JP3506950B2 - FM receiver - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an FM receiver capable of removing adjacent interference.

[0002]

In recent years, due to the increase in the number of broadcasting stations, the frequency interval with other broadcasting stations has become closer,
Along with this, good reception is hindered by interference or interference between the tuning frequency signal of the desired broadcast station and the frequency signal of another adjacent broadcast station received by the FM receiver, so-called adjacent interference. Increasing reception failures are occurring.

A conventional FM receiver removes adjacent interference by switching the IF filter when the above-mentioned adjacent interference is detected. That is, as shown in FIG. 10, the conventional FM receiver inputs the intermediate frequency (IF) signal output from the front end 1 to the wide band IF filter 2A having a wide band filter characteristic when there is no adjacent interference. Then, the band-pass signal is output to the limiter circuit 3, but when a microcomputer (not shown) detects an adjacent interfering signal based on the S meter output obtained by AM detection of the received wave. By switching the filter changeover switch SW to, the IF signal has a narrow band I having narrow band filter characteristics.
The narrow band IF filter 2 is input to the F filter 2B.
By B, the adjacent interfering signal is removed.

However, in such a conventional FM receiving apparatus, when the IF filter is switched, the SN ratio and TH are sharp.
There is a problem that D becomes worse. Then, it is necessary to provide a plurality of IF filters having different bands in order to remove adjacent interference, which causes a problem of high product cost.
The present invention has been made to solve the problems in the conventional FM receiving apparatus as described above. That is, it is an object of the present invention to provide an FM receiver which can eliminate adjacent interference, and which has a small effect on sound quality and a low product cost.

[0005]

In order to achieve the above object, an FM receiver according to a first aspect of the present invention comprises an FM detection output output from an FM detection circuit and an S meter output output from an AM detection circuit. A disturbing direction detecting means for detecting whether the frequency of the adjacent disturbing wave is higher or lower than the frequency of the desired wave based on the correlation, and the tuning frequencies are made adjacent to each other based on the disturbing direction detecting signal output from the disturbing direction detecting means. Tuning frequency shifting means for shifting in the opposite direction to the direction in which the disturbance exists is provided.

In the FM receiver according to the first aspect of the present invention, when the adjacent interference occurs, the interference direction detecting means provides the FM detection output output from the FM detection circuit and the S meter output output from the AM detection circuit. It is detected whether the frequency of the adjacent interfering wave is higher or lower than the frequency of the desired wave based on the correlation of.

Then, based on the detection result by the interference direction detecting means, the tuning frequency shifting means sets the tuning frequency of the FM receiving device in the opposite direction to the direction in which the adjacent interference exists.
That is, in the case of the upper disturbance in which the frequency of the adjacent disturbance is higher than the frequency of the desired wave, the tuning frequency becomes smaller, and in the case of the lower disturbance in which the frequency of the adjacent disturbance is smaller than the frequency of the desired wave. Shifts the tuning frequency by a predetermined frequency in the direction of increasing the tuning frequency to remove adjacent interference.

As described above, according to the first invention,
Adjacent interference is removed by detecting the direction in which the adjacent interference is occurring and shifting the tuning frequency in the direction opposite to the direction in which the adjacent interference is occurring.
It is not necessary to provide many IF filters, the product cost can be kept low, and there is no possibility that the sound quality will change due to the switching of the IF filters.

In order to achieve the above object, in the FM receiver according to the second invention, in addition to the configuration of the first invention, the jamming direction detecting means multiplies the FM detection output by the S meter output. The first comparison means includes a multiplication means and a first comparison means for comparing an output of the multiplication means with a predetermined first upper reference value and first lower reference value.
When the output from the multiplication means is larger than the first upper reference value, a signal indicating an upper side interference in which the frequency of the adjacent interference wave is larger than the frequency of the desired wave is output, and the output of the multiplication means is larger than the first lower reference value. Is smaller than the frequency of the desired wave, the signal indicating the lower side interference is output.

In the FM receiver according to the second aspect of the present invention, the jamming direction detecting means has a predetermined first upper reference preset by the first comparing means for the multiplication output of the FM detection output from the multiplying means and the S meter output. Value and the first lower reference value.

Then, the first comparing means outputs the multiplication output as the first
When the frequency is higher than the upper reference value, the adjacent interference wave frequency is higher than the desired wave frequency.
When the frequency is smaller than the first lower reference value, the frequency of the adjacent interference wave is smaller than the frequency of the desired wave, and a signal indicating lower interference is output, and the tuning frequency shift means changes the adjacent interference direction from the first comparing means. Based on the signal shown, the tuning frequency of the FM receiver is shifted in the direction opposite to the direction in which adjacent interference is present.

As described above, according to the second invention,
Unlike the conventional case, it is not necessary to provide many IF filters, and the product cost can be kept low.
There is no fear that the sound quality will change due to the switching of the F filter.

In order to achieve the above object, in the FM receiver according to the third invention, in addition to the configuration of the first invention, the disturbance direction detecting means is preset with the value of the DC component of the FM detection output. And a second comparing means for comparing with a predetermined second upper reference value and a second lower reference value. When the second comparing means has a value of the DC component of the FM detection output is larger than the second upper reference value. When the frequency of the adjacent interference wave is higher than the frequency of the desired wave, the signal indicating the upper interference is output, and when the value of the DC component of the FM detection output is smaller than the second lower reference value, the frequency of the adjacent interference wave is higher than that of the desired wave. It is characterized by outputting a signal indicating lower side interference smaller than the frequency.

In the FM receiving apparatus according to the third aspect of the present invention, the interference direction detecting means sets the value of the DC component of the FM detection output to the second value.
The comparison means compares with a predetermined second upper reference value and second lower reference value set in advance.

