Equipment for detecting interference of signals in adjacent channels and method, and broadcast receiving equipment capable of using the method

Description: TECHNICAL FIELD [Detailed description of the invention]

【0001】

[Technical field to which the invention belongs]

The present invention relates to an adjacent interference detecting device and method capable of automatically detecting the state of adjacent interference in a broadcasting receiving device such as FM broadcasting, and a configuration of a broadcasting receiving device using the adjacent interference detecting device and method.

【0002】

[Conventional technology]

Generally, in an FM radio receiver or the like, when an interference signal is generated adjacent to a broadcast signal from a desired broadcasting station, so-called "adjacent interference", which is a deterioration of communication quality, occurs.

【0003】

Therefore, when such an adjacency interference occurs, it is detected and the pass bandwidth of the IF filter that passes the intermediate frequency signal (IF signal), which is the down-converted received signal, is changed on the receiver side. Then, measures such as reducing the influence of such an interfering signal are taken. However, in Europe, for example, since channels are adjacent in units of 100 KHz, interference signals cannot be completely removed by adjusting the pass band of the IF filter alone, and countermeasures against adjacent interference are one issue in the design of FM receivers and the like. ..

【0004】

As a method of detecting the presence or absence of such an interfering signal, for example, first, Japanese Patent Application Laid-Open No. 8-97738 compares the energies contained in the wide band and the narrow band centering on the frequency of the desired wave, and the comparison result is obtained. Based on this, a method for detecting the presence of adjacent interference is disclosed.

【0005】

Alternatively, in Japanese Patent Application Laid-Open No. 5-193112, an intermediate frequency filter is used to detect interfering waves existing in the upper and lower frequency bands of the desired reception signal, and the detected output is differentially amplified to obtain this differential. A technique for moving the center frequency of the IF filter for a desired signal to the smaller side of the interfering wave energy according to the amplified output is disclosed.

【0006】

[Problems to be Solved by the Invention]

According to the prior art as described above, although it is possible to detect an adjacent disturbing wave under specific conditions, there are the following problems.

【0007】

First, in the invention disclosed in Japanese Patent Application Laid-Open No. 8-97738, looking at the intensity ratio between the desired wave and the interfering wave (hereinafter referred to as the DU ratio), when the intermodulation described later occurs, it is detected. There is a problem that the range of DU ratio that can be created is narrowed.

【0008】

On the other hand, even in the method disclosed in JP-A-5-191312, the original intermodulation station and the modulation interference caused by such intermodulation sandwich the desired station under the condition that intermodulation interference occurs. Therefore, there is a problem that an erroneous judgment is caused.

【0009】

Hereinafter, this intermodulation interference will be described in more detail. FIG. 11 is a conceptual diagram for explaining such intermodulation.

【0010】

The front end of an FM receiver or the like that receives a signal received from an antenna and converts it to an intermediate frequency also amplifies the received wave, but the signal that has passed through such an amplifier causes so-called intermodulation distortion. ..

【0011】

As shown in FIG. 11, when two or more signals having different frequencies, for example, signals having frequencies fa and fb, are input to the high frequency amplifier, the input signals are connected to each other or the high frequency generated due to the non-linearity of the amplifier. Intermodulation occurs between them, causing so-called "spurious" at the output of the amplifier. That is, new interfering signals due to intermodulation may be generated on both sides of the signal input to the amplifier.

【0012】

FIG. 12 is a conceptual diagram showing the effect of such intermodulation interference in the presence of an interfering station in an FM receiver or the like as described above.

【0013】

As shown in FIG. 12, it is as explained in FIG. 11 that an interfering signal from the interfering station is generated near the frequency F of the desired station on the frequency side deviated by + Δf from the frequency of the desired station. Due to the influence of mutual modulation, a spurious signal is generated at a position opposite to the signal of the interfering station and deviated by -Δf from the frequency of the signal of the desired station with respect to the signal of the desired station.

【0014】

Therefore, for example, in the invention as disclosed in JP-A-5-191312 described above, the generation of interfering waves is detected by differential amplification of the signal levels on both sides of the signal from the desired station. There is a problem of causing an erroneous judgment.

【0015】

The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to accurately detect the occurrence of interfering stations over a wide range of DU ratios in FM broadcast receivers and the like. It is an object of the present invention to provide a possible adjacency detection device and a broadcast receiving device using the device.

【0016】

[Means for solving problems]

One aspect of the present invention relates to an adjacent interference detection device. This device has a first detector that outputs the difference value of the signal output that has passed through two band filters with different pass bands centered on the frequency of the desired wave, and a frequency higher and lower than the frequency of the desired wave, respectively. The first and second detections are made according to the output level of the interference wave generated adjacent to the desired wave and the second detection unit that outputs the added value of the signal output that has passed through the two band filters as the center frequencies. It includes an intensity ratio determining unit that selects an output value of any one of a plurality of detecting units including the unit and determines the intensity ratio of the desired wave and the interfering wave.

【0017】

The output level of the disturbing wave may be determined by comparing the output value of the first or second detection unit with a predetermined threshold value. When the output level of the disturbing wave is higher than a predetermined threshold value, the intensity ratio determination using the output value of the first detection unit is performed, and when the output level of the disturbing wave is lower than the predetermined threshold value, the first 2 The intensity ratio may be determined using the output value of the detection unit.

