JPH07131381A - Receiver for spread spectrum communication and method for acquiring synchronization for same - Google Patents

Abstract

PURPOSE:To quickly acquire an initial synchronization in a communication between radio communication equipments using a spread spectrum system with a simple constitution. CONSTITUTION:With a multiplier 8, a reverse spreading code is multiplied to the received signal. The result of the multiplication is integrated by an integration circuit 10. The result of the integration is compared with a threshold value by a threshold circuit 11. A search controller 12 fixes the phase of the reverse spreading code in the case of the synchronization is estabilished as the result of the comparison. The fact that the demodulation is available is reported to a data demodulation circuit 13. As a pseudo noise generator 4 which produces a reverse spreading code, the structure which can produce plural reverse spreading code with dissimilar bit lengths is used. Only when the conditions of the synchronization acquisition is made on the reverse spreading code with the bit length shorter than that at the time of the communication, the synchronization is acquired with the reverse spreading code with the bit length at the time of the communication.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to spread spectrum (S
In S: spread spectrum) communication, pseudo noise (PN:
Pseudo Noise) The present invention relates to a method for establishing synchronization between a sender and a receiver for a code.

[0002]

2. Description of the Related Art In the SS system, a narrow band modulation signal obtained by modulating a carrier wave with a modulation signal such as data or a voice signal is modulated with a pseudo noise (PN) code which is a spread code. It is a communication method in which a frequency band is spread over a wide band and communication is performed using a modulated wave in which the frequency band is spread. For example, a so-called weak SS system is important when performing wireless control of FA, power equipment, and the like. S
In the S method, in order to receive and demodulate (despread) the transmitted wideband modulated wave, it is necessary for the receiving side to establish synchronization of the spreading code with the transmitting side. Usually, in order to establish this synchronization, a synchronization circuit using a delay locked loop (DLL) or the like is used.

FIG. 11 shows an outline of a spread spectrum communication device described in Japanese Patent Laid-Open No. 3-236645. The transmitter Tx includes a spread modulator 1, a pseudo noise generator 3 and an information source 6, and a receiver Rx.
Is a despreading modulator 2, a pseudo noise generator 4 and a synchronization circuit 5.
It consists of

The spread modulator 1 converts the signal from the information source 6 into
Based on the PN code from the pseudo noise generator 3, for example, PSK
Modulate, thereby generating a transmission signal having a wide frequency band. The generated transmission signal is sent to a wired or wireless signal transmission path and transmitted to the reception device Rx.

In the receiving device Rx, the signal received from the transmitting device Tx via a wired or wireless signal transmission path is
Despreading is performed by the despreading modulator 2. That is, the despreading modulator 2 despread-modulates the received signal with the PN code from the pseudo noise generator 4, and outputs the demodulated signal obtained as a result.

In order to perform such demodulation (despreading), the PN code from the pseudo noise generator 4 must be synchronized with the PN code related to the SS added to the received signal. That is, in order to synchronize the PN code, a part of the demodulated signal is input and the PN in the pseudo noise generator 4 is input.
The synchronization circuit 5 for controlling the code generation phase is required. By providing such a synchronization circuit 5, it is possible to synchronize the PN code and demodulate the signal.

FIG. 12 shows a more detailed structure of the receiving device Rx. That is, the despreading modulator 2 described above serves as the multiplier 8, the synchronizing circuit 5 serves as the integrator 10, the threshold circuit 11, and the search controller 12.
It is shown.

The signal S (t) received from the transmission device Tx via the signal transmission line is a BPF that passes only the SS band.
The band is limited by 7 and supplied to the multiplier 8. The PN code is supplied from the pseudo noise generator 4 to the multiplier 8, and the multiplier multiplies the PN code by the output of the BPF 7.
As a result, despreading of the band-limited signal S (t) is performed. The result is an LP that passes only the data band.
It is supplied to F9 to remove unnecessary band and then integrator 1
Supplied to zero.

