JP2886390B2 - Optical microwave mixing circuit and optical microwave frequency conversion circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a microwave monolithic integrated circuit (MMIC) for processing signals in a frequency band such as a microwave band, a quasi-millimeter wave band, or a millimeter wave band of about 1 GHz or more. The present invention relates to an optical microwave mixing circuit and an optical microwave frequency conversion circuit to be formed.

[0002]

2. Description of the Related Art FIG. 7 is a block diagram of an optical microwave frequency conversion circuit provided with a conventional optical microwave mixing circuit.

[0003] In FIG 7, an intermediate frequency signal of frequency f _IF is input to the laser diode 1 is an electrical-optical converter through an intermediate frequency signal input terminal T1, the electrical-optical conversion (hereinafter, referred optic converter.) The converted optical signal, which is intensity-modulated by the intermediate frequency signal, is connected to the photodiode PD having one end connected to the first terminal of the three-terminal circulator 90 and the other end grounded via the optical fiber cable 2. Incident. On the other hand, the local oscillation signal having the frequency f _LO is input to the second terminal of the three-terminal circulator 90 via the local oscillation signal input terminal T2 and the impedance matching circuit 91, and then is input via the first terminal of the three-terminal circulator 90. Is input to the photodiode PD. The photodiode PD performs optical-to-electrical conversion (hereinafter, referred to as photoelectric conversion) of the incident optical signal into an electric signal, and converts the converted electric signal and the input local oscillation signal according to the input / output nonlinear characteristics. And a mixed electric signal having a frequency of, for example, a frequency f _LO ± f _IF is input to a high-pass filter (HPF) 93 via a three-terminal circulator 90 and an impedance matching circuit 92, f _RF
After filtering the high-frequency signal having = f _LO + f _IF , the signal is output via the high-frequency signal output terminal T3.

[0004]

However, in the conventional optical microwave frequency conversion circuit, a photodiode PD is used, and it is difficult to convert the photodiode PD into an MMIC. It is difficult to convert MMIC to MMIC. Also,
Since the two-terminal photodiode PD is used, it is necessary to provide a local oscillation signal separation circuit such as the circulator 90, which increases the size of the circuit. Therefore, there is a problem that the frequency conversion circuit cannot be downsized.

Further, there has been a problem that it is difficult to convert the frequency conversion circuit and an active circuit such as an amplifier circuit having an FET into MMICs so as to obtain predetermined performance. Furthermore, in order to process signals in the microwave band or higher, it is necessary to use an ultra-high-speed photodiode PD, but this is still at the research level and has the problem of being expensive.

A first object of the present invention is to solve the above problems and to provide an inexpensive optical / microwave mixing circuit which can be reduced in size and weight as compared with the conventional example.

A second object of the present invention is to convert an input electric signal into an electric signal having a predetermined frequency, which can be reduced in size and weight as compared with the conventional example, and which is inexpensive. It is an object of the present invention to provide an optical microwave frequency conversion circuit.

[0008]

An optical microwave frequency conversion circuit according to claim 1 of the present invention is an optical microwave frequency conversion circuit comprising an optical microwave mixing circuit and a filtering means, The optical microwave mixing circuit has a first electrode and a second electrode and has a non-linear characteristic, and converts an input first electrical signal having a first frequency into an optical signal. Conversion means; and optical means for irradiating the active area of the transistor with an optical signal that has been converted from light to light by the conversion means, wherein the transistor converts the irradiated light signal into a second electric signal. Performing electrical conversion, mixing the second electrical signal with a third electrical signal having a second frequency different from the first frequency and input to the first electrode using the nonlinear characteristic hand,
An electric signal having each frequency of a sum and a difference between the first frequency and the second frequency is generated at the second electrode, and the filtering means is generated at the second electrode by the transistor. Filtering an electric signal having the sum frequency or an electric signal having the difference frequency from the electric signal having the sum and difference frequencies of the first frequency and the second frequency. And

[0009]

According to a second aspect of the present invention, there is provided an optical microwave frequency conversion circuit comprising: a first transistor having a first electrode and a second electrode and having non-linear characteristics; a third transistor and a fourth electrode; A second transistor having an electrode and having a non-linear characteristic substantially the same as the non-linear characteristic of the first transistor; First distributing means for splitting into two so as to have a phase difference, and first conversion for electro-optically converting one of the first electric signals split into two by the first distributing means into a first optical signal. Means for irradiating an active area of the first transistor with a first optical signal which has been subjected to electrical / optical conversion by the first converting means; The other first electrical signal into a second optical signal A second conversion unit for performing electrical-to-optical conversion, a second optical unit for irradiating the second optical signal electrical-to-optically converted by the second conversion unit to an active region of the second transistor, A second frequency different from the first frequency
The input second electric signal having the frequency of 2 is divided into two so as to be in phase with each other, one of the divided electric signals is output to the first electrode of the first transistor, and Second distribution means for outputting the other electrical signal to the third electrode of the second transistor, wherein the first transistor transmits the irradiated first optical signal to a third electrode. Optical-to-electrical conversion into an electric signal, and mixing the third electric signal and the electric signal input to the first electrode from the second distribution means using the non-linear characteristic to form a first mixing The second transistor converts the irradiated second optical signal into a fourth electric signal, and outputs the fourth electric signal and the second electric signal from the second distribution unit. The electric signal input to the third electrode is mixed using the above-mentioned nonlinear characteristic. The second mixed signal and outputs the,
Further, the first and second mixed signals are combined to output an electric signal having a frequency equal to the sum of the first and second frequencies, and the first and second mixed signals are combined. And a hybrid circuit for outputting an electric signal having a frequency different from the frequency of the electric signal.

