JPH08213931A - Signal processor - Google Patents

Abstract

PURPOSE: To obtain the signal processor which is immune to surrounding noise and effect of input level fluctuation attended thereto. CONSTITUTION: A signal received by an antenna 1 is given to a multiplexer 3 via an RF amplifier 2, frequency-converted and the result is given to an LPF 6, where the side band is eliminated from the signal. An output of the LPF 6 is converted into a digital signal by an A/D converter 6 and the signal is given to a 1st comparator 8, a delay device 10, a subtractor 11 and a demodulator 14 via a DMF 7 and the result is outputted as information data. An output as the information data is normally demodulated by ANDing an output of a 1st comparator 8, an output of a 2nd comparator 12 receiving an output of a differentiation circuit comprising a delay device 10 and a subtractor 11 at an AND circuit 16 by controlling a timing generator 15.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a signal processing device for performing spread spectrum demodulation in a device for performing communication using spread spectrum technology.

[0002]

2. Description of the Related Art In recent years, as various devices have been digitized, unnecessary radiation due to their operation has become a problem. For example, the reason why a portable compact disc player cannot be used in a passenger plane is that there is a case in which the operation system of the passenger plane is confused due to unnecessary radiation due to its operation, and it is about to crash. As is clear from this example, the unwanted radiation that enters the signal transmission path is a serious problem.

A "spread spectrum communication system" is currently in the limelight as a communication system which is less susceptible to such unwanted radiation. As its name implies, this method is a communication method in which a spectrum limited to a certain band is spread and used in a wide band. Even if this is affected by noise, not all spectra are destroyed, so
It is possible to prevent errors during reception.

First, an outline of the operation of transmission / reception for performing spread spectrum will be described. FIG. 6A is a diagram showing the modulation principle of the spread spectrum system on the transmission side. In the figure, 51 is a means for generating information data to be transmitted, and this output is once a narrow band baseband modulator 52.
Frequency modulated by. This modulation method is QP
SK (Quadrature Phase Shift Keying) and BPSK (Bina
ry Phase Shift Keying) is common.

The output of the baseband modulator 52 is multiplied by a PN code or the like in the spread spectrum modulator 53. The clock frequency of this PN code determines the frequency bandwidth after spreading. For example, to spread the bandwidth to 26 MHz, multiply by a PN code with a clock frequency of 13 MHz. The spread signal is frequency-converted into an RF band by an RF modulator, amplified by an amplifier, and output.

When receiving, the original information is restored through the reverse process as shown in FIG. 6 (b). Here, I have described the advantages of interference waves, but in addition to this, because the peak power is kept low to spread the power, and the receiving side cannot demodulate unless the same "key" (code) as the transmitting side is used, There is a feature that confidentiality can be obtained without performing any processing. The above method is called a direct diffusion method.

Although the spread spectrum method has many advantages as described above, the proposal itself was made in the 1940's, but the application has only just begun in recent years, and it has not been sufficiently developed. . FIG.
It is a block schematic diagram of a signal processing device in the prior art example of the present invention showing one of such few application examples.

In the figure, the radio wave received by the antenna 1 is amplified by the RF amplifier 2 and sent to the multiplier 3. Frequency conversion is performed by the sine wave signal from the sine wave oscillator 4, a side band band is removed by a low pass filter (hereinafter abbreviated as "LPF"), and an analog / digital converter (hereinafter abbreviated as "A / D"). Quantify at.

The digitized received signal is used by the correlator 31.
In, for example, autocorrelation or the like can be obtained. The output of the correlator 31 is sent to the comparator 32 and the demodulator 14.
The comparator 32 compares with a threshold value 33 stored in a ROM (Read Only Memory) or the like, and if it exceeds a predetermined threshold value, regards it as information and outputs an information detection signal Sn.

Regarding the generation of this information detection signal, some explanation will be added with reference to the signal waveform diagram of FIG. In the figure, D1 is a threshold value, and when a correlator is used for spread spectrum reception, when the received signal is correlated, the output level of the correlator shows a peak, otherwise the output of the correlator is low. It can be suppressed. Since the spread demodulation is performed at this peak and the information is reproduced, the peak exceeding the high threshold value D1 is set as this peak, and the peak is reliably captured by synchronizing with the input to the demodulator 14 in the timing generator 15. is there.

[0011]

However, in such a system, in the case where the output of the correlator 31 is as shown in FIG. 5, when the threshold 33 is D1, the input level fluctuates, and the point A in FIG. If the threshold value 33 is lowered to D2 in order to detect this peak in the case where the signal drops from the point A to the point B, the signal at the point C can be detected. There is a problem that it will be erroneously detected. There is a problem that an ideal automatic gain control circuit is required before the A / D 6 to control the setting of the threshold value 33.

The present invention has been made in view of the above problems, and it is an object of the present invention to provide a signal processing device which is not easily affected by ambient noise and input level fluctuations accompanying it.

[0013]

In order to achieve the above object, the signal processing apparatus of the present invention is, in claim 1, a correlating means for obtaining a correlation of a received modulated signal, and an output of this correlating means and a predetermined value. Of the output of the correlation means, a first comparison means for comparing the output of the correlation means with the first threshold value of And a synthesizing means for logically synthesizing the output of the second comparing means and the output of the first comparing means.

