JP2622956B2 - Video signal playback device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a video signal reproducing apparatus, and more particularly to a video signal for reproducing a video signal recorded on a recording medium by selectively switching a carrier frequency of a frequency-modulated video signal. It relates to a playback device.

2. Description of the Related Art In recent years, there has been a growing demand for higher resolution of video equipment, and various systems have been proposed. For example, a large screen display of 28 inches or more is desired to have a high resolution, and some home-use displays realize, for example, a horizontal resolution of 560 TV lines. Also, in television broadcasting, research is being conducted to increase the resolution while maintaining compatibility with the current system (for example, Journal of the Institute of Television Engineers of Japan Vol.4).
0, No. 5, "Special Edition EDTV and IDTV" (May 1986).
Further, among the video signal reproducing devices, some of the video signal reproducing devices realize a horizontal resolution of 400 TV lines.

In response to such a trend of higher image quality, it is desired to achieve higher resolution in a helical scan VTR of a low-frequency conversion color recording / reproducing system. FIG. 10 is a block diagram showing an example of a VTR reproducing system, that is, an example of a video signal reproducing apparatus. In the figure, frequency division multiplexed signals of a frequency-modulated luminance signal (FM luminance signal) and a reduced conversion carrier chrominance signal are reproduced from recording tracks on a magnetic tape by rotating heads 1 and 2, and rotary transformers 3 and 4 and a head are used. The signals are successively passed through the amplifiers 5 and 6 and supplied to the switch circuit 7, where the signals are alternately switched for each field to form a continuous reproduced frequency division multiplexed signal. The capacitors Ca and Cb connected between the inputs of the head amplifiers 5 and 6 and the ground are for obtaining head resonance.

The reproduced frequency division multiplexed signal extracted from the switch circuit 7 is split into two, one of which is a high-pass filter (hereinafter referred to as HPF).
8 to separate the reproduced FM luminance signal.
The other is output via a terminal 9 to a known color system. HP
The reproduced FM luminance signal extracted from F8 is FM equalizer 10,
The signal is supplied to an FM demodulator 13 via an AGC circuit 11 and a limiter 12, where the signal is subjected to FM demodulation to be a reproduced luminance signal, and then a low-pass filter (hereinafter referred to as LPF) 14 and a de-emphasis circuit 1
5 and output to the output terminal 16 respectively.

The recorded video signal on the magnetic tape reproduced by such a video signal reproducing device is in a mode of the current VTR standard (hereinafter, referred to as a mode).
In this mode, which is referred to as a standard image quality mode or A mode), as shown in FIG. 2A, for example, a carrier frequency deviation of 3.4 MHz corresponding to a sync chip level and a carrier frequency 4.4 MHz corresponding to a white peak level is used. and FM luminance signal Y _a having moved, the more becomes the frequency division multiplex signal and the low-band converting carrier chrominance signal C _a color subcarrier frequency of about 629KHz.

Meanwhile, remarkable advances in performance of recent magnetic tapes performance and rotary head, recording the carrier frequency of the FM luminance signal is set higher than that of the FM luminance signal Y _A, by reproducing the above standard definition Recording and reproduction in a high-quality mode (this is also referred to as a B mode) that obtains a high-quality image with a higher horizontal resolution than an image recorded and reproduced in the mode has become possible.

Therefore, when focusing only on the image quality, a video signal reproducing apparatus dedicated to the high image quality mode may be configured. However, in the standard image quality mode (A mode), an inexpensive magnetic tape can be used, and the high image quality mode ( There is an advantage that a video signal recorded using a conventional video signal recording device dedicated to the standard image quality mode which cannot be recorded in the B mode) can be reproduced, and the standard image quality mode is hard to be discarded. Thus, the present invention relates to a video signal reproducing apparatus capable of switching and reproducing both the A and B modes.

Problems to be Solved by the Invention When the video signal reproducing apparatus having the above-described configuration switches and reproduces both the A and B modes, the video signal recorded in the high image quality mode (B mode) is shown in FIG. ) to as shown the frequency spectrum, for example, sinks carrier frequency corresponding to the chip level is 5.4 MHz, FM luminance signal Y _B and the color subcarrier frequency which is a carrier frequency corresponding to the white peak level having a carrier frequency shift of 7.0MHz is more becomes frequency division multiplexed signal and the low-band converting carrier chrominance signal C _B of about 629kHz, FM
As can be seen from FIGS. 2A and 2B, the carrier frequency of the luminance signal is different from each other in both modes.

