JP3012766B2 - Relay device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an relay device used in an optical analog communications, in particular, provided as a dead spots for the Wireless paging system, is connected with one master station and cable
Are those about the relay device comprising a dispersing arranged plurality of slave stations.

[0002]

2. Description of the Related Art A radio paging system is composed of a central base station connected to a telephone network, a plurality of peripheral base stations connected to the central base station by inter-station communication lines, and a plurality of radio paging receivers. Have been. When the calling number of the radio paging receiver is dialed from the telephone, radio waves are transmitted from the base stations in the service area, and the corresponding radio paging receiver is called. In order to further improve the service of such a paging system, a relay device is installed in a dead zone where radio waves do not reach, such as in a premises, an underground shopping mall, a tunnel, etc., and a radio wave from a peripheral base station is relayed and amplified. Now you can receive.

FIG. 2 is a block diagram of a relay apparatus 12 to which the present invention is applied. In the figure, 11 is a peripheral base station, 13 is a radio unit, 14 is an electric / optical converter (E / O) for converting an electric signal into light, 15 is a distributor, 16 is a plurality of optical cables, Reference numeral 17 denotes a plurality of slave stations, 18 denotes a plurality of optical / electrical converters (O / E) for converting light into electric signals, 19 denotes a combiner, and 20 denotes a master station. As shown in the figure, the relay device 1
Numeral 2 includes a master station 20, a plurality of slave stations 17-1 to 17-n, and a plurality of cables 16 connecting between them. The radio unit 13 receives a radio wave from the peripheral base station 11 and outputs an amplified high-frequency signal (RF signal). The RF signal output from the wireless unit 13 is converted into light by an E / O converter 14 and distributed to a plurality of slave stations 17 by a plurality of optical cables 16 connected to a distributor 15. The plurality of slave stations 17 are distributed and arranged, for example, in a range of 1 m to 20 km in order to make the whole area in the premises of the blind zone, the underground mall, and the tunnel a service area. The connection between the plurality of slave stations 17 and the master station 20 has a low loss (0.3 dB / km to 0.5 dB / km).
An optical cable 16 having the following characteristics is used, and optical analog transmission is employed.

Similarly, a monitoring optical signal is sent from a plurality of slave stations 17 to a master station 20 via an optical cable, converted into an electrical signal by an optical / electrical converter (O / E) 18 and combined by a combiner 19. Are input to the radio unit 13.

FIG. 3 is a conventional block diagram of a downlink from the master station 20 to the slave station 17 in FIG.
Is an RF signal input terminal , and 2 is an amplifier in the radio unit 13. 14 is an E / O converter, 16 is an optical cable, and the distributor 15 is omitted. 9 is the conventional in the slave station
And an optical / electrical converter (O / E) 3 for converting light into an electric signal, and a variable gain amplifier 4. An antenna is connected to the output terminal 7, and a radio wave (output RF signal) is transmitted to the paging receiver. The variable gain amplifier 4 is configured such that the gain is adjusted when the slave station is installed so that a specified transmission RF output can be obtained.

[0006]

The plurality of slave stations 17 provided with the above-mentioned conventional optical receiving device 9 are provided with service areas sequentially from a position close to the master station 20 in a narrow area such as in a tunnel. They are distributed as far as a chain, and in the case of a large area such as an underground shopping mall, they are distributed and arranged in a vertical and horizontal lattice. In any case, the master station 20 and the plurality of slave stations 17
The lengths of the plurality of optical cables 16 for connecting the respective sub-stations are different from each other, and the sub-stations arranged close to each other may be 1 to several meters long, and the sub-stations arranged farthest may be as long as 20 km. As described above, the optical cable is characterized by low loss, but has a loss of 0.3 to 0.5 dB / km. Therefore, in order to install such a repeater 12, the optical cable depends on the position of the slave station. Is 0 to 10 dB, and the electrical signal has a difference of 0 to 20 dB which is twice the optical loss. The level of the output RF signal output to the output terminal 7 of the above-mentioned conventional optical receiving device 9 may be a problem even if the output level is slightly different in a system such as CATV in which a reproduced image is obtained by an image receiver directly connected to the output terminal 7. However, in a paging system that transmits radio waves by connecting an antenna, the range of radio waves differs and the service range differs for each slave station, which causes a problem. The area of the service area of each slave station is set to be substantially equal, and the variable gain amplifier of the optical receiver 9 is used to compensate for the difference in the loss of the optical cable at the time of installation of the slave station and make the transmission levels substantially equal. 4 was manually adjusted for installation.

