width continuously variable correlation type signal detector.