JP2012199739A - Reception device and signal processing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform high-quality content reproduction while rationally reducing an influence of an interference signal.SOLUTION: A power spectrum calculator 191 calculates power spectrum distribution of a signal IFD obtained by converting a desired wave signal transmitted from a desired station into a desired signal of a predetermined frequency band, and thereafter, calculates average spectrum distribution which is a time average of the power spectrum distribution obtained in a recent predetermined period. Subsequently, an interference signal distribution detector 194 identifies a continuous frequency range which includes, as the center frequency of the desired signal to be a center of symmetry, the center of symmetry in the average power spectrum distribution and is estimated to have high bilateral symmetry on a frequency axis, to be a range of a non-interference signal. Based on the identified non-interference signal range, a variable BPF controller 195 determines a frequency range to be passed through a variable BPF unit 130, and designates the determined frequency range to the variable BPF unit 130.

Description

  The present invention relates to a receiving device, a signal processing method, a signal processing program, and a recording medium on which the signal processing program is recorded.

  Conventionally, a receiving apparatus that receives and processes broadcast waves such as FM broadcast waves and reproduces sound is mounted on a moving body such as a vehicle. In such a receiving apparatus, adjacent interference in which an adjacent broadcast wave transmitted from an adjacent station adjacent to the desired broadcast wave on the frequency axis is mixed in the frequency band of the desired broadcast wave may occur.

  Techniques for reducing the influence of such adjacent interference have been proposed. As one of these proposed technologies, the signal level near the center frequency of the desired broadcast wave and the signal level near the center frequency of the adjacent broadcast wave are detected, and based on these detection results, an intermediate signal is adopted as the desired wave signal. There is a technique for determining a frequency range of a frequency signal (see Patent Document 1: hereinafter referred to as “conventional example”).

  In the conventional technique, the ratio (DU ratio) between the signal level of the desired broadcast wave and the signal level of the disturbing wave derived from the adjacent broadcast wave is obtained based on the detection result described above. Then, based on the obtained DU ratio value, the pass frequency range in the intermediate frequency filter through which the intermediate frequency signal passes is determined.

International Publication No. WO2007 / 000860

  In the technique of the conventional example described above, it is necessary to detect the signal level near the center frequency of the adjacent broadcast wave from the adjacent station, but the frequency difference between the adjacent broadcast wave and the desired broadcast wave may vary depending on the region. As a result, the number of adjacent broadcast waves that can be disturbing waves varies depending on the region. For this reason, when trying to detect the signal level of adjacent broadcast waves without depending on the area, it is necessary to prepare the number of band-pass filters for detection as many as the number of adjacent broadcast waves that can be interference waves, and the circuit scale is reduced. There is concern about becoming larger.

  In addition, when the desired broadcast wave is an FM broadcast wave, the degree of modulation may vary depending on the broadcast station. When the modulation degree is large, there is a concern that a part of the desired broadcast wave is detected as the adjacent broadcast wave even though the adjacent broadcast wave is not received.

  For this reason, there is a need for a technique that can appropriately reduce the interference signal even if the frequency of the adjacent broadcast wave that can be an interference wave or the modulation degree of the desired broadcast wave changes. Meeting this requirement is one of the problems to be solved by the present invention.

  The present invention has been made in view of the above circumstances, and provides a receiving apparatus and a signal processing method capable of reducing the influence of a disturbing signal with a simple configuration and rationally reducing high-quality content reproduction. The purpose is to do.

  The invention according to claim 1 is a receiving device that receives a broadcast signal, and converts a desired wave signal, which is a broadcast signal transmitted from a desired station, into a signal of a predetermined frequency band; A filter unit that selectively passes a component of the specified frequency range in the output signal from the front end unit according to the specification; a frequency that the filter unit is to pass based on the output signal from the front end unit; A control unit that designates a range for the filter unit, the control unit calculates a power spectrum distribution of the output signal after performing time-frequency conversion of the output signal, The time average left-right symmetry of the calculated power spectrum distribution is high with the frequency in the output signal corresponding to the center frequency as the center of symmetry. Based on continuous frequency range including the center of symmetry being valence, the filter unit is to determine the frequency range to pass, that is a receiving apparatus according to claim.

  According to a sixth aspect of the present invention, there is provided a front end unit that converts a desired wave signal, which is a broadcast signal transmitted from a desired station, into a signal of a predetermined frequency band; and an output signal from the front end unit according to a frequency range designation A signal processing method used in a receiving apparatus comprising: a filter unit that selectively passes a component in the specified frequency range of the output signal after performing time-frequency conversion of the output signal; A calculation step of calculating a power spectrum distribution; and it is evaluated that the time average left-right symmetry of the calculated power spectrum distribution is high with the frequency in the output signal corresponding to the center frequency of the desired wave signal as the symmetry center Based on a continuous frequency range including the center of symmetry, a frequency range to be passed by the filter unit is determined, and the determined A signal processing method characterized by comprising: a control step of designating against the frequency range the filter unit.

  A seventh aspect of the present invention is a signal processing program that causes a calculation means to execute the signal processing method according to the sixth aspect.

  The invention according to claim 8 is a recording medium in which the signal processing program according to claim 7 is recorded so as to be readable by the arithmetic means.

It is a block diagram which shows roughly the structure of the receiver which concerns on 1st Embodiment of this invention. It is a block diagram which shows the structure of the control unit of FIG. 3 is a flowchart for explaining a calculation process of an average power spectrum distribution by a power spectrum calculation unit of FIG. 2. It is a figure which shows the example (the 1) of average power spectrum distribution. 3 is a flowchart for explaining adjacent station signal information detection processing by an adjacent station signal information detection unit in FIG. 2; It is a figure which shows the example of the average power spectrum distribution of an adjacent station signal. 3 is a flowchart for explaining detection processing of desired station signal information by a desired station signal information detection unit of FIG. 2. It is a figure which shows the example of the average power spectrum distribution of a desired station signal. 3 is a flowchart for explaining detection processing of an interference signal distribution by an interference signal distribution detection unit in FIG. 2. It is a figure which shows the example of the power difference distribution obtained in the intermediate | middle stage of the detection process of disturbance signal distribution. It is a block diagram which shows roughly the structure of the receiver which concerns on 2nd Embodiment of this invention. It is a block diagram which shows the structure of the control unit of FIG. It is a figure which shows the example (the 2) of average power spectrum distribution. It is a figure which shows the average power spectrum distribution of a beat signal.