FIG. 4 is a diagram showing an example of the characteristics of the optical RF output with respect to the input RF signal when a light emitting diode is used as the E / O converter 14, and shows the relationship between the current of the light emitting diode and the optical output. This indicates that when a high frequency signal (input RF) is superimposed on the bias current of the light emitting diode and driven, an analog intensity modulated optical output can be obtained. Input RF
When the modulation degree of the signal is m, the optical output is A (1 + msin
pt) expressed as cos ωt, dB when this output is demodulated
The conversion is 2 × 10 log A + 20 logm [dB].
10 log A [dB] of the first term of this equation is a light level.

FIG. 5 is a diagram for explaining the characteristics of the photodiode and the detection operation, and is a diagram for explaining the demodulation (detection) operation when a photodiode is used for the O / E converter 3 of the optical receiver 9 in FIG. Optical input A from optical cable 16 to photodiode
Is input, B flows as a photodiode current.
When the optical input A is intensity-modulated by the RF signal a, the RF signal b is superimposed on the photodiode current B and output. When the optical input is at the A level and the modulation degree of the RF signal a is m, the detection R
The F current becomes b. However, when the length of the optical cable 16 is long and the loss increases, and the optical input A becomes A ', the modulation degree m is constant, so that the photodiode current B' becomes small, and the detection RF current becomes b '. Become smaller.
The variable gain amplifier 4 needs to correct the amount by which the RF detection signal b is reduced to b ′, that is, twice the loss of the optical cable in which the optical input A becomes A ′.

As described above, when a slave station 17 equipped with the conventional optical receiver 9 is newly installed or added, the variable gain amplifier 4 needs to be manually adjusted. However, there is a disadvantage that it takes labor and time to perform the adjustment.

It is an object of the present invention to correspond to the length of an optical cable.
More to provide a light receiving device that can without manually adjusted by the amplification degree obtain the specified level of the high-frequency output signal when the level of the received input light is Tsu different and, further, the relay apparatus in a radio paging system Another object of the present invention is to provide a repeater in which the labor and time required for installation adjustment and work time are remarkably reduced by automatically compensating for the difference in optical cable loss depending on the installation position when distributing the slave stations.

[0011]

SUMMARY OF THE INVENTION An optical receiving apparatus, which is an essential part of the present invention, receives an optical output of a fixed level on which a high-frequency signal is superimposed via an optical cable of an unspecified length and converts the optical output into a high-frequency signal. An optical receiving apparatus including an optical / electrical converter and a variable gain amplifier for amplifying the output of the optical / electrical converter and outputting a high-frequency output signal of a specified level is input to the optical / electrical converter. A current detector for detecting a current value of the optical / electrical converter that changes linearly in response to a level change of the received light of an unspecified level; and a length of the optical cable based on a detected current value obtained from the current detector. Loss proportional to
It is estimated that the variable gain amplifier has a gain to compensate for the loss.
Control for giving such a gain control signal to the variable gain amplifier
A high-frequency output signal having the specified level regardless of the length of the optical cable.

A relay apparatus using the receiving apparatus of the present invention receives a radio wave from a peripheral base station in a radio paging system and superimposes a high-frequency signal of the radio wave on light of a predetermined level. A master station for transmitting a plurality of optical outputs from the distributor, a plurality of optical cables each having one end connected to the distributor of the master station and transmitting the plurality of optical outputs, and the other ends of the plurality of optical cables being respectively connected Optical receiving means for receiving an optical output from the master station via an optical cable, amplifying a high-frequency signal extracted by an optical-to-electrical converter with a variable gain amplifier, and outputting a high-frequency output signal of a specified level. The high frequency output signal of the
In the relay apparatus having a plurality of slave stations which antenna is provided for delivering against Bisueria of the portable device, the double
The number of variable gain amplifiers of the slave stations is variable according to the master station.
Lengths corresponding to the minimum and maximum distances between the satellite and multiple slave stations
A current detector configured to detect a current value of the optical / electrical converter in each of the optical receivers of the plurality of slave stations, the current detector being set in accordance with a difference in loss of the optical cable, and a detection obtained from the current detector Loss proportional to the length of the optical cable from the current value
Gain for estimating loss and for the variable gain amplifier to compensate for the loss
To the variable gain amplifier such that
And a control circuit, high-frequency output signal level sent from the antenna of the plurality of child stations regardless of the distance <br/> and the plurality of slave stations and the master station automatically all approximately equal
Service areas of multiple slave stations are almost all equal
It is characterized in that configured to be properly.
Further, the length of the plurality of optical cables is 1 m to 20 km.
In any of the ranges described above.

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a block diagram showing an embodiment of an optical receiving apparatus which is a main part of the present invention.
A current detector 5 for detecting the current value of the O / E converter 3 and a control circuit 6 for controlling the gain of the variable gain amplifier 4 based on the detected current value are provided. When a photodiode is used as the O / E converter 3, as shown in FIG. 5, the current flowing through the photodiode changes linearly with a change in the optical input level. That is, the current detector 5, it detects the DC current value of the O / E converter 3 corresponding to the level of the input light received from the master station 20 of the relay device 12 via the optical cable 16. The control circuit 6 converts the detected current into a digital value by an A / D converter, for example, and is proportional to the length of the optical cable from the DC current value of the reference value (optical cable 0 m).
Then, a gain control signal such that the output RF signal voltage at the output terminal 7 of the variable gain amplifier 4 becomes a predetermined specified value is supplied to the variable gain amplifier 4 to change the degree of amplification. A method for estimating optical cable loss from the detected current
For example, the value of the photodiode current with respect to the light loss
Is stored in the nonvolatile memory of the control circuit in advance, and
By reading the optical loss corresponding to the current from the memory,
And can be easily realized . That is, the control circuit 6
Means that the gain of the variable gain amplifier 4 is proportional to the length of the optical cable
Variable gain control signal to compensate for loss
It is given to the gain amplifier 4.

[0014]

As described in detail above, the essential points of the present invention are as follows.
In the optical receiving device, the gain is automatically controlled even if there is a large difference in the level of the input light modulated by the RF signal, and an RF output signal of a specified level can be obtained. Therefore, by providing the optical receiving device 8 , which is a main part of the present invention, in each of the plurality of slave stations of the repeater in the radio paging system, the antennas of the plurality of slave stations distributed over the optical cables 16 of different lengths can be used. The levels of the output RF signals to be transmitted can all be automatically made substantially equal. Therefore, due to the size of the blind spot where the relay device is installed, the planar shape, etc.,
Since the variable gain range of the variable gain amplifier can be set based on the distance from the installation point of the master station to the installation point of the farthest slave station, the labor and time required for installation adjustment for new installations and expansions are greatly reduced. The practical effect is extremely large.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of an optical receiving device which is a main part of the present invention.

FIG. 2 is a diagram illustrating an example of a system configuration to which the present invention is applied.

FIG. 3 is a configuration example diagram of a conventional device.

FIG. 4 is a graph showing an example of electrical / optical conversion characteristics.

FIG. 5 is a diagram illustrating an example of light / electricity conversion characteristics and an operation of the present invention.

[Explanation of symbols]

REFERENCE SIGNS LIST 1 RF input terminal 2 amplifier 3 O / E converter 4 variable gain amplifier 5 current detector 6 control circuit 7 RF output terminal 8, 9 optical receiver 11 peripheral base station 12 relay device 13 radio unit 14 E / O converter 15 Distributor 16 Optical cable 17 Slave station 18 O / E converter 19 Synthesizer 20 Master station

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI H04B 10/16 (72) Inventor Takashi Yokote 3-14-20 Higashinakano, Nakano-ku, Tokyo International Electric Company (72) Invention Person Hiroshi Suzuki 3-14-20 Higashinakano, Nakano-ku, Tokyo International Electric Co., Ltd. (72) Inventor Jun Suganuma 2- 10-1, Toranomon, Minato-ku, Tokyo NTT Mobile Communications Network Co., Ltd. (56) reference Patent flat 1-30336 (JP, a) JP flat 4-157820 (JP, a) JitsuHiraku Akira 59-137657 (JP, U) (58 ) investigated the field (Int.Cl. ⁷ H04B 10/00-10/28 H04B 7/26

Claims (2)

(57) [Claims] 1. A peripheral base station in a radio paging system
These radio waves are received and the high-frequency signal of the radio waves is
A master station that superimposes on the light and sends out a plurality of light outputs from the distributor;
One end of each of the plurality of light sources is connected to the distributor of the master station.
A plurality of optical cables each transmitting an output;
The other ends of the optical cables are connected and distributed,
Each receives optical output from the master station via an optical cable.
Variable high-frequency signal extracted by light-to-electricity converter
Amplifies with a gain amplifier and outputs a high-frequency output signal at a specified level.
And the high-frequency output signal of the optical receiver.
The antenna to be transmitted to the portable device in the service area is
In a relay device including a plurality of slave stations provided, the variable gain amplifier of each of the plurality of slave stations may have a variable gain range.
Corresponds to the minimum and maximum distance between the parent station and multiple child stations.
That is set in accordance with the difference between the loss of length of the optical cable, each of the optical receiver of the plurality of slave stations, said optical / electrostatic
A current detector for detecting a current value of the gas converter;
From the detected current value obtained from the
The proportional gain is estimated and the variable gain amplifier compensates for the loss.
A gain control signal to compensate for the gain.
And a control circuit provided to the device, regardless of the distance between the master station and the plurality of slave stations.
High frequency output signals transmitted from the antennas of the plurality of slave stations.
Signal levels are automatically almost equal to each other.
Configured so that all service areas are almost equal
A relay device characterized in that: 2. The optical cable according to claim 1, wherein said plurality of optical cables have a length of 1 m to 2 m.
2. The relay device according to claim 1, wherein the distance is within a range of 0 km.