According to a third aspect of the present invention, there is provided an optical microwave mixing circuit comprising: a first transistor having a first electrode and a second electrode and having non-linear characteristics; a third electrode and a fourth electrode; A second transistor having non-linear characteristics substantially the same as the non-linear characteristics of the first transistor, and an input first electric signal having a first frequency being distributed in two phases in opposite phases to each other. First distributing means for converting the first electric signal, which has been divided into two by the first distributing means, into a first optical signal, and a first converting means; First optical means for irradiating an active area of the first transistor with a first optical signal which has been electro-optically converted by the means, and the other first electric signal divided into two by the second distribution means Conversion for converting the optical signal into a second optical signal A stage, and a second optical means for irradiating a second optical signal converted electric-light by the second converting means into the active region of the second transistor, the first
The input second electric signal having a second frequency different from the input frequency is divided into two by a predetermined first phase difference, and one of the divided electric signals is divided by the first transistor of the first transistor. A second distribution means for outputting the other electric signal after the distribution to the third electrode of the second transistor while outputting the other electric signal to the first electrode, wherein the first transistor emits the electric signal. The first optical signal is optically / electrically converted into a third electric signal, and the third electric signal and the electric signal input from the second distribution means to the first electrode are converted into the non-linear characteristic. Output a first mixed signal by mixing using
The second transistor optically / electrically converts the irradiated second optical signal into a fourth electric signal, and transmits the fourth electric signal to the third electrode from the second distribution unit. The input electric signal is mixed using the non-linear characteristic to output a second mixed signal, and further, the first and second mixed signals are combined with each other with a predetermined second phase difference, The second
And a synthesizing unit for outputting an electric signal having a sum and a difference between the first frequency and the second frequency.

The optical microwave mixing circuit according to claim 4 is the optical microwave mixing circuit according to claim 3,
The first phase difference is π, and the second phase difference is zero.

Further, in the optical microwave mixing circuit according to a fifth aspect, in the optical microwave mixing circuit according to the third aspect, the first phase difference is 0 and the second phase difference is π. It is characterized by the following.

Furthermore, the optical microwave frequency conversion circuit according to claim 6 is an optical microwave mixing circuit according to claim 3, 4 or 5, and the first microwave output from the synthesizing means.
Filtering means for filtering an electric signal having the sum frequency or an electric signal having the difference frequency from an electric signal having the sum and difference frequencies of the sum of the second frequency and the second frequency. It is characterized by the following.

[0015]

In the optical / microwave mixing circuit according to the first aspect, the converting means converts the input first electric signal having the first frequency into an optical signal by optical / optical conversion. The optical signal that has been subjected to the electrical / optical conversion by the conversion means is applied to the active region of the transistor. Next, the transistor optically / electrically converts the irradiated optical signal into a second electric signal, and has the second electric signal and the first frequency having a second frequency different from the first frequency. The third electric signal input to the first electrode and the third electric signal are mixed using the non-linear characteristic, and the electric signal having each frequency of the sum and the difference between the first frequency and the second frequency is converted to the second electric signal. Occurs on the electrodes. Therefore, the first electric signal having the first frequency is frequency-converted into an electric signal having each frequency of the sum and difference of the first frequency and the second frequency. Next, in the optical microwave frequency conversion circuit, the filtering means converts each frequency of the sum and difference of the first frequency and the second frequency generated at the second electrode by the transistor. The electric signal having the frequency of the sum or the electric signal having the frequency of the difference is filtered from the electric signal.

[0016]

In the optical microwave frequency conversion circuit according to the present invention, the first distribution means may receive the first input signal.
Are divided into two such that the first electric signals have a phase difference of π / 2 from each other, and the first conversion means converts one of the first electric signals divided into two by the first distribution means. The first optical means converts the signal into a first optical signal, and the first optical means converts the first optical signal, which has been electro-optically converted by the first converting means, into an active area of the first transistor. Irradiate. On the other hand, the second converter converts the other first electric signal, which has been divided into two by the second distributor, into a second optical signal by electro-optical conversion. The second optical signal, which has been subjected to the electrical / optical conversion by the second conversion means, is applied to the active region of the second transistor. Next, the second distribution means divides the input second electric signals having the second frequency different from the first frequency into two so as to be in phase with each other, and distributes one of the electric signals after the distribution. A signal is output to the first electrode of the first transistor, and the other divided electric signal is output to the third electrode of the second transistor. Further, the first transistor optically / electrically converts the irradiated first optical signal into a third electric signal, and outputs the third electric signal and the first electric signal from the second distribution unit. The electric signal input to the electrode is mixed using the nonlinear characteristic to output a first mixed signal, while the second transistor converts the irradiated second optical signal into a fourth electric signal. The optical signal is converted into a signal, and the fourth electric signal is mixed with the electric signal input to the third electrode from the second distribution means by using the non-linear characteristic to form a second mixed signal. Is output. Further, the hybrid circuit combines the first and second mixed signals to generate the first frequency and the second mixed signal.
And an electric signal having a frequency equal to the difference between the first frequency and the second frequency is output. Therefore, the first
Is converted into an electric signal having each of the sum and the difference between the first frequency and the second frequency.

According to a third aspect of the present invention, in the optical / microwave mixing circuit, the first distribution means distributes the input first electric signal having the first frequency into two opposite phases to each other, and Conversion means converts one of the first electric signals divided into two by the first distribution means into a first optical signal.
The first optical means performs light conversion, and irradiates the first optical signal, which has been electro-optically converted by the first conversion means, to the active region of the first transistor. On the other hand, the second converter converts the other first electric signal, which has been divided into two by the second distributor, into a second optical signal by electro-optical conversion. The second optical signal, which has been subjected to the electrical / optical conversion by the second conversion means, is applied to the active region of the second transistor. Next, the second distribution means distributes the input second electric signals having a second frequency different from the first frequency into two with a predetermined first phase difference from each other, and One electric signal is outputted to the first electrode of the first transistor, and the other electric signal after the distribution is outputted to the third electrode of the second transistor. Further, the first transistor optically / electrically converts the irradiated first optical signal into a third electric signal, and outputs the third electric signal and the first electric signal from the second distribution unit. Mixing the electric signal input to the electrode with the above-mentioned nonlinear characteristic to output a first mixed signal;
On the other hand, the second transistor is provided with the illuminated second transistor.
The optical signal is optically / electrically converted into a fourth electric signal,
And the electric signal input from the second distribution means to the third electrode by using the non-linear characteristic to output a second mixed signal. Further, the synthesizing means synthesizes the first and second mixed signals with a predetermined second phase difference, cancels the second electric signal, and cancels the first frequency and the second frequency. An electric signal having each frequency of the sum and the difference with the frequency is output. Therefore, the first electric signal having the first frequency is frequency-converted to an electric signal having each frequency of the sum and difference of the first frequency and the second frequency.

According to a fourth aspect of the present invention, the first phase difference is π, and the second phase difference is preferably π. Is 0.

Further, in the optical microwave mixing circuit according to claim 5, in the optical microwave mixing circuit according to claim 3, preferably, the first phase difference is zero,
The second phase difference is π.

Further, in the optical microwave frequency conversion circuit according to the present invention, the filtering means may include a difference between a sum of the first frequency and the second frequency output from the synthesizing means. An electric signal having the sum frequency or an electric signal having the difference frequency is filtered from the electric signals having the respective frequencies.

[0022]

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

<First Embodiment> FIG. 1 shows a first embodiment according to the present invention.
It is a circuit diagram which shows the optical microwave frequency conversion circuit which is an Example of FIG.

The optical microwave frequency conversion circuit of the first embodiment converts the intermediate frequency signal of the frequency f _IF into light and light by the laser diode 1 and converts the converted light signal through the optical fiber cable 2 and the optical lens 3. Then, the active region 5 of the field effect transistor (hereinafter referred to as FET) TR1 is irradiated, and the electric signal is converted by the photoelectric conversion by the FET TR1 to obtain the converted electric signal, while the local oscillation signal of the frequency f _LO (> f _IF ) is obtained. The electric signal is input to the gate electrode G of the FET TR1, the converted electric signal is mixed with the local oscillation signal by the input / output nonlinear characteristics of the FET TR1, and the mixed electric signal is input to the π-type band elimination filter 20. , Frequency f _LO
By removing the electrical signal at −f _IF, the frequency f _RF =
It is characterized in that a high-frequency signal of f _LO −f _IF is filtered and output via a high-frequency signal output terminal T3.

[0025] In FIG 1, an intermediate frequency signal of frequency f _IF is input via the intermediate frequency signal input terminal T1 to the laser diode 1 is a lightning transducer, laser diode 1 is an intermediate frequency signal which is input to electrical-optical In other words, as shown in FIG. 2, a grounded source FET is transmitted through an optical fiber cable 2 and an optical lens 3 such as a convex lens to convert the optical signal after intensity-modulating the optical signal with the intermediate frequency signal.
The light is incident on the active region 5 near the gate electrode G of TR1.
Here, in the FETTR1, an active region (active region) 5 is formed in the GaAs substrate 4 between the source electrode S and the drain electrode D and below the gate electrode G with a predetermined doping amount of an impurity such as Si. Formed optical fiber cable 2
An optical signal incident through the optical lens 3 is applied to the active area 5 with a predetermined spot beam. Also, F
The ETTR 1 has a photoelectric conversion function and has input / output nonlinear characteristics between the gate electrode G and the drain electrode D. Here, the FET TR1 preferably uses a Schottky FET (MESFET) or a high electron transfer transistor (HEMT).

The local oscillation signal input terminal T2 is grounded via the parallel stub transmission line 11, and is connected to the gate electrode G of the FET TR1 via the impedance conversion transmission line 12. Further, the drain electrode D of the FET TR1 is connected via the impedance conversion transmission line 13,
One end is connected to the other end of the parallel stub transmission line 14 grounded and the input end of the π-type band elimination filter 20. The band elimination filter 20 includes an MIM capacitor 21 and transmission lines 22 and 23 each having one end grounded. The band elimination filter 20 has a predetermined cutoff frequency that is _lower than the frequency f _LO + f _IF and higher than the frequency f _LO −f _IF. Have. Here, the input end of the band elimination filter 20 is connected to the high-frequency signal output terminal T3 via the other end of the transmission line 22, the MIM capacitor 21, and the other end of the transmission line 23.

In the optical microwave frequency conversion circuit configured as described above, the optical signal intensity-modulated by the intermediate frequency signal including the information signal input to the input terminal T1 is an FET.
The local oscillation signal input through the input terminal T2 is applied to the gate electrode G of the FET TR1 while being applied to the active region 5 of the transistor TR1. Here, the FET TR1 photoelectrically converts the incident optical signal into an electric signal proportional to the intermediate frequency signal, and mixes the electric signal after the photoelectric conversion with the local oscillation signal by using its input / output nonlinear characteristics. And
For example, the mixed electric signal including the component of the frequency f _LO ± f _IF is output to the band elimination filter 20. The band elimination filter 20 filters out the high frequency signal of the frequency f _RF = f _LO + f _IF by removing the electric signal of the frequency f _LO −f _IF and outputs the filtered signal through the high frequency signal output terminal T3. Therefore, the intermediate frequency signal of frequency f _IF is a frequency converted into a frequency f _RF = f _LO + f _IF of the high-frequency signal.

