JPH0440124A - Digital correlation device - Google Patents

Abstract

PURPOSE:To instantaneously obtain correlation without being affected by a phase by deciding the degree of correlation between a spread spectrum reception (SS) signal and a spreading code by fetching the number of coincident bits between the respectively detected SS signal and the spreading code by each coincidence detection signal each time one cycle of the spreading code passes while inverting the phase of the SS signal or of the spreading code. CONSTITUTION:Each time a first coincidence detection circuit 31 detects the coincidence by exclusively ORing the SS signal, which phase is inverted by a phase inversion circuit 7, and the spreading code to be outputted from a spreading code generation circuit 2, a coincidence signal is outputted and the number of the signals is counted by a first counter circuit 51. On the other hand, a second coincidence detection circuit 32 similarly detects coincidence between the SS signal, which phase is not inverted, to be applied from a buffer circuit 8 and the spreading code for each bit, and a second counter circuit 52 counts the number of coincidence signals. On the other hand, each time one cycle of the spreading code to be outputted from the spreading code generation circuit 2 passes, a control circuit 9 respectively reads the count values of the first and second counter circuits 51 and 52 and decides the degree of correlation.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a digital correlator used in spread spectrum communication and the like.

[Conventional technology]

FIG. 3 is a block diagram showing a conventional digital correlator disclosed in, for example, Japanese Unexamined Patent Publication No. 1-319862. 2 is a spreading code generating circuit that generates a spreading code to be included in this SS signal. Reference numeral 3 designates a coincidence detection circuit 1, which uses an SS signal and a spreading code as input signals, and detects coincidence of each bit of these two signals, for example, by an exclusive OR circuit.

Reference numeral 4 denotes a phase switching circuit which switches the phase of the SS signal inputted from the input terminal 1 and inputs it to the coincidence detection circuit 3 either as a positive phase or inverted to an opposite phase. Reference numeral 5 denotes a counter or circuit for counting the number of matching bits between the SS signal detected by the matching detection circuit 3 and the spreading code. 6 takes in the count value of the counter circuit 5 every time one period of the spreading code passes, and based on it, determines the degree of correlation between the SS signal and the spreading code, and if it is determined that there is no correlation, the phase This is a control circuit that instructs the switching circuit 4 to switch the phase of the SS signal.

Next, the operation will be explained. First, the control circuit 6 sends a control signal to the phase switching circuit 4 to set the state of the one-phase switching circuit 4 so that, for example, the input SS signal is output as is without phase inversion. As a result, the -number construction circuit 3 performs the exclusive OR of the spreading code generated by the spreading code generation circuit 2 and this SS signal to detect coincidence for each bit. The detection result is sent to the counter circuit 5, and the counter circuit 5 counts the number of matching signals.

Here, when one period of the spreading code has passed, the control circuit 6 reads the counted value from the counter circuit 5, and at the same time resets the counter circuit 5 to clear the counted value.
Next, the control circuit 6 calculates a correlation value based on the read count value and compares it with a predetermined reference value. the result.

If the calculated correlation value is larger than the reference value, it means that the SS signal and the spreading code are correlated, so this series of processing is completed and the processing is passed to the synchronization routine.

Also, if the correlation value is smaller than the reference value, the signal is sent to an SS destined for another station whose spreading code on the transmitting side is different from that of the own station.
There is a high possibility that it is a signal or noise, but it is also possible that the phase of the SS signal and the phase of the spreading code are completely opposite.

Therefore, the control circuit 6 sends a control signal to the phase switching circuit 4 to set the state of the phase switching circuit 4 so that the phase of the input SS signal is inverted and output. below,
As in the case described above, the minus number generation circuit 3 detects a bit-by-bit coincidence between the spreading code and the phase-inverted SS signal, the counter circuit 5 counts the number of coincidence signals, and the control circuit 6 The degree of correlation is determined from the correlation value based on the counted value.

As a result, if the correlation value is smaller than the reference value, the phase of the SS signal is inverted again and the above operation is repeated.

Furthermore, if a correlation cannot be taken because the phase of the SS signal addressed to the own station is inverted, the correlation value becomes larger than the reference value due to the phase inversion of the SS signal. Therefore, the SS signal has a correct correlation with the spreading code.

