Timing detection device and timing detection method

Abstract

[Problem] To suppress a side lobe at correlation processing time. [Solution] A correlation unit 52 comprises a main reference code generator 525, an auxiliary reference code generator 526, a correlation processor 521, a correlation processor 522, and a difference unit 523. The main reference code generator 525 generates a main reference code comprising the same code as the code for synchronization that is included in a received signal. The auxiliary reference code generator 526 generates, using part of the same code as the code for synchronization, an auxiliary reference code comprising a code structure different from the main reference code, with which there is no occurrence of a main lobe at correlation processing time. The correlation processor 521 correlatively processes the received signal and the main reference code and outputs a first correlation processing result. The correlation processor 522 correlatively processes the received signal and the auxiliary reference code and outputs a second correlation processing result. The difference unit 523 calculates the difference between the first and the second correlation processing results.

Description

[Technical Field]

[0001] The present invention relates to a technique for detecting timing when receiving a digitally modulated signal. [Background technology]

[0002] Patent Document 1 describes a wireless communication method and device for receiving a signal modulated with a Barker code. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2005-311532 Summary of the Invention [Problem to be solved by the invention]

[0004] However, when correlation processing is performed using a conventional spreading code such as a Barker code to detect predetermined timing such as slot timing, a relatively large side lobe occurs in the correlation processing result, which can cause errors in the detected timing.

[0005] Therefore, an object of the present invention is to suppress side lobes during correlation processing. [Means for solving the problem]

[0006] The timing detection device of the present invention comprises a main reference code generator, an auxiliary reference code generator, a first correlator, a second correlator, and a differentiator. The main reference code generator generates a main reference code consisting of the same code as the synchronization code included in the received signal. The auxiliary reference code generator uses a portion of the same code as the synchronization code to generate an auxiliary reference code having a code structure different from that of the main reference code and which does not produce a main lobe during correlation processing. The first correlator correlates the received signal with the main reference code and outputs a first correlation processing result. The second correlator correlates the received signal with the auxiliary reference code and outputs a second correlation processing result. The differentiator obtains a difference between the first correlation processing result and the second correlation processing result.

[0007] In this configuration, the side lobes of the first correlation processing result and the side lobes of the second correlation processing result cancel each other out in the output of the differentiator. [Effects of the Invention]

[0008] According to the present invention, side lobes during correlation processing can be suppressed. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a functional block diagram of a correlation unit according to an embodiment of the present invention. [Figure 2] FIG. 2 is a functional block diagram of the automatic identification system of a vessel according to the embodiment of the present invention. [Figure 3] FIG. 3 is a diagram showing an example of the data structure of an automatic identification signal for vessels. [Figure 4] FIG. 4 is a diagram showing an example of a bit arrangement of SW (Syncword) data. [Figure 5] FIG. 5(A) is a diagram showing an example of a bit arrangement of a main reference code according to the first embodiment, and FIG. 5(B) is a diagram showing an example of a bit arrangement of an auxiliary reference code according to the first embodiment. [Figure 6]Figures 6(A) and 6(B) are figures showing the correlation results (first correlation processing results) between SW data and main reference code, and Figures 6(C) and 6(D) are figures showing the correlation results (second correlation processing results) between SW data and auxiliary reference code. [Figure 7] FIG. 7 is a diagram showing the final correlation processing result (final correlation processing data). [Figure 8] FIG. 8 is a flowchart showing an example of a timing detection method according to an embodiment of the present invention. [Figure 9] Figure 9(A) is a diagram showing an example of a bit arrangement of a main reference code according to the second embodiment, and Figure 9(B) is a diagram showing an example of a bit arrangement of an auxiliary reference code according to the second embodiment. [Figure 10] 10(A) and 10(B) are diagrams showing the correlation results (second correlation processing results) between SW data and auxiliary reference codes. [Figure 11] FIG. 11(A) is a diagram showing an example of a bit arrangement of a main reference code according to the third embodiment, and FIG. 11(B) is a diagram showing an example of a bit arrangement of an auxiliary reference code according to the third embodiment. [Figure 12] FIG. 12 is a diagram showing the final correlation processing result (final correlation processing data) according to the third embodiment. [Figure 13] FIG. 13(A) is a diagram showing an example of a bit arrangement of a main reference code according to the fourth embodiment, and FIG. 13(B) is a diagram showing an example of a bit arrangement of an auxiliary reference code according to the fourth embodiment. [Figure 14] FIG. 14 is a diagram showing the final correlation processing result (final correlation processing data) according to the fourth embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0010] [First embodiment] A timing detection technique according to a first embodiment of the present invention will be described with reference to the drawings. Fig. 1 is a functional block diagram of a correlation unit according to an embodiment of the present invention. Fig. 2 is a functional block diagram of an automatic identification system (AISI) according to an embodiment of the present invention.

