JPS599962B2 - Onseishingouno Kirokusaiseisouchi - Google Patents

Description

[Detailed description of the invention] The present invention relates to an audio signal recording and reproducing device.

Recording sources for music and the like include FM stereo broadcasts, concerts, natural sounds, and copies from other recording media.

Among these, recording of FM stereo broadcasts is the most commonly used. However, when considering these recording sources, F.
Like M stereo broadcasting, the frequency band of the audio signal (
(hereinafter referred to as audio signal band) is suppressed to 15KH2, or 20KH2 such as music at a concert etc.
There are also those that have a frequency band that is higher than that. As a device for recording such signals, it is possible to decode and record FM stereo broadcasts once, but decoding can cause imbalances between channels, phase shifts, etc., resulting in quality deterioration. The problem arises. The present invention relates to a device that frequency multiplexes these stereo recording sources with different frequency bands, performs FM modulation, and records and reproduces them on one track of a recording medium. , which modulates and records one FM carrier.

When reproducing these signals, it is possible to faithfully reproduce the recording source regardless of the difference in frequency allocation for multiplexing. Examples thereof will be described below.

FIG. 1 is a diagram showing frequency bands when recording FM stereo broadcasts.

Al, A2, As indicate the band division method of current FM stereo broadcasting, Al is the main channel signal (ch1 + ch2),
A2 is a sub-channel signal, and the sub-carrier 38KH2 is balanced-modulated with the (chl-ch2) signal. As is 1
This is the pilot signal of 9KH2. A4 is the main channel signal Al, the subchannel signal A2, and the pilot signal As.
This is a broadcast wave that is modulated by FM broadcast radio waves (80 MH2 as an example) using a multiplexed signal. A5 is an FM receiver that transmits FM stereo broadcast waves A4 at an intermediate frequency of 10
．． In the same way as frequency conversion to 7MH2, FM stereo broadcast wave A4 is converted to recording band (for example, 5MHz frequency).
00KH2). FIG. 2 is a diagram showing an example of frequency bands when recording music such as a concert.

Here, as an example, the audio signal band is up to 20KH2, and the pilot signal is 28.5KH2. B1 is the main channel signal (ch1+ch2), B2 is the sub-channel signal (Chl-Ch2), and the subcarrier is 57 KHz.
is modulated in equilibrium. B3 is pilot signal 28.5K
It is Hz. B4 is an FM carrier of the frequency band to be recorded (as an example, 50
0KHz), which is FM modulated, and serves as a modulation signal to be recorded on a recording medium. As described above, even if the audio signal has a different frequency band, such as FM stereo broadcasting or music from a concert, the FM modulation signal A to be recorded is
5 and B4 are recorded in the same frequency band. Therefore, FM
Even audio signals with different bands, such as stereo broadcasts or music from concerts, can be recorded on one recording medium in their respective bands. Next, an example of a recording circuit for recording music from the above-mentioned FM stereo broadcasts, concerts, etc. will be explained with reference to FIG. In the figure, 1 is an antenna through which FM stereo broadcasting arrives, and 2 is an FM receiver, which outputs a high-frequency signal before frequency conversion. 3 is a frequency converter that converts the frequency into a frequency band A5 required for recording.

Note that A5 is a 500KHz FM radio station. 4 is a switching circuit that switches between two inputs and outputs one of them; 5 is a recording head for recording a signal on a recording medium 6;

Reference numerals 7 and 8 are input terminals to which audio signals up to a band of 20 KHz are applied, respectively; here, the input terminal 7 is designated as Chl, and the input terminal 8 is designated as Ch2.

A matrix circuit 9 generates a sum signal Chl+Ch2 of two input signals at an output terminal 9a, and a difference signal Chl-Ch2 at an output terminal 9b.

The sum signal is assumed to be the main channel signal B1. 10 is an adder,
11 is an oscillator for generating a pilot signal, 12 is a doubling circuit for obtaining a subcarrier, 13 is a balanced modulator, and 14 is an FM modulator. Next, the operation of this recording circuit will be explained.

When recording an FM stereo broadcast, first the switching circuit 4 is operated so that the output of the frequency converter 3 is applied to the recording head 5. An FM stereo broadcast received by an antenna 1 is received on a predetermined channel by an FM receiver 2, amplified, outputted without frequency conversion, and added to a frequency converter 3. This frequency converter 3 converts the modulated signal A5 into a modulated signal A5 having a frequency band required for recording, for example, FM carrier 500 KHz. This modulated signal A5 is sent to the recording head 5 via a switching circuit 4.
In addition, it is recorded on the recording medium 6. Further, when recording music from a concert or the like in stereo, the switching circuit 4 is first switched so that the output of the FM modulator 14 is applied to the recording head 5.

The signals of Chl and ch2 applied to input terminals 7 and 8, respectively, are converted into a sum signal and a difference signal by a matrix circuit 9.
The sum signal is applied directly to adder 10 as main channel signal B1. The difference signal is also applied to a balanced modulator 13,
It is modulated with the 57 KHz subcarrier obtained from the doubler circuit 12, and is applied to the adder 10 as a subchannel signal B2. Adder 10 multiplexes main and sub channel signals B1, B2 and pilot signal B3. This multiplexed signal is, for example, 500KHz0) FM Senyariya.
The signal is modulated by the M modulator 14, applied to the recording head via the switching circuit 4, and recorded on the recording medium 6. Like this FM
Even signals with different audio signal bands, such as music from stereo broadcasts or concerts, can be recorded on the recording medium 6 without deteriorating quality. Next, when signals of different audio signal bands as described above are recorded on the recording medium 6, FIG. 4 shows a reproducing circuit that can faithfully reproduce the recorded signals regardless of the difference in the bands.

6 is a recording medium in FIG. 3, 21 is a reproduction head, 22
is an FM demodulator which converts the main channel signal, sub-channel signal,
A multiplexed pilot signal is obtained as a demodulated signal.

23 is a pilot signal detection circuit, and from the demodulated signal,
Different pilot signals are detected depending on the audio signal to be reproduced.

24 is a phase detector, 25 is a low-pass filter, 26 is a DC amplifier, 27 is a voltage controlled oscillator (hereinafter referred to as CO), 28 is a 1/2 frequency divider, and 29 is a 1/2 frequency divider. .

Note that 24, 25, . . . 29 constitute a phase lock loop (hereinafter referred to as PLL). That is, the phase detector 24 detects the phase difference between the pilot signal obtained from the pilot signal detection circuit 23 and the feedback signal from the 1/2 frequency divider 29, converts it into a voltage, and integrates it in the low frequency divider 25. , a voltage component proportional to the phase difference is extracted, amplified by the DC amplifier 26, and added to the CO27.
Since the VCO27 oscillates according to the input voltage, 1
For example, 76KHz1 or 2, which is 4 times the frequency of 19KHz.
The manual voltage is set to oscillate at a frequency of 114 KHz, which is four times 8.5 KlIz. In the 1/2 frequency divider 28, C
Obtain 38KHz1 or 57KHz, which is 1/2 of the oscillation frequency of O27.

The 1/2 frequency divider 29 divides 1/2 of the output signal of the 1/2 frequency divider 28.
2 frequencies of 19KHz1 or 28.5KHz are obtained.

The signal thus obtained by the pilot signal detection circuit 23 is passed through the PLL to obtain a stable pilot signal of 19 KHz or 28.5 KHz. A switching circuit 30 is controlled by the output of a switching signal generation circuit 31, which will be described later, and applies the demodulated signal to low frequency filters 32 and 33 having different frequency characteristics depending on the audio signal band to be reproduced.

Further, 34 is a switching circuit similarly controlled by the output of the switching signal generation circuit 31, and a switching circuit 34 having different frequency characteristics.
Add to 5,36. As an example, the low frequency filter 32 obtains the main channel signal shown in A2 of FIG. 5, and the low frequency filter 33 obtains the main channel signal shown in FIG. 5, B2.

It is assumed that the band filter 35 obtains the sub-channel signal shown in FIG. 5A3, and the band filter 36 obtains the sub-channel signal shown in FIG. 5B3. Reference numeral 31 denotes a switching signal generation circuit for generating the above-mentioned switching signal, which is composed of, for example, a comparator, inputs the DC voltage to be input to the VCO 27, and outputs H and L level signals based on the level difference of the DC voltage.

