JP2693112B2 - Optical fiber link system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

FIELD OF THE INVENTION The present invention relates to an optical fiber link system having a plurality of mixing circuits.

[0002]

2. Description of the Related Art A conventional mixing circuit has a photoelectric conversion function and a mixing function of mixing an intermediate frequency signal obtained by photoelectric conversion by itself and a local oscillation signal input from a local oscillator configured separately from the mixing circuit. It is configured to have both.

FIG. 15 shows an example of a conventional optical fiber link system constructed by using a conventional mixing circuit. The optical fiber link system includes a laser diode 312.
Is provided in the radio control station, and the mixing circuit 300 and the local oscillator 3 are provided.
26, a band pass filter 325, a band pass filter 324, a power amplifier 330, an antenna 331, and an optical lens 327 in a wireless base station, and a wireless control station and a wireless base station are connected by an optical fiber cable 301. It is configured to do.

In FIG. 15, the intermediate frequency signal having the frequency fIF is input to the laser diode 312 via the terminal T1. The laser diode 312 converts an optical signal of a predetermined wavelength generated by itself into an optical signal intensity-modulated according to the input intermediate frequency signal. The optical signal is transmitted through the optical fiber 301, collected by the optical lens 327, and applied to the active region between the base and collector of the transistor 7 of the mixing circuit 300. On the other hand, the local oscillator 326 generates a local oscillation signal of frequency f0 and inputs it to the transistor 7 via the bandpass filter 325. The transistor 7 photoelectrically converts the optical signal into an intermediate frequency signal of frequency fIF, mixes the intermediate frequency signal and the local oscillation signal, and converts the intermediate frequency signal into a transmission signal of carrier frequency f0 + fIF and a signal of frequency f0−fIF. A signal of frequency 2f0, a signal of frequency 2fIF, a signal of frequency f0, and a signal of frequency fIF are generated. The mixed signals are passed through the capacitor 351 to the band pass filter 3
24 is input. The bandpass filter 324 is configured in advance to pass only the transmission signal of the carrier frequency f0 + fIF, passes only the transmission signal of the carrier frequency f0 + fIF, and inputs it to the power amplifier 330.
The power amplifier 330 power-amplifies the transmission signal of the carrier frequency f0 + fIF and radiates it in the free space via the antenna 331.

FIG. 16 shows the H.264 standard. Ogawa, et al. , "Fiber
-Optic Microwave TransmissionUsing Harmonic
Laser Mixing, Optoelectronic Mixing, and Optica
lly Pumped Mixing, "IEEE Trans. Microwave
Theory Tech., Vol. MTT-39, pp.2045-2051, Dec.19
It is another example of the conventional optical fiber link system configured by using the conventional mixing circuit disclosed in 91.

The optical fiber link system has a modulator 314, a laser diode 312, and a harmonic generator 3.
13 is provided in the radio control station, the mixing circuit 321, the band pass filter 322, the photodiode 323, and the band pass filter 324 are provided in the radio base station, and the radio control station and the radio base station are connected to the optical fiber cable 301, It is connected via 302.

In FIG. 16, the data signal is the terminal T5.
Is input to the modulator 314 via the. The modulator 314 is
The carrier signal is converted into an intermediate frequency signal of frequency fIF which is frequency-modulated according to the data signal. The intermediate frequency signal is input to the laser diode 312. The laser diode 312 converts an optical signal of a predetermined wavelength generated by itself into an optical signal intensity-modulated according to the input intermediate frequency signal. The optical signal is the optical fiber cable 3
01, and is input to the mixing circuit 321.

On the other hand, the local oscillation signal of frequency f0 is input to the harmonic generator 313 using a laser diode via the terminal T6. The harmonic generator 313 intensity-modulates an optical signal of a predetermined wavelength generated by itself according to a signal including a local oscillation signal of frequency f0, a signal of frequency 2f0, a signal of frequency 3f0, etc. 323. The photodiode 323 photoelectrically converts the optical signal into a signal including a local oscillation signal of frequency f0, a signal of frequency 2f0, a signal of frequency 3f0, and the like, and inputs the signal to the bandpass filter 322. The bandpass filter 322 is configured to pass only the signal having the frequency 2f0, passes only the signal having the frequency 2f0, and inputs the signal to the mixing circuit 321.

The mixing circuit 321 photoelectrically converts the optical signal intensity-modulated according to the intermediate frequency signal into an intermediate frequency signal, mixes the photoelectrically converted intermediate frequency signal and the signal of frequency 2f0, and outputs the signal of frequency 2f0-fIF. And frequency 2f
A signal of 0 + fIF is generated and a signal of each frequency is output to the bandpass filter 324. The band pass filter passes only one of the frequency 2f0-fIF signal and the frequency 2f0 + fIF signal, and outputs the signal via the output terminal T7.

[0010]

However, in the conventional mixing circuit having only the photoelectric conversion function and the frequency mixing function, there is a problem that a local oscillator needs to be separately provided. As a result, it is necessary to provide a local oscillator in the radio base station in addition to the mixing circuit, which causes a problem that the radio base station cannot be downsized. When the local oscillation signal is input to the radio base station via the radio control station like the optical fiber link system of FIG. 16, it is necessary to equip the radio control station with a harmonic generator. Needs to be equipped with a photodiode and a bandpass filter, and an optical fiber cable for local oscillation signal transmission must be connected between the wireless control station and the wireless base station, which complicates the entire optical fiber link system. There was a problem.

[0011]

An object of the present invention is to provide an optical fiber link system which has a simple structure, is small in size, and is inexpensive as compared with the conventional example.

[0013]

[0014]

[0015]

[0016]

[0017]

[0018]

According to a first aspect of the present invention, there is provided an optical fiber link system which has an input / output terminal and which converts an optical signal incident on an active region of a transistor into an electric signal. A transistor having a non-linear characteristic that mixes a function and two electric signals and outputs a signal having a sum and a difference frequency of the respective electric signals;
A mixing circuit including a feedback circuit connected to the transistor, wherein the transistor converts the optical signal incident on the active region after intensity modulation by an electric signal having a first frequency into the photoelectric conversion function. While performing photoelectric conversion to the electric signal using the feedback circuit, the feedback circuit oscillates and generates a local oscillation signal having a second frequency, and mixes the electric signal and the local oscillation signal using the nonlinear characteristic. Then, an optical fiber link system including two mixing circuits for generating an electric signal having each of a sum and a difference of the first frequency and the second frequency at an output terminal of the transistor, The input circuit of one of the two mixing circuits and the input circuit of the other mixing circuit of the two mixing circuits are provided close to each other so as to be electromagnetically coupled to each other. And having a resonant frequency equal to the second frequency, the flows in the input circuit of the mixing circuit of one said 1
And the second oscillation signal flowing in the input circuit of the other mixing circuit are in opposite phases to each other, and the direction of the magnetic field generated when the first oscillation signal flows and the second oscillation signal
The direction of the magnetic field generated when the oscillation signal of
A resonator provided so as to match the direction of a magnetic field generated when the resonator is excited, and an electric signal having a first frequency that is input are first and second so as to have a phase difference of π with respect to each other. A first distribution means for distributing the second electric signal into two, a first conversion means for converting the first electric signal into a first optical signal, and a first conversion means for converting the first optical signal into the first optical signal. A first optical means for irradiating the active region of the transistor of the mixing circuit, a second converting means for converting the second electric signal into a second optical signal, and a second converting means for converting the second optical signal into the second optical signal. The second optical means for irradiating the active region of the transistor of the other mixing circuit, the electric signal output from the one mixing circuit and the electric signal output from the other mixing circuit are combined in phase. A synthesizing means for outputting and an electric signal output from the synthesizing means And selectively filtering an electric signal having a frequency of the sum of the first frequency and the second frequency or an electric signal having a frequency of the difference between the first frequency and the second frequency. And a filtering means.

The optical fiber link system according to claim 2 is the optical fiber link system according to claim 1,
The resonator is a dielectric resonator.

Further, an optical fiber link system according to a third aspect is the optical fiber link system according to the first aspect, wherein the resonator is a ring resonator.

An optical fiber link system according to a fourth aspect of the present invention has an input / output terminal and a photoelectric conversion function of converting an optical signal incident on an active region of a transistor into an electric signal and two electric signals. A mixed circuit including a transistor having a non-linear characteristic for mixing and outputting a signal of a frequency of a sum and a difference of frequencies of respective electric signals, and a feedback circuit connected to the transistor, wherein the transistor is An optical signal that is intensity-modulated by an electric signal having a first frequency and then enters the active region is photoelectrically converted into the electric signal by using the photoelectric conversion function, while the second frequency is generated by using the feedback circuit. Is generated by oscillating a local oscillation signal having, and mixing the electric signal and the local oscillation signal using the non-linear characteristic to generate the first frequency and the second frequency. An electrical signal having a respective frequency of the sum and the difference between the wave number a fiber optic link system with two mixing circuit for generating the output terminal of the transistor,
The input circuit of one of the two mixing circuits and the input circuit of the other mixing circuit of the two mixing circuits are provided close to each other so as to be electromagnetically coupled, Has a resonance frequency equal to the frequency of
Direction of the magnetic field generated when the second oscillation signal flows and the direction of the magnetic field generated when the second oscillation signal flows are the direction of the magnetic field generated when the resonator is excited. A resonator provided so as to match, and a first electric signal having a first frequency to be input, which is divided into two first and second electric signals so as to have a phase difference of π / 2. Distribution means, first conversion means for converting the first electric signal into a first optical signal by electric / optical conversion, and one of the two mixing circuits for converting the first optical signal into one of the two mixing circuits. First optical means for irradiating the active region of the transistor, and second converting means for converting the second electric signal of the other two distributed by the first distributing means into a second optical signal. , The second optical signal is a transistor of the other mixing circuit of the two mixing circuits The second optical means for irradiating the active region, the electric signal output from the one mixing circuit and the electric signal output from the other mixing circuit, one of the electric signals is phase-shifted by π / 2. Then, the first synthesizing means for synthesizing and outputting, and the electric signal output from the first synthesizing means, an electric signal having a sum and a frequency of the first frequency and the second frequency, or And a filtering means for selectively filtering an electric signal having a frequency that is a difference between the first frequency and the second frequency.

An optical fiber link system according to a fifth aspect of the present invention is the optical fiber link system according to the fourth aspect, wherein the resonator is a dielectric resonator.

Further, an optical fiber link system according to a sixth aspect is the optical fiber link system according to the fourth aspect, wherein the resonator is a ring resonator.

