JPH0340875B2 - - Google Patents

Description

[Detailed Description of the Invention] [Technical Field of the Invention] This invention relates to a correlation process that detects a signal having a spectrum equivalent to a reference power spectrum from an input signal by calculating a correlation coefficient of power spectra. Regarding equipment.

[Technical background of the invention and its problems]

FIG. 1 shows a conventional correlation processing device. Input signal i is analog/digital (A/
D) is supplied to the conversion circuit 11, and this conversion circuit 11
At the sampling pulse signal s of a predetermined period, the signal is converted into a digital time series signal. This sample data is supplied to the first storage circuit 12 and stored therein. The number of samples stored is 2N. The sample data read out from the storage circuit 12 is sequentially supplied to the power spectrum calculation circuit 13, and is processed using, for example, FFT (Fast Fourier Transform).
Depending on the method, N pieces of power spectrum data xi(i
=0, 1,...,N-1) are obtained. This power spectrum data xi is supplied to the second storage circuit 14 and stored therein.

On the other hand, the third storage circuit 15 stores reference power spectrum data yi corresponding to the signal to be detected in advance.
(i=0, 1, . . . , M-1; M<N) are stored. The data stored in storage circuits 15 and 14 are read out in sequence and supplied to cross-correlation calculation circuit 16. This calculation circuit 16 performs the following calculation.

However, k=0, 1,..., N-1 = 1/M _k+M-1 〓 ^i=k xi = 1/M _M=1 〓 ⁱ⁼⁰ yi Correlation coefficient obtained by this calculation γ(k) is supplied to a determination circuit 17, which determines the maximum value γ(k)max of the correlation coefficient γ(k).
Then, from this value of k, the center frequency of the signal whose power spectrum pattern matches the reference spectrum pattern is determined. Figure 2 a, b, c
are examples of xi, yi, and γ(k), respectively.

By the way, since the power spectrum xi of the input signal is discrete data for each frequency resolution Δ (where Δ=s/2N), it is determined by the value of the center frequency ₀ of the signal as shown in Figure 3 a and b. What should originally be the same spectrum has the possibility of becoming quite different spectrum data. The dotted line _between a and b in Figure 3 shows the _continuous spectral envelope. (a positive integer), and a value of ₀ makes these two extremes and a spectral pattern in between.

This means that if the reference spectral pattern is stored, for example, in the form shown in Figure 3a,
In the case of a pattern between a and b shown in FIG. 3, the maximum value r(k)max of the correlation coefficient varies accordingly. As described above, the conventional apparatus has the drawback that the correlation coefficient varies greatly depending on the relative relationship between the center frequency of the signal and the frequency resolution.

[Object of the Invention] This invention was made based on the above circumstances, and its object is to provide a correlation processing device that can obtain a predetermined correlation coefficient no matter what the center frequency of the input signal. This is what we are trying to provide.

[Summary of the invention]

This invention obtains the power spectrum of an input signal, finds the maximum correlation coefficient between this spectrum and a reference spectrum, and changes the input signal in n steps within a frequency resolution Δ determined by a power spectrum calculation circuit. By determining the largest value from a group of n maximum values of the correlation coefficients determined for each of the changed signals, a correlation coefficient with little variation is always obtained.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to the drawings. Note that the same parts in FIG. 4 as in FIG. 1 are given the same reference numerals.

In FIG. 4, input signal i is supplied to frequency conversion circuit 41. In FIG. An output signal from a local oscillation circuit 42 is supplied to this conversion circuit 41, and the frequency of the input signal i is changed by this signal. That is,
The local oscillation circuit 42 is capable of changing its output frequency within a predetermined range, and this signal causes the frequency of the input signal i to be shifted within the range of the frequency resolution Δ. The frequency-converted signals are sequentially supplied to the A/D conversion circuit 11 to the cross-correlation calculation circuit 16 and the first determination circuit 17,
The maximum value group {γn(k( _o )}) of the correlation coefficients is obtained from the first determination circuit 17 by the same operation as in FIG.

Now, in this device, first, the frequency of the local oscillation circuit 42 is selected so that the output frequency of the frequency conversion circuit 41 is equal to the frequency of the input signal i,
The maximum value γ ₁ (k ₁ ) of the correlation coefficient at this time is calculated. Next, the frequency of the local oscillation circuit 42 is Δ/n
The maximum value γ ₂ (k ₂ ) in this case is determined by a similar calculation. Below, local oscillation circuit 4
The maximum value of the correlation coefficient is calculated sequentially by changing the frequency of 2 by Δ/n, and γ ₁ (k ₁ ), γ ₂ (k ₂ ), ..., γ
_o
A group of n maximum values of (kn) is determined. As a result, the frequency of the input signal i is changed by the width Δ by Δ/n, so from Figure 3a to Figure 3b
There are n different spectral patterns up to. Therefore, if we select the largest maximum value γ(k)max from a group of n maximum values, we get
The correlation coefficient closest to the reference frequency pattern can be obtained. The second determination circuit 43 performs this, and determines the maximum value γ(k) that is the largest among the n maximum value groups obtained by the first determination circuit 17.
max is determined.

With this configuration, no matter where the center frequency ₀ of input signal i is within the frequency resolution Δ, the correlation coefficient γ(k)max always has little variation.
It becomes possible to obtain.

〔Effect of the invention〕

As described in detail above, according to the present invention, it is possible to provide a correlation processing device that can obtain a predetermined correlation coefficient regardless of the center frequency of the input signal.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an example of a conventional correlation processing device, FIG. FIG. 1 is a configuration diagram showing an embodiment of a correlation processing device according to the present invention. 11...A/D conversion circuit, 13...Power spectrum calculation circuit, 16...Cross correlation calculation circuit, 17
...first determination circuit, 41...frequency conversion circuit,
42... Local oscillation circuit, 43... Second determination circuit.

Claims (1)

[Claims] 1. An oscillation circuit that can change the oscillation frequency, a frequency conversion circuit that changes the frequency of an input signal using this oscillation signal, a circuit that A/D converts this conversion output signal with a predetermined sampling pulse signal, and A circuit that obtains a power spectrum from a sampled signal, a circuit that is supplied with the obtained power spectrum and a reference power spectrum and obtains a cross-correlation coefficient, and a first judgment that obtains a maximum value from the obtained correlation coefficient. the maximum value from among the group of n maximum values obtained by the first judgment circuit when the oscillation frequency of the oscillation circuit is changed by n steps within the frequency resolution range of the circuit and the circuit for calculating the power spectrum. A correlation processing device characterized by comprising: a second determination circuit for determining .