Then, the second comparing means outputs a signal indicating the upper side interference in which the frequency of the adjacent interference wave is larger than the frequency of the desired wave when the value of the DC component is larger than the second upper reference value, and the second comparison means outputs the signal. When the frequency is smaller than the lower reference value, the frequency of the adjacent interference wave is lower than the frequency of the desired wave, and a signal indicating the lower interference is output, and the tuning frequency shift means outputs the signal indicating the adjacent interference direction from the second comparing means. Based on the above, the tuning frequency of the FM receiver is shifted in the direction opposite to the direction in which the adjacent disturbance exists.

As described above, according to the third invention,
Unlike the conventional case, it is not necessary to provide many IF filters, and the product cost can be kept low.
There is no fear that the sound quality will change due to the switching of the F filter.

In order to achieve the above object, in the FM receiver according to the fourth invention, in addition to the configuration of the first invention, the jamming direction detecting means multiplies the FM detection output by the S meter output. The output of the multiplication means is compared with predetermined first upper reference value and first lower reference value, and when the output of the multiplication means is larger than the first upper reference value, the frequency of the adjacent interference wave is the desired wave. Output a signal indicating an upper side interference larger than the frequency of the above, and output a signal indicating a lower side interference in which the frequency of the adjacent interference wave is smaller than the frequency of the desired wave when the output of the multiplication means is smaller than the first lower reference value. And comparing the value of the DC component of the FM detection output with a predetermined second upper reference value and second lower reference value, and the value of the DC component of the FM detection output is the second value. When it is larger than the upper reference value, When the frequency of the wave is higher than the frequency of the desired wave, the signal indicating the upper disturbance is output, and when the value of the DC component of the FM detection output is smaller than the second lower reference value, the frequency of the adjacent disturbance is higher than the frequency of the desired wave. The second comparing means for outputting a signal indicating the lower side interference, and the signals from the first comparing means and the second comparing means are input, and the signals from the second comparing means are input. And a control means for outputting the signal from the second comparing means with priority over the signal from the first comparing means.

In the FM receiver according to the fourth aspect of the present invention, the interference direction detecting means has a predetermined first upper reference preset by the first comparing means for the multiplication output of the FM detection output from the multiplying means and the S meter output. Value and the first lower reference value, and further compares the value of the DC component of the FM detection output with a predetermined second upper reference value and second lower reference value preset by the second comparing means.

Then, from the first comparing means and the second comparing means to the control means, respectively, a signal indicating the upper disturbance in which the frequency of the adjacent interference wave is higher than the frequency of the desired wave or the frequency of the adjacent interference wave is the frequency of the desired wave. A signal indicating a lower disturbance that is less than is output.

When the signals are input from both the first comparison means and the second comparison means, the control means outputs the signal from the second comparison means with priority over the signal from the first comparison means, and performs tuning. The frequency shift means shifts the tuning frequency of the FM receiver in the direction opposite to the direction in which the adjacent interference exists based on the signal indicating the adjacent interference direction from the second comparing means.

As described above, according to the fourth invention,
Unlike the conventional case, it is not necessary to provide many IF filters, and the product cost can be kept low.
There is no possibility that the sound quality will change due to the switching of the F filter, and the adjacent interference directions are detected by the first comparison means and the second comparison means, respectively, so that the adjacent interference directions can be accurately detected. .

In order to achieve the above-mentioned object, an FM receiver according to a fifth aspect of the present invention is, in addition to the configuration of the first aspect of the present invention, detects a multipath of a reception wave and detects a detection signal indicating the level of the detected multipath. To the interference direction detecting means,
It is characterized in that it further comprises a multipath detecting means for controlling the interference direction detecting sensitivity of the interference direction detecting means.

In the FM receiver according to the fifth aspect of the present invention, the multipath detecting means detects the level of the multipath superposed on the received wave, and detects the detection signal indicating the detected level of the multipath in the jamming direction. Output to the means.

The disturbing direction detecting means adjusts the detecting sensitivity in the disturbing direction in accordance with the level of the multipath indicated by the detection signal from the multipath detecting means. Specifically, when the detected multipath level is high, the detection sensitivity in the disturbing direction is lowered, and when the detected multipath level is low, the disturbing direction detection sensitivity is increased.

As described above, according to the fifth aspect of the present invention, when detecting the adjacent interference direction, it is possible to prevent erroneous detection due to the multipath noise superimposed on the received wave, and to detect the accurate adjacent interference direction. Detection can be performed.

In order to achieve the above object, in the FM receiver according to the sixth invention, in addition to the configuration of the fifth invention, the jamming direction detecting means multiplies the FM detection output by the S meter output. The output of the multiplication circuit is compared with predetermined first upper reference value and first lower reference value, and when the output of the multiplication circuit is larger than the first upper reference value, the frequency of the adjacent interference wave is the desired wave. Output a signal indicating an upper side interference greater than the frequency of, and a signal indicating a lower side interference in which the frequency of the adjacent interference wave is smaller than the frequency of the desired wave when the output of the multiplication circuit is smaller than the first lower reference value. And a first upper reference value and a first lower reference value of the first comparing means are set corresponding to the detection signal of the multipath detecting means.

In the FM receiver according to the sixth aspect of the present invention, the jamming direction detecting means has a predetermined first upper reference preset by the first comparing means for the multiplication output of the FM detection output from the multiplying means and the S meter output. And the first lower reference value, and the first comparing means outputs a signal indicating an upper disturbance in which the frequency of the adjacent disturbance wave is larger than the frequency of the desired wave when the multiplication output is larger than the first upper reference value. However, when the frequency of the adjacent interference wave is smaller than the frequency of the desired wave when the frequency is smaller than the first lower reference value, the tuning frequency shift means outputs the signal indicating the lower interference, and the tuning frequency shift means outputs the signal from the first comparison means. The tuning frequency of the FM receiver is shifted in the direction opposite to the direction in which the adjacent disturbance exists based on the signal indicating the disturbance direction.

