Optical: systems and elements – Deflection using a moving element – Using a periodically moving element
Reexamination Certificate
1998-11-17
2002-01-08
Pascal, Leslie (Department: 2633)
Optical: systems and elements
Deflection using a moving element
Using a periodically moving element
C359S199200, C359S199200, C359S199200, C359S199200, C359S199200, C455S009000, C455S014000, C455S020000, C455S022000, C455S023000, C455S410000
Reexamination Certificate
active
06337754
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an optical conversion relay amplification system for use as a relay amplification system to cover a dead spot of mobile communications, particularly relates to an optical conversion relay amplification system achievable of economic constitution avoiding a beat noise.
2. Description of the Related Art
Public mobile communications systems (hereafter referred to as mobile communications systems) such as car phone, portable phone system, PHS, paging system, etc. have a base station of the mobile communications (hereafter, base station) linked to a network of the higher rank than public networks, etc. (PSTN and ISDN) by a wire to allow the base station to communicate with mobile stations such as portable phones by wireless systems.
The communicable area (cover area) of the base station by wireless systems is exemplified by some kilometers to some ten kilometers in car phone and portable phone systems and some hundred meters in PHS. In addition, so-called “cellular system” is applied to locate base stations in cover areas like cells in order to keep wider areas effectively using frequencies.
Further, to solve the problem of frequency resource according to an increased demand of radio waves, 1.5 GHz frequency band has been newly assigned to car/portable phone systems for use in addition to the conventional 800 MHz band and 1.9 GHz frequency band has been assigned to PHS for use. Furthermore, 2 GHz band is probably assigned to the portable phone of the next generation. All these band changes to high frequency bands have been carried out for mobile communications.
In these mobile communications systems using the cellular system, generally, wireless communications are done in high quality on outdoor ground, etc. However, even in a cover area of a base station, a radio wave difficultly reaches the inside of a tunnel, an underground shopping center, a basement of a building, and stories above ground of a big building, and thus, any auxiliary means are required to communicate with mobile wireless terminals in these sites by wireless systems.
These areas are named “dead spots”. The dead spot generally appears in radio wave wireless communications not only of mobile communications systems, but also of such as official radios exemplified by police radio, fire radio, and train radio, TV broadcast, and radio broadcast.
As auxiliary means to allow wireless communications in these dead spots, an apparatus named “relay amplification apparatus is generally used”.
The first antenna is located in a site capable of high quality wireless communications with a base station (a broadcast station in broadcasting) and the second antenna is located in a dead spot to amplify a high frequency signal arrived in the first antenna, transmit to the second antenna located in the dead spot by a wire, and radiate the high frequency signal amplified via the second antenna.
By such steps, downlink communications from the base station to the mobile station are kept. Besides, wireless communications in the dead spot become possible by that communications of a downlink line from the base station to the mobile station are established, and also by that in uplink communications from the mobile station to the base station, the high frequency signal radiated by the mobile station is caught by the second antenna to amplify and transmitted to the first antenna with a wire, and the amplified high frequency signal is radiated via the first antenna to output for transmission to the base station.
In addition, on the background of the popularized, wired, high quality communications networks of higher rank such as ISDN, there is a plan that a radio modem is equipped for the dead spot, e.g., underground shopping center where communications have a particularly large demand, directly connected to higher rank network such as ISDN by a wire.
Such radio modem modulates a high frequency signal by a signal inputted from the higher rank network, distributes the high frequency signal from the radio modem to an antenna (said second antenna) located in the dead spot, receives the frequency signal through the antenna, and demodulates the signal from the mobile station to output to the higher rank network.
The conventional relay amplification systems are specifically exemplified by a method in which in a dead spot such as tunnel, a leaky coaxial cable suitable to achieve a linear service area is used as the second antenna to link to the first antenna with a high frequency coaxial cable, and a method in which the second antenna is located in various sites to link to the first antenna with a high frequency coaxial cable.
However, a connection distance between the first antenna and the second antenna requires some kilometers on the situation. In this case, an attenuation (transmission loss) occurs as a problem in the high frequency coaxial cable. Particularly in latest years, frequencies assigned to mobile communications are moved to higher bands to require coaxial cables with a large diameter resulting in a problem of difficulty of laying construction.
Thus, to avoid transmission loss, the optical conversion relay amplification system has been proposed and partially practiced using analog optical fiber transmission technology in replacement to conventionally used the high frequency coaxial cable and leaky coaxial cable having a function as an antenna.
The technical situations of these optical conversions have been detailedly described in reference
1
: Kuganuma et al., “A tunnel booster 1.5 GHz digital mobile communications”, NTT DoCoMo technical Journal, Vol. 2, No. 2 (1994), for example, for relay system, and also for example, reference
2
: Sanada et al., “An optical transmission system for wireless base stations”, National Technical report, Vol. 39, No. 4 (1993) for optical transmission system to link to the system of a base station.
Besides, a detailed description has been given in the following general review about the application of transmission technology using an analog optical fiber for mobile communications: reference
3
, Morita, K., et al., “The new generation of wireless communications based on fiber-radio technologies”, IEICE Trans. Comm., Vol. E76-B, No. 9 (1993), etc.
On the other hand, the following two main systems are conventional to accomplish these analog optical fiber transmission systems in a structure of optical transmission line: a star distribution connection used for point-to-multipoint connection to connect an optical transmitter/receiver of the first antenna side with an optical transmitter/receiver of the second antenna side for the downlink line from the base station of the mobile communications (simply, base station) with the mobile station (portable machine); on the contrary, transmission by connecting both optical transmitters/receivers as point-to-point connection in the uplink line from the portable machine to the mobile base station.
However, this connection system requires many optical fiber conductors. Therefore, A multibranching optical transmission system has been proposed to make the system economic by reducing the required optical fiber conductors.
This means that the number of optical fiber conductor is reduced to one for the downlink to distribute optical signals in a site requiring the distribution of the optical signal by using a point-to-two point optical branching device. The uplink, as well, transmits an optical signal from respective sites through a single optical fiber by multiplex using a point-to-two point optical multiplexer.
By this process, in the uplink, the optical fiber as transmission line is one in number and, in addition, an optical signal multiplexed by a single photo-detector is collectively received to make the scale of a photo-detector circuit small as an advantage.
As a specific example appeared in Japanese Published Unexamined Patent Application No.153255/94, a system has been described as that radio signals received by a plurality of antennae—corresponding to the second antenna/e—put in a tunne
Jacobson & Holman PLLC
Kokusai Electric Co. Ltd.
Pascal Leslie
Phan Hanh
LandOfFree
Optical conversion relay amplification system does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Optical conversion relay amplification system, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Optical conversion relay amplification system will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2826516