An optical fiber link system according to a seventh aspect of the present invention has an input / output terminal and a photoelectric conversion function for converting an optical signal incident on an active region of a transistor into an electric signal and two electric signals. A mixing circuit comprising a transistor having a non-linear characteristic for mixing signals of the respective electric signals to output signals having a sum and a difference frequency of frequencies, and a feedback circuit connected to the transistor, wherein the transistor is , Photoelectrically converting an optical signal, which is intensity-modulated by an electric signal having a first frequency and then enters the active region, into the electric signal by using the photoelectric conversion function, while using the feedback circuit, a second signal is generated. A local oscillation signal having a frequency is oscillated and generated, and the electrical signal and the local oscillation signal are mixed using the non-linear characteristic to generate the first frequency and the second frequency. Is an optical fiber link system including four mixing circuits for generating electric signals having sum and difference frequencies with respect to the output terminal of the transistor, wherein one of the four mixing circuits is provided. The input circuit of the first mixing circuit, the input circuit of one second mixing circuit of the four mixing circuits, and the third mixing circuit of one of the four mixing circuits. The input circuit and the input circuit of the fourth mixing circuit, which is one of the four mixing circuits, are provided close to each other so as to be electromagnetically coupled, and have a resonance frequency equal to the second frequency. And a first oscillation signal flowing in the input circuit of the first mixing circuit, a second oscillation signal flowing in the input circuit of the second mixing circuit, and a second oscillation signal flowing in the input circuit of the third mixing circuit. The three oscillation signals are out of phase with each other, and the The first oscillation signal flowing in the circuit and the fourth oscillation signal flowing in the input circuit of the fourth mixing circuit are in phase with each other, and the direction of the magnetic field generated when the first oscillation signal flows, Direction of magnetic field generated when the second oscillating signal flows, direction of magnetic field generated when the third oscillating signal flows, and when the fourth oscillating signal flows And a resonator provided so that the direction of the generated magnetic field coincides with the direction of the magnetic field generated when the resonator is excited, and a phase difference π / And a first distributing means that divides the electric signal into two so as to have two, and one electric signal that is divided into two by the first distributing means is divided into a first electric signal and a second electric signal so as to have a phase difference π with each other. The second distribution means and the first optical signal are combined with the first optical signal. First conversion means for converting light into electricity, first optical means for irradiating the active region of the transistor of the first mixing circuit with the first light signal, and second light for converting the second electric signal. A second conversion means for converting the signal into electric signals and an optical signal, a second optical means for irradiating the active region of the second transistor with the second optical signal, and a second distribution means for dividing into two. Third distribution means for distributing the other electric signal into third and fourth electric signals so as to have a phase difference π with each other,
Third converting means for converting the third electric signal into a third optical signal, and third optical means for irradiating the active region of the transistor of the third mixing circuit with the third optical signal. Means, fourth converting means for converting the fourth electric signal into a fourth optical signal, and irradiating the active area of the transistor of the fourth mixing circuit with the fourth optical signal. Four optical means, a first synthesizing means for synthesizing and outputting the electrical signal output from the first mixing circuit and the electrical signal output from the second mixing circuit in the same phase, and the third optical means. Second combining means for combining and outputting the electric signal output from the mixing circuit and the electric signal output from the fourth mixing circuit in phase, and the electric signal output from the first combining means And the electric signal output from the second synthesizing means described above. Third combining means for phase-shifting the signal by π / 2 and then combining and outputting the sum of the first frequency and the second frequency from the electric signal output from the third combining means. And a filtering means for selectively filtering an electric signal having a frequency or an electric signal having a frequency of a difference between the first frequency and the second frequency.

An optical fiber link system according to an eighth aspect is the optical fiber link system according to the seventh aspect, wherein the resonator is a dielectric resonator.

Further, an optical fiber link system according to a ninth aspect is the optical fiber link system according to the seventh aspect, wherein the resonator is a ring resonator.

[0027]

In the mixing circuit according to claim 1, the transistor uses the photoelectric conversion function to convert the optical signal, which is intensity-modulated by the electric signal having the first frequency and then enters the active region, into the active region. While photoelectrically converting to the electric signal, the local oscillation signal having the second frequency is oscillated and generated by using the connected feedback circuit, and the electric signal and the local oscillation signal are generated by using the nonlinear characteristic. And mixes to generate an electrical signal at the output terminal of the transistor having respective frequencies of the sum and difference of the first frequency and the second frequency. Therefore, one transistor can perform photoelectric conversion and generation and mixing of a local oscillation signal.

In the mixed circuit according to the second aspect, the resonator is coupled to the input circuit of the mixed circuit to operate as a resonator, and the unloaded Q of the resonator is high. It can be made large, so that the mixing circuit generates a frequency-stabilized and low-noise local oscillation signal.

In the mixed circuit according to the third aspect, the dielectric resonator is coupled to the input circuit and operates as a resonator,
The mixing circuit produces a frequency stabilized local oscillator signal having the second frequency.

In the mixed circuit according to the fourth aspect, a ring resonator is coupled to the input circuit to operate as a resonator,
The mixing circuit produces a frequency stabilized local oscillator signal having the second frequency.

In the optical fiber link system according to the fifth aspect, the converting means converts the electric signal having the first frequency into an optical signal and outputs the optical signal to the optical means.
The optical means illuminates the optical signal to the active area of the transistor. The transistor photoelectrically converts the optical signal into the electric signal by using the photoelectric conversion function, and oscillates and generates a local oscillation signal having the second frequency to generate the electric signal and the local oscillation signal. Mix
An electric signal having each of the sum and difference frequencies of the first frequency and the second frequency is generated at the output terminal of the transistor and output to the filtering means. The filtering means selectively selects an electric signal having the sum frequency or an electric signal having the difference frequency from electric signals having respective sum and difference frequencies of the first frequency and the second frequency. Slow down. As a result, the electric signal having the first frequency is electro-optically converted and transmitted, and further photoelectrically converted, and then mixed with the local oscillation signal having the second frequency generated in the mixing circuit, whereby the mixing is performed. Selectively filtering an electrical signal having a frequency of a sum of a first frequency and a second frequency or an electrical signal having a frequency of a difference between the first frequency and the second frequency that is subsequently generated. Therefore, an optical fiber link system can be constructed by using the mixing circuit according to the first aspect.

In the optical fiber link system according to the present invention, the first distributing means may input the electric signals having the first frequency so as to have a phase difference of π from each other. The second electric signal is divided into two and output to the first and second conversion means, respectively. The first converter converts the first electrical signal into an optical signal and outputs the first optical signal to the first optical unit, and the first optical unit outputs the first optical signal. The active area of the transistor of the one mixing circuit is illuminated. on the other hand,
The second conversion means converts the second electrical signal into an optical signal and outputs the second optical signal to the second optical means, and the second optical means outputs the second optical signal. To the active area of the transistor of the other mixing circuit.
Further, the resonator has a resonance frequency equal to the second frequency, and the first oscillation signal flowing through the input circuit of the one mixing circuit and the input oscillation circuit of the other mixing circuit. Direction of magnetic field generated when the first oscillation signal flows and direction of magnetic field generated when the second oscillation signal flows when the second oscillation signals have opposite phases Are provided so as to match the direction of the magnetic field generated when the resonator is excited. Therefore, the resonator is electromagnetically coupled to the input circuit of the one mixing circuit and the input circuit of the other mixing circuit, whereby the one mixing circuit and the other mixing circuit are respectively The first local oscillation signal and the second local oscillation signal having a second frequency and opposite phases are oscillated and generated.

The transistor of the one mixing circuit photoelectrically converts the first optical signal into the first electric signal by using the photoelectric conversion function, while the first electric signal and the first electric signal are combined. By mixing one local oscillation signal, an electric signal having each frequency of the sum and difference of the first frequency and the second frequency, an electric signal having the first frequency and the second frequency The electric signal that it has is generated at the output terminal of the transistor. On the other hand, the transistor of the other mixing circuit photoelectrically converts the second optical signal into the second electric signal by using the photoelectric conversion function, while the second electric signal and the second local portion. An electric signal having each frequency of the sum and difference of the first frequency and the second frequency, an electric signal having the first frequency, and an electric signal having the second frequency by mixing oscillation signals. Are generated at the output terminal of the transistor. Further, the synthesizing means is configured so that the first frequency and the second frequency that are input in the same phase of the electric signal input from the one mixing circuit and the electric signal input from the other mixing circuit An electric signal having a sum frequency and an electric signal having a frequency difference between the first frequency and the second frequency are combined, and the first frequency is inputted with a phase difference of π. The electric signal and the electric signal having the second frequency are suppressed and output to the filtering means. The filtering means, from the electrical signal output from the synthesizing means, an electrical signal having a frequency of the sum of the first frequency and the second frequency or the first frequency and the second frequency Selectively filtering electrical signals having a frequency of the difference. Thereby, the synthesizing means, from among the electrical signals generated after mixing, an electrical signal having a first frequency corresponding to the electrical signal included in the optical signal, and a second frequency corresponding to the local oscillation signal. While suppressing the electric signal having the frequency of 1 and the electric signal having the frequency of the sum of the first frequency and the second frequency and the electric signal having the frequency of the difference between the first frequency and the second frequency Output.

In the optical fiber system according to the seventh aspect, the dielectric resonator is electromagnetically coupled to each input circuit of the one and the other mixed circuit of the optical fiber link system according to the sixth aspect. One mixing circuit and the other mixing circuit generate the first and second local oscillation signals having the first frequency and being frequency-stabilized and out of phase with each other.

In the optical fiber system according to claim 8, the ring resonator is electromagnetically coupled to each input circuit of the one and the other mixed circuit of the optical fiber link system according to claim 6, and the one And the other mixing circuit generates the first and second local oscillation signals having the first frequency and being frequency-stabilized and having opposite phases.

In the optical fiber link system according to the ninth aspect, the first distributing means separates the input electric signals having the first frequency from each other so as to have a phase difference of π / 2. The second electric signal is divided into two and output to the first and second conversion means, respectively. The first conversion means converts the first electrical signal into an optical signal and outputs the first optical signal to the first optical means, and the first optical means outputs the first optical signal. The signal is applied to the active area of the transistor of the one mixing circuit.
On the other hand, the second conversion means performs electrical-optical conversion of the second electric signal into a second optical signal and outputs the second optical signal to the second optical means, and the second optical means is the second optical signal. The signal is applied to the active area of the transistor of the other mixing circuit.
The resonator has a resonance frequency equal to the second frequency, and has a direction of a magnetic field generated when the first oscillation signal flows and a direction of a magnetic field generated when the second oscillation signal flows. The direction of the magnetic field generated is provided so as to match the direction of the magnetic field generated when the resonator is excited. Therefore, the resonator is electromagnetically coupled to the input circuit of the one mixing circuit and the input circuit of the other mixing circuit, and the two mixing circuits have the second frequency and the phase. The first and second local oscillation signals of the same phase or opposite phase are oscillated and generated. Further, the one mixing circuit mixes the first electric signal and the first local oscillation signal, and each electric signal having a sum and a difference frequency of the first frequency and the second frequency. A signal, an electric signal having the first frequency, an electric signal having the second frequency, and the like, and outputs to the first combining means, the other mixing circuit, the second mixing circuit, An electric signal and an electric signal having the first frequency and each electric signal having a frequency of a sum and a difference between the first frequency and the second frequency, and an electric signal having the first frequency. And an electric signal having the second frequency is generated so as to have a predetermined phase difference as compared with each electric signal generated in one of the mixing circuits, and is output to the first combining means. The first synthesizing means synthesizes the electric signal output from the one mixing circuit and the electric signal output from the other mixing circuit after shifting one of the electric signals by π / 2. Output to the filtering means. The filtering means, from the electric signal output from the first combining means, an electric signal having a frequency of the sum of the first frequency and the second frequency, or the first frequency and the second frequency. Selectively filtering an electrical signal having a frequency that is the difference between the two frequencies. Thereby, the first synthesizing means generates an electric signal having a frequency of the sum of the first frequency and the second frequency generated after mixing, and an electric signal having a frequency of the difference between the first frequency and the second frequency. One of the signals is suppressed and the other is combined and output.

In the optical fiber system of the tenth aspect, the dielectric resonator is electromagnetically coupled to each input circuit of the one mixing circuit and the other mixing circuit of the optical fiber link system of the ninth aspect. However, the one mixing circuit and the other mixing circuit generate the first and second local oscillation signals having the first frequency and being frequency-stabilized and having opposite phases.

In the optical fiber system according to claim 11, the ring resonator is electromagnetically coupled to each input circuit of the one mixing circuit and the other mixing circuit of the optical fiber link system according to claim 9. The one mixing circuit and the other mixing circuit generate the first and second local oscillation signals having the first frequency and being frequency-stabilized and having opposite phases.