FIG. 3 shows a case where the FET TR1 is composed of a HEMT, an optical signal modulated with an intermediate frequency signal and a local oscillation signal are inputted to the HEMT, and an upper sideband signal and a lower sideband signal are detected. 7 is a graph illustrating frequency characteristics of a detection level of an output signal when only an optical signal modulated by an intermediate frequency signal is input to a HEMT for direct detection. In the experiment, the following devices were used and set as follows. (A) FET: H composed of n-type AlGaAs / InGaAs with an input / output coplanar line in an on-wafer state
EMT (gate length Lg = 0.25 μm, gate width Wg
= 100 μm) (b) Laser diode 1: 3210C laser diode manufactured by Ortel (oscillation light wavelength λ = 0.
(C) Intermediate frequency f _IF = 0.4 GHz (d) Input level of intermediate frequency signal to laser diode 1 = 10 dBm (e) Input of local oscillation signal to gate electrode G of FET TR1 Level = -4dBm

As is apparent from FIG. 3, the frequency characteristic of the direct detection signal monotonically decreases to 5 GHz, is flat to 8 GHz, and decreases again at frequencies higher than that.
On the other hand, the frequency characteristics of the upper sideband signal and the lower sideband signal obtained by optical / microwave frequency mixing are flat up to 20 GHz, and the detection level is improved at 4 GHz or higher as compared with the direct detection signal. You can see that. Therefore, it was confirmed that the device operates as an optical microwave mixing circuit similarly to the optical microwave mixing circuit using the photodiode PD of the above-described conventional example, and is capable of transmitting a signal having a bandwidth equal to or greater than the band of the device.

In the first embodiment described above, since a two-terminal photodiode PD is not used and a three-terminal FET is used, a separation circuit such as a circulator 90 is not required unlike the conventional example. The MMIC can be formed together with the circuit, and the frequency conversion circuit can be downsized.

In the first embodiment, the transmission line 1
Although 1 to 14, 22, and 23 are used, the configuration is not limited thereto, and a lumped constant element such as a spiral inductor, a meander inductor, or an MIM capacitor may be used.

<Second Embodiment> FIG. 4 shows a second embodiment according to the present invention.
It is a circuit diagram which shows the optical microwave frequency conversion circuit which is an Example of FIG.

The optical microwave frequency conversion circuit of the second embodiment converts an intermediate frequency signal having a frequency f _IF into a phase difference of π / 2.
And the converted intermediate frequency signals are electro-optically converted by the laser diodes 1a and 1b, respectively, and the converted optical signals are converted into optical fiber cables 2 respectively.
a, 2b, optical amplifiers 6a, 6b and optical lenses 3a, 3
b, the active regions of the FETs TR11 and TR12 are irradiated, and the electric signals are converted by the FETs TR1 and TR12 to obtain converted electric signals, while the frequency f _LO (>
f _IF ) and distributes the local oscillation signal in-phase to the FET TR1.
1 and TR12, the converted electric signal and the local oscillation signal are mixed according to the non-linear characteristics of the input and output of the FETs TR11 and TR12. The frequency f _UP = f _LO + f
_{It is characterized in that} the upper sideband signal of _{IF and} the lower sideband signal of frequency f _LW = f _LO −f _IF are output via output terminals T4 and T5, respectively.

In FIG. 4, an intermediate frequency signal having a frequency f _IF is input to an in-phase distributor 30 via an intermediate frequency signal input terminal T1 and distributed in phase, and one of the divided intermediate frequency signals is output to a laser diode 1a. At the same time, the other intermediate frequency signal after the distribution is output to the laser diode 1b via the π / 2 phase shifter 31. Laser diode 1a
Converts the input intermediate frequency signal into light-to-light, that is, modulates the intensity of the optical signal with the intermediate frequency signal and grounds the converted optical signal via the optical fiber cable 2a, the optical amplifier 6a, and the optical lens 3a. In the active region near the gate electrode G1 of the FET TR11. On the other hand, the laser diode 1b electro-optically converts the input intermediate frequency signal, and converts the converted optical signal via the optical fiber cable 2b, the optical amplifier 6b, and the optical lens 3b to the FE of the source ground.
The light is incident on an active region near the gate electrode G2 of the TTR12. Here, each line length is set such that the phase difference between the intermediate frequency signal included in the optical signal incident on the active region of the FET TR11 and the intermediate frequency signal included in the optical signal incident on the active region of the FET TR12 becomes π / 2. Is adjusted and set,
Preferably, each circuit is adjusted such that the amplitude of each intermediate frequency signal included in each optical signal is the same.

The local oscillation signal having the frequency f _LO is distributed in-phase by an in-phase distribution circuit 40 composed of a Wilkinson-type power distribution circuit composed of two transmission lines 41 and 42 and an absorption resistor R1, and one of the divided signals is distributed. Local oscillation signal is FE
While being input to the gate electrode G1 of the TTR11, the other local oscillation signal is input to the gate electrode G2 of the FETTR12. Here, each of the FETs TR11 and TR12 is
Each of them has a photoelectric conversion function, and has substantially the same input / output nonlinear characteristics as each other.

Further, the drain electrode D of the FET TR11
1 is a branch line type π / 2
Input to the first input terminal of the hybrid circuit 50, F
The electric signal output from the drain electrode D2 of the ETTR 12 is input to a second input terminal of the hybrid circuit 50. Here, the π / 2 hybrid circuit 50 is configured by connecting four transmission lines 51, 52, 53, and 54 each having a half wavelength on a ring, and the first and second transmission lines 51 are provided at both ends of the transmission line 51. An input terminal is connected, and first and second output terminals are connected to both ends of the transmission line. The first output terminal of the π / 2 hybrid circuit 50 is an upper sideband output terminal T4.
And the second output terminal of the π / 2 hybrid circuit 50 is connected to the lower sideband output terminal T5.

