JPH05145498A - Am multiplex signal receiver - Google Patents

Abstract

(57) [Abstract] [PROBLEMS] To provide an AM multiplex signal receiving apparatus capable of avoiding interference in medium-wave AM broadcasting, enabling good voice reception, and digitally receiving information other than voice. A frequency converter 102 for converting an RF signal into an IF signal, an envelope detector 104 for demodulating the IF signal to obtain an audio signal 1, a digital demodulator 106 for reproducing a digital audio signal from the IF signal, and a demodulator One of the audio signal 1 output from the envelope detector 104 and the audio signal 2 output from the digital audio signal decoding circuit 108, which reproduces the analog audio signal 2 from the generated digital audio signal. Signal switch 110 for selecting the audio signal 1 and the audio signal 1
And an error correction syndrome output from the digital demodulator 106 to compare the respective sound qualities and generate a sound quality evaluation circuit 112 that generates a control signal for switching the signal switch 110.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for receiving a broadcast AM multiplex signal by multiplexing a digital signal with an AM broadcast.

SUMMARY OF THE INVENTION The present invention relates to an AM multiplex broadcasting receiver that multiplexes and broadcasts a conventional AM broadcasting digital signal, and demodulates the AM signal when the digital audio signal is not multiplexed. However, when the digital audio signal is multiplexed, both the AM signal and the digital audio signal are demodulated, and the one with the better reception quality is automatically selected, and the digital audio signal is received even in the area where the interference is bad and the quality of the AM signal is poor. It is possible to reproduce a good-quality audio signal by demodulating.

In addition, when additional information such as data is multiplexed by a digital signal and is broadcast, A
It has both a function of demodulating an M signal and a function of demodulating a digital signal, and is capable of reproducing a digital multiplex signal different from the AM audio signal.

[0004]

2. Description of the Related Art Conventionally, AM broadcasting using medium waves has been used for radio broadcasting and the like. In recent years, the medium wave A
M stereo broadcasting has also been put to practical use.

By the way, in the medium-wave AM broadcasting, there is a problem of interference, and particularly in a region where radio waves are congested such as Europe, it is in a state of interference that cannot be practically used. Moreover, even in Japan, it is a fact that interference is troubled especially at night when radio waves reach a long distance.

[0006]

As described above, although the interference is a serious listening problem in the current medium-wave AM broadcasting, receivers having countermeasures against interference are not well known.

The present invention has been made in view of the above circumstances, and an object of the present invention is to avoid interference in medium-wave AM broadcasting, enable good voice reception, and digitally receive information other than voice. An object is to provide an AM multiplex signal receiving device.

[0008]

In order to achieve the above object, the present invention provides a means for receiving an AM multiplex signal transmitted by multiplexing a digital audio signal with an AM audio signal, and a method for receiving the AM multiplex signal. From the extracted analog voice signal and digital voice signal, and means for selecting and outputting the one of the extracted analog voice signal and digital voice signal having a better voice quality. To do.

Further, in order to achieve the above object, another invention is a means for receiving an AM multiplexed signal transmitted by multiplexing a digital data signal with an AM voice signal, and a received A signal.
A means for extracting an analog voice signal and a digital data signal from the M multiplexed signal is provided.

[0010]

In the present invention, the analog broadcast signal and the same digital voice signal as the analog broadcast signal are multiplexed on the AM broadcast wave, and the analog broadcast signal and the digital broadcast signal are extracted from the AM multiplexed signal, Both signals are evaluated and the one with better quality is output as a voice signal.

In another aspect of the invention, an analog broadcast signal and a digital data signal are multiplexed on an AM broadcast wave, and the analog voice signal and the digital data signal are extracted from the AM multiplexed signal. The digital data signal is various information signals other than voice and can be displayed.

[0012]

1 is a block diagram showing the configuration of an embodiment of an AM multiplex signal receiving apparatus according to the present invention.

The receiver shown in the drawing is a tuning circuit 100 for selecting an RF signal of a desired frequency from the received RF signals.
A frequency converter 102 for converting the selected RF signal into an IF signal, an envelope detector 104 for demodulating the IF signal to obtain an audio signal 1, and a digital demodulator 106 for reproducing a digital audio signal from the IF signal. , A digital audio signal decoding circuit 108 for reproducing an analog audio signal 2 from the demodulated digital audio signal, an audio signal 1 output from the envelope detector 104, and an audio signal 2 output from the digital audio signal decoding circuit 108. A signal switcher 110 for selecting one of them, the audio signal 1, and an error correction syndrome output from the digital demodulator 106 are input and the respective sound qualities are compared to switch the signal switcher 110. And a sound quality evaluation circuit 112 for generating the control signal.

The sound quality evaluation circuit 112 includes a bandpass filter (BPF) unit 200 for extracting the high frequency component (noise component) of the envelope detection output (voice signal 1) from the envelope detector 104, and the level of the extracted noise component. Noise level detection unit 202, an error rate measurement unit 204 that measures an error rate from the error correction syndrome from the digital demodulator 106, and the noise level detection unit 20.
2 is compared with the output of the error rate detection unit 204 to generate a control signal for selecting a signal with better sound quality and output it to the signal switcher 110.
It has and. Next, the operation of this embodiment will be described.

The received AM broadcast signal (RF signal) is supplied to the tuning circuit 100, and the tuning circuit 100 selects a signal of a desired frequency from the RF signal. The selection signal is converted into an IF signal by the frequency converter 102. This IF signal is then sent to the envelope detector 1
The envelope detection is performed by 04 to obtain the audio signal 1,
It is supplied to the signal switch 110 and the sound quality evaluation circuit 112.
Further, the IF signal is supplied to the digital demodulator 108, and the multiplexed digital signal component is demodulated.
Further, the error correction syndrome in the digital signal demodulated by the digital demodulator 106 is supplied to the error rate measuring unit 204 of the sound quality evaluation circuit 112.

The sound quality evaluation circuit 112 evaluates the sound quality in the following manner, generates a control signal, and outputs it to the signal switch 110.

The audio band of AM broadcasting is 7.5 kHz, but when AM multiplex broadcasting is broadcast, the band of AM audio signals is narrowed to about 5 kHz, for example.
Therefore, there is no audio signal in the band from 5 kHz to 7.5 kHz, which is noise. This noise is transferred to the BPF unit 2
00, and the noise level detecting section 202 detects this noise level to evaluate the quality of the AM voice signal equivalently. In addition, the error rate measuring unit 204 obtains a bit error rate or a block error rate from the supplied error correction syndrome and equivalently evaluates the quality of the digital voice signal. The evaluation signals of the noise level detecting unit 202 and the error detecting unit 204 are compared by the level comparing unit 206, and a control signal for reproducing the voice signal of higher quality is output to the signal switch 110.

The operation of the level comparing section 206 will be described in more detail. As shown in FIG. 2, the noise level and the bit error rate and the subjective voice evaluation have a relationship that the subjective evaluation value decreases as the noise level increases. Similarly, if the bit error rate increases, the subjective evaluation value decreases. The evaluation value is low. Therefore, the outputs of the noise level detection unit 202 and the error measurement unit 204 are compared, and the one with the larger subjective evaluation value is selected as the audio signal. However, since the noise level and the bit error rate change from moment to moment, hysteresis is provided in order to switch the voice signals so that they do not disturb the ears. In this hysteresis, for example, the difference between the subjective evaluation values is set to 0.5 or 1.0. The control signal generated in this way is the signal switch 11
When it is supplied to 0, the signal switcher 110 selects one of the audio signal 1 and the audio signal 2 having a better quality and outputs it as an audio signal.

Although the present embodiment has been described with respect to the example of receiving the audio signal multiplexed with the AM broadcast signal, the present invention is not limited to this, and the reception of the data signal such as the character data multiplexed with the AM broadcast signal is received. Can also be applied to. In this case, as shown in FIG. 3, at the same time as reproducing the AM voice signal detected by the envelope detector 104, the digital signal such as character data demodulated by the digital demodulator 106 is reproduced and displayed on the display. You can Further, in this case, if the digital voice signal and the data signal are distinguished from each other, they can be received by the circuit configuration similar to that of FIG.

[0020]

As described above, according to the present invention, even if the quality of an AM voice signal is poor due to interference, the quality of the multiplexed voice signal of the same content is digitally modulated and reproduced. You can get a good voice signal. It is also possible to receive various data signals carried on digital signals.

[Brief description of drawings]

FIG. 1 is a block diagram showing the configuration of an embodiment of an AM multiplex signal receiving apparatus according to the present invention.

FIG. 2 is an explanatory diagram showing a relationship between a noise level and a bit error rate and a subjective voice evaluation.

FIG. 3 is a block diagram showing the configuration of another embodiment of the AM multiplex signal receiving apparatus according to the present invention.

[Explanation of symbols]

 100 Tuning circuit 102 Frequency converter 104 Envelope detector 106 Digital demodulator 108 Digital voice signal decoding circuit 110 Signal switcher 112 Sound quality evaluation circuit 200 Bandpass filter section 202 Noise level detection section 204 Error rate measurement section 206 Level comparison section

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shigeki Moriyama 1-10-11 Kinuta, Setagaya-ku, Tokyo Inside the Japan Broadcasting Corporation Broadcasting Technology Laboratory (72) Inventor Tomohiro Saito 1-10-11 Kinuta, Setagaya-ku, Tokyo (72) Inventor, Satoshi Yamada 1-10-11 Kinuta, Setagaya-ku, Tokyo Inside Broadcasting Technology Institute, Japan Broadcasting Corporation

Claims (2)

[Claims] 1. A unit for receiving an AM multiplex signal transmitted by multiplexing a digital voice signal with an AM voice signal, and a unit for extracting an analog voice signal and a digital voice signal from the received AM multiplex signal. An AM multiplex signal receiving device, comprising: a unit for selecting and outputting a signal having a better voice quality from the extracted analog voice signal and digital voice signal. 2. A means for receiving an AM multiplex signal transmitted by multiplexing a digital data signal with an AM voice signal, and a means for extracting an analog voice signal and a digital data signal from the received AM multiplex signal. An AM multiplex signal receiving apparatus comprising: