JP2000021100A - Crosstalk canceling circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To permit simultaneous reproduction at the time of recordings by coupling recording currents to be supplied to recording heads with reproducing currents to be outputted from reproducing heads in a matrix form to reduce crosstalk. SOLUTION: The crosstalk canceling circuit 13 provided among a rotating head drum device 1, recording amplifiers 11 and reproducing preamplifier 12 couples recording currents from the recording amplifiers 11 to recording heads 7 with reproducing currents from reproducing heads 8 to the reproducing preamplifiers 12 in a matrix form. That is, twisted pair lines for recording currents A, B and parallel orthogonal coupling lines a, b orthogonal to the twisted pair lines are coupled with each other in a matrix form. Then, the twisted pair lines A, B and the orthogonal coupling lines a, b are provided so that the lines A, B and the lines a, b respectively pass on the surface side and the back side of a substrate 14 and intersection parts with the lines A, B appear on the surface of the substrate 14 in a semicircle shape and the lines a, b straddle the lines A, B. Then, canceling quantities of the crosstalk are adjusted by varying interference quantities while deformingly moving the orthogonal coupling lines a, b on the twisted pair lines A, B two-dimensionally.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a crosstalk canceling circuit for suppressing a recording signal from interfering with a reproduced signal in a recording / reproducing apparatus having a rotating head drum for simultaneously reproducing during recording.

[0002]

2. Description of the Related Art Broadcast and professional VTRs, data recorders, and the like perform simultaneous reproduction during recording in order to minimize recording errors. That is, a recording head and a reproducing head are independently provided on the rotating head drum, and signals recorded on the magnetic tape by the recording head are simultaneously reproduced by the reproducing head to monitor a recording state.

A problem that arises when simultaneous reproduction is performed during recording is crosstalk between a recording signal and a reproduction signal in a head of a rotary head drum, a rotary transformer, and a signal transmission line. Interference with the signal causes an error in the reproduced signal.

Therefore, conventionally, in order to suppress the interference of the recording signal with the reproduction signal, a plurality of the following measures are combined. 1. A playback preamplifier is mounted inside the rotating head drum. 2. A recording amplifier is mounted inside the rotating head drum. 3. Provide a large distance between the recording head and the reproducing head. 4. Apply an electrostatic or electromagnetic shield to the head. 5. In a rotary transformer, the distance between a recording signal and a reproduction signal is increased. 6. Apply an electrostatic shield to the rotary transformer. 7. The transmission level of the reproduction signal is set higher than the recording signal level. 8. As the signal transmission line, a two-core shielded wire or a twisted pair wire is used.

[0005]

However, in recent years, in a small recording and reproducing apparatus such as a digital VTR,
Recommended drum diameter of rotary head drum is 21.4mm
At present, the above countermeasures cannot be taken, so that a small-sized recording / reproducing apparatus cannot perform simultaneous reproduction during recording.

The present invention has been made in view of the above problems, and provides a crosstalk canceling circuit which can effectively suppress the interference of a recording signal with a reproduction signal even in a small recording / reproducing apparatus. An object is to enable simultaneous reproduction at the time of recording.

[0007]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention relates to a recording / reproducing apparatus in which a recording amplifier and a reproducing amplifier are arranged outside a rotary head drum, and a recording current supplied to the recording head is supplied to the reproducing head. The matrix is coupled to the reproduction current output from In this matrix coupling section, the line through which the recording current flows is a twisted pair line, and the line through which the reproduction current flows is a parallel coupling line substantially orthogonal to the twisted pair line.

[0008] Then, in this matrix bonding portion,
By independently moving and adjusting the coupling line on the twisted pair line in two dimensions, it is possible to effectively suppress the interference of the recording signal with the reproduction signal.

[0009]

Embodiments of the present invention will be described below in detail with reference to the drawings.

First, the structure of the rotary head drum device will be described with reference to FIG. In the figure, reference numeral 1 denotes the rotary head drum device 1 as a whole, 2 denotes a fixed drum,
Reference numeral 3 denotes a rotating drum which runs with a magnetic tape wound around a peripheral surface extending over both drums 2 and 3.

The rotating drum 3 is coaxially rotated with respect to the fixed drum 2, that is, a drum shaft 4 is rotatably supported at the center of the fixed drum 2 via a bearing 5. The rotating drum 3 is fixed to the drum shaft 4 at the center.

Reference numeral 6 denotes a drum motor. The drum shaft 4 is directly connected to the drum motor 6. That is, the driving of the drum motor 6 causes the rotary drum 3 to rotate at a high speed integrally with the drum shaft 4. ing.

A recording head 7 and a reproducing head 8 are independently mounted on the rotating drum 3, and recording is performed on the recording head 7 from a recording amplifier disposed outside the rotating head drum device 1 via a rotary transformer 9. An electric current is supplied to perform recording on the magnetic tape, and at the same time, the reproducing head 8
The reproduction current reproduced and output from the rotary transformer 10
The signal is transmitted to a reproduction preamplifier arranged outside the rotary head drum device 1 via the.

Since the rotary head drum device 1 is small in size, a recording amplifier and a reproduction preamplifier cannot be mounted inside the rotary head drum device 1. In other words, the recording amplifier and the reproduction preamplifier cannot be mounted outside the rotary head drum device 1 as described above. Are arranged.

For this reason, in the rotary head drum device 1, crosstalk easily occurs between a recording signal and a reproduction signal in a head, a rotary transformer, and a signal transmission line. It is provided between the device and the recording amplifier and the reproducing preamplifier.

Most of the crosstalk in a small rotary head drum device is electromagnetic coupling, and can be canceled by adding interference signals in opposite phases. However, since a voltage is generated at the time of recording, the electromagnetic coupling does not exist alone but accompanies the electrostatic coupling.

FIG. 2 shows the interference of parallel lines, that is, in this case, a signal current flows through the parallel lines A and B, and the measuring point a is moved on the parallel lines A and B. In this configuration, the cross section of the line is as shown in FIG. 3, and distances between the lines are L ₁ , L ₂ , and L ₃ .

When the measuring point a is moved in the direction of the arrow, the distribution of the magnetic field and the electric field changes as shown in the graph of FIG.
L ₁ and the distance L ₂ becomes zero when equal, L ₁ -L ₂
Since the polarity changes depending on the sign, the amount of interference can be varied between + and-. Although capable of varying the level by L _3, when a is a single wire, the electrostatic coupling level changes.

However, when trying to realize a crosstalk canceling circuit having this configuration, it is difficult to adapt to multi-channel recording and reproduction. That is, for example, in the case of recording / reproducing of four channels, there are 16 combinations, and if the crosstalk cancellation by the above configuration is performed, a large space is required and it is difficult to realize.

Therefore, as shown in FIG. 5, consider a configuration in which the parallel lines are the twisted pair lines A and B, and the coupling line a is orthogonal to these. Here, when the joining line a is moved over the twisted pair lines A and B as shown in (1), (2) and (3), the relative positions are changed as shown in (1), (2) and (3) of FIG. Since the relationship changes, a change characteristic equivalent to the graph of FIG. 4 is obtained. According to this configuration, it is possible to easily adapt to multi-channel recording and reproduction.

FIGS. 7 to 9 show an example of a specific embodiment. FIG. 7 shows an example in which the crosstalk canceling circuit according to the present invention is applied to a rotary head drum device that performs recording and reproduction on four channels, that is, the rotary head drum device 1 includes a recording head 7 and a reproducing head 8. A recording current is supplied to the recording head 7 from a recording amplifier 11 disposed outside the rotary head drum device 1 via a rotary transformer 9 to record on a magnetic tape. At the same time, the reproduction current reproduced and output from the reproduction head 8 is transmitted via the rotary transformer 10 to the reproduction amplifier 12 arranged outside the rotary head drum device 1, and the signal is reproduced.

In this configuration, a crosstalk cancel circuit 13 according to the present invention is provided between the rotary head drum device 1 and the recording amplifier 11 and the reproducing preamplifier 12.

This crosstalk cancel circuit 13
The recording current supplied from the recording amplifier 11 to the recording head 7 is matrix-coupled to the reproduction current output from the reproduction head 8 and transmitted to the reproduction preamplifier 12.

Here, the matrix coupling portion is formed by defining the lines through which the recording current flows as twisted pair lines A and B, and the lines through which the reproduction current flows as parallel orthogonal coupling lines a and b substantially orthogonal to the twisted pair lines A and B. is there.

In this embodiment, since the recording head 7 and the reproducing head 8 are each mounted on the rotary head drum device 4 in a four-channel configuration, four matrix coupling portions are formed at the front portion at 16 locations. Become.

In this configuration, the twisted pair lines A and B are disposed on the front side of the substrate 14, while the orthogonal coupling lines a and b pass through the rear side of the substrate 14 as apparent from FIGS.
A portion that intersects with the twisted pair wires A and B is exposed in a semicircular shape on the surface side of the substrate 14 and straddles the twisted pair wires A and B.

In this configuration, the orthogonal coupling lines a and b
Is deformed and moved two-dimensionally on the twisted pair lines A and B to vary the amount of interference to + and-to adjust the crosstalk cancellation level (this operation is performed while measuring the crosstalk). If the orthogonal coupling lines a and b are parallel lines, the magnetic field coupling is the difference between a and b, but the electric field coupling is also the difference between a and b. Therefore, the orthogonal joining lines a and b are independently twisted pair lines A , B in two dimensions, both the magnetic field coupling and the electric field coupling can be adjusted, and a wideband cancellation is possible. Since the orthogonal coupling lines a and b need to move two-dimensionally as described above, they need to be formed of a soft copper wire or a silver wire that can be plastically deformed.

In the above configuration, since the twisted pair lines A and B are difficult to obtain the positional accuracy, the twisted pair lines A and B may be formed by the wiring pattern of the substrate as shown in FIGS.

In this case, the substrate 14 is a so-called double-sided substrate, and twisted pair wires A and B are formed by a wiring pattern printed on both front and back surfaces of the double-sided substrate 14. It is intended to change to +-. Orthogonal coupling lines a and b
Mounts a semicircular soft copper wire or the like on the substrate 14, mounts the orthogonal coupling lines a and b and the twisted pair lines A and B
The crosstalk cancellation level is +-
Is to be varied.

As described above, the crosstalk canceling circuit according to the present invention reduces the crosstalk by matrix-coupling the recording current with the reproduction current and moving and adjusting the coupling line in the matrix-coupling portion. In this case, since the difference between the recording current and the reproducing current is large, crosstalk between the head, rotary transformer, and signal transmission line can be effectively canceled with a small coupling, and a small coupling is sufficient. Influence on is small and can be ignored.

FIG. 12 is a graph showing the crosstalk canceling effect according to the present invention.
Shows the interference characteristics to the playback signal when set to
The characteristic (a) is a case where the crosstalk canceling circuit according to the present invention is not used, and the characteristic (b) is a case where the crosstalk canceling circuit according to the present invention is used.

As is clear from the above, when the crosstalk canceling circuit according to the present invention is used, an improvement of 30 to 35 dB in a band of 20 MHz is observed as compared with the case where the crosstalk canceling circuit is not used. By effectively suppressing the interference of the recording signal with the reproduction signal, simultaneous reproduction at the time of recording can be performed without any problem.

Although the embodiment of the present invention has been described above, it goes without saying that the present invention is not limited to this example but can take various embodiments.

[0034]

As described above, according to the crosstalk canceling circuit of the present invention, in the recording / reproducing apparatus in which the recording amplifier and the reproducing amplifier are arranged outside the rotary head drum, the head of the rotary head drum, the rotary transformer,
The crosstalk of the signal transmission line can be effectively reduced, so that simultaneous reproduction during recording can be performed even with a small rotating head drum.

[Brief description of the drawings]

FIG. 1 is a vertical sectional side view showing a structure of a rotary head drum device.

FIG. 2 is a perspective view illustrating interference of parallel lines.

FIG. 3 is a sectional view of the same.

FIG. 4 is a graph showing changes in a magnetic field and an electric field.

FIG. 5 is a perspective view illustrating interference of twisted pair wires.

FIG. 6 is a sectional view of the same.

FIG. 7 is a plan view showing an example of an embodiment of a crosstalk canceling circuit according to the present invention.

FIG. 8 is a plan view of the same matrix coupling portion.

FIG. 9 is a longitudinal sectional view of the same.

FIG. 10 is a plan view of a matrix coupling section showing an example in which a twisted pair line is formed by a wiring pattern.

FIG. 11 is a longitudinal sectional view of the same.

FIG. 12 is a graph showing a crosstalk canceling effect according to the present invention.

[Explanation of symbols]

1 ‥‥ rotating head drum device, 7 ‥‥ recording head, 8 ‥
{Reproduction head, 11} Recording amplifier, 12} Reproduction preamplifier, 13} Crosstalk cancel circuit, A, B
{Twisted pair wires (lines through which recording current flows) a, b}
Orthogonal coupling line (line through which reproduction current flows)

Claims (3)

[Claims] 1. A recording / reproducing apparatus in which a recording amplifier and a reproducing amplifier are arranged outside a rotary head drum, wherein a recording current supplied to the recording head is matrix-coupled to a reproducing current output from the reproducing head to reduce crosstalk. A crosstalk canceling circuit, which enables simultaneous reproduction during recording. 2. The cross according to claim 1, wherein in the matrix coupling section, a line through which a recording current flows is a twisted pair line, and a line through which a reproduction current flows is a coupling line substantially orthogonal to the twisted pair line. Talk cancel circuit. 3. The crosstalk canceling circuit according to claim 2, wherein said twisted pair wire is formed by a wiring pattern printed on the front and back surfaces of a double-sided board.