In the optical microwave frequency conversion circuit of the second embodiment configured as described above, the FET TR1
1, when each optical signal enters each active area of TR12,
Each of the FETs TR11 and TR12 photoelectrically converts an incident optical signal into electric signals P _IF1 and P _IF2 represented by the following equations (1) and (2).

[0038]

## EQU1 ## P _IF1 = A ₁ sin (2πf _IF t)

P _IF2 = A ₁ sin (2πf _IF t + π / 2) where A ₁ is the amplitude of the electric signals P _IF1 and P _IF2 .

Further, each other each local oscillation signal P _LO in-phase frequency f _LO is, the gate electrode G of FETTR11
1 is input to the gate electrode G2 of the FET TR12.
Here, the FET TR11 mixes the electric signal P _IF1 after the photoelectric conversion and the local oscillation signal P _LO by using the input / output nonlinear characteristic, and outputs the electric signal P _IF expressed by the following equation (3).
_While outputting _mix1 , the FETTR12 mixes the photoelectrically converted electric signal P _IF2 and the local oscillation signal P _LO using the input / output nonlinear characteristics, and outputs the electric signal represented by the following equation 4. Output P _mix2 .

[0040]

P _mix1 = A ₂ [sin {2π (f _LO + f _IF ) t} + sin {2π (f _LO −f _IF ) t}]

P _mix2 = A ₂ [sin {2π (f _LO + f _IF ) t + π / 2} + sin {2π (f _LO −f _IF ) t−π / 2}] where A ₂ is the electric signal P _mix1 , P _mix2 .

The electric signals P _mix1 and P _mix2 after mixing are π
When input to the / 2 hybrid circuit 50, the branch line type π / 2 hybrid circuit 50, which is a 90-degree phase synthesizing circuit, has a position of π / 2 between the first and second input terminals, as is well known. The first and second output terminals are combined with each other with a phase difference of π / 2, and the phase difference between the first input terminal and the first output terminal is π / 2. 2 has a phase difference of π /
2 and the upper sideband signal P _UP and the lower sideband signal P _LW represented by the following equations (5) and (6) can be separated and extracted at the output terminals T4 and T5. .

[0042]

P _UP = A ₃ [sin {2π (f _LO + f _IF ) t}

P _LW = A ₃ [sin {2π (f _LO −f _IF ) t} where A ₃ is the amplitude of the electric signals P _UP and P _LW .

[0043] Thus, the intermediate frequency signal of a frequency f _IF, a frequency f _LO + f _IF of the upper sideband signal P _UP, the frequency f _LO -f
_The frequency can be converted into the lower sideband signal P _{LW of the IF} and separated and extracted.

In the optical microwave frequency conversion circuit of the second embodiment configured as described above, each circuit on the left side of FIG. 4 of the optical fiber cables 2a and 2b is replaced with, for example, the radio control station 100 of the automobile telephone network. And each circuit on the right side of the optical fiber cables 2a and 2b in FIG.
By setting it to 0, it can be used for the downlink of an optical fiber link for mobile communication.

Further, the optical microwave frequency conversion circuit of the second embodiment uses a three-terminal FET instead of a two-terminal photodiode PD as in the first embodiment. As described above, the MMIC can be formed together with the peripheral circuit without using the separation circuit such as the circulator 90, and the frequency conversion circuit can be downsized.

In the second embodiment, the optical amplifier 6
Although a and 6b are used, it may be omitted when the radio control station 100 and the radio base station 200 are close to each other and the intensity of the optical signal is sufficiently large.

In the above-described second embodiment, the in-phase distribution circuit 40 composed of a Wilkinson type power distribution circuit is used. However, the present invention is not limited to this, and the present invention is not limited to this. An in-phase distribution circuit composed of parallel branches of the transmission line may be used. Instead of the branch line π / 2 hybrid circuit 50, a Lange coupler or a distributed constant coupling type directional coupler may be used.

Although the in-phase distribution circuit 40 is used in the above second embodiment, the invention is not limited to this, and an anti-phase distribution circuit may be used.

<Third Embodiment> FIG. 5 shows a third embodiment according to the present invention.
FIG. 6 is a circuit diagram showing an optical microwave frequency conversion circuit according to an embodiment of the present invention, in which the same components as those in the second embodiment of FIG.

The difference between the optical microwave frequency conversion circuit of the third embodiment and the circuit of the second embodiment shown in FIG. 4 is as follows. (A) Instead of the in-phase distributor 30 and the π / 2 phase shifter 31 of the second embodiment, an anti-phase distributor 46 including an in-phase distributor 47 and a π phase shifter 48 is used. (B) Instead of the in-phase distribution circuit 40 of the second embodiment, an anti-phase distribution circuit 43 composed of an in-phase distributor 44 and a π phase shifter 45
Is used. (C) Instead of the π / 2 hybrid circuit 50 of the second embodiment, a cascade connection circuit of an in-phase synthesis circuit 49 and a band-pass filter (BPF) 80 for band-filtering only the upper sideband signal P _UP is used. . Here, the output end of the band-pass filter 80 is connected to the high-frequency signal output terminal T3.

In the optical microwave frequency conversion circuit of the third embodiment configured as described above, the FET TR1
1, each optical signal incident on each active region of TR12 includes each intermediate frequency signal having a phase difference of π from each other,
The intermediate frequency signals are generated by the FETs TR11 and TR12. On the other hand, the local oscillation signals having opposite phases to each other are input to the gate electrodes G1 and G2 of the FETs TR11 and TR12.
After the signals are mixed in TR1 and TR12, they are in-phase synthesized by the in-phase synthesizing circuit 49. At this time, the local oscillation signal and its odd-order harmonic signal are canceled in the in-phase synthesis circuit 49, and the in-phase synthesis circuit 49 outputs the even-order harmonic signal of the local oscillation signal and the upper sideband signal of the frequency f _LO + f _IF. P _UP and the lower sideband signal P _{LW of} the frequency f _LO −f _IF are output, and the band-pass filter 80 outputs, for example, the frequency f _LO
Only the upper band signal P _{UP of} + f _IF is band-filtered and output as a high frequency signal of frequency f _RF . Therefore, the frequency f
_Since the local oscillation signal of the _LO can be suppressed without using a filter, the size of the subsequent circuit device can be reduced.

