JP2642771B2 - Passive sonar broadband signal reception method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial application field) The present invention relates to a passive sonar that searches for a target, measures a position of the target, and categorizes the target using a sound wave radiated by a target moving in a three-dimensional space (underwater). Alternatively, the present invention relates to a method for receiving a wideband signal of a passive sonar among active sonars which irradiate a sound wave toward a target and search for the target using a reflected wave (echo). More specifically,
According to the present invention, a continuous wideband signal having a high degree of stationery, such as a running sound of a ship or the like, is received by a sensor, and detection of the wideband signal is performed using intensity information (hereinafter, referred to as “power”) of the sensor output. The present invention relates to a passive sonar broadband signal receiving method.

(Prior Art) Conventionally, techniques in such a field include: PROCEEDINGS OF T
HE IEEE), 69 [11] (1981-11) (USA) WCKNIGHT et
al "Digital Signal Processing for
Sonar (Digital Signal Processing for Sonar) "P.1
There were those described in 451-1506. Hereinafter, the configuration will be described with reference to the drawings.

FIG. 2 is a functional block diagram showing an example of a configuration of a conventional passive sonar broadband signal receiving method described in the above document.

This broadband signal receiving method is a square-law detection receiving method, for example, a sensor 1, an amplifier 2, a band limiting filter 3,
Sampler 4, square calculator 5, integrator 6, and output terminal 7
Is processed as follows.

The wideband signal Sin from the target is received by the sensor 1,
The sensor output is amplified by the amplifier 2 to an appropriate level. After unnecessary frequency components of the amplified received signal are removed by the band control filter 3, the signal is converted into a digital signal by the sampler 4 and sent to the square calculator 5.

The square calculator 5 calculates a square value of the digital reception signal output from the sampler 4 to obtain a wideband signal.
Strength at time t _k of Sin (hereinafter referred to as "instantaneous power") sent to the integrator 6 in search of P (k). The integrator 6 integrates the instantaneous power P (t) to form a broadband signal Si.
n long-term integrated power (hereinafter referred to as "power")
(K) is obtained and output from the output terminal 7 as power information. Then, using the power time-series information output from the output terminal 7, detection of the wideband signal Sin and the like are performed.

Here, the integrator 6 can be constituted by, for example, a finite impulse response filter (hereinafter, referred to as “FIR filter”) or an infinite impulse response filter (hereinafter, referred to as “IIR filter”). In the case of receiving Sin, if an FIR filter is used, the signal processing becomes complicated and the processing time becomes longer, so that the integrator 6 is usually configured using an IIR filter to simplify the signal processing and increase the processing speed. Speedup.

(Problems to be solved by the invention) However, the conventional receiving method has the following problems.

In the conventional receiving method, a high-level pulse signal Ps also called a search sound transmitted from an active sonar,
When an IIR filter is used for the integrator 6 when the signal is in the symmetric frequency band of the wideband signal Sin, there is a problem that the power of the wideband signal Sin is masked for a long time by the power of the pulse signal Ps.

FIG. 3 is a more detailed illustration of such a problem. In the figure, P ₁ (t) indicates the instantaneous power of only the wideband signal Sin at time t, P ₂ (t) indicates the instantaneous power of only the pulse signal ps at time t, and (t) indicates the wideband Si.
This shows the power of the addition signal of n and the pulse signal Ps. In addition,
All are shown in a continuous system for simplicity.

As shown in FIG. 3, the pulse signal ps pulse duration T _p which continues from time t1 to t2 is when present in the symmetric frequency band of the wideband signal Sin, (t) is the integrator 6 using an IIR filter Affected, after time t2, approximately at time t3
During the time T _i leading to.

The time Ti affected by the power of the pulse signal ps is P
_It is determined by the relative level of ₁ (t) and P ₂ (t), the pulse width T _p , and the equivalent integration time τ of the integrator 6. For example, when an exponential function is selected as a response function of the IIR filter forming the integrator 6, when 10 log ｛P ₂ (t) / P ₁ (t)｝ 40 dB, T _p = 1 second, and τ = 60 seconds, time T _i is on the order of about 60 to 80 seconds. When the power of the wideband signal Sin is masked for a long time as described above, the power of the wideband signal Sin cannot be continuously detected, the receiving accuracy is reduced, and it is difficult to solve the problem. there were.