In the optical fiber link system according to the twelfth aspect, the first distributing means divides the inputted electric signals having the first frequency into two so as to have a phase difference of π / 2. Output to the second and third distributing means. The second distribution means distributes one of the electric signals divided into two by the first distribution means to the first and second electric signals so as to have a phase difference π with each other, and respectively divides the first electric signal into the first electric signal. And output to the second conversion means. The first conversion means performs electrical-optical conversion of the first electric signal into the first optical signal and outputs the first optical signal to the first optical means, and the first optical means is the first optical signal. The optical signal is applied to the active area of the transistor of the first mixed circuit.
The second conversion means performs electrical-optical conversion of the second electric signal into the second optical signal and outputs the second optical signal to the second optical means, and the second optical means is the second optical signal. The signal is applied to the active area of the transistor of the second mixing circuit. The third distributing means distributes the other electric signal, which is divided into two by the first distributing means, into the third and fourth electric signals so as to have a phase difference π with respect to each other, and the third and fourth electric signals. It is output to the fourth conversion means. The third conversion means is
The third electric signal is converted into a third optical signal by electric / optical conversion and output to the third optical means, and the third optical means is
The third optical signal is applied to the active region of the transistor of the third mixing circuit. The fourth conversion means performs electrical-optical conversion of the fourth electric signal into the fourth optical signal and outputs the fourth optical signal to the fourth optical means, and the fourth optical means is the fourth optical signal. The optical signal is applied to the active area of the transistor of the fourth mixing circuit.

The resonator includes an input circuit of the first mixing circuit, an input circuit of the second mixing circuit, an input circuit of the third mixing circuit, and an input circuit of the fourth mixing circuit. And a first oscillating signal having a resonance frequency equal to the second frequency and flowing to an input circuit of the first mixing circuit, The second oscillation signal and the first oscillation signal flowing in the input circuit of the second mixing circuit and the third oscillation signal flowing in the input circuit of the third mixing circuit are in opposite phases to each other, and When the first oscillation signal flowing through the input circuit of the one mixing circuit and the fourth oscillation signal flowing through the input circuit of the fourth mixing circuit are in phase with each other, the first oscillation signal flows. The direction of the magnetic field generated when the Direction of the magnetic field generated when the third oscillation signal flows, the direction of the magnetic field generated when the fourth oscillation signal flows, the direction of the magnetic field generated when the fourth oscillation signal flows, It is provided so as to match the direction of the magnetic field generated when the resonator is excited. Therefore, the first mixing circuit and the fourth mixing circuit oscillate and generate the first and fourth local oscillation signals that have the second frequency and are in phase with each other. And the third and third mixing circuits respectively have the second frequency and have the phase difference π compared to the first or fourth local oscillation signal, and the second and third local oscillations. Generates and oscillates a signal.

Further, the first mixing circuit mixes the first electric signal and the first local oscillation signal to obtain a sum and difference frequencies of the first frequency and the second frequency. Each electric signal having, an electric signal having the first frequency, an electric signal having the second frequency, etc. are generated and output to the first combining means, and the second mixing circuit is
Mixing the second electric signal and the second local oscillation signal, each electric signal having a frequency of the sum and difference of the first frequency and the second frequency, the first frequency The electric signal having the second frequency and the electric signal having the second frequency are compared with the electric signals generated in the first mixing circuit so as to have a predetermined phase difference, and the first combining unit generates the electric signal. Output to.

The first synthesizing means receives the electric signal output from the first mixing circuit and the electric signal output from the second mixing circuit from the electric signal output in the opposite phase. Suppressing the electric signal of the frequency and the electric signal of the second frequency, respectively synthesizing each electric signal having each frequency of the sum and difference of the first frequency and the second frequency input in phase Output to the third combining means.

Further, the third mixing circuit mixes the third electric signal and the third local oscillation signal to obtain the sum and difference frequencies of the first frequency and the second frequency. Each electric signal having, the electric signal having the first frequency, the electric signal having the second frequency, etc., so as to have a predetermined phase difference from each electric signal generated in the first mixing circuit. Generated and output to the first combining means, the fourth mixing circuit mixes the fourth electrical signal and the fourth local oscillation signal, the first frequency and the second Each electric signal having a sum and difference frequency with a frequency, an electric signal having the first frequency, an electric signal having the second frequency, etc., generated in the first mixing circuit. The second phase is generated so as to have a predetermined phase difference as compared with the signal. And outputs it to the synthesis means.

The second synthesizing means outputs the first signal input in a reverse phase from the electrical signal output from the third mixing circuit and the electrical signal output from the fourth mixing circuit. Suppressing the electric signal of the frequency and the electric signal of the second frequency, each electric signal having each frequency of the sum and difference of the first frequency and the second frequency input in the same phase, They are combined and output to the third combining means. The third synthesizing means phase-shifts one of the electrical signals output from the first synthesizing means and the electrical signal output from the second synthesizing means by π / 2. It is post-synthesized and output to the filtering means. The filtering means is an electric signal having a sum frequency of the first frequency and the second frequency from the electric signal output from the third combining means, or the first frequency and the second frequency. Selectively filtering electrical signals having a frequency that is the difference in frequency. As a result, among the electric signals generated after the mixing, the first synthesizing means and the second synthesizing means have the electric signal having the first frequency corresponding to the electric signal contained in the optical signal and the local oscillation signal. Suppresses the electric signal having the second frequency corresponding to, and the third synthesizing means further has an electric signal having the frequency of the sum of the first frequency and the second frequency, or the first frequency and the second frequency. One of the electric signals having the frequency difference is suppressed.

In the optical fiber system according to the thirteenth aspect, the dielectric resonator is provided in each of the first, second, third and fourth mixed circuits of the optical fiber link system according to the twelfth aspect. Electromagnetically coupled to the input circuit, the first mixing circuit and the fourth mixing circuit, respectively, the first and the fourth mixing circuit having the second frequency and frequency-stabilized in phase with each other. Generated by oscillating a local oscillation signal,
The second mixing circuit and the third mixing circuit each have the second frequency and have a phase difference π in comparison with the frequency-stabilized first or fourth local oscillation signal. The second and third local oscillation signals are oscillated and generated.

In the optical fiber system according to claim 14, the ring resonator is provided at each input of the first, second, third and fourth mixing circuits of the optical fiber link system according to claim 12. Electromagnetically coupled to the circuit, wherein the first mixing circuit and the fourth mixing circuit each have the second frequency and are frequency-stabilized in-phase first and fourth local oscillations. Oscillating and generating a signal, the second mixing circuit and the third mixing circuit respectively having the second frequency and comparing the frequency-stabilized first or fourth local oscillation signal. Generate and oscillate the second and third local oscillation signals having a phase difference π.

[0047]

Embodiments of the present invention will be described below with reference to the drawings.

<First Embodiment> FIG. 1 shows a first embodiment of the optical fiber link system according to the present invention.

The optical fiber link system of the first embodiment is a system used between a radio control station and a radio base station in mobile communication such as a mobile phone. The wireless control station includes a laser diode 101, and the wireless base station includes an optical lens 111, a mixing circuit 10, and a power amplifier 31.
1, an antenna 321 is provided. The wireless control station and the wireless base station are connected by an optical fiber cable 121.

The optical fiber link system of the first embodiment collects the laser diode 101 for converting the intermediate frequency signal of the frequency fIF into an optical signal, the optical fiber cable 121 for transmitting the optical signal, and the optical signal. Mixing circuit 1
The optical lens 111 input to 0 and the input optical signal are photoelectrically converted into an intermediate frequency signal, a local oscillation signal of frequency f0 is generated by itself, the intermediate frequency signal and the local oscillation signal are mixed, and the frequency fIF and the frequency f0 are mixed. And a carrier frequency f0
The mixing circuit 10 has an input / output terminal and a transistor 1 that includes a power amplifier 311 that selectively amplifies only a + fIF transmission signal and an antenna 321 that radiates a power-amplified electric signal in free space. And a feedback circuit between the base and the emitter of the transistor 1 and a transistor 1 having a non-linear characteristic of mixing two electric signals with the active region of the above and outputting a signal having a sum and a difference of frequencies of the respective electric signals. It is characterized by having.

In FIG. 1, the intermediate frequency signal is the terminal T
It is input to the laser diode 101 via 1. The intermediate frequency signal is a frequency f obtained by frequency-modulating a carrier signal according to a baseband signal such as a voice signal or a data signal.
This is the IF signal. The laser diode 101 converts an optical signal of a predetermined wavelength generated by itself into an optical signal intensity-modulated according to the input intermediate frequency signal. The optical signal is transmitted through the optical fiber cable 121, collected by the optical lens 111, and applied to the active region between the base and collector of the transistor 1 of the mixing circuit 10. The mixing circuit 10 photoelectrically converts the optical signal into an intermediate frequency signal of frequency fIF, generates a local oscillation signal of frequency f0 by itself, and further mixes the intermediate frequency signal and the local oscillation signal,
The intermediate frequency signal is generated as a transmission signal of carrier frequency f0 + fIF, a signal of frequency f0-fIF, a signal of frequency 2f0, a signal of frequency 2fIF, a signal of frequency f0, and a signal of frequency fIF. The transmission signal is input to the power amplifier 311 via the capacitor 51 together with the other mixed signals. The power amplifier 311 power-amplifies only the transmission signal. The power-amplified transmission signal is radiated into free space via the antenna 321.

Next, the structure and operation of the mixing circuit 10 will be described in detail.

The mixing circuit 10 includes a transistor 1, a strip conductor 11, a dielectric resonator 5, a resistor 21, a coil 31,
The capacitor 41, the capacitor 51, and the dielectric substrate 75 are included. The emitter of the transistor 1 is grounded via a capacitor 41 and a coil 31 that are connected in parallel with each other, and the base of the transistor 1 has a strip conductor 11 and a terminating resistor 21 connected to the other end of the strip conductor 11. Grounded through. Further, the collector of the transistor 1 has an output capacitor 5
1 is connected. The dielectric resonator 5 is formed in a cylindrical shape, and the diameter D and the axial length L thereof are set to predetermined values so that the resonance frequency of the TE ₀₁ δ mode is set to the frequency f 0 in advance. Has been done. Further, as shown in FIG. 2, the strip conductor 11 is formed on the upper surface of the dielectric substrate 75 having the ground conductor 85 on the back surface, and constitutes a microstrip line together with the dielectric substrate 75. The dielectric resonator 5 is provided on the upper surface of the dielectric substrate 75 so as to be adjacent to the strip conductor 11 at a distance d1 so as to be electromagnetically coupled, and from the base of the transistor 1 to the dielectric resonator 5. It is arranged so that the distance to the intersection of the strip conductor 11 and the surface that intersects the strip conductor 11 at a right angle, including the center line in the axial direction, is l1.

With the above configuration, the transistor 1
A feedback circuit is formed between the base and emitter of the. Here, the feedback circuit is composed of a series feedback circuit including the capacitor 41 and an internal capacitance between the base and emitter of the transistor 1. Also, an input circuit is connected to the base of the transistor 1. As shown in FIG. 2, the microstrip line and the dielectric resonator 5, which are the input circuits, are arranged in the direction of the magnetic field 91 of the microstrip line and the dielectric resonator when an oscillation signal of frequency f0 flows in the strip conductor 11. And the direction of the magnetic field 90 generated when is excited, and magnetic field coupling occurs. Regarding the strength of magnetic field coupling between the dielectric resonator 5 and the microstrip line, a predetermined strength of coupling can be obtained by setting the distance d1 between the dielectric resonator 5 and the strip conductor 11 to a predetermined value. .

