JPH0964815A - Optical communication system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase a dynamic range by separating each of plural received signals and amplifying each separated signal with a nonlinear amplifier so as to prevent an excess input of an electroopticcal converter without intermodulation distortion. SOLUTION: Radio signals sent from plural mobile stations are received by a radio base station 191, in which frequency conversion and optical conversion are applied to the signals, the result is sent to a control station 192 through an optical fiber 9. The control station 192 demodulates the signal and detects the level of the received input. The base station 191 uses a low noise amplifier 1 to amplify the received radio signals by n-channels and a distributer 2 to branch the signals into n-ways. Each distributed signal is frequency-converted by signals of mixers 31-34 and synthesizers 36-39 to apply frequency conversion to decided frequencies F1-F4 not deteriorated by intermodulation distortion. Signals subjected to frequency conversion is given to a BPF, in which only one frequency component is separated. The separated signal is amplified, synthesized and subjected to electrooptic conversion 8 and the result is sent to the control station 192 through the optical fiber 9.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical microcell communication system for mobile communication, and in particular, a base station receives radio channel signals from a plurality of mobile stations at different frequencies, and the base station receives the radio signals as optical signals. In the optical microcell communication system that converts the signal to the optical fiber and transmits it through the optical fiber, the level difference between the wireless channels input to the electro-optical converter in the base station that receives the wireless channel signals of different frequencies is reduced, The present invention relates to a method for keeping the converter within the required dynamic range.

[0002]

2. Description of the Related Art As shown in FIG. 4, a conventional optical communication system uses an antenna 4 for receiving radio signals from a plurality of mobile stations.
0, a low noise amplifier 41 that amplifies a received n-line radio signal, a mixer 42 and an oscillator 43 that frequency-converts the signal, a bandpass filter 44 having a pass band corresponding to the reception band of the n line, and n. The radio base station 491 including the linear amplifier 45 for amplifying the radio signal of the line and the electro-optical converter 46.
Is composed. The reception signal of the wireless base station 491 is transmitted to the control station 492 via the optical fiber 47. In addition, the photoelectric converter 410 and the distributor 4 that distributes each signal
11 and a mixer 421 for frequency-converting the distributed signal
To 424, synthesizers 431 to 434, band pass filters 441 to 444 having a pass band for one wave, and demodulators 451 to 45 for demodulating the outputs of the band pass filters.
4 and a detector 4 for detecting the level of the bandpass filter
61 to 464 and A / D for digitizing the detector output
A control station 492 is configured with the converters 471 to 474 (refer to the dynamic range improving method in the microcell system using SB-6-5 subcarrier transmission of the 1992 IEICE Spring Conference).

[0003]

In the conventional optical communication system, when receiving signals of arbitrary plural frequencies among radio channels arranged at equal intervals, the difference between the respective receiving input levels is taken into consideration, A constituent element having excellent characteristics is required so as to have a low distortion and a wide dynamic range, and it has been particularly difficult to transmit a long distance with an optical fiber.

There is also a method of using an AGC amplifier in the preceding stage of the electro-optical converter, but in that case, means for separately transmitting the RSSI signal to the control station was required.

In view of the drawbacks of the prior art, an object of the present invention is to separate a plurality of received signals for each wave to prevent deterioration due to intermodulation distortion, and to use a non-linear amplifier to provide an electro-optical converter. It is to prevent the excessive input of and increase the dynamic range.

[0006]

In order to solve the above problems, the optical communication system of the present invention is a low noise amplifier for amplifying a received n-line radio signal, a distributor for distributing the signal,
A radio base including a mixer and a synthesizer for frequency-converting distributed signals, a bandpass filter having a pass band for one wave, a non-linear amplifier for amplifying each signal, a combiner for combining each signal, and an electro-optical converter Station, opto-electric converter, distributor for distributing each signal, mixer and oscillator for frequency-converting the distributed signal, bandpass filter having one wave pass band, demodulator 151 connected in parallel to each filter 154, detectors 161-164, A / D converter for digitizing the detector output, and a ROM for compensating the output of the non-linear characteristic and the inverse characteristic of the non-linear amplifier to correct the data, and the radio station It is composed of an optical fiber that connects a station and a control station to serve as a transmission line. Further, the ROM is characterized in that it compensates an output having an inverse characteristic with respect to the input / output characteristic of the nonlinear amplifier.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of the present invention, FIG. 2 is a graph of input / output characteristics of a non-linear amplifier, and FIG. 3 is a graph showing a relationship between input / output data of a ROM.