[0011] (Configuration of Automatic Identification System) 2, the automatic identification system 10 comprises an antenna 20, a downconverter 30, a rough frequency control unit 41, a symbol timing detection unit 42, a downconverter 43, a phase control unit, a tracking processing unit 45, a signal detection unit 51, a correlation unit 52, and a decoding unit 60. Note that the components of the automatic identification system 10 other than the antenna 20 can be realized by analog circuits, digital circuits, a processing unit such as a computer, or the like.

[0012] The antenna 20 receives the automatic vessel identification signal and outputs the received signal to the downconverter 30. The downconverter 30 downconverts the received signal to a frequency that is a predetermined multiple (for example, 10 times) of the baseband signal. The downconverter 30 outputs the downconverted received signal to the coarse frequency control unit 41 and the signal detection unit 51.

[0013] 3 is a diagram showing an example of the data structure of an automatic identification signal. The automatic identification signal is composed of RU (Ramp-up) data, SW (Syncword) data, LCID (Link Config ID) data, DS (Data Symbol) data, RD (Ramp-down) data, and GD (Guard) data.

[0014] The RU data, SW data, LCID data, DS data, RD data, and GD data are arranged in this order. Each of the RU data, SW data, LCID data, DS data, RD data, and GD data has a predetermined number of bits and a predetermined bit arrangement, and is modulated by a predetermined modulation method (QPSK, 8PSK, 16QAM, etc.).

[0015] RU data is data that indicates the start of the data for the Automatic Identification Signal. SW data is data for timing detection and frequency control. LCID data is data that indicates the modulation method of the DS data. DS data is data that includes various information for Automatic Identification of Ships, such as ship identification ID. RD data is data for the Automatic Identification Signal, more specifically, data that indicates the end of the DS data. GD data is data used for error code correction, etc. SW data corresponds to the "synchronization code" of this invention.

[0016] Fig. 4 is a diagram showing an example of a bit arrangement of SW data. As shown in Fig. 4, SW data is composed of non-inverted codes and inverted codes. SW data is a code in which non-inverted codes and inverted codes are consecutive. Specifically, the non-inverted codes are, for example, a Barker code sequence with N=13. The inverted codes are codes obtained by inverting the non-inverted codes.

[0017] For example, the non-inverted code is "1,1,1,1,1,0,0,1,1,0,1,0,1,0,1", and the inverted code is "0,0,0,0,0,1,1,0,0,1,0,1,0,1,0". Therefore, the SW data is "1,1,1,1,1,0,0,1,1,0,1,0,1,0,0,0,0,0,1,1,0,0,1,0,1,0,1,0".

[0018] The frequency coarse control section 41 estimates and calculates the amount of frequency deviation from the received signal and performs coarse frequency control. For example, the processing of the frequency coarse control section 41 narrows the frequency of the reference signal from a range of ±500 Hz to a range of ±30 Hz with respect to the frequency of the received signal.

[0019] The symbol timing detector 42 detects the symbol timing of the received signal after the coarse control output from the coarse frequency controller 41. The downconverter 43 downconverts the output signal of the symbol timing detector 42 to a baseband frequency.

[0020] The phase control unit 44 performs automatic phase control on the signal down-converted to baseband (baseband signal).

