Communications: electrical – Systems – Selsyn type
Reexamination Certificate
1998-06-02
2001-02-27
Lefkowitz, Edward (Department: 2736)
Communications: electrical
Systems
Selsyn type
C340S315000, C307S105000, 36
Reexamination Certificate
active
06194996
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a transfer apparatus and a transfer method, using power lines for separating waveform signals (information signals) from waveform signals superposed over sine wave signals (carrier wave signals), also relates to a signal superposing apparatus and a signal superposing method for use in a power line carrier system for communicating information signals using power signals on AC power lines as carrier wave, and more particularly to a transfer apparatus and a transfer method using power lines effective in code division multiple access (CDMA).
BACKGROUND OF THE INVENTION
In a power line carrier system or the like, with sine wave power signals being used as carrier wave, information signals are superposed over the power signals and sent out. At the receiving end, the information signals superposed over the power signals are separated with a filter or the like. In separating information signals from electric signals in this process, though the phase of separated signals varies with the characteristics of the filter, it poses no essential problem when the information signals are analog audio signals or the like.
Now, when a digital signal is sent by the power line carrier system, the phase of the digital signal will be shifted at the receiving end, and the waveform will be distorted on the time axis. Where pulse signals are to be sent by pulse code modulation (PCM), even if the waveform is distorted on the time axis, such distortion can be coped with by newly generating pulse signals at the receiving end.
However, where signals undergo spread spectrum multiplexing, no pulse signals can be newly generated at the receiving end unlike in a PCM system. This waveform distortion on the time axis in signal reception poses a grave problem in the spread spectrum system.
Furthermore, one of the known power line carrier systems is to superpose information signals over a carrier wave consisting of sine wave power signals on AC power lines, and this is used in relatively simple communication of control signals, such as on-off control of a motor or the like, and of audio and other analog signals or digital signals by a PCM system. Many of the signal superposing systems used therein have a coupling transformer between the superposing system and the AC power lines to superpose information signals over power signals. As a result, the phase and other aspects of the information signals are varied by a kind of filter formed by this coupling transformer and the AC power lines, and this is known to invite waveform distortion of the superposed information signals.
However, even though information signals are subjected to such waveform distortion, no essential trouble would occur to control signals or analog signals referred to above because of the character of their processing. Nor would digital signals in a PCM system be subject to so serious disturbance, thanks to signal regeneration or otherwise at the receiving end, that signal errors are uncorrectable. Therefore, they created no system problem.
On the other hand, the progress of multiple access technology in recent years has led to studies on various multiplexing systems, and particular interest is focused on CDMA by spread spectrum multiplexing, which permits multiplexing with a simpler configuration than frequency division multiplexing or time division multiplexing.
However, if it is attempted to communication such CDMA-multiplexed information signals by the above-mentioned power line carrier system, inverse spreading on the receiving side is made difficult by the waveform distortion of signals, which are thereby prevented from demodulation. In other words, as it is impossible, in a power line carrier system using power signals on AC power lines as carrier wave over which information signals are superposed, to superpose information signals of a desired waveform (e.g. a stepwise waveform as illustrated in
FIG. 20
) without distortion, it is impossible to accomplish communications by CDMA.
An object of the present invention, undertaken to solve the problem pointed out above, is to provide a transfer apparatus and a transfer method, using power lines, for separating waveform information signals, on the time axis without distorting their waveform, from synthesized signals formed by superposing any desired waveform signals over sine wave signals.
Another object of the invention is to provide a transfer apparatus and a transfer method, using power lines, permitting superposition of information signals of a desired waveform over power signals on AC power lines.
SUMMARY OF THE INVENTION
According to the present invention, there is provided a transfer apparatus comprising:
a filter for extracting sine wave signals from sine wave signals over which waveform signals are superposed;
phase shifting means for giving a phase shift to the sine wave signals extracted by the filter;
phase converting means for generating sine wave signals before the superposition of the waveform signals by adding sine wave signals extracted by the filter and sine wave signals to which a phase shift has been given by the phase shifting means; and
subtracting means for extracting waveform signals by subtracting the sine wave signals generated by the phase converting means from the sine wave signals over which the waveform signals are superposed.
According to the invention, there is provided a transfer method whereby sine wave signals are extracted from sine wave signals over which waveform signals are superposed; a phase shift is given to the extracted sine wave signals; sine wave signals before the superposition of the waveform signals are generated by adding sine wave signals extracted with the filter and sine wave signals to which a phase shift has been given; and waveform signals are extracted by subtracting the generated sine wave signals from the sine wave signals over which the waveform signals are superposed. Since waveform signals are extracted by generating sine wave signals having no phase shift from the original sine wave signals, the waveform signals can be extracted with no distortion on the time axis.
A preferred embodiment of the invention can be simply configured because the phase shifting means consists of either a differentiating circuit or an integrating circuit.
A transfer apparatus using a power line according to the invention is a signal superposing apparatus for superposing information signals over power signals on AC power lines, characteristic in that it has circuit elements obtained by using a self inductance and the mutual inductance of a transformer connected to the AC power line.
Another method according to the invention is a signal superposing method for superposing information signals over power signals on AC power lines whereby the information signals are given to the secondary the current i
1
of a transformer, of which the primary side voltage e
0
is represented by an expression including a term of L
1
(di
0
/dt) and a term of M(di
1
/dt) and the secondary side voltage e
1
is represented by an expression including a term of M(di
0
/dt) and a term of L
2
(di
1
/dt) wherein:
L
1
is the primary side self inductance of the transformer connected to the AC power line; L
2
, the secondary side self inductance of the transformer; M, the mutual inductance of the transformer; e
0
, the primary side voltage of the transformer; e
1
, the secondary side voltage of the transformer; i
0
, the primary side current of the transformer; and i
1
, the secondary side current of the transformer.
The invention involves circuit elements obtained by using a self inductance and the mutual inductance of a transformer connected to AC power lines. Thus the circuit configuration can take account of the impedance of this transformer.
In a preferred embodiment of the invention, the circuit elements consist of an impedance Z
1
and an impedance Z
2
connected between AC power lines so as to divide a power signal voltage, and a voltage source connected between the point of voltage division by the impedances Z
1
and Z
2
and ei
Kawashima Mitsusato
Okazaki Hideaki
Goins Davetta
IBIDEN Industries Co., Ltd.
Lefkowitz Edward
Pillsbury Madison & Sutro LLP
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