Communication systems, sender and receiver

Details Communication systems, sender and receiver Communication systems, sender and receiver

1998-09-23

2003-01-14

Chin, Stephen (Department: 2634)

Pulse or digital communications

Systems using alternating or pulsating current

Plural channels for transmission of a single pulse train

C375S285000, C375S296000, C375S299000, C375S347000, C375S349000, C370S281000, C370S319000, C370S343000, C370S480000, C455S104000, C455S226200, C455S226300

Reexamination Certificate

active

06507622

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to a communication system and more particularly to a communication system via high noise transmission lines of low-voltage power such as an electric wire and its sender and receiver.
BACKGROUND OF THE INVENTION
Such narrow-band noises as distortion and impulse noise in transmission lines are often too great to overlook in the transmission systems. In such transmission systems a diffusion data transmission technique has been used as useful means to combat those noises in the past. The diffusion data transmission technique comprises the sender which diffuses data to send via a transmission line and the receiver which inversely diffuses data received The data transmission system based on that conventional diffusion data transmission is described by the following example of the data transmission system using the existing electric power line, that is, low-tension power line of a 100-volt a. c., 50/60 Hz.
FIG. 15
is a block diagram showing an example of the conventional system of the direct diffusion technique for sending data via the electric power line.
In
FIG. 15
, a sender
100
and a receiver
200
are connected to each other via a transmission line
300
.
The sender
100
is provided with a mixer
110
, a pseudo noise generator
111
, a carrier wave oscillator
112
and an equilibrium modulator
113
. The receiver
200
includes a mixer
210
, a pseudo noise generator
211
, a carrier wave oscillator
212
, an equilibrium modulator
213
and an intermediate frequency band pass filter (IF-BPF)
214
.
Diffusion signals from the pseudo noise oscillator
211
is inputted in the mixer
110
on the sender side as well as input data are inputted in the same
Those two kinds of signals are multiplied and inputted in the next equilibrium modulator
113
The aforesaid carrier wave oscillator
112
generates and inputs a carrier wave in the equilibrium modulator
113
. The equilibrium modulator
113
then modulates the carrier wave with the signal from the mixer
110
(diffused input signal) and sends out the modulated carrier wave without the original carrier wave to the receiver
200
.
In the receiver
200
, the carrier wave oscillator
212
generates a carrier wave with the same frequency as of the carrier wave generated by the carrier wave oscillator
112
on the side of the sender
100
, and inputs it in the equilibrium modulator
213
. Meantime, the pseudo noise generator
211
produces an inversely diffused code with a phase opposite to the diffused code generated by the sender
100
, and inputs it in the equilibrium modulator
213
. Thereby, the equilibrium modulator
213
modulates the carrier wave outputted from the carrier wave oscillator
212
by using an inversely diffused code outputted by the pseudo noise generator
211
. The modulated carrier wave is then outputted to the mixer
210
. The mixer
210
multiplies a modulated signal inputted via the transmission line
300
and a modulated signal inputted from the equilibrium modulator
213
, and then outputs its result to IF-BPF
214
. IF-BPF
214
, which means an intermediate frequency band pass filter, is a filter through which waves in the intermediate frequency band can pass.
Now, supposing that the data signal inputted to the mixer
110
carries a spectrum as shown in FIG.
16
(
a
), the mixer
110
diffuses the spectrum by multiplying the input data signal using the diffused code provided by the pseudo noise generator
111
. A spectrum waveform of an input data signal after the diffusion is shown in FIG.
16
(
b
). The diffused data signal then modulates a carrier wave outputted from the carrier wave oscillator
112
at the equilibrium modulator
112
and outputs the modulated signal onto the transmission line
300
. The phrase diffused code means a code with multiple bits in relation to “1” or “0” as, for example, a 31-bit code like 1111100011011101010000100101100 or 0000011100100010101111011010011.
The following is described in the case that an impulse noise (shaded area indicated in FIG.
16
(
c
)) occurs while data signals are being sent via the transmission line
300
and the receiver
200
is to receive the signals shown in FIG.
16
(
c
).
As mentioned, the carrier wave outputted by the carrier wave oscillator
212
in the receiver
200
is modulated with the inversely diffused code given by the pseudo noise generator
211
at the equilibrium modulator
213
Furthermore, the mixer
210
diffuses the spectrum by multiplying the modulated signal and the diffused data signal obtained via the transmission line
300
. The inversely diffused code is a code that the total bits of the diffused code is “1” against the inputting of “1” if the absolute OR with the diffused code is taken (reversely, the inputting “0” brings the total bits of the diffused code to “0”), that is, the inversely diffused code is a code that the diffused code is turned round.
In the multiplication performed at the mixer
210
, the data signals diffused at the sender
100
will be inversely diffused but will undergo usual diffusion against the impulse noise. Therefore, the spectrum waveform of data signals after the multiplication (that is, an inverse diffusion) is as shown in FIG.
16
(
d
). That is, the data signals are recovered to the original form while the impulse signals generated in transmission are diffused instead so that the level for the data signals gets small immediately. This way, the effect of the impulse signals upon the data signals is alleviated
Needless to say, however, in order to carry out the aforesaid inverse diffusion exactly, it is necessary to exactly synchronize the inputting in the mixer
210
of signals from the transmission line and the inputting of modulated signals from the equilibrium modulator
213
.
As set forth above, the conventional system of sending data by direct diffusion technique alleviates the effects of narrow band noises such as impulse noise as well as distortion on the transmission line caused by equipment connected to the line, (for example, the line noise occurring at the start-up of the compressor in the household refrigerator connected to the low-tension electric power line through the 100 V outlet in the house), by the processing of diffusing and inversely diffusing the spectrum as indicated in FIGS.
16
(
c
) and
16
(
d
).
The technique of diffusing spectrum is described in a book entitled “Spectrum Diffusion Communication Formula” published by Jatech Publishing Co., pages 9 to 28.
The prior art system of sending data by the direct diffusion technique as just outlined is effective in removing the effects of narrow-band noises and line distortion to some extent. But in the prior art, it is impossible to completely get rid of the effects of narrow-band noises and line distortion over the full band of frequencies as in the low-tension power line. That is, in case the line noise or distortion is too strong over the level of input data signals, the conventional diffusion technique is no longer effective enough to reduce those noises or distortion.
And, since the frequencies of the aforesaid diffused code are spread over a wide band the bandwidth occupied by the modulated signals increases. Accordingly a large number of side lobes rises over a wide band as well as a main lobe, and those side lobes consume much energy and keeps down the transmission efficiency As mentioned furthermore, the inverse diffusion requires the synchronizing of signals obtained from the transmission line and signals from the equilibrium modulator. This synchronizing undergoes complicated procedures and costs much when it is carried out through a fairly complicated circuit or program In addition the prior art is not sufficient in synchronizing accuracy and can fail to detect data.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a communication system for transmitting data at a high speed with the data quality kept high by making good use of frequency bands which are free from the effects of narrow band noises or line distortion. It is another

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