JP2004080409A - Radio optical fusion communication system and radio optical fusion communication method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a radio optical fusion communication system and method wherein a base station transmits a radio modulation signal to a remote antenna station via an optical fiber and the remote antenna station applies photoelectric conversion to the received optical signal. <P>SOLUTION: The radio optical fusion communication system is provided with a base station comprising: first and second laser light sources whose wavelengths differ from each other; an intermediate frequency band signal generating means; a modulator for modulating a first optical signal into a carrier non-suppression type single side band (SSB) optical modulation signal or a double side band (DSB) optical modulation signal by using the intermediate frequency band signal; and an optical mixer for mixing a second optical signal being a non-modulation light source whose frequency is apart from the frequency of the optical modulation signal by a desired radio frequency band with the optical modulation signal and optically transmitting the mixed signal, with an optical fiber transmission line through which the optical signal is transmitted, with a remote antenna station wherein the optical signal is subjected to photoelectric conversion to generate the radio modulation signal and the signal is emitted from an antenna, and with a terminal for receiving the radio modulation signal, extracting the intermediate frequency band conversion signal, and demodulating the signal. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a wireless optical fusion system in which a wireless modulation signal is optically transmitted from a base station to a remote antenna station, and the received optical signal is photoelectrically converted at the remote antenna station to wirelessly transmit the signal from an antenna to a terminal. The present invention relates to a communication system and a wireless optical fusion communication method.
[0002]
[Prior art]
A wireless device that transmits a high-speed digital signal or a wideband analog signal or the like generally multiplies an intermediate frequency band signal (IF) and a local oscillation signal (LO) and performs up-conversion to obtain a wireless modulation signal ( RF), a transmitter having a function of transmitting a radio modulation signal (RF) modulated by the modulator, and a radio modulation signal (RF) received and multiplied by a local oscillation signal (LO). And a receiver having a function of generating an intermediate frequency band signal (IF) by down-conversion.
[0003]
In order to maintain the quality of the transmission signal in the transceiver, the intermediate frequency band signal (IF) input to the transmitter and the intermediate frequency band signal (IF) generated by the receiver have a predetermined frequency difference. It is required that the time variation of the phase difference be sufficiently small. Therefore, a local oscillator that generates a local oscillation signal (LO) in a transceiver is required to have excellent frequency stability and low phase noise. In particular, in a microwave region having a high frequency, the dielectric resonator or the PLL (Phase) is used.
Lock Loop) circuit stabilizes and reduces noise.
[0004]
However, as the operating frequency becomes higher (eg, 30 GHz)
As described above, it is difficult to realize a low-noise oscillator having high stability and high stability, and the manufacturing cost increases. For example, in a dielectric resonator, a Q (Quality) value is low, and performance cannot be exhibited. In the PLL circuit, particularly, a configuration of a frequency divider becomes difficult.
[0005]
As a method for solving the above problem, there is a method of obtaining a local oscillation signal (LO) by frequency-multiplying a signal from a low-frequency oscillator, but generally requires an amplifier for increasing the signal strength, which is expensive. In addition, problems such as an increase in size, an increase in power consumption, and the like also occurred.
[0006]
In order to solve these problems, a wireless communication device and a wireless communication method described in JP-A-2001-53640 shown in FIG. 4 have been proposed. FIGS. 4A to 4C are schematic diagrams for explaining a radio communication system in a conventional example, and explain the relationship among an intermediate frequency band signal (IF), a local oscillation signal (LO), and a radio modulation signal (RF). FIG.
[0007]
In FIG. 4A, a radio communication device 41 in a base station includes a mixer 43 for multiplying a local oscillation signal (LO) and an intermediate frequency band signal (IF), a bandpass filter 44 for removing unnecessary signals, A local oscillation signal generator 45 for generating a local oscillation signal (LO); a distributor 46 for distributing the local oscillation signal (LO) generated by the local oscillation signal generator 45; A power combiner 47 for adding the modulated signal (RF) and a part of the local oscillation signal (LO) distributed by the distributor 46; and an amplifier 48 for amplifying the wireless signal added by the power combiner 47. , And an antenna 49 for radiating a radio signal amplified by the amplifier 48.