[Problem to be solved by the invention]

Since the conventional digital correlator is configured as described above, when receiving an SS signal whose phase is inverted depending on marks and spaces of the data to be transmitted on the transmitting side, each time the phase of the SS signal is inverted, Whenever the correlation is lost, it is necessary to invert the phase of the SS signal and redetect the correlation between the SS signal and the spreading code over one period of the spreading code. Therefore, when the phase of the SS signal is reversed, the spreading code There is a period of time during which no correlation can be established, and it takes a long time for the SS signal and the spreading code to be correlated. If the signal is assigned, the phase will be opposite to the SS signal and no correlation will be detected even if correlation detection is performed.
There were issues such as the inability to receive data.

This invention was made to solve the above-mentioned problem, and it can instantly convert an SS signal whose phase is inverted depending on the marks and spaces of the data to be transmitted, without being affected by the phase. The purpose is to obtain a digital correlator that can correlate with the spreading code.

[Means to solve the problem]

The digital correlator according to the present invention includes two coincidence detection circuits that detect coincidence between each bit of an SS signal and a spreading code, and inverts the phase of the SS signal or spreading code input to one of the coincidence detection circuits. Each time the phase inversion circuit and the spreading code pass one period, the number of matching bits between the SS signal and the spreading code detected by each minus number detection circuit is taken in, and the SS signal and the spreading code are spread based on the number of matching bits. A control circuit for determining the degree of correlation with the code is provided.

[Effect]

The control circuit in the present invention includes a first counter circuit that counts the number of matching bits between the SS signal and the spreading code detected by the first matching detection circuit, in which the phase of either the SS signal or the spreading code is inverted. of a second counter circuit that counts the number of matching bits between the SS signal and the spreading code detected by the second matching detection circuit in which neither the SS signal nor the spreading code is phase inverted. The count value is captured every time one period of the spreading code passes, and the degree of correlation between the SS signal and the spreading code is determined based on each captured count value. To realize a digital correlator that can instantaneously take the correlation with a spreading code without being affected by the phase of an SS signal, even if the phase is inverted.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings. 1st
In the figure, 1 is an input terminal, 2 is a spreading code generation circuit,
These parts are the same as or equivalent to those in the prior art, which are denoted by the same reference numerals in FIG. Reference numerals 31 and 32 denote first and second coincidence detection circuits which receive the SS signal and the spreading code as input signals and detect coincidence of each bit of these two signals.These first and second coincidence detection circuits 31 and 32 have the same configuration as the conventional coincidence detection circuit 3.

51 is a first counter circuit that counts the number of matching bits between the SS signal and the spreading code detected by the first matching detection circuit 31; This is a second counter circuit that counts the number of matching bits between the SS signal and the spreading code. These first and second
The counter circuits 51 and 52 also have the same configuration as the conventional counter circuit 5.

A phase inversion circuit 7 inverts the phase of the SS signal input to the input terminal 1 and inputs the same to the first coincidence detection circuit 31. 8, the phase inversion circuit 7 supplies the phase-inverted SS signal to the first coincidence detection circuit 31, and the phase inversion circuit 7 supplies the phase-inverted SS signal to the second coincidence detection circuit 31 without inverting the phase of the SS signal.
This is a buffer circuit that inputs input to the coincidence detection circuit 32 of.

9 reads the count values of the first counter circuit 51 and the second counter circuit 52 every time one period of the spreading code passes, calculates each correlation value, and calculates each correlation value according to a preset standard. This is a control circuit that determines the degree of correlation between the SS signal and the spreading code by comparing the values.

Next, the operation will be explained. Here, FIG. 2 is a flowchart showing the operating procedure.

When the digital correlator starts operating, the control circuit 9
First, the spreading code generating circuit 2, the first . The second coincidence detection circuits 31, 32, the first . Second counter circuits 51, 52 .
Phase inversion circuit 7. and the buffer circuit 8, initial settings such as reset are performed (step 5TI). Next, the control circuit 9 controls the spreading code generation circuit 2, the first . Second coincidence detection circuit 31.32. 1st. Second counter circuit 51°52
An instruction is given to start correlation processing to (step 5T2).

As a result, the first coincidence detection circuit 31 calculates the exclusive OR of the SS signal whose phase has been inverted by the phase inversion circuit 7 and the spreading code output from the spreading code generation circuit 2, and calculates the A match is detected and a match signal is output every time a match is detected. This coincidence signal is sent to the first counter circuit 5.
1 and counted. In addition, the second coincidence detection circuit 3
Similarly, the second counter circuit 52 performs coincidence detection for each bit of the SS signal, which is not subjected to phase inversion, provided by the buffer circuit 8 and the spreading code, and the second counter circuit 52 counts the coincidence signals.