For this reason, if the FM equalizer 10 is commonly used in both modes as shown in FIG. 10, the optimum characteristics will not be obtained in at least one of the modes. There is a problem that image quality cannot be obtained.

Accordingly, it is an object of the present invention to provide a video signal reproducing apparatus which solves the above-mentioned problems by switching the equalizer characteristics of a single equalizer circuit in each of the modes.

Means for Solving the Problems The video signal reproducing apparatus according to the present invention includes a rotary transformer for transmitting a signal reproduced from a rotary head, and a frequency-modulated video signal reproduced via the rotary transformer, which is synthesized with a plurality of peaking circuits. A recording mode in which the carrier frequency of the frequency-modulated video signal is approximately 3.4 MHz at the sync tip level and approximately 4.4 MHz at the white peak level, and approximately 5.4 MHz at the sync tip level and approximately 7 MHz at the white peak level
An equalizer circuit that provides an equalizer characteristic according to the recording mode to be performed, a limiter circuit that limits the amplitude of the reproduced frequency-modulated video signal that has passed through the equalizer circuit, and a frequency demodulation that is performed on the reproduced frequency-modulated video signal that has passed through the limiter circuit. A frequency demodulation circuit to be applied, a low-pass filter that limits the band of an output signal of the frequency demodulation circuit, and a de-emphasis circuit that performs de-emphasis on the output signal of the low-pass filter and outputs a reproduced video signal. is there.

The recording medium in which the frequency-modulated video signal is recorded in any one of n types of modes (where n is an integer of 2 or more) in which the carrier frequencies of the frequency-modulated video signal are different from each other is shared. The reproduced frequency-modulated video signal of one recording mode reproduced by the head is supplied to an equalizer circuit through a common head amplifier. The equalizer circuit switches the recording mode to a predetermined equalizer characteristic based on a signal obtained by determining the recording mode of the reproduced frequency-modulated video signal.

This is for the following reason. Now, it is assumed that the n types of modes are the above-described standard image quality mode (A mode) and high image quality mode (B mode), and a recording medium on which signals of each frequency are recorded with an optimum recording current is reproduced. It is assumed that the reproduced output at this time has a frequency characteristic shown by a solid line in FIG. 2 (C).

When the A-mode frequency division multiplexed signal shown in FIG. 2A is recorded on such a recording medium and reproduced,
Since the reproduction output level of the lower sideband of the frequency modulated luminance signal is higher than the reproduction output level near the FM carrier frequency, a so-called inversion phenomenon occurs. Therefore, level correction is usually performed using an equalizer circuit so that the reproduction output level near the FM carrier is higher than the reproduction output level of the lower band.

FIG. 2D shows an example of an equalizer characteristic for the A-mode frequency-modulated luminance signal (FM luminance signal). In this example, a peaking characteristic I having a peak level frequency (peaking frequency) of about 4 MHz and a peak level frequency Combines the peaking characteristic II of about 5.5 MHz to obtain the equalizer characteristic indicated by the solid line III as a whole. A recording medium having the characteristics shown by the solid line in FIG.
Whole is recorded in the frequency spectrum, by passing the equalizer circuit having equalizer characteristic shown by the solid line III the FM luminance signal Y _A obtained by reproducing it in Graph 1 (D), reproduced FM luminance signal is shown in As shown in FIG. 9E, a characteristic in which the vicinity of the FM carrier is emphasized is provided.

On the other hand, the frequency characteristic of the reproduction output on a high-performance recording medium capable of recording and reproducing a video signal in the high image quality mode (B mode) and having a wide range of recordable and reproducible frequencies is as shown by a broken line in FIG. 2 (C). and if the second view (B) FM luminance signal from the video signal of B mode such frequency spectrum shown in Y _B of the reproduced high-performance recording medium is separated waves, the solid line in the FIG. 2 (D) When passed through an equalizer circuit having an equalizer characteristic indicated by III, as described above, FM
Since the lower band wave lower than the carrier wave is emphasized, an inversion phenomenon easily occurs, the frequency characteristic of the reproduced luminance signal is poor, and an unnatural reproduced image is obtained.

Therefore, when the recording mode of the reproduced FM video signal is the B mode, the equalizer circuit has a peaking characteristic IV near a peak level frequency of 5.5 MHz and a peak level frequency around 7.5 MHz as shown in FIG. Is switched to an equalizer characteristic as indicated by a solid line VI obtained by synthesizing the peaking characteristic V with the peaking characteristic V. As a result, the B-mode reproduced FM luminance signal is provided with an optimum equalizer characteristic and is extracted from the equalizer circuit.