[0008]
The input intermediate frequency band signal (IF) is multiplied by a local oscillation signal (LO) by a mixer 43 and passes through a bandpass filter 44 to filter an unnecessary signal to obtain a required radio modulation signal (RF). ) Is generated. A part of the local oscillation signal (LO) generated by the local oscillation signal generator 45 is added to the radio modulation signal (RF) by the power combiner 47 to be a radio signal. The radio signal is transmitted from an antenna 49 after the signal level is increased by an amplifier 48.
[0009]
On the other hand, the receiver 42 shown in FIG. 4B includes an antenna 410 for receiving the radio signal transmitted from the base station, a band-pass filter 411 for removing noise and the like from the radio signal, and amplifying the radio signal. 412, and a squarer 413 for demodulating a radio signal to generate an intermediate frequency band signal (IF).
[0010]
In the radio signal received by the antenna 410, unnecessary signals are filtered by a bandpass filter 411 in the receiver 42, the signal level is increased by an amplifier 412, and then the signal is increased by a square detector 413 to an intermediate frequency band signal (IF). Demodulated. In the above method, the same local oscillation signal (LO) used to generate the radio modulation signal (RF) is transmitted as a radio signal. Therefore, the influence of the phase noise of the local oscillation signal generator 45 serving as a local oscillation signal (LO) source is canceled at the time of demodulation. There is an advantage that the demodulated intermediate frequency band signal (IF) is demodulated to the frequency of the original intermediate frequency band signal (IF) input to the transmitter.
[0011]
In recent years, in the field of R & D using wireless optical fusion, the low transmission loss and wide area characteristics of optical fibers have been used to reduce the cost, simplify, and reduce the size of wireless access points that transmit wireless signals over optical fibers. Efforts are being made to achieve this. In addition, a method of not only transmitting a wireless modulation signal through an optical fiber but also simultaneously realizing a function of generating an extremely high frequency wireless signal such as a millimeter wave band by using an optical fiber is being studied. ing.
[0012]
[Problems to be solved by the invention]
Means for generating a radio signal of a high frequency such as a millimeter wave band using an optical device and transmitting the radio signal through an optical fiber at the same time as shown in FIG. FIG. 5 is a diagram illustrating a conventional example in which a high-frequency radio signal is generated and the radio signal is simultaneously transmitted through an optical fiber. In FIG. 5, the wireless communication device includes a base station, an optical fiber transmission line 521, a remote antenna station, and a terminal (not shown).
[0013]
The base station mixes a first light source 514 and a second light source 515 that generate laser lights of different wavelengths with signals partially branched from the first light source 514 and the second light source 515, respectively. Mixer 516, a detector 517 for optically detecting the optical signal mixed by the mixer 516, and an oscillation frequency of the first light source 514 and the second light source 515 using an output of the detector 517 as an input signal. A controller 518 for controlling the phase and a mixer 520 for mixing the optical signal from the first light source 514 with the optical signal modulated by the modulator 519 and the optical signal from the second light source 515. It is configured.
[0014]
The laser light from the first light source 514 is modulated by the modulator 519 with the information signal DATA. Thereafter, the optical signal modulated by the modulator 519 and the optical signal generated by the second light source 515 are mixed by a mixer 520 and transmitted by an optical fiber transmission line 521. At the receiving side, that is, at the remote antenna station, the optical signal is detected by the broadband optical detector 522, and a radio modulation signal (RF) corresponding to the difference between the wavelengths of the two light sources can be obtained.
[0015]
As described above, the wireless optical fusion communication system can relatively easily generate a radio modulation signal (RF) even for a very high frequency radio signal that is difficult to generate in an electric circuit. . However, in order to stabilize the obtained radio modulation signal (RF) in frequency characteristics and phase characteristics, the two laser light sources to be used are strictly stabilized in frequency, and at the same time, have a relative frequency. The phase relationship must be fixed.