In the circuit of the third embodiment, a circuit from the anti-phase distribution circuit 43 to the in-phase synthesis circuit 49 via the FETs TR11 and TR12 can be constituted by the anti-phase distribution and in-phase synthesis circuit 81 of FIG. The circuit 81 is configured as follows from an antiphase distribution circuit using a series T branch of a slot line and an in-phase synthesis circuit using a coplanar line.

As shown in FIG. 6, two conductors 61, 6 formed at a predetermined distance from each other on a semiconductor substrate 4a.
2 constitutes the slot line 60 on the input side,
A coplanar line 70 is constituted by the center conductor 71 and two ground conductors 72 and 73 formed on both sides of the center conductor 71 with a predetermined space therebetween. The tip of the conductor 61 is connected to the gate electrode G1 of the FET TR11, and the tip of the conductor 62 is connected to the FETT.
It is connected to the gate electrode G2 of R12. FETTR1
Each of the source electrodes S1 and S2 of the TR1 and the TR12 is formed integrally and has a triangular portion having an acute angle toward the slot line 60. Further, the drain D1 of TR11 and FE
The drain D2 of the TTR 12 is connected to the center conductor 71. Therefore, the local oscillation signal input to the slot line 60 is distributed in the opposite phase, and the two FETs TR11 and TR
After input to each of the twelve gate electrodes G1 and G2, each FE
After the above-described mixing process in TTR11 and TR12, F
Electric signals output from the drain electrodes D1 and D2 of the ETTR11 and TR12 are combined in phase and output to the coplanar line 70.

In the third embodiment, the bandpass filter 80 for filtering only the upper sideband signal P _UP is used. However, the present invention is not limited to this, and only the lower sideband signal P _LW is filtered. A band pass filter may be used.

In the third embodiment, an in-phase distribution circuit is used in place of the anti-phase distribution circuit 43 and the in-phase synthesis circuit 4
9 may be replaced with an antiphase combining circuit. In this case, the operation is similar to that of the third embodiment.

<Other Embodiments> In the above embodiments, an optical microwave frequency conversion circuit is configured by combining an optical microwave mixing circuit and filters such as a band-pass filter, a high-pass filter, and a band-elimination filter. However, the present invention is not limited to this, and may be configured with a single optical microwave mixing circuit.

In the above embodiment, the FETs TR1, T
Although R11 and TR12 are used, the present invention is not limited to this, and a bipolar transistor may be used instead.

[0058]

As described in detail above, according to the optical microwave frequency conversion circuit of the first aspect of the present invention, an optical microwave frequency conversion circuit comprising an optical microwave mixing circuit and a filtering means. Wherein the optical microwave mixing circuit comprises:
A transistor having a non-linear characteristic having a first electrode and a second electrode, a converting means for converting an input first electric signal having a first frequency into an optical signal by light-to-light conversion, Optical means for irradiating the active area of the transistor with the electrical / optically converted optical signal, wherein the transistor optically / electrically converts the emitted optical signal into a second electrical signal, An electric signal and a third electric signal having a second frequency different from the first frequency and input to the first electrode are mixed using the non-linear characteristic, and the first frequency and the third frequency are mixed. An electric signal having a sum and a difference frequency with respect to the second frequency is generated at the second electrode, and the filtering means is configured to control the first frequency generated at the second electrode by the transistor. Of the sum and difference between From the electrical signal having a frequency, an electrical signal to filter having a frequency of the electrical signal or the difference with the frequency of the sum. Accordingly, an optical / microwave mixing circuit for frequency-converting the first electric signal having the first frequency into electric signals having respective frequencies of a sum and a difference between the first frequency and the second frequency, Since the above-described transistor is used instead of the two-terminal photodiode as in the conventional example, an isolation circuit such as the circulator 90 is not required, and the entire circuit can be formed as an MMIC. It is possible to provide an inexpensive optical / microwave mixing circuit while reducing the size and weight. Further, the optical microwave frequency conversion circuit includes the optical microwave mixing circuit and the filtering means, and can be formed into an MMIC, and is a small, lightweight, and inexpensive optical microwave frequency conversion circuit. Can be provided.

[0059]