【0018】

The first detection unit has a wideband filter with a wide pass band centered on the frequency of the desired wave that can include adjacent interfering waves on both sides, and a narrow pass band centered on the frequency of the desired wave that does not include adjacent interfering waves on both sides. A narrowband filter with a band may be used. In the second detection unit, two band filters having a relatively narrow pass band that does not include the desired wave may be used, each having a pass band near the frequencies of adjacent interfering waves on both sides. The two band filters used in the second detection unit have a band filter whose center frequency is lower than the desired wave and whose upper limit is less than the center frequency of the desired wave, and a band filter whose center frequency is higher than the desired wave and whose lower limit is lower. It may be a filter in a band exceeding the center frequency of the desired wave.

【0019】

The intensity ratio determination unit further includes a third detection unit that outputs a difference value of signal output that has passed through two band filters having a frequency higher than the frequency of the desired wave and a frequency lower than the frequency of the desired wave, respectively, and the intensity ratio determination unit is the first. The intensity ratio may be determined by selecting the output value of any one of the plurality of detection units including the second and third detection units. The output level of the disturbing wave is divided into three stages, and in the range where the output level is high, the intensity ratio is determined using the difference value output by the first detection unit, and in the range where the output level is low, the third The intensity ratio may be determined using the difference value output by the detection unit, and the intensity ratio may be determined using the added value output by the second detection unit in the other intermediate range. By using the difference value by the third detection unit, the intensity ratio can be accurately determined even when the desired wave has a high degree of modulation.

【0020】

The pass bandwidth of the two band filters used in the third detector is made larger than the pass bandwidth of the two band filters used in the second detector, and the pass band includes the spread of the frequency of the desired wave to some extent. It may be a band.

【0021】

The second detection unit further outputs the difference value of the signal output that has passed through the two band filters whose center frequencies are higher and lower than the frequency of the desired wave, respectively, and the intensity determination unit further outputs the difference value of the signal output that has passed through the two band filters. The intensity ratio may be determined by selecting any one of the difference value output by the 1 detection unit, the addition value output by the second detection unit, and the difference value. By sharing the two band filters of the second detection unit, the addition value and the difference value can be obtained, and the configuration can be simplified.

【0022】

Another aspect of the present invention also relates to an adjacent interference detection device. This device has a first detector that outputs the added value of the signal output that has passed through two band filters whose central frequencies are higher and lower than the frequency of the desired wave, and a frequency higher than and lower than the frequency of the desired wave. The first detection unit outputs the difference value of the signal output that has passed through two band filters having a low frequency as the center frequency, and the first detection unit according to the output level of the interfering wave generated adjacent to the desired wave. And an intensity ratio determining unit for determining the intensity ratio of the desired wave and the interfering wave by selecting the output value of any one of the second detection unit. The output level of the disturbing wave is divided into three stages, and in the high range and the low range of the output level, based on the difference value by the second detection unit, and in the other intermediate range, the first detection unit. The intensity ratio of the desired wave and the disturbing wave may be determined based on the added value according to the above.

【0023】

Another aspect of the present invention relates to a broadcast receiver. This device includes a front-end unit that converts the FM broadcast signal received from the desired station into an intermediate frequency signal, and an adjacent interference detection unit that detects the intensity of the interference wave adjacent to the desired wave based on the intermediate frequency signal. An intermediate frequency filter unit that filters and outputs the intermediate frequency signal according to the intensity of the interfering wave, an FM detection unit that outputs an FM demodulated signal based on the output signal from the intermediate frequency filter unit, and the FM. It includes a stereo demodulation unit that demodulates the demodulated signal in stereo and outputs it. The adjacent interference detection unit includes a plurality of detection units that filter the interference wave signal in the peripheral frequency region of the desired wave frequency by different methods to detect and output the output level of the interference wave, and the interference wave. Including an intensity ratio determining unit that selects an output value of any one of the plurality of detection units according to the output level of the desired wave and determines the intensity ratio of the desired wave and the interfering wave.

【0024】

The plurality of detection units include a first detection unit that outputs a difference value of signal output that has passed through two band filters having different pass bands centered on the frequency of the desired wave, and a frequency higher and lower than the frequency of the desired wave. It may include a second detection unit that outputs an added value of signal outputs that have passed through two band filters having frequencies as center frequencies. The plurality of detection units may further include a third detection unit that outputs a difference value of signal output that has passed through two band filters having a frequency higher than the frequency of the desired wave and a frequency lower than the frequency of the desired wave as center frequencies, respectively.

【0025】

The intermediate frequency filter unit may adjust the bandwidth of the band filter through which the intermediate frequency signal is passed according to the intensity ratio. The stereo demodulation unit may adjust the degree of separation of the left and right channels in the stereo sound according to the intensity ratio. The stereo demodulation unit may change the ratio of removing the high frequency component of the FM demodulation signal according to the intensity ratio.

【0026】

Another aspect of the present invention relates to a method for detecting adjacent interference. This method focuses on the first detection step, which outputs the difference value of the signal output that has passed through two band filters with different pass bands centered on the frequency of the desired wave, and the frequencies higher and lower than the frequency of the desired wave, respectively. The second detection step of outputting the added value of the signal output passing through the two band filters as frequencies, and the first and second detection steps according to the output level of the interfering wave generated adjacent to the desired wave. This includes a determination step of selecting the output value of any one of the steps and determining the intensity ratio of the desired wave and the disturbing wave.