[0016]
That is, for example, as shown in FIG. 5, signals from the two laser light sources are partially branched and mixed by a mixer 516, which is detected by a detector 517, and whose output is monitored by a controller 518. . That is, the two laser light sources, the first light source 514 and the second light source 515, have a so-called optical phase-locked loop (PLL) mechanism such as having a feedback mechanism for sequentially adjusting the frequency and phase from the outside. Are synchronized in phase. Therefore, the base station has a problem that the device is very expensive and large.
[0017]
SUMMARY OF THE INVENTION The present invention is directed to solving the above problems, and is a wireless optical fusion communication system capable of obtaining an inexpensive local oscillator having a stable frequency even when a radio frequency band used becomes high. And a wireless optical fusion communication method.
[0018]
An object of the present invention is to provide a wireless-optical fusion communication system and a wireless-optical fusion communication method that have a simple configuration without causing frequency fluctuation or phase noise occurring in a radio frequency to affect communication quality.
[0019]
SUMMARY OF THE INVENTION It is an object of the present invention to provide a wireless optical fusion communication system and a wireless optical fusion communication method that prevent signal quality deterioration due to phase noise included in a local oscillation signal, which occurs in a conventional wireless transceiver.
[0020]
[Means for Solving the Problems]
(First invention)
The wireless optical fusion communication system of the first invention generates a wireless modulation signal in a base station, converts the wireless modulation signal into an optical signal while maintaining the modulation form through electro-optical conversion, and converts the wireless modulation signal to a remote antenna station. The remote antenna station performs fiber transmission, and the remote antenna station photoelectrically converts the transmitted optical signal to take out the wireless modulation signal and wirelessly transmit the wireless modulation signal from the antenna. First and second laser light sources 124 and 125 for generating an optical signal, intermediate frequency band signal generating means 126 for generating a modulation signal in an intermediate frequency band, and an intermediate frequency band generated by the intermediate frequency band signal generating means 126 A modulator that modulates the first optical signal into a single-sideband (SSB) optical modulation signal of a carrier non-suppression type or a double-sideband (DSB) optical modulation signal with a signal. And an optical mixer 128 that mixes the second optical signal and the optical modulation signal, which are unmodulated light sources separated in frequency by a desired radio frequency band with respect to the optical modulation signal, and optically transmits the mixed light. With the configured base station 123:
An optical fiber transmission line 129 for transmitting an optical signal transmitted by the base station 123;
A remote antenna station 130 that generates an unmodulated carrier and a radio modulated signal by photoelectrically converting the optical signal transmitted from the optical fiber transmission line 129 and radiates from the antenna 133:
A wireless terminal 134 that receives an unmodulated carrier and a radio modulated signal transmitted from the remote antenna station 130, generates a product component of these two signals, extracts an intermediate frequency band converted signal, and demodulates the signal.
It is characterized by having.
[0021]
(Second invention)
The wireless optical fusion communication system of the second invention is characterized in that the optical signal obtained at the base station 123 is branched and supplied to a plurality of remote antenna stations 130.
[0022]
(Third invention)
A wireless optical fusion communication method according to a third aspect of the present invention is to generate a wireless modulation signal in a base station, convert the wireless modulation signal into an optical signal while maintaining the modulation form by way of electro-optical conversion, and convert the wireless modulation signal to a remote antenna station By transmitting the fiber, the remote antenna station, by photoelectrically converting the transmitted optical signal, to take out the wireless modulation signal and wirelessly transmit from the antenna, by the first and second laser light source, First and second optical signals having different wavelengths are generated, and a modulated signal in an intermediate frequency band is generated. The modulated optical signal is used to convert the first optical signal into a non-carrier-suppressed single sideband (SSB) light. The second optical signal, which is a non-modulated light source that is modulated into a modulated signal or a double sideband (DSB) optical modulated signal, and is separated from the optically modulated signal by a desired radio frequency band, and the optical modulation The optical signal mixed with the signal is transmitted from the base station through the optical fiber transmission line, and the optical signal transmitted from the optical fiber transmission line is received by the remote antenna station. A signal is generated, radiated from an antenna of a remote antenna station, a wireless modulation signal transmitted from the remote antenna station is received by a terminal, and a product component of the two components is generated, whereby an intermediate frequency band conversion signal is generated. And demodulating the signal.