First Embodiment FIG. 1 is a block diagram showing a first embodiment of a main part of the apparatus of the present invention. Reproduced FM luminance signal from the HPF8 that incoming in the figure, the terminal 19, if it is recorded in A mode (standard definition mode) on a magnetic tape, as shown in Y _A in FIG. 2 (A) has a frequency spectrum, also in the case which has been recorded in the B-mode (high image quality mode), the second view (B) to have a frequency spectrum as shown by Y _B is as described above is there. This reproduced FM luminance signal is supplied to the FM equalizer 20.

The FM equalizer 20 is configured to change its equalizer characteristics based on both or one of the A mode discrimination signal from the terminal 21 and the B mode discrimination signal from the terminal 22. The equalizer characteristic of the FM equalizer 20 is a frequency characteristic as shown by a solid line III in FIG. 2 (D) when the reproduced FM luminance signal is in the A mode, and a solid line in FIG. 2 (F) when the reproduced FM luminance signal is in the B mode. The frequency characteristics are selected as shown in VI. Playback from the output terminal 23 of this FM equalizer 20
The FM luminance signal is supplied to a reproduction system after the AGC circuit 11 in FIG.

Next, embodiments of the specific circuit of the FM equalizer 20 shown in FIG. 1 and modifications thereof will be described with reference to FIGS. FIG. 3A shows a specific circuit of the first embodiment of the FM equalizer, and the same components as those in FIG. 1 are denoted by the same reference numerals. In FIG. 3 (A), reproduced FM luminance signal input terminal 19 via a supplied to the base of NPN transistor Q _1, where it is amplified and output to the output terminal 23 from the collector of Q _1.

Recording mode of the input reproduced FM luminance signal in the case of the A mode, the switch circuit SW ₂ and SW ₃ are turned on by the input signal of the terminal 21a and 21b, the switch circuits SW ₁ and SW ₄ are turned off. Therefore, between the collector and the supply voltage + Vcc of the transistor Q ₁ is, the capacitor C _1, a coil L ₁ and the resistor R
Becomes the configuration resistor Ra to the first parallel resonance circuit composed of ₁ are connected in series, and transistors to Q ₁ emitter and between the ground coil L _3, the first consisting of the capacitor C ₃ and resistor R ₃
Is connected in parallel to the emitter resistor Rb, which is equivalent to the absence of the coils L ₂ and L ₄ , the capacitors C ₂ and C ₄ , and the resistors R ₂ and R ₄ .

The frequency characteristic of one of the first parallel resonance circuit and the first series resonance circuit is selected as one of the peaking characteristics shown by broken lines I and II in FIG. The frequency characteristic is selected as the other peaking characteristic. Therefore, the output terminal 23 is connected to the solid line III in FIG.
A reproduced FM luminance signal to which the frequency characteristic indicated by is added is extracted.

On the other hand, the recording mode of the input reproduced FM luminance signal is at a B-mode, the switch circuits SW ₁ and SW ₄ are turned on by the input signal of the terminal 22a and 22b, the switch circuit SW ₂ and SW ₃ are the respective off. Therefore, between the collector and the supply voltage + Vcc of the transistor Q ₁ is, the capacitor C _2, the coil L ₂
And a resistor second resistor Ra to the parallel resonant circuit of which consists of R ₂ is the connected in series, and transistors to Q ₁ emitter and between the ground coil L _4, a second consisting of the capacitor C ₄ and the resistor R ₄ Is connected in parallel to the series resonant circuit, and this is equivalent to the absence of the coils L ₁ and L ₃ , the capacitors C ₁ and C ₃ , and the resistors R ₁ and R ₃ .

One of the second parallel resonance circuit and the second series resonance circuit is selected as one of the peaking characteristics IV and V shown in FIG. 2 (F), and the other resonance circuit is selected as the other peaking characteristic. It is. Therefore, the input reproduction FM luminance signal in the B mode is given an equalizer characteristic indicated by a solid line VI in FIG.