Further, let ZD be the impedance of the transistor 1 viewed from the base side of the transistor 1, Rd be the absolute value of the resistance of the transistor 1 viewed from the base side of the transistor 1, and Xd be the reactance of the transistor 1 viewed from the base side of the transistor 1. , ZD = -Rd + jXd. Let ZR be the impedance from the base of the transistor 1 to the dielectric resonator 5 side, Rr be the resistance from the base of the transistor 1 to the dielectric resonator side, and Xr be the reactance from the base of the transistor to the dielectric resonator 5 side. ZR = Rr + jXr. The mixing circuit 10 shown in FIG.
Shows an equivalent circuit when operates as an oscillator. The equivalent circuit is a dielectric resonator 5 in which a transmission line TL having a length l1 in the microstrip line, a capacitance C0, a resistance R0, and an inductance L0 are connected in parallel.
, A terminating resistor 21, an impedance ZDA including the negative resistance of the transistor 1, and a load resistor RL. Here, the parallel resonant circuit including the capacitance C0, the resistor R0, and the inductance L0 and the terminating resistor 21 are connected in series to one terminal of the transmission line TL, and the other terminal of the transmission line TL is connected to the other terminal. Has an impedance ZDA and a load resistance RL connected in parallel. Further, in FIG. 17, the impedance when the right side in the figure from the line FF ′ is the above impedance ZD, and the impedance when the left side in the figure from the line FF ′ is the above impedance ZR. In order for the mixing circuit 10 to oscillate at the frequency f0, the resistors Rd and R
r, reactance Xd, and reactance Xr need to satisfy the following equations 1 and 2.

[0056]

[Formula 1] Rd ≧ Rr

[0057]

[Formula 2] Xd + Xr = 0

The resistance Rr can be reduced by strongly coupling the dielectric resonator 5 to the microstrip line. The resistance Rd can be increased by setting the capacitance of the capacitor 41 and the inductance of the coil 31 to appropriate values. As described above, the resistance Rd and the resistance Rr can be set so as to satisfy the expression 1.

The value of the reactance Xd is the value of the capacitor 41
And the value of the inductance of the coil 31. On the other hand, the reactance Xr depends on the distance l1, and the distance l
It can be arbitrarily set by changing 1. Generally, the frequency dependence of the impedance ZD when the transistor 1 is viewed from the base side of the transistor 1 is smaller than the frequency dependence of the impedance ZR. Therefore, the distance
Equation 2 can be satisfied by setting l1 to a predetermined value.

As described above, by setting the capacitance of the capacitor 41, the inductance of the coil 31, the distance l1 and the distance d1 to predetermined values, the mixing circuit 10 generates a local oscillation signal of frequency f0.

Further, the dielectric resonator 5 operates as a resonator of the parallel resonant circuit of L0, C0, R0 in the mixing circuit 10 as shown in FIG. Here, since the unloaded Q of the dielectric resonator 5 is large, it is possible to increase the load Q as a resonator when coupled to the microstrip line, whereby the mixed circuit 1
0 generates a local oscillation signal whose frequency is stabilized and which has low noise.

Next, as the transistor 1, for example, a transistor having a photoelectric conversion function such as HBT (heterojunction bipolar transistor) is used. The optical signal applied to the active region between the base and collector of the transistor 1 is absorbed by the active region between the base and collector of the transistor 1, and the active signal between the base and collector of the transistor 1 is absorbed. Generate a number of electron-hole pairs proportional to the intensity. In the transistor 1, the holes flow into the base from the active region between the base and the collector,
By accumulating in the base, a voltage proportional to the intensity of the optical signal is generated between the base and the emitter. That is, the amplitude proportional to the intermediate frequency signal and the frequency f
A voltage with IF is generated between the base and emitter of transistor 1. As a result, in the transistor 1, electrons are injected from the emitter to the base, and a base current having an amplitude proportional to the voltage and the same frequency fIF as the voltage is generated. If the base width of the transistor 1 is set to be shorter than that of the electron diffusion layer, the base current is amplified by the current amplification function of the transistor 1. Due to such a mechanism, the optical signal applied to the active region between the base and the emitter of the transistor 1 has an amplitude proportional to the intermediate frequency signal and the same frequency f as the intermediate frequency.
It is converted into an electric signal having IF.

Next, assuming that the voltage between the base and the emitter of the transistor 1 is Vbe and the current flowing through the collector of the transistor 1 is Ic, the relationship between the voltage Vbe and the current Ic is shown in FIG. 3, and the transistor 1 has the voltage Vbe. When is set to a predetermined range, the voltage-current relationship exhibits a non-linear characteristic with no linearity. In general, the non-linear characteristic of the transistor 1 is expressed by Equation 3.

[0064]

[Number 3] ^{Ic = aVbe + bVbe 2 + cVbe} 3 + dVbe 4 + .........

As the transistor 1, the coefficient c of the third or higher order,
When using a transistor in which the coefficients d, ... Are extremely smaller than the coefficients a and b, Equation 3 can be expressed as Equation 4.

[0066]

[Equation 4] Ic = aVbe + bVbe ²

The base-emitter voltage by the photoelectrically converted intermediate frequency signal is Vs, the amplitude is Es, and the angular frequency is ω.
If s, then ωs = 2π × fIF and Vs = Es [cos
(ωs × t)]. If the voltage between the base and the emitter generated by the local oscillation signal is Vl, the amplitude is El, and the angular frequency is ωl, then ωl = 2π × f0, and Vl =
It can be expressed as El [cos (ωl × t)]. Further, if the DC bias voltage between the base and the emitter is Vb, then Vbe = Vb + Vs
It can be expressed as + Vl. By substituting these equations into the equation 4, the equation 4 is expressed as the equation 5.

[0068]

[Equation 5] Ic = A + Bcos (ωs × t) + Ccos (ωl × t) + Dc
os (2 × ωs × t) + Ecos (2 × ωl × t) + Fcos [(ωl + ω
s) × t] + Gcos [(ωl−ωs) × t]

In Equation 5, A, B, C, D, E, F and G are constants determined by the values of a, b, Vb, Es and El, respectively. Also, in the equation 5, A is a DC current signal, and Bcos (ωs × t)
Is the frequency fIF signal, Ccos (ωl × t) is the frequency f0 signal, and Dcos (2 × ωs × t) is the frequency 2fI.
The signal of F, the term of Ecos (2 × ωl × t) is the signal of frequency 2f0, and the term of Fcos [(ωl + ωs) × t] is the frequency fIF + f0.
Signal of Gcos [(ωl−ωs) × t] is frequency f0−f
Each signal of IF is shown.

As described above, the transistor 1 exhibits a non-linear characteristic by setting the DC bias voltage Vb to an appropriate value, and by the non-linear operation, the intermediate frequency signal of the frequency fIF photoelectrically converted and the local part of the frequency f0. Mixing the oscillation signal, the signal of frequency f0-fI and the frequency f0 + fIF
, The signal of frequency fIF, the signal of frequency f0, the signal of frequency 2fIF, the signal of frequency 2f0, and the direct current signal are generated in the collector.

The signals of the respective frequencies are input to the power amplifier 311 via the capacitor 51 excluding the direct current signal. The power amplifier 311 frequency-selectively power-amplifies only the transmission signal of frequency f0 + fIF among the input signals. The power-amplified transmission signal is radiated into the free space via the antenna 321.

In the above first embodiment, the optical fiber link system can be miniaturized without the need to separately provide a local oscillation circuit as in the conventional example.

In the above first embodiment, the HBT (heterojunction bipolar transistor) is used as the transistor 1, but the present invention is not limited to this, and the HEM is used.
Other transistors having a photoelectric conversion function such as T (high electron mobility transistor) may be used.

In the above first embodiment, the power amplifier 311 is used.
, Which is configured to amplify only the transmission signal of frequency f0 + fIF in a frequency selective manner, the present invention is not limited to this, and has a power gain for a signal in a wide frequency range including the transmission signal of frequency f0 + fIF. Using a power amplifier,
Between the power amplifier and the capacitor 51, the frequency f0
A configuration may be adopted in which a bandpass filter that passes only the + fIF transmission signal is arranged.

In the first embodiment described above, in the transistor 1, in the relation between the collector current Ic and the voltage between the base and the emitter, the coefficient c, the coefficient d, ... Are extremely small compared to the coefficient a and the coefficient b. Although a transistor having characteristics is used, this is because when a transistor having a non-linear characteristic in which coefficient c, coefficient d, ... Is not sufficiently small compared to coefficient a and coefficient b is used,
This is because more unnecessary signals are generated and the configuration of the power amplifier 311 becomes complicated. For example, in Equation 3, if a transistor whose third-order coefficient c is not sufficiently small with respect to the first-order coefficient a and the second-order coefficient b and cannot be ignored, the frequency 3f0
Signal, frequency 3fIF signal, frequency f0-2fIF signal, frequency f0 + 2fIF signal, frequency 2f0 + fIF
Signal of 2f0-fIF occurs. Therefore, the power amplifier 311 needs to be configured not to amplify the unnecessary signal. As described above, the transistor 1 has a nonlinear characteristic in which the coefficient c, the coefficient d, ... Are extremely smaller than the coefficient a and the coefficient b in the relationship between the collector current Ic and the voltage between the base and the emitter. This simplifies the structure of the power amplifier 311 and, when a wide band power amplifier is used, simplifies the structure of the bandpass filter inserted in front of the power amplifier. From the above, the transistor 1 has a nonlinear characteristic in which the coefficient c, the coefficient d, ... Are extremely smaller than the coefficient a and the coefficient b in the relationship between the collector current Ic and the voltage between the base and the emitter. It is preferable that the coefficient a is
Is smaller than the coefficient b, but the present invention is not limited to this, and a transistor having a non-linear characteristic that is not sufficiently small compared to the coefficients a, c, d ,. May be.

In the above first embodiment, the microstrip line is used as the transmission line coupled to the dielectric resonator, but other transmission lines such as strip line, slot line, coplanar line may be used.

Although the cylindrical dielectric resonator is used in the first embodiment as described above, the present invention is not limited to this, and another shape such as a prism may be used. Further, although the TE mode is used as the resonance mode of the dielectric resonator, the present invention is not limited to this, and other modes such as the TM mode may be used.

Although the dielectric resonator is used in the first embodiment as described above, the present invention is not limited to this, and another resonator having a large unloaded Q such as a cavity resonator may be used.

In the first embodiment described above, the carrier frequency f0
Although the + fIF signal is used as the transmission signal, the present invention is not limited to this, and another mixed signal, for example, the frequency f0-fIF is used.
The signal may be used as the transmission signal. In this case, the power amplifier 311 is configured to frequency-selectively amplify the power of only the signals of the frequencies f0 to fIF.

FIG. 4 is a modification of the first embodiment of the optical fiber link system according to the present invention. This modified example of the first embodiment uses a ring resonator instead of the dielectric resonator 5 of the first embodiment. Dielectric substrate 75
The upper surface of the ring-shaped conductor 6 is spaced a distance d1 from the strip conductor 11 and from the base of the transistor 1,
A ring resonator is formed so that the distance between the strip conductor 11 and a plane that includes the center line of the ring conductor 6 perpendicular to the dielectric substrate 75 and intersects the strip conductor 11 at a right angle is l1. I am configuring. The ring resonator is one in which resonance occurs at a frequency at which an electric signal makes one phase around the line formed by the ring-shaped conductor 6, and is set in advance so as to resonate at a frequency f0. As shown, the magnetic field 93 of the ring resonator and the magnetic field 91 of the microstrip line are magnetically coupled. The modified example of the first embodiment having the above configuration operates in the same manner as the first embodiment. In the modification of the first embodiment described above, the ring resonator can be formed on the same substrate as the microstrip line, and the mixing circuit 10 can be formed.
Simplifies the configuration. Also, it can be made into an MMIC.