On the other hand, each time one period of the spreading code output from the spreading code generation circuit 2 passes, the control circuit 9 reads the count values of the first counter circuit 51 and the second counter circuit 52 (step 5T3), Simultaneously with reading this count value, the control circuit 9 controls the first and second counter circuits 5.
1 and 52 to clear their count values (step 5T4). Next, the control circuit 9 calculates each correlation value based on the count values read from each counter circuit 51 and 52 (step 5T4). step 5T5), and comparing each obtained correlation value with a preset reference value to identify the magnitude relationship step 5T6);
The degree of correlation is determined.

That is, if all of the calculated correlation values are smaller than the reference value, it means that the SS signal input from the input terminal 1 and the spreading code output from the spreading code generating circuit 2 cannot be correlated. This means that there is a high possibility that the signal is an SS signal addressed to another station whose spreading code on the transmitting side is different from that of the own station, or is noise. In such a case, the processing is changed from step ST6 to step ST2. Returning to the spreading code generation circuit 2. 1st. The second coincidence detection circuit 31°32, the first . The second counter circuits 51 and 52 are instructed to start correlation processing again.

On the other hand, if either of the correlation values calculated in step ST5 is equal to or greater than the reference value, it means that the SS signal and the spreading code are correlated, and regardless of whether the phase of the SS signal is positive or negative, the correlation is It shows that it can be removed. Therefore, regardless of whether the phase of the SS signal input to the input terminal 1 is positive or negative, the SS signal has a correlation with the spreading code output from the spreading code generating circuit 2, and the mark and the mark of the data to be transmitted are maintained. Even when an SS signal whose phase is inverted due to space is received, the correlation operation can be performed without considering the phase inversion of the received signal.

If it is determined in step ST6 that one of the correlation values is greater than or equal to the reference value, this series of processing is ended and the processing is passed to the synchronization routine.

In the above embodiment, the main body of the control circuit calculates each correlation value based on the count values read from the first and second counter circuits, and compares them with a reference value to determine the degree of correlation. However, a comparison circuit is provided separately within the control circuit, and first, this comparison circuit compares the count values from the first and second counter circuits with the reference value, and the comparison results are sent to the main body of the control circuit. By configuring it in this way, the load on the control circuit body can be reduced.

Furthermore, in the above embodiment, a case has been described in which the phase of the SS signal is inverted by the phase inversion circuit and inputted to the first coincidence detection circuit, but the SS signal is inputted to the first coincidence detection circuit with the same phase.
The spreading code outputted from the spreading code generating circuit may be inputted to the first matching detection circuit, and the phase of the spreading code output from the spreading code generating circuit may be inverted and inputted to the first matching detection circuit, and the same effect as in the above embodiment can be obtained.

〔Effect of the invention〕

As described above, according to the present invention, two coincidence detection circuits for detecting coincidence between each bit of an SS signal and a spreading code are prepared, and the phase of the SS signal or spreading code input to one of the coincidence detection circuits is A phase inversion circuit is provided to invert the spread code, and the control circuit takes in the number of matching bits between the SS signal and the spreading code detected by each negative output circuit for each period of the spreading code, and calculates the number of matching bits based on the number of matching bits. Since the configuration is configured so that the degree of correlation between the SS signal and the spreading code is determined by I was able to draw a correlation with

Even when receiving an SS signal whose phase is inverted depending on the marks and spaces of the data to be transmitted, correlation operation can be performed without considering the phase inversion of the received signal.
Furthermore, correlation with the received signal is instantaneous and there is no delay.
This has the effect of providing a digital correlator that can shorten the time from reception to synchronization.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing a digital correlator according to an embodiment of the present invention, FIG. 2 is a flow chart showing its operating procedure, and FIG. 3 is a block diagram showing a conventional digital correlator. 2 is a spreading code generation circuit, 31 is a first coincidence detection circuit, 3
2 is a second coincidence detection circuit, 51 is a first counter circuit,
52 is a second counter circuit, 7 is a phase inversion circuit, and 9 is a control circuit. In addition, in the figures, the same reference numerals indicate the same or equivalent parts. Diagram

Claims (1)

[Claims] a spreading code generating circuit that generates a spreading code to be included in a digitized spread spectrum reception signal; Second
a coincidence detection circuit, a phase inversion circuit that inverts one phase of the input signal of the first coincidence detection circuit, and the spread spectrum received signal and the spread code detected by the first coincidence detection circuit. a first counter circuit that counts the number of matching bits between the spread spectrum received signal and the spread code detected by the second matching detection circuit; a control circuit that determines the degree of correlation between the spread spectrum received signal and the spread code based on the count values of the first and second counter circuits that are captured every time one period of the spread code passes; Digital correlator with.