In the second aspect, the change amount detecting means delays the output of the correlating means by a predetermined time, and the output of the delaying means and the output of the correlating means at a predetermined ratio. And subtraction means for subtracting.

Further, in claim 3, the correlation means is a digital matched filter.

Further, according to a fourth aspect of the present invention, a timing generating means for generating a signal that changes for a predetermined time according to the output of the synthesizing means, and a state for demodulating the output of the correlating means according to the output of the timing generating means And demodulation means for changing

[0017]

According to the above structure, in the first aspect, the correlation of the modulated signal received by the correlating means is obtained, and the output of the correlating means is compared with the predetermined first threshold value by the first comparing means. The change amount detecting means detects a time change amount of the output of the correlating means, compares the output of the change amount detecting means with a predetermined second threshold value by the second comparing means, and the combining means outputs the second value. Since the output of the comparison means and the output of the first comparison means are logically combined, it is less likely to be affected by ambient noise and the accompanying level fluctuation of the input.

In the second to fourth aspects, the change amount detecting means delays the output of the correlating means by a predetermined time, and the output of the delaying means and the output of the correlating means are predetermined. Since the anomaly can be easily detected because the subtraction means for subtracting by the ratio is used, the correlating means is a digital matched filter, and the present apparatus generates a signal that changes for a predetermined time according to the output of the synthesizing means. Since it further comprises timing generation means and demodulation means for changing the state of demodulating the output of the correlation means in accordance with the output of the timing generation means, it is less susceptible to ambient noise and the accompanying level fluctuation of the input. Become.

[0019]

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows a schematic block diagram of a signal processing apparatus according to an embodiment of the present invention. In FIG. 1, the antenna 1, the RF amplifier 2, the multiplier 3, the sine wave oscillator 4, the LPF 5, the A / D 6, the demodulator 14 and the timing generator 15 are the same as those in the conventional example, and detailed description thereof will be omitted. . Reference numeral 8 is a first comparator, 9 is a first threshold, which is the same as the comparator 32 and the threshold 33 in the conventional example. Reference numeral 7 is a digital matched filter (hereinafter abbreviated as "DMF"), 10 is a delay device, 11 is a subtractor, 12 is a second comparator, and 13 is a second threshold value.
Regarding the signal processing device of the present invention configured as described above,
The operation will be described below with reference to the waveform chart of FIG.

First, the DMF that receives the output of the A / D 6
7 will be described. DMF is a circuit for demodulating a spectrum-spread signal into original data, and outputs the largest amplitude when the PN code performed at the time of transmission and the PN code on the receiving side are the same and synchronized. It is a thing. In case of digital circuit, FIR (Finit
e Impulse Response) It has a similar structure to the filter. FIG. 3 shows an example of the structure.

A delay device having a delay time D equal to one cycle of the clock frequency of the PN code, and a coefficient having a coefficient of 1 when the PN code is "1" and a coefficient of -1 when the PN code is "0". It consists of a multiplier, a multiplier, and an adder. If the input PN code sequence and the received PN code are the same and their cycles match,
The multiplier operates only 1 × 1 or −1 × −1. Therefore, the output results are all 1. The output result of adding these is the maximum. If not synchronized or the PN codes do not match, the multiplier also operates 1 × -1 in addition to 1 × 1 and −1 × -1. Therefore, the result of adding these is smaller than the output result when the PN codes are the same and synchronized. See Table 1 below.

[0022]

[Table 1]

In this way, the DMF 7 is delayed by the delay device 10 having the delay amount D, and the subtracter 11 subtracts the output of the DMF before and after the delay. This operation corresponds to a kind of differential operation and is equivalent to simple feature extraction. Thereby, the waveform as shown in FIG. 2C can be obtained. A value of Dh2 is stored in the second threshold value 13, and if the waveform is shaped by the second comparator 12, a waveform as shown in FIG. 4D can be obtained.

As a result, a logical product with the output of the first comparator 8 is obtained in the logic synthesizing circuit 16 (here, the AND circuit), and both are synthesized to produce a noise signal as shown in FIG. Sn ′ is synthesized. The noise signal controls the demodulator 16 via the timing generator 15 as in the conventional example. This enables demodulation in a spread spectrum communication system that is less susceptible to noise.

As described above, according to this embodiment, the delay device 1
The output of the DMF 7 that has passed through the differentiation circuit (feature extraction circuit) by 0 and the subtractor 11 is waveform-shaped by the second comparator 12,
The output of the first comparator, which is the same as the conventional one, and the AND circuit 1
Since they are combined in 6 and supplied to the timing generator 15, there is an effect that it is possible to provide a signal processing device that is not easily affected by ambient noise and input level fluctuations associated therewith. Therefore, even if the input signal fluctuates, only the peak can be reliably captured.

In the above explanation, the output of the DMF 7 is judged to be hard, but it may be judged to be soft. Further, the differential operation is configured by only one delay device 10 and one subtractor 11, but it may be stacked in multiple stages or IIR (Infinite Impu
Lse Response) type or a differential filter by bilinear transformation may be used. Besides, the present invention is not limited to the above-mentioned embodiment, and various modifications can be made.