<Second Embodiment> FIG. 6 shows a second embodiment of the optical fiber link system according to the present invention. The same parts as those in the first embodiment of FIG. 1 are designated by the same reference numerals.

The optical fiber link system of the second embodiment is provided with an anti-phase distributor 221 and laser diodes 101 and 102 in the radio control station, and the input intermediate frequency signals have two intermediate frequencies having a phase difference of π. Split into signals,
The optical signals are converted into optical signals and transmitted to the radio base stations via the optical fiber cables 121 and 122, respectively.
0, in-phase combiner 231, power amplifier 311, antenna 3
21, the mixing circuits 10 and 20 share the dielectric resonator 5, and the mixing circuits 10 and 20 have a phase difference π with respect to each other.
Is configured to generate a local oscillation signal of frequency f0, and the in-phase combiner 231 is configured to suppress the local oscillation signal of frequency f0.

In FIG. 6, the intermediate frequency signal of frequency fIF is input to the anti-phase distributor 221 via the terminal T1. The anti-phase distributor 221 performs anti-phase distribution on the input intermediate frequency signals into two intermediate frequency signals so as to have a phase difference of π. One of the distributed first intermediate frequency signals is input to the laser diode 101. The laser diode 101 converts an optical signal of a predetermined wavelength generated by itself into a first optical signal intensity-modulated according to the input first intermediate frequency signal. The first optical signal is transmitted through the optical fiber cable 121, is condensed by the optical lens 111, and is transmitted to the base of the transistor 1 of the mixing circuit 10.
The active area between the collectors is illuminated. The mixing circuit 10
The first optical signal is photoelectrically converted into a first intermediate frequency signal, a first local oscillation signal of frequency f0 is generated by itself, the first intermediate frequency signal and the first local oscillation signal are mixed, and a carrier wave is generated. A transmission signal of frequency f0 + fIF, a signal of frequency f0-fIF, a signal of frequency 2f0, a signal of frequency 2fIF, a signal of frequency f0, and a signal of frequency fIF are generated. The transmission signal is input to the in-phase combiner 231 via the capacitor 51 together with the other mixed signals.

On the other hand, the second intermediate frequency signal whose phase is delayed by π compared with the first intermediate frequency signal distributed by the anti-phase distributor 221 is input to the laser diode 102. The laser diode 102 converts an optical signal of a predetermined wavelength generated by itself into a second optical signal intensity-modulated according to the input second intermediate frequency signal. The second optical signal is transmitted through the optical fiber cable 122, collected by the optical lens 112, and applied to the active region between the base and collector of the transistor 2 of the mixing circuit 20. The mixing circuit 20 photoelectrically converts the second optical signal into a second intermediate frequency signal, and has a frequency f0 and a phase difference π with the first local oscillation signal generated inside the mixing circuit 10. The second local oscillation signal is generated, the second intermediate frequency signal and the second local oscillation signal are mixed, and the carrier frequency f0 + f
IF transmission signal, frequency f0-fIF signal, frequency 2f0 signal, frequency 2fIF signal, and mixing circuit 10
Signal of frequency f0 having a phase difference of π with the signal of frequency f0 generated in 1
A signal of frequency fIF, which is delayed in phase by π compared with the signal of F, is generated. The transmission signal of carrier frequency f0 + fIF is input to the in-phase combiner 231 via the capacitor 52 together with the other mixed signals.

The in-phase combiner 231 suppresses the signal of the frequency f0 and the signal of the frequency fIF among the input signals.
Transmission signal of carrier frequency f0 + fIF and frequency f0-fIF
Signal, the signal of frequency 2f0 and the signal of frequency 2fIF are combined in phase and output to the power amplifier 311. Power amplifier 3
11 is the carrier frequency f0 + f in each of the input signals
It is configured such that only the IF transmission signal is frequency-selectively power-amplified and signals having other frequencies are suppressed, and only the transmission signal of the carrier frequency f0 + fIF is power-amplified and radiated into the free space via the antenna 321. To do.

Next, the configurations of the mixing circuits 10 and 20 and the local oscillation operation will be described in detail. The emitter of the transistor 1 is grounded via a capacitor 41 and a coil 31 which are connected in parallel to each other, and the base of the transistor 1 has a strip conductor 11 and a strip conductor 11 respectively.
Is grounded through a terminating resistor 21 connected to the other end of the. Further, the collector of the transistor 1 is connected to one input terminal of the in-phase combiner 231 via the output capacitor 51. On the other hand, the emitter of the transistor 2 is grounded via a capacitor 42 and a coil 32 that are connected in parallel to each other, and the base of the transistor 2 is a strip conductor 12 and a terminating resistor connected to the other end of the strip conductor 12. It is grounded via 22. Further, the collector of the transistor 2 is the output capacitor 52.
Is connected to the other input terminal of the in-phase combiner 231 via. Both the strip conductor 11 and the strip conductor 12 are parallel to each other on the upper surface of the dielectric substrate 75 having the ground conductor 85 on the back surface thereof, and are directed from the transistor 1 toward the terminating resistor 21 and from the transistor 2 toward the terminating resistor 22. The dielectric substrate 75 and the dielectric substrate 75 form first and second microstrip lines, respectively. Further, on the upper surface of the dielectric substrate 75, the dielectric resonator 5 is separated from the strip conductor 11 and the strip conductor 12 by a distance d1 and a distance d2 from the strip conductor 11 and the strip conductor 12, respectively. A surface that is provided in proximity to the conductor 12 so as to be electromagnetically coupled and that includes the axial centerline of the dielectric resonator 5 from the base of the transistor 1 and that intersects the strip conductor 11 and the strip conductor 12 at a right angle and the strip conductor. The distance to the intersection of 11 is l1, and the distance from the base of the transistor 2 to the intersection of the strip conductor 12 and the plane including the axial center line of the dielectric resonator 5 and intersecting at right angles with the strip conductor 11 and the strip conductor 12. l
It is arranged so that it becomes 2. Furthermore, distance l1 and distance l
2 is configured to have substantially the same length, and the distance d1 and the distance d2 are configured to be substantially equal.

With the above configuration, the transistor 1
A feedback circuit is formed between the base and the emitter of the transistor 2 and the transistor 2.

At this time, the first microstrip line and the second strip line and the dielectric resonator 5 are arranged as shown in FIG.
As shown in FIG.
When two oscillating signals of opposite frequency of frequency f0 flow to 2,
First microstripline magnetic field 91 generated
And the direction of the magnetic field 92 of the second microstrip line coincide with the direction of the magnetic field 90 generated when the dielectric resonator 5 is excited, and magnetic field coupling occurs. Furthermore, the distance
Since l1 and the distance l2 have almost the same length, the mixing circuit 10
And the mixing circuit 20 have a frequency f0 having a phase difference of π.
Generates a local oscillation signal of.

By operating as described above, the in-phase combiner 231 operates at the frequency f0 generated by the mixing circuits 10 and 20.
And the signal of frequency fIF are suppressed.

In the second embodiment described above, the signal of frequency f0 and the frequency of the signals generated by the mixing circuits 10 and 20 are used.
The in-phase combiner 231 suppresses the fIF signal, and the configuration of the power amplifier 311 can be simplified.

In the above second embodiment, the microstrip line is used as the transmission line coupled to the dielectric resonator, but other transmission lines such as strip line, slot line, coplanar line may be used. As the dielectric resonator coupled to the transmission line, the one that resonates in the TE mode at the frequency f0 is used, but another mode such as the TM mode may be used. Further, another resonator such as a cavity resonator may be used.

In the above second embodiment, the carrier frequency f0
Although the + fIF signal is used as the transmission signal, the present invention is not limited to this, and other mixed signals such as a signal having a frequency f0−fIF may be used. In this case, the power amplifier 311 is configured to frequency-selectively amplify the power of only the signals of the frequencies f0 to fIF.

FIG. 8 is a modification of the second embodiment of the optical fiber link system according to the present invention. The modification of the second embodiment is different from the second embodiment in FIG. 6 in that a ring resonator is used instead of the dielectric resonator 5. As shown in FIG. 9, the first microstrip line, the second microstrip line, and the ring resonator, when the oscillation signals of frequencies f0 opposite to each other flow in the strip conductor 11 and the strip conductor 12, as shown in FIG. The direction of the magnetic field 91 of the microstrip line and the direction of the magnetic field 92 of the second microstrip line are the same as the direction of the magnetic field 93 generated when the ring resonator is excited.
Magnetic field coupling. In this way, the mixing circuit 10 and the mixing circuit 20 generate the local oscillation signal of the frequency f0 having the phase difference π with each other. As described above, even if the ring resonator is used instead of the dielectric resonator 6, the optical fiber link system similar to that of the second embodiment can be configured. In the optical fiber link system of the modified example of the second embodiment described above, the ring resonator can be formed on the same substrate as the first microstrip line and the second microstrip line, and the ring resonators of the mixing circuits 10 and 20 can be formed. Easy to configure. Furthermore, the mixing circuits 10 and 20 can be made into an MMIC including a ring resonator.

<Third Embodiment> FIG. 10 shows a third embodiment of the optical fiber link system according to the present invention. The same components as those in the second embodiment of FIG. 6 are designated by the same reference numerals. There is.
The optical fiber link system of the third embodiment is shown in FIG.
Differences from the second embodiment are as follows. (a) An in-phase distributor 251 is used instead of the anti-phase distributor 221 of the second embodiment. (b) A π / 2 phase shifter 262 is arranged between the in-phase distributor 251 and the laser diode 102. (c) The π / 2 phase shifter 242 is arranged between the in-phase combiner 231 and the capacitor 52.

The optical fiber link system according to the third embodiment having the above-described structure has a laser diode 101, an optical fiber cable 121, a lens 111, and a mixing circuit 1.
Signal of each frequency output to the in-phase combiner 231 via 0, the laser diode 102 and the optical fiber cable 1
The in-phase combiner 23 is set by setting the phase difference between the signal of each frequency output to the in-phase combiner 231 through the lens 22, the lens 112, and the mixing circuit 20 to a predetermined value.
1 is configured to suppress a signal of frequency f0-fIF.

The difference in operation from the second embodiment will be described in detail below. The in-phase distributor 251 distributes the input intermediate frequency signals in-phase so that they have the same phase. One of the distributed first intermediate frequency signals is input to the laser diode 101. Meanwhile, the in-phase distributor 251
The other intermediate frequency signal distributed by is input to the π / 2 phase shifter 262. The π / 2 phase shifter 262 converts the input intermediate frequency signal into a third intermediate frequency signal having a phase delayed by π / 2 with respect to the signal input to the laser diode 101. It is input to the laser diode 102. The π / 2 phase shifter 242 is generated by the mixing circuit 20,
Carrier frequency f0 + f, which is advanced in phase by π / 2 compared with the transmission signal of carrier frequency f0 + fIF generated in mixing circuit 10.
The transmission signal of IF and the frequency f0 generated in the mixing circuit 10
The frequency f0-fIF whose phase is delayed by 3π / 2 compared with the signal of -fIF, the signal of frequency 2f0, and the frequency whose phase is delayed by π compared with the signal of frequency 2fIF generated in the mixing circuit 10. The phase is advanced by π compared to the signal of 2fIF and the frequency f0 generated by the mixing circuit 10, and the phase is delayed by π / 2 compared with the signal of the frequency fIF generated by the mixing circuit 10. The signal of frequency fIF is mixed with the transmission signal of carrier frequency f0 + fIF and mixing circuit 1
The signal of frequency f0-fIF which is advanced in phase by π compared with the signal of frequency f0-fIF generated at 0 and the frequency 2f0 whose phase is delayed by π / 2 compared with the signal of frequency 2f0 generated by the mixing circuit 10 Signal of frequency f0 generated by the mixing circuit 10, and a signal of frequency 2fIF delayed by 3π / 2 in comparison with the signal of frequency 2fIF generated by the mixing circuit 10.
The signal of the frequency f0, which is advanced by π / 2 in comparison with the signal of, and the signal of the frequency fIF, which is delayed in phase by π compared with the signal of the frequency fIF generated in the mixing circuit 10, are converted, and the in-phase combiner 231 Output to.

By the above operation, the in-phase combiner 2
Reference numeral 31 suppresses the signal of frequency f0−fIF, synthesizes the transmission signal of carrier frequency f0 + fIF, the signal of frequency 2f0, the signal of frequency 2fIF, the signal of frequency f0, and the signal of frequency fIF, and outputs the power amplifier 311.

In the third embodiment, the in-phase combiner 231 is used.
However, the signals of the frequencies f0-fIF generated by the mixing circuits 10 and 20 are suppressed, and the configuration of the power amplifier 311 is simplified.

In the third embodiment described above, the microstrip line is used as the transmission line coupled to the dielectric resonator 5, but other transmission lines such as a strip line, a slot line and a coplanar line may be used. . As the dielectric resonator coupled to the transmission line, the one that resonates in the TE mode at the frequency f0 is used, but another mode such as the TM mode may be used. Further, another resonator such as a cavity resonator may be used.

In the third embodiment described above, the frequency f0 + fIF
However, the present invention is not limited to this, and other mixed signals such as signals of frequencies f0-fIF may be used. In this case, the phase shifter 242 includes the capacitor 5
1 and the in-phase combiner 231.

In the above third embodiment, the mixing circuits 10 and 2 are
At 0, the local oscillation signals that oscillate are configured to have a phase difference π with each other, but the present invention is not limited to this and may be configured to have the same phase.

FIG. 11 is a modification of the optical fiber link system of the third embodiment according to the present invention. The same parts as those in the third embodiment of FIG. 8 are designated by the same reference numerals. FIG.
The modified example of the third embodiment is different from the third embodiment of FIG. 10 in that a ring resonator is used instead of the dielectric resonator 5. The modification of the third embodiment configured as described above operates in the same manner as the third embodiment of FIG. In the modified example of the third embodiment configured as described above, the ring resonator can be formed on the same substrate as the first microstrip line and the second microstrip line, and the mixing circuit 10, 20 can be formed. Can be easily configured. Further, the mixing circuits 10 and 20 can be implemented as MMIC.

<Fourth Embodiment> FIG. 12 shows a fourth embodiment of the optical fiber link system according to the present invention.

In the optical fiber link system of the fourth embodiment, the in-phase distributor 251 and the anti-phase distributor 22 are connected to the radio control station.
1,223, laser diodes 101,102,103,1
04, a phase shifter 262, and converts the input intermediate frequency signal into four-divided intermediate frequency signals each having a phase difference of π / 2, converts each into an optical signal, and respectively converts the optical fiber cables 121, 122, 123,124 to the wireless base station, while the optical bases 111,112,113,114, the mixing circuits 10,20,
30 and 40, in-phase combiners 231, 233 and 241, a phase shifter 272, a power amplifier 311, and an antenna 321. The in-phase combiners 231 and 233 and the in-phase combiner 241 respectively mix the signal of frequency f0 and the frequency f0. -FIF signal is configured to be suppressed, and mixing circuits 10, 20, 3
0 and 40 share the dielectric resonator 5 and generate local oscillation signals having a predetermined phase difference and a frequency f0.

In FIG. 12, the intermediate frequency signal of frequency fIF is input to the in-phase distributor 251 via the terminal T1. The in-phase distributor 251 in-phase distributes the input intermediate frequency signals into two intermediate frequency signals so that they have the same phase. One of the distributed intermediate frequency signals is input to the anti-phase distributor 221. The anti-phase distributor 221 compares the input intermediate frequency signal with the first intermediate frequency signal of frequency fIF and the frequency fIF, and compares the intermediate frequency signal with the intermediate frequency signal to obtain a second intermediate frequency signal whose phase is delayed by π. Distribute. The first intermediate frequency signal is the laser diode 10
1 is input. The laser diode 101 converts an optical signal of a predetermined wavelength generated by itself into a first optical signal intensity-modulated according to the input first intermediate frequency signal. The first optical signal is transmitted through the optical fiber cable 121, is condensed by the optical lens 111, and is mixed by the mixing circuit 10.
The active region between the base and collector of the transistor 1 is irradiated. The mixing circuit 10 outputs the first optical signal to the frequency fI.
The first intermediate frequency signal of F is photoelectrically converted and the frequency f
A first local oscillation signal of 0 is generated, and the first intermediate frequency signal and the first local oscillation signal are mixed to obtain a carrier frequency.
A transmission signal of f0 + fIF, a signal of frequency f0-fIF, a signal of frequency 2f0, a signal of frequency 2fIF, a signal of frequency f0, and a signal of frequency fIF are generated. Carrier frequency f0
The + fIF transmission signal is input to the in-phase combiner 231 via the capacitor 51 together with the other mixed signal.

On the other hand, the second intermediate frequency signal is input to the laser diode 102. The laser diode 102 converts an optical signal of a predetermined wavelength generated by itself into a second optical signal intensity-modulated according to the input second intermediate frequency signal. The second optical signal is transmitted through the optical fiber cable 122, collected by the optical lens 112, and applied to the active region between the base and collector of the transistor 2 of the mixing circuit 20. The mixing circuit 20 photoelectrically converts the second optical signal into a second intermediate frequency signal, and has a frequency f0 and a second local oscillation having a phase difference π with the local oscillation signal generated inside the mixing circuit 10. A signal is generated, the second intermediate frequency signal and the second local oscillation signal are mixed, and a transmission signal of carrier frequency f0 + fIF, a signal of frequency f0-fIF, a signal of frequency 2f0, and a signal of frequency 2fIF are generated. ,
Generates a signal of frequency f0 having a phase difference π between the signal of frequency f0 generated by the mixing circuit 10 and a signal of frequency fIF delayed by π compared with the signal of frequency fIF generated by the mixing circuit 10. To do. The transmission signal of the carrier frequency f0 + fIF is combined with the mixed signal and the capacitor 52.
Is input to the in-phase combiner 231 via.

The other intermediate frequency signal distributed by the in-phase distributor 251 is input to the π / 2 phase shifter 262. The π / 2 phase shifter 262 converts the input intermediate frequency signal so that the phase is delayed by π / 2 with respect to the signal input to the laser diode 101. Laser diode 10
The intermediate frequency signal whose phase is delayed by π / 2 from the signal input to 1 is input to the anti-phase distributor 223, and the third intermediate signal whose phase is delayed by π / 2 from the signal input to the laser diode 101. The phase is distributed in antiphase to the fourth intermediate frequency signal whose phase is delayed by 3π / 2 as compared with the frequency signal and the signal input to the laser diode 101.

One of the third intermediate frequency signals distributed by the anti-phase distributor 223 is input to the laser diode 103. The laser diode 103 converts an optical signal of a predetermined wavelength generated by itself into a third optical signal intensity-modulated according to the input third intermediate frequency signal. The third optical signal is transmitted through the optical fiber cable 123, collected by the optical lens 113, and applied to the active region between the base and collector of the transistor 3 of the mixing circuit 30. The mixing circuit 30 photoelectrically converts the third optical signal into a third intermediate frequency signal, and has the frequency f0 by itself and the mixing circuit 1
Carrier wave generated in the mixing circuit 10 by generating a third local oscillation signal having a phase difference π with the local oscillation signal generated inside 0, further mixing the third intermediate frequency signal and the third local oscillation signal, and generating in the mixing circuit 10. A transmission signal of a carrier frequency f0 + fIF with a phase advanced by π / 2 compared to the transmission signal of the frequency f0 + fIF,
A signal having a frequency f0-fIF with a phase advanced by 3π / 2 as compared with a signal having a frequency f0-fIF generated in the mixing circuit 10;
Signal 2f0 and frequency 2f generated in the mixing circuit 10
The signal of the frequency 2fIF whose phase is delayed by π compared with the signal of IF, the signal of the frequency f0 whose phase is advanced by π compared with the signal of the frequency f0 generated in the mixing circuit 10, and the mixing circuit 1
Compared to the signal of frequency fIF generated at 0, the phase is π /
And a signal having a frequency fIF delayed by two. The transmission signal having the carrier frequency f0 + fIF is input to the in-phase combiner 233 via the capacitor 53 together with the other mixed signals.

The other fourth intermediate frequency signal distributed by the anti-phase distributor 223 is input to the laser diode 104. The laser diode 104 converts an optical signal of a predetermined wavelength generated by itself into a fourth optical signal intensity-modulated according to the input fourth intermediate frequency signal. The fourth optical signal is transmitted through the optical fiber cable 124, collected by the optical lens 114, and applied to the active area between the base and collector of the transistor 4 of the mixing circuit 40. The mixing circuit 40 photoelectrically converts the fourth optical signal into a fourth intermediate frequency signal, and generates a fourth local oscillation signal of frequency f0 having no phase difference from the first local oscillation signal by itself. , The fourth intermediate frequency signal and the fourth local oscillation signal are mixed, and the carrier frequency f0 + f generated in the mixing circuit 10 is generated.
The carrier frequency f0 + fIF whose phase is advanced by π / 2 compared with the IF transmitted signal and the frequency f0-fIF whose phase is advanced by 3π / 2 compared with the signal of frequency f0-fIF generated in the mixing circuit 10. And the signal of frequency 2f0,
The phase is advanced by π / 2 in comparison with the signal of frequency 2fIF which is delayed in phase by π compared with the signal of frequency 2fIF generated in mixing circuit 10 and the signal of frequency f0 and the signal of frequency fIF generated in mixing circuit 10. And a signal of frequency fIF. The transmission signal of the carrier frequency f0 + fIF is input to the in-phase combiner 233 via the capacitor 54 together with the other mixed signals. The converted signals are input to the in-phase combiner 233 via the capacitor 54.

The in-phase combiner 231 includes capacitors 51, 5
Among the signals of the respective frequencies input via 2, the signals of the frequency f0 and the frequency fIF that are input in opposite phases are suppressed, and the transmission signal of the carrier frequency f0 + fIF and the frequency f0-fIF that are input in the same phase are suppressed. Signal, the signal of frequency 2f0, and the signal of frequency 2fIF are respectively combined and output to the in-phase combiner 241.

The in-phase combiner 233 includes capacitors 53, 5
Among the signals of the respective frequencies input via 4, the signal of the frequency f0 and the signal of the frequency fIF which are input in opposite phases are suppressed, and the transmission signal of the carrier frequency f0 + fIF generated in the mixing circuit 10 which is input in the same phase. Compared with the transmission signal having the carrier frequency f0 + fIF which is advanced by π / 2 in comparison with the signal having the frequency f0−fIF generated in the mixing circuit 10, the phase is 3π.
/ 2 The signal of frequency f0-fIF advanced, the signal of frequency 2f0 and the signal of frequency 2fIF generated in the mixing circuit 10 are compared with each other to synthesize a signal of frequency 2fIF delayed by π,
Output to the π / 2 phase shifter 272.