The integrator 10 integrates the output of the LPF 9 for a time corresponding to one cycle of the PN code. The phase of the PN code output from the pseudo noise generator 4 is the PN related to the signal S (t).
When the phase of the code substantially matches, the correlation value r (t) as a result of the integration becomes large, and otherwise it becomes small. Therefore, the synchronization establishment status of the PN code can be determined depending on whether the correlation value r (t) is large. The threshold circuit 11 is a circuit that executes this determination by comparing the correlation value r (t) with a predetermined threshold value Th. When the former is smaller than the latter, it is determined that the synchronization is not established, and the threshold circuit 11 drives the search controller 12. The search controller 12 controls the pseudo noise generator 4 to shift the phase of the PN code by Δt (bit shift). This bit shift is sequentially executed until the correlation value r (t) becomes equal to or greater than the threshold value Th, and thereby the synchronization of the PN code is established. When the correlation value r (t) becomes equal to or greater than the threshold value Th, the output bit state of the PN code of the pseudo noise generator 4 is fixed. The search controller 12 is
A synchronization establishment signal is supplied to the data demodulation circuit 13. The correlation value r (t) at this time is converted into binary data by the data demodulation circuit 13 according to the synchronization establishment signal, and is output as demodulation data.

FIG. 13 shows the correlation between the correlation value r (t) and the bit shift value Δt of the PN code and the threshold value Th. As shown in this figure, the value of the correlation value r (t) significantly decreases when the phase of the PN code on the transmitting side is shifted by one chip. Therefore, in order to obtain the synchronization, it is important to select the threshold value Th as an appropriate value.

[0011]

As described above, if the PN code is sequentially bit-shifted until the correlation value becomes equal to or more than the predetermined threshold value to obtain the initial synchronization, the synchronization is caused by the phase shift of the PN code. However, if synchronization is not established, a cycle time corresponding to the square of the worst PN code is required to establish synchronization.

To solve this problem, for example, as disclosed in Japanese Patent Laid-Open No. 3-88526, a plurality of despreading circuits are provided and the amount of bit shift in each despreading circuit is made different. Good. However, when such a circuit system is adopted, a plurality of code comparators (integrators,
A threshold circuit, etc.)
This causes problems such as an increase in volume of a wireless communication device using the SS method, an increase in manufacturing cost, and an increase in current consumption.

The present invention has been made in order to solve such a problem, and it is possible to shorten the time required for initial synchronization acquisition without using a plurality of code comparators and with a simple structure. To aim.

[0014]

In order to achieve such an object, a receiver for spread spectrum communication according to the present invention comprises:
Correlation value calculation means for calculating the correlation value of the received signal that has been spread spectrum modulated by the despreading code and the spreading code for communication, and the despreading code of the despreading code when the correlation value of the despreading code and the received signal is lower than a predetermined value. Correlation determination means for repeatedly performing the calculation of the correlation value by sequentially changing the phase, and determining that the despreading code is synchronized with the communication spreading code when the value is higher than a predetermined value, the correlation value calculating means and / or the correlation value By controlling the operation of the determination means, an initial synchronization acquisition means for establishing the synchronization between the despread code and the received signal at an early stage is provided.

A first synchronization establishment method of the present invention is a reception that is spread spectrum modulated by a first despreading code and a communication spreading code that are shorter than the communication spreading code and have a partial configuration common to the communication spreading code. The correlation value of the signal is calculated, and when the correlation value of the first despread code and the received signal is lower than the first predetermined value, the phase of the first despread code is sequentially changed to repeatedly execute the calculation of the correlation value. If it is higher than the first predetermined value, the correlation value between the second despreading code having the same configuration and the same length as the communication spreading code and the reception signal is calculated, and the correlation value between the second despreading code and the reception signal is the second predetermined value. It is characterized in that the second despreading code is considered to be synchronized with the communication spreading code when it is higher than the value.

A second synchronization establishing method of the present invention is characterized in that, in the first synchronization establishing method, the first despreading code is a part of the second despreading code.

A third synchronization establishing method of the present invention stores the phase of the first despreading code which maximizes the correlation value between the first despreading code and the received signal in the first synchronization establishing method,
It is characterized in that the second despread code is generated in this phase.

