JP2001060849A - Broadcasting receiver - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a broadcasting receiver which reliably starts to search for other broadcasting stations even while the level of a composite signal is lowered in a weak electric field and even in a weak electric field. SOLUTION: Multi-path noise and weak electric field noise including adjacent interference noise are added, a direct current output on the basis of the added value is outputted from an adder 11, a controller 12 calculates the average value of direct current outputs outputted from the adder 11 and the instantaneous value of the direct current output from the adder 11 in each prescribed period, when the average value is equal to or more than 1st threshold, AF search which automatically switches to the broadcasting reception of another broadcasting station is allowed, and in the case the instantaneous value after allowing the AF search is equal to or more than 2nd threshold in a weak electric field, the AF search is started. Meanwhile, at the time of intense electric field strength, when the instantaneous value after allowing the AF search is equal to or more than 3rd threshold being larger than the 2nd threshold, the AF search is started.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a broadcast receiver, and more particularly, to a broadcast receiver which automatically switches to broadcast reception of another broadcast station when the reception condition deteriorates during broadcast reception.

[0002]

2. Description of the Related Art A conventional on-vehicle FM broadcast receiver, for example, RD
In an S broadcast receiver, an AF that automatically switches to broadcast reception of another broadcast station when the reception state is deteriorated due to a decrease in reception electric field strength or adjacent interference during traveling after receiving a broadcast or multipath noise is increased. A search is performed.

In such an RDS broadcast receiver, the multipath noise is detected based on the level of an AC component around, for example, about 19 kHz which is superimposed on the S-meter output voltage output from the intermediate frequency amplification stage. Weak electric field noise including adjacent interference noise is detected based on the level of an AC component, for example, around 100 kHz included in the composite signal output from the FM detection stage.

The levels of these detected AC components are converted into DC voltages, and both DC voltages are added, and the added DC voltage (hereinafter also referred to as an added DC voltage) is controlled by a computer-controlled RDS broadcast receiver. A / D in equipment
It is supplied to a port and used as a trigger signal for AF search. In such an RDS broadcast receiver, an AF search permission instruction is issued when the average value of the added DC voltage is equal to or higher than a threshold value a (V), and 10 seconds after the AF search permission.
The added DC voltage is checked every ms, and when the instantaneous value is equal to or greater than a threshold value b (a <b) (V), the AF search is started as an AF search start instruction.

[0005]

However, in the above-mentioned conventional FM broadcast receiver, the threshold value a (V) for instructing other broadcast station search permission is set low, and the threshold value a
(V) is also a threshold value b for instructing another broadcast station to start searching.
(V) was also constant regardless of the received electric field strength.

However, in FM broadcast receivers, so-called soft mute, which reduces the level of a composite signal with a weak electric field, is operated in order to reduce the annoying noise feeling with a weak electric field. For this soft mute operation,
The AC component (10
(Around 0 kHz), and the input terminal of the A / D port of the control device in the FM broadcast receiver satisfies the average value of the added DC voltage ≧ threshold a (V).
There is a problem that the instantaneous value of the added DC voltage checked every ms does not reach the threshold value b (V), and the search for another broadcast station is not started when the electric field is weak.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a broadcast receiver capable of surely starting a search for another broadcast station even when the level of a composite signal is reduced due to a weak electric field.

[0008]

According to a first aspect of the present invention, there is provided a broadcast receiver, comprising: detecting means for detecting adjacent interference noise and / or weak electric field noise; Determining means for determining medium and strong electric field strength;
First and second threshold values for the output from the detection means are predetermined, and when the output value of the detection means is equal to or more than the first threshold value when the received electric field strength is weak electric field strength, a search for another broadcast station is performed. And a control unit for starting a search for another broadcast station when the output value of the detection unit is equal to or more than a second threshold when the reception electric field strength is medium or strong.

According to the broadcast receiver of the first aspect of the present invention, when the discrimination means determines that the received electric field strength is weak electric field strength, the adjacent interference noise and / or the weak electric field noise detected by the detection means are reduced. A search for another broadcast station is started when the value is equal to or greater than the first threshold value, and when the received electric field strength is determined to be medium or strong by the determining means, the adjacent interference noise and / or the weak electric field detected by the detecting means are detected. When the noise is greater than or equal to the second threshold, a search for another broadcast station is started. At this time, even when the level of the composite signal is reduced by the weak electric field due to the setting of the first threshold value and the second threshold value, the search for another broadcast station can be reliably started even at the time of the weak electric field.

According to a second aspect of the present invention, there is provided a broadcast receiver, comprising: detecting means for detecting adjacent interference noise and / or weak electric field noise; weak electric field strength by detecting a received electric field strength;
Determining means for determining the strong electric field strength; obtaining an average value of the DC output output from the detecting means; and obtaining an instantaneous value of the output from the detecting means for each predetermined period, and determining a predetermined value for the average value. 1 is predetermined, predetermined second and third thresholds for the instantaneous value are predetermined, and when the average value is equal to or more than the first threshold, search for another broadcast station is permitted, and the reception electric field strength is low. When the electric field strength is higher, the search for the other broadcast station is started when the instantaneous value after permitting the search for the other broadcast station is equal to or more than a second threshold value. Control means for starting a search for another broadcast station when the instantaneous value after permitting the search for a station is equal to or greater than a third threshold value.

According to the broadcast receiver of the second aspect of the present invention, when the received electric field intensity is judged to be weak electric field intensity by the judgment means, the adjacent interference noise and / or the weak electric field noise detected by the detection means are detected. When the average value is equal to or greater than the first threshold, the search for another broadcast station is permitted, and the instantaneous value of the adjacent interference noise and / or the weak electric field noise detected by the detection unit after the search for the other broadcast station is permitted is obtained. When the number is equal to or larger than the second threshold, a search for another broadcast station is started. On the other hand, when the received electric field strength is
When it is determined that the electric field strength is strong, a search for another broadcast station is permitted when the average value is equal to or greater than a first threshold value, and the instantaneous value after permitting the search for the other broadcast station is equal to or greater than a third threshold value. Sometimes a search for another broadcast station is started. At this time, even when the level of the composite signal is reduced by the weak electric field due to the setting of the second threshold value and the third threshold value, the search for another broadcasting station can be reliably started even at the time of the weak electric field.

According to a third aspect of the present invention, there is provided a broadcast receiver, comprising: detecting means for detecting adjacent interference noise and / or weak electric field noise;
Determining means for determining the strong electric field strength; obtaining an average value of the DC output output from the detecting means; and obtaining an instantaneous value of the output from the detecting means for each predetermined period, and determining a predetermined value for the average value. 1, a predetermined second threshold value for the instantaneous value and a predetermined third threshold value larger than the second threshold value are determined in advance, and when the average value is equal to or greater than the first threshold value, the other broadcast station is determined. The search of the other broadcast station is started when the instantaneous value after permitting the search of the other broadcast station is greater than or equal to the second threshold when the received electric field strength is weak electric field strength. And medium control means for starting a search for another broadcast station when the instantaneous value after permitting the search for the other broadcast station is higher than or equal to a third threshold value at the time of strong electric field strength.

According to the broadcast receiver of the third aspect of the present invention, when the received electric field intensity is judged to be weak electric field intensity by the judging means, the adjacent interference noise and / or the weak electric field noise detected by the detecting means are detected. When the average value is equal to or greater than the first threshold, the search for another broadcast station is permitted, and the instantaneous value of the adjacent interference noise and / or the weak electric field noise detected by the detection unit after the search for the other broadcast station is permitted is obtained. When the number is equal to or larger than the second threshold, a search for another broadcast station is started. On the other hand, when the received electric field strength is
When it is determined that the electric field strength is strong, a search for another broadcast station is permitted when the average value is equal to or greater than a first threshold value, and the instantaneous value after permitting the search for the other broadcast station is equal to or greater than a third threshold value. Sometimes a search for another broadcast station is started. At this time, since the second threshold is set to a value smaller than the third threshold, even when the level of the composite signal is reduced due to the weak electric field, the search for another broadcasting station can be started reliably even in the weak electric field. Can be.