The π / 2 phase shifter 272 compares each input signal with the transmission signal of the carrier frequency f0 + fIF and the signal of the frequency f0−fIF generated in the mixing circuit 10, and the frequency f0− advanced by π. The phase of the signal of fIF is delayed by π / 2 in comparison with the signal of the frequency 2f0 generated in the mixing circuit 10, and the phase is delayed by 3π / 2 in comparison of the signal of frequency 2f0 generated by the mixing circuit 10 and the signal of the frequency 2fIF generated in mixing circuit 10. It is converted into a signal of frequency 2fIF and output to the in-phase combiner 241.

The in-phase combiner 241 suppresses the signals of the frequencies f0-fIF input in opposite phases among the signals of the respective frequencies input, and transmits the transmission signal of the carrier frequency f0 + fIF, the signal of the frequency 2f0, and the frequency 2fIF. The signals are combined and output to the power amplifier 311.

The power amplifier 311 has a carrier frequency f0 + f
It is preconfigured to frequency-selectively power-amplify the transmission signal of IF and suppress signals having other frequencies. Only the transmission signal of carrier frequency f0 + fIF is power-amplified and radiated into free space via antenna 311. To do.

Further, the mixing circuits 10, 20, 30, 40 will be described in detail. The emitter of the transistor 1 has a capacitor 41 and a coil 3 which are connected in parallel with each other.
1 is grounded, and the base of the transistor 1 is grounded via the strip conductor 11 and a terminating resistor 21 connected to the other end of the strip conductor 11. Further, an output capacitor 51 is connected to the collector of the transistor 1. On the other hand, the emitter of the transistor 2 is grounded via a capacitor 42 and a coil 32 which are connected in parallel with each other, and the base of the transistor 2 has a strip conductor 12 and a strip conductor 12 respectively.
Is grounded through a terminating resistor 22 connected to the other end of the. Further, an output capacitor 52 is connected to the collector of the transistor 2. The emitter of the transistor 3 is grounded via a capacitor 43 and a coil 33 that are connected in parallel to each other, and the base of the transistor 3 has a strip conductor 13 and a strip conductor 13
Is grounded through a terminating resistor 23 connected to the other end of the. Further, an output capacitor 53 is connected to the collector of the transistor 3. On the other hand, transistor 4
The emitters of are capacitors 44 connected in parallel with each other.
And the coil 34, and the base of the transistor 4 is grounded via the strip conductor 14 and the terminating resistor 24 connected to the other end of the strip conductor 14. Further, an output capacitor 54 is connected to the collector of the transistor 4. As described above, feedback circuits are formed between the bases and emitters of the transistors 1, 2, 3, and 4, respectively, similarly to the first embodiment.

The strip conductors 11, 12, 13, 14 and the cylindrical dielectric resonator 5 similar to the first embodiment are formed on the upper surface of the dielectric substrate 75 as follows. The strip conductors 11, 12, 13, 14 have substantially the same length in the longitudinal direction, are orthogonal to each other around the dielectric resonator 5, and are arranged in the order of the strip conductors 11, 12, 13, 14 and strip. The center points of the conductors 11, 12, 13, 14 in the longitudinal direction are electromagnetically coupled to the circumferences of the four cylinders that are separated from each other by an angle of 90 ° about the center of the cylinder of the dielectric resonator 5. Thus, they are provided close to each other. The dielectric resonator 5 and the strip conductors 11, 12, 13, 14 are arranged with a distance d1, d2, d3, d4, respectively. Here, the pair of strip conductors 11 and 14 and the pair of strip conductors 12 and 13 are parallel to each other. Further, one end of the strip conductor 11 connected to the resistor 21 and one end of the strip conductor 13 connected to the resistor 23 are close to each other, and one end of the strip conductor 12 connected to the resistor 22 and the strip conductor 14 connected to the resistor 24. Is configured to be close to one end of the. Further, the strip conductors 11, 12, 13, 14 are connected to the transistor 1,
The distance to each base of 2, 3 and 4 is l1,
l2, l3, l4, the distance l1 and the distance l2
And the distance l3 and the distance l4 are set to be substantially equal. Furthermore, the distance d1, the distance d2, the distance d3, and the distance d4 are set to be substantially equal.

With the above configuration, the first microstrip line and the dielectric resonator 5, the second microstrip line and the dielectric resonator 5, and the third microstrip line and the dielectric resonator 5 and the In the four microstrip lines and the dielectric resonator 5, the oscillation signals of frequencies f0 opposite to each other flow in the strip conductor 11 and the strip conductor 12, respectively, and the oscillation signals of the frequency f0 in the strip conductor 11 and the strip conductor 14 have the same phase. When the oscillating signal flows and the oscillating signals having the frequencies f0 and having the opposite frequencies to each other flow in the strip conductor 13 and the strip conductor 14, respectively, magnetic field coupling is performed. In this way, the mixing circuit 10 and the mixing circuit 20, and the mixing circuit 30 and the mixing circuit 40 generate the local oscillation signals having the frequencies f0 of opposite phases to each other.
0 generates local oscillation signals of frequency f0 in phase with each other.

By performing the above operation, the in-phase combiners 231 and 233 cause the mixing circuits 10, 20, 30, and 40 to operate.
The signal of frequency f0 and the signal of frequency fIF which are generated are suppressed, and the in-phase combiner 241 suppresses the signal of frequency f0-fIF.

In the above fourth embodiment, the mixing circuit 10,
Frequency f in the signal of each frequency generated in 20, 30, 40
The in-phase synthesizers 231, 233, 241 suppress the 0-fIF signal, the f0 signal, and the frequency fIF signal, and the power amplifier 3
The configuration of 11 can be simplified. In the above fourth embodiment, the signal of carrier frequency f0 + fIF is used as the transmission signal, but the present invention is not limited to this, and the signal of frequency f0-fIF may be used. In this case, the phase shifter 272 is arranged between the in-phase combiner 231 and the in-phase combiner 241.

FIG. 13 is a first modification of the fourth embodiment of the optical fiber link system according to the present invention. The optical fiber link system of the first modification of the fourth embodiment is different from the optical fiber link system of the fourth embodiment in that a ring resonator is used instead of the dielectric resonator 5. . The first microstrip line and the ring resonator, the second microstrip line and the ring resonator, the third microstrip line and the ring resonator, and the fourth microstrip line and the ring resonator include strip conductor 11 and strip. Oscillation signals of opposite phases of frequency f0 flow through the conductors 12 and the frequencies of the strip conductors 11 and 14 are respectively different.
When the oscillating signals having the same phase of f0 flow and the oscillating signals of the opposite phase having the frequency f0 respectively flow in the strip conductor 13 and the strip conductor 14, magnetic field coupling is performed.
In this way, the mixing circuit 10 and the mixing circuit 20, and the mixing circuit 30 and the mixing circuit 40 generate the local oscillation signals of the frequency f0 having mutually opposite phases, and the mixing circuit 10 and the mixing circuit 40 and the mixing circuit 20 and the mixing circuit 30 mutually A local oscillation signal of frequency f0 in phase is generated. With the above configuration, the optical fiber link system of the first modification of the fourth embodiment operates in the same way as the optical fiber link system of the fourth embodiment. The optical fiber link system of the first modification of the fourth embodiment configured as described above, the ring resonator is a first microstrip line, a second microstrip line and a third microstrip line. The fourth microstrip line and the mixed circuit 10, 20, 30, 40 can be formed on the same substrate.
Can be easily configured. Also, the mixing circuit 10,
It is also possible to make 20, 30, 40 into an MMIC.

FIG. 14 is a second modification of the fourth embodiment of the optical fiber link system according to the present invention. The optical fiber link system of the second modified example of the fourth embodiment has strip conductors 11a, 12b, 13c, 14d on the outer periphery of the dielectric resonator 5 as compared with the optical fiber link system of the fourth embodiment. The difference is that it is formed by bending along.
With the above configuration, the optical fiber link system of the second modified example of the fourth embodiment operates in the same manner as the optical fiber link system of the fourth embodiment. With the above configuration, the magnetic field coupling between the first, second, third, and fourth microstrip lines and the dielectric resonator 5 can be strengthened.

[0122]

[0123]

As described in detail above, according to the optical fiber link system of the present invention, photoelectric conversion is performed which has an input / output terminal and converts an optical signal incident on the active region of the transistor into an electrical signal. A transistor having a non-linear characteristic that mixes a function and two electric signals and outputs a signal having a sum and difference frequencies of respective electric signals;
A mixing circuit including a feedback circuit connected to the transistor, wherein the transistor converts the optical signal incident on the active region after intensity modulation by an electric signal having a first frequency into the photoelectric conversion function. While performing photoelectric conversion to the electric signal using the feedback circuit, the feedback circuit oscillates and generates a local oscillation signal having a second frequency, and mixes the electric signal and the local oscillation signal using the nonlinear characteristic. Then, an optical fiber link system including two mixing circuits for generating an electric signal having each of a sum and a difference of the first frequency and the second frequency at an output terminal of the transistor, The input circuit of one of the two mixing circuits and the input circuit of the other mixing circuit of the two mixing circuits are provided close to each other so as to be electromagnetically coupled to each other. And having a resonant frequency equal to the second frequency, the flows in the input circuit of the mixing circuit of one said 1
And the second oscillation signal flowing in the input circuit of the other mixing circuit are in opposite phases to each other, and the direction of the magnetic field generated when the first oscillation signal flows and the second oscillation signal
The direction of the magnetic field generated when the oscillation signal of
A resonator provided so as to match the direction of a magnetic field generated when the resonator is excited, and an electric signal having a first frequency that is input are first and second so as to have a phase difference of π with respect to each other. A first distribution means for distributing the second electric signal into two, a first conversion means for converting the first electric signal into a first optical signal, and a first conversion means for converting the first optical signal into the first optical signal. A first optical means for irradiating the active region of the transistor of the mixing circuit, a second converting means for converting the second electric signal into a second optical signal, and a second converting means for converting the second optical signal into the second optical signal. The second optical means for irradiating the active region of the transistor of the other mixing circuit, the electric signal output from the one mixing circuit and the electric signal output from the other mixing circuit are combined in phase. A synthesizing means for outputting and an electric signal output from the synthesizing means And selectively filtering an electric signal having a sum frequency of the first frequency and the second frequency or an electric signal having a difference frequency between the first frequency and the second frequency. And filtering means. Therefore,
Compared with the optical fiber link system configured by using the conventional mixing circuit of FIG. 15, it is not necessary to separately configure a local oscillator in the radio base station, and the band pass filter 32 is further provided.
5 is not required, and the configuration of the wireless base station can be simplified. Compared to the conventional optical fiber link system of FIG. 16, the radio control station does not need the harmonic generator 313 and the radio base station does not need the photodiode 323 and the band pass filter 322. Both configurations of the control station can be simplified. Furthermore, since the optical fiber cable 302 is not required, the configuration of the entire optical fiber link system can be simplified. Therefore, according to the present invention, a compact and inexpensive optical fiber link system can be provided.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing an optical fiber link system that is a first embodiment according to the present invention.

FIG. 2 is a cross-sectional view of a coupling portion between a microstrip line and a dielectric resonator of the optical fiber link system of FIG.

3 is a graph showing a non-linear relationship between a collector current and a base-emitter voltage of a transistor of the optical fiber link system of FIG.

FIG. 4 is a circuit diagram showing an optical fiber link system which is a modification of the first embodiment according to the present invention.

5 is a cross-sectional view of a coupling portion between a microstrip line and a ring resonator of the optical fiber link system of FIG.

FIG. 6 is a circuit diagram showing an optical fiber link system which is a second embodiment according to the present invention.