Therefore, when reproducing FM stereo broadcasting, if the switching signal is at H level, the demodulated signal is sent to the low frequency filter 32 and the band filter 35, and if the switching signal is at L level, the demodulated signal is sent to the low frequency filter 32 and the band filter 35. The signal is sent to a low frequency filter 33 and a band filter 36. 37 is a matrix circuit to which the main channel signals (Chl+Ch2) obtained from the low-frequency F wave generators 32 and 33 are added;
Reference numeral 0 denotes a detection circuit to which sub-channel signals obtained from the bandpass filters 35 and 36 are added, and performs synchronous detection using the sub-carrier to obtain a difference signal (Chl-Ch2).

This difference signal is applied to matrix circuit 37. That is, the matrix circuit 37 receives the main channel signal (Chl+C
h2) and the difference signal (Ch
l-Ch2) is added. 38 is an output terminal where the Chl output signal is generated, and 39 is an output terminal where the Ch2 output signal is generated.

Next, the operation of the reproducing circuit when reproducing FM stereo broadcasting will be explained. If a pilot signal of 19 KHz (A in FIG. 5) is obtained in the pilot signal detection circuit 23, a DC voltage equivalent to generating 76) KHz is applied to the CO 27.

If VCO27 generates 76KHz, 1/2 frequency divider 2
8, a frequency of 38 KHz, which is 1/2 of 76 KHz, is obtained and used as a subcarrier. Furthermore, 19 KHz is obtained by the 1/2 frequency divider 29 and fed back to the phase detector 24. On the other hand, the switching signal generation circuit 31 is activated by the DC voltage applied to the VCO 27, the switching signal becomes H level, and the switching circuits 30 and 34 send the demodulated signal to the low frequency waveform generator 32 and the band waveform waveform generator 35. . The signal obtained by the low frequency filter 32 is the main channel signal (Chl+Ch2) shown in FIG. 5A2. The signal obtained by the band filter 35 is a sub-channel signal shown in A3 in FIG. 5, and is synchronously filtered by the subcarrier in the filter circuit 40 to obtain a difference signal (Chl-Ch2). The matrix circuit 37 has main channel signals (Chl+Ch2)
The difference signal (Ch]-Ch which is the demodulated sub-channel signal
2) is added, Ch1 is obtained at the output terminal 38, Ch2 is obtained at the output terminal 39, and an audio signal in the audio signal band up to 15 KHz is obtained. When reproducing music such as a concert, a pilot signal of 28.5 KHz as shown in FIG. 5 b1 is obtained by the pilot signal detection circuit 23, and the VCO 27
It generates 114KHz.

The 1/2 frequency divider 28 generates 57KI{z, and also 1/2
The frequency divider 29 generates 28.5 KHz.

Further, the switching signal becomes L level and the demodulated signal is applied to the low frequency waveform generator 33 and the band waveform waveform generator 36 by the switching circuits 30 and 34. Therefore, the output signal of the low-frequency filter 33 is as shown in FIG.
The main channel signal (Chl+Ch2) shown in 2 is obtained,
Added to matrix circuit 37. In addition, the sub-channel signal shown in FIG. 5B3 is obtained as the output signal of the bandpass filter 36,
The waveform circuit 40 performs synchronous detection using a subcarrier of 57 KHz to obtain a difference signal (Ch]-Ch2). Matrix circuit 3
7, the main channel signal (Chl+Ch2) and the difference signal (Chl-Ch2) are added. Therefore, Chl and ch2 are obtained as output signals of the matrix circuit 37, and an audio signal with an audio signal band of up to 20 KHz can be obtained. As described above, if the low frequency waveform generators 32, 33 and the band waveform waveforms 35, 36 are switched using the DC voltage 37 generated by obtaining one of the pilot signals, different audio signals can be recorded on one recording medium. Even if a band audio signal is recorded, it can be faithfully reproduced. Furthermore, in the above description, the low frequency waveformers 32 and 33 are used to obtain the main channel signal, and the low frequency waveformers 35 and 36 are connected to the audio signal band 1 to obtain the sub channel signal.
Although one for 5 KHz and one for 20 KHz were provided, the same effect can be obtained by switching the cut-off frequency within one low-frequency P-wave device and one band-pass wave device. Next, as a means for detecting the pilot signal from the demodulated signal, the pilot signal detection circuit 23 is briefly shown in FIG. 4, and the pilot signal detection circuit 23 is shown in FIG.
One specific example is shown below.

41 and 42 are band transmitters, 41 outputs a frequency component of 19 KHz shown in Figure 5 a1, and 42 outputs a frequency component of 19 KHz shown in Figure 5 b1.
The 28.5KHz frequency component shown in is output.

43, 44 are integrating circuits to which the signals obtained by the band filters 41, 42 are added.

The time constants of the integrating circuits 43 and 44 are set large, and the signals obtained by the bandpass converters 41 and 42 are converted into DC voltages. 45 compares the DC voltages obtained by the integrating circuits 43 and 44, and sets the higher DC voltage to H level;
Also, comparators 46 and 47 are switching circuits that output a switching signal such that the lower one becomes L level, and when the switching signal composed of the gate circuit becomes H level, the signal obtained by the band wave generators 41 and 42 is switched. It sends out signals.

The phase detector 24 outputs one of the signals obtained by the band filters 41 and 42 as a pilot signal. Next, the detection of pilot signals when reproducing FM stereo broadcasting will be described. A signal with a frequency component of 19 KHz is obtained by the bandpass filter 41. This signal is applied to an integrating circuit 43. The DC voltage that is the integrated output signal is applied to the comparator 45, and when compared with the DC voltage obtained from one integrating circuit 44, the switching signal becomes H level. In response to the switching signal, the signal obtained from the bandpass filter 41 is sent as a pilot signal to the phase detector 24 shown in FIG. Also, pilot signal 28.5KH when playing music at concerts etc.
z can also be detected by comparing the DC voltages from the integrating circuits 43 and 44 in the same way. When doing this, pilot signal 1 when playing FM stereo broadcasting
When 9 KHz is being detected by the band transducer 41, there is a case where one of the band transducers 42 detects 28.5 KHz. Also, pilot signal 28 when playing music at a concert, etc.
．． When 5KHz is being detected by the pre-band waver 42, the 20 KHz audio signal band may also include an audio signal equivalent to 19 KHz, which is the pilot signal for FM stereo broadcasting, Although 19 KHz may be detected by the detector 41, this problem can be solved by setting the time constants of the integrating circuits 43 and 44 to be large, since it does not last for a long time like a pilot signal.
As explained above, according to the present invention, during recording, F
Even if the audio signals have different bands, such as M stereo broadcasts or music from concerts, it is possible to directly record the audio signals in each audio signal band.

In addition, during playback, by detecting each pilot signal, it is possible to faithfully reproduce the audio signal without deteriorating the quality by switching each low frequency wave filter or band wave filter. can.

[Brief explanation of the drawing]

FIG. 1 and FIG. 2 are diagrams showing the band characteristics of a signal used in an audio signal recording and reproducing device according to an embodiment of the present invention, respectively;
FIG. 3 is a block diagram of the recording device, FIG. 4 is a block diagram of the reproducing device, and FIG. 5 is a diagram showing the signal characteristics of the main parts.
FIG. 6 is a block diagram showing the detailed circuit configuration of the main parts. 2...FM receiver, 5...recording head, 6...recording medium, 10...adder,
14...FM modulator, 21...Reproduction head, 23...Pilot signal detection circuit, 31
...Switching signal generation circuit, 30, 34...
・Switching circuit, 32, 33...Low frequency transducer, 35
, 36...- Bandwidth wave device.

Claims (1)

[Claims] 1. A means for frequency multiplexing stereo signals with different signal bands according to each band, a means for FM modulating a carrier of an arbitrary frequency with this frequency multiplexed signal and recording it on a recording medium, and a means for reproducing from the recording medium. A means for automatically detecting and identifying the frequency of a pilot signal included in a reproduced signal obtained by using a low-pass filter and a passband of a bandpass filter for demodulating a frequency multiplexed signal according to the detected signal. 1. An audio signal recording and reproducing device, characterized in that it is provided with means for changing.