Miscellaneous active electrical nonlinear devices – circuits – and – Signal converting – shaping – or generating – Synthesizer
Reexamination Certificate
2002-05-10
2003-06-03
Wells, Kenneth B. (Department: 2816)
Miscellaneous active electrical nonlinear devices, circuits, and
Signal converting, shaping, or generating
Synthesizer
C327S100000, C327S165000, C327S299000
Reexamination Certificate
active
06573763
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a waveform generation apparatus and method for generating, transmitting, and synthesizing plural binary-state signals to generate a multi-valued composite signal and, more particularly, to a waveform generation apparatus having a construction for eliminating an adverse effect of phase differences among the plural binary-state signals on the multi-valued composite signal.
BACKGROUND OF THE INVENTION
In recent years, high-density recording on recording media has been demanded for an increase in recording capacity, and an improved accuracy of waveform generation has been demanded of waveform generation apparatuses for an increase in recording density.
FIG. 13
is a block diagram illustrating the construction of a conventional waveform generation apparatus. The conventional waveform generation apparatus is provided with a delay circuit
501
comprising plural stages of delay elements which are connected in series; plural (k pieces of) selectors
502
-
1
~
502
-k for selecting the outputs from the respective output stages of the delay elements constituting the delay circuit
501
; a waveform generation circuit
504
for receiving the outputs from the plural selectors; a transmission path
505
for transmitting the outputs from the waveform generation circuit
504
; a waveform synthesis circuit
506
for synthesizing the waveforms of the signals transmitted through the transmission path
505
; and plural (k pieces of) selector control circuits
507
-
1
~
507
-k for controlling the operations of the respective selectors.
Hereinafter, the operation of the conventional waveform generation apparatus constructed as described above will be described.
When a recording/playback medium such as an optical disc is continuously irradiated with a laser beam for the duration of forming recording marks on the medium, heat generated by the irradiation with the laser beam stays on the medium, and the recording marks become larger with time, resulting in tear-drop-shaped marks as shown in FIG.
14
. Thus, the recording/playback medium has a problem caused by the physical phenomenon on the medium.
If data are written on the recording/playback medium in which the problem caused by the physical phenomenon remains, the data cannot be read normally when the medium is played back. Therefore, it becomes necessary to generate a recording waveform so as to correct the physical phenomenon at recording. In the case of an optical disc, for example, a recording waveform is generated so as to frequently turn on and off a laser beam. Thus, it is necessary to generate a recording waveform for correction suited to each recording medium.
When generating such recording waveform for correcting the physical characteristics of a recording medium it becomes necessary to generate reference timings (reference clocks for recording correction) which are finer than a reference clock for writing.
In order to generate reference clocks for recording correction, delayed clocks are generated by delaying a reference clock with the delay circuit
501
, and timings corresponding to the delay amounts are generated. Which delayed clock (delay amount) among the delayed clocks generated in the delay circuit
501
is to be adopted depends on the select state of each of the k pieces of selectors
502
-
1
~
502
-k.
The waveform generation circuit
504
generates plural recording waveforms having different binary states, using the selected clocks having different delay amounts, according to input data. The recording waveforms having different binary states are transmitted through the transmission path
505
. The waveform synthesis circuit
506
synthesizes binary-state signals corresponding to three recording waveforms among the transmitted recording waveforms having different binary states, thereby forming a multi-valued signal for recording. The multi-valued signal is transmitted to a laser diode (not shown) in the subsequent stage, whereby the laser diode is driven and data writing is carried out The reason why the multi-valued signal is not directly transmitted to the transmission path
505
is because data transmission errors due to noise are increased if multi-valued signal is transmitted through the path
505
. So, the binary data (binary-state signals) are transmitted through the path
505
to reduce the errors due to noise. Furthermore, the selector control circuits
507
-
1
~
507
-k control the respective selectors
502
-
1
~
502
-k so as to select the delay amounts according to the setting of waveform generation.
In the conventional waveform generation apparatus constructed as described above, the paths of the respective binary-state signals up to the waveform synthesis circuit
506
will vary, when the signals from the delay circuit
501
are trasmitted through the respective selectors
502
-
1
~
502
-k, the waveform generation circuit
504
, and the transmission path
505
, to the waveform synthesis circuit
506
, resulting in skews among the signals. Therefore, it is necessary to adjust the lengths of the respective paths or the numbers of circuits through which the respective signals pass, thereby to minimize the skews.
Even when the transmission paths or the like are adjusted to minimize the skews, the delay amounts in the respective paths or circuits may vary due to the temperature, voltage, passage of time, or the like, and the variations appear as skews. These skews among the respective signals cause errors in the recording waveforms even though the signal inputs to the waveform generation circuit
504
are accurately controlled using the delay circuit
501
as shown in
FIG. 13
, resulting in errors in th recording marks.
In the conventional waveform generation apparatus and method constructed as described above, although the highly-accurate clocks are inputted to the waveform generation circuit
504
by using the delay circuit
501
and the selectors
502
-
1
~
502
-k, skews are generated due to factors such as the signal transmission paths, use environment, passage of time, and the like, resulting in errors in recording waveforms.
SUMMARY OF THE INVENTION
The present invention is made to solve the above-mentioned problems and has for its object to provide a waveform generation apparatus and method which can reduce errors in recording waveforms due to skews among binary-state signals.
Other objects and advantages of the invention will become apparent from the detailed description that follows. The detailed description and specific embodiments described are provided only for illustration since various additions and modifications within the scope of the invention will be apparent to those of skill in the art from the detailed description.
According to a first aspect of the present invention, there is provided a waveform generation apparatus for transmitting in pieces of binary-state signals, and generating a signal waveform having a multi-valued state by synthesizing the n pieces of binary-state signals, which apparatus comprises: a delay means comprising i pieces of unit delay circuits connected in series, and providing i kinds of delay states by deriving signals from the respective unit delay circuits; k pieces of selection means each selecting one delay state from among the kinds of delay states of the delay means; a waveform generation means for generating n pieces of binary-state signals in the same state, or generating n pieces of binary-state signals having a shape according to recording data supplied from the outside, on the basis of the signals having the i kinds of delay states, which are outputted from the k pieces of selection means, and the recording data supplied from the outside; a transmission means for transmitting the n pieces of binary-state signals generated by the waveform generation means; a waveform synthesis means for generating a signal having multi-valued information from the n pieces of binary-state signals transmitted by the transmission means; a phase difference detection means for detecting phase differences among the n pieces of binary-st
Matsushita Electric - Industrial Co., Ltd.
Nguyen Hai L.
Parkhurst & Wendel L.L.P.
Wells Kenneth B.
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