In FIG. 1, reference numeral 191 is a radio base station that directly communicates with a mobile station by radio, 192 is a control station, and a plurality of radio base stations including this radio base station 191 and a control station 19 are provided.
The two are connected by a transmission line such as an optical fiber 9. In the figure, 1 is a low noise amplifier that amplifies a received n-line radio signal, 2 is a distributor for separating each n-line, 31-34 and 36-39 are mixers for frequency-converting the signal. Oscillators 51 to 54 are band pass filters having pass bands for respective reception bands, 61 to 6
Reference numeral 4 is a non-linear amplifier, 7 is a combiner, and 8 is an electro-optical converter, which constitute a radio base station 191. As shown in FIG. 2, the characteristics of the non-linear amplifier tend to decrease in output without being directly proportional to the increase in input. This is because a large received input is compressed to fit within a predetermined dynamic range. An optical fiber 9 connects the radio base station 191 and the control station 192. 10 is an opto-electric converter, 11 is a distributor which distributes each signal, 121-12
4 and 131 to 134 are mixers and synthesizers for frequency-converting the distributed signals, 141 to 144 are band pass filters having a pass band of one wave, 151 to 154 are demodulators for demodulating the output of the band pass filter, 161 ~ 16
4 is a detector for detecting the output level of the bandpass filter, and 171 to 174 are A for digitizing the detector output.
A / D converters 181 to 184 are ROMs connected to the respective A / D converters. These constitute the control station 192. As shown in FIG. 3, the output of the ROM compensates the output having the inverse characteristic with respect to the input / output characteristic of the nonlinear amplifier.

Next, the operation of the embodiment will be described.

Radio signals transmitted from a plurality of mobile stations are received by the radio base station 191, frequency-converted and optical-converted and transmitted to the control station 192 through the optical fiber 9, and the control station 19
At 2, demodulation and reception input level detection are performed.

In the radio base station 191, the received n-line radio signal is amplified by the low noise amplifier 1 and then distributed by the distributor 2 to n.
Branch (n = 4 in FIG. 1). The distributed signals are mixers 31 to 34 for frequency conversion into predetermined frequencies F1 to F4 that are not deteriorated by mutual modulation distortion of each other.
And the frequencies of the synthesizers 36 to 39 are frequency-converted. The respective frequency-converted signals are separated by the band-pass filters 51 to 54 for only one wave. Each of the separated signals is amplified by the non-linear amplifiers 61 to 64 with the characteristics shown in FIG. 2, and the respective signals are combined by the combiner 7 and converted into an optical signal by the electro-optical converter 8, and the optical fiber 9
And sent to the control station 192.

In the control station 192, the optical signal sent from the radio base station 191 is converted into an electric signal by the photoelectric converter 10 and then distributed by the distributor 11 to each signal. The distributed signals are frequency-converted by mixers 121-124 and oscillators 131-134, and then separated by bandpass filters 141-144 having a pass band for one wave. The received signals of the separated signals are reproduced by the respective demodulators 151 to 154 and become the reception output.

On the other hand, in order to detect the reception level of the separated signal on the control station side, the levels are detected by the wave detectors 161-164.
The detector output is digitized by the A / D converters 171 to 174. Further, since the non-linear amplifier is used in the radio base station, the inverse characteristic of the non-linear amplifier (shown in FIG. 3) is input to the R
The reception levels are corrected by the OMs 181 to 184.

[0015]

As described above, according to the present invention, a plurality of received signals are separated for each wave and then amplified by a non-linear amplifier to prevent intermodulation distortion and prevent excessive input of an electro-optical converter. , Has the effect of increasing the dynamic range. Furthermore, by using the ROM in which the inverse characteristics of the non-linear amplifier are input when detecting the reception level at the control station,
There is an effect that an accurate reception level can be measured.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of an embodiment of the present invention.

FIG. 2 is a graph showing input / output characteristics of a non-linear amplifier.

FIG. 3 is a graph showing a relationship between input / output data of ROM

FIG. 4 is a block diagram showing a configuration of a conventional technique.

[Explanation of symbols]

 1 Low Noise Amplifier 2 Distributor 31-34 Mixer 36-39 Synthesizer 51-54 Bandpass Filter 61-64 Nonlinear Amplifier 7 Combiner 8 Electro-Optical Converter 9 Optical Fiber 10 Photo-electric Converter 11 Distributor 121-124 Mixer 131 -134 oscillator 141-144 band pass filter 151-154 demodulator 161-164 detector 171-174 A / D converter 181-184 ROM 191 radio base station 192 control station 40 antenna 41 low noise amplifier 42 mixer 43 oscillator 44 band Pass filter 45 Linear amplifier 46 Electro-optic converter 47 Optical fiber 410 Opto-electric converter 411 Distributor 421-424 Mixer 431-434 Synthesizer 441-444 Band pass filter 451-454 Demodulator 461-464 Detector 4 71-474 A / D converter 491 Radio base station 492 Control station

Claims (2)

[Claims] 1. A low noise amplifier for amplifying a received n-line radio signal, a distributor for distributing the signal, a mixer and a synthesizer for frequency-converting the distributed signal, and a pass band for one wave. Bandpass filter, non-linear amplifier for amplifying each signal, combiner for combining each signal, electro-optical converter, optical fiber, opto-electric converter, distributor for distributing each signal, distribution A mixer and an oscillator for converting the frequency of the converted signal, a bandpass filter having a pass band for one wave, a demodulator and a detector connected in parallel to each filter, and an A / D for digitizing the detector output.
An optical communication system comprising a converter and a ROM for correcting data. 2. The optical communication system according to claim 1, wherein the ROM is a ROM for compensating an output having an inverse characteristic with respect to the input / output characteristic of the nonlinear amplifier.