[0023]
(4th invention)
A wireless optical fusion communication method according to a fourth aspect is characterized in that an optical signal obtained at the base station is branched and supplied to a plurality of remote antenna stations.
[0024]
BEST MODE FOR CARRYING OUT THE INVENTION
FIG. 1 is a schematic diagram for explaining a configuration of a wireless optical fusion communication system according to a first embodiment of the present invention. FIGS. 2A and 2B are diagrams for explaining the relationship among the oscillation frequency f ₀₁ , the oscillation frequency f ₀₂ , the intermediate frequency f _IF , and the radio frequency f _RF on the optical frequency axis. In FIG. 1, the wireless optical fusion communication system includes a base station 123, a remote antenna station 130, an optical fiber transmission line 129 connecting the base station 123 and the remote antenna station 130, and a wireless terminal 134. Have been.
[0025]
The base station 123 includes a laser light source 124 to the single mode oscillation at an oscillation frequency _{f 01,} the oscillation frequency _{f 02} of the oscillation frequency _{f 01} corresponds to a radio frequency _{f RF} to be the desired spacing of the laser light source 124 It comprises an oscillating laser light source 125, an intermediate frequency (IF) generator 126 for generating an intermediate frequency (IF) modulated signal modulated by the information signal DATA, a modulator 127, and an optical mixer 128. ing.
[0026]
In base station 123, the output of the laser light source 124 to the single mode oscillation at an oscillation frequency _{f 01} is input the carrier non-suppressed optical single side-band (optical SSB) modulator 127. The modulator 127 receives an intermediate frequency band signal (IF) of the intermediate frequency f _IF generated by the intermediate frequency band signal generator 126 as a modulation signal. As a result, as shown in FIG. 2A, a signal light (f ₀₁ + f _IF ) in which the optical carrier is SSB-modulated on the optical frequency axis is obtained.
[0027]
In this embodiment, the residual carrier type optical SSB signal is obtained by inputting the intermediate frequency band signal to the carrier non-suppressing type optical single sideband (optical SSB) modulator 127. Even if a carrier-remaining optical DSB signal is obtained using a non-carrier-suppressed optical double-sideband (optical DSB) modulator, the same effect can be obtained thereafter. Also, as a method for obtaining a residual carrier type optical DSB signal, it is possible to directly modulate the light source with an intermediate frequency band signal instead of providing a modulator outside the light source as shown in FIG.
[0028]
The signal light (f ₀₁ + f _IF ) and the output light of the laser light source 125 that oscillates in a single mode at an oscillation frequency f ₀₂ different from the oscillation frequency f ₀₁ are input to an optical mixer 128 and mixed. The output of the optical mixer 128 is transmitted to the remote antenna station 130 via the optical fiber transmission line 129. The optical signal spectrum received by the remote antenna station 130 at this time is, as shown in FIG. 2B, the interval between the oscillation frequency f ₀₁ and the oscillation frequency f ₀₂ is set to a desired RF frequency f _RF . Yes, it is.
[0029]
In the remote antenna station 130, the received signal light is detected by the optical detector 131 to generate a non-modulated carrier and a radio modulated signal, then amplified by the amplifier 132, and radiated to the space by the antenna 133.