The present invention has a problem that the related art has a problem that when a relatively high-level pulse signal is included in a reception target band of a wideband signal, the pulse signal remains for a long time after the end of the duration of the pulse signal. An object of the present invention is to provide a passive sonar broadband signal receiving method that solves the problem that the power of the wideband signal is masked and the receiving accuracy is reduced.

For (SUMMARY for a) the invention is to solve the above problems, a wideband signal from a target is received by the sensor, the instantaneous power is the intensity at time t _k of the wideband signal based on the sensor output Calculate and integrate the instantaneous power in the time domain to obtain a long-term integrated power in a broadband signal receiving method of a passive sonar, wherein a frequency analysis process, an instantaneous power density calculation process, a pulse detection process, a pulse component removal parameter setting process, and The instantaneous power calculation processing determines the instantaneous power P (k) of the wideband signal Sin.

That is, in the frequency analysis processing, the wideband signal of the sensor output is divided into narrowband components, and the result of the division is given to the instantaneous power density calculation processing. In the instantaneous power density calculation process, the instantaneous power density, which is the short-time integrated power, is calculated for each frequency of the divided narrow band components, and the calculation result is sent to the instantaneous power calculation process and the pulse detection process.

In the pulse detection process, only the pulse-like signal component is detected for each of the divided frequencies using the time-series data of the instantaneous power density, and the detection result is provided to the pulse component removal parameter setting process. In the pulse component removal parameter setting process, the removal start time t _{s, m} and the removal release time tp _{, m} (where m = 1,..., M are the divided frequencies) for each frequency of the detected pulse-like signal component. ) And sends the set value to the instantaneous power calculation process.

Instantaneous power calculating process, based on the processing result of the pulse rejection parameter setting process, the time t _k at t _{s, m} t _k
The instantaneous power density of the m-th frequency that satisfies the condition of tp _{, m} is removed, and the instantaneous power density is added in the frequency domain. Calculate the equivalent instantaneous power.

The removal start time t _{s, m} and removal removal time t _{p, m at} the frequency at which no pulse is detected may be processed by setting t _{s, m} = t _{p, m} .

(Operation) According to the present invention, since the wideband signal receiving method is configured as described above, the received wideband signal is divided into narrowband components, and the instantaneous power density is calculated for each frequency. Further, the pulse signal is detected for each frequency, and the power component of the pulse signal included in the instantaneous power density is removed from the parameters of the detected pulse signal. Thereby, the influence of the pulse signal is removed and the power of the wideband signal is continuously obtained. Therefore, the above problem can be solved.

(Embodiment) FIG. 1 shows an embodiment of the present invention and is a functional block diagram of a receiving apparatus using a passive sonar broadband signal receiving method, in which elements common to the conventional elements in FIG. Are denoted by the same reference numerals.

This receiving apparatus differs from the conventional one in FIG. 2 in that an instantaneous power calculation processing unit 10 is used instead of the square calculator 5 in FIG.
That is,

The instantaneous power calculation processing unit 10 performs a fast Fourier transform (FF
A frequency analyzer 11 for dividing the output of the sampler 4 into narrow band components by digital Fourier transform such as T), an instantaneous power density calculator 12 for calculating an instantaneous power density from the output of the frequency analyzer, and an output of the instantaneous power density calculator An instantaneous power calculator 13 which calculates the instantaneous power Pa (k) from the above and supplies the calculated instantaneous power Pa (k) to the integrator 6. Further, the pulse detector 14 detects a pulse-like signal component from the output of the instantaneous power density calculator.
And a parameter for setting a parameter for removing a pulse-like signal component from the output of the pulse detector and providing the parameter to the instantaneous power calculator 13.
Are provided.