According to a second aspect of the present invention, there is provided an optical microwave frequency conversion circuit comprising: a first transistor having a first electrode and a second electrode and having a non-linear characteristic;
A second transistor having a third electrode and a fourth electrode, having a nonlinear characteristic substantially the same as the nonlinear characteristic of the first transistor, and a first transistor having an input first frequency. First distributing means for distributing the electric signals into two so as to have a phase difference of π / 2, and converting one of the first electric signals divided by the first distributing means into a first optical signal. A first conversion unit for performing optical conversion, a first optical unit for irradiating an active region of the first transistor with a first optical signal that has been subjected to electrical / optical conversion by the first conversion unit, A second conversion unit for performing electrical / optical conversion of the other first electrical signal divided into two by the two distribution units into a second optical signal; and a second electrical / optical conversion unit configured to perform electrical / optical conversion by the second conversion unit. Irradiates the active region of the second transistor with the optical signal of And an input second electric signal having a second frequency different from the first frequency is divided into two so as to be in phase with each other, and one of the divided electric signals is divided into the second electric signal. Output to the first electrode of the first transistor, and output the other electric signal after the distribution to the second electrode.
A second distribution means for outputting to the third electrode of the transistor, the first transistor optically / electrically converts the irradiated first optical signal into a third electric signal,
The third electric signal is mixed with the electric signal input from the second distribution means to the first electrode by using the non-linear characteristic to output a first mixed signal, and the second mixed signal is output. The transistor optically / electrically converts the irradiated second optical signal into a fourth electric signal, and outputs the fourth electric signal and an electric signal input to the third electrode from the second distribution unit. A second mixed signal by mixing the first and second mixed signals with each other by using the non-linear characteristic, and further combining the first and second mixed signals to obtain a first and second mixed signals. A hybrid circuit that outputs an electric signal having a sum frequency and outputs an electric signal having a frequency of a difference between the first frequency and the second frequency. Accordingly, an optical microwave frequency for separating and converting the first electric signal having the first frequency into an electric signal having each frequency of the sum and difference of the first frequency and the second frequency. Since the conversion circuit is formed using the above-mentioned transistor without using a two-terminal photodiode as in the conventional example, an isolation circuit such as the circulator 90 is not required, and the entire circuit can be formed into an MMIC. It is possible to provide an inexpensive optical / microwave frequency conversion circuit while reducing the size and weight as compared with the example.

Further, in the optical / microwave mixing circuit according to claim 3 of the present invention, a first transistor having a first electrode and a second electrode and having a non-linear characteristic,
A second transistor having a non-linear characteristic substantially the same as the non-linear characteristic of the first transistor, and a first electric signal having a first input frequency. Distributing the first electric signal into two in the opposite phase to each other, and converting the first electric signal divided into two by the first distributing means into a first optical signal.
Conversion means, first optical means for irradiating an active area of the first transistor with the first optical signal which has been subjected to the electrical / optical conversion by the first conversion means, and 2 A second conversion unit for performing electrical / optical conversion of the other distributed first electrical signal into a second optical signal; and converting the second optical signal subjected to electrical / optical conversion by the second conversion unit into the second optical signal. A second optical means for irradiating the active region of the two transistors, and an input second electric signal having a second frequency different from the first frequency and divided into two by a predetermined first phase difference. And outputting one of the divided electric signals to the first electrode of the first transistor and outputting the other divided electric signal to the third electrode of the second transistor. 2 distributing means, and the first
The third transistor converts the irradiated first optical signal to a third
Optical-electrical conversion into the electric signal of the third electric signal,
The electric signal input to the first electrode from the second distribution means is mixed using the nonlinear characteristic to output a first mixed signal, and the second transistor outputs the first mixed signal. Optical-to-electrical conversion of the second optical signal into a fourth electrical signal,
The fourth electric signal is mixed with the electric signal input from the second distribution means to the third electrode by using the non-linear characteristic to output a second mixed signal. The first and second mixed signals are combined with each other with a predetermined second phase difference to cancel the second electric signal, and each of the sum and difference of the first frequency and the second frequency is calculated. Combining means for outputting an electric signal having a frequency. Accordingly, optical microwave mixing for separating and converting the frequency of the first electric signal having the first frequency into electric signals having the sum and difference frequencies of the first frequency and the second frequency. Since the circuit is formed using the above-mentioned transistor without using a two-terminal photodiode as in the conventional example, an isolation circuit such as the circulator 90 is not required, and the entire circuit can be formed into an MMIC. Small size compared to
The weight can be reduced, and an inexpensive optical / microwave mixing circuit can be provided.

Further, in the optical microwave frequency conversion circuit according to the sixth aspect, the optical microwave mixing circuit according to the third, fourth or fifth aspect, and the first frequency output from the synthesizing means and the first frequency A filtering means for filtering an electric signal having a frequency of the sum or an electric signal having a frequency of the difference from an electric signal having each frequency of a sum and a difference with the frequency of 2; Thus, it is possible to provide an optical microwave frequency conversion circuit that is small, lightweight, and inexpensive.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing an optical microwave frequency conversion circuit according to a first embodiment of the present invention.

FIG. 2 is an FET of the optical microwave frequency conversion circuit of FIG. 1;
3A and 3B are a schematic view and a cross-sectional view of a circuit portion to which an optical signal whose intensity is modulated by an intermediate frequency signal is irradiated.

FIG. 3 shows an optical microwave frequency conversion circuit of FIG. 1 in which a HEMT is used as an FET, and an optical signal modulated by an intermediate frequency signal and a local oscillation signal are input to the HEMT, and an upper sideband signal and a lower sideband are input. When a signal is detected, and for comparison, only the optical signal modulated with the intermediate frequency signal is HEMT.
7 is a graph showing the frequency characteristics of the detection level of the output signal when the detection signal is directly detected by inputting the detection signal.

FIG. 4 is a circuit diagram showing an optical microwave frequency conversion circuit according to a second embodiment of the present invention.

FIG. 5 is a circuit diagram showing an optical microwave frequency conversion circuit according to a third embodiment of the present invention.

FIG. 6 is a plan view of an antiphase distribution and inphase synthesis circuit used in the third embodiment of FIG. 5;

FIG. 7 is a block diagram of a conventional optical microwave frequency conversion circuit.

[Explanation of symbols]

 1, 1a, 1b: laser diode, 2, 2a, 2b: optical fiber cable, 3, 3a, 3b: optical lens, 6a, 6b: optical amplifier, 11, 14: transmission line for parallel stub, 12, 13: impedance Conversion transmission line, 20: π-type band elimination filter, 30: in-phase distributor, 31: π / 2 phase shifter, 40: in-phase distributor, 43: anti-phase distributor, 44: in-phase distributor, 45, 48 ... Π phase shifter, 46... In-phase distribution circuit, 47... In-phase distribution circuit, 49... In-phase synthesis circuit, 50. Π / 2 hybrid circuit, 80. , G2: gate electrode of FET, S, S1, S2: source electrode of FET, D, D1, D2: drain electrode of FET, T1: intermediate frequency signal input terminal, T2: local oscillation signal input terminal , T3: High frequency signal output terminal, T4: Upper sideband signal output terminal, T5: Lower sideband signal output signal.