【0027】

The determination step further includes a third detection step of outputting the difference value of the signal output passing through the two band filters having a frequency higher than the frequency of the desired wave and a frequency lower than the frequency of the desired wave, respectively, and the determination step is the first and second. , And the output value of any one of the third detection steps may be selected to determine the intensity ratio.

【0028】

Another aspect of the present invention also relates to a method for detecting adjacent interference. In this method, the first detection step of outputting the sum of the signal outputs that have passed through the two band filters whose center frequencies are higher and lower than the frequency of the desired wave, and the frequencies higher and higher than the frequency of the desired wave and the frequency of the desired wave The second detection step, which outputs the difference value of the signal output that has passed through the two band filters whose center frequency is a low frequency, and the output level of the interfering wave generated adjacent to the desired wave are divided into three stages. In the high range and low range of the output level, the desired wave and the disturbing wave are based on the difference value obtained by the second detection step, and in the other intermediate ranges, based on the added value obtained by the first detection step. Includes a determination step of determining the strength ratio of.

【0029】

Another aspect of the present invention relates to an adjacent interference detection device for detecting an adjacent interference wave in the peripheral frequency region of a desired wave. This device uses the desired wave as the center frequency and the first signal that has passed through the filter in the first band, and the desired wave as the center frequency and the second signal that has passed through the filter in the second band narrower than the first passing band. The first adjacent interference detection unit that obtains the difference between the signal and the third signal that has passed the filter in the third band whose center frequency is lower than the desired wave and whose upper limit is lower than the center frequency of the desired wave and is higher than the desired wave. The intensity ratio of the desired wave and the jamming wave is the second adjacent jamming detector that finds the sum of the fourth signal that has passed through the filter in the fourth band whose lower limit exceeds the center frequency of the desired wave with the frequency as the center frequency. If the frequency is equal to or higher than a predetermined threshold, the interference wave is detected based on the output of the first adjacent interference detection unit, and if the intensity ratio is less than the predetermined threshold value, the interference wave is detected based on the output of the second adjacent interference detection unit. It is provided with an interfering wave determination unit to perform.

【0030】

The second adjacent interference detection unit receives an input signal and has a first bandpass filter having a third pass band, a first smoothing means for smoothing the output of the first bandpass filter, and a second bandpass filter. A second bandpass filter having a fourth pass band, a second smoothing means for smoothing the output of the second bandpass filter, and first and second smoothing means for receiving an input signal. It may include an addition means for receiving and adding the output of.

【0031】

Another aspect of the present invention relates to a broadcast receiver. This device has a receiving means for converting a broadcast signal from a desired desired station into an intermediate frequency, a filtering means for receiving an output of the receiving means and passing a signal having a bandwidth corresponding to a control signal, and an output of the filtering means. The adjacent interference detecting means includes a demodulating means for detecting and demodulating the signal, and an adjacent interference detecting means for detecting an adjacent interference wave in the peripheral frequency region of the desired wave based on the output of the receiving means. The difference between the first signal that has passed the filter in the first band with the desired wave as the center frequency and the second signal that has passed through the filter in the second band that has the desired wave as the center frequency and is narrower than the first pass band. The center frequency is the first adjacent interference detector to be obtained, the third signal that has passed through the filter in the third band whose center frequency is lower than the desired wave and the upper limit is less than the center frequency of the desired wave, and the frequency higher than the desired wave. The intensity ratio of the desired wave and the disturbing wave is equal to or greater than a predetermined threshold with the second adjacent interference detection unit that obtains the sum of the fourth signal that has passed through the filter in the fourth band whose lower limit exceeds the center frequency of the desired wave. In the case of, based on the output of the first adjacent interference detection unit, if the intensity ratio is less than a predetermined threshold value, the interference wave determination for detecting the interference wave is performed based on the output of the second adjacent interference detection unit. Including part.

【0032】

Any combination of the above components and a conversion of the expression of the present invention between methods, devices, systems and the like are also effective as aspects of the present invention.

【0033】

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiment 1 FIG. 1 is a schematic block diagram for explaining the configuration of the FM broadcast receiving device 100 according to the first embodiment.

【0034】

With reference to FIG. 1, the FM broadcast receiving device 100 includes an antenna 10, a front end portion 12 that receives a signal from the antenna 10 and performs channel selection processing, amplification processing, conversion processing to an intermediate frequency, and the like, and a front. The IF filter 14 is a band-passing filter that receives the output of the end unit 12 and passes an intermediate frequency signal in the desired band, and the FM detection unit 16 that receives the output of the IF filter 14 and performs FM detection. The DU ratio is detected from the outputs of the stereo demodulation unit 18 and the front end unit 12 that demodulate the signal and demodulate it into the stereo signals of the R signal and L signal, and control it to the IF filter 14. It is provided with an adjacent interference detection unit 200 that gives a signal.

【0035】

Here, the front end unit 12 is provided with an automatic gain control unit (not shown), and the intermediate frequency signal (IF signal) output from the front end unit is constant regardless of the electric field strength at the receiving point. It becomes the level of.