FIG. 4 is a functional block diagram showing one configuration example of the pulse detector 14 in FIG.

The pulse detector 14 has input terminals 31 _{1 to} 31 _M for inputting the output of the instantaneous power density calculator 12, and includes an integrator
32 _{1 to} 32 _M , threshold setting unit 33 _{1 to} 33 _M , comparator
34 _{1 to} 34 _M and output terminals 35 _{1 to} 35 _M to the pulse component removal parameter setting device 15 are connected.

Next, a method of receiving a wideband signal using the above-described receiving apparatus will be described.

In FIG. 1, a broadband signal Sin from a target is received by a sensor 1 and the sensor output is amplified by an amplifier 2 to an appropriate level. Unnecessary frequency components of the amplified received signal are removed by the band control filter 3, then converted into digital signals by the sampler 4,
Sent to

The frequency analyzer 11 divides the wideband signal output from the sampler 4 into M narrowband components. Frequency analyzer 11
Is generally a complex signal, and the M complex signals are squared in absolute value by the instantaneous power density calculator 12 and output as M instantaneous power densities. The instantaneous power density function of the m-th frequency f _m in the M time _{t k P (m, k)} ( where, m = 1, ..., M , k = 1, ...)
Expressed by Time t _k at M number of instantaneous power density P (m;
k) is input to the instantaneous power calculator 13 and the pulse detector 14.

In the pulse detector 14, time series data of instantaneous power density..., P (m; k-3), P (m; k-2), P (m; k-1), P (m , with k), detects only pulse component included in the frequency f _m.

That is, in the pulse detector 14 of FIG. 4, the integrators 32 ₁ ,
32 ₂ ,..., 32 _M are integrators having an equivalent integration time that is sufficiently longer than the maximum time width of the pulse signal to be detected, and are output to the instantaneous power density calculator output from the input terminals 31 _{1 to} 31 _M. based pulses to estimate the level of the signal components other than the pulse for determining-threshold for detecting and sends the estimation result-threshold setter 33 _to 333 to the _M.

-Threshold setter 33 ₁ ~ 33 _M are integrators 32 ₁ to 32 _M
Level output from, by adding a predetermined constant value,-threshold value at time t _k TH (1;
k), TH (2; outputs k) to the comparator 34 ₁ to 34C _M a; k), ..., TH ( M. Here, the value to be added is set according to the minimum level to be subjected to pulse component removal determined by the false alarm probability or the like.

Comparators 34 _{1 to} 34 _M are threshold setting units 33 _{1 to} 33 _M
And the input terminals 31 _{1 to} 31 _M
Instantaneous power at time t _k which is input from the density P (1:
, P (2; k),..., P (M; k) are compared for each frequency f _m , and the instantaneous power density P (m; k) is set to a threshold value TH _m
When exceeded, it gives the first view of the pulse component removal parameter setting unit 15 outputs a pulse detection signal to the output terminal 35 ₁ to 35 _M.

The pulse component removal parameter setting device 15 is a pulse detector
Using the pulse detection signal output from 14, each frequency f _m
A removal start time t _{s, m} and a removal release time t _{p, m} are generated for each
Output to the instantaneous power calculator 13. Instantaneous power calculator 13
The instantaneous power instantaneous power output from the density calculator 12 Density P; Of _{(m k), t s,} m t k t p, the instantaneous power density P excluding the instantaneous power density of the frequency f _m that satisfies _m (M;
By calculating the sum of k), the instantaneous power P _a (k) of the wideband signal Sin is calculated by the following equation and output to the integrator 6.

: In t _s, the integrator 6 except m satisfying _m t _k t _{p, m,} and calculates a power (k) by integrating the instantaneous power P _a (k) by the time domain, and outputs to the output terminal 7.
Therefore, the wideband signal Sin can be detected using the time-series information of the power (k) output from the output terminal 7.

 FIG. 5 is an operation waveform diagram of FIG.