[0030]
The signal radiated from the antenna 133 of the remote antenna station 130 is received by the antenna 135 of the wireless terminal 134. The unmodulated carrier and the wireless modulated signal component received by the wireless terminal 134 are amplified by an amplifier 136 and then unnecessary components are removed by a bandpass filter 137. Thereafter, the non-modulated carrier and the radio-modulated signal component are detected by a square detector 138, and a product component of the two components is generated, whereby an intermediate frequency band signal (IF) is reproduced. The reproduced intermediate frequency band signal (IF) is input to an intermediate frequency band demodulation circuit 139 and then demodulated to become an information signal DATA.
[0031]
The wireless optical fusion communication system of the present invention shown in FIG. 1 can generate a radio signal of a very high frequency relatively easily without performing frequency conversion by an electric circuit, and at the same time, transmits the radio signal to an optical fiber. It can be used to transmit to a remote antenna station at a distance. Furthermore, the wireless optical fusion communication system eliminates the need for a controller or the like for controlling a laser light source or the like, or does not require advanced control as seen in an optical phase-locked loop circuit, and at low cost. And miniaturization became possible. Also, the wireless optical fusion communication system of the present invention can realize a high-stability and high-quality wireless link from a remote antenna station to a wireless terminal, in addition to low cost.
[0032]
FIG. 3 is a schematic diagram for explaining a configuration of a wireless optical fusion communication system according to a second embodiment of the present invention. In FIG. 3, a wireless optical fusion communication system comprises a base station 123, remote antenna stations 130, 230, 330, 430,..., And an optical fiber transmission line connecting the base station 123 and the remote antenna station 130. 129 and a wireless terminal 134.
[0033]
The wireless optical fusion communication system shown in FIG. 3 is different from the wireless optical fusion communication system shown in FIG. 1 in that a remote antenna station is branched into a plurality. That is, the remote antenna stations 130, 230, 330, 430,... Are distributed from the base station 123 by the optical distributors 240, 340, 440,.
[0034]
Each of the remote antenna stations 130, 230, 330, 430,... Reproduces a radio signal from the received optical signal and radiates it from the antenna 133 to the space, as in the first embodiment. The radio signal is received by an antenna 135, amplified by an amplifier 136, filtered by a bandpass filter 137, detected by a square detector 138, and converted into an information signal by an intermediate frequency band demodulation circuit 139. Demodulated.
[0035]
The wireless optical fusion communication system of the second embodiment makes use of the property of high signal distribution capability at a plurality of locations as well as the low-loss property of an optical fiber, thereby expanding a cover area or spotting a plurality of areas. It became possible to cover at low cost.
[0036]
As mentioned above, although the Example of this invention was described in full detail, this invention is not limited to the said Example. Various design changes can be made without departing from the present invention described in the claims. The blocks in the embodiments of the present invention can be achieved by well-known or known techniques, and can be arbitrarily changed.
[0037]
【The invention's effect】
ADVANTAGE OF THE INVENTION According to this invention, it becomes possible to generate | occur | produce a radio signal of a very high frequency comparatively easily, without performing frequency conversion by an electric circuit, and at the same time, a radio signal is transmitted to a remote antenna using an optical fiber. It has become possible to transmit to a station with low loss and high quality.
[0038]
ADVANTAGE OF THE INVENTION According to this invention, since the control apparatus which controls the frequency of a laser light source became unnecessary, it was a small and low-cost system, and high quality and highly stable communication became possible.
[Brief description of the drawings]
FIG. 1 is a schematic diagram illustrating a configuration of a wireless optical fusion communication system according to a first embodiment of the present invention.
FIGS. 2A and 2B are diagrams for explaining a relationship among an oscillation frequency f ₀₁ , an oscillation frequency f ₀₂ , an intermediate frequency f _IF , and a radio frequency f _RF on an optical frequency axis.
FIG. 3 is a schematic diagram illustrating a configuration of a wireless optical fusion communication system according to a second embodiment of the present invention.
FIGS. 4A to 4C are schematic diagrams for explaining a wireless communication system in a conventional example, and show the relationship among an intermediate frequency band signal (IF), a local oscillation signal (LO), and a wireless modulation signal (RF). It is a figure for explaining.