【0036】

In the present invention, if the output level of the interfering station is obtained, the level of the desired station that occupies the rest of the IF signal level can be known. Further, as will be described later, the DU ratio that can be detected by utilizing the fact that the DU ratio, that is, the ratio between the desired wave signal level and the adjacent interfering wave signal level can be obtained depending on the degree of output of the detected adjacent interfering station. It is possible to expand the range of.

【0037】

Again, with reference to FIG. 1, the IF filter 14 continuously and stepwise switches the passband based on the control signal from the adjacent jamming detector 200. For example, when the occurrence of an interfering signal is detected, the bandwidth of the IF filter 14 is reduced to a band where the interfering signal can be removed, and the output from the IF filter 14 having such a narrowed bandwidth is detected. Can be. When such control is performed, the adjacent interference can be effectively prevented only when the adjacent interference occurs, and when there is no adjacent interference, it is possible to obtain a good detection output for the distortion factor.

【0038】

FIG. 2 is a schematic block diagram illustrating the configuration of the adjacent interference detection unit 200 shown in FIG.

【0039】

The received signal converted from the antenna 10 through the front end unit 12 to the intermediate frequency (IF) is the first method adjacent interference detection unit 202 by the wide-narrow band difference method and the second method adjacent interference detection unit 204 by the adjacent band addition method. Given to.

【0040】

The DU ratio determination unit 210 determines the DU ratio of the received signal based on the outputs from the first and second method adjacent interference detection units 202 and 204, and gives the determination result to the IF filter 14 as a control signal.

【0041】

FIG. 3 is a schematic block diagram for explaining the configuration of the first method adjacent interference detection unit 202 shown in FIG.

【0042】

The first method adjacent interference detection unit 202 includes a wideband bandpass filter 2022 having a wide pass band centered on the frequency of the desired station, a smoothing processing unit 2024 for smoothing the output of the wideband bandpass filter 2022, and a smoothing processing unit 2024. Bandpass filter 2026 with a narrow pass band centered on the frequency of the desired wave, smoothing processing unit 2028 for smoothing the output of the narrow band bandpass filter 2026, and output of the smoothing processing units 2024 and 2028. It is equipped with a diffifier 2030 for calculating the difference.

【0043】

The degree of interference is the output of this diffifier 2030 and is given to the DU ratio determination unit 210. As will be described later, the output of the differential device 2030 is configured to normalize the outputs of the first method adjacent interference detection unit 202 and the second method adjacent interference detection unit 204 so as to be continuous at a predetermined threshold value. can do.

【0044】

FIG. 4 is a diagram showing the passage characteristics of the wideband bandpass filter 2022 and the narrowband bandpass filter 2026 shown in FIG.

【0045】

With the frequency F of the desired station as the center frequency, the pass band of the wideband bandpass filter has a wide pass band that can include interfering waves on both sides thereof.

【0046】

On the other hand, the narrow band bandpass filter has a narrow pass band centered on the frequency F of the desired station so as not to include the interfering wave. However, if the pass bandwidth is narrowed down to this narrow band bandpass filter, the distortion rate will increase if the signal that has passed through such a narrow band bandpass filter is detected by the detection circuit. In addition, it is not appropriate to use such a narrowband bandpass filter as the IF filter 14 of the FM receiver 100 when the degree of modulation is large.

【0047】

FIG. 5 is a schematic block diagram for explaining the configuration of the second method adjacent interference detection unit 204 shown in FIG.

【0048】

The second method adjacency detection unit 204 has a bandpass filter 2042 for detecting an adjacency on the minus side and an output of the bandpass filter filter 2042, in which the pass band is near the adjacent frequency on the lower frequency side when viewed from the desired wave. A smoothing processing unit 2044 for receiving and smoothing, a bandpass filter 2046 for detecting adjacent interference on the positive side, and a bandpass filter 2046 for detecting adjacent interference on the positive side, in which the vicinity of the adjacent frequency on the higher frequency side when viewed from the desired station is the pass band, and this bandpass. A smoothing unit 2048 for receiving the output of the filter 2046 and smoothing, and an adder 2050 that receives the outputs of the smoothing processing units 2044 and 2048 and outputs the sum signal to the DU ratio determination unit 210. And. As will be described later, the output of the adder 2050 is also normalized so that the outputs of the first method adjacent interference detection unit 202 and the second method adjacent interference detection unit 204 are continuous at a predetermined threshold value. can do.

【0049】

FIG. 6 is a diagram showing the passband characteristics of the bandpass filter 2042 for detecting the negative side adjacent interference and the bandpass filter 2046 for detecting the positive side adjacent interference shown in FIG.

【0050】

As shown in FIG. 6, the bandpass filter 2042 for detecting the adjacent interference on the negative side has a pass band in a region whose center frequency is Δf lower than the frequency F of the desired station, and the upper limit of the pass band is the desired wave. It is set to a relatively narrow passband so that it is below the center frequency of and does not include the desired wave. The bandpass filter 2046 for detecting adjacent interference on the positive side has a passband in a region whose center frequency is Δf higher than the frequency F of the desired station, and the lower limit of the passband exceeds the center frequency of the desired wave. It is set in a relatively narrow passband so as not to include the desired wave. It is assumed that the pass band width of both of these two bandpass filters 2042 and 2046 corresponds to the region of the interfering wave. For example, in the European specification, since channels are adjacent in units of 100 KHz, the value of Δf, which is the difference between the center frequency of the desired wave and the center frequency of the interfering wave to be detected, is set to 100 KHz.