  Embodiments of the present invention will be described below with reference to the drawings. In the following description and drawings, the same or equivalent elements are denoted by the same reference numerals, and redundant description is omitted.

[First Embodiment]
First, a first embodiment of the present invention will be described with reference to FIGS. In the first embodiment, a receiving apparatus that receives FM broadcast waves and reproduces sound will be described as an example.

<Configuration>
FIG. 1 is a block diagram illustrating a schematic configuration of a receiving device 100A according to the first embodiment. As shown in FIG. 1, the receiving apparatus 100A includes an antenna 110 and an RF processing unit 120 as a front end unit. The receiving apparatus 100A includes a variable bandpass filter (BPF) unit 130 as a filter unit and a reproduction processing unit 150. Furthermore, the receiving device 100A includes an analog processing unit 160, a speaker unit 170, an operation input unit 180, and a control unit 190A as a control unit.

  The antenna 110 receives a broadcast wave (received signal). The reception result by the antenna 110 is sent to the RF processing unit 120 as a signal RFS.

  The RF processing unit 120 performs frequency conversion processing for converting the desired wave signal transmitted from the desired station to be selected into the desired station signal in the intermediate frequency band in accordance with the channel selection command CSL sent from the control unit 190A. The frequency conversion signal IFD (hereinafter referred to as “signal IFD”) is sent to the variable BPF unit 130 and the control unit 190A. The RF processing unit 120 includes an input filter, a high-frequency amplifier (RF-AMP: Radio Frequency-Amplifier), and a band-pass filter (hereinafter referred to as “RF filter”). The RF processing unit 120 includes a mixer (mixer), an AD (Analogue to Digital) converter, and a local oscillation circuit (OSC).

  Here, the input filter is a high-pass filter that blocks a low-frequency component of the signal RFS transmitted from the antenna 110. The high frequency amplifier amplifies the signal that has passed through the input filter. The RF filter selectively passes a signal in a high frequency band among signals output from the high frequency amplifier. The mixer mixes the signal that has passed through the RF filter and the local oscillation signal supplied from the local oscillation circuit, and performs frequency conversion so that the desired wave signal becomes a desired local signal in a predetermined intermediate frequency band.

  The AD converter converts the signal output from the mixer into a digital signal. This conversion result is sent to the variable BPF unit 130 and the control unit 190A as a signal IFD.

  Note that the local oscillation circuit includes an oscillator that can control the oscillation frequency by voltage control or the like. This local oscillation circuit generates a local oscillation signal having a frequency corresponding to a desired station to be selected in accordance with a channel selection command CSL sent from the control unit 190A, and supplies it to the mixer.

  The variable BPF unit 130 receives the signal IFD sent from the RF processing unit 120. Then, the variable BPF unit 130 passes the signal component in the frequency range specified by the variable BPF control specification VFC sent from the control unit 190A. The signal component that has passed through the variable BPF unit 130 is sent to the reproduction processing unit 150 as a signal BFD.

  The reproduction processing unit 150 includes a detection unit and a stereo demodulation unit. Here, the detection unit receives the signal BFD transmitted from the variable BPF unit 130. Then, the detection unit performs detection processing on the signal BFD and sends a detection result signal to the stereo demodulation unit.

  The stereo demodulator receives the detection result signal sent from the detector. The stereo demodulator performs a stereo demodulation process on the detection result signal. This stereo demodulation result is sent to the analog processing unit 160 as a demodulated signal DMD (hereinafter referred to as “signal DMD”). The signal DMD is composed of two signals, a left channel (hereinafter “L channel”) signal and a right channel (hereinafter “R channel”) signal.

  The analog processing unit 160 receives the signal DMD sent from the reproduction processing unit 150. Then, the analog processing unit 160 generates an output audio signal AOS under the control of the control unit 190A and sends it to the speaker unit 170.

  The analog processing unit 160 having such a function includes a DA (Digital to Analogue) conversion unit, a volume adjustment unit, and a power amplification unit. Here, the DA converter receives the signal DMD sent from the reproduction processing unit 150. The DA converter converts the signal DMD into an analog signal. Note that the DA conversion unit includes two DA converters configured in the same manner, corresponding to the L channel signal and the R channel signal included in the signal DMD. The signal of the analog conversion result by the DA conversion unit is sent to the volume adjustment unit.

  The volume adjustment unit receives the analog conversion result signal sent from the DA conversion unit. Then, the volume adjustment unit performs volume adjustment processing on the analog conversion result signals corresponding to the L channel and the R channel in accordance with the volume adjustment command VLC sent from the control unit 190A. In the first embodiment, the volume adjusting unit is configured to include two electronic volume elements configured in the same manner, corresponding to the L channel and the R channel. The signal of the volume adjustment result by the volume adjustment unit is sent to the power amplification unit.

  The power amplification unit receives the signals of the volume adjustment results of the L channel and the R channel sent from the volume adjustment unit. The power amplification unit power-amplifies the signal of the volume adjustment result. The power amplifying unit includes two power amplifiers configured similarly to each other, corresponding to the L channel and the R channel. An output audio signal AOS that is an amplification result by the power amplification unit is sent to the speaker unit 170.

  The speaker unit 170 includes an L channel speaker and an R channel speaker. The speaker unit 170 reproduces and outputs audio in accordance with the output audio signal AOS sent from the analog processing unit 160.

  The operation input unit 180 includes a key unit provided in the main body of the receiving device 100A, or a remote input device including the key unit. Here, as a key part provided in the main body, a touch panel provided in a display unit (not shown) can be used. Moreover, it can replace with the structure which has a key part, and the structure which inputs voice can also be employ | adopted. An operation input result to the operation input unit 180 is sent to the control unit 190A as operation input data IPD.

  The control unit 190A controls the operation of the entire receiving apparatus 100A. As shown in FIG. 2, the control unit 190 </ b> A includes a power spectrum calculation unit 191, an adjacent station signal information detection unit 192, a desired station signal information detection unit 193, and an interference signal distribution detection unit 194. . Further, the control unit 190A includes a variable BPF control unit 195 and a command input processing unit 199.

  The power spectrum calculation unit 191 receives the signal IFD sent from the RF processing unit 120. Subsequently, the power spectrum calculation unit 191 performs time frequency conversion on the signal IFD for each frame period of a predetermined time length, and then calculates an individual power spectrum distribution in the frame period based on the result of the time frequency conversion. . And the power spectrum calculation part 191 calculates the average power spectrum distribution of the individual power spectrum distribution obtained in the recent predetermined period. The average power spectrum distribution thus calculated is supplied as power spectrum distribution information PSD (hereinafter referred to as “information PSD”) to the adjacent station signal information detection unit 192, desired station signal information detection unit 193, and interference signal distribution detection unit 194. Sent.

  If there is only a signal corresponding to the selected broadcasting station in the intermediate frequency band, the time average of a sufficiently long period of the power spectrum distribution of the signal is theoretically on the frequency axis. The shape is nearly symmetrical. In the present invention, this fact is utilized.

  For this reason, when there is only a signal corresponding to the selected broadcasting station in the intermediate frequency band, the calculated average power spectrum distribution is likely to have a shape that is nearly symmetrical on the frequency axis. From the viewpoint that it can be expected statistically, the “predetermined period” is determined in advance based on experiments, simulations, experiences, and the like.

  The adjacent station signal information detection unit 192 receives the information PSD sent from the power spectrum calculation unit 191. Subsequently, the adjacent station signal information detection unit 192 extracts a power spectrum distribution in a predetermined frequency range centered on the center frequency corresponding to the adjacent broadcast wave from the average power spectrum distribution obtained as the information PSD. . The adjacent station signal information detector 192 detects the adjacent station signal power by calculating the sum of the individual power spectra in the power spectrum distribution thus extracted. The adjacent station signal power detected in this way is the adjacent station signal information NBD (hereinafter referred to as “information NBD”) together with the frequency difference between the center frequency of the desired wave transmitted from the selected broadcasting station and the center frequency of the adjacent broadcast wave. Is sent to the variable BPF control unit 195.

  In addition, from the viewpoint that the “predetermined frequency width” of the frequency range to be extracted by the adjacent station signal information detection unit 192 is a frequency range in which the degree of mixing of the signal corresponding to the desired wave is sufficiently low, It is determined in advance based on experiments, simulations, experiences, and the like.

  The desired station signal information detection unit 193 receives the information PSD sent from the power spectrum calculation unit 191. Subsequently, the desired station signal information detection unit 193 extracts a power spectrum distribution in a predetermined frequency range centering on the center frequency corresponding to the desired wave from the average power spectrum distribution obtained as the information PSD. The desired station signal information detection unit 193 detects the modulation degree of the desired wave based on the spread (for example, half width) of the power spectrum distribution thus extracted. In the first embodiment, the degree of modulation of the desired wave is detected based on the half width of the extracted power spectrum distribution.

  The desired station signal information detection unit 193 detects the desired station signal power by calculating the sum of the individual power spectra in the extracted power spectrum distribution. The detected desired station signal power is transmitted to the variable BPF control unit 195 as desired station signal information DBD (hereinafter referred to as “information DBD”) together with the modulation degree of the desired wave detected as described above. It is done.

  In addition, from the viewpoint that the “predetermined frequency width” of the frequency range to be extracted by the desired station signal information detection unit 193 is a frequency range in which the degree of mixing of signals corresponding to adjacent waves can be considered sufficiently low. It is determined in advance based on experiments, simulations, experiences, and the like.

  The interference signal distribution detection unit 194 receives the information PSD sent from the power spectrum calculation unit 191. Subsequently, the interference signal distribution detection unit 194 derives a power difference distribution from the average power spectrum distribution obtained as the information PSD. Here, the interference signal distribution detection unit 194 calculates the absolute value distribution of the difference between the power values at two frequencies having the same absolute value of the frequency difference from the center frequency corresponding to the desired wave in the average power spectrum distribution as the power difference. Derived as a distribution. Then, the interference signal distribution detection unit 194 includes a center frequency corresponding to the desired wave, and a continuous frequency range in which the absolute value of the power difference is equal to or less than a predetermined value is an interference signal no range in which there is no interference signal. Is specified. The non-jamming signal range thus specified is sent to the variable BPF control unit 195 as jamming signal distribution information NDT (hereinafter referred to as “information NDT”).

  The variable BPF control unit 195 includes information NBD sent from the adjacent station signal information detection unit 192, information DBD sent from the desired station signal information detection unit 193, and information sent from the interference signal distribution detection unit 194. Receive NDT. Subsequently, the variable BPF control unit 195 determines a frequency range that the variable BPF unit 130 should pass through among the signal components of the signal IFD based on the information NBD, DBD, and NDT. Then, the variable BPF control unit 195 sends control information for allowing the signal component in the determined frequency range to pass through the variable BPF unit 130 to the variable BPF unit 130 as the variable BPF control designation VFC.

  Details of the processing by the variable BPF control unit 195 will be described later.

The command input processing unit 199 receives the operation input data IPD sent from the operation input unit 180. If the content of the operation input data IPD is a channel selection designation, the command input processing unit 199 generates a channel selection command CSL corresponding to the designated desired station and sends it to the RF processing unit 120. If the content of the operation input data IPD is a volume adjustment designation, the command input processing unit 199 generates a volume adjustment instruction VLC corresponding to the designated volume adjustment designation and sends it to the analog processing unit 160. .
<Operation>
Next, the operation of the receiving apparatus 100A configured as described above will be described mainly focusing on the process for controlling the variable BPF unit 130 by the control unit 190A.

  As a premise, it is assumed that a channel selection designation has already been input to the operation input unit 180 by the user, and a channel selection command CSL corresponding to the designated desired station has been sent to the RF processing unit 120. Further, it is assumed that a volume adjustment designation has already been input by the user to the operation input unit 180, and a volume adjustment command VLC corresponding to the designated volume adjustment designation has been sent to the analog processing unit 160 (see FIG. 1).

