JPS618771A - Recording and reproducing device - Google Patents

Abstract

PURPOSE:To perform narrow-band transmission and to obtain a good-S/N playback signal by recording an input signal after frequency modulation of carrier frequency higher than the highest frequency, and multiplying the frequency-modulated wave substantially by four for demodulation during reproducing operation. CONSTITUTION:The input signal is inputted to an input terminal 1 and converted into an FM wave by a voltage-controlled oscillator 2. The carrier frequency of the FM modulated wave is set higher than the maximum frequency of the input signal and this FM wave is recorded on a magnetic tape 4 through a magnetic head 3. The FM signal recorded on the tape 4 is reproduced by a magnetic head 5 and the reproduced FM wave is supplied to a four-multiplication type demodulator 6. The demodulator 6 consists of a 90 deg. phase shifter 8 composed of a transversal filter and an FM demodulator 11 which is connected to the phase shifter 8 and multiplies signals from input terminals 12 and 13 by two to perform substantially four multiplication, and the output of the demodulator 6 is supplied to an output terminal 7. Thus, narrow-band recording and reproduction are performed and the S/N is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an apparatus, such as a video tape recorder, which records and reproduces information using low carrier FM.

Conventional configuration and its problems Conventionally, low carrier wave FM such as video tape recorders, etc.
In a device that transmits (records and reproduces) information using a pulse counter demodulation or qualifier demodulation, the above FM wave is, for example, differentiated between the waves, doubled, and then demodulated with a pulse count/return during reproduction. were used, but in both cases the second lower side wave of the doubled FM wave (
J2) does not mix into the demodulated signal band, f>-fc
2a (fc: the lowest frequency of the FM signal frequency, fa: the highest signal frequency), so it was necessary to have a wide transmission band. For this reason, the FM key rear frequency must be set high, resulting in problems such as a decrease in S/H.

purpose of invention The present invention solves the above-mentioned problems and eliminates the conventional condition f.

The purpose of this invention is to provide a device Ca that performs transmission (recording and reproduction) under lower frequency conditions (that is, f>f).

However, fc is the lowest frequency of the FM carrier frequencies.

Another purpose is to improve the S/N of the reproduced signal by transmitting (recording and reproducing) the signal under the condition that fc>.

Furthermore, it is an object of the present invention to provide a device that transmits (records and reproduces) data using a narrower band transmission path by transmitting (recording and reproducing) under the condition fc>f.

Furthermore, the third lower side wave (J5) of the FM wave multiplied by 4 during demodulation is
) is not mixed into the demodulated signal band, thereby improving the S/N of the reproduced signal.

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention is an apparatus for recording and reproducing by frequency modulating an input signal, in which the highest frequency of the input signal is fc, the carrier frequency of the frequency modulated wave is f, fc>, and upon reproduction, the reproduced frequency modulated wave is effectively multiplied by 4 and demodulated.

Description of Examples Low carrier wave F used in video tape recorders, etc.
In M, conventionally, Fig. 1(a),' (bl l (C
It was modulated and demodulated using the frequency allocation shown in 1. FIG. 1(a-) shows the frequency band of the input signal to be recorded, and fa indicates the highest frequency of the input signal. FIG. 1(b) shows the frequency occupied band of such a signal subjected to FM. Figure 1 (b
In l, fc indicates the FM carrier frequency,
Here, the lowest frequency of FM deviation is shown. The frequency of the first lower side wave (Jl) is fc-f. The frequency allocation when such an FM signal is demodulated by a commonly used doubling type pulse power demodulator is shown in Figure 1 (cl). Here, the FM carrier frequency becomes 2f0 by doubling, 1st lower side wave (Jl)
and a second lower side wave (Jl) is generated. The frequency of Jl is 2
To fc-.

The frequency of Jl is 2f0-2f. The condition is that this Jl does not fall within the band of the demodulated signal, that is, f<2
fc-2fa fc<÷f, −・・−・−・=−=・−・・・・=−(1
) is required, and the F of the F M signal shown in Fig. 1(b) is required.
The lower limit of the frequency band occupied by Mdevi 7 was set.

The condition shown in equation (1) is caused by a double-multiplying demodulator, and if a quadruple-multiplying demodulator according to the present invention described below is used, the conditions shown in FIG. 2 (&), (kl), (C1) It can be modulated and demodulated with such frequency allocation. Figure 2 (2L) shows the frequency band of the same input signal as in Figure 1 (a). Figure 2 (b) shows the frequency band of such a signal after FM. This shows the frequency occupied band of the signal.Here, fc>fa is set.The frequency allocation when such an FM signal is quadruple demodulated by the quadruple demodulator according to the configuration of the present invention is shown as the second frequency allocation. Figure (C) shows that the FM carrier frequency is multiplied by 4 and becomes 4fc, which is the first lower side wave (JT).

The second lower side wave (Jl)+the third lower side wave (J,) is generated.

The frequency of Jl is "C'al The frequency of J2 is 4f0-2f
The frequencies of 2L and J3 are 4f0-38. As a condition that J3 does not fall within the band of the demodulated signal, Equation 1 Equation (2) represents the lower frequency limit (fc) of the FM carrier shown in FIG. 2(b), that is, the lower limit frequency of the FM deviation.