Next, a modified example of the present embodiment will be described. Although the circuit shown in FIG. 3A uses four coils, the coil occupies a large area particularly when high-density mounting is performed. Therefore, an example in which the number of coils is reduced is shown in FIG. In FIG.
The same components as those in FIG. 1A are denoted by the same reference numerals, and description thereof will be omitted. In FIG. 3 (B), a parallel resonance circuit composed of a coil L ₁ ′, a capacitor C ₁ ′ and a resistor R ₁ ′, and a series resonance circuit composed of a coil L ₃ ′, a capacitor C ₃ ′ and a resistor R ₃ ′. Gives A-mode equalizer characteristics,
A B-mode equalizer characteristic is provided by a parallel resonance circuit including L ₁ ′, capacitor C ₂ ′, and resistor R ₂ ′, and a series resonance circuit including coil L ₃ ′, capacitor C ₄ ′, and resistor R ₄ ′. The resonance frequency of these resonance circuits is given by selecting the capacitance value of the capacitor, and the sharpness (Q) of resonance can be set to an appropriate equalizer characteristic by selecting the resistance value.

Next, a second embodiment of the present invention will be described. In the first embodiment, two peaking frequencies are independently set for each of the A and B modes. However, when the A and B modes have the spectrum arrangement as shown in FIGS. 2A and 2B, for example, the peaking characteristic II on the high frequency side in the case of the A mode shown in FIG. The peaking frequency,
The peaking frequency of the low-frequency peaking characteristic IV in the case of the B mode shown in FIG.
Hz) can be. This embodiment is created in view of the above points, and FIG. 4 (A) shows a specific circuit diagram of the second embodiment, and the same components as those in FIG. 3 (A) are denoted by the same reference numerals. And description thereof is omitted.

Figure 4 (A), a by capacitor C ₅ and the coil L ₅ which is connected to the collector of the transistor Q _1, giving peaking frequency of the shared, parallel to the parallel circuit of C _5, L ₅ and a resistor R _5A the switch circuit SW ₅ in the series circuit of a resistor R _5B and the switch circuit SW ₅ that is connected to, Q is changed in the common peaking frequency. In the mode in which the Q at this peaking frequency is smaller, in order to obtain a good reproduction image quality, in both the A and B modes, the terminal 25
The switching circuit SW ₅ is turned on by the higher-mode discrimination signal. Note that the values of the resistors _R5A and _R5B are set to values that give the optimum Q in each mode.

The switch circuit SW ₆ in A mode is turned on, the coil L _6, the series resonant circuit consisting of the capacitor C ₆ and a resistor R _6, the peaking characteristic I is given. On the other hand, in the B mode, the switch circuit SW ₇ is turned on, the coil L _7, wherein the peaking characteristic V is given by the series resonant circuit consisting of the capacitor C ₇ and the resistance R _7.

FIG. 4 (B) is a modification of the second embodiment of the FM equalizer 20 shown in FIG. 4 (A), and the same components as those in FIG. Is omitted. In the circuit shown in FIG. 4 (B), the parallel circuit of a capacitor C ₅ and the coil L _5, the resistance R _5A 'and R _5B' series circuit consisting of the parallel connection and the resistor R _5B 'to the switch circuit SW ₅ 'are connected in parallel.

Thus, in the A and B modes, in a mode where it is desirable that the Q at the common peaking frequency is smaller in order to obtain a good reproduction image quality, the switch circuit SW ₅ ′ is turned on, and the Q is changed. When the larger mode is the better mode, SW ₅ ′ is turned off.

FIG. 4 (C) in yet another variation of the second embodiment of the FM equalizer 20, FIG. 4 (A), (B) in A, the common peaking frequency collector of the transistor to Q ₁ B both modes In the present modification, what is obtained by the parallel resonance circuit of FIG. ₁ is obtained by the series resonance circuit on the emitter side of the transistor Q1. That is, the common peaking frequency coil L _10, capacitor C _10, given by the series resonant circuit consisting of resistor R _10A and R _10B, towards the Q in the peaking frequency is obtained a good reproduction quality when a larger Q the reproduction FM luminance signal when the incoming mode, the switch circuits SW ₁₀ based on an input signal terminal 26 is turned on, disconnecting the resistor R _10B from the circuit.

On the other hand, the transistor on the collector side of Q _1, the switch circuit SW ₈ in A mode is on, SW ₉ is turned off capacitor C _8, a parallel resonant circuit consisting of coil L ₈ and the resistor R _8, wherein the peaking characteristic I is given, also the switch circuit SW ₈ in B mode is turned off, and SW ₉ is turned on the capacitor C _9, wherein the peaking characteristic V is given by the parallel resonant circuit consisting of coil L ₉ and the resistor R _9. It should be noted that the Q of the common peaking circuit may not be switched, and a resistor having a common resistance value that allows practical image quality in each mode may be connected.

Next, a third embodiment of the FM equalizer 20 is shown in FIG. 5 (A), and respective modifications thereof are shown in FIGS. 5 (B) to (E).
In each figure, FIG. 1, FIG. 3 (A), FIG. 5 (A),
The same components as those in (B) are denoted by the same reference numerals, and description thereof will be omitted. The circuits shown in FIGS. 4 (A) to 4 (C) required three coils, but the number of coils was further reduced to two, as shown in FIGS. 5 (A) to 5 (E). Circuit.

FIG. 5 (A) shows a circuit similar to that shown in FIG. 4 (C).
Coil L ₁₁ which is provided on the emitter side of the transistor Q _1,
Obtain a common peaking characteristics in both modes by the series resonant circuit consisting of a capacitor C ₁₁ and resistor R _11, A, B two modes with different alternative peaking characteristic I, switching of peaking frequency and Q of the V, the transistor Q ₁ In the parallel resonance circuit on the collector side. That is, the switch circuit SW ₁₁ is turned on only in A mode, the capacitor C ₁₂ to the A mode, the coil L _12, resistors
A parallel resonance circuit composed of R ₁₂ , capacitor C ₁₃ and resistor R ₁₃ is formed, and the peaking characteristic I is obtained. On the other hand, since the switch circuit SW ₁₁ for B mode is turned off, the parallel resonant circuit of the collector of the transistor Q ₁ is composed only the capacitor C _12, the coil L ₁₂ and resistor R _12, whereby said peaking characteristic V is obtained Can be In the circuit shown in FIG. 5 (A), A, can not be Q switches in B both modes common peaking frequency, for example, similarly to the FIG. 4 (C), a resistor R ₁₁ to divide the other hand Is connected or disconnected by a switch circuit,
Can be switched.

Each modification shown respectively in FIG. 5 (B) ~ (D) are provided A, B both modes common peaking characteristic to the collector of the transistor Q _1, consisting of a capacitor C _14, the coil L ₁₄ and resistor R ₁₄ generated by the parallel resonance circuit, a, Aru another frequency peaking differ B both modes is configured to generate switching a series resonant circuit of the emitter side of Q _1. That is, the series resonant circuit of the emitter side of the transistor Q ₁ is the case of FIG. 5 (B), the coil L ₁₅ switch circuits SW ₁₂ in A mode is turned on, in series with the resistor R _15, a capacitor C while parallel circuit of _15A and C _15B is the connected configuration, the B mode the switch circuit SW ₁₂ is turned off, the capacitor C _15B is disconnected. In the circuit shown in FIG. 5 (C), a capacitor C _15C and a coil C are provided by a switch circuit SW ₁₃ which is turned on only in the A mode.
A series resonant circuit consisting of L ₁₅ and resistor R _15, only adding a capacitor C _15D in series B mode.

Further, in the circuit shown in FIG. 5 (D), the transistor Q ₁
The circuit on the emitter side, the switch circuit SW _14, B mode switching circuit SW ₁₅ which is turned only to be turned on only A mode, carp L ₁₅ to the A mode, the capacitor C
_A series resonance circuit consisting of _15E and a resistor R _15E
In mode, coil L ₁₅ , capacitor C _15F and resistor R _15F
Is formed. According to the modification shown in FIG. 5 (D), the Q of the resonance circuit on the emitter side can be adjusted in each mode.

In the circuit shown in FIG. 5A, the transistor Q ₁
Although the value of the resistance component that determines the Q of the parallel resonance circuit on the collector side of A is smaller in the case of the A mode than in the case of the B mode, there is a modification in which the value can be determined independently in both modes. This is shown in FIG. Figure 5 in (E), the A mode is connected parallel capacitor C _13A and resistor R _13A is the coil L ₁₂ is the switching circuit SW ₁₆ is turned on, the coil L is switch circuit SW ₁₇ is turned on in the B mode ₁₂ , a capacitor C _13B and a resistor R _13B are connected in parallel.

Next, a fourth embodiment of the FM equalizer 20 is shown in FIG. 6A, and a modified example thereof is shown in FIG. In the embodiment described above, each of the two peaking characteristics used for equalization in both the A and B modes is made by the FM equalizer. However, in the magnetic reproducing apparatus, as shown in FIG. 10, the rotary heads 1, 2 and the rotary transformers 3, 4
, And the capacitors Ca, Cb provided at the input stages of the head amplifiers 5, 6, it is possible to perform peaking by so-called head resonance. Therefore,
In this embodiment and its modifications, the head resonance is used for any one of the peaking characteristics in the above equalization.

FIG. 6A shows a circuit of the FM equalizer 20 when the values of the capacitors Ca and Cb are selected so that the peaking characteristic V on the high frequency side in the B mode is provided by head resonance. In FIG. 6 (A), a parallel resonance circuit composed of a capacitor C ₁₆ , a coil L ₁₆ and a resistor R ₁₆ on the collector side of the transistor Q ₁ provides a common peaking characteristic in both A and B modes, and Switch circuit in mode
The emitter side to the resistance R _17A for Q ₁ to SW ₁₈ as an off, the capacitor C _17, to form a series resonant circuit consisting of coil L ₁₇ and resistor R _17B provide the peaking characteristics I. On the other hand, in the B mode, the switch circuit SW ₁₈ is turned on, and the coil L
₁₇ and short-circuit the resistor R _17B to ground, the emitter of the transistor Q ₁ is not a series resonant circuit, the series circuit consisting of resistor R _17A and the capacitor C ₁₇ is connected in parallel configuration to the resistor Rb.

As a result, in the B mode, the circuit shown in FIG. 6 (A) shows the low-frequency peaking characteristic IV or a mere high-frequency emphasis characteristic having a characteristic close to it. Since another peaking characteristic V in the case of the B mode is provided by the head resonance, the peaking at this frequency is not particularly performed in the FM equalizer. Even without be a high frequency emphasis characteristics described above may be switched to the emitter of the transistor Q ₁ so that the circuit structure of only the emitter resistor Rb.

Figure 6 (B) the circuit shown in the A on the emitter side of Q _1, B gives both modes common peaking characteristics, connected in parallel coil L _19, a series resonant circuit consisting of a capacitor C ₁₉ and resistor R ₁₉ to the resistor Rb In the A mode, the switch circuit SW ₁₉ is turned on, and a parallel resonance circuit composed of a capacitor C ₁₈ , a resistor R ₁₈ and a coil L ₁₈ is formed on the collector side of Q ₁ to provide another peaking characteristic of the A mode. Give I On the other hand, since the switch circuit circuit SW ₁₉ when the B mode is turned off, the parallel resonant circuit to the collector of the transistor Q ₁ is not configured, the serial-to-parallel circuit to the resistor Ra of the coil L ₁₈ and the resistor R ₁₈ 6B, the circuit shown in FIG.

Note that instead of the switch circuit SW ₁₉ , a capacitor C ₁₈ ,
By providing the switch circuit so as to short-circuit only across the B mode of the parallel circuit of the resistor R ₁₈ and the coil L _18, the B mode can be stopped even a high frequency emphasis characteristics described above.

In addition, in the A mode, the head resonance suitable for the B mode due to the head resonance emphasizes an unnecessary band, thereby deteriorating the S / N. However, in order to avoid this, FM demodulation is performed from the head amplifiers 5 and 6. In the circuit system up to the device 13, the circuit for inserting a head resonance frequency trapping circuit and a low-pass filter is configured to be inserted only when the reproduced FM luminance signal is in the A mode, thereby enhancing the head resonance. The band can be attenuated. Of course, S /
If N deterioration is practically acceptable, the above-described trap circuit and low-pass filter need not be inserted.

Next, a second embodiment of the main part of the apparatus of the present invention will be described with reference to FIGS. 7 (A) and 7 (B). The FM equalizer 20 shown in FIG. 1 as described in conjunction with FIG. 3 to FIG. 6, a single transistor Q _1, the resonance circuit for obtaining respectively attached peaking characteristic to the emitter side and the collector side And a switch circuit for switching the constant of the resonance circuit. However, as shown in FIG. 7A, the FM equalizer 30 of this embodiment has a cascade connection configuration of a main equalizer 31 and a correction equalizer 32. It has a characteristic in a certain point.

The main equalizer 31 is, for example, a B-mode equalizer, and the correction equalizer 32 corrects the B-mode equalizer characteristics (VI in FIG. 2 (F)) to add an A-mode equalizer characteristic (III in FIG. 2 (D)). Is an equalizer.
As a result, the input reproduction FM luminance signal is transmitted to the main equalizer 31.
And the correction equalizer 32, respectively,
A reproduction FM luminance signal to which an equalizer characteristic for A mode is added is taken out to 33, and an output terminal is output from the main equalizer 31.
In 34, a reproduced FM luminance signal to which a B-mode equalizer characteristic is added is extracted.

FIG. 7 (B) is a circuit diagram of one embodiment of the FM equalizer 30 shown in FIG. 7 (A), and the same components as those in FIG. 7 (A) are denoted by the same reference numerals and description thereof will be omitted. NPN transistor T
While selecting the constant of the resonance circuit on the emitter side of r ₁ and making the peaking characteristic of one of the B modes by the head resonance, an equalizer characteristic for the B mode is created,
Obtaining equalizing characteristics for A mode by adding the correction constant in the resonant circuit of the emitter side and the collector side of the PNP transistor Tr _3. Incidentally, the NPN transistor Tr ₂ and the NPN transistor Tr ₄ is an emitter follower.

Next, a third embodiment of the main part of the device of the present invention will be described with reference to the block diagram of FIG. 8 (A) and the circuit diagrams of FIGS. 8 (B) and (C). 8A to 8C, the same components are denoted by the same reference numerals. The FM equalizer 36 of the present embodiment is configured such that the main equalizer 37 and the correction equalizer 38 are connected in cascade, and the correction equalizer 38 can switch the equalizer characteristics in both modes by a mode discrimination signal from the terminal 39. It is.

FIG. 8B is a circuit diagram of an embodiment of the FM equalizer 36 shown in FIG. 8A. The main equalizer 37 comprises an NPN transistor Tr _5, etc., correction equalizer 38 PNP transistor Tr _6, the collector, the emitter side resonant circuit, consisting of a switch circuit SW _20, SW _21. Switch circuits SW ₂₀ and SW ₂₁ are turned on respectively A mode only. Transistor
The signal extracted from the collector of Tr ₆ is output via the base and emitter of a PNP transistor Tr ₇ which is an emitter follower.

FIG. 8C shows another specific circuit of the FM equalizer 36 shown in FIG. 8A. Figure 8 in (C), the constant of the feedback circuit of the differential amplifier 41 provides both modes common peaking characteristics mentioned above, the next stage of the NPN transistor Tr _7, consisting of the switch circuit SW _22, SW _23, etc. correcting equalizer The characteristic of 38 is switched by switching the external constant of Tr ₇ in both A and B modes. Switch circuit SW ₂₂ is terminal 39
ON only in A mode by signal from a, switch circuit S
W ₂₃ is turned on by a signal from the terminal 39 b B mode only. The equalization by the feedback circuit of the differential amplifier 41 may, of course, be performed by an external constant of the transistor, as in the other embodiments.

In the present invention, the main equalizer and the correction equalizer do not necessarily have to be directly connected in cascade, and modifications such as those shown in FIGS. 9A to 9C are possible. 9 (A) to 9 (C), the same components as those in FIG. 10 are denoted by the same reference numerals, and description thereof will be omitted. 9 (A) to 9 (C), the head 2, the rotary transformer 4, the head amplifier 6, the capacitor Cb,
Illustration of the switch circuit 7 and the like is omitted. Further, in FIGS. 9B and 9C, the subscripts a and b indicate circuits for the A and B modes. As shown in FIG. 9 (A), the main equalizer 43 (3
1, 37) and the correction equalizer 44 (32, 38).
And other circuits may be inserted. When the AGC circuit 11 is built in the head amplifier IC,
By mounting the circuit before the GC circuit 11 around the drum and mounting the circuit after the correction equalizer 44 in another place, the size of the circuit mounted around the drum becomes smaller, so this circuit is mounted in a small place. There is an advantage that it becomes easier.

Particularly, when different outputs are provided in each mode as shown in FIG. 7 (A), as shown in FIG. 9 (B), the circuits after the limiters 12a and 12b are also different circuits in both modes. Each equalizer output terminal may be connected to a subsequent circuit of each mode. In this case, all circuits after the limiter do not have to be separate circuits. For example, as shown in FIG. 9 (C), in order to share the FM demodulator 13, a switch circuit 45 is provided on the input side thereof. Alternatively, the LPFs 14a and 14b and the de-emphasis circuits 15a and 15b may be separately provided, and their outputs may be switched by the switch circuit 46.

Note that the present invention is not limited to the above embodiment, for example, the frequency-modulated video signal is not limited to the FM luminance signal, and may be, for example, an FM composite color video signal, an FM time-division multiplexed video signal, an FM color signal, or the like. The present invention can be similarly applied to three or more modes. The present invention can be applied to a 4-head VTR other than the 2-head VTR.

Effect of the Invention As described above, according to the present invention, the use of a recording medium can be improved by high-density recording and reproduction using a rotary head because of having a rotary transformer. The equalizer circuit adjusts the carrier frequency of the frequency-modulated video signal to approximately 3.4 MHz at the sync chip level and approximately 4.4 MHz at the white peak level.
Recording mode, and about 5.4 MHz at the sync chip level,
Since an equalizer characteristic according to the recording mode in which the white peak level is approximately 7 MHz is provided, the video signal can be reproduced with good S / N according to the recording mode. Further, since the limiter circuit is provided, the upper band wave lost in the recording / reproducing process can be substantially reproduced, and as a result, inversion phenomenon caused by imbalance between the upper band wave and the lower band wave can be prevented. S / N can be improved. In addition, since a low-pass filter is provided, the carrier frequency component can be suppressed and the S / N of the reproduced signal can be improved. Further, since the de-emphasis circuit is provided, it has features such as that triangular noise accompanying frequency modulation recording / reproduction can be reduced and S / N of a reproduced video signal can be improved.

[Brief description of the drawings]

FIG. 1 is a diagram showing a first embodiment of a main part of the present invention, FIG. 2 is a diagram showing a frequency spectrum for explaining the present invention,
3 to 6 are diagrams showing each embodiment of a specific circuit of the circuit shown in FIG. 1 and its modification, and FIGS. 7 (A) and 7 (B).
8 is a block diagram of a second embodiment of a main part of the present invention and a circuit diagram of one embodiment thereof, and FIGS. 8A to 8C are block diagrams of a third embodiment of the main part of the present invention, respectively. FIGS. 9A to 9C are block diagrams showing other modified examples of the present invention, and FIG. 10 is a block diagram showing an example of a conventional device. is there. 19: Reproduction FM luminance signal input terminal, 20, 30, 36 ... FM equalizer, 21, 21, 21a, 21b ... A mode discrimination signal input terminal, 22,
22a, 22b ... B mode discrimination signal input terminals, 23, 33, 34 ...
Output terminal, 31, 37, 43 …… Main equalizer, 32, 38, 44…
… Correction equalizer, 39… Mode discrimination signal input terminal.

Claims (3)

(57) [Claims] 1. A carrier frequency of a frequency-modulated video signal,
Frequency-modulated video in one of the recording modes of approximately 3.4 MHz at the sync tip level and approximately 4.4 MHz at the white peak level and one of the recording modes at approximately 5.4 MHz at the sync tip level and approximately 7 MHz at the white peak level What is claimed is: 1. A video signal reproducing apparatus for reproducing a recorded frequency modulated video signal from a recording medium on which a signal is recorded using a common rotary head, comprising: a rotary transformer for transmitting a signal reproduced from the rotary head; The carrier frequency of the frequency-modulated video signal is approximately 3.4 M at the sync chip level as a composite of multiple peaking circuits on the reproduced frequency-modulated video signal that has passed through the rotary transformer.
Hz, a recording mode of approximately 4.4 MHz at the white peak level, and an equalizer circuit for imparting equalization characteristics according to a recording mode of approximately 5.4 MHz at the sync chip level and approximately 7 MHz at the white peak level. A limiter circuit for limiting the amplitude of the reproduced frequency-modulated video signal, a frequency demodulation circuit for performing frequency demodulation on the reproduced frequency-modulated video signal passed through the limiter circuit, and a low-frequency band for limiting a band of an output signal of the frequency demodulation circuit. A video signal reproducing apparatus comprising: a filter; and a de-emphasis circuit that performs de-emphasis on an output signal of the low-pass filter and outputs a reproduced video signal. 2. An equalizer circuit according to claim 1, wherein a part of a constant of said peaking circuit is set to a recording mode in which a carrier frequency of a frequency-modulated video signal is approximately 3.4 MHz at a sync chip level and approximately 4.4 MHz at a white peak level. About 5.
2. The video signal reproducing apparatus according to claim 1, wherein the video signal reproducing apparatus is configured to be shared with a recording mode of 4 MHz and a white peak level of about 7 MHz. 3. An equalizer circuit comprising a cascade connection of a first equalizer circuit section and a second equalizer circuit section, wherein one of the first and second equalizer circuit sections includes a frequency-modulated video signal. Equalizer characteristics common to the recording mode where the carrier frequency of the sync chip level is approximately 3.4 MHz and the white peak level is approximately 4.4 MHz, and the recording mode where the sync chip level is approximately 5.4 MHz and the white peak level is approximately 7 MHz 2. The video signal reproducing apparatus according to claim 1, further comprising: