Induced nuclear reactions: processes – systems – and elements – Control component for a fission reactor – Flexible control element
Reexamination Certificate
2000-03-29
2004-05-18
Jung, Min (Department: 2663)
Induced nuclear reactions: processes, systems, and elements
Control component for a fission reactor
Flexible control element
C370S342000, C375S146000
Reexamination Certificate
active
06738448
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a spectrum spread communication and in particular to a (multi-rated) multiplexing direct spread spectrum communication having a variable multiplicity in which the transmission power is made constant.
2. Description of the Relates Art
Recently spread spectrum communication systems have attracted attention as new communication systems. The modulation schemes used for general data transmission are narrow band modulation scheme. Although they can be implemented by a relatively small circuit, they have a disadvantage that they are susceptible to multipath phasing and colored noise in a narrow band indoors (offices, factories).
In contrast to this, the spread spectrum communication systems are advantageous in that the above-mentioned disadvantage is overcome since the spectrum of data is spread with a spreading code for transmission in a broad band.
However, high rate data transmission is hard to conduct since the wider band is required for the higher data transmission rate. For example, if data transmission using QPSK (Quadrature Phase Shift Keying) scheme by spreading data with a 11 chips is contemplated, 22 MHz band is required for 2 Mbps data transmission. 110 MHz band is required for data transmission at a rate of 10 Mbps.
Further, regulation of bands in which radio wave transmission is permitted also makes it harder to conduct high rate data transmission.
Accordingly, in order to conduct high rate transmission in a restricted band, a multiplexing scheme in which spread signals are delayed (hereinafter referred to as “delay multiplexing scheme) is proposed (refer to Japanese Laid-Open Patent Publication No. 9-55714).
Use of this scheme makes it possible to conduct high rate transmission in a restricted band. If the scheme which is disclosed in the cited publication No. 9-55714 is used for the former example (2 Mbps data, 22 MHz band), duplexing and quintuplexing in the same band enables data transmission at 4 and 10 Mbps, respectively.
FIG. 1
is a block diagram showing an exemplary circuit used for heretofore proposed delay multiplexing scheme.
In
FIG. 1
, data which is generated by a data generating portion
110
is differentially coded by a differential encoding portion
111
and then parallel-converted into numbers to be multiplexed by an S/P converting portion
112
.
Subsequently, the parallel data is spread by being multiplied by a PN code from a PN generator
114
by respective multiplying portions (
113
-
1
through
113
-
4
) and then delayed by respective delay elements (
115
-
1
through
115
-
4
).
Then, the delayed data are combined into multivalued digital signals by a combiner (frequency combining device)
116
. The digital signals are modulated by an oscillated signal from an oscillator
120
in a modulator
119
. The signal is transmitted via a frequency converting portion
122
and power amplifier
123
.
As a result, high rate data transmission in a limited band is made possible.
In a telecommunications system using such a spectrum spreading, the transmission signal assumes +1 or −1, and the multiplexed signal assumes multivalue in the multiplex part. For example, the quintuplexed signal assumes values of −5, −3, −1, 1, 3, 5.
This is shown in FIG.
2
. As shown in
FIG. 2
, the multiplexed operation values differ largely in simplex and multiplex parts.
On the other hand, in the communication system, the signal, the frequency of which is converted to a radio frequency range is usually transmitted. In this case, the operation value assumes 1 and −1 in the simplex part and −5, −3, −1, 1, 3, 5 in the quintuplex part, so that the transmission outputs are not identical in the simplex and multiplex parts.
For the spread spectrum communications in Japan, the communication system using ISM (Industrial, Scientific and Medical) band is permitted as special low power communication system in an assigned band in Japan. A standard RCR-STD-33 (RCR: Research and Development Center for Radio System) is established.
In this standard, usable bands, physical specifications such as allowed power are determined. As to transmission power, it is regulated that the filed transmission power should be kept except for several tolerances.
Accordingly, there is the risk of transmission of the power exceeding the standards if the signal as multiplexed is amplified with the same amplification and is output.
It is also preferable for a high power amplifier in a transmitter system and for an amplifier in a receiver that the power is equal in the simplex/multiplex parts. Use of the system which can not satisfy these requirements provides problems.
The other circuit systems in the communication system in interest are shown in
FIGS. 3 and 4
.
The differences between the circuits of
FIGS. 1 and 3
reside in the difference in the multiplication and in that detection and control portion
121
c
and gain-variable amplifier
121
are additionally provided in the latter circuit.
FIG. 4
shows a variation of the configuration of
FIG. 3
for conducting the spreading, delaying and adding operations in a digital manner and is substantially identical with the configuration of
FIG. 3
except that the signal is delay-multiplexed by means of multipliers
113
′-
1
through
113
′-
5
, delay elements
115
′-
1
through
115
′-
5
and operating portions
117
, and is thereafter D/A converted by a D/A convertor
118
and is input to a modulator
119
.
As shown in
FIGS. 3 and 4
, some communication systems have a gain-variable amplifier
121
, the gain of which is changed in response to a signal from the detection and control portion
121
c
which detects the power of the transmission system for controlling the transmission output to a constant output.
The gain-variable amplifier
121
is disposed at the succeeding stage of the modulator
119
for reducing or eliminating variations of elements in the system such as lowering of output which may be caused by variations in characteristics such as temperature characteristics among the elements and aging of elements.
The detection and control portion
121
c
usually determines the power of RF or IF signal after the modulator
119
as a signal to be controlled for controlling the gain-variable amplifier
121
to keep the power of the signal after detection in response to determined power.
Since the control operation inherently contemplates to absorb the variations among systems, the time constant of integration is set comparatively longer so that the characteristics will not be varied due to noise. The characteristics when a signal having the simplex/multiplex part is input to this circuit is shown in FIG.
5
.
FIG.
5
(A) shows the changes in the output power on the input side of the gain-variable amplifier
121
. FIG.
5
(C) shows the output when the gain is variably changed. FIG.
5
(B) shows the control voltage when the above-mentioned time constant of integration is set comparatively longer.
As shown in FIG.
5
(C), there is a problem that in the transient period, the transmission power will largely increase by the amount corresponding to the integration interval at the transient although the transmission power is kept constant after the lapse of the considerable period of time.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a direct spread spectrum communication system using a multi-rated delay multiplexing scheme, the multiplicity of which is changed, the system performing control operation as quickly as possible by suppressing the output fluctuation within a narrow range so as to perform constant power transmission.
In accordance with the present invention, there is provided a transmitter for a multi-rated delay multiplexing direct spread spectrum communication system including delay multiplexing means for multiplexing a plurality of series of signals which are obtained by delaying, by a desired number of chips, each of the signals. The signals are directly spread wi
Jung Min
Lee Andy
Sharp Kabushiki Kaisha
LandOfFree
Transmitter and receiver for multi-rated delay multiplexing... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Transmitter and receiver for multi-rated delay multiplexing..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Transmitter and receiver for multi-rated delay multiplexing... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3257897