FIG. 3 shows a schematic configuration diagram of a recording system (modulation system) according to the present invention. An input signal is applied to an input terminal 1 and is converted into an FM wave υC by a VCO (voltage controlled oscillator) 2. The frequency band of the input signal is shown in FIG. 2 (al), and the occupied frequency band of the FM wave is shown in FIG. 2 (b).

Such FM waves are magnetically recorded on the tape 4 via the magnetic head 3.

FIG. 4 shows a schematic configuration diagram of the reproduction system (demodulation system).

A magnetic head 5 reproduces the FM signal recorded on the magnetic tape 4 and supplies it to a quadruple demodulator 6 . 4 has been 2
It consists of a 7M demodulator 11 whose input terminal is 12.13 and whose output terminal is 21, and the output signal of the demodulator 6 is supplied to the output terminal 7. 900 phase? ! ? The i8 has a transversal filter type configuration, and examples of the configuration are shown in FIGS. 5 and 6. FIG. 5 shows a configuration example using one stage of delay line 14 (900 phase shifter 22), and FIG. 6 shows a two-stage delay line configuration (900 phase shifter 23) using delay lines 15 and 16. 90 phase shifters composed of multistage delay lines of three or more stages are A, Ghowaniec, G, and S.
.

Hobson: The Use of Charg
e-Coupled Devices fcr Sin
gle 5ideband ModJation, In
t, Conf.

of Charge-Coupled Device
es (1974) 237-244 [(
are shown and may be used.

The operation of the 900° phase shifter 8 is shown in FIG.
This will be explained using a phase shifter 22). The FM signal supplied to the input terminal 17 is supplied to a delay line 14 whose delay time is T, an adder 19, and a subtracter 18. The output signal of the delay line 14 is also supplied to an adder 19.degree. subtracter 18, and the result is outputted to output terminals 1o and 9. The signal vector diagram (complex plan view), frequency' characteristics, and signal frequency allocation of each part of the 90° phase shifter 22 are shown in FIG. 7 (a+,
(b) (shown in cl.

In FIG. 7(a), vector A shows the FM signal supplied to input terminal 17, and vector B shows the delayed inversion (18Q
0 phase shift) signal. These signals are sent to adder 19. As a result of the calculation in the subtracter 18, the vector D is output to the output terminal 10.
A signal represented by vector E is outputted to the output terminal 9.

When vector A is normalized and represented by 1, vector D and vector E are represented by equations (3) and (4).

Vector D = 1+exp(-j 2wf T )
---(3) Vector E=1-exp(-j 2πfT
) -- (4j However, f: Frequency of the input signal From FIG. 7 (&) which is a complex plane diagram, it can be understood that the vector D and the vector E have an orthogonal relationship (relative phase difference of 900). The frequency-amplitude characteristics of each vector E are shown by the solid line and broken line in FIG. 7(b).
From equations 3) and 4, vector D and vector E each have a linear frequency-phase characteristic, so the frequency-single group delay characteristic becomes a constant value, and group delay distortion does not occur. Figure 7 (
b) l (As shown in C1, it is important to set the delay time T of the T delay line 14 so that the center value of the FM carrier becomes the frequency -.

In addition, Fig. 7(b) shows the amplitude of vector C and vector E -
The frequency characteristics are shown, where the solid line is the characteristic of vector C, and the broken line is the characteristic of vector E.

Figure 7(C) shows a desirable example of the frequency arrangement of the FM signal.If the frequency corresponding to the intersection of the solid line and the broken line in Figure 7(b) is set at the center of the FM deviation, the band can be effectively expanded. can be used.

The two systems of FM signals with a relative phase difference of 900 thus obtained are sent to the FM demodulator 11 via the output terminals 10 and 9.
0 input terminal 13.12. A 90° phase shifter 23, which is another embodiment shown in FIG. 6, is composed of a delay line 15, 16 with a delay time of T and a subtracter 20, and similarly outputs a signal with a relative phase difference of 900. It is known.

Examples of the configuration of the 7M demodulator 11 are shown in FIGS. 8 and 9.

The 7M demodulators are shown in FIG. 10 as 24.25.26. 7
The operation of the M demodulator 11 will be explained using the configuration example (7M demodulator 24) shown in FIG. Two systems of FM signals with a relative phase difference 900 supplied to input terminals 13.12 are outputted via limiters 27.28 and double-wave differentiating circuits 29.30, respectively.
After performing an OR operation in the R circuit 31 and converting it into a single system of quadrupled FM signals, it is made into a signal with a predetermined pulse width by a monostable mono multi-bi break, and the demodulated signal component is converted into a p-wave by a low-pass filter 33. 6, which is supplied to the output terminal 21;
Signal waveforms at each part of the 7M demodulator 24 are shown in FIGS. 11(a) to 11(f). Figure 11 (a) l (b)
9 respectively show the FM signals input to the double-wave differentiating circuits 29 and 30, and FIGS. 11(C) and 11(d) show the output signal waveforms of the double-wave differentiating circuits 29 and 30, respectively. By performing the logical sum of such signal waveforms in the OR circuit 31, one system of 4-multiplied FM signals as shown in FIG. 11 (6) is obtained. This signal is converted into a pulse wave with a predetermined pulse width as shown in FIG. P wave component.

Another configuration example shown in FIG. 9 is a limiter 2γ.

28, double-wave differentiating circuits 29, 30, monostable monomulti-bi breakers 34, 35, low-pass filters 36, 37, and an adder 38, and operate in the same manner.

Another configuration shown in FIG.
, an exclusive OR circuit 39, a double-wave differentiating circuit 29, a monostable monomulti-bi break 32, and a low-pass filter 33. The output end of the limiter 27°28 has a first
Signal waveforms as shown in FIGS. 1(a) and 1(b) are output, and the exclusive OR circuit 39 obtains a doubled signal waveform as shown in FIG. 11(q). Such a signal waveform is processed by a subsequent double-wave differentiating circuit 29, a monostable monomulti-bi break, and a low-pass filter 33.
Since so-called pulse counter demodulation is performed, the system is quadruple demodulated.

In the above explanation, a device that records and reproduces an input signal by FM was described, but for example,
It can also be applied to luminance signal systems such as the so-called color under system used in TR. That is, as is well known, the color under method lowers the signal of the carrier color signal band (mainly the carrier color signal) of the input composite picture signal so that the color subcarrier is converted to, for example, 629KH2. At the same time, frequency components lower than the input carrier color signal (so-called luminance signal system) are converted to FM and recorded, so the present invention can be applied to this luminance signal system.

Similarly, since the color signal of the SECAM signal is FM, S
The present invention can also be applied to recording and reproducing color signals of ECAM signals.

Although the FM demodulator 11 has been explained using a pulse counter type in all cases, conventionally known demodulation methods such as FMi modulation using a PLL (phase-locked loop) and FM demodulation using Fodoratch detection method can be used. The FM demodulator 11 may be configured using the following.

In addition, the explanation has been made using an electromagnetic conversion system, that is, a tape head system, as an FM transmission path, but in some cases, such as satellite broadcasting,
The present invention can be similarly applied to any modulation/demodulation system using M signals.

Effects of the invention As described above, the recording and reproducing apparatus according to the present invention has the following effects:
By quadruple demodulating the reproduced FM signal, the conditions for the FM carrier frequency (fc) during recording and the highest input signal frequency (mu) can be set as f>f, which results in better transmission of S/H. (recording and playback).

Furthermore, due to the above condition (fc>fL), transmission (recording and reproduction) can be performed in a narrower band than in the past.

Furthermore, by quadrupling demodulation, the third lower side wave (J3) of the FM signal does not mix into the demodulated signal band, so the S/H
A good playback signal can be obtained.

[Brief explanation of the drawing]

Fig. 1 is a frequency characteristic diagram showing the frequency occupied band of the signal in the conventional FM modulation and demodulation process, and Fig. 2 is a frequency characteristic diagram showing the frequency occupied band of the signal in the FM modulation and demodulation process according to the present invention. FIG. 3 is a block diagram showing a schematic configuration of a recording system of a recording and reproducing apparatus according to an embodiment of the present invention, FIG. 4 is a block diagram showing a schematic configuration of a reproducing system, and FIG.
The figure is a block diagram showing an example of the configuration of the 90° phase shifter in FIG. 4, and FIG. 6 is a block diagram showing an example of another configuration.
Figure 7 (a) I (b) l (C) are the fifth
Vector diagram and frequency characteristic diagram 2 showing the operation of the configuration shown in the figure
Frequency characteristics diagram, FIG. 8 is a block diagram showing an example of the configuration of the FM demodulator in FIG. 4, FIG. 9 is a block diagram showing another example, and FIG. 10 is a block diagram showing yet another example. , FIG. 11 is a waveform diagram showing waveforms at various parts in FIGS. 9 and 10. 8...900 phase shifter, 11 ・FM demodulator, 22
・900 phase shifter, 14 Delay line, 18-... subtractor, 19... Adder, 23...-900 phase shifter, 15, 16""" delay line, 20 Subtractor, 24
．． 25.26...FM demodulator. Name of agent: Patent attorney Toshio Nakao (1st person)
Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure JC Figure 8 Figure 9 Figure 10

Claims (2)

[Claims] (1) The highest frequency of the input signal is f_a, the carrier frequency of the frequency modulated wave is f_c, the condition of f_c>f_a is satisfied, and means for frequency modulating and recording the input signal, and the frequency reproduced at the time of reproduction. Modulated wave effectively 4
1. A recording/reproducing device characterized by comprising means for multiplying and demodulating. (2) As a circuit for quadrupling and demodulating, a phase shifter inputs a frequency modulated wave and outputs two output signals having a relative phase difference of 90 degrees, and inputs the two output signals. and a frequency demodulator that effectively quadruples and demodulates each signal by doubling, and the phase shifter is configured with a transversal filter, according to claim 1. recording and reproducing equipment.