[0021] The tracking processor 45 performs more accurate automatic phase control and automatic frequency control on the baseband signal output from the phase controller 44. This shifts the frequency of the reference signal from a range of ±500 Hz to a range of ±30 Hz relative to the frequency of the received signal. This makes it possible to achieve convergence to a desired symbol point with high accuracy. The tracking processor 45 outputs the signal (demodulated signal) after automatic phase control and automatic frequency control to the decoder 60.

[0022] The signal detector 51 detects RU data in the received signal.

[0023] The correlation unit 52 performs correlation processing between the received signal and the reference code using the timing of the RU data. The specific configuration and processing of the correlation unit 52 will be described later. The correlation unit 52 outputs the correlation processing result to the decoding unit 60. The correlation processing result output from the correlation unit 52 has a main lobe corresponding to the slot timing of the received signal. Therefore, the correlation processing result output from the correlation unit 52 (output correlation processing result) enables detection of the slot timing of the received signal. In other words, the correlation unit 52 corresponds to the "timing detection device" of the present invention.

[0024] The decoding unit 60 uses the demodulated signal and the timing of detection of the main lobe (peak detection timing) of the correlation processing result to decode data including various information for automatic ship identification, such as a ship identification ID, from the DS (Data Symbol) data.

[0025] (Configuration and processing of correlation unit) 1, correlation unit 52 includes correlation processor 521, correlation processor 522, differentiator 523, VCO 524, main reference code generator 525, and auxiliary reference code generator 526. Correlation processor 521 corresponds to the "first correlator" of the present invention, and correlation processor 522 corresponds to the "second correlator" of the present invention.

[0026] The VCO 524 generates a reference frequency signal for correlation processing and outputs the reference frequency signal to the main reference code generator 525 and the auxiliary reference code generator 526.

[0027] FIG. 5(A) is a diagram showing an example of a bit arrangement of a main reference code according to the first embodiment, and FIG. 5(B) is a diagram showing an example of a bit arrangement of an auxiliary reference code according to the first embodiment.

[0028] The main reference code generator 525 generates a main reference code using the reference frequency signal and outputs the generated main reference code C51 to the correlation processor 521.

[0029] As shown in FIG. 5A, the main reference code C51 is a code in which a first code section C511 and a second code section C512 are consecutive. The first code section C511 is the same code as the non-inverted code of the SW data. The second code section C512 is the same code as the inverted code of the SW data. Specifically, in this embodiment, the first code section C511 is "1,1,1,1,1,0,0,1,1,0,1,0,1,0,1", and the second code section C512 is "0,0,0,0,0,1,1,0,0,1,0,1,0,1,0". Therefore, the main reference code C51 is "1,1,1,1,1,0,0,1,1,0,1,0,1,0,0,0,0,0,1,1,0,0,1,0,1,0,1,0", which is the same code as the SW data.

[0030] The auxiliary reference code generator 526 generates an auxiliary reference code using the reference frequency signal and outputs the generated auxiliary reference code C52 to the correlation processor 522.

[0031] As shown in FIG. 5B, the auxiliary reference code C52 is a code consisting of successive first code sections C511. The first code section C511 is the same code as the non-inverted code of the SW data. Specifically, in this embodiment, the first code section C511 is "1,1,1,1,1,0,0,1,1,0,1,0,1,0,1." Therefore, the auxiliary reference code C52 is "1,1,1,1,1,0,0,1,1,0,1,0,1,1,1,1,1,1,1,0,0,1,1,0,1,0,1." In other words, the auxiliary reference code C52 is constructed using a portion of the SW data, and more specifically, is constructed using the non-inverted code of the SW data.

[0032] The correlation processor 521 executes correlation processing between the received signal and the main reference code, and outputs absolute value data of the first correlation processing result (first correlation processing data) to the differentiator 523.

[0033] The correlation processor 522 executes correlation processing between the received signal and the auxiliary reference code, and outputs absolute value data of the second correlation processing result (second correlation processing data) to the differentiator 523.

[0034] Differentiator 523 obtains the difference between the absolute value data of the first correlation processing result (first correlation processing data) and the absolute value data of the second correlation processing result (second correlation processing data), and outputs the final correlation processing result (final correlation processing data).

[0035] Figures 6(A) and 6(B) show the correlation results (first correlation processing results) between SW data and main reference code, and Figures 6(C) and 6(D) show the correlation results (second correlation processing results) between SW data and auxiliary reference code. Figure 6(B) shows the absolute value data of Figure 6(A), and Figure 6(D) shows the absolute value data of Figure 6(C).

[0036] As mentioned above, SW data contains N=26 bits, which allows for a longer code length than the Barker code sequence with N=13. This increases the ratio between the magnitude of the peak generated in the correlation result and the noise floor, enabling synchronization and frequency control to be achieved with higher precision.

[0037] However, by using Barker code sequences consecutively, the side lobe suppression effect, which is the same as when a Barker code sequence is used alone, is reduced. As a result, as shown in Figures 6(A) and 6(B), the first correlation processing result (first correlation processing data) obtained by performing correlation processing using a main reference code having the same code structure as the SW data generates a main lobe as well as a side lobe of a predetermined level.

[0038] Here, the second correlation processing result (second correlation processing data) obtained by performing correlation processing using the auxiliary reference code having the above-mentioned code configuration generates only side lobes, as shown in Figures 6(C) and 6(D).

[0039] Furthermore, by configuring the main reference code and auxiliary reference code as described above, the position (position on the time axis) of the side lobe of the correlation processing using the main reference code (first correlation processing result (first correlation processing data)) is the same as the position (position on the time axis) of the side lobe of the correlation processing using the auxiliary reference code (second correlation processing result (second correlation processing data)).

[0040] Therefore, by differentiator 523 calculating the difference between the first correlation processing result (first correlation processing data) and the second correlation processing result (second correlation processing data), the side lobes are cancelled out and suppressed, leaving only the main lobe.

[0041] 7 is a diagram showing the final correlation processing result (final correlation processing data). As shown in FIG. 7, the final correlation processing result (final correlation processing data) has almost no side lobes, and the main lobe remains.

[0042] In this way, by using the configuration and processing of this embodiment, the correlation unit 52 (timing detection device) can suppress side lobes during correlation processing. This allows the automatic identification system 10 to perform synchronization with high precision. In addition, the automatic identification system 10 can perform frequency control with high precision.

[0043] (Timing detection method) Fig. 8 is a flowchart showing an example of a timing detection method according to an embodiment of the present invention. Note that, in the specific content of each process in the flowchart shown in Fig. 8, the parts explained in the explanation of the above configuration will not be explained below.

[0044] The correlation unit 52 generates a main reference code and an auxiliary reference code (S11). The correlation unit 52 executes a first correlation process using the main reference code and a second correlation process using the auxiliary reference code (S12). The correlation unit 52 calculates the difference between the results of the first correlation process and the second correlation process (S13).

[0045] [Second embodiment] A timing detection technique according to a second embodiment of the present invention will be described with reference to the drawings. Fig. 9(A) is a diagram showing an example of a bit arrangement of a main reference code according to the second embodiment, and Fig. 9(B) is a diagram showing an example of a bit arrangement of an auxiliary reference code according to the second embodiment. Figs. 10(A) and 10(B) are diagrams showing the correlation result (second correlation processing result) between SW data and the auxiliary reference code. Fig. 10(B) is the absolute value data of Fig. 10(A).

[0046] The timing detection technique according to the second embodiment differs from the timing detection technique according to the first embodiment in the auxiliary reference code. Other details of the timing detection technique according to the second embodiment are the same as those of the timing detection technique according to the first embodiment, and therefore a description of the same parts will be omitted.

[0047] 9A, the correlation unit 52 generates a code in which a first code portion C511 and a second code portion C512 are consecutive as the main reference code C51. Therefore, the main reference code C51 is the same code as the SW data. The correlation unit 52 performs a first correlation process using the main reference code C51.

[0048] 9(B), the correlation unit 52 generates a code having successive second code portions C512 as the auxiliary reference code C52A. Specifically, in this embodiment, the auxiliary reference code C52A is "0,0,0,0,0,1,1,0,0,1,0,1,0,0,0,0,0,0,1,1,0,0,1,0,1,0,1,0".

[0049] The correlation unit 52 executes the second correlation process using the auxiliary reference code C52A.

[0050] By using such auxiliary reference code C52A, the main lobe is suppressed in the second correlation processing result (second correlation processing data), but side lobes are not suppressed and occur, as shown in Figures 10(A) and 10(B).

[0051] Therefore, by using the auxiliary reference code C52A, it is possible to suppress side lobes in the final correlation processing result (final correlation processing data).

[0052] [Third embodiment] A timing detection technique according to a third embodiment of the present invention will be described with reference to the drawings. Fig. 11(A) is a diagram showing an example of a bit arrangement of a main reference code according to the third embodiment, and Fig. 11(B) is a diagram showing an example of a bit arrangement of an auxiliary reference code according to the third embodiment. Fig. 12 is a diagram showing a final correlation processing result (final correlation processing data) according to the third embodiment.

[0053] The timing detection technique according to the third embodiment differs from the timing detection technique according to the second embodiment in the auxiliary reference code. Other details of the timing detection technique according to the third embodiment are the same as those of the timing detection technique according to the second embodiment, and therefore a description of the same parts will be omitted.

[0054] 11(A), the correlation unit 52 generates a code in which a first code portion C511 and a second code portion C512 are consecutive as the main reference code C51. Therefore, the main reference code C51 is the same code as the SW data. The correlation unit 52 performs a first correlation process using the main reference code C51.

[0055] 11(B), the correlation unit 52 generates a code in which the second code portion C512 and the third code portion C512B are consecutive as the auxiliary reference code C52B. The third code portion C512B is a code in which some bits of the second code portion C512 are different. More specifically, the third code portion C512B is a code in which the last bit of the second code portion C512 is inverted.

[0056] Specifically, in this embodiment, the third code portion C512B is "0,0,0,0,0,1,1,0,0,1,0,1,1,1". Therefore, the supplemental reference code C52B is "0,0,0,0,0,1,1,0,0,1,0,1,0,0,0,0,0,0,1,1,0,0,1,0,1,1".

[0057] The correlation unit 52 executes the second correlation process using the auxiliary reference code C52B.

[0058] By using such an auxiliary reference code C52B, the main lobe is suppressed, and the side lobes are generated with almost no suppression, as in the second embodiment.

[0059] Therefore, as shown in FIG. 12, in the final correlation processing result (final correlation processing data), the main lobe is not suppressed, but the side lobes can be suppressed.

[0060] [Fourth embodiment] A timing detection technique according to a fourth embodiment of the present invention will be described with reference to the drawings. Fig. 13(A) is a diagram showing an example of a bit arrangement of a main reference code according to the fourth embodiment, and Fig. 13(B) is a diagram showing an example of a bit arrangement of an auxiliary reference code according to the fourth embodiment. Fig. 14 is a diagram showing a final correlation processing result (final correlation processing data) according to the fourth embodiment.

[0061] The timing detection technique according to the fourth embodiment differs from the timing detection technique according to the second embodiment in the auxiliary reference code. Other details of the timing detection technique according to the fourth embodiment are the same as those of the timing detection technique according to the second embodiment, and therefore a description of the same parts will be omitted.

[0062] 13A, the correlation unit 52 generates a code in which a first code portion C511 and a second code portion C512 are consecutive as the main reference code C51. Therefore, the main reference code C51 is the same code as the SW data. The correlation unit 52 performs the first correlation process using the main reference code C51.

[0063] 13(B), the correlation unit 52 generates a code in which the second code portion C512 and the fourth code portion C512C are consecutive as the auxiliary reference code C52B. The fourth code portion C512C is a code in which some bits of the second code portion C512 are changed. More specifically, the fourth code portion C512C is a code in which the first bit of the second code portion C512 is inverted.

[0064] Specifically, in this embodiment, the fourth code portion C512C is "1,0,0,0,0,1,1,0,0,1,0,1,0,0." Therefore, the supplemental reference code C52B is "0,0,0,0,0,1,1,0,0,1,0,1,0,1,0,0,0,0,1,1,0,0,1,0,1,0,1,0."

[0065] The correlation unit 52 executes the second correlation process using the auxiliary reference code C52C.

[0066] By using such an auxiliary reference code C52C, the main lobe is suppressed, and the side lobes are generated with almost no suppression, as in the second embodiment.

[0067] Therefore, as shown in FIG. 14, in the final correlation processing result (final correlation processing data), the main lobe is not suppressed, but the side lobes can be suppressed. [Explanation of symbols]

[0068] 10: Automatic Identification System 20: Antenna 30, 43: Down converter 41: Coarse frequency control section 42: Symbol timing detector 44: Phase control section 45: Tracking processing unit 51: Signal detection unit 52: Correlation section 60: Decryption unit 521, 522: Correlation processor 523:Differentiator 524:VCO 525: Main Reference Code Generator 526: Auxiliary Reference Code Generator C51: Main Reference Code C511: First code section C512: Second code section C512B: Third code section C512C: 4th code section C52, C52A, C52B, C52C: Supplementary reference code

Claims

1. a main reference code generator that generates a main reference code that is the same as a synchronization code included in a received signal; an auxiliary reference code generator that uses a part of the same code as the synchronization code to generate an auxiliary reference code having a code structure different from that of the main reference code, and that does not produce a main lobe during correlation processing; a first correlator that performs a correlation process between the received signal and the main reference code and outputs a first correlation process result; a second correlator that correlates the received signal with the auxiliary reference code and outputs a second correlation result; a difference calculator that calculates a difference between the first correlation processing result and the second correlation processing result; A timing detection device comprising:

2. 2. The timing detection device according to claim 1, the synchronization code is composed of a sequence of a non-inverted code made of a predetermined spreading code and an inverted code of the spreading code, The auxiliary reference code generator The auxiliary reference code is generated using a sequence of the non-inverted codes. 、 Timing detection device.

3. 3. The timing detection device according to claim 2, the auxiliary reference code is a code in which the non-inverted code is consecutive; Timing detection device.

4. 2. The timing detection device according to claim 1, the synchronization code is composed of a sequence of a non-inverted code made of a predetermined spreading code and an inverted code of the spreading code, The auxiliary reference code generator generating the auxiliary reference code using successive codes of the inverted code; Timing detection device.

5. 5. The timing detection device according to claim 4, the auxiliary reference code is a code in which the inverted code is consecutive; Timing detection device.

6. 6. The timing detection device according to claim 1, The synchronization code is a Barker code. Timing detection device.

7. generating a main reference code consisting of the same code as the synchronization code contained in the received signal; generating an auxiliary reference code having a code structure different from that of the main reference code using a part of the same code as the synchronization code, and which suppresses a main lobe during correlation processing; Correlate the received signal with the main reference code and output a first correlation processing result; Correlate the received signal with the auxiliary reference code and output a second correlation result; calculating a difference between the first correlation processing result and the second correlation processing result; Timing detection method.

8. 8. The timing detection method according to claim 7, the synchronization code is composed of a sequence of a non-inverted code made of a predetermined spreading code and an inverted code of the spreading code, The auxiliary reference code is generated using a sequence of the non-inverted codes. 、 Timing detection method.

9. 9. The timing detection method according to claim 8, the auxiliary reference code is a code in which the non-inverted code is consecutive; Timing detection method.

10. 8. The timing detection method according to claim 7, the synchronization code is composed of a sequence of a non-inverted code made of a predetermined spreading code and an inverted code of the spreading code, generating the auxiliary reference code using successive codes of the inverted code; Timing detection method.

11. 11. The timing detection method according to claim 10, the auxiliary reference code is a code in which the inverted code is consecutive; Timing detection method.

12. 12. The timing detection method according to claim 7, further comprising: The synchronization code is a Barker code. Timing detection method.

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