JPH04292021A - Signal interpolating system - Google Patents

Abstract

PURPOSE:To perfectly remove a multipath noise present in a received signal, and to obtain a regenerative signal not to cause an unpleasant feeling due to the above-mentioned removal at all. CONSTITUTION:This system is provided with a signal interpolating means 30 constituted of a detecting means 2 to detect an FM multipath noise in an FM received signal, a muting means 4 to mute temporarily a received audio signal, sound recording and reproducing parts 13 to 16 to record and reproduce successively the received audio signal, and a control part 12 to make the muting means 4 operate in response to the output of the detecting means 2, and interpolate the audio signal just before the corresponding muted part from the sound recording and reproducing parts 13 to 16 to the corresponding muted part of the temporarily muted signal.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention mutes the noise part when FM signal multipath noise is included in the received signal, and also adds a predetermined signal to the muted part. The present invention relates to a signal interpolation system in an FM receiver that interpolates.

0002

2. Description of the Related Art Conventionally, in FM receivers, a diversity reception system has been generally used as a means for removing FM signal multipath noise.

This diversity reception method combines FM signals received at two or more points by appropriate means, or switches and selects the most suitable one among the received FM signals. More reliable reception information can be obtained than when a single FM signal is received, and at this time, FM signal multipath noise can be eliminated.

0004

[Problem to be Solved by the Invention] However, even in this conventional diversity reception system, FM signal multipath noise may occur in each of the FM signals received at two or more points. Sometimes the smallest F
There is a problem in that only an FM signal containing M signal multipath noise is selected, and the FM signal multipath noise cannot be completely eliminated.

The present invention was devised to eliminate the above-mentioned problems, and when FM signal multipath noise is present in the received signal, it is possible to completely remove the FM signal multipath noise. Further, it is an object of the present invention to provide a signal interpolation system in an FM receiver that does not cause any discomfort in the reproduced signal even when the above-mentioned removal is performed.

[0006]

Means for Solving the Problems To achieve the above object, the present invention provides a detection means for detecting FM signal multipath noise in an FM received signal, and a detection means for temporarily muting the received audio signal. a recording and reproducing unit that sequentially records and reproduces the received audio signals; - signal interpolation means comprising a control section for interpolating the audio signal from the recording/reproducing section immediately before the silent section of the audio signal;

[0007]

[Operation] The FM signal received by the FM receiver is demodulated into an audio signal by the FM detection circuit, and this audio signal is supplied to the audio amplifier via a noise canceller circuit, a silencing circuit, an adder circuit, etc. and is emitted by a speaker or the like.

Further, a part of the audio signal obtained from the output of the noise canceler circuit is alternately supplied to two IC memories via an analog-to-digital conversion circuit,
They are temporarily stored there and then read out alternately. This read signal is supplied to an adder circuit via a digital-to-analog conversion circuit.

Furthermore, the multipath noise detection signal obtained from the output of the FM detection circuit is supplied to a microcomputer constituting a control section.

[0010] Now, if there is no FM signal multipath noise in the received signal, there is no multipath noise detection signal supplied to the microcomputer, so the silencing circuit and the digital-to-analog conversion circuit are not activated. F
As described above, the audio signal demodulated by the M detection circuit is supplied to the audio amplifier via the noise canceller circuit, the silencing circuit, the adder circuit, etc., and is outputted as it is through the speaker.

On the other hand, if FM signal multipath noise is present in the received signal, the multipath noise detection signal detected by the FM detection circuit is supplied to the microcomputer, and the microcomputer detects the soundless circuit at an appropriate timing. and operating the digital-to-analog conversion circuit. Therefore, the multipath noise part of the audio signal is muted by the muting circuit, and the adding circuit adds the muted part of the audio signal to the digital signal. - The audio signal immediately before the muted part of the audio signal supplied via the analog conversion circuit is interpolated, and the audio signal as a whole is free from multipath noise and has no audio interruption. You can get a video signal.

0012

[Embodiment] An embodiment of the present invention will be explained with reference to the drawings.

FIG. 1 is a block configuration diagram showing one embodiment of a signal interpolation system according to the present invention, and FIG. 2 shows signal waveforms of each part in the configuration diagram of the embodiment shown in FIG.

In the figure, 1 is an FM receiver front end, 2 is an FM detection circuit, 3 is a noise canceller, 4 is a silencing circuit (muting circuit), 5 is an addition circuit, and 6 is a stereo demodulation circuit (multiplex decoder), 7 is an audio amplifier, 8 is a speaker, 9 is a 100KHz high-pass filter, 10 is a detection circuit, 11 is a smoothing circuit, 1
2 is a microcomputer (microcomputer), 13 is an analog-digital conversion circuit, 14 is a first IC memory, 15
is a second IC memory, and 16 is a digital-to-analog conversion circuit. It constitutes a signal interpolation means 30.

The FM detection circuit 2 demodulates the FM signal supplied from the front end 1 and outputs it to the detection terminal 1.
7 to generate an audio signal, and control terminal 1
8 to generate an S meter output signal. The silencing circuit 4 is
Controlled by a silence drive signal from the microcomputer 12,
The audio signal from the noise canceller 3 is silenced only during the control period. The bandpass filter 9, the detection circuit 10, and the smoothing circuit 11 jointly process the S-meter output signal to generate a multipath noise detection signal. When the microcomputer 12 is supplied with the multipath noise detection signal, it generates a silence driving signal at appropriate timing and also generates various control signals for operating the digital-to-analog conversion circuit 16. The first and second IC memories 14 and 15 alternately store digital signals (audio data) from the analog-to-digital conversion circuit 13 at a constant cycle, and also store digital signals (audio data) alternately stored at the same cycle. audio data) is read out and supplied to the digital-to-analog conversion circuit 16. That is, while the first IC memory 14 is storing a digital signal (audio data), the second IC memory 15 is reading the digital signal (audio data), and the second IC memory 15 is reading the digital signal (audio data). 2 IC memory 15
When the first IC memory 14 is storing data, the first IC memory 14 is reading data. The digital-to-analog conversion circuit 16 becomes operational only when receiving various control signals from the microcomputer 12, and converts digital signals (audio data) read from the first or second IC memory 14, 15.
Converts and plays back audio signals. Conversion playback in this case involves reproducing a signal going in the reverse direction on the time axis from the playback start point (trigger point), or for a predetermined period of time (for example, 500 seconds) from the playback start point (trigger point).
The signal from before (m seconds) is played back in the forward direction on the time axis.

Next, the operation of this embodiment will be explained using the signal waveform diagram shown in FIG. Note that the following explanation is for a case where FM signal multipath noise or the like exists in the FM received signal.

When a desired FM signal is received by the FM receiver front end 1, the detection terminal 17 of the FM detection circuit 2 receives a multipath noise component 20 and a spike noise component, as shown in waveform (3) in FIG. 21 is output, and at the same time, the control terminal 18 receives the waveform ■ of FIG.
As shown in FIG. 2, an S meter output signal containing a multipath noise component 20 is output. Of these, the pulsed spike noise component 21 of the audio signal is removed by a noise canceller, and the audio signal becomes silent, containing only the multipath noise component 20, as shown in waveform (2) in FIG. is supplied to the conversion circuit 4. On the other hand, the S meter output signal is filtered by a 100KHz high-pass filter 9 to remove unnecessary DC components and low frequency components.
The envelope of the multipath noise component 20 is detected by the detection circuit 10, and the waveform ■ of FIG.
As shown in FIG. 2 , the multipath noise detection signal from which the ripple component 22 has been removed is converted to a multipath noise detection signal and is supplied to the microcomputer 12 .

When the multipath noise detection signal is input to the microcomputer 12, as shown in waveform (3) in FIG. The silencing circuit 4 supplies the silencing drive signal with a duration of
In the audio signal shown by the waveform (■) in FIG.
As shown in the waveform (2) in FIG. 2, the output is an audio signal that is muted during the supply period of the multipath noise component 20, and is supplied to the adder circuit 5.

In addition, although signal waveforms are not particularly shown, the microcomputer 12 sends various control signals for operating the digital-to-analog conversion circuit 16 when the multipath noise detection signal is input. Generally, these various control signals have a generation timing that is substantially the same as the supply timing of the detection signal and a duration that is substantially the same as the supply period of the detection signal.

By the way, the audio signal shown in waveform (3) in FIG. One IC memory 14 (15
) and is temporarily stored there. At this time,
The other IC memory 15 (1
The digital signal (audio data) read from 4) is sequentially supplied to the digital-to-analog conversion circuit 16, and since the digital-to-analog conversion circuit 16 becomes operational at the time when this signal is supplied, As shown in waveform (■) in FIG. 2, an audio signal is sent from the conversion circuit 16,
This signal is supplied to the adder circuit 5.

In this case, the adder circuit 5 supplies and adds the audio signal shown in the waveform (2) of FIG. Therefore, the output of the adder circuit 5 is a seemingly continuous audio signal as shown in waveform (2) in FIG. (Multiplex decoder) 6 separates the signals of both channels, and then these signals are amplified to the desired output signal level by audio amplifier 7 and output from speaker 8, multipath It is possible to reproduce an audio signal that does not contain any noise components 20 or the like.

The above explanation is about the operation when FM signal multipath noise etc. is present in the FM received signal, but if FM signal multipath noise is not present in the FM received signal, the S mail Since the multipath noise component 20 does not exist in the data output signal and there is no multipath noise detection signal supplied to the microcomputer 12, the silencing circuit 4
does not perform a silencing operation, and the digital-to-analog conversion circuit 16 also does not operate, so the audio signal demodulated by the FM detection circuit 2 is sent to the noise canceller circuit 3, the silencing circuit 4, and the adder circuit. The signal is supplied to the audio amplifier 7 via the 5th line, etc., and then outputted by the speaker 8 as it is.

In this embodiment, when adding the interpolated audio signal to the muted portion of the muted audio signal, the muted audio signal and the interpolated audio signal are added to the muted portion of the muted audio signal. - A slight phase or amplitude difference may occur between the audio signal and the audio signal, and the phase or amplitude of the added audio signal may jump momentarily, but such a jump in phase or amplitude is extremely Since it is only an instantaneous phenomenon, it does not cause any discomfort to the listener.

As described above, according to this embodiment, the entire reproduced audio signal does not contain multipath noise, and moreover, it is possible to obtain the signal without any audio interruption. .

Next, FIG. 3 is a block diagram showing another embodiment of the signal interpolation system of the present invention.

In contrast to the above-described embodiment, the stereo demodulation circuit (multiplex decoder) 6 is arranged after the signal interpolation means 30, and the signal interpolation process is performed before stereo demodulation. Therefore, in this embodiment, a stereo demodulation circuit (multiplex decoder) 6 is arranged before the signal interpolation means 30, and the signal interpolation process is performed on each of the left and right channel signals that have undergone stereo demodulation. Although there is a difference in the configuration in some respects, the rest of the configuration is the same as that of the previous embodiment. In this embodiment, the same components as those in the previous embodiment are given the same reference numerals, and explanations for these components will be omitted.

To explain the operation of this embodiment, in the above embodiment, the output audio signal of the FM detection circuit 2 is
In contrast, the silencing circuit 4 performs silencing processing on the audio signal, and the signal interpolation processing is performed by supplying an interpolation signal from the signal interpolation means 30 to the silencing portion of the audio signal. Therefore, in this embodiment, the output audio signal of the FM detection circuit 2 is first separated into a right channel signal and a left channel signal in a stereo demodulation circuit (multiplex decoder) 6, and these separated signals are separated into a right channel signal and a left channel signal. Except for the fact that each audio signal is subjected to the above-mentioned silencing process and signal interpolation process, all other operations are the same as those of the previous embodiment.

In the above-mentioned embodiment, since the audio signal on which the signal interpolation process is being performed is a composite signal containing a stereo pilot signal, the audio signal to be muted during the signal interpolation process is If no consideration is given to the phase and frequency amplitude characteristics of the signal and the audio signal interpolated thereto, the separation of the left and right channel audio signals may deteriorate. Therefore, in the embodiment described above, the signal interpolating means 3
Regarding the configuration of 0, it is necessary to pay some design consideration to the above points.

However, in this embodiment, since the audio signal on which the signal interpolation processing is being performed is the demodulated left and right channel audio signal, the audio signal to be silenced and the audio signal interpolated thereto are There is no need to consider the phase and frequency amplitude characteristics of the audio signal, and the signal interpolation means 30 with a simple configuration can be used.

In this embodiment, this signal interpolation means 30
However, since the signal interpolation means 30 used in this embodiment has relatively narrow band frequency characteristics and does not have a phase correction circuit, it is sufficient to use an inexpensive analog-to-digital conversion circuit. 13 and the digital-to-analog conversion circuit 16 can be used. Furthermore, in the inexpensive audio signal analog-to-digital conversion circuit 13, digital-to-analog conversion circuit 16, and IC memories 14 and 15 used in the signal interpolation means 30 of this embodiment, Since most of the types have built-in signals for two channels, even if the signal interpolation means 30 for two channels is provided, the cost will not be high, and on the contrary, the cost will often be low.

[0031]

[Effects of the Invention] As explained above, according to the present invention,
When FM signal multipath noise exists in the received signal, the multipath noise detection signal detected by the FM detection circuit 2 is supplied to the microcomputer 12, and the microcomputer 12 uses the silencing circuit 4 and the digital-to-analog signal at an appropriate timing. Since the conversion circuit 16 is activated, the multipath noise part of the audio signal obtained at the output of the FM detection circuit 2 is muted by the silencing circuit 4, and the audio signal is muted by the adding circuit 5. - The audio signal immediately preceding the silenced portion of the audio signal supplied via the digital-to-analog conversion circuit 16 is interpolated to the silenced portion of the audio signal.

[0032] Therefore, the output of the FM receiver is a high-quality audio signal that does not contain multipath noise, has no audio interruptions, and does not cause any discomfort to the listener. can be emitted aloud.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing one embodiment of a signal interpolation system of the present invention.

FIG. 2 is a signal waveform diagram showing signals of each part in the embodiment configuration diagram of FIG. 1;

FIG. 3 is a block diagram showing another embodiment of the signal interpolation system of the present invention.

[Explanation of symbols]

1 FM receiver front end 2 FM detection circuit 3 Noise canceller 4 Silencing circuit (muting circuit) 5 Adding circuit 6 Stereo demodulation circuit (multiplex decoder)
7 Audio amplifier 8 Speaker 9 100KHz high-pass filter 10 Detection circuit 11 Smoothing circuit 12 Microcomputer 13 Analog-to-digital conversion circuit 14 First IC memory 15 Second IC memory 16 Digital-to-analog conversion Circuit 30 Signal interpolation means

Claims (1)

[Claims] 1. A detection means for detecting FM signal multipath noise in an FM reception signal, a silencing means for temporarily silencing a received audio signal, and a silencing means for temporarily silencing a received audio signal.
a recording and reproducing section for sequentially recording and reproducing the audio signal; and a recording and reproducing section that operates the silencing section in response to the output of the detecting section, and performs the recording on the muted portion of the temporarily muted audio signal. 1. A signal interpolation system for an FM receiver, comprising signal interpolation means comprising a control section that interpolates an audio signal immediately before the silenced portion from a reproduction section.