Signal processing device and signal processing method

Abstract

To provide a signal processing device capable of properly removing noises having temporal periodicity from received signals.SOLUTION: The signal processing device includes a noise estimation unit. The noise estimation unit receives input signals that are time domain signals including broadcast signals, which are signals derived from broadcast waves and noise signals that have peaks at regular time intervals. The signal-processing device detects a non-broadcasting period that exists at regular time intervals and does not include broadcasting signals from the received signal, and extracts at least part of the received signal in the non-broadcast period as a first noise pattern signal.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a signal processing device and a signal processing method. [Background technology]

[0002] Generally, a noise canceller is composed of a noise extraction unit and a noise suppression unit that subtracts the extracted noise from the received signal. The conventional technology disclosed in Patent Document 1 is based on the premise that the bandwidth of the broadcast wave is narrower than the bandwidth of the A / D converter, as in an AM radio receiver, for example. In other words, the conventional technology achieves noise suppression by taking advantage of the periodicity of the noise and adding a frequency-shifted received signal in antiphase to the original received signal. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-126360 Summary of the Invention [Problem to be solved by the invention]

[0004] However, signals that use multiple carrier frequencies, such as DAB broadcast waves, have a wide bandwidth and occupy most of the bandwidth of the A / D converter, so the method using frequency shift mentioned above can cause interference between the broadcast waves and may not be able to achieve adequate noise suppression.

[0005] An object of the present disclosure is to provide a technology for appropriately removing noise having time periodicity from a received signal. [Means for solving the problem]

[0006] A signal processing device according to one embodiment of the present disclosure is a signal processing device including a noise estimation unit, which receives as input a received signal, which is a time-domain signal including a broadcast signal derived from a broadcast wave and a noise signal having peaks at regular time intervals, detects non-broadcast intervals from the received signal, which are time intervals that do not include the broadcast signal and exist at regular time intervals, and extracts at least a portion of the received signal in the non-broadcast intervals as a first noise pattern signal.

[0007] A signal processing method according to one embodiment of the present disclosure receives as input a received signal, which is a time-domain signal including a broadcast signal derived from a broadcast wave and a noise signal having peaks at regular time intervals; detects non-broadcast intervals from the received signal, which are time intervals that do not include the broadcast signal and exist at regular time intervals; and extracts at least a portion of the received signal in the non-broadcast intervals as a first noise pattern signal.

[0008] These comprehensive or specific aspects may be realized as a system, an apparatus, a method, an integrated circuit, a computer program, or a recording medium, or may be realized as any combination of a system, an apparatus, a method, an integrated circuit, a computer program, and a recording medium. [Effects of the Invention]

[0009] According to the present disclosure, it is possible to appropriately remove noise having temporal periodicity from a received signal. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a diagram showing a first configuration example of a signal processing device according to an embodiment of the present invention; [Figure 2] FIG. 1 is a diagram for explaining processing by a signal processing device having a first exemplary configuration according to the present embodiment. [Figure 3] FIG. 10 is a diagram showing a second configuration example of a signal processing device according to the present embodiment. [Figure 4] FIG. 10 is a diagram for explaining the processing of a signal processing device having a second exemplary configuration according to the present embodiment. [Figure 5] FIG. 10 is a diagram showing a third configuration example of a signal processing device according to the present embodiment. [Figure 6A] FIG. 10 is a diagram for explaining the processing of a signal processing device having a third exemplary configuration according to the present embodiment. [Figure 6B] FIG. 10 is a diagram for explaining the processing of a signal processing device having a third exemplary configuration according to the present embodiment. [Figure 7] FIG. 10 is a diagram showing a fourth configuration example of a signal processing device according to the present embodiment. [Figure 8] FIG. 10 is a diagram for explaining the processing of a signal processing device having a fourth exemplary configuration according to the present embodiment. [Figure 9] FIG. 1 is a block diagram illustrating an example of a hardware configuration of a signal processing device according to the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, embodiments of the present disclosure will be described in detail with appropriate reference to the drawings. However, more detailed description than necessary may be omitted. For example, detailed descriptions of well-known matters and redundant descriptions of substantially identical configurations may be omitted. This is to avoid unnecessary redundancy in the following description and to facilitate understanding by those skilled in the art. Note that the accompanying drawings and the following description are provided to enable those skilled in the art to fully understand the present disclosure, and are not intended to limit the subject matter described in the claims.

[0012] (Embodiment 1) <First configuration example> Fig. 1 is a diagram showing a first configuration example of a signal processing device 10 according to the present embodiment. Fig. 2 is a diagram for explaining processing of the signal processing device 10 having the first configuration example according to the present embodiment.

[0013] The signal processing device 10 is used for signal processing of received broadcast waves. The signal processing device 10 is mounted on a vehicle such as an EV (Electric Vehicle) or a PHEV (Plug-in Hybrid Electrical Vehicle). The signal processing device 10 according to the first configuration example includes an antenna 11, an AD conversion unit 12, a noise estimation unit 13, a deviation calculation unit 14, a clipping unit 15, a phase adjustment unit 16, and a noise removal unit 17.

[0014] The antenna 11 receives broadcast waves. The broadcast waves may be digital radio broadcasts in the DAB (Digital Audio Broadcast) format. DAB broadcast waves employ the OFDM (Orthogonal Frequency Division Multiplexing) modulation method. DAB broadcast waves also have NULL symbols that do not contain any broadcast waves at regular time intervals. The NULL symbols are time intervals that do not contain any broadcast waves, and may be interpreted as non-broadcast intervals.

[0015] The AD (Analog-Digital) converter 12 converts analog signals of broadcast waves received by the antenna 11 into digital signals and outputs the digital signals. The signals output by the AD converter 12 are referred to as received signals. The received signals may include broadcast signals, which are signals derived from broadcast waves, and noise signals, which are signals derived from noise. Vehicles such as EVs may be equipped with devices that emit noise with peaks at regular time intervals. Examples of such devices include inverters and DC / DC converters. In other words, the received signals may include noise signals with peaks at regular time intervals. The signal processing device 10 outputs a signal obtained by removing such noise signals with peaks at regular time intervals from the received signal. A radio device (not shown) can output low-noise audio from a speaker by decoding the signal from which the noise signals have been removed by the signal processing device 10.

[0016] In this embodiment, a signal of 2048 samples, which corresponds to 1 msec of the received signal, is described as the first signal. However, the first signal may have any number of samples as long as it is within a predetermined time interval.

[0017] The noise estimation unit 13 estimates a noise signal included in the received signal output from the AD conversion unit 12. The noise estimation unit 13 includes a NULL symbol detection unit 21 and a noise pattern extraction unit 22.

[0018] In the DAB system, NULL symbols exist at regular time intervals in a broadcast signal. The regular time intervals may be one frame period. The NULL symbol detector 21 detects the NULL symbols existing in the received signal every one frame period.

[0019] The noise pattern extraction unit 22 extracts at least a part of the signal in the NULL symbol detected by the NULL symbol detection unit 21 as a first noise pattern signal. For example, the noise pattern extraction unit 22 extracts 2548 (=2048+500) samples in the center of the 2656 samples included in the NULL symbol as the first noise pattern signal. The noise estimation unit 13 outputs the extracted first noise pattern signal. Since the NULL symbol does not include a broadcast signal, the signal extracted from the NULL symbol is dominated by a noise signal. In other words, the first noise pattern signal is an estimate of the actual noise signal with high accuracy.

[0020] That is, the noise estimation unit 13 receives as input a received signal, which is a time-domain signal that includes a broadcast signal, which is a signal derived from a broadcast wave, and a noise signal that has peaks at regular time intervals, and detects non-broadcast intervals from the received signal, which are time intervals that do not include a broadcast signal and exist at regular time intervals, and extracts at least a portion of the received signal in the non-broadcast intervals as a first noise pattern signal.

[0021] The deviation calculation unit 14 calculates the amount of deviation in the time domain between the peaks of the first signal, which is a received signal in a predetermined section of the received signal output from the AD conversion unit 12, and the first noise pattern signal output from the noise estimation unit 13. Then, based on the calculated amount of deviation, the deviation calculation unit 14 determines a start position for extracting a predetermined section from the first noise pattern signal. The predetermined section may be 2048 samples, the same as the first signal. For example, as shown in FIG. 2(a), the deviation calculation unit 14 calculates the cross-correlation while shifting the first signal relative to the first noise pattern signal in the time direction, and determines the position of the first signal relative to the first noise pattern signal at which the correlation value is highest as the start position. The deviation calculation unit 14 outputs the determined start position.

[0022] Furthermore, the deviation calculation unit 14 calculates the phase difference between the first noise pattern signal and the first signal at the position where the correlation value is highest. Based on the calculated phase difference, the deviation calculation unit 14 calculates a phase adjustment amount for synchronizing the phases of the first noise pattern signal and the first signal at the position where the correlation value is highest. The deviation calculation unit 14 outputs the calculated phase adjustment amount.

[0023] That is, the deviation calculation unit 14 determines the start position for cutting out the first noise pattern signal based on the cross-correlation between the first signal, which is a received signal in a predetermined section, and the first noise pattern signal, and calculates the amount of phase adjustment based on the phase deviation between the first signal and the first noise pattern signal.

[0024] The clipping unit 15 generates a second noise pattern signal by clipping a predetermined section of the first noise pattern signal output from the noise estimation unit 13, starting from the start position output from the deviation calculation unit 14. The predetermined section may be 2048 samples, the same as the first signal. That is, the clipping unit 15 generates a second noise pattern signal by clipping 2048 samples of the first noise pattern signal, starting from the start position. The clipping unit 15 also outputs the second noise pattern signal. This allows the clipping unit 15 to generate and output a second noise pattern signal whose peak portions are aligned with those of the first signal in the time domain.

[0025] The phase adjustment unit 16 adjusts the phase of the second noise pattern signal output from the clipping unit 15 based on the phase adjustment amount output from the deviation calculation unit 14, thereby generating a third noise pattern signal as shown in Fig. 2(b). This allows the phase adjustment unit 16 to generate a third noise pattern signal whose peak portion and phase are aligned with those of the first signal. The phase adjustment unit 16 outputs the generated third pattern signal.

[0026] As shown in FIG. 2(c), the noise elimination unit 17 subtracts the third noise pattern signal output from the phase adjustment unit 16 from the first signal output from the AD conversion unit 12 to generate a second signal as shown in FIG. 2(d). The noise elimination unit 17 also outputs the second signal. This allows the noise elimination unit 17 to generate and output a second signal in which the magnitude of noise peaks is suppressed compared to the first signal. Therefore, a radio device (not shown) can output sound with less noise from a speaker by decoding the second signal output from the noise elimination unit 17.

[0027] <Second configuration example> Fig. 3 is a diagram showing a second configuration example of the signal processing device 10 according to the present embodiment. Fig. 4 is a diagram for explaining the processing of the signal processing device 10 having the second configuration example according to the present embodiment. In the explanation of the second configuration example, differences from the first configuration example will be explained, and explanation of parts common to the first configuration example may be omitted.

[0028] The signal processing device 10 includes an antenna 11, an AD conversion unit 12, a noise estimation unit 13, a deviation calculation unit 14, a clipping unit 15, a phase adjustment unit 16, a noise removal unit 17, and a synchronous synthesis unit 30.

[0029] The noise estimation unit 13 generates a first noise pattern signal from each of M different NULL symbols. M is an integer equal to or greater than 2. That is, the noise estimation unit 13 generates M first noise pattern signals. The noise estimation unit 13 outputs the generated M first noise pattern signals.

[0030] The deviation calculation unit 14 determines the start position of each of the M first noise pattern signals output from the noise estimation unit 13. At this time, as shown in FIG. 4(a), the deviation calculation unit 14 stores the correlation value calculated to determine the start position in association with the first noise pattern signal. The correlation value is used in the synchronous synthesis unit 30, which will be described later. The deviation calculation unit 14 outputs the M start positions.

[0031] The deviation calculation unit 14 also calculates the phase adjustment amount for each of the M first noise pattern signals, and outputs the M phase adjustment amounts.

[0032] The clipping unit 15 generates M second noise pattern signals by clipping a predetermined section of each of the M first noise pattern signals output from the noise estimation unit 13 from a corresponding start position among the M start positions output from the deviation calculation unit 14. That is, the clipping unit 15 generates M second noise pattern signals by clipping each of the M first noise patterns from a corresponding start position. The clipping unit 15 outputs the generated M second noise pattern signals.

[0033] The phase adjustment unit 16 generates M third noise pattern signals by adjusting the phases of the M second noise pattern signals output from the extraction unit 15 using the phase adjustment amounts corresponding to the M phase adjustment amounts output from the deviation calculation unit 14. That is, the phase adjustment unit 16 generates M third noise pattern signals by performing phase adjustment on each of the M second noise pattern signals using the corresponding phase adjustment amount. The phase adjustment unit 16 outputs the generated M third noise pattern signals.

[0034] The synchronous synthesis unit 30 selects N third noise pattern signals from the M third noise pattern signals output from the phase adjustment unit 16 in descending order of correlation value, as shown in FIG. 4(b). N is a positive integer smaller than M. The synchronous synthesis unit 30 performs synchronous synthesis processing on the selected N third noise pattern signals to generate a synthesized noise pattern signal, as shown in FIG. 4(c). The synchronous synthesis processing synchronizes the timing and phase of the noise peaks of multiple third noise pattern signals and synthesizes them. The synthesis processing may involve adding multiple third noise pattern signals. The synchronous synthesis processing generates a synthesized noise pattern signal in which noise peaks are emphasized and non-peak noise portions are suppressed by cancellation. Therefore, the synthesized noise pattern signal has an improved carrier-to-noise ratio (CN ratio) between periodic noise and the noise floor, compared to a single third noise pattern signal. The synchronous synthesis unit 30 outputs the generated synthesized noise pattern signal.

[0035] The synchronous synthesis unit 30 may perform the synchronous synthesis process using either of the following methods (A1) and (A2). (A1) The synchronous synthesis unit 30 generates a synthesized noise pattern signal by averaging N third noise pattern signals in descending order of correlation value. (A2) The synchronous synthesis unit 30 weights the third noise pattern signals so that the newer the third noise pattern signals in the time series, the greater their influence, and then averages N third noise pattern signals in descending order of correlation value to generate a synthesized noise pattern signal.