A fourth synchronization establishing method of the present invention calculates a correlation value of a reception signal which is spread spectrum modulated by a despreading code having the same configuration and length as the spreading code for communication and a spreading code for communication, and despreading. When the correlation value between the code and the received signal is lower than the predicted correlation value obtained according to the synchronization probability, the phase of the despread code is sequentially changed and the above correlation value is repeatedly calculated, and when it is higher than the predicted correlation value. Is characterized in that the despreading code is considered to be synchronized with the communication spreading code.

The fifth synchronization establishing method of the present invention is as follows:
If the correlation value of the received signal that has been spread spectrum modulated by the despreading code and the spreading code for communication with the same configuration as the spreading code for communication and the spreading code for communication is calculated, and the correlation value between the despreading code and the received signal is lower than a predetermined value Sequentially changes the phase of the despreading code and repeatedly executes the calculation of the above correlation value. If it is higher than a predetermined value, it is considered that the despreading code is synchronized with the communication spreading code, and the phase of the despreading code is When the correlation value between the despreading code and the received signal continues to fall below a predetermined value even if the period is changed, the phase of the despreading code is changed by the half period and the calculation of the correlation value is started.

[0020]

In the spread spectrum communication receiver of the present invention, the correlation value calculation means calculates the correlation value of the received signal which is spread spectrum modulated by the despread code and the communication spread code. When the calculated correlation value is lower than the predetermined value, the correlation determining unit sequentially changes the phase of the despreading code (that is, shifts the bits) and repeatedly executes the calculation of the correlation value. On the contrary, when the value is higher than the predetermined value, the correlation determining unit considers that the despreading code is synchronized with the communication spreading code. The initial synchronization acquisition means then controls the operation of the correlation value calculation means and / or the correlation value determination means,
Early establishment of synchronization between the despread code and the received signal. That is, rather than using a plurality of code comparators for correlation calculation and determination, initial synchronization can be obtained by controlling the correlation calculation and determination operation, and the time required for initial synchronization acquisition can be shortened with a simple device configuration.

As a method for obtaining the initial synchronization by controlling the correlation calculation and the judgment operation, five kinds of methods can be proposed as described above.

In the first synchronization establishing method, two types of despreading codes are used. Among them, the first despreading code is a code shorter than the communication spreading code and a part of the configuration is common to the communication spreading code, and the second despreading code is a code having the same configuration and the same length as the communication spreading code. . In this method, first, the correlation value between the first despreading code and the received signal is calculated. When the correlation value between the first despread code and the received signal is lower than the first predetermined value, the correlation value is repeatedly calculated while sequentially changing the phase of the first despread code. On the contrary, when the correlation value between the second despread code and the received signal is higher than the first predetermined value, and when the correlation value between the second despread code and the received signal is higher than the second predetermined value, the second The despread code is considered to be synchronized with the communication spread code. Therefore, in this method, since the correlation is first obtained by the despreading code having a short bit length and then the synchronization is made by the despreading code having the same length as the communication spreading code, the synchronization can be accelerated.

In the second synchronization establishing method, a part of the second despreading code is used as the first despreading code. That is, first, the correlation with a part of the second despreading code is calculated,
The result is used for the determination, and after the above condition is satisfied, the synchronization by the second despreading code is tried. Therefore, it is not necessary to prepare two types of despreading codes.

In the third synchronization establishing method, the phase of the first despread code that maximizes the correlation value between the first despread code and the received signal is stored, and the second despread code is generated at this phase. . Therefore, the synchronization can be acquired earlier.

In the fourth synchronization establishing method, the correlation value between the despread code and the received signal is compared with the predicted correlation value obtained according to the synchronization probability. That is, since the correlation determination is performed using the predicted correlation value, the establishment of synchronization can be detected more accurately.

Then, in the fifth synchronization establishing method,
When determining the correlation, if the correlation value between the despreading code and the received signal continues to fall below a predetermined value even if the phase of the despreading code is changed by one cycle, the correlation value is changed by changing the phase of the despreading code by half the cycle. The calculation of is started. Therefore, the time required for synchronization acquisition is shortened.

[0027]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will be described below with reference to the drawings. Note that the same or corresponding configurations as those of the conventional example shown in FIGS. 11 and 12 are designated by the same reference numerals, and the description thereof will be omitted.

First Embodiment FIG. 1 shows the configuration of a receiving device Rx in the first embodiment of the present invention. Further, FIG. 2 shows the synchronization establishment control operation by the search controller 12 in this embodiment. The configuration of this embodiment is partly common to the above-described conventional example, but is largely different in that the pseudo noise generator 4 can generate a plurality of despread codes (PN codes) having different bit lengths. . The first of the despread codes generated by the pseudo noise generator 4 is a code having the same bit length as the PN code used for communication from the transmitter Tx (hereinafter,
The second one is a communication bit length despreading code) and the second one is a code which is shorter and has the same configuration as a part of the communication bit length despreading code (hereinafter referred to as a shortened bit length despreading code). Corresponding to this, the threshold circuit 1
1 is the threshold value Th for each despreading code.
Is set.

As shown in FIG. 2, when the signal S (t) is received from the transmission device Tx via the signal transmission line after the operation is started (100), first, the pseudo noise generator 4 despreads the shortened bit length. The code is output (102). That is, a trial of synchronization by the shortened bit length despreading code is started. B
The shortened bit length despreading code is multiplied by the multiplier 8 on the signal S (t) whose band is limited by the PF 7. The output of the multiplier 8 is filtered by the LPF 9 and then
It is integrated by the integrator 10. The threshold circuit 11 compares the correlation value r (t), which is an integrated value, with the threshold value Th, and the comparison result is the search controller 12
To enter. The integration period of the integrator 10 and the threshold value Th are set in advance by the search controller 12 to values corresponding to the shortened bit length despreading code. For example, the integration period is set to the time corresponding to one cycle of the shortened bit length despreading code.

The search controller 12 uses the correlation value r
It is determined whether (t) is greater than or equal to the threshold value Th, that is, whether synchronization has been established for the shortened bit length despreading code (104). Judgment result, correlation value r
If (t) is not equal to the threshold value Th and synchronization is not established, the search controller 1
2 instructs the pseudo noise generator 4 to continuously generate the shortened bit length despreading code and shift the code by Δt (106). Further, for the integrator 10, the fact that the integration period is continuously set to one cycle of the shortened bit length despreading code is set, and for the threshold circuit 11, the threshold value Th is continuously set for the shortened bit length despreading code. To set the value of
Command each. After that, the above-described operation is performed in step 10.
It is repeated until the condition of 4 is satisfied.

When it is determined in step 104 that the correlation value r (t) is greater than or equal to the threshold value Th and synchronization is established, the search controller 12 instructs the pseudo noise generator 4 to despread the communication bit length. Is output (108), the integration period is subtracted from the integrator 10, and one cycle of the communication bit length despreading code is set, and the threshold value is input to the threshold circuit 11. It is instructed to set Th to a value for the communication bit length despreading code. The multiplier 8 is
The communication bit length despreading code is multiplied by the signal S (t) whose band is limited by the BPF 7. The output of the multiplier 8 is LP
After being filtered by F9, it is integrated by the integrator 10. The threshold circuit 11 compares the correlation value r (t), which is an integral value, with the threshold value Th, and inputs the comparison result to the search controller 12.

The search controller 12 uses the correlation value r
It is determined whether (t) is greater than or equal to the threshold value Th, that is, whether synchronization has been established for the communication bit length despreading code (110). Judgment result, correlation value r
When (t) does not reach the threshold value Th and the synchronization is not established, the search controller 12 stops the attempt of synchronization by the communication bit length despreading code and shortens the pseudo noise generator 4. A bit length despreading code is generated and an instruction to shift the code by Δt is issued (112, 106). In addition, the threshold circuit 1 indicates that the integration period is set to one cycle of the shortened bit length despreading code for the integrator 10.
For 1, it is instructed to set the threshold value Th to a value for the shortened bit length despreading code.
After that, the above-described operation is repeated until the conditions of steps 104 and 110 are satisfied.

The search controller 12 executes step 10
4 and 110 are satisfied, the pseudo noise generator 4
The bit state of the despreading code is fixed, the synchronization establishment signal is supplied to the data demodulation circuit 13, and data demodulation is started.

Therefore, according to this embodiment, the possibility of establishing synchronization is judged by the correlation calculation of the shortened bit length despreading code, and the synchronization establishment is attempted by the communication bit length despreading code. Can be speeded up.

Second Embodiment FIG. 3 shows the configuration of the receiver Rx in the second embodiment of the present invention, and FIG. 4 shows the flow of the synchronization establishing operation by the search controller 12 thereof. This embodiment is different from the first embodiment mainly in that the memory 14 is provided. The memory 14 is used to store the maximum value (maximum correlation value) of the correlation value r (t) obtained by the integrator 10 and the bit shift amount Δt corresponding to this correlation value r (t).

After executing steps 100 and 102 as in the first embodiment, the search controller 12 compares the correlation value r (t) obtained from the integrator 10 with the maximum correlation value on the memory 14 (112). ). As a result of comparison, the correlation value r
If (t) is less than or equal to the maximum correlation value on the memory 14, the search controller 12 executes step 106. Therefore, steps 106 and 112 are repeatedly executed until the correlation value r (t) exceeds the maximum correlation value on the memory 14.

When the correlation value r (t) obtained from the integrator 10 exceeds the maximum correlation value on the memory 14, the search controller 12 causes the correlation value r (t) at that time and the bit shift amount Δt corresponding thereto. Stored in the memory 14 (1
14). The search controller 12 repeats the operations of steps 106, 112, and 114 over one cycle of the shortened bit length despreading code (116). After that, the search controller 12 reads the maximum correlation value and the corresponding bit shift amount Δt on the memory 14 (118), shifts the bit shift amount Δt corresponding to the maximum correlation value, and at the same time, the communication bit length despread code. Is generated (12
0). This attempts to establish synchronization. As a result of this trial, if it is determined in step 110 that synchronization has not been established, the process returns to step 102. When it is determined that the synchronization has been established, the output bit state of the pseudo noise generator 4 is fixed and the synchronization establishment signal is output.

Therefore, in this embodiment as well, the possibility of establishing synchronization is judged by the correlation calculation of the shortened bit length despreading code, and the synchronization establishment is attempted by the communication bit length despreading code. Can be converted. Further, since the maximum correlation value is stored in the memory 14 together with the bit shift amount, it is possible to accurately grasp the phase information with which the maximum correlation is obtained, and more accurate initial synchronization can be realized.

Third Embodiment FIG. 5 shows the configuration of the receiver Rx in the third embodiment of the present invention, and FIG. 6 shows the flow of the synchronization establishing operation by the search controller 12 thereof. This embodiment is largely different from the first embodiment in that there is one type of despreading code, and the determination based on the threshold value Th is executed even in the middle of the cycle of the despreading code (for example, half cycle).

When the signal is received (100), the search controller 12 waits for a time corresponding to a partial cycle of the despreading code generated by the pseudo noise generator 4, for example, a half cycle (114). Meanwhile, for this signal, the correlation value with the despreading code generated by the pseudo noise generator 4 is calculated by the integrator 10. Since this correlation value is an integral value in a partial cycle of the despreading code, it will be referred to as a temporary correlation value hereinafter. The threshold circuit 11 compares the temporary correlation value with the threshold value Th set by the search controller 12, and supplies the result to the search controller 12. The search controller 12 is
Until the temporary correlation value becomes equal to or larger than the threshold value Th (116), step 106 is executed and then the operations after step 114 are repeated.

The temporary correlation value is the threshold value Th.
When the above is reached, the search controller 12 waits for a period corresponding to one cycle of the despreading code (118). The integrator 10 integrates the output of the LPF 9 for a period corresponding to one cycle of the despreading code and outputs it as a correlation value r (t). Search controller 12
Executes step 110 based on this correlation value r (t).

Therefore, in this embodiment, the possibility of establishing the synchronization is judged by the correlation calculation for a part of the despreading code (for example, half cycle), and then the establishment of the synchronization by the full length of the despreading code is tried. The synchronization acquisition can be speeded up. Further, substantially the same operation as that of preparing a plurality of types of despreading codes occurs without actually preparing a plurality of types of despreading codes.