FIG. 5 is a diagram illustrating a conventional example in which a radio signal of a high frequency is generated and the radio signal is simultaneously transmitted through an optical fiber.
[Explanation of symbols]
123 base station 124 laser light source 125 laser light source 126 intermediate frequency band signal generator 127 modulator 128 optical mixer 129 optical fiber transmission line 130 ... Remote antenna station 131 ... Optical detector 132 ... Amplifier 133 ... Antenna 134 ... Wireless terminal 135 ... Antenna 136 ... Amplifier 137 ... Band filter 138 ...・ Square detector 139 ・ ・ ・ Intermediate frequency band demodulation circuits 230, 330, 430 ・ ・ ・ Remote antenna stations 240, 340, 440 ・ ・ ・ Optical distributor

Claims (4)

A wireless modulation signal is generated at the base station, the wireless modulation signal is converted to an optical signal while maintaining the modulation form by way of electro-optical conversion, and is transmitted to a remote antenna station via an optical fiber. By photoelectrically converting the transmitted optical signal, in a wireless optical fusion communication system that takes out the wireless modulation signal and wirelessly transmits the signal from an antenna,
First and second laser light sources for generating first and second optical signals having different wavelengths,
Intermediate frequency band signal generating means for generating a modulation signal in the intermediate frequency band,
The first optical signal is modulated into a non-carrier-suppressed single sideband (SSB) optical modulation signal or a double sideband (DSB) optical modulation signal by the intermediate frequency band signal generated by the intermediate frequency band signal generating means. A modulator,
An optical mixer that mixes the second optical signal and the optical modulation signal, which is an unmodulated light source separated in frequency by a desired radio frequency band with respect to the optical modulation signal, and transmits the mixed light,
With a base station consisting of:
An optical fiber transmission line for transmitting an optical signal transmitted from the base station;
A remote antenna station that generates an unmodulated carrier and a radio modulated signal by photoelectrically converting the optical signal transmitted from the optical fiber transmission line and radiates from an antenna:
A terminal that receives an unmodulated carrier and a radio modulated signal transmitted from the remote antenna station, generates a product component of these two signals, extracts an intermediate frequency band converted signal, and demodulates the signal.
A wireless optical fusion communication system comprising: The wireless optical fusion communication system according to claim 1, wherein the optical signal obtained by the base station is branched and supplied to a plurality of remote antenna stations. A wireless modulation signal is generated at the base station, the wireless modulation signal is converted to an optical signal while maintaining the modulation form by way of electro-optical conversion, and is transmitted to a remote antenna station via an optical fiber. By performing a photoelectric conversion of the transmitted optical signal, a wireless optical fusion communication method of extracting the wireless modulation signal and wirelessly transmitting the signal from an antenna,
Generating first and second optical signals having different wavelengths by the first and second laser light sources;
A modulated signal in the intermediate frequency band is generated,
Modulating the first optical signal with the modulation signal into a single-sideband (SSB) optical modulation signal of a carrier non-suppression type or a double-sideband (DSB) optical modulation signal;
An optical signal obtained by mixing the second optical signal and the optical modulation signal, which is an unmodulated light source whose frequency is separated from the optical modulation signal by a desired radio frequency band, is transmitted from a base station via an optical fiber transmission line. ,
After receiving the optical signal transmitted from the optical fiber transmission line at the remote antenna station, generate an unmodulated carrier and a radio modulation signal by photoelectric conversion, radiate from the antenna of the remote antenna station,
The terminal receives the unmodulated carrier and the radio modulation signal transmitted from the remote antenna station, generates a product component of these two signals, extracts the intermediate frequency band converted signal, and demodulates the signal.
A wireless optical fusion communication method characterized by the above-mentioned. The wireless optical fusion communication method according to claim 2, wherein the optical signal obtained by the base station is branched and supplied to a plurality of remote antenna stations.

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