  When a broadcast wave is received by the antenna 110 in such a state, a signal RFS is sent from the antenna 110 to the RF processing unit 120. Then, in the RF processing unit 120, after the signal of the desired station to be selected is converted into a signal in the intermediate frequency band, AD conversion is performed. The result of this AD conversion is sent as a signal IFD to the variable BPF unit 130 and the control unit 190A (see FIG. 1).

  In the control unit 190A that has received the signal IFD, processing for controlling the variable BPF unit 130 includes average power spectrum distribution calculation processing, adjacent station signal information detection processing, desired station signal information detection processing, interference signal distribution detection processing, and variable processing. A BPF control process is executed.

<< Average power spectrum distribution calculation process >>
The average power spectrum distribution calculation process is executed by the power spectrum calculation unit 191.

  In this average power spectrum calculation processing, as shown in FIG. 3, first, in step S11, the power spectrum calculation unit 191 calculates the current frame period, that is, the individual power spectrum distribution at the present time of the signal IFD. It is determined whether or not the collection period of the signal IFD for use has ended. If the result of this determination is negative (step S11: N), the process of step S11 is repeated.

  When the current frame period ends and the result of the determination in step S11 is affirmative (step S11: Y), the process proceeds to step S12. In step S12, the power spectrum calculation unit 191 calculates the individual power spectrum distribution of the signal IFD in the frame period.

  In calculating the individual power spectrum distribution, the power spectrum calculation unit 191 first performs time-frequency conversion on the signal IFD sent from the RF processing unit 120 during the frame period. Then, the power spectrum calculation unit 191 calculates the individual power spectrum distribution of the signal IFD in the frame period based on the result of the time frequency conversion.

  Next, in step S13, the power spectrum calculation unit 191 calculates an average power spectrum distribution of the individual power spectrum distributions obtained in a recent predetermined period. Then, the power spectrum calculation unit 191 reports the calculated average power spectrum distribution to the adjacent station signal information detection unit 192, desired station signal information detection unit 193, and interference signal distribution detection unit 194 as information PSD (FIG. 2). reference).

  When the process of step S13 ends, the process returns to step S11. Thereafter, the processes of steps S11 to S13 are repeated, and the average power spectrum distribution is calculated every time the frame period ends, and the calculated average power spectrum distribution is used as information PSD to be the adjacent station signal information detection unit. 192, the desired station signal information detector 193 and the interference signal distribution detector 194.

  An example of the average power spectrum distribution calculated in step S13 described above is shown in FIG. 4 as an average power spectrum distribution SPM (F) (F: frequency).

<Neighboring station signal information detection processing>
The adjacent station signal information detection process is executed by the adjacent station signal information detection unit 192.

  In this adjacent station signal information detection process, as shown in FIG. 5, first, in step S21, the adjacent station signal information detection unit 192 determines whether or not new information PSD has been received. If the result of this determination is negative (step S21: N), the process of step S21 is repeated.

  When new information PSD is received and the result of determination in step S21 is affirmative (step S21: Y), the process proceeds to step S22. In this step S22, the adjacent station signal information detection unit 192 is based on the average power spectrum distribution obtained as the new information PSD, and the adjacent station that is the source of the maximum disturbance signal with respect to the desired station signal. It is determined whether or not a certain maximum disturbing neighbor station has been identified.

  In performing the specific determination of the maximum disturbing adjacent station, the adjacent station signal information detection unit 192 firstly includes an adjacent station (hereinafter referred to as “disturbed adjacent station candidate”) that may generate a disturbing signal for the desired station signal. First adjacent station determination is performed to determine whether or not the power value at the center frequency of the adjacent station signal (hereinafter referred to as “interfering adjacent station signal candidate”) corresponding to each of the adjacent station signals is equal to or greater than a predetermined adjacent threshold. If there is no interfering adjacent station signal candidate for which the first adjacent station determination result is affirmative, the adjacent station signal information detection unit 192 determines that there is no interfering adjacent station. As a result, the result of the determination in step S22 is negative (step S22: N), and the process proceeds to step S24 described later.

Incidentally, the "predetermined adjacent threshold", from the viewpoint of the adjacent station signal can become an interference wave, corresponding to the frequency difference between the center frequency of the interfering neighbor candidate center frequency FD _C of the desired signal, experiments, simulations , Based on experience and the like. Here, the smaller the frequency difference, the smaller the “predetermined threshold value”.

  Next, the adjacent station signal information detection unit 192 has a power spectrum distribution spread (e.g., half-value width) of a disturbing adjacent station signal candidate for which the result of the first adjacent station determination is affirmative becomes a predetermined width or more. Whether or not there is a second adjacent station is determined. If there is no interfering adjacent station signal candidate for which the result of the second adjacent station determination is affirmative, the adjacent station signal information detection unit 192 determines that there is no interfering adjacent station. As a result, the result of the determination in step S22 is negative (step S22: N), and the process proceeds to step S24 described later.

  The “predetermined width” is determined in advance based on experiments, simulations, experiences, and the like from the viewpoint of determining whether or not it can be said that the power distribution corresponds to the broadcast wave transmitted from the adjacent station.

Next, the adjacent station signal information detection unit 192 has a center frequency of an adjacent station signal (hereinafter, referred to as “disturbed adjacent station signal”) that is a disturbing adjacent station signal candidate for which the second adjacent station determination result is positive. Based on the combination of the power and the frequency difference, the maximum disturbing adjacent station that is considered to have the maximum influence on the desired station signal is identified. As a result, the determination result in step S22 is affirmative (step S22: Y), and the process proceeds to step S23. If the result of determination in step S22 is affirmative, the frequency difference ΔF _DN between the center frequency FD _C of the desired station signal and the center frequency of the maximum disturbing adjacent station signal is used as information on the maximum disturbing adjacent station. 6) is obtained.

  Next, in step S23, the adjacent station signal information detection unit 192 calculates the adjacent station signal power corresponding to the maximum disturbing adjacent station. When calculating the adjacent station signal power, the adjacent station signal information detection unit 192 extracts a power spectrum distribution in a range of a predetermined frequency width WN (see FIG. 6) centering on the center frequency of the maximum disturbing adjacent station signal. To do. The adjacent station signal information detector 192 detects the adjacent station signal power by calculating the sum of the individual power spectra in the power spectrum distribution thus extracted. Then, the process proceeds to step S24.