Fourth Embodiment FIG. 7 shows the configuration of the receiving device Rx in the fourth embodiment of the present invention, and FIG. 8 shows the operation flow of the search controller 12 in this embodiment. In this embodiment, one kind of despreading code is used as in the third embodiment, and the memory 14 is used as in the second embodiment. The memory 14 stores in advance a predicted correlation value determined by establishing synchronization or the like.

When the signal is received (100), the search controller 12 compares the output of the integrator 10 with the predicted correlation value in the memory 14 (120), and if the output of the integrator 10 is not greater than or equal to the predicted correlation value. (122), step 10
After step 6, the operations from step 120 onward are repeated. When the output of the integrator 10 is equal to or higher than the predicted correlation value up to the final bit of the despreading code (124), the search controller 12 determines that the synchronization is established and supplies the data demodulation circuit 13 with the synchronization establishment signal output. To do.

Therefore, in this embodiment, since the synchronization acquisition is tried based on the result of comparison with the predicted correlation value, the initial synchronization acquisition can be speeded up.

Fifth Embodiment FIG. 9 shows the configuration of the receiving device Rx in the fifth embodiment of the present invention, and FIG. 10 shows the operation flow of the search controller 12 in this embodiment.

When the signal is received (100), the integrator 1
The output of 0 is compared with the threshold value, and the determination of synchronization establishment is executed by the search controller 12 (110). When the search controller 12 does not establish synchronization despite performing the bit shift (106, 124) for one cycle of the despreading code a plurality of times (three times in FIG. 10) (126), the components in the integrator 10 are The bit position to be started, that is, the position of the correlation start bit is changed to a position shifted by, for example, half the bit length of the despreading code (128), and the correlation calculation is repeated. When the synchronization is established, the search controller 12 outputs a synchronization establishment signal to the data demodulation circuit 13.

Therefore, in this embodiment, the synchronization timing is preferably detected by changing the position of the correlation start bit when the synchronization is not established.
The initial synchronization acquisition can be speeded up.

Addendum In the above description, the configuration having one set of the multiplier 8, the LPF 9, the integrator 10 and the pseudo noise generator 4 has been described.
It goes without saying that the present invention can be applied to a configuration of two or more sets. Also, it goes without saying that combinations of the respective embodiments are possible.

[0050]

As described above, according to the spread spectrum communication receiver of the present invention, the correlation value calculating means and / or
Alternatively, by controlling the operation of the correlation value determination means, the despreading code and the received signal are synchronized at an early stage, so that a plurality of code comparators are not used for correlation calculation and determination, that is, with a simple device configuration. , The synchronization acquisition time can be shortened.

According to the first synchronization establishing method of the present invention, the correlation is first obtained by the despreading code having a short bit length, and then the synchronization is attempted by the despreading code having the same length as the communication spreading code. Therefore, synchronization can be accelerated.

According to the second synchronization establishing method of the present invention, since a part of the second despreading code is used as the first despreading code, it is not necessary to prepare two types of despreading codes.

According to the third synchronization establishing method of the present invention, the phase of the first despreading code having the maximum correlation value between the first despreading code and the received signal is stored, and the second despreading code is stored as this phase. Since it is generated by, the synchronization can be acquired earlier.

According to the fourth synchronization establishing method of the present invention, the correlation value between the despreading code and the received signal is compared with the predicted correlation value obtained according to the synchronization probability. It becomes possible to detect accurately.

Further, according to the fifth synchronization establishing method of the present invention, at the time of correlation determination, the correlation value between the despread code and the received signal falls below a predetermined value even if the phase of the despread code is changed by one cycle. When it is continued, the phase of the despreading code is changed by half its period to start the calculation of the correlation value, so that the time required for synchronization acquisition is shortened.

[Brief description of drawings]

FIG. 1 is a block diagram showing an outline of a configuration of a receiving device according to a first embodiment of the present invention.

FIG. 2 is a flowchart showing a flow of a synchronization establishing operation in this embodiment.

FIG. 3 is a block diagram showing an outline of a configuration of a receiving device according to a second embodiment of the present invention.

FIG. 4 is a flowchart showing a flow of a synchronization establishing operation in this embodiment.