7 is a cross-sectional view of a coupling portion between a microstrip line and a dielectric resonator of the optical fiber link system of FIG.

FIG. 8 is a circuit diagram showing an optical fiber link system which is a modified example of the second embodiment according to the present invention.

9 is a cross-sectional view of a coupling portion between a microstrip line and a ring resonator of the optical fiber link system of FIG.

FIG. 10 is a circuit diagram showing an optical fiber link system according to a third embodiment of the present invention.

FIG. 11 is a circuit diagram showing an optical fiber link system which is a modification of the third embodiment according to the present invention.

FIG. 12 is a circuit diagram showing an optical fiber link system according to a fourth embodiment of the present invention.

FIG. 13 is a circuit diagram showing an optical fiber link system which is a first modification of the fourth embodiment according to the present invention.

FIG. 14 is a circuit diagram showing an optical fiber link system which is a second modification of the fourth embodiment according to the present invention.

FIG. 15 is a circuit diagram showing a conventional optical fiber link system.

FIG. 16 is a block diagram showing another conventional optical fiber link system.

FIG. 17 is an equivalent circuit when the mixing circuit 10 of FIG. 1 operates as an oscillator.

[Explanation of symbols]

10, 20, 30, 40, 70, 80, 321 ... Mixed circuit 1, 2, 3, 4, 7, 8 ... Transistor 11, 12, 13, 14, 11a, 12b, 13c, 14d ... Strip conductor 21, 22 , 23, 24 ... Termination resistance 31, 32, 33, 34 ... Coil 41, 42, 43, 44, 51, 52, 53, 54 ... Capacitor 5 ... Dielectric resonator 6 ... Ring conductor 90 ... Dielectric resonator Magnetic field 93 ... Magnetic field of ring resonator 91, 92 ... Magnetic field of microstrip line 101, 102, 103, 104, 312, 313 ... Laser diode 111, 112, 113, 114 ... Optical lens 121, 122, 123, 124, 301, 302 ... Optical fiber cables 221, 223 ... Anti-phase distributor 251 ... In-phase distributor 242, 262, 272 ... π / 2 phase shifter 231, 233, 241 ... In-phase combiner 311, 330 ... Power amplifier 321, 331 … Antenna 326 ... Local oscillator 323 ... Photodiode 322, 324, 325 ... Bandpass filter 310 ... Electrical / optical converter 320 ... Optical / electrical converter T1 ... Intermediate frequency signal input terminal T5 ... Voice signal input terminal T6 ... Local oscillation signal Input terminal T7 ... Transmission signal output terminal C0 ... Capacitor R0 ... Resistance RL ... Load resistance L0 ... Coil TL ... Transmission line ZDA ... Impedance

Continuation of front page (56) Reference JP-A-5-259744 (JP, A) JP-A-6-196933 (JP, A) JP-A-55-68747 (JP, A) JP-A-5-129841 (JP , A) JP-A-2-128506 (JP, A)

Claims (9)

(57) [Claims] 1. A photoelectric conversion function of converting an optical signal incident on an active region of a transistor into an electric signal having an input / output terminal, and a sum of frequencies of two electric signals mixed with each other. A mixed circuit comprising a transistor having a non-linear characteristic for outputting a signal of a frequency of a difference and a feedback circuit connected to the transistor, the transistor being intensity-modulated by an electric signal having a first frequency. After that, while photoelectrically converting the optical signal incident on the active region into the electrical signal by using the photoelectric conversion function, the feedback circuit oscillates and generates a local oscillation signal having a second frequency, The electric signal and the local oscillation signal are mixed by using the non-linear characteristic, and an electric signal having each of the sum and difference frequencies of the first frequency and the second frequency is mixed with the above-mentioned non-linear characteristic. An optical fiber link system comprising two mixing circuits generated at the output terminal of a transistor, wherein an input circuit of one of the two mixing circuits and a mixing circuit of the other of the two mixing circuits are provided. A first oscillating signal that is provided in close proximity to the input circuit of the circuit so as to be electromagnetically coupled, has a resonance frequency equal to the second frequency, and that flows into the input circuit of the one mixing circuit; The second oscillating signal flowing in the input circuit of the other mixing circuit has a phase opposite to each other, and the direction of the magnetic field generated when the first oscillating signal flows and the second oscillating signal flow A resonator provided so that the direction of the magnetic field sometimes generated coincides with the direction of the magnetic field generated when the resonator is excited, and an electric signal having the first frequency to be input is mutually π First to have a phase difference of And a first distribution means for distributing the first electric signal into a second optical signal, a first conversion means for converting the first electric signal into a first optical signal, and a first conversion means for converting the first optical signal into the first optical signal. A first optical means for irradiating the active region of the transistor of one of the mixing circuits, a second conversion means for converting the second electric signal into a second optical signal, and a second optical signal. To the active region of the transistor of the other mixing circuit, and an electric signal output from the one mixing circuit and an electric signal output from the other mixing circuit in the same phase And outputting from the electric signal output from the synthesizing means, an electric signal having a sum frequency of the first frequency and the second frequency or the first frequency and the second frequency. Selectively select electrical signals that have a frequency that is the difference from the frequency Fiber optic link system, characterized in that a filtering means for waves. 2. The optical fiber link system according to claim 1, wherein the resonator is a dielectric resonator. 3. The optical fiber link system according to claim 1, wherein the resonator is a ring resonator. 4. A photoelectric conversion function which has an input / output terminal and which converts an optical signal incident on an active region of a transistor into an electric signal, and a sum of frequencies of respective electric signals obtained by mixing two electric signals. A mixed circuit comprising a transistor having a non-linear characteristic for outputting a signal of a frequency of a difference and a feedback circuit connected to the transistor, the transistor being intensity-modulated by an electric signal having a first frequency. After that, while photoelectrically converting the optical signal incident on the active region into the electrical signal by using the photoelectric conversion function, the feedback circuit oscillates and generates a local oscillation signal having a second frequency, The electric signal and the local oscillation signal are mixed by using the non-linear characteristic, and an electric signal having each of the sum and difference frequencies of the first frequency and the second frequency is mixed with the above-mentioned non-linear characteristic. An optical fiber link system comprising two mixing circuits generated at the output terminal of a transistor, wherein an input circuit of one of the two mixing circuits and a mixing circuit of the other of the two mixing circuits are provided. Is provided in close proximity to the input circuit of the circuit so as to be electromagnetically coupled, has a resonance frequency equal to the second frequency, and has the first frequency.
Direction of the magnetic field generated when the second oscillation signal flows and the direction of the magnetic field generated when the second oscillation signal flows are the direction of the magnetic field generated when the resonator is excited. A resonator provided so as to match with each other, and a first distributing means for distributing an inputted electric signal having the first frequency into two parts, that is, a first electric signal and a second electric signal having a phase difference of π / 2. A first conversion means for converting the first electric signal into a first optical signal in an electric / optical manner, and an active transistor of one of the two mixing circuits for converting the first optical signal. First optical means for irradiating the region, second converting means for converting the other second electric signal, which is divided into two by the first distributing means, into a second optical signal, and the second converting means. The second optical signal is transferred to the transistor of the other mixing circuit of the above two mixing circuits. The second optical means for irradiating the moving region, the electric signal output from the one mixing circuit and the electric signal output from the other mixing circuit, and one of the electric signals is phase-shifted by π / 2. Then, the first combining means for combining and outputting, and from the electric signal output from the first combining means, the electric signal having the sum of the first frequency and the second frequency and the frequency, or An optical fiber link system comprising: a filtering unit that selectively filters an electrical signal having a frequency that is a difference between a first frequency and the second frequency. 5. The optical fiber link system according to claim 4, wherein the resonator is a dielectric resonator. 6. The optical fiber link system according to claim 4, wherein the resonator is a ring resonator. 7. A photoelectric conversion function of having an input / output terminal and converting an optical signal incident on an active region of a transistor into an electric signal and a sum of frequencies of two electric signals mixed with each other. A mixed circuit comprising a transistor having a non-linear characteristic for outputting a signal of a frequency different from the above, and a feedback circuit connected to the transistor, wherein the transistor is intensity-modulated by an electric signal having a first frequency. After that, while photoelectrically converting the optical signal incident on the active region into the electric signal by using the photoelectric conversion function, the feedback circuit oscillates and generates a local oscillation signal having a second frequency, The electric signal and the local oscillation signal are mixed by using the non-linear characteristic, and an electric signal having each of the sum and difference frequencies of the first frequency and the second frequency is mixed with the above-mentioned non-linear characteristic. An optical fiber link system comprising four mixing circuits generated at output terminals of a transistor, wherein an input circuit of one first mixing circuit of the four mixing circuits and four mixing circuits are provided. Of one of the four mixing circuits, one of the four mixing circuits of the third mixing circuit, and one of the four mixing circuits of The first mixing circuit is provided so as to be electromagnetically coupled to the input circuit of the fourth mixing circuit, has a resonance frequency equal to the second frequency, and flows into the input circuit of the first mixing circuit. And the second oscillating signal flowing in the input circuit of the second mixing circuit have opposite phases, and the first oscillating signal and the third oscillating signal flowing in the input circuit of the third mixing circuit The oscillating signal has a phase opposite to that of the first mixing circuit and flows to the input circuit of the first mixing circuit. One oscillating signal,
When the fourth oscillation signals flowing in the input circuit of the fourth mixing circuit are in phase with each other, the direction of the magnetic field generated when the first oscillation signal flows and the second oscillation signal are The direction of the magnetic field generated when flowing, the direction of the magnetic field generated when the third oscillation signal flows, and the direction of the magnetic field generated when the fourth oscillation signal flows,
A resonator provided so as to match the direction of a magnetic field generated when the resonator is excited, and an electric signal having a first frequency that is input are divided into two parts having a phase difference of π / 2. A first distributing means; a second distributing means for distributing one of the two electric signals divided by the first distributing means into a first electric signal and a second electric signal so as to have a phase difference π with each other; First converting means for converting the first electric signal into a first optical signal by electric / optical conversion; and first optical means for irradiating the active area of the transistor of the first mixed circuit with the first optical signal. A second conversion means for converting the second electric signal into a second optical signal, and a second conversion means for irradiating the active region of the transistor of the second mixing circuit with the second optical signal. The optical means and the other of the two distributed by the first distributing means Third distributing means for distributing the air signal into third and fourth electric signals so as to have a phase difference of π, and a third distributing means for converting the third electric signal into a third optical signal by electric / optical conversion. Conversion means; third optical means for irradiating the active region of the transistor of the third mixing circuit with the third optical signal; and electrical-optical conversion of the fourth electrical signal into a fourth optical signal. Fourth conversion means, fourth optical means for irradiating the active region of the transistor of the fourth mixing circuit with the fourth optical signal, electric signals output from the first mixing circuit, and the fourth The first combining means for combining and outputting the electric signals output from the second mixing circuit in phase, the electric signal output from the third mixing circuit, and the electric signal output from the fourth mixing circuit. Second synthesizing means for synthesizing and outputting signals in phase, and the first synthesizing means Third synthesizing means for synthesizing and outputting one of the electrical signals output from the means and the electrical signal output from the second synthesizing means after phase shifting one electrical signal by π / 2; From the electric signal output from the third synthesizing means, an electric signal having a sum frequency of the first frequency and the second frequency or an electric signal having a difference frequency between the first frequency and the second frequency. An optical fiber link system comprising: a filtering means for selectively filtering a signal. 8. The optical fiber link system according to claim 7, wherein the resonator is a dielectric resonator. 9. The optical fiber link system according to claim 7, wherein the resonator is a ring resonator.