According to a fourth aspect of the present invention, there is provided a broadcast receiver comprising: first detection means for detecting multipath noise; second detection means for detecting adjacent interference noise and / or weak electric field noise; And an adding means for adding a detection output from the second detection means and sending out a DC output based on the addition result; a discriminating means for detecting a received electric field strength to discriminate a weak electric field strength and a medium or strong electric field strength; Calculating the average value of the DC output output from the adding means, obtaining the instantaneous value of the output from the adding means at predetermined intervals, determining a predetermined first threshold value for the average value in advance, and determining a predetermined value for the instantaneous value. Is determined in advance, and a predetermined third threshold larger than the second threshold is predetermined for the instantaneous value. When the average value is equal to or larger than the first threshold, a search for another broadcast station is performed. Allow,
When the received electric field strength is weak electric field strength, the search for the other broadcast station is started when the instantaneous value after permitting the search for the other broadcast station is equal to or more than a second threshold, and the received electric field is medium.
A control means is provided for starting a search for another broadcast station when the instantaneous value after permitting the search for the other broadcast station is higher than or equal to a third threshold value at the time of strong electric field strength.

According to the broadcast receiver of the present invention, the detected multipath noise is added to the detected adjacent interference noise and / or the weak electric field noise, and the DC output based on the added value is added. The average value of the DC output output from the adding means and the DC output output from the adding means is obtained, and the instantaneous value of the DC output from the adding means for each predetermined period is obtained. When the average value is equal to or more than the first threshold, When the search for the broadcast station is permitted, the search for the other broadcast station is started when the instantaneous value after the search permission for the other broadcast station is greater than or equal to the second threshold value when the electric field strength is weak, and when the medium electric field strength is high. When the instantaneous value after the search permission of the other broadcast station is equal to or more than the third threshold, the search for the other broadcast station is started.

According to the fourth aspect of the present invention, since the third threshold is set to a value larger than the second threshold, the level of the composite signal is reduced by the weak electric field. However, even in the case of a weak electric field, the search for another broadcast station is started without fail.

Further, in the broadcast receiver according to any one of claims 2 to 4 of the present invention, a fourth threshold value is further predetermined with respect to the average value, and when the received electric field intensity is weak electric field intensity, the average value is determined. Control for permitting the search for another broadcast station when the value is equal to or greater than the first threshold, and for allowing the search for another broadcast station when the average value is equal to or greater than the fourth threshold when the received electric field strength is medium or strong. Means may be provided.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a broadcast receiver according to the present invention will be described with reference to embodiments.

FIG. 1 is a block diagram showing a configuration of a main part of a broadcast receiver according to an embodiment of the present invention. The case of an RDS broadcast receiver of a radio data multiplex broadcasting system will be described as an example.

In the broadcast receiver according to one embodiment of the present invention, the output from the antenna 1 is supplied to the front end 2, and the reception signal selected in the front end 2 is converted into an intermediate frequency signal and output. . Front end 2
The intermediate frequency signal converted in the above is supplied to and amplified by an intermediate frequency amplification stage 3 having necessary bandwidth characteristics and selectivity characteristics, and the output from the intermediate frequency amplification stage 3 is sent to an FM detection stage 40 and subjected to FM detection. , FM detection output are sent to a stereo demodulator 6 where they are stereo-demodulated.

Here, the FM detection stage 40 attenuates the level of the composite signal which is the FM detection output when the received electric field strength detected by the FM detector 4 for performing the FM detection of the intermediate frequency signal and the S meter output described later is a weak electric field. An attenuator 5 is included.

The S-meter output voltage based on the received electric field intensity detected by the electric field intensity detection circuit (not shown) provided in the intermediate frequency amplification stage 3 is supplied to the band-pass filter 7 and is superposed on the S-meter output voltage. Come for example 19k
An AC component around Hz is detected as multipath noise by the bandpass filter 7, detected by the detector 8, converted into a DC voltage, and output.

The composite signal output from the FM detection stage 40 is supplied to the band-pass filter 9, and an AC component, for example, near 100 kHz, which is superimposed on the composite signal, is detected by the band-pass filter 9 as weak electric field noise. Detected by the detector 10, converted into a DC voltage and output. Here, 1
The reason why the AC component around 00 kHz is detected is to detect adjacent interference noise.

The DC voltage output from the detector 8 and the DC voltage output from the detector 9 are added in an adder 11. The output from the adder 11 is the sum of the multipath noise and the weak electric field noise, and is hereinafter also referred to as an added DC voltage.

On the other hand, the S-meter output voltage detected by the electric field intensity detection circuit is supplied to a comparator (not shown) to provide a reference value of 0 dBμ (a received electric field intensity of 0d).
The value based on the electric field strength when the received electric field strength detected by the electric field strength detection circuit is less than 0 dBμ and when the received electric field strength is 0 dBμ or more and when the received electric field strength is higher than 0 dBμ. Is converted.

The added DC voltage output from the adder 11 is supplied to an A / D port of the control device 12, and a signal based on the electric field strength is supplied to the control device 12.

The control device 12 basically includes a microcomputer, and the adder 1 supplied to the A / D port
An arithmetic circuit for obtaining an average value based on the added DC voltage from 1 and an instantaneous value based on the added DC voltage every 10 ms;
A threshold a1 (V) for the average value of the added DC voltage supplied to the D port and a threshold b1 for the instantaneous value of the added DC voltage supplied to the A / D port based on the electric field strength
(V) and a threshold table shown in FIG. 2 in which threshold values b2 (b2> b1) (V) are stored.

Here, the threshold value a1 (V) is, for example, 1.3 V
The threshold value b1 (V) is, for example, 1.8 V, and the threshold value b2
(V) is set to, for example, 2.9V. That is, the threshold value a1 (V) is set to the threshold value a1 (V) irrespective of the electric field intensity, and the threshold value b1 (V) and the threshold value b2 (V) are set when the reception electric field intensity is low, medium, and high. The threshold value is varied based on the electric field strength, and as described above, the threshold value b1 (V)
Is set low, and the threshold value b2 (V) is set high.

The controller 12 further sets a threshold value a when the input received electric field strength information indicates a weak electric field strength.
1 (V) and the threshold value b1 (V) are selected, and when the medium and high electric field strengths are indicated, the threshold value a1 (V) and the threshold value b2 (V) are selected. a1 (V) is compared with an average value based on the added DC voltage supplied to the A / D port. When the average value is equal to or more than the threshold value a1 (V), the AF search is permitted. When the AF search is permitted. When the input received electric field strength information indicates a weak electric field strength, the threshold b1 (V) is compared with the instantaneous value of the added DC voltage supplied to the A / D port every 10 ms,
When the instantaneous value is equal to or greater than the threshold value b1 (V), an AF search start instruction signal is sent to start the AF search. When the AF search is permitted, the input received electric field strength information is When the strength is indicated, the threshold value b2
(V) is compared with the instantaneous value of the added DC voltage supplied to the A / D port of the control device 12 every 10 ms. When the instantaneous value is equal to or more than the threshold value b2 (V), an AF search start instruction signal is transmitted. A search control circuit for starting an AF search by using a search function is provided.

In the above, the S-meter output voltage detected by the electric field intensity detection circuit is supplied to a comparator (not shown) and compared with a 0 dBμ reference value, and the received electric field intensity detected by the electric field intensity detection circuit is less than 0 dBμ. The case where the signal is converted to a signal based on the electric field strength at the time of the weak electric field strength and 0 dBμ or more and at the time of the strong electric field strength and then supplied to the control device 12 is shown. The device 12 may determine whether it is less than 0 dBμ or more.

The operation of the broadcast receiver according to the embodiment of the present invention configured as described above will be described based on the operation of the control device 12.

In the broadcast receiver according to the embodiment of the present invention configured as described above, a received signal is received by the front end 2, converted into an intermediate frequency signal, and output. The intermediate frequency signal output from the front end 2 is supplied to the intermediate frequency amplification stage 3, amplified after band limitation, output to the FM detection stage 40 and subjected to FM detection, and demodulated into a stereo signal by the stereo demodulator 6. Is done.

The S-meter output voltage is extracted from the electric field intensity detection circuit, is compared with the 0 dBμ reference value, and is converted into a binary signal based on the weak electric field intensity, the medium electric field intensity, and the strong electric field intensity, and is received by the control circuit 12. If the electric field is weak, medium,
It is determined whether it is a strong electric field.

On the other hand, the added DC voltage output from the adder 11 obtained by adding the DC voltage based on the multipath noise output from the detector 8 and the weak electric field noise output from the detector 10 is equal to the A / D port, the arithmetic circuit of the controller 12 calculates the average value of the added DC voltage, checks whether the calculated average value is equal to or more than the threshold value a1 (V), and calculates the average value of the added DC voltage. Threshold a1
(V) When it is determined that the value is equal to or more than the above, the AF search is permitted.

In this state, it is determined whether the received electric field strength detected based on the S meter output voltage is a weak electric field strength, a medium electric field strength, or a strong electric field intensity. When it is determined that the electric field strength is weak, the instantaneous value of the added DC voltage every 10 ms is equal to the threshold value b1.
(V) or more is checked, and the added DC voltage of 10
When the instantaneous value for each ms is determined to be equal to or more than the threshold value b1 (V), the AF search is started.

However, since the output voltage of the S-meter is low or almost non-existent when the electric field is weak, the level of the DC voltage based on the detected multipath noise output from the detector 8 is low and the noise is unpleasant. The composite signal is attenuated by the attenuator 5 in order to reduce the DC voltage, and the level of the DC voltage based on the weak electric field noise output from the detector 10 is reduced. As a result, even if the instantaneous value of the added DC voltage is low, since the threshold value b1 (V) is set to a low value, the added DC voltage becomes the threshold value b1 (V).
As described above, when the AF search is permitted, the AF search is started.

In the middle, when the electric field intensity is strong, the output voltage of the S-meter is high and saturates, so that multipath noise is not detected. The level of the DC voltage based on the detected multipath noise output from the detector 8 is Although it is low, the composite signal is not attenuated by the attenuator 5 in order to reduce harsh noise, and the level of the DC voltage output from the detector 10 is higher than in the case of the weak electric field strength, and When the instantaneous value of the voltage increases and the instantaneous value of the added DC voltage becomes equal to or higher than the threshold value b2 (V) and the AF search is permitted, the AF search is started.

As described above, according to the broadcast receiver according to the embodiment of the present invention, even when the level of the composite signal is lowered at the time of a weak electric field, other broadcast stations are surely caused by the weak electric field noise. The effect of starting the search is obtained, and the multipath noise and the adjacent interference noise at the time of medium and strong electric field strengths are reduced by AF as in the conventional case.
The effect that the search is started is obtained.

Although the broadcast receiver according to the embodiment of the present invention has been exemplified by an RDS broadcast receiver,
The present invention can be similarly applied to other broadcast station search by the auto tuning function in a broadcast receiver having the auto tuning function.

Further, only weak electric field noise may be detected without using multipath noise detection, or only weak electric field noise and adjacent interference noise may be detected. Further, the threshold value for the average value in the case of the weak electric field may be set smaller than the threshold value in the case of the medium and strong electric fields, and the threshold value of the average value may be changed together with the threshold value of the instantaneous value. Since the output levels of the respective detecting means are different due to differences in the gain and the like of the respective circuits and variations, the values of the instantaneous value thresholds b1 and b2 may be b1> b2.

[0041]

As described above, according to the broadcast receiver of the present invention, it is possible to obtain the effect of reliably starting the search for another broadcast station with weak electric field noise, and at the same time the noise at medium and high electric field strengths. For example (for example, due to adjacent interference), the effect of starting a search for another broadcast station is obtained as in the conventional case.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of a broadcast receiver according to an embodiment of the present invention.

FIG. 2 is a schematic diagram for explaining a table provided in the control device of the broadcast receiver according to the embodiment of the present invention;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Antenna 2 Front end 3 Intermediate frequency amplification stage 4 FM detector 5 Attenuator 6 Stereo demodulator 7 and 9 Bandpass filter 8 and 10 Detector 11 Adder 12 Control device 40 FM detection stage

Claims (5)

[Claims] A detecting means for detecting adjacent interference noise and / or a weak electric field noise; a detecting means for detecting a received electric field strength to discriminate a weak electric field strength, a medium electric field strength, and a strong electric field strength; The first and second threshold values for the output of the first and second broadcast stations are determined in advance, and when the output value of the detection means is equal to or more than the first threshold value when the received electric field intensity is weak electric field intensity, a search for another broadcast station is started. A broadcast receiver, comprising: control means for starting a search for another broadcast station when the output value of the detection means is equal to or more than a second threshold when the electric field strength is medium or strong. 2. Detection means for detecting adjacent interference noise and / or weak electric field noise; discrimination means for detecting a reception electric field strength to discriminate between a weak electric field strength and medium / strong electric field strength; Find the average value of the output DC output,
Calculating an instantaneous value of the output from the detection means for each predetermined period; determining a predetermined first threshold value for the average value; determining predetermined second and third threshold values for the instantaneous value; When the value is equal to or greater than the first threshold, search for another broadcast station is permitted, and when the received electric field strength is weak, the instantaneous value after permitting the search for the other broadcast station is equal to or greater than the second threshold. Starts a search for another broadcast station, and starts the search for another broadcast station when the instantaneous value after permitting the search for the other broadcast station is greater than or equal to a third threshold when the received electric field is medium or strong electric field strength. And a control unit for causing the broadcast receiver to perform the control. 3. Detection means for detecting adjacent interference noise and / or weak electric field noise; discrimination means for detecting received electric field strength to discriminate between weak electric field strength, medium and strong electric field strength; Find the average value of the output DC output,
And obtaining an instantaneous value of the output from the detection means for each predetermined period, predetermining a predetermined first threshold value for the average value, and a predetermined second threshold value for the instantaneous value and a predetermined value larger than the second threshold value. A third threshold value is predetermined, and when the average value is equal to or more than the first threshold value, search for another broadcast station is permitted. When the received electric field strength is weak, the search for the other broadcast station is permitted. When the instantaneous value is equal to or more than the second threshold, the search for another broadcast station is started. When the received electric field is medium and the electric field strength is strong, the instantaneous value after permitting the search for the other broadcast station is equal to the third threshold. A broadcast receiver provided with control means for starting a search for another broadcast station at the time described above. 4. A detection means for detecting multipath noise, a second detection means for detecting adjacent interference noise and / or a weak electric field noise, and a detection output from the first and second detection means. Adding means for sending out a DC output based on the addition result, detecting means for detecting the received electric field strength to determine the weak electric field strength, medium and strong electric field strength, and averaging the DC output outputted from the adding means. A value, and an instantaneous value of the output from the adding means for each predetermined period, a predetermined first threshold value for the average value is determined in advance,
A predetermined second threshold value for the instantaneous value is predetermined, and a predetermined third threshold value larger than the second threshold value is predetermined for the instantaneous value. When the average value is equal to or larger than the first threshold value, When the search of the broadcasting station is permitted, the search of the other broadcasting station is started when the instantaneous value after the permission of the search of the other broadcasting station is greater than or equal to the second threshold when the reception electric field strength is the weak electric field strength, When the electric field is medium and the electric field strength is strong, the instantaneous value after permitting the search for the other broadcast station is the third value.
Control means for starting a search for another broadcast station when the threshold value is equal to or greater than the threshold value. 5. The broadcast receiver according to claim 2, wherein a fourth threshold value is further predetermined with respect to the average value, and when the received electric field intensity is a weak electric field intensity, the average value is set to the fourth value. Control means is provided for permitting a search for another broadcast station when the average value is equal to or greater than a fourth threshold and permitting a search for another broadcast station when the received electric field strength is medium or strong. A broadcast receiver.