[0036] As shown in FIG. 4(d), the noise elimination unit 17 subtracts the synthesized noise pattern signal output from the synchronous synthesis unit 30 from the first signal output from the AD conversion unit 12 to generate a second signal as shown in FIG. 4(e). The noise elimination unit 17 then outputs the second signal. This allows the noise elimination unit 17 to generate and output a second signal in which the magnitude of noise peaks is suppressed compared to the first signal. Typically, the CN ratio of the synthesized noise pattern signal is higher than the CN ratio of one third noise pattern signal. Therefore, the noise elimination unit 17 can generate and output a second signal in which the magnitude of noise peaks is further suppressed compared to the first configuration example. This allows a radio device (not shown) to decode the second signal output from the noise elimination unit 17 and output audio with less noise from its speaker.

[0037] <Third configuration example> Fig. 5 is a diagram showing a third configuration example of the signal processing device 10 according to the present embodiment. Figs. 6A and 6B are diagrams for explaining the processing of the signal processing device 10 having the third configuration example according to the present embodiment. In the explanation of the third configuration example, differences from the second configuration example will be explained, and explanations of parts common to the second configuration example may be omitted.

[0038] The signal processing device 10 includes an antenna 11, an AD conversion unit 12, a noise estimation unit 13, a synchronous synthesis unit 30, a deviation calculation unit 14, a clipping unit 15, a phase adjustment unit 16, and a noise removal unit 17.

[0039] As shown in FIG. 6A(a), the noise pattern extraction unit 22 included in the noise estimation unit 13 extracts 2548 (=2048+250+250) samples in the center of the 2656 samples included in the NULL symbol as a first noise pattern signal. As shown in FIG. 6A(a), the noise estimation unit 13 generates a first noise pattern signal from each of M mutually different NULL symbols. M is an integer equal to or greater than 2. That is, the noise estimation unit 13 generates M first noise pattern signals. The noise estimation unit 13 outputs the generated M first noise pattern signals.

[0040] The synchronous synthesis unit 30 performs synchronous synthesis processing on the M first noise pattern signals output from the noise estimation unit 13. For example, the synchronous synthesis unit 30 performs the following steps S11 to S16. (Step S11) As shown in FIG. 6A(b), the synchronous synthesis unit 30 selects the first first noise pattern signal from among the M first noise pattern signals, and removes the latter 250 samples. (Step S12) As shown in FIG. 6A(b), the synchronous synthesis unit 30 calculates a correlation value by shifting the first first noise pattern signal, from which 250 samples have been removed, relative to the second first noise pattern signal by a shift width of 250 samples, and detects the section where the correlation value is maximum. (Step S13) The synchronous synthesis unit 30 extracts the section in which the correlation value is maximum from the second first noise pattern signal. (Step S14) The synchronous synthesis unit 30 performs the same processing as steps S12 and S13 described above on the third to Mth first noise pattern signals, and extracts the section in which the correlation value is maximum. (Step S15) The synchronous synthesis unit 30 adjusts the phases of the second to Mth first noise pattern signals extracted in steps S12 to S14 so that they are aligned with the phase of the first first noise pattern signal from which the latter 250 samples have been removed in step S11. (Step S16) The synchronous synthesis unit 30 synthesizes the 1st to Mth first noise pattern signals whose phases have been adjusted in step S15 to generate a synthesized noise pattern signal of 2298 (=2048+250) samples, as shown in FIG. 6A(c). 250 samples of the first noise pattern signal are surplus samples required for calculating the cross-correlation between the first noise patterns. In the example shown in FIG. 6A, the shift width when calculating the cross-correlation is 250 samples, so the surplus samples are also 250 samples. The surplus samples are removed from the first noise pattern signal in the process of extracting the section where the correlation value is maximized. Therefore, the number of samples of the synthesized noise pattern signal is 250 samples less than the number of samples of the first noise pattern signal.

[0041] The above processing generates a composite noise pattern signal in which noise peaks are emphasized and non-peak noise is suppressed by cancellation, resulting in an improved C / N ratio between the periodic noise and the noise floor in the composite noise pattern signal compared to a single first noise pattern signal.

[0042] 6B(d), the deviation calculation unit 14 calculates a correlation value while shifting the first signal of 2048 samples output from the AD conversion unit 12 with respect to the combined noise pattern signal of 2298 (=2048+250) samples output from the synchronous synthesis unit 30 by a shift width of 250 samples. The deviation calculation unit 14 calculates the amount of shift that maximizes the correlation value, and determines the start position for cutting out a predetermined section from the combined noise pattern signal based on the calculated amount of shift. The deviation calculation unit 14 outputs the determined start position.

[0043] The deviation calculation unit 14 also calculates the phase difference between the composite noise pattern signal and the first signal, and calculates the amount of phase adjustment based on the calculated phase difference. The deviation calculation unit 14 outputs the calculated amount of phase adjustment.

[0044] The clipping unit 15 generates a second noise pattern signal by clipping a predetermined section of the combined noise pattern signal output from the synchronous combining unit 30, starting from the start position output from the deviation calculating unit 14. The clipping unit 15 also outputs the second noise pattern signal.

[0045] The phase adjustment unit 16 adjusts the phase of the second noise pattern signal output from the extraction unit 15 based on the phase adjustment amount output from the shift calculation unit 14, thereby generating a third noise pattern signal as shown in FIG. 6B(e). The phase adjustment unit 16 also outputs the third pattern signal. 250 samples of the composite noise pattern signal are surplus samples required to calculate the cross-correlation between the first signal and the composite noise pattern signal. In the example shown in FIG. 6B, the shift width when calculating the cross-correlation is 250 samples, so the surplus samples are also 250 samples. The surplus samples are removed from the composite noise pattern signal during the process of extracting the section where the correlation value is maximized. Therefore, the number of samples of the third noise pattern signal is 250 samples less than the number of samples of the composite noise pattern signal.

[0046] As shown in FIG. 6B(f), the noise elimination unit 17 subtracts the third noise pattern signal output from the phase adjustment unit 16 from the first signal output from the AD conversion unit 12 to generate a second signal as shown in FIG. 6B(g). The noise elimination unit 17 also outputs the second signal. Since the third noise pattern signal has been subtracted from the second signal, the magnitude of the noise peaks in the second signal is suppressed compared to the first signal. This allows a radio device (not shown) to decode the second signal output from the signal processing device 10 and output sound with less noise from the speaker.

[0047] Since the number of samples of the NULL symbol is "2656," the number of samples of the first noise pattern signal shown in FIG. 6A(a) is limited to "2656" or less. Therefore, in the above, the number of samples of the first noise pattern signal is set to "2048 + 250 + 250." For example, the number of samples of the first noise pattern signal may be set to "1024 + 500 + 500," and the number of samples of the first signal may be set to "1024." In other words, the surplus for calculating the cross-correlation may be set to 500 samples.

[0048] Furthermore, the deviation calculation unit 14 may store the synthesized noise pattern signal output from the synchronization synthesis unit 30 in a predetermined memory, and repeatedly use the stored synthesized noise pattern signal for the first signal sequentially output from the AD conversion unit 12. This reduces the processing load on the signal processing device 10 compared to when a synthesized noise pattern signal is generated every time.

[0049] Alternatively, an expiration date may be set for the stored synthetic noise pattern signal, and when the expiration date expires, the synchronous synthesis unit 30 may generate a new synthetic noise pattern signal and store it in memory. This allows the signal processing device 10 to update the synthetic noise pattern signal to match the currently received signal while reducing the processing load.

[0050] <Fourth configuration example> Fig. 7 is a diagram showing a fourth configuration example of the signal processing device 10 according to the present embodiment. Fig. 8 is a diagram for explaining the processing of the signal processing device 10 having the fourth configuration example according to the present embodiment. In the explanation of the fourth configuration example, differences from the first configuration example will be explained, and explanation of parts common to the first configuration example may be omitted. In the fourth configuration example, a signal processing device 10 that can be applied to broadcast waves that do not include NULL symbols will be explained.

[0051] The signal processing device 10 includes an antenna 11 , an AD conversion unit 12 , a noise estimation unit 13 , a deviation calculation unit 14 , a clipping unit 15 , a phase adjustment unit 16 , and a noise removal unit 17 .

[0052] The noise estimation unit 13 includes a synchronous synthesis unit 30 and a noise pattern extraction unit 22 .

[0053] As shown in Fig. 8(a), the synchronous combining unit 30 performs synchronous combining processing on M mutually different one-symbol signals included in the received signal output from the AD conversion unit 12, thereby generating a combined symbol signal as shown in Fig. 8(b). For example, the synchronous combining unit 30 acquires M one-symbol signals of 3156 (=2656+500) samples. The synchronous combining unit 30 performs processing similar to steps S11 to S16 described in the third configuration example above on the M one-symbol signals, using a shift width of 500 samples, thereby generating a combined symbol signal of 2656 samples as shown in Fig. 8(b). In other words, the number of samples of the combined symbol signal is less than the number of samples of the one-symbol signal by 500 samples used as the shift width.

[0054] The time waveform of a broadcast wave using the OFDM modulation method is highly random. In other words, the broadcast wave has low autocorrelation. Therefore, in a combined symbol signal obtained by synchronously combining M one-symbol signals, the level of the broadcast signal portion is reduced and the level of the periodic noise signal portion is emphasized, as shown in Figure 8(b).

[0055] The noise pattern extraction unit 22 extracts a first noise pattern signal from the combined symbol signal. For example, as shown in FIG. 8(c), the noise pattern extraction unit 22 extracts 2548 (=2048+500) samples in the center of the 2656 samples included in the combined symbol signal as the first noise pattern signal.

[0056] In this way, even if the broadcast wave does not include a NULL symbol, the noise estimation unit 13 can output the first noise pattern signal by generating a combined symbol signal through synchronous combining processing.

[0057] The deviation calculation unit 14 and the clipping unit 15 may perform the same processing as in the first configuration example, using the first noise pattern signal output from the noise estimation unit 13. The phase adjustment unit 16 and the noise removal unit 17 may also perform the same processing as in the first configuration example.

[0058] This allows the signal processing device 10 to output a second signal with a suppressed noise peak, and therefore a radio device (not shown) can decode the second signal output from the signal processing device 10 and output sound with less noise from the speaker.

[0059] Unlike the first to third configuration examples, the fourth configuration example does not use a NULL symbol. Therefore, in the fourth configuration example, the synchronous synthesis unit 30 may extract any sample interval from the received signal. For example, one symbol of the signal shown in FIG. 8(a) may be 2656 samples or more.

[0060] <Modification> The signal processing device 10 according to the first to fourth configuration examples described above may perform the following processing. That is, the signal processing device 10 compares the signal level of the first signal with the signal level of the second signal and determines whether the power of the second signal is greater than the power of the first signal. If the power of the second signal is greater than the power of the first signal, the signal processing device 10 stops the operation of the noise reduction unit 17. That is, the signal processing device 10 stops the noise canceller. If the noise reduction unit 17 is not operating properly, the second signal may have increased noise compared to the first signal. If the noise in the second signal is increased, the power of the second signal will be greater than the power of the first signal. Therefore, by stopping the operation of the noise reduction unit 17 according to the result of comparing the power of the first signal with the power of the second signal, the signal processing device 10 can prevent the second signal with increased noise from being output to the broadcast signal decoder.

[0061] (Hardware configuration) FIG. 9 is a block diagram showing an example of a hardware configuration of the signal processing device 10 according to the present disclosure.

[0062] As shown in FIG. 9, the signal processing device 10 may include a processor 1001, a memory 1002, a signal input I / F (Interface) 1003, a signal output I / F 1004, and a communication device 1005.

[0063] The processor 1001 may execute a computer program stored in the memory 1002 to realize the processing of the AD conversion unit 12, the noise estimation unit 13, the deviation calculation unit 14, the clipping unit 15, the phase adjustment unit 16, the noise removal unit 17, the NULL symbol detection unit 21, the noise pattern extraction unit 22, and the synchronization synthesis unit 30 included in the above-described signal processing device 10. The processor 1001 may be interpreted as other terms such as a control unit, a control device, a control circuit, a controller, a CPU (Central Processing Unit), an MPU (Micro Processing Unit), an LSI (Large Scale Integration), an ASIC (Application Specific Integrated Circuit), a PLD (Programmable Logic Device), or an FPGA (Field-Programmable Gate Array).

[0064] The memory 1002 stores computer programs and data used by the signal processing device 10. The memory 1002 may include a read-only memory (ROM) and a random access memory (RAM). The memory 1002 may also include a volatile memory and a non-volatile memory.

[0065] The signal input I / F 1003 may be connected to the antenna 11. The signal input I / F 1003 may output a received signal input from the antenna 11 to the processor 1001.

[0066] The signal output I / F 1004 may be connected to a radio device (not shown), and may output the output signal input from the processor 1001 to the radio device.

[0067] The communication device 1005 may be connected to a communication network within the vehicle. Examples of the communication network include a controller area network (CAN), a LIN, and a FlexRay. The processor 1001 may transmit and receive information to and from each device provided in the vehicle via the communication device 1005 and the communication network.

[0068] At least some of the AD conversion unit 12, noise estimation unit 13, deviation calculation unit 14, clipping unit 15, phase adjustment unit 16, noise removal unit 17, NULL symbol detection unit 21, noise pattern extraction unit 22, and synchronization synthesis unit 30 included in the signal processing device 100 may be realized as an LSI, which is an integrated circuit. At least some of the AD conversion unit 12, noise estimation unit 13, deviation calculation unit 14, clipping unit 15, phase adjustment unit 16, noise removal unit 17, NULL symbol detection unit 21, noise pattern extraction unit 22, and synchronization synthesis unit 30 may be individually implemented on a single chip, or some or all of them may be integrated on a single chip. Although the term LSI is used here, it may also be referred to as an IC, system LSI, super LSI, or ultra LSI depending on the degree of integration. Furthermore, if an integrated circuit technology that can replace LSI emerges due to advances in semiconductor technology or a different derived technology, that technology may naturally be used to integrate blocks.

[0069] Summary of the Disclosure The contents of this disclosure can be expressed as follows:

[0070] <Item 1> A signal processing device (10) of the present disclosure includes a noise estimation unit (13). The noise estimation unit (13) receives as input a received signal, which is a time-domain signal including a broadcast signal derived from a broadcast wave and a noise signal having peaks at regular time intervals, detects non-broadcast intervals (e.g., NULL symbols) that exist at regular time intervals from the received signal and are time intervals that do not include a broadcast signal, and extracts at least a portion of the received signal in the non-broadcast intervals as a first noise pattern signal. Since the non-broadcast interval does not contain a broadcast signal, the first noise pattern signal extracted from the non-broadcast interval estimates the actual noise signal with high accuracy. Therefore, the signal processing device (10) can appropriately suppress the noise contained in the received signal by using the first noise pattern signal.

[0071] <Item 2> The signal processing device (10) described in item 1 further includes a deviation calculation unit (14). The deviation calculation unit (14) determines a start position for cutting out the first noise pattern signal based on a cross-correlation between a first signal, which is a received signal in a predetermined section, and the first noise pattern signal, and calculates a phase adjustment amount based on a phase deviation between the first signal and the first noise pattern signal. This allows the deviation calculation section (14) to calculate the peak deviation and phase deviation between the first signal and the first noise pattern signal.

[0072] <Item 3> The signal processing device (10) described in item 2 further includes a cutout unit (15). The cutout unit (15) cuts out a predetermined section of the first noise pattern signal from a start position, thereby generating a second noise pattern signal. This allows the cutout section (15) to generate a second pattern signal whose peak portions are aligned with those of the first signal in the time domain.

[0073] <Item 4> The signal processing device (10) described in item 3 further includes a phase adjustment unit (16). The phase adjustment unit (16) adjusts the phase of the second noise pattern signal based on the phase adjustment amount, thereby generating a third noise pattern signal. This allows the phase adjustment unit (16) to generate a third noise pattern signal that is aligned in peak and phase with the first signal.

[0074] <Item 5> The signal processing device (10) described in item 4 further includes a synchronous synthesis unit (30). The synchronous synthesis unit (30) generates a synthesized noise pattern signal by synchronizing and synthesizing a plurality of third noise pattern signals. This allows the synchronous synthesis unit (30) to generate a synthesized noise pattern signal in which the peak portions of the noise are emphasized and the portions other than the peaks of the noise are suppressed by cancellation.

[0075] <Item 6> The signal processing device (10) described in item 4 further includes a noise removal section (17). The noise removal section (17) generates a second signal by subtracting a third noise pattern signal from the first signal. This allows the noise removal section (17) to generate a second signal in which noise peaks are suppressed.

[0076] <Item 7> The signal processing device (10) described in item 5 further includes a noise removal section (17). The noise removal section (17) generates a second signal by subtracting the synthetic noise pattern signal from the first signal. In the synthesized noise pattern signal, noise peaks are emphasized and non-noise peaks are suppressed, thereby enabling the noise removal unit (17) to generate a second signal in which noise peaks are further suppressed.

[0077] <Item 8> The signal processing device (10) described in item 1 further includes a synchronous synthesis unit (30), a deviation calculation unit (14), a clipping unit (15), a phase adjustment unit (16), and a noise removal unit (17). A synchronous synthesis unit (30) synthesizes the plurality of first noise pattern signals in synchronization with each other to generate a synthesized noise pattern signal. The deviation calculation unit (14) determines a start position for cutting out the composite noise pattern signal based on the cross-correlation between a first signal, which is a predetermined section of the received signal, and the composite noise pattern signal, and calculates a phase adjustment amount based on the phase deviation between the first signal and the composite noise pattern signal. The cutout section (15) cuts out a predetermined section of the synthesized noise pattern signal from the start position to generate a second noise pattern signal. A phase adjuster (16) adjusts the phase of the second noise pattern signal based on the phase adjustment amount, thereby generating a third noise pattern signal. A noise removal section (17) generates a second signal by subtracting the third noise pattern signal from the first signal. This allows the noise removal section (17) to generate a second signal in which noise peaks are suppressed.

[0078] <Item 9> The signal processing method of the present disclosure includes the following processing: A received signal, which is a time-domain signal including a broadcast signal derived from a broadcast wave and a noise signal having peaks at regular time intervals, is input, non-broadcast intervals, which are time intervals that do not include a broadcast signal and exist at regular time intervals, are detected from the received signal, and at least a portion of the received signal in the non-broadcast intervals is extracted as a first noise pattern signal. Since the non-broadcast interval does not contain a broadcast signal, the first noise pattern signal extracted from the non-broadcast interval is a highly accurate estimate of the actual noise signal. Therefore, according to the signal processing method, by using the first noise pattern signal, it is possible to appropriately suppress the noise contained in the received signal.

[0079] Although the embodiments have been described above with reference to the accompanying drawings, the present disclosure is not limited to such examples. It is clear that a person skilled in the art can conceive of various modifications, alterations, substitutions, additions, deletions, and equivalents within the scope of the claims, and it is understood that these also fall within the technical scope of the present disclosure. Furthermore, the components in the above-described embodiments may be combined in any manner without departing from the spirit of the invention. [Industrial Applicability]

[0080] The technology of the present disclosure is useful for a signal processing device or a signal processing method for removing noise from a signal. [Explanation of symbols]

[0081] 10. Signal Processing Device 11 Antenna 12 AD conversion section 13 Noise estimation section 14 Deviation calculation unit 15 Cutout section 16 Phase adjustment section 17 Noise reduction section 21 NULL symbol detection unit 22 Noise pattern extraction unit 30 Synchronous synthesis section

Claims

1. A signal processing device including a noise estimation unit, the noise estimation unit A received signal is input, which is a time domain signal including a broadcast signal derived from a broadcast wave and a noise signal having peaks at regular time intervals; detecting non-broadcast periods, which are time periods that do not include the broadcast signal and exist at regular time intervals, from the received signal; extracting at least a portion of the received signal in the non-broadcast period as a first noise pattern signal; a deviation calculation unit that determines a start position for extracting the first noise pattern signal based on a cross-correlation between a first signal, which is the received signal in a predetermined section, and the first noise pattern signal, and calculates a phase adjustment amount based on a phase deviation between the first signal and the first noise pattern signal, Signal processing device.

2. a cutout unit that cuts out a predetermined section of the first noise pattern signal from the start position to generate a second noise pattern signal, The signal processing device according to claim 1 .

3. a phase adjustment unit that adjusts the phase of the second noise pattern signal based on the phase adjustment amount to generate a third noise pattern signal. The signal processing device according to claim 2 .

4. a synchronous synthesis unit that generates a synthesized noise pattern signal by synchronizing and synthesizing the plurality of third noise pattern signals, The signal processing device according to claim 3 .

5. a noise removal unit that generates a second signal by subtracting the third noise pattern signal from the first signal. The signal processing device according to claim 3 .

6. a noise removal unit that generates a second signal by subtracting the synthetic noise pattern signal from the first signal. The signal processing device according to claim 4 .

7. A signal processing device comprising a noise estimation unit, wherein the noise estimation unit: A received signal is input, which is a time domain signal including a broadcast signal derived from a broadcast wave and a noise signal having peaks at regular time intervals; detecting non-broadcast periods, which are time periods that do not include the broadcast signal and exist at regular time intervals, from the received signal; extracting at least a portion of the received signal in the non-broadcast period as a first noise pattern signal; a synchronous synthesis unit that generates a synthesized noise pattern signal by synchronizing and synthesizing a plurality of the first noise pattern signals; a deviation calculation unit that determines a start position for extracting the synthetic noise pattern signal based on a cross-correlation between a first signal that is a predetermined section of the received signal and the synthetic noise pattern signal, and calculates a phase adjustment amount based on a phase deviation between the first signal and the synthetic noise pattern signal; an extracting unit that extracts a predetermined section of the synthesized noise pattern signal from the start position to generate a second noise pattern signal; a phase adjustment unit that adjusts the phase of the second noise pattern signal based on the phase adjustment amount to generate a third noise pattern signal; a noise removal unit that generates a second signal by subtracting the third noise pattern signal from the first signal. Signal processing device.

8. A received signal is input, which is a time domain signal including a broadcast signal derived from a broadcast wave and a noise signal having peaks at regular time intervals; detecting non-broadcast periods, which are time periods that do not include the broadcast signal and exist at regular time intervals, from the received signal; extracting at least a portion of the received signal in the non-broadcast period as a first noise pattern signal; determining a start position for extracting the first noise pattern signal based on a cross-correlation between a first signal, which is the received signal in a predetermined section, and the first noise pattern signal, and calculating a phase adjustment amount based on a phase shift between the first signal and the first noise pattern signal; Signal processing methods.

9. A received signal is input, which is a time domain signal including a broadcast signal derived from a broadcast wave and a noise signal having peaks at regular time intervals; detecting non-broadcast periods, which are time periods that do not include the broadcast signal and exist at regular time intervals, from the received signal; extracting at least a portion of the received signal in the non-broadcast period as a first noise pattern signal; generating a composite noise pattern signal by synchronizing and combining a plurality of the first noise pattern signals; determining a start position for extracting the composite noise pattern signal based on a cross-correlation between a first signal that is a predetermined section of the received signal and the composite noise pattern signal, and calculating a phase adjustment amount based on a phase shift between the first signal and the composite noise pattern signal; generating a second noise pattern signal by extracting a predetermined section of the synthesized noise pattern signal from the start position; generating a third noise pattern signal by adjusting the phase of the second noise pattern signal based on the phase adjustment amount; generating a second signal by subtracting the third noise pattern signal from the first signal; Signal processing methods.

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