[0027]

As described above, the signal processing device of the present invention is
According to claim 1, the correlation of the modulated signal received by the correlating means is obtained, and the output of the correlating means and the predetermined first threshold value are set to the first value.
Of the correlation means, and the change amount detecting means detects the time change amount of the output of the correlating means, and compares the output of the change amount detecting means with a predetermined second threshold value by the second comparing means. Then, in the synthesizing means, the output of the second comparing means and the first
Since it is logically synthesized with the output of the comparing means, there is an effect that it is hardly affected by ambient noise and the accompanying input level fluctuation. Therefore, even if the input signal fluctuates, only the peak can be reliably captured.

In the second to fourth aspects, the change amount detecting means delays the output of the correlating means by a predetermined time, and the output of the delaying means and the output of the correlating means are predetermined. Since the anomaly can be easily detected because the subtraction means for subtracting by the ratio is used, the correlating means is a digital matched filter, and the present apparatus generates a signal that changes for a predetermined time according to the output of the synthesizing means. Since it further includes timing generation means and demodulation means for changing the state of demodulating the output of the correlation means according to the output of the timing generation means, it is less susceptible to ambient noise and the accompanying level fluctuation of the input. There is an effect. Therefore, even if the input signal fluctuates, only the peak can be reliably captured.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a signal processing device according to an embodiment of the present invention.

FIG. 2 is a signal waveform diagram in a main part of the signal processing device in the example.

FIG. 3 is a block diagram showing a configuration of a DMF in the signal processing device in the embodiment.

FIG. 4 is a block diagram showing a configuration of a signal processing device in a conventional example of the present invention.

FIG. 5 is a signal waveform diagram in a main part of the signal processing device in the conventional example.

FIG. 6 is a schematic block diagram illustrating a general configuration of a spread spectrum communication system.

[Explanation of symbols]

 1 Antenna 2 RF Amplifier 3 Multiplier 4 Sine Wave Oscillator 5 LPF 6 A / D 7 DMF 8 First Comparator 9 First Threshold 10 Delayer 11 Subtractor 12 Second Comparator 13 Second Threshold 14 Demodulation 15 Timing generator 16 AND circuit

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[Procedure amendment]

[Submission date] January 10, 1996

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0008

[Correction method] Change

[Correction content]

In the figure, the radio wave received by the antenna 1 is amplified by the RF amplifier 2 and sent to the multiplier 3. The frequency is converted by the sine wave signal from the sine wave oscillator 4, and a low pass filter (hereinafter abbreviated as "LPF") 5
The band of the side band is removed at and the digitization is made at the analog-to-digital converter (hereinafter abbreviated as “A / D”) 6 .

[Procedure Amendment 2]

[Document name to be amended] Statement

[Name of item to be corrected] 0023

[Correction method] Change

[Correction content]

In FIG . 2, (a) and (b) are respectively
The outputs of the DMF 7 and the first comparator 8 are shown. DMF
The output of 7 is given to the delay device 10 and the subtractor 11,
10 delays by a delay amount D corresponding to one clock cycle.
Cast is to, DMF after the delay and the delay before the subtractor 11
The output of is subtracted. This operation corresponds to a kind of differential operation and is equivalent to simple feature extraction. Thereby, the waveform as shown in FIG. 2C can be obtained.
The second threshold value 13 is stored a value comprised Dh2, reduced
If the waveform of the output of the calculator 11 is shaped by the second comparator 12,
A waveform as shown in FIG. 2D can be obtained.

[Procedure 3]

[Document name to be amended] Statement

[Name of item to be corrected] 0024

[Correction method] Change

[Correction content]

As a result, in the logic synthesis circuit 16 (here, the AND circuit), the logical product with the output of the first comparator 8 is obtained, and both are synthesized to obtain information as shown in (e) of FIG.
The detection signal Sn 'is synthesized. With this information detection signal , the demodulator 1 is passed through the timing generator 15 as in the conventional example.
Control 6 This enables demodulation in a spread spectrum communication system that is less susceptible to noise.

Claims (4)

[Claims] 1. Correlating means for obtaining a correlation of a received modulated signal, first comparing means for comparing an output of the correlating means with a predetermined first threshold value, and temporal output of the correlating means. Change amount detecting means for detecting the change amount, second comparing means for comparing the output of the change amount detecting means with a predetermined second threshold value, output of the second comparing means and the first comparison A signal processing device comprising: a synthesizing unit that logically synthesizes an output of the unit. 2. The change amount detecting means includes delay means for delaying the output of the correlating means by a predetermined time, and subtracting means for subtracting the output of the delay means and the output of the correlating means at a predetermined ratio. The signal processing device according to claim 1, comprising: 3. The signal processing apparatus according to claim 1, wherein the correlation means is a digital matched filter. 4. A timing generating means for generating a signal that changes in a predetermined time according to the output of the synthesizing means, and a demodulating means for changing the state of demodulating the output of the correlating means according to the output of the timing generating means. The signal processing device according to claim 1, further comprising: