Optical communications – Multiplex
Reexamination Certificate
2001-06-27
2004-06-22
Phan, Hanh (Department: 2633)
Optical communications
Multiplex
C398S079000, C398S075000, C398S076000, C398S082000, C398S091000, C398S098000, C398S102000, C398S140000, C398S141000, C398S161000, C398S163000, C398S182000, C398S183000
Reexamination Certificate
active
06754448
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to multiplex transmission apparatuses for optically transmitting a plurality of signals and, more specifically, to a multiplex transmission apparatus that converts a plurality of the same or similar signals varied in phase into optical signals and multiplexes these signals for transmission through a single optical fiber.
2. Description of the Background Art
FIG. 15
is a block diagram showing the structure of a conventional multiplex transmission apparatus. In
FIG. 15
, the multiplex transmission apparatus includes first and second multiplexers
15011
and
15012
, first and second optical transmitters
15021
and
15022
, an optical multiplexer
1503
, an optical transmission path
1504
, an optical separator
1505
, first and second optical receivers
15061
and
15062
, a delay controller
1507
, and a multiplexer
1508
.
The operation of the above structured multiplex transmission apparatus is described. The first and second multiplexers
15011
and
15012
each multiplex a plurality of electrical signals externally supplied (for example, RF signals received by an antenna), and then outputs the resultant signal.
Assume herein that the electrical signals supplied to the first and second multiplexers
15011
and
15012
are equal in signal parameter such as frequency, modulation scheme and modulation information, but different in phase. One example of such signals are those outputted from the same signal source but having different phases because they respectively reached the first and second multiplexers
15011
and
15012
at different times.
In
FIG. 15
, the first and second multiplexers
15011
and
15012
are each supplied with two electrical signals. The first multiplexer
15011
is supplied with a first signal (hereinafter, first main element signal) Sa having a frequency fa and a phase angle
0
and a second signal (hereinafter, second main element signal) Sb having a frequency fb and a phase angle
0
. The second multiplexer
15012
is supplied with a first signal (hereinafter, first sub-element signal) Sa having the frequency fa and a phase angle+&tgr;
1
(phase delayed by &tgr;
1
) and a second signal (hereinafter, second sub-element signal) Sb having the frequency fb and a phase angle−&tgr;
2
(representing phase advanced by &tgr;
2
). Note that the first main element signal and the first sub-element signal are hereinafter collectively referred to as first element signals, while the second main element signal and the second sub-element signal are as second element signals.
In
FIG. 15
, the above signals are represented as follows: the first main element signal as Sa@fa(
0
), the second main element signal as Sb@fb(
0
), the first sub-element signal as Sa@fa(&tgr;a), and the second sub-element signal as Sb@fb(&tgr;b). The mark “@” is an identification mark with a signal name placed therebefore and signal parameters placed thereafter for indicating attributes. Placed as the signal parameters are the frequency and the phase angle, which is enclosed in parentheses.
Note that the above phase angles can be converted into propagation delay times, and therefore are treated herein as equivalent thereto. Also, the first and second main element signals are hereinafter collectively referred to as a main signal group, while the first and second sub-element signals are as a sub-signal group.
The first optical transmitter
15021
, provided correspondingly to the first multiplexer
15011
, converts the main signal group outputted from the first multiplexer
15011
into a first optical signal having a wavelength &lgr;
1
. Similarly, the second optical transmitter
15022
, provided correspondingly to the second multiplexer
15012
, converts the sub-signal group outputted from the second multiplexer
15012
into a second optical signal having a wavelength &lgr;
2
.
The optical multiplexer
1503
multiplexes the optical signals outputted from the first and second optical transmitters
15021
and
15022
, and sends out the resultant optical signal to the optical transmission path
1504
. The optical separator
1505
separates the optical signal coming through the optical transmission path
1504
into two, based on the wavelength. The separated optical signals are outputted as a first optical signal having the wavelength &lgr;
1
and a second optical signal having the wavelength &lgr;
2
.
The first optical receiver
15061
is supplied with the first optical signal outputted from the optical separator
1505
. The first optical receiver
15061
converts the supplied first optical signal into an electrical signal (main signal group) through square-law detection. Similarly, the second optical receiver
15062
is supplied with the second optical signal outputted from the optical separator
1505
. The second optical receiver
15062
converts the supplied second optical signal into an electrical signal (sub-signal group) through square-law detection.
The delay controller
1507
gives a predetermined time delay &tgr;x to the main signal group outputted from the first optical receiver
15061
, and then outputs the main signal group. The multiplexer
1508
multiplexes the main signal group with the time delay given thereto outputted from the delay controller
1507
and the sub-signal group outputted from the second optical receiver
15062
, and then outputs the resultant signal.
For the above structured multiplex transmission apparatus, how to set the time delay &tgr;x in the delay controller
1507
, and the operational principle and effects of the apparatus in terms of setting the time delay are described below by using an example.
FIG. 16
is one example of application of the present apparatus, schematically illustrating the structure of a receiving system using a phased array antenna. In
FIG. 16
, the system includes first and second antenna elements
16011
and
16012
, first and second transmission paths
16041
and
16042
, a delay controller
1507
, and a multiplexer
1508
.
Here, the first and second antenna elements
16011
and
16012
in
FIG. 16
correspond to the first and second multiplexers
15011
and
15012
in
FIG. 15
, respectively. Also, the first and second transmission paths
16041
and
16042
in
FIG. 16
schematically correspond to a propagation path from the first optical transmitter
15021
to the first optical receiver
15061
and a propagation path from the second optical transmitter
15022
to the second optical receiver
15062
, respectively. The delay controller
1507
and the multiplexer
1508
in
FIGS. 15 and 16
are the same in structure, and therefore provided with the same reference numerals.
The first antenna element
16011
in
FIG. 16
is supplied with signals similar to the first main element signal and the second main element signal supplied to the first multiplexer
15011
in FIG.
15
. The second antenna element
16012
in
FIG. 16
is supplied with signals similar to the second main element signal and the second sub-element signal supplied to the second multiplexer
15012
in FIG.
15
. In other words, the first main element signal and the first sub-element signal are the same signal outputted from the same signal source, but different in phase due to a positional relation among the signal source and the first and second antenna elements
16011
and
16012
. The same goes for the second main element signal and the second sub-element signal.
For example, the first main element signal supplied to the first antenna element
16011
is the first element signal Sa, and so is the first sub-element signal supplied to the second antenna element
16012
. However, the first sub-element signal passes through a propagation path longer than that of the first main element signal, and therefore is delayed in phase by the amount corresponding to the propagation time difference+&tgr;a.
On the other hand, the second main element signal supplied to the first antenna element
16012
is the second element signal Sb, and so is the sec
Matsushita Electric - Industrial Co., Ltd.
Phan Hanh
Wenderoth , Lind & Ponack, L.L.P.
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