In step S24, the adjacent station signal information detection unit 192 reports the information NBD to the variable BPF control unit 195. In this report, if it is determined in step S22 described above that there is no interfering adjacent station, the adjacent station signal information detection unit 192 reports the fact to the variable BPF control unit 195 as information NBD. On the other hand, when the frequency difference ΔF _DN and the adjacent station signal power are obtained in steps S22 and S23, they are reported to the variable BPF control unit 195 as information NBD (see FIG. 2).

  When the process of step S24 ends, the process returns to step S21. Thereafter, each time the average power spectrum distribution is calculated by repeating the processing of steps S21 to S24, the adjacent station information is detected, and the detection result is reported to the variable BPF control unit 195 as information NBD.

  In FIG. 6, an example of the power spectrum distribution extracted in step S24 is shown as a power spectrum distribution SPN (F).

<< desired station signal information detection process >>
The desired station signal information detection process is executed by the desired station signal information detection unit 193.

  In this desired station signal information detection process, as shown in FIG. 7, first, in step S31, the desired station signal information detection unit 193 determines whether or not new information PSD has been received. If the result of this determination is negative (step S31: N), the process of step S31 is repeated.

  When new information PSD is received and the result of determination in step S31 is affirmative (step S31: Y), the process proceeds to step S32. In step S32, the desired station signal information detection unit 193 detects the modulation degree of the desired station signal based on the average power spectrum distribution obtained as the new information PSD.

Upon detection of such modulation, the desired signal information detection unit 193, the power spectrum distribution in the range of the center frequency FD _C and centered predetermined desired station frequency width WD corresponding to the desired signal (see FIG. 8) To extract. Subsequently, the desired station signal information detection unit 193 obtains the half width HW (see FIG. 8) of the extracted power spectrum distribution. Then, the desired station signal information detection unit 193 detects the modulation degree of the desired station signal based on the obtained half width HW.

  Next, in step S33, the desired station signal information detection unit 193 calculates the power of the desired station signal. In this calculation, the desired station signal information detection unit 193 calculates the desired station signal power by calculating the sum of the individual power spectra in the power spectrum distribution extracted in step S32.

  Next, in step S34, the desired station signal information detection unit 193 reports the modulation degree and signal power of the desired station signal obtained as described above to the variable BPF control unit 195 as information DBD (see FIG. 2). ).

  When the process of step S34 ends, the process returns to step S31. Thereafter, each time the average power spectrum distribution is calculated by repeating the processes of steps S31 to S34, the desired station information is detected, and the detection result is reported to the variable BPF control unit 195 as information DBD.

  In FIG. 8, an example of the power spectrum distribution extracted in step S32 is shown as a power spectrum distribution SPD (F).

《Interference signal distribution detection processing》
The interference signal distribution detection process is executed by the interference signal distribution detection unit 194.

  In this interference signal distribution detection process, as shown in FIG. 9, first, in step S41, the interference signal distribution detection unit 194 determines whether or not new information PSD has been received. If the result of this determination is negative (step S41: N), the process of step S41 is repeated.

When new information PSD is received and the result of determination in step S41 is affirmative (step S41: Y), the process proceeds to step S42. In step S42, the interfering signal distribution detecting unit 194, the average power spectrum distribution obtained as new information PSD, power in two frequency absolute value is equal to the frequency difference from the center frequency FD _C of the desired signal A power difference distribution, which is a distribution of absolute values of value differences, is calculated.

Next, in step S43, the interference signal distribution detection unit 194 determines that the frequency difference is “0” when the absolute value of the power difference is equal to or less than a predetermined value ΔP _TH (see FIG. 10) in the calculated power difference distribution. A range WNN (see FIG. 10) continuing from the above is specified. Based on the specification result, the interfering signal distribution detecting unit 194 includes the center frequency of the desired signal, a symmetrical range in a continuous frequency axis absolute value of the power difference is less than the predetermined value [Delta] P _TH Detecting as no interference signal range where there is no interference signal.

  Next, in step S44, the interference signal distribution detection unit 194 reports the interference signal no range obtained as described above to the variable BPF control unit 195 as information NDT (see FIG. 2).

  When the process of step S44 ends, the process returns to step S41. Thereafter, each time the average power spectrum distribution is calculated by repeating the processes of steps S41 to S44, the detection of the no-interference signal range is performed, and the detection result is reported to the variable BPF control unit 195 as information NDT. .

In FIG. 10, an example of the power difference distribution calculated in step S42 is shown as a power difference distribution ΔP (ΔF). In FIG. 10, the absolute value of the difference between the center frequency FD _C of the desired station signal and the center frequency of the maximum disturbing adjacent station signal is shown as “ΔF _DN ”.

<< Variable BPF control process >>
The variable BPF control process is executed by the variable BPF control unit 195 that receives the information NBD, DBD, NDT detected each time a new average power spectrum distribution is calculated.

  In this variable BPF control process, the variable BPF control unit 195 first determines the frequency range that the variable BPF unit 130 should pass through by comprehensively considering the contents of the newly received information NBD, DBD, and NDT. An algorithm used for determining such a frequency range is determined in advance based on experiments, simulations, experiences, and the like from the viewpoint of maintaining reproduced sound quality.

  Note that the variable BPF control unit 195 determines the frequency range such that the wider the non-interference signal range, the wider the frequency range that the variable BPF unit 130 should pass. Further, the variable BPF control unit 195 determines the frequency range so that the frequency range of the signal component that the variable BPF unit 130 should pass through becomes wider as the modulation degree is higher.

Further, the variable BPF control unit 195, the center frequency FD _C and as the frequency difference [Delta] F _DN of the center frequency of the maximum interference neighboring station signal is high, the frequency range of the signal components to the variable BPF unit 130 passes the desired signal The frequency range is determined so as to increase. In addition, the variable BPF control unit 195 increases the frequency range of the signal component that the variable BPF unit 130 should pass as the ratio between the power of the desired station signal and the adjacent station signal power (so-called “DU ratio”) increases. Next, the frequency range is determined.