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-5-22230 (JP, A) JP-A-63-59030 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) H04B 10/00-10/28 H01L 31/10-31/20 G02F 1/29-7/00

Claims (6)

(57) [Claims] 1. An optical microwave frequency conversion circuit comprising an optical microwave mixing circuit and a filtering means, wherein the optical microwave mixing circuit has a first electrode and a second electrode, and is non-linear. A transistor having characteristics; a conversion unit for converting the first electrical signal having the first frequency to an optical signal into an optical signal; an optical signal electrically and optically converted by the conversion unit; Optical means for irradiating an area, wherein the transistor optically / electrically converts the irradiated optical signal into a second electric signal, and the second electric signal and a second electric signal different from the first frequency. The third electric signal having the frequency of the first frequency and the third electric signal input to the first electrode is mixed using the non-linear characteristic, and each frequency of the sum and the difference between the first frequency and the second frequency is mixed. An electric signal having the second electrode The filtering means generates the frequency of the sum from an electric signal generated at the second electrode by the transistor and having a difference between the sum of the first frequency and the second frequency. An optical microwave frequency conversion circuit for filtering an electric signal having the above-mentioned or an electric signal having the above-mentioned difference frequency. A first transistor having a first electrode and a second electrode and having non-linear characteristics; a third transistor and a fourth electrode having substantially the same non-linear characteristics as the first transistor; A second transistor having the same non-linear characteristic, and first distributing means for distributing the input first electric signal having the first frequency into two so as to have a phase difference of π / 2 from each other. A first converting means for performing electrical / optical conversion of one of the first electric signals divided into two by the first distribution means into a first optical signal; and an electric / optical conversion performed by the first converting means. First optical means for irradiating the active region of the first transistor with the first optical signal, and the other first electric signal divided into two by the second distribution means into a second optical signal. A second converting means for performing electric / optical conversion, and the second converting means Second optical means for irradiating the second optical signal, which has been subjected to the electro-optical conversion by the second optical signal, to the active region of the second transistor, and a second input having a second frequency different from the first frequency. Are divided into two so as to be in phase with each other, one of the divided electric signals is outputted to the first electrode of the first transistor, and the other divided electric signal is outputted to the second electrode. A second distribution means for outputting to the third electrode of the transistor, the first transistor optically / electrically converts the irradiated first optical signal into a third electric signal, The third electric signal is mixed with the electric signal input from the second distribution means to the first electrode by using the non-linear characteristic to output a first mixed signal, and the second transistor Converts the irradiated second optical signal to a fourth signal. Optical-to-electrical conversion into a gas signal, and mixing the fourth electric signal with the electric signal input to the third electrode from the second distribution means using the non-linear characteristic to form a second mixing And outputting an electric signal having a sum of the first frequency and the second frequency, and combining the first and second mixed signals to output an electric signal having the sum of the first frequency and the second frequency. An optical microwave frequency conversion circuit, comprising: a hybrid circuit that outputs an electric signal having a frequency that is a difference between the frequency and the second frequency. 3. A first transistor having a first electrode and a second electrode and having non-linear characteristics, and a third transistor having a third electrode and a fourth electrode and substantially non-linear characteristics of the first transistor. A second transistor having a non-linear characteristic which is substantially the same, a first distribution means for dividing an input first electric signal having a first frequency into two phases in opposite phases to each other, and the first distribution means Conversion means for converting one of the first electric signals, which has been divided into two, into a first optical signal, and a first optical signal which has been subjected to the electrical / optical conversion by the first conversion means. A first optical means for irradiating an active area of the first transistor; and a second optical-to-optical conversion means for converting the other first electric signal divided into two by the second distribution means into a second optical signal. And electrical / optical conversion by the second converting means. A second optical unit for irradiating the active region of the second transistor with the second optical signal, and a second electric signal having a second frequency different from the first frequency and being input to each other. The two electric signals are distributed at a predetermined first phase difference, one of the electric signals after the distribution is output to the first electrode of the first transistor, and the other electric signal after the distribution is transmitted to the second transistor. A second distribution means for outputting to the third electrode, the first transistor optically / electrically converts the irradiated first optical signal into a third electric signal, And the electric signal input to the first electrode from the second distribution means by using the non-linear characteristic to output a first mixed signal, and the second transistor comprises: The illuminated second optical signal is converted into a fourth electrical signal by optical / electrical In other words, the fourth electric signal is mixed with the electric signal input from the second distribution means to the third electrode using the non-linear characteristic to output a second mixed signal, , The first and second mixed signals are connected to each other by a predetermined second
To cancel the second electric signal,
An optical / microwave mixing circuit, comprising: synthesizing means for outputting an electric signal having each frequency of a sum and a difference between the first frequency and the second frequency. 4. The first phase difference is π, and the second phase difference is π.
4. The optical microwave mixing circuit according to claim 3, wherein the phase difference is zero. 5. The method according to claim 1, wherein the first phase difference is 0, and the second phase difference is
4. The optical microwave mixing circuit according to claim 3, wherein the phase difference is π. 6. An optical microwave mixing circuit according to claim 3, 4 or 5, further comprising an electric wave having a sum and a difference between the first frequency and the second frequency output from the synthesizing means. An optical microwave frequency conversion circuit, comprising: a filtering unit that filters an electric signal having the sum frequency or an electric signal having the difference frequency from the signal.