At this time, by the multipath detecting means,
The level of the multipath superimposed on the received wave is detected, and when the multipath is detected, a detection signal indicating the level of the multipath is output to the disturbing direction detecting means, and the first upper reference of the first comparing means. The value and the first lower reference value are set corresponding to the level of the multipath indicated by the detection signal.

Specifically, when the level of the detected multipath is high, the absolute values of the first upper reference value and the first lower reference value of the first comparing means are increased to lower the detection sensitivity in the disturbing direction, When the level of the detected multipath is low, the absolute value of the first upper reference value and the first lower reference value of the first comparing means is reduced to increase the detection sensitivity in the disturbing direction.

As described above, according to the sixth aspect of the present invention, when the adjacent interference direction is detected, it is possible to prevent erroneous detection due to the multipath noise superimposed on the received wave, and to accurately detect the adjacent interference direction. Detection can be performed.

In order to achieve the above object, in the FM receiver according to the seventh invention, in addition to the configuration of the fifth invention, the jamming direction detecting means presets the value of the DC component of the FM detection output. The predetermined second upper reference value and the second
Compared to the lower reference value, when the value of the DC component of the FM detection output is larger than the second upper reference value, the signal indicating the upper disturbance in which the frequency of the adjacent interference wave is higher than the frequency of the desired wave is output, The second comparison means is provided, which outputs a signal indicating a lower side interference in which the frequency of the adjacent interference wave is smaller than the frequency of the desired wave when the value of the DC component of the detection output is smaller than the second lower reference value. The second upper reference value and the second lower reference value of the comparing means are set corresponding to the detection signal of the multipath detecting means.

In the FM receiver according to the seventh aspect of the present invention, the interference direction detecting means sets the value of the DC component of the FM detection output to the second value.
The second comparing means compares the predetermined second upper reference value and the second lower reference value preset by the comparing means, and the second comparing means sets D
When the value of the C component is greater than the second upper reference value, the signal indicating the upper disturbance in which the frequency of the adjacent interference wave is greater than the frequency of the desired wave is output, and when the value of the C component is less than the second lower reference value, the adjacent interference wave is output. Outputs a signal indicating the lower side interference whose frequency is lower than the frequency of the desired wave, and the tuning frequency shift means outputs F from the second comparing means based on the signal indicating the adjacent disturbance direction.
The tuning frequency of the M receiver is shifted in the direction opposite to the direction in which adjacent interference is present.

At this time, the multipath detecting means
The level of the multipath superimposed on the received wave is detected, and when the multipath is detected, a detection signal indicating the level of the multipath is output to the disturbing direction detecting means, and the second upper reference of the second comparing means. The value and the second lower reference value are set corresponding to the level of the multipath indicated by the detection signal.

Specifically, when the level of the detected multipath is high, the absolute value of the second upper reference value and the second lower reference value of the second comparing means is increased to lower the detection sensitivity in the disturbing direction, When the level of the detected multipath is low, the absolute value of the second upper reference value and the second lower reference value of the second comparing means is reduced to increase the detection sensitivity in the interference direction.

As described above, according to the seventh aspect of the present invention, when the adjacent interference directions are detected, it is possible to prevent erroneous detection due to the multipath noise superimposed on the received wave, and to accurately detect the adjacent interference directions. Detection can be performed.

In order to achieve the above object, in the FM receiver according to the eighth invention, in addition to the configuration of the fifth invention, the jamming direction detecting means multiplies the FM detection output by the S meter output. The output of the multiplication circuit is compared with predetermined first upper reference value and first lower reference value, and when the output of the multiplication circuit is larger than the first upper reference value, the frequency of the adjacent interference wave is the desired wave. Output a signal indicating an upper side interference greater than the frequency of, and a signal indicating a lower side interference in which the frequency of the adjacent interference wave is smaller than the frequency of the desired wave when the output of the multiplication circuit is smaller than the first lower reference value. And comparing the value of the DC component of the FM detection output with a predetermined second upper reference value and second lower reference value, and the value of the DC component of the FM detection output is the second value. When it is larger than the upper reference value, When the frequency of the wave is higher than the frequency of the desired wave, the signal indicating the upper disturbance is output, and when the value of the DC component of the FM detection output is smaller than the second lower reference value, the frequency of the adjacent disturbance is higher than the frequency of the desired wave. The second comparing means for outputting a signal indicating the lower side interference, and the signals from the first comparing means and the second comparing means are input, and the signals from the second comparing means are input. Control means for outputting the signal from the second comparing means prior to the signal from the first comparing means, the first upper reference value, the first lower reference value and the second comparison of the first comparing means. The second upper reference value and the second lower reference value of the means are set corresponding to the detection signals of the multipath detecting means, respectively.

In the FM receiver according to the eighth aspect of the present invention, the jamming direction detecting means has a predetermined first upper reference preset by the first comparing means for the multiplication output of the FM detection output from the multiplying means and the S meter output. Value and the first lower reference value, and further compares the value of the DC component of the FM detection output with a predetermined second upper reference value and second lower reference value preset by the second comparing means.

Then, from the first comparing means and the second comparing means to the control means, the signal indicating the upper disturbance in which the frequency of the adjacent interfering wave is higher than the frequency of the desired wave or the frequency of the adjacent interfering wave is the frequency of the desired wave, respectively. A signal indicating a lower disturbance that is less than is output.

When the signals are input from both the first comparison means and the second comparison means, the control means outputs the signal from the second comparison means prior to the signal from the first comparison means, and performs tuning. The frequency shift means shifts the tuning frequency of the FM receiver in the direction opposite to the direction in which the adjacent interference exists based on the signal indicating the adjacent interference direction from the second comparing means.

At this time, the multipath detecting means
The level of the multipath superimposed on the received wave is detected, and when the multipath is detected, a detection signal indicating the level of the multipath is output to the disturbing direction detecting means, and the first upper reference of the first comparing means. The value, the first lower reference value, and the second upper reference value and the second lower reference value of the second comparing means are set corresponding to the level of the multipath indicated by the detection signal.

Specifically, when the detected multipath level is high, the first upper reference value of the first comparing means, the first upper reference value,
The absolute values of the lower reference value and the second upper reference value and the second lower reference value of the second comparing means are increased to lower the detection sensitivity in the jamming direction, respectively, and when the detected multipath level is low, The absolute values of the first upper reference value and the first lower reference value of the first comparison means and the second upper reference value and the second lower reference value of the second comparison means are reduced to increase the detection sensitivity in the interference direction.

As described above, according to the eighth aspect of the invention, since the adjacent interference directions are detected by the first comparing means and the second comparing means, it is possible to accurately detect the adjacent interference directions. When detecting the adjacent interference direction, erroneous detection due to the multipath noise superimposed on the received wave is prevented, and the adjacent interference direction can be detected more accurately.

In order to achieve the above-mentioned object, an FM receiver according to a ninth aspect of the present invention is, in addition to the configuration of the first aspect, the DC component of the FM detection output generated when the tuning frequency is shifted by the tuning frequency shifting means. It is characterized by further comprising first offset detection means for detecting an offset amount and correcting an offset of a DC component of the FM detection output input to the adjacent interference detection means.

In the FM receiver according to the ninth aspect of the present invention, the D of the FM detection output produced when the tuning frequency shift means shifts the tuning frequency by the first offset detection means.
The offset amount of the C component is detected.

Then, D of the detected FM detection output
Based on the offset amount of the C component, the offset of the DC component due to the shift of the tuning frequency generated in the FM detection output input to the adjacent interference detecting means is corrected.

As described above, according to the ninth invention,
By correcting the offset of the DC component generated in the FM detection output along with the shift of the tuning frequency, it is possible to prevent erroneous detection due to the shift of the DC center that occurs during fine adjustment of the tuning frequency.

In order to achieve the above object, in the FM receiver according to the tenth invention, in addition to the configuration of the first invention, the jamming direction detecting means presets the value of the DC component of the FM detection output. Compared with the predetermined second upper reference value and second lower reference value, when the value of the DC component of the FM detection output is larger than the second upper reference value, the frequency of the adjacent interfering wave is higher than the frequency of the desired wave. A signal indicating the upper side interference, and when the value of the DC component of the FM detection output is smaller than the second lower reference value, the signal indicating the lower side interference in which the frequency of the adjacent disturbance wave is smaller than the frequency of the desired wave is output. The second comparison means for outputting is provided, and the offset amount of the DC component of the FM detection output generated when the tuning frequency shift means shifts the tuning frequency is detected, and the detected DC component of the FM detection output is turned off. In response to Tsu bets amount is characterized in that it further comprises a second offset detecting means for correcting the second upper reference value and a second lower reference value of the second comparison means.

The FM receiver according to the tenth invention is
The disturbance direction detecting means compares the value of the DC component of the FM detection output with a predetermined second upper reference value and second lower reference value preset by the second comparing means, and the second comparing means,
When the value of the DC component is larger than the second upper reference value, the signal indicating the upper disturbance in which the frequency of the adjacent interference wave is higher than the frequency of the desired wave is output, and when the value of the DC component is smaller than the second lower reference value, the adjacent interference wave is output. Outputs a signal indicating lower side interference whose frequency is lower than the frequency of the desired wave, and the tuning frequency shift means makes the tuning frequencies of the FM receivers adjacent to each other based on the signal indicating the adjacent interference direction from the second comparing means. Shift in the opposite direction of the interference.

At this time, the offset amount of the DC component of the FM detection output generated when the tuning frequency is shifted by the tuning frequency shifting means is detected by the second offset detecting means. Then, the second upper reference value and the second lower reference value of the second comparing means are corrected corresponding to the detected offset amount of the DC component of the FM detection output.

As described above, according to the tenth aspect of the invention, the reference value for detecting the adjacent interference direction is detected corresponding to the offset of the DC component generated in the FM detection output due to the shift of the tuning frequency. By performing the correction, it is possible to prevent the occurrence of erroneous detection due to the shift of the DC center that occurs when the tuning frequency is finely adjusted.

[0051]

BEST MODE FOR CARRYING OUT THE INVENTION The most preferred embodiment of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a block diagram showing an example of an embodiment of an FM receiver according to the present invention. In FIG. 1, a desired wave (RF signal) generated by amplifying a broadcast wave received by an antenna circuit (not shown) by a high frequency amplifier circuit is input to a mixer 10.

Then, in the mixer 10, the RF signal is mixed with the local oscillation signal input from the local oscillation circuit 11, converted into an intermediate frequency (IF) signal, and further amplified by the IF amplification circuit 12. . Next, the IF signal is input to the limiter circuit 13 to be generated as an FM signal having a constant amplitude, and then FM detection is performed by the FM detection circuit 14, and the FM detection output a is output to a stereo demodulation circuit (not shown) and Stereo reproduction through the de-emphasis and low-frequency amplification circuit. The above configuration is similar to that of the conventional FM receiving apparatus.

In addition to the above configuration, this FM receiver further includes an AM detection circuit 15 for AM detection of the IF signal before being input to the limiter circuit 13, and this AM detection circuit 1.
The AM detection output (S meter output) b from 5 and the FM detection output a from the FM detection circuit 14 are input to detect the interference direction for detecting whether the frequency of the adjacent interference wave is higher or lower than the frequency of the desired wave. Circuit 16 and this interference direction detection circuit 16
And a microcomputer 17 for controlling the frequency of the local oscillation signal output from the local oscillation circuit 11 by outputting the tuning frequency data signal c to the local oscillation circuit 11 based on the detection signal from the local oscillation circuit 11.

FIG. 2 is a block diagram showing the configuration of the interference direction detection circuit 16. In FIG. 2, the jamming direction detection circuit 16 includes an HPF 16A to which the AM detection output b output from the AM detection circuit 15 is input, and the HPF 16A.
And the comparator 16B which receives the AM detection output b that has passed through and detects the beat cycle of the AM detection output b,
The HPF 16C to which the FM detection output a output from the M detection circuit 14 is input, and the FM that has passed through this HPF 16C
Detection output a and A detected by the comparator 16B
The AC of FM detection output a depending on the beat cycle of M detection output b
Sampling of components (FM detection output a and AM detection output b
16D for performing the multiplication), the LPF 16E to which the sampling output from the sampling circuit 16D is input, and the multiplication output that has passed through the LPF 16E are input, and the multiplication output is preset to an upper reference value and a lower reference. A first window comparator 16F that outputs a HI signal or an LO signal in comparison with a value, and an LPF1 to which the FM detection output a from the FM detection circuit 14 is input
6G and the FM detection output a that has passed through this LPF 16G are input, and the DC component of this FM detection output a is compared with preset upper and lower reference values and a HI signal or LO signal is output. Window comparator 1
6H and the HI signal or the LO signal from the first window comparator 16F and the second window comparator 16H, respectively, and the H from the first window comparator 16F or the second window comparator 16H.
The control circuit 16I outputs the I signal or the LO signal to the microcomputer 17.

Next, the operation of detecting the direction of adjacent interference in the interference direction detecting circuit 16 will be described. Here, before describing the operation of the interference direction detection circuit 16, first, the characteristics of the FM detection output a will be described.

FIGS. 3 and 4 show the frequency fluctuations of the FM detection output a and the AM detection output b, respectively, by plotting the ratio (D / U ratio) of the desired wave and the interfering wave with time by simulation. 3 is a graph shown in FIG. 3, in which the frequency of the adjacent disturbance wave is higher than the frequency of the desired wave (+200 kHz) (hereinafter referred to as upper disturbance), and FIG. The frequency variation is shown when the frequency is lower than the frequency of the desired wave (-200 kHz) (hereinafter, referred to as lower interference).

From FIGS. 3 and 4, it can be seen that when adjacent interference occurs, beat components due to the interference occur in both the FM detection output a and the AM detection output b. Furthermore, it can be seen that the following characteristics appear due to the adjacent disturbance. That is, (1) when the adjacent interfering wave is weaker than the desired wave (D / U ratio is negative), a) when the upper interfering wave (FIG. 3), the beat component of the FM detection output a and the beat component of the AM detection output b When the components are in phase with each other and b) the lower side interference (Fig. 4), the beat component of the FM detection output a and the beat component of the AM detection output b are in opposite phase to each other, and (2) the adjacent disturbance wave is more than the desired wave. Is also strong (the D / U ratio is positive), c) The DC of the FM detection output a when the upper disturbance (Fig. 3) is present.
Is deviated in the positive direction by the detuning frequency of the interfering wave, and d) the lower side interfering wave (Fig. 4), the DC of the FM detection output a
Is shifted in the negative direction by the detuning frequency of the interfering wave. The jamming direction detection circuit 16 uses the FM detection output a as described above.
In the case where the adjacent interfering wave in (1) above is weaker than the desired wave (D / U ratio is negative), the
The window comparator 16F detects the disturbing direction, and the adjacent disturbing wave in (2) above is stronger than the desired wave (D
In the case where the / U ratio is positive), the interference direction is detected by the second window comparator 16H.

That is, the jamming direction detection circuit 16 uses the FM
In the sampling circuit 16D, the AC component of the detection output a that has passed through the HPF 16C is sampled at the beat cycle obtained from the comparator 16B to which the AM detection output b that has passed through the HPF 16A is input (the FM detection output a and the AM detection output b are Multiply).

Next, the DC component of the multiplication output of the sampling circuit 16D that has passed through the LPF 16E is input to the first window comparator 16F. Then, in the first window comparator 16F, the DC component value of the multiplication output is compared with the preset upper reference value and lower reference value. Here, this first window comparator 1
The upper reference value and the lower reference value set to 6F are the upper limit value and the lower limit value of the DC component value of the multiplication output for determining whether to shift the tuning frequency described later when there is adjacent interference. Is shown.

As described above, in the case of the upper side interference (interference wave frequency> desired wave frequency), the beat outputs of the FM detection output a and the AM detection output b are in phase with each other in the multiplication output from the sampling circuit 16D. Therefore, it is positive, and in the case of lower side interference (interfering wave frequency <desired wave frequency), the phases are opposite to each other and therefore is negative.

Therefore, the first window comparator 16F
In the comparison in i), if the DC component value> the upper reference value, the HI signal indicating that the multiplication output from the sampling circuit 16D is positive and the adjacent disturbance is larger than the set upper reference value is sent to the control circuit 16I. Ii) When the DC component value <lower reference value, the LO signal indicating that the multiplication output from the sampling circuit 16D is negative and adjacent interference is smaller than the set lower reference value is output to the control circuit 16I. Iii) When lower reference value <DC component value <upper reference value, no signal is output to the control circuit 16I.

The control circuit 16I receives the HI signal from the first window comparator 16F,
It is determined that the adjacent disturbance is the upper disturbance and the tuning frequency needs to be shifted. When the LO signal is input, it is determined that the adjacent disturbance is the upper disturbance and the tuning frequency needs to be shifted. To do. In addition, the interference direction detection circuit 16 is a DC that has passed through the LPF 16G of the FM detection output a.
Input the component to the second window comparator 16H,
The DC component value of the FM detection output a is compared with the preset upper reference value and lower reference value.

Here, the second window comparator 1
The upper reference value and the lower reference value set to 6H are the upper limits of the offset amounts of the DC components of the FM detection output a for determining whether to shift the tuning frequency described later when there is adjacent interference. And the lower limit value.

As described above, the DC component of the FM detection output a is the upper disturbance (interference wave frequency> desired wave frequency).
In the case of, it shifts in the positive direction, and in the case of lower side interference (interference wave frequency <desired wave frequency), it shifts in the negative direction.

Therefore, the second window comparator 16H
Iv) When the DC component value> the upper reference value, the DC component is shifted in the positive direction and the HI signal indicating that the adjacent disturbance is larger than the set upper reference value is output to the control circuit 16I. V) When the DC component value <lower reference value, the DC component is shifted in the negative direction, and the LO signal indicating that the adjacent disturbance is smaller than the set lower reference value is output to the control circuit 16I, vi) When the lower reference value <DC component value <upper reference value, no signal is output to the control circuit 16I. When the HI signal is input from the second window comparator 16H, the control circuit 16I determines that the adjacent interference is the upper interference and the tuning frequency needs to be shifted. When the LO signal is input, the control circuit 16I determines that the adjacent interference is the upper interference. , It is judged that the adjacent disturbance is the upper disturbance and it is necessary to shift the tuning frequency.

Then, the control circuit 16I includes a first window comparator 16F and a second window comparator 16H.
When both the HI signal and the LO signal are input from the first window comparator 16H, the signal from the second window comparator 16H is prioritized to determine the disturbing direction. When no signal is input from the second window comparator 16H, the first window comparator 16H is input. Judgment of the disturbing direction is made based on the signal from 16F.

Then, the control circuit 16I includes the second window comparator 16H or the first window comparator 1
When it is determined by the HI signal from 6F that the adjacent interference is the upper interference and it is necessary to shift the tuning frequency, the interference detection output HI signal is output to the microcomputer 17.

Further, the control circuit 16I includes the second window comparator 16H or the first window comparator 16H.
When the LO signal from F determines that the adjacent interference is the lower interference and the tuning frequency needs to be shifted, the interference detection output LO signal is output to the microcomputer 17.

Then, the microcomputer 17 outputs to the local oscillation circuit 11 based on the interference detection output HI signal and LO signal input from the control circuit 16I, and outputs the local oscillation signal from the local oscillation circuit 11 to the mixer 10. A tuning frequency data (DC voltage) signal c for shifting the tuning frequency (local oscillation frequency) of the oscillation signal in the direction opposite to the direction in which adjacent interference is generated is output.

That is, when the interference detection output HI signal is input from the interference direction detection circuit 16 to the microcomputer 17, the adjacent interference is the upper interference and is large enough to be removed. The tuning frequency data signal c for shifting the tuning frequency of the local oscillation signal output from the VOC to the mixer 10 in the direction of decreasing is output to the PLL of the local oscillation circuit 11.

On the contrary, when the disturbance detection output LO signal is input to the microcomputer 17 from the disturbance direction detection circuit 16, the adjacent disturbance is the lower disturbance and is large enough to be removed. Reference numeral 17 outputs a tuning frequency data signal c to the PLL of the local oscillation circuit 11, which shifts the tuning frequency of the local oscillation signal output from the VOC to the mixer 10 in the increasing direction.

The width of the tuning frequency of the local oscillation signal shifted by the tuning frequency data signal c can be set in advance to an arbitrary value, but normally, it is set to be smaller than the frequency shift width in the seek function of the FM receiver. Is set to.

As described above, when the adjacent interference occurs, the shift of the tuning frequency in the direction opposite to the direction in which the adjacent interference occurs in the mixer 10 is repeated until the adjacent interference disappears.

FIG. 5 is a block diagram showing another example of the embodiment of the FM receiver according to the present invention. This F of FIG.
In the M receiver, the multipath detection circuit 20 is connected to the jamming direction detection circuit 16 of the FM receiver of FIG. 1, and the multipath detection circuit 20 outputs the AM detection output b from the AM detection circuit 15. A part of it is designed to be input.

The multipath detection circuit 20 detects the multipath level based on the level of the AM component detected from the IF signal by the AM detection circuit 15, and outputs the detection sensitivity adjustment signal d corresponding to the detected multipath level. Output to the jamming direction detection circuit 16.

Then, the interference direction detection circuit 16 reduces the detection sensitivity in the adjacent interference direction based on the detection sensitivity adjustment signal d input from the multipath detection circuit 20.
That is, the disturbance direction detection circuit 16 detects the detection sensitivity adjustment signal d.
The absolute value of the upper reference value and the lower reference value of each of the first window comparator 16F and the second window comparator 16H is increased according to the level of the multipath indicated by. This prevents malfunction due to multipath noise.

FIGS. 6 and 7 are block diagrams showing another example of the embodiment of the FM receiving apparatus according to the present invention. The FM receivers of FIGS. 6 and 7 are the same as the FM receiver of FIG.
In addition to the configuration of the receiving device, an IF counter 30 is further provided.

This IF counter 30 includes an FM detection circuit 1
4 receives a part of the FM detection output a and detects the DC center offset amount (IF frequency offset amount) generated when the tuning frequency is shifted in the mixer 10 from the FM detection output a.

The FM receiver shown in FIG. 6 receives the FM detection output a inputted to the interference direction detection circuit 16 by the amount of the DC center offset detected by the IF counter 30.
Is an offset.

Further, the FM receiver of FIG. 7 corresponds to the amount of the DC center offset detected by the IF counter 30, and the upper reference value and the lower reference value in the second window comparator 16H of the disturbance direction detection circuit 16. Is to correct.

In any case, the jamming direction is detected by offsetting the FM detection output a, which is the object of the direction detection of the adjacent interference, to correct the deviation of the DC center of the FM detection output a due to the fine tuning of the tuning frequency. The first window comparator 16F and the second window comparator 1 of the circuit 16
6H can be normally compared to prevent erroneous detection due to the deviation of the DC center that occurs when the tuning frequency is finely adjusted.

FIGS. 8 and 9 are block diagrams showing still another example of the embodiment of the FM receiving apparatus according to the present invention. Each of the FM receivers of FIGS. 8 and 9 includes an offset detection circuit 40 in addition to the configuration of the FM receiver of FIG.

The offset detection circuit 40 receives a part of the tuning frequency data signal c output from the microcomputer 17 to the local oscillation circuit 11, and shifts the tuning frequency in the mixer 10 from the tuning frequency data signal c. DC center offset (IF
The amount of frequency shift) is calculated.

The FM receiver shown in FIG. 8 has the FM amount before the input to the interference direction detecting circuit 16 by the amount of the DC center offset calculated by the offset detecting circuit 40.
An offset is applied to the detection output a.

Further, the FM receiver of FIG. 9 sets the upper and lower reference values in the second window comparator 16H of the jamming direction detection circuit 16 in correspondence with the amount of DC center offset calculated by the offset detection circuit 40. To correct.

In any case, the jamming direction is detected by offsetting the FM detection output a which is the object of the direction detection of the adjacent interference to correct the deviation of the DC center of the FM detection output a due to the fine tuning of the tuning frequency. The first window comparator 16F and the second window comparator 1 of the circuit 16
6H is allowed to perform a normal comparison operation to prevent erroneous detection due to the deviation of the DC center that occurs when the tuning frequency is finely adjusted.

[Brief description of drawings]

FIG. 1 is a block diagram showing an example of an embodiment of the present invention.

FIG. 2 is a block diagram showing a configuration of a disturbance direction detection circuit in the same example.

FIG. 3 is a graph showing frequency fluctuations of an FM detection output and an AM detection output in an FM receiver at the time of upper side interference.

FIG. 4 is a graph showing frequency fluctuations of an FM detection output and an AM detection output in the FM receiver at the time of lower side interference.

FIG. 5 is a block diagram showing another example of the embodiment of the present invention.

FIG. 6 is a block diagram showing still another example of the embodiment of the present invention.

FIG. 7 is a block diagram showing still another example of the embodiment of the present invention.

FIG. 8 is a block diagram showing still another example of the embodiment of the present invention.

FIG. 9 is a block diagram showing still another example of the embodiment of the present invention.

FIG. 10 is a block diagram showing a conventional example.

[Description of Reference Signs] 10 ... Mixer 11 ... Local oscillation circuit (tuning frequency shift means) 12 ... IF amplifier circuit 13 ... Limiter circuit 14 ... FM detection circuit 15 ... AM detection circuit 16 ... Interference direction detection circuit (interference direction detection means) 16A ... HPF 16B ... Comparator 16C ... HPF 16D ... Sampling circuit (multiplier) 16E ... LPF 16F ... Window comparator (first comparing means) 16G ... LPF 16H ... Window comparator (second comparing means) 16I ... Control circuit (control) Means) 17 Microcomputer (tuning frequency shifting means) 20 Multipath detecting circuit (multipath detecting means) 30 IF counter (first offset detecting means) 40 Offset detecting circuit (second offset detecting means) a FM Detection output b ... AM detection output (S meter output) c ... Tuning frequency data signal d ... Detection sensitivity adjustment signal

Continuation of the front page (56) Reference JP-A-2-194736 (JP, A) JP-A-5-276062 (JP, A) JP-A-6-29878 (JP, A) JP-A-53-134315 (JP , A) Japanese Unexamined Patent Publication No. 4-307807 (JP, A) Actual development Sho 53-29225 (JP, U) Actual development Sho 52-37415 (JP, U) (58) Fields investigated (Int.Cl. ⁷ , DB) Name) H04B 1/10 H04B 1/26

Claims (10)