  Thus, when the frequency range to be passed by the variable BPF unit 130 is determined, the variable BPF control unit 195 sets the variable BPF unit 130 to set the variable BPF unit 130 to pass the signal component in the determined frequency range. Create a specified VFC. Then, the variable BPF control unit 195 sends the generated variable BPF control designation VFC to the variable BPF unit 130 (see FIG. 2).

  Under the control of the control unit 190A performed as described above, the variable BPF unit 130 that has received the signal IFD sent from the RF processing unit 120 as described above, the variable BPF control sent from the control unit 190A. Pass signal components in the frequency range specified by the specified VFC. The signal component that has passed through the variable BPF unit 130 is sent to the reproduction processing unit 150 as a signal BFD (see FIG. 1).

  In the reproduction processing unit 150 that has received the signal BFD, the detection unit performs detection processing on the signal BFD and sends a detection result signal to the stereo demodulation unit. Upon receiving the detection result signal, the stereo demodulation unit performs stereo demodulation processing including separation processing on the detection result signal. Then, the stereo demodulation unit sends the result of the stereo demodulation processing to the analog processing unit 160 as a signal DMD (see FIG. 1).

  In the analog processing unit 160 that has received the signal DMD sent from the reproduction processing unit 150, the DA conversion unit, the volume adjustment unit, and the power amplification unit sequentially process to generate an output audio signal AOS, and to the speaker unit 170. Send (see FIG. 1). Then, the speaker unit 170 reproduces and outputs sound in accordance with the output sound signal AOS from the analog processing unit 160.

  As described above, in the first embodiment, the power spectrum calculation unit 191 performs the time of the signal IFD in which the desired wave signal transmitted from the desired station by the RF processing unit 120 is converted into the desired station signal in the predetermined frequency band. Perform frequency conversion. Subsequently, the power spectrum calculation unit 191 calculates the power spectrum distribution of the signal IFD. And the power spectrum calculation part 191 calculates the average power spectrum distribution which is a time average of the power spectrum distribution obtained in the recent predetermined period.

Next, interference signal distribution detecting unit 194, as a symmetrical about the center frequency FD _C of the desired signal, the average power spectrum distribution, with including the symmetry center is evaluated as a high symmetry in the frequency domain The continuous frequency range is identified as no interfering signal range. Here, the interference signal distribution detection unit 194 calculates a power difference distribution that is a distribution of absolute values of differences between power spectrum values at two frequencies that are equidistant from the symmetry center, and then calculates the calculated power difference. Based on the difference distribution, left-right symmetry is evaluated on the frequency axis centered on the symmetry center of the average power spectrum distribution. Then, the variable BPF control unit 195 determines a frequency range that the variable BPF unit 130 should pass based on the specified no interference signal range, and designates the determined frequency range to the variable BPF unit 130. Do.

  Therefore, according to the first embodiment, high-quality audio reproduction can be performed with a simple configuration while rationally reducing the interference signal.

Further, in the first embodiment, the adjacent station signal information detection unit 192 causes the signal IFD if the component of the adjacent station signal corresponding to the broadcast signal transmitted from the adjacent station adjacent to the desired station on the frequency axis is equal to or higher than a predetermined level. , The power of the adjacent station component and the frequency difference ΔF _DN between the center frequency of the desired station signal and the center frequency of the adjacent station signal are detected. Further, the desired station signal information detection unit 193 detects the power of the desired station signal. Then, the variable BPF control unit 195 determines the frequency range that the variable BPF unit 130 should pass by further considering the ratio between the power of the desired station signal and the power of the adjacent station component and the frequency difference ΔF _DN . For this reason, it is possible to rationally reduce adjacent interference.

  In the first embodiment, the desired station signal information detection unit 193 detects the modulation degree of the desired station signal. Then, the variable BPF control unit 195 determines a frequency range that the variable BPF unit 130 should pass through, further considering the detected modulation degree. For this reason, it is possible to suppress signal distortion related to the desired station.

[Second Embodiment]
First, a second embodiment of the present invention will be described mainly with reference to FIGS. In the second embodiment, as in the case of the first embodiment described above, a receiving device that receives FM broadcast waves and reproduces sound will be described as an example.

<Configuration>
FIG. 11 is a block diagram illustrating a schematic configuration of a receiving device 100B according to the second embodiment. As shown in FIG. 11, the receiving device 100B further includes a notch filter unit 140 as a notch filter unit and an adaptive filter unit 145 as an adaptive filter unit, compared with the receiving device 100A described above, and The difference is that a control unit 190B is provided instead of the control unit 190A described above. Hereinafter, description will be made mainly focusing on these differences.

  The notch filter unit 140 is supplied with a signal BFD from the variable BPF unit 130. The adaptive filter unit 145 supplies a signal AFD to the reproduction processing unit 150.

  The notch filter unit 140 receives the signal BFD sent from the variable BPF unit 130. The notch filter unit 140 selectively blocks signal components in the vicinity of the frequency designated by the notch filter control designation NFC sent from the control unit 190B. The signal component that has passed through the notch filter unit 140 is sent to the adaptive filter unit 145 as a signal NFD.

  The adaptive filter unit 145 receives the signal NFD received from the notch filter unit 140. The adaptive filter unit 145 adaptively performs a filtering process on the signal NFD. The result of the filtering process by the adaptive filter unit 145 is sent to the reproduction processing unit 150 as a signal AFD.

  In the second embodiment, CMA (Constant Modulus Algorithm) is adopted as an adaptive filtering processing algorithm in consideration that the FM broadcast wave is originally constant in amplitude.

  As shown in FIG. 12, the control unit 190B is different from the control unit 190A described above in that it further includes a beat frequency detection unit 196 and a notch filter control unit 197.

  The beat frequency detection unit 196 receives the information PSD sent from the power spectrum calculation unit 191. Subsequently, the beat frequency detection unit 196 extracts a beat power distribution that is a power spectrum distribution corresponding to a beat signal having a narrow peak from the average power spectrum distribution obtained as information PSD. The beat frequency detection unit 196 detects the center frequency of the beat power distribution. The detection result by the beat frequency detection unit 196 is sent to the notch filter control unit 197 as beat frequency information BFD (hereinafter referred to as “information BFD”).

  The notch filter control unit 197 receives the information BFD sent from the beat frequency detection unit 196. Subsequently, the notch filter control unit 197 generates a notch filter control designation NFC that designates a frequency to be cut off by the notch filter unit 140 based on the frequency obtained as the information BFD. Then, the notch filter control unit 197 sends the generated notch filter control designation NFC to the notch filter unit 140.

<Operation>
Next, the operation of the receiving apparatus 100B configured as described above will be described mainly focusing on the processing for controlling the notch filter unit 140 by the control unit 190B.

  As a premise, it is assumed that a channel selection designation has already been input to the operation input unit 180 by the user, and a channel selection command CSL corresponding to the designated desired station has been sent to the RF processing unit 120. Further, it is assumed that a volume adjustment designation has already been input by the user to the operation input unit 180, and a volume adjustment command VLC corresponding to the designated volume adjustment mode has been sent to the analog processing unit 160 (FIG. 11).

  When a broadcast wave is received by the antenna 110 in such a state, the signal RFS is transmitted from the antenna 110 to the RF processing unit 120, as in the case of the first embodiment described above. Then, in the RF processing unit 120, after the signal of the desired station to be selected is converted into a signal in the intermediate frequency band, AD conversion is performed. The result of this AD conversion is sent as a signal IFD to the variable BPF unit 130 and the control unit 190B (see FIG. 11).

  In the control unit 190B that has received the signal IFD, as in the case of the control unit 190A described above, as processing for controlling the variable BPF unit 130, average power spectrum distribution calculation processing, adjacent station signal information detection processing, desired station signal Information detection processing and interference signal distribution detection processing are executed. Further, in the control unit 190B that has received the signal IFD, beat frequency detection processing and notch filter control processing are executed as processing for controlling the notch filter unit 140.

<Beat frequency detection processing>
The beat frequency detection process is executed by the beat frequency detection unit 196 that has received new information PSD from the power spectrum calculation unit 191.

  In FIG. 13, an example of the average power spectrum distribution calculated by the power spectrum calculation unit 191 is shown as an average power spectrum distribution SPM ′ (F).

In this beat frequency detection process, the beat frequency detection unit 196 extracts a power spectrum distribution corresponding to the beat signal from the average power spectrum distribution obtained as new information PSD. When extracting the power spectrum distribution corresponding to the beat signal, the beat frequency detecting unit 196 averages the peak portion having a narrow width and a peak power value equal to or greater than a predetermined peak power value PV _TH (see FIG. 14). Extract from the power spectrum distribution.

  Note that the “predetermined peak power value” is determined in advance based on experiments, simulations, experiences, and the like from the viewpoint that the beat signal may have a negative influence that cannot be ignored on the reproduction sound quality.

  Next, the beat frequency detection unit 196 identifies the center frequency of the extracted power spectrum distribution. Then, the beat frequency detecting unit 196 detects the identified frequency as the beat frequency FB. Then, the beat frequency detection unit 196 sends the detection result as information BFD to the notch filter control unit 197 (see FIG. 12).

  Each time the above beat frequency detection process receives new information PSD, the beat frequency detection unit 196 executes the beat frequency detection unit 196 to detect the beat frequency FB in the average power spectrum distribution obtained as the new information PSD. The detected beat frequency FB is reported to the notch filter control unit 197 as information BFD.

  In FIG. 14, an example of extracting the power spectrum distribution corresponding to the beat signal is shown as a power spectrum distribution BPM (F).

《Notch filter control processing》
The notch filter control process is executed by the notch filter control unit 197 that receives the information BFD detected each time a new average power spectrum distribution is calculated.

  In this notch filter control process, the notch filter control unit 197 first sets a notch filter unit 140 to set the notch filter unit 140 so as to block the signal component in the vicinity of the beat frequency FB obtained as the newly received information BFD. A filter control designation NFC is generated. Then, the notch filter control unit 197 sends the generated notch filter control designation NFC to the notch filter unit 140 (see FIG. 12).

  Under the control of the variable BPF unit 130 by the control unit 190B performed in the same manner as in the first embodiment, the variable BPF unit 130 that has received the signal IFD sent from the RF processing unit 120 as described above is controlled. The signal component in the frequency range designated by the variable BPF control designation VFC sent from the unit 190B is passed. The signal component that has passed through the variable BPF unit 130 is sent to the notch filter unit 140 as a signal BFD (see FIG. 11).

  Subsequently, under the control of the notch filter unit 140 by the control unit 190B performed as described above, the notch filter unit 140 that has received the signal BPF that has passed through the variable BPF unit 130 receives the notch sent from the control unit 190B. The signal component in the vicinity of the frequency designated by the filter control designation NFC is selectively cut off. The signal component that has passed through the notch filter unit 140 is sent to the adaptive filter unit 145 as a signal NFD (see FIG. 11).

  The adaptive filter unit 145 that receives the signal NFD sent from the notch filter unit 140 adaptively performs a filtering process on the signal NFD. The result of the filtering process by the adaptive filter unit 145 is sent to the reproduction processing unit 150 as a signal AFD (see FIG. 11).

  In the reproduction processing unit 150 that has received the signal AFD, as in the case of the first embodiment, the detection unit performs detection processing on the signal AFD and sends a detection result signal to the stereo demodulation unit. Upon receiving the detection result signal, the stereo demodulation unit performs stereo demodulation processing including separation processing on the detection result signal. Then, the stereo demodulation unit sends the result of the stereo demodulation processing to the analog processing unit 160 as a signal DMD (see FIG. 11).

  In the analog processing unit 160 that has received the signal DMD sent from the reproduction processing unit 150, the DA conversion unit, the volume adjustment unit, and the power amplification unit sequentially process the output audio as in the case of the first embodiment. A signal AOS is generated and sent to the speaker unit 170 (see FIG. 11). Then, the speaker unit 170 reproduces and outputs sound in accordance with the output sound signal AOS from the analog processing unit 160.

  As described above, in the second embodiment, as in the case of the first embodiment described above, the frequency range of the signal component that the variable BPF unit 130 should pass is controlled. Therefore, according to the second embodiment, as in the case of the first embodiment, it is possible to rationally reduce adjacent interference and suppress signal distortion related to a desired station with a simple configuration, and achieve high quality. Audio playback can be performed.

  In the second embodiment, the beat frequency detector 196 detects the beat frequency based on the average power spectrum distribution calculated by the power spectrum calculator 191. Then, the notch filter control unit 197 designates the frequency of the signal component to be cut off to the notch filter unit 140 based on the detected beat frequency.

  Therefore, according to the second embodiment, it is necessary to stop the operation of the adaptive filter unit 145 that performs the filtering process by the CMA algorithm effective for canceling the multipath noise in a weak electric field environment in consideration of the influence of the beat signal. Disappear. For this reason, it is possible to cancel multipath noise which is very effective in addition to rationally reducing adjacent interference.

[Modification of Embodiment]
The present invention is not limited to the above-described embodiment, and various modifications are possible.

  For example, in the first and second embodiments described above, when calculating the average power spectrum, it is assumed that the time average over a relatively long period is calculated for the individual power spectrum distribution. On the other hand, it is also possible to reduce the number of significant digits of the calculation result of the power difference performed when detecting the interference signal distribution while shortening the period to be subjected to time averaging.

  In the first and second embodiments, the variable bandpass filter (BPF) unit is used as the filter unit. However, the lowpass filter can change the passband of the signal according to the designation from the control unit. Etc. may be used.

  Moreover, the identification method of the maximum disturbance adjacent station in the detection of the adjacent station signal information in the first and second embodiments described above is an exemplification, and other identification methods can be adopted. For example, if the frequency difference between the desired station and the interfering adjacent station candidate is determined by the area, the maximum interfering adjacent station may be specified after specifying the area to which the current position of the receiving device belongs. Good.

  In the second embodiment, the notch filter unit is disposed between the variable BPF unit and the adaptive filter unit. However, the notch filter unit is disposed between the RF processing unit and the variable BPF unit. It may be.

  Further, the adaptive filter unit in the second embodiment may be configured as an IIR (Infinite Impulse Response) type filter or an FIR (Finite Impulse Response) type filter. Further, the IIR filter and the FIR filter may be switched according to the level detection result of the intermediate frequency signal.

  In the second embodiment, the adaptive filtering processing algorithm employed in the adaptive filter unit is CMA. However, other adaptive filtering processing algorithms may be employed.

  In the above embodiment, the present invention is applied to the FM receiver. However, the present invention can of course be applied to other types of broadcast receivers.

  The control units 190A and 190B in the first and second embodiments described above are configured as a computer as a calculation unit including a central processing unit (CPU), and a program prepared in advance is included in the computer. By executing the above, part or all of the processing in the first and second embodiments described above may be executed. This program is recorded on a computer-readable recording medium such as a hard disk, CD-ROM, or DVD, and is read from the recording medium and executed by the computer. The program may be acquired in a form recorded on a portable recording medium such as a CD-ROM or DVD, or may be acquired in a form distributed via a network such as the Internet. Also good.

100A, 100B ... Receiving device 120 ... RF processing unit (front end part)
130 ... Variable BPF unit (filter part)
140 ... Notch filter unit (notch filter section)
145 ... Adaptive filter unit (adaptive filter unit)
190A, 190B ... Control unit (control unit)

Claims (8)

A receiving device for receiving a broadcast signal,
A front end unit that converts a desired wave signal, which is a broadcast signal transmitted from a desired station, into a signal of a predetermined frequency band;
A filter unit that selectively passes components of the specified frequency range in the output signal from the front end unit according to the specification of the frequency range;
A control unit for designating a frequency range to be passed by the filter unit to the filter unit based on an output signal from the front end unit;
The controller is
After performing the time-frequency conversion of the output signal, calculate the power spectrum distribution of the output signal,
A continuous frequency range including the symmetry center evaluated with high time-average left-right symmetry of the calculated power spectrum distribution with the frequency in the output signal corresponding to the center frequency of the desired wave signal as the symmetry center. To determine a frequency range to be passed by the filter unit,
A receiving apparatus.   The control unit calculates the time of the calculated power spectrum distribution based on a difference between power spectrum values at two frequencies that are equidistant from the symmetry center on the time-average frequency axis of the calculated power spectrum distribution. The receiving apparatus according to claim 1, wherein average left-right symmetry is evaluated. The controller is
Based on the calculated power spectrum distribution when an adjacent station component corresponding to a broadcast signal transmitted from an adjacent station adjacent to the desired station on the frequency axis is included in the output signal at a predetermined level or higher. Calculating a ratio value between the level of the component corresponding to the desired wave signal in the output signal and the level of the adjacent station component;
Further considering the calculated ratio value, a frequency range to be passed by the filter unit is determined.
The receiving apparatus according to claim 1, wherein the receiving apparatus is a receiver. The desired signal is an FM broadcast signal;
The controller is
Based on the calculated power spectrum distribution, a modulation degree of the desired wave signal is calculated,
Further considering the calculated degree of modulation, a frequency range to be passed by the filter unit is determined,
The receiving device according to claim 1, wherein A notch filter unit that reduces a component of the designated level reduction frequency included in the output signal or a signal that has passed through the filter unit according to the designation of the level reduction frequency;
An adaptive filter unit that adaptively performs a filtering process on a signal that has passed through both the filter unit and the notch filter unit;
The control unit specifies the frequency of the beat signal when the beat signal is included in the output signal, and specifies the specified frequency to the notch filter unit.
The receiving apparatus according to claim 1, wherein the receiving apparatus includes: A front-end unit that converts a desired wave signal, which is a broadcast signal transmitted from a desired station, into a signal of a predetermined frequency band; and components of the specified frequency range in the output signal from the front-end unit according to the specification of the frequency range A signal processing method used in a receiving apparatus comprising: a filter unit that selectively passes
A calculation step of calculating a power spectrum distribution of the output signal after performing time-frequency conversion of the output signal;
A continuous frequency range including the symmetry center evaluated with high time-average left-right symmetry of the calculated power spectrum distribution with the frequency in the output signal corresponding to the center frequency of the desired wave signal as the symmetry center. A control step of determining a frequency range to be passed by the filter unit based on the control unit and designating the determined frequency range to the filter unit;
A signal processing method comprising:   A signal processing program for causing a calculation means to execute the signal processing method according to claim 6.   8. A recording medium, wherein the signal processing program according to claim 7 is recorded so as to be readable by an arithmetic means.

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