P ₁ (f; k) is the instantaneous power density function of only the broadband signal component at time _{t k, P 2 (f;} k) denotes the instantaneous power density function of only the pulse signal component at time t _k. P _a (f; k)
Indicates an instantaneous power density function obtained by removing components exceeding a threshold from the instantaneous power density function of the addition signal of the wideband signal Sin and the pulse signal. In FIG. 5, the instantaneous power density function is shown as a continuous function in the frequency domain to simplify the description.

If the range of the frequency f _m beyond the-threshold is F _{1 fm} F ₂ at time t _k, the instantaneous power density components belonging to F _{1 fm} F ₂ is removed from the adding operation of the instantaneous power calculator 13, the P _{From a} (f; k), the instantaneous power P of the wideband signal Sin
_a (k) will be calculated.

Therefore, even when the integrator 6 having a long-time integration function constituted by an IIR filter is used, interference of the pulse signal is reduced for a long time. further,
Outside the frequency band in which the strong instantaneous power of the pulsed signal exists, the signal is continuously received without being affected by the pulsed signal. Therefore, loss of power information of the wideband signal Sin can be reduced. The receiving method of this embodiment is more effective when the bandwidth of the pulse signal is relatively narrow as compared with the receiving bandwidth of the wideband signal Sin.

Note that the present invention is not limited to the illustrated embodiment.
Various modifications are possible, such as receiving a wideband signal by processing each block in FIG. 1 with a digital signal processor (DSP) or a microprocessor.

(Effects of the Invention) As described in detail above, according to the present invention, the conventional square calculation processing is replaced with a frequency analysis processing, an instantaneous power density calculation processing, and an instantaneous power calculation processing.
Using the time series data of the instantaneous power density calculation processing output, to detect a pulse signal, based on the pulse detection information,
A strong power component generated by the pulse signal is removed from the adding operation of the instantaneous power calculation processing. Therefore, even when a long-time integration process using an IIR filter is performed, the interference of the pulse over a long period of time is reduced, and outside the frequency band where the strong instantaneous power of the pulse is present, the pulse is excluded. Since the signals are continuously received without being affected, loss of power information of the wideband signal can be reduced. The present invention is more effective when the bandwidth of the pulse signal is relatively narrow as compared with the reception bandwidth of the wideband signal.

[Brief description of the drawings]

FIG. 1 is a functional block diagram of a receiving apparatus using a passive sonar broadband signal receiving method according to an embodiment of the present invention.
FIG. 1 is a functional block diagram of a receiving apparatus using a conventional passive sonar broadband signal receiving method. FIG. 3 is an explanatory view of a problem of the conventional receiving method. FIG. 4 is a function of a pulse detector in FIG. FIG. 5 is a block diagram, and FIG. 5 is an operation waveform diagram of FIG. 1 ... sensor 4 ... sampler 6 ... integrator 10 ...
Instantaneous power calculation processing unit, 11: Frequency analyzer, 12: Instantaneous power density calculator, 13: Instantaneous power calculator, 14 ...
Pulse detector, 15 ... Pulse component removal parameter setting device.

Claims (1)

(57) [Claims] 1. A wideband signal from a target is received by a sensor.
Calculating the instantaneous power is the intensity at time t _k of the wideband signal based on the sensor output, in a broadband signal receiving method Passhibusona seeking long integrated power by integrating the instantaneous power in the time domain, the sensor output A frequency analysis process of dividing the wideband signal into narrowband components, an instantaneous power density calculation process of calculating an instantaneous power density that is a short-time integrated power for each frequency of the divided narrowband components, A pulse detection process for detecting only a pulse-like signal component for each of the divided frequencies using the time-series data of the above, a removal start time t _{s, m} and a removal release time for each frequency of the detected pulse-like signal component t _{p, m} (where, m = 1, ..., M is the divided number of frequency) and a pulse component removal parameter setting processing for setting, the pulse rejection parameter Based on the processing result of the data setting _{processing, t s, m t k t} p, removing the instantaneous power density of satisfying the m-th frequency _m the instantaneous power density by adding in the frequency domain at the time t _k And performing an instantaneous power calculation process for calculating an instantaneous power of the wideband signal.