FIG. 5 is a block diagram showing an outline of a configuration of a receiving device according to a third embodiment of the present invention.

FIG. 6 is a flowchart showing a flow of a synchronization establishing operation in this embodiment.

FIG. 7 is a block diagram showing an outline of a configuration of a receiving device according to a fourth embodiment of the present invention.

FIG. 8 is a flowchart showing a flow of a synchronization establishing operation in this embodiment.

FIG. 9 is a block diagram showing an outline of a configuration of a receiving device in a fifth embodiment of the present invention.

FIG. 10 is a flowchart showing a flow of a synchronization establishing operation in this embodiment.

FIG. 11 is a block diagram showing an outline of a wireless communication device using a spread spectrum system according to a conventional example.

FIG. 12 is a block diagram showing an outline of the configuration of a receiving apparatus in this conventional example.

FIG. 13 is a diagram showing a correlation between a correlation value r (t) after despreading and a bit shift value and a threshold value of the PN code in the receiving side device in the conventional example.

[Explanation of symbols]

 Tx transmitter Rx receiver 1 Spreading modulator 2 Despreading modulator 3,4 Pseudo noise generator 5 Synchronization circuit 6 Information source 7 BPF 8 Multiplier 9 LPF 10 Integrator 11 Threshold circuit 12 Search controller 13 Data demodulation circuit 14 Memory r (t) Correlation output Δt Bit shift value

Claims (6)

[Claims] 1. Correlation value calculating means for calculating a correlation value of a received signal which is spread spectrum modulated by a despreading code and a communication spreading code, and when the correlation value of the despreading code and the received signal is lower than a predetermined value. Is a correlation determination means for sequentially changing the phase of the despreading code to repeatedly execute the calculation of the correlation value, and if the despreading code is higher than a predetermined value, it is considered that the despreading code is synchronized with the communication spreading code, and a correlation value calculating means. And / or an initial synchronization acquisition means for early establishing synchronization between the despread code and the received signal by controlling the operation of the correlation value determination means, and a receiver for spread spectrum communication. 2. A correlation value of a reception signal which is spread spectrum modulated by a first despreading code and a spreading code for communication, a part of which is shorter than the spreading code for communication and is common to the spreading code for communication, and When the correlation value between the one despreading code and the received signal is lower than the first predetermined value, the phase of the first despreading code is sequentially changed to repeatedly execute the calculation of the correlation value, and when the correlation value is higher than the first predetermined value. Calculates a correlation value between the second despreading code having the same structure and the same length as the communication spreading code and the received signal, and when the correlation value between the second despreading code and the received signal is higher than the second predetermined value, the second inverse spread A method for establishing synchronization characterized in that the spreading code is regarded as synchronized with the spreading code for communication. 3. The synchronization establishing method according to claim 2, wherein the first despreading code is a part of the second despreading code. 4. The synchronization establishing method according to claim 2, wherein the phase of the first despreading code that maximizes the correlation value between the first despreading code and the received signal is stored, and the second despreading code is stored as the second despreading code. A method of establishing synchronization characterized by generating in phase. 5. A correlation value of a reception signal that is spread spectrum modulated by a despreading code and a communication spreading code having the same structure as that of the communication spreading code, and the correlation value of the despreading code and the received signal is synchronized. If it is lower than the predicted correlation value obtained according to the probability, the phase of the despreading code is sequentially changed to repeatedly execute the calculation of the correlation value,
A method for establishing synchronization characterized in that the despreading code is considered to be synchronized with the spreading code for communication when it is higher than the predicted correlation value. 6. A correlation value of a reception signal which is spread spectrum modulated by a despreading code and a communication spreading code having the same configuration and the same length as the communication spreading code, and a correlation value between the despreading code and the received signal is predetermined. When it is lower than the value, the phase of the despreading code is sequentially changed and the above correlation value is repeatedly calculated. When it is higher than a predetermined value, it is considered that the despreading code is synchronized with the communication spreading code, and the despreading code is calculated. When the correlation value between the despreading code and the received signal continues to fall below a predetermined value even if the phase of the despreading code is changed by one period, the phase of the despreading code is changed by the half period and the calculation of the correlation value is started. The method of establishing synchronization.