(57) [Claims] 1. Whether the frequency of an adjacent interfering wave is higher or lower than the frequency of a desired wave based on the correlation between the FM detection output output from the FM detection circuit and the S meter output output from the AM detection circuit. And a tuning frequency shift means for shifting the tuning frequency in the direction opposite to the direction in which the adjacent disturbance exists based on the disturbance direction detection signal output from the disturbance direction detection means. An FM receiver characterized by: 2. The disturbing direction detecting means multiplies the FM detection output by the S meter output, and a predetermined first upper reference value and first lower reference which are preset for the output of the multiplying means. A first comparing means for comparing with a value, the first comparing means, when the output from the multiplying means is larger than a first upper reference value, the upper disturbance in which the frequency of the adjacent disturbance wave is higher than the frequency of the desired wave. The signal indicating the lower side interference in which the frequency of the adjacent interference wave is smaller than the frequency of the desired wave is output when the output of the multiplication means is smaller than the first lower reference value. FM receiver. 3. The disturbance direction detecting means comprises second comparing means for comparing the value of the DC component of the FM detection output with a predetermined second upper reference value and second lower reference value. When the value of the DC component of the FM detection output is larger than the second upper reference value, the second comparison means outputs a signal indicating upper side interference in which the frequency of the adjacent interference wave is higher than the frequency of the desired wave, and the FM detection output The FM receiver according to claim 1, wherein when the value of the DC component is smaller than the second lower reference value, a signal indicating lower side interference in which the frequency of the adjacent disturbance wave is smaller than the frequency of the desired wave is output. 4. The disturbing direction detecting means compares the output of a multiplying means for multiplying the FM detection output and the S meter output with a predetermined first upper reference value and first lower reference value. , When the output of the multiplication means is larger than the first upper reference value, a signal indicating an upper side interference in which the frequency of the adjacent interference wave is higher than the frequency of the desired wave is output, and the output of the multiplication means is higher than the first lower reference value. First comparing means for outputting a signal indicating lower interference in which the frequency of the adjacent interference wave is smaller than the frequency of the desired wave when the frequency is small, and a predetermined second upper value in which the value of the DC component of the FM detection output is preset. Compared to the reference value and the second lower reference value,
When the value of the DC component of the FM detection output is larger than the second upper reference value, a signal indicating the upper side interference in which the frequency of the adjacent interference wave is larger than the frequency of the desired wave is output, and the DC of the FM detection output is output.
Second comparing means for outputting a signal indicating lower interference in which the frequency of the adjacent interference wave is smaller than the frequency of the desired wave when the value of the component is smaller than the second lower reference value; and the first comparing means and the second comparing means. Control means for inputting the signal from the comparing means and outputting the signal from the second comparing means prior to the signal from the first comparing means when the signal from the second comparing means is input. The FM receiver according to claim 1, further comprising: 5. Multipath detection for detecting multipaths of received waves and outputting a detection signal indicating the level of the detected multipaths to the jamming direction detecting means to control the jamming direction detecting sensitivity of the jamming direction detecting means. The FM receiver according to claim 1, further comprising means. 6. The disturbing direction detecting means compares the output of a multiplication circuit that multiplies the FM detection output and the S meter output with predetermined first upper reference value and first lower reference value. , When the output of the multiplication circuit is larger than the first upper reference value, the signal indicating the upper interference in which the frequency of the adjacent interference wave is larger than the frequency of the desired wave is output, and the output of the multiplication circuit is larger than the first lower reference value. When the frequency of the adjacent interference wave is smaller than the frequency of the desired wave when the frequency is small, the first comparison means for outputting a signal indicating the lower interference is provided, and the first upper reference value and the first lower reference value of the first comparison means are provided. The FM receiver according to claim 5, wherein the FM receiver is set in correspondence with a detection signal of the multipath detecting means. 7. The disturbance direction detecting means sets a predetermined second value of a DC component of the FM detection output.
Compared with the upper reference value and the second lower reference value, when the value of the DC component of the FM detection output is larger than the second upper reference value, the frequency of the adjacent interference wave is higher than the frequency of the desired wave. Second comparing means for outputting a signal and outputting a signal indicating a lower side interference in which the frequency of the adjacent interference wave is smaller than the frequency of the desired wave when the value of the DC component of the FM detection output is smaller than the second lower reference value. The FM receiver according to claim 5, further comprising: a second upper reference value and a second lower reference value of the second comparing means, which are set in correspondence with a detection signal of the multipath detecting means. 8. The disturbing direction detecting means compares the output of a multiplication circuit for multiplying the FM detection output and the S meter output with a predetermined first upper reference value and first lower reference value. , When the output of the multiplication circuit is larger than the first upper reference value, the signal indicating the upper interference in which the frequency of the adjacent interference wave is larger than the frequency of the desired wave is output, and the output of the multiplication circuit is larger than the first lower reference value. First comparing means for outputting a signal indicating lower interference in which the frequency of the adjacent interference wave is smaller than the frequency of the desired wave when the frequency is small, and a predetermined second upper value in which the value of the DC component of the FM detection output is preset. Compared to the reference value and the second lower reference value,
When the value of the DC component of the FM detection output is larger than the second upper reference value, a signal indicating the upper side interference in which the frequency of the adjacent interference wave is larger than the frequency of the desired wave is output, and the DC of the FM detection output is output.
Second comparing means for outputting a signal indicating lower interference in which the frequency of the adjacent interference wave is smaller than the frequency of the desired wave when the value of the component is smaller than the second lower reference value; and the first comparing means and the second comparing means. Control means for inputting the signal from the comparing means and outputting the signal from the second comparing means prior to the signal from the first comparing means when the signal from the second comparing means is input. And a first upper reference value and a first lower reference value of the first comparing means and a second upper reference value and a second lower reference value of the second comparing means are respectively detected signals of the multipath detecting means. The FM receiver according to claim 5, which is set correspondingly. 9. The offset amount of the DC component of the FM detection output, which is generated when the tuning frequency shift unit shifts the tuning frequency, is detected to correct the offset of the DC component of the FM detection output input to the adjacent interference detection unit. First to do
The FM receiver according to claim 1, further comprising offset detection means. 10. The DC component of the FM detection output, wherein the disturbing direction detecting means compares the value of the DC component of the FM detection output with a predetermined second upper reference value and second lower reference value. When the value of is greater than the second upper reference value, the signal indicating the upper disturbance in which the frequency of the adjacent interference wave is greater than the frequency of the desired wave is output, and the value of the DC component of the FM detection output is greater than the second lower reference value. And a second comparing means for outputting a signal indicating a lower side interference in which the frequency of the adjacent interference wave is smaller than the frequency of the desired wave, and FM detection generated when the tuning frequency shift means shifts the tuning frequency. A second step of detecting an offset amount of the DC component of the output and correcting the second upper reference value and the second lower reference value of the second comparing means in accordance with the detected DC component offset amount of the FM detection output. Oh Further comprising a set detecting means, FM receiver according to claim 1.