Dynamic magnetic information storage or retrieval – General recording or reproducing – Signal switching
Reexamination Certificate
1998-06-04
2001-01-16
Faber, Alan T. (Department: 2753)
Dynamic magnetic information storage or retrieval
General recording or reproducing
Signal switching
C066S208000, C066S208000
Reexamination Certificate
active
06175461
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a signal reproduction apparatus and method in which a signal transmission between a rotary side and a fixed side of a rotary head apparatus is carried out via a rotary transformer and in particular, to a signal reproduction apparatus and method involving a rotary drum having a reproduction amplifier.
2. Description of the Prior Art
In a DAT (digital audio tape recorder), VTR, and the like, a so-called helical scan type rotary head apparatus is known.
FIG. 1
shows a brief configuration of such a helical scan type rotary head apparatus as an example, including a rotary drum
51
and a fixed drum
52
. A magnetic head
53
for recording and reproduction is arranged so as to be exposed through a window
54
at the outer circumference of the rotary drum
51
.
FIG. 2
shows a guide running state of a magnetic tape
55
. The magnetic tape
55
is guide and driven to run in an inclined direction along the outer circumference of the rotary drum
51
and the fixed drum
52
. The magnetic head of the rotary drum
51
carries out recording/reproduction while scanning the magnetic tape
55
in an inclined direction with respect to the tape running direction.
Transmission of a recording/reproduction signal for the recording/reproduction head of the rotary drum is carried out via a rotary transformer. A recording output amplifier and a reproduction initial stage amplifier are normally arranged outside of the drum.
FIG. 3
is a block diagram showing a circuit for connection between the recording/reproduction head of the rotary drum and the recording/reproduction amplifier. In
FIG. 3
, reproduction heads
61
,
62
arranged at the rotary side such as the aforementioned rotary drum are respectively connected via windings
71
,
72
of the rotary transformer
70
to reproduction initial stage amplifiers
81
,
82
of the fixed side, whereas recording heads
63
,
64
of the rotary side are respectively connected via windings
73
,
74
of the rotary transformer
70
to recording amplifiers
83
,
84
of the fixed side. It should be noted that in
FIG. 3
, each of the windings of the rotary transformer
70
is denoted by a reference numeral having a subscript “a” for the fixed side and a subscript “b” for the rotary side.
FIG. 4
is a cross sectional view showing the rotary transformer
70
as an example including a fixed side core
70
a
and a rotary side core
70
b
which are arranged to oppose each other via a clearance. Each of the cores, as shown in
FIG. 5
, has a number of concentric circular grooves
76
corresponding to a number of recording/reproduction channels formed on the opposing sides. The windings
71
b
to
74
a
are mounted in the grooves of the fixed side and the windings
71
b
to
74
b
are mounted in the grooves of the rotary side. In the rotary transformer
70
having the aforementioned configuration, the clearance present between the cores
70
a
and the
70
b
causes a large transmission loss compared to a transformer having no clearance.
The transmission loss of this rotary transformer
70
results in a reduction of a weak reproduction head output signal, which in turn reduces the signal ratio with respect to an amplifier noise, so-called SN ratio, deteriorating the quality of the amplifier output signal.
Next,
FIG. 6
shows a circuit configuration equivalent to a circuit from the reproduction head to the reproduction initial stage amplifier. A signal source
81
represents a reproduction head electro motive force voltage v
1
, and a coil
82
represents a head inductance L. A capacitor
83
represents a capacity C as a total of the amplifier input capacity, the wiring capacity, and the rotary transformer capacity. A resistor
84
represents a resistance component in parallel to the head L in addition to a parallel synthesis value R of a damping resistance. These are connected to an input side of the reproduction initial stage amplifier
85
.
As is clear from this
FIG. 6
, the head inductance L and the capacity C at the amplifier input terminal constitute a low pass filter. This low pass filter brings about a cut-off frequency &ohgr;
0
having a characteristic as shown in
FIG. 7
which determines an upper limit of a frequency band of this system. It should be noted that the aforementioned cut-off frequency &ohgr;
0
is, for example, as follows:
&ohgr;
0
=1/(LC)
The capacity C obtained at the amplifier input side includes an input capacity of the amplifier itself to which is also added a capacity parallel to the windings of the rotary transformer as well as the winding capacity between the head and the rotary transformer and between the rotary transformer and the amplifier, which may be greater than the input capacity of the amplifier itself, limiting the frequency band.
To cope with this, there is a case when the reproduction initial stage amplifier is provided on the rotary drum.
This make it possible to eliminate attenuation of the reproduction signal due to the aforementioned loss in the rotary transformer as well as to reduce the capacity of the amplifier input side, extending the frequency band.
That is,
FIG. 8A
shows a case when a reproduction initial stage amplifier
104
is provided at the fixed side. In this case, between a reproduction head
101
and a reproduction initial stage amplifier
104
, there are connected in parallel the rotary transformer
102
and a cable
103
.
FIG. 8
B shows a case when a reproduction initial stage amplifier
112
is provided at the rotary side. In this case, a reproduction head
111
is provided in the vicinity of a reproduction initial stage amplifier
112
, in which the amplifier input side has a capacity which is almost determined by the input capacity of the amplifier itself, increasing the cut-off frequency of the low pass filter, which in turn extends the frequency band. The output of the reproduction initial stage amplifier
112
is fed to the rotary transformer
113
and via a cable
114
to the next stage amplifier.
In the aforementioned case when the reproduction initial stage amplifier is provided at the rotary side, it is necessary that the amplifier operation power source power be supplied to the rotary drum side. For this, there is a known technique for transmitting power via the rotary transformer.
In this case, as shown in
FIG. 9
, a power transmission channel is added besides the recording/reproduction channels. That is, a power signal from a power supply driver
121
is supplied via windings
122
P of a rotary transformer
122
to a rectifier circuit
123
for power supply via a smoothing voltage stabilizing block
124
to a reproduction initial stage amplifier
126
. The reproduction initial stage amplifier
126
amplifies a reproduction signal from a reproduction head
125
and transmits the amplified signal via the rotary transformer
122
to the fixed side.
FIG. 10
shows a configuration example of the power supply driver
121
shown in FIG.
9
. Power from an AC power source
131
is supplied via a CMOS driver circuits
132
and
133
to the fixed side winding of the rotary transformer. Respective portions a to e in
FIG. 10
have signal waveforms as shown respectively in
FIG. 11A
to FIG.
11
E.
FIG. 11F
shows a push-pull output from the two CMOS driver circuits
132
and
133
supplied to the fixed side winding of the rotary transformer, which is equivalent to a difference between the aforementioned signals c and e, i.e., c-e.
However, the configuration as shown in
FIG. 9
has a problem that a signal in the power transmission channel, passing through the rotary transformer windings or air, reaches the recording/reproduction signal system, lowering the signal noise ratio. Especially, this significantly affects the reproduction head output which is a weak signal.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a signal reproduction apparatus and method which enable to prevent adverse affects from the power transmission channel even if the reproduction initial
Fukuda Shinichi
Kawakubo Toshihiro
Okazaki Masanori
Suzuki Masahiro
Faber Alan T.
Maioli Jay H.
Sony Corporation
LandOfFree
Rotary head block with rotary transformer having separate... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Rotary head block with rotary transformer having separate..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Rotary head block with rotary transformer having separate... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2546448