【0051】

FIG. 7 is a diagram showing the DU ratio dependence of the difference value output from the first method adjacent interference detection unit 202 shown in FIG. 2 when intermodulation interference is received from an adjacent station. It is a figure which shows the DU ratio dependence of the addition value output output from the 2nd method adjacent interference detection part 204 shown in FIG. 2 when the intermodulation interference from an adjacent station is received.

【0052】

As shown in FIG. 7, for example, when the DU ratio is in the range of -30 to 0 dB, the output from the first method adjacent interference detection unit 202 accurately corresponds to the signal level of the interference station, but the DU ratio exceeds 0 dB. From around that point, the output level drops sharply, making it impossible to accurately determine the DU ratio.

【0053】

On the other hand, as shown in FIG. 8, the output from the second method adjacent interference detection unit 204 accurately corresponds to the signal level of the interference station even when the DU ratio is 0 to 30 dB, but on the contrary, the DU ratio is 0 dB or less. Then, it becomes impossible to accurately judge the DU ratio.

【0054】

Therefore, in determining the DU ratio, the output result of the first method adjacent interference detection unit 202 by the wide / narrow band difference method is used in the range of DU ratio of -30 to 0 dB, and the adjacent band is used in the range of DU ratio of 0 to + 30 dB. By using the output result of the second method adjacent interference detection unit 204 by the addition method, it is possible to detect good interference waves over a wide range of DU ratios.

【0055】

That is, in the DU ratio determination unit 210, in this way, in the first predetermined range of the DU ratio, for example, in the range of -30 to 0 dB as described above, the interference wave is based on the output from the first method adjacent interference detection unit 202. In the second predetermined range where the DU ratio becomes larger than the first predetermined range, for example, in the range of 0 to +30 dB as described above, based on the output from the second method adjacent interference detection unit 204. Detects disturbing waves.

【0056】

FIG. 9 is a diagram showing the DU ratio dependence of the signal level on which the DU ratio determination unit 210 detects an interfering wave, which is the basis of the determination, in this way.

【0057】

The detection range of the DU ratio can be expanded by using the characteristics of the first and second method adjacent interference detection units 202 and 204 shown in FIGS. 7 and 8 separately for each region. At this time, which of the output values of the first and second method adjacent interference detection units 202 and 204 is used depends on, for example, the output value from the first method adjacent interference detection unit 202 that uses the wide-narrow band difference method, and the DU ratio. This is performed based on the judgment result of whether or not is 0 or more.

【0058】

FIG. 10 is a flowchart for explaining the operation of the adjacent interference detection unit 200 shown in FIG.

【0059】

With reference to FIG. 10, when the DU ratio determination process is first started (S100), it is determined whether or not the difference value by the wide / narrow band difference method exceeds the threshold value (S102).

【0060】

When the threshold value is exceeded, the difference value in the wide and narrow bands from the first method adjacent interference detection unit 202 is output, for example, the value normalized to the range of 1 to 0.5 is included in the control signal as the DU ratio judgment data. (S104), the process ends (S110).

【0061】

On the other hand, if it is determined in step S102 that the wide / narrow band difference value does not exceed a predetermined threshold value, the output from the second method adjacent interference detection unit 204, that is, the determination value based on the adjacent band addition value is received. , DU ratio determination unit 210 outputs the output from the second method adjacent interference detection unit 204, for example, a value normalized to the range of 0.5 to 0 as DU ratio determination data, including it in the control signal (S106). ), The process ends (S110).

【0062】

As described above, according to the present embodiment, the level of the interfering wave is determined in a predetermined range of the DU ratio based on the difference value of the signals that have passed through the wideband and narrowband bandpass filters, and this predetermined level is determined. If the interfering wave becomes larger than the range of, the level of the interfering wave is determined based on the value obtained by adding the outputs from the two bandpass filters whose passing regions are the adjacent bands on both sides of the desired wave. Therefore, it is possible to detect the state of adjacent interference over a wider range of DU ratios.

【0063】

Embodiment 2 FIG. 13 is a configuration diagram of the FM broadcast receiving device 100 according to the second embodiment. A configuration and operation different from those of the first embodiment will be described. The DU ratio data 15 output by the adjacent interference detection unit 200 is given to the IF filter 14 and the stereo demodulation unit 18.

【0064】

FIG. 14 is a configuration diagram of the adjacent interference detection unit 200. The difference from the adjacency detection unit 200 of the first embodiment is that the third method adjacency detection unit 206 is provided, and the output of the third method adjacency detection unit 206 is given to the DU ratio determination unit 210. The DU ratio determination unit 210 determines the DU ratio of the received signal based on the outputs from the first, second and third adjacent interference detection units 202, 204 and 206, and demodulates the DU ratio data with the IF filter 14 in stereo. Give to part 18.

【0065】

In the first embodiment, the detection range of the DU ratio can be expanded by the combination of the first method adjacent interference detection unit 202 and the second method adjacent interference detection unit 204, but when the modulation degree of the desired wave signal is high. Even when there is no interference wave signal, both the wide / narrow band difference value by the first method adjacent interference detection unit 202 and the adjacent band addition value by the second method adjacent interference detection unit 204 become large values. It is erroneously determined that there is an interfering wave signal. Therefore, in the present embodiment, the DU ratio is determined by further using the third method adjacent interference detection unit 206 so that the DU ratio can be detected more accurately in the range where the level of the interference wave is small.

【0066】

FIG. 15 is a configuration diagram of the third method adjacent interference detection unit 206. The third method adjacent interference detection unit 206 receives the output of the negative side adjacent interference detection bandpass filter 2062 and the output of this bandpass filter 2062, in which the vicinity of the adjacent frequency on the lower frequency side when viewed from the desired wave is the pass band. The smoothing processing unit 2064 for smoothing, the bandpass filter 2066 for detecting the adjacent interference on the positive side where the pass band is near the adjacent frequency on the higher frequency side when viewed from the desired station, and the bandpass filter 2066. The absolute value of the output of the smoothing processing unit 2068 for receiving and smoothing the output, the differencer 2070 that receives the output of the smoothing processing units 2064 and 2068 and outputs the signal of the difference, and the differencer 2070. It is provided with an absolute value output unit 2072 that outputs to the DU ratio determination unit 210. The output of the diffifier 2070 is normalized so that the outputs of the first method adjacency detection unit 202, the second method adjacency detection unit 204, and the third method adjacency detection unit 206 are continuous at a predetermined threshold value. Can be.

【0067】

FIG. 16 is a diagram showing the passband characteristics of the bandpass filter 2062 for detecting the negative side adjacent interference and the bandpass filter 2066 for detecting the positive side adjacent interference shown in FIG. As shown in FIG. 16, the bandpass filter 2062 for detecting the adjacent interference on the negative side has a pass band in a region whose center frequency is Δf lower than the frequency F of the desired station, and the upper limit of the pass band is the desired one. Although it is less than the center frequency of the wave, it is set to a relatively wide passband so as to include the peripheral frequency of the desired wave to some extent. The bandpass filter 2066 for detecting adjacent interference on the positive side has a passband in a region whose center frequency is Δf higher than the frequency F of the desired station, and the lower limit of the passband exceeds the center frequency of the desired wave. , It is set in a relatively wide pass band so as to include the peripheral frequency of the desired wave to some extent. For both of these two bandpass filters 2062 and 2066, the pass bandwidth is assumed to correspond to the region of the interfering wave, and the pass bandwidth is set to a value of about 1.5Δf as an example. Alternatively, it may be set to a value in the range of 7.5Δf to 2.25Δf.

【0068】

FIG. 17 is a configuration diagram of the IF filter 14 shown in FIG. The IF filter 14 switches the wideband IF filter 142, the medium band IF filter 144, and the narrow band IF filter 146 by the switch 148, passes the IF signal, and gives it to the FM detection unit 16. The switch 148 is switched according to the value of the DU ratio data 15. When the DU ratio is small, that is, the level of the interfering wave is high, the narrow band IF filter 146 with high selectivity is switched, and when the DU ratio is large, that is, the level of the interfering wave is low, the wide band IF filter 142 is switched to, and the interfering wave is generated. If it is at an intermediate level, switch to the mid-band IF filter 144.

【0069】

FIG. 18 is a configuration diagram of the stereo demodulation unit 18 shown in FIG. The LR sub-signal and L + R main signal of the stereo composite signal FM demodulated by the FM detection unit 16 are input to the stereo demodulation unit 18. The LR sub-signal is amplified by the amplifier 180 and input to the adder 182 and the diffifier 184. On the other hand, the L + R sub signal is directly input to the adder 182 and the diffifier 184. The L signal is output from the adder 182, and the R signal is output from the diffifier 184. Here, the gain K of the amplifier 180 is adjusted according to the DU ratio data 15. As a result, the degree of separation of the left and right channels in the stereo sound changes, and separation control is performed according to the level of the interfering wave.

【0070】

The L signal output from the adder 182 is input to the amplifier 191 with a gain α, and after passing through the low-pass filter 186, is input to the amplifier 192 with a gain (1-α). The outputs from the two amplifiers 191 and 192 are added by the adder 196 to finally output the L signal.

【0071】

The R signal output from the adder 184 is input to the amplifier 193 with a gain α, and after passing through the low-pass filter 188, is input to the amplifier 194 with a gain (1-α). The outputs from the two amplifiers 193 and 194 are added by the adder 198 to finally output the R signal.

【0072】

The gain α values of the four amplifiers 191 to 194 are adjusted according to the DU ratio data 15, and high-cut control is performed. That is, when the level of the interfering wave is high, the gain α can be reduced and the weighting of the signals passed through the low-pass filters 186 and 188 can be increased to cut the high frequency component.

【0073】

FIG. 19 is a flowchart illustrating a DU ratio determination procedure by the adjacent interference detection unit 200 shown in FIG. First, when the DU ratio determination process is started (S200), it is determined whether or not the difference value by the wide / narrow band difference method exceeds the first threshold value (S202). This first threshold value is preset as the value of the wide / narrow band difference value output by the first method adjacent interference detection unit 202 when the DU ratio corresponds to, for example, 0 dB. When the wide / narrow band difference value exceeds the first threshold value (Y of S202), it can be determined that the DU ratio is less than 0 dB, and the wide / narrow band difference value from the first method adjacent interference detection unit 202 is, for example, 1 to 0.6. Normalizes to the range of, outputs as DU ratio determination data (S204), and ends the DU ratio determination process (S212).

【0074】

On the other hand, in step S202, when the wide / narrow band difference value does not exceed the first threshold value (N in S202), it is then determined whether or not the difference value by the adjacent band difference method exceeds the second threshold value (S206). ). This second threshold value is preset as an adjacent band difference value output by the third method adjacent interference detection unit 206 when the DU ratio corresponds to, for example, 30 dB. When the adjacent band difference value does not exceed the second threshold value (N of S206), it can be determined that the DU ratio is 30 dB or more, and the adjacent band difference value from the third method adjacent interference detection unit 206 is, for example, 0.2. After normalizing to the range of ~ 0, it is output as DU ratio judgment data (S210), and the DU ratio judgment process is completed (S212).

【0075】

On the other hand, in step S206, when the adjacent band difference value exceeds the second threshold value (Y in S206), it can be determined that the DU ratio is between 0 dB and 30 dB, and the second method adjacent interference detection unit 204 After normalizing the adjacent band addition value from, for example, to the range of 0.6 to 0.2, it is output as the DU ratio judgment data (S208), and the DU ratio processing is terminated (S212).

【0076】

Embodiment 3 The configuration of the FM broadcast receiving device 100 according to the third embodiment is the same as that of the second embodiment shown in FIG. 13, and the configuration of the adjacent interference detection unit 200 is the same as that of the first embodiment shown in FIG. , The first method adjacency detection unit 202, the second method adjacency detection unit 204, and the DU ratio determination unit 210 are provided, and the configuration of the second method adjacency detection unit 204 is different from that of the first embodiment. FIG. 20 shows the configuration of the second method adjacent interference detection unit 204 of the present embodiment.

【0077】

The second method adjacent interference detection unit 204 receives the output of the negative side adjacent interference detection bandpass filter 2082 and the output of the bandpass filter 2082, in which the vicinity of the adjacent frequency on the lower frequency side when viewed from the desired wave is the pass band. The smoothing processing unit 2084 for smoothing, the bandpass filter 2086 for detecting the adjacent interference on the positive side where the passband is near the adjacent frequency on the higher frequency side when viewed from the desired station, and the bandpass filter 2086. The DU ratio is the absolute value of the output of the smoothing processing unit 2088 for receiving the output and smoothing, the difference device 2090 that receives the output of the smoothing processing units 2084 and 2088 and outputs the difference, and the difference device 2090. It includes an absolute value output unit 2092 that outputs to the determination unit 210, and an adder 2094 that receives the outputs of the smoothing processing units 2084 and 2088 and outputs the sum to the DU ratio determination unit 210. The outputs of the difference device 2090 and the adder 2094 can be normalized so that the outputs of the first method adjacent interference detection unit 202 and the second method adjacent interference detection unit 204 are continuous at a predetermined threshold value. ..

【0078】

The present embodiment differs from the second embodiment in the following points. In the second embodiment, each of the second method adjacency detection unit 204 and the third method adjacency detection unit 206 has a bandpass filter for negative side adjacency detection and positive side adjacency detection, and the second embodiment. The two-method adjacent interference detection unit 204 calculated the adjacent band addition value, and the third method adjacent interference detection unit 206 calculated the adjacent band difference value. In the present embodiment, the configuration of the bandpass filter and the smoothing processing unit is shared, and both the adjacent band addition value and the adjacent band difference value are output only by the configuration of the second method adjacent interference detection unit 204. This makes it possible to simplify the configuration of the adjacent interference detection unit 200. On the other hand, in the adjacency detection unit 200 of the second embodiment, the second method adjacency detection unit 204 for calculating the adjacency band addition value and the third method adjacency detection unit 206 for calculating the adjacency band difference value are used. , There is an advantage that the pass band and the center frequency of the bandpass filter can be different.

【0079】

Embodiment 4 FIG. 21 is a configuration diagram of the adjacent interference detection unit 200 according to the fourth embodiment. In the present embodiment, the adjacency detection unit 200 includes the second method adjacency detection unit 204, the third method adjacency detection unit 206, and the DU ratio determination unit 210, and is different from other embodiments in a wide and narrow band. The first method adjacent interference detection unit 202 that calculates the difference value is not included. The configuration of the second method adjacent interference detection unit 204 and the third method adjacent interference detection unit 206 is the same as that of the second embodiment. The present embodiment is characterized in that the third method adjacent interference detection unit 206 of the adjacent band difference method is also used as a substitute for the first method adjacent interference detection unit 202 of the broadband difference method.

【0080】

FIG. 22 is a flowchart illustrating a DU ratio determination procedure by the adjacent interference detection unit 200 according to the present embodiment. First, when the DU ratio determination process is started (S300), it is determined whether or not the difference value by the adjacent band difference method exceeds the first threshold value (S302). This first threshold value is preset as the value of the adjacent band difference value output by the third method adjacent interference detection unit 206 when the DU ratio corresponds to, for example, 0 dB. When the adjacent band difference value exceeds the first threshold value (Y of S302), it can be determined that the DU ratio is less than 0 dB, and the adjacent band difference value from the third method adjacent interference detection unit 206 is, for example, 1 to 0.6. Normalizes to the range of, outputs as DU ratio judgment data (S304), and ends the DU ratio judgment processing (S312).

【0081】

On the other hand, in step S302, when the adjacent band difference value does not exceed the first threshold value (N in S302), then it is determined whether or not the adjacent band difference value exceeds the second threshold value (S306). This second threshold value is preset as an adjacent band difference value output by the third method adjacent interference detection unit 206 when the DU ratio corresponds to, for example, 30 dB. When the adjacent band difference value does not exceed the second threshold value (N of S306), it can be determined that the DU ratio is 30 dB or more, and the adjacent band difference value from the third method adjacent interference detection unit 206 is, for example, 0.2. After normalizing to the range of ~ 0, it is output as DU ratio judgment data (S310), and the DU ratio judgment process is completed (S312).

【0082】

On the other hand, in step S306, when the adjacent band difference value exceeds the second threshold value (Y in S306), it can be determined that the DU ratio is between 0 dB and 30 dB, and the second method adjacent interference detection unit 204 After normalizing the adjacent band addition value from, for example, to the range of 0.6 to 0.2, it is output as the DU ratio judgment data (S308), and the DU ratio processing is completed (S312).

【0083】

In the present embodiment, since the configuration does not include the adjacent interference detection unit of the broadband difference method, the configuration of the adjacent interference detection unit 200 can be simplified.

【0084】

As described above, in any of the embodiments, by selecting the calculation output from the plurality of adjacent interference detection units according to the DU ratio according to the configuration of the adjacent interference detection unit 200, the calculation output from the plurality of adjacent interference detection units is selected over a wide range of DU ratios. It is possible to accurately determine the level of adjacent interference.

【0085】

The present invention has been described above based on the embodiments. It will be appreciated by those skilled in the art that these embodiments are exemplary and that various modifications are possible for each of these components and combinations of processing processes, and that such modifications are also within the scope of the present invention. By the way. Further, each component is illustrated as a functional block, and it is understood by those skilled in the art that these functional blocks can be realized in various forms by hardware only, software only, or a combination thereof. The adjacent interference detection unit of any of the embodiments can be made into an LSI to form a single device, and this may be incorporated into an FM receiver or the like for use.

【0086】

[Effect of the invention]

According to the present invention, the level of adjacency interference can be accurately detected in a wider DU ratio range.

[Simple explanation of drawings]

[Figure 1]

It is a schematic block diagram for demonstrating the configuration of the FM broadcast receiving apparatus which concerns on Embodiment 1. FIG.

[Figure 2]

It is a schematic block diagram explaining the structure of the adjacent interference detection part shown in FIG.

[Fig. 3]

It is a schematic block diagram for demonstrating the structure of the 1st method adjacent interference detection part of FIG.

[Fig. 4]

It is a figure which shows the passing characteristic of the wideband bandpass filter and the narrowband bandpass filter of FIG.

[Fig. 5]

It is a schematic block diagram for demonstrating the structure of the 2nd method adjacent interference detection part of FIG.

[Fig. 6]

It is a figure which shows the pass band characteristic of the two bandpass filters of FIG.

[Fig. 7]

It is a figure which shows the DU ratio dependence of the difference value output from the 1st system adjacency interference detection part when the intermodulation interference is received from the adjacent station.

[Fig. 8]

It is a figure which shows the DU ratio dependence of the addition value output from the 2nd system adjacent interference detection part when the intermodulation interference is received from the adjacent station.

[Fig. 9]

It is a figure which shows the DU ratio dependence of the signal level which is the basis of the determination when the DU ratio determination part of FIG. 2 detects an interfering wave.

[Fig. 10]

It is a flowchart explaining the DU ratio determination procedure by the adjacent interference detection part which concerns on Embodiment 1. FIG.

[Fig. 11]

It is a conceptual diagram for demonstrating intermodulation.

[Fig. 12]

It is a conceptual diagram which shows the influence which intermodulation interference has influence when the interference station exists in FM receiver and the like.

[Fig. 13]

It is a block diagram of the FM broadcast receiving apparatus which concerns on Embodiment 2. FIG.

[Fig. 14]

It is a block diagram of the adjacent interference detection part of FIG.

[Fig. 15]

It is a block diagram of the 3rd method adjacent interference detection part of FIG.

[Fig. 16]

It is a figure which shows the pass band characteristic of the two bandpass filters of FIG.

[Fig. 17]

It is a block diagram of the IF filter of FIG.

[Fig. 18]

It is a block diagram of the stereo demodulation part of FIG.

[Fig. 19]

It is a flowchart explaining the DU ratio determination procedure by the adjacent interference detection part which concerns on Embodiment 2.

[Fig. 20]

It is a block diagram of the 2nd method adjacent interference detection part of the adjacent interference detection part which concerns on Embodiment 3. FIG.

[Fig. 21]

It is a block diagram of the adjacent interference detection part which concerns on Embodiment 4. [Fig. 22]

It is a flowchart explaining the DU ratio determination procedure by the adjacent interference detection part which concerns on this Embodiment.

[Explanation of symbols]

10 antennas, 12 front-ends, 14 IF filters, 16 FM detectors, 18 stereo demodulators, 100 FM broadcast receivers, 200 adjacency detectors, 202 1st method adjacency detectors, 204 2nd system adjacency detectors , 206 3rd method adjacent interference detection unit, 210 DU ratio determination unit.