JP2011064460A - Photoelectric conversion type signal generation device, spectrum analyzer, and reference radio wave generation device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a spectrum analyzer capable of measuring highly accurately a radio wave having a high frequency such as a millimeter wave band. <P>SOLUTION: This spectrum analyzer 401 includes: a frequency converter 21 into which a light fundamental wave whose intensity is modulated by a measuring radio wave which is a measuring object and a prescribed modulated frequency, for outputting a down-convert signal wherein a frequency included in the measuring radio wave is lowered as much as a modulated frequency portion of the light fundamental wave; and a signal intensity measuring device 22 for measuring signal intensity of each frequency included in the down-convert signal outputted from the frequency converter 21. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a photoelectric conversion type signal generator that outputs an optical signal whose intensity is modulated at a predetermined frequency, a spectrum analyzer that measures the signal intensity for each frequency of radio waves, and a reference radio wave generator that outputs radio waves of a predetermined frequency. .

  In order to maintain and improve the radio wave usage environment and promote radio wave use by reducing unnecessary radio waves as much as possible, wireless communication related to the allowable value of spurious emission intensity of radio equipment in WRC (World Radio Communication Conference) Regulation (RR) was revised. According to the revised wireless communication regulations, in order to reduce the emission of unnecessary radio waves in the actual operation state, measurement is performed in the actual operation state, and the outside of the frequency band is separated from the center frequency by ± 250% of the required frequency band. Is defined as a spurious region, and unnecessary emission including out-of-band emission in the spurious region is limited.

  In recent years, transmission systems using 60 GHz and 76 GHz millimeter-wave radio waves have been realized. Also for this transmission system, it is necessary to accurately measure the intensity of spurious emission and confirm that it is within an allowable value defined in the wireless communication rules.

  A spectrum analyzer is used to measure the intensity of spurious emission from the transmission system (see, for example, Patent Document 1). FIG. 6 is a block diagram illustrating the general architecture of a spectrum analyzer. The spectrum analyzer 420 of FIG. 6 includes a filter 61, an oscillator 62, a mixer 63, an intermediate frequency filter 64, and an envelope detector 65. The filter 61 is a pre-selector or a low-pass filter that selects radio waves to be measured. The mixer 63 mixes the reception signal from the filter 61 and the transmission signal from the oscillator 62. The intermediate frequency filter 64 extracts an interference component between the reception signal and the transmission signal from the output of the mixer 63. The envelope detector 65 detects this interference component.

  There are two types of spectrum analyzers 420, a fundamental wave mixing type and a harmonic mixing type. In the fundamental wave mixing type, the oscillator 62 has a local oscillation circuit that operates in a frequency range higher than the frequency range of the received signal, and uses the fundamental frequency from the local oscillation circuit as a transmission signal. On the other hand, in the harmonic mixing type, the oscillator 62 has a harmonic circuit that generates harmonics of the local oscillation circuit, and uses harmonics from the harmonic circuit as a transmission signal.

JP-A-62-211565

  The fundamental wave mixing type spectrum analyzer has an advantage that an external signal is not included in the measurement result, but a local oscillator that generates an accurate frequency is required. For this reason, when the frequency of the radio wave to be measured exceeds 100 GHz, it is difficult to prepare a local oscillator capable of fundamental wave mixing, and there is a problem that it is difficult to measure a high frequency radio wave such as a millimeter wave band.

  On the other hand, the harmonic mixing type spectrum analyzer can lower the oscillation frequency of the local oscillator, but it is difficult to control the harmonic frequency because the noise due to the generation of harmonics and the power due to unnecessary signals affect the measurement results. For this reason, there has been a problem in the measurement accuracy of high-frequency radio waves such as millimeter waves.

  In order to solve the above-described problems, an object of the present invention is to provide a spectrum analyzer that can measure high-frequency radio waves such as millimeter waves with high accuracy.

  In order to achieve the above object, the spectrum analyzer according to the present invention uses an optical beat signal as a fundamental wave. For this reason, the spectrum analyzer according to the present invention includes a photoelectric conversion signal generator that outputs an optical beat signal.

  Specifically, the photoelectric conversion signal generator according to the present invention includes a light source that outputs a supply light having a constant optical frequency, an oscillator that outputs a high-frequency signal, the supply light from the light source, and the oscillator. An optical frequency comb generator for generating a plurality of sideband lights having an optical frequency of the supplied light as zero-order light and a frequency of the high frequency signal as an optical frequency interval; and the optical frequency comb An optical beat signal generator that receives the zero-order light and the sideband light from a generator and outputs an optical beat signal that causes the zero-order light and one of the sideband lights to interfere with each other.

  In the following description, the sideband light and zero-order light generated by the optical frequency comb generator are collectively referred to as “optical frequency comb”. The photoelectric conversion type signal generator according to the present invention generates an optical beat signal from one of the sideband lights and the 0th order light in the optical frequency comb. For this reason, it is possible to easily generate an optical beat signal having a desired frequency by using the interval of the optical frequency comb. Furthermore, since the optical frequency comb interval is highly accurate, the frequency of the optical beat signal can be set with high accuracy. Further, if one of the sideband light that generates the optical beat signal and the light intensity of the 0th-order light are measured, the power of the optical beat signal can be accurately known as described below.

ここで、α_ｒ、α_ｓはそれぞれ参照光、信号光の振幅である。ｆ_ｒ、ｆ_ｓはそれぞれ参照光、信号光の周波数である。φ_ｒ、φ_ｓはそれぞれ参照光、信号光の位相である。干渉は両光の重ね合わせであるので、光ビート信号の電界成分は次のようになる。

The power of the optical beat signal is calculated using the principle of optical heterodyne interference. Assuming that the electric field components of zero-order light (corresponding to reference light) and one of sideband light (corresponding to signal light) are Er and Es, these can be expressed as follows.

Here, α _r and α _s are the amplitudes of the reference light and the signal light, respectively. f _r and f _s are the frequencies of the reference light and the signal light, respectively. φ _r and φ _s are the phases of the reference light and the signal light, respectively. Since interference is a superposition of both lights, the electric field component of the optical beat signal is as follows.

ここで、ｆｂは光ビート周波数、Δは参照光と信号光との位相差である。 Since the light intensity is proportional to the square of the amplitude of the electromagnetic field, the light intensity (power) of the optical beat signal is as follows.

Here, fb is the optical beat frequency, and Δ is the phase difference between the reference light and the signal light.

  The power of the optical beat signal can be calculated by knowing the light intensities of the 0th-order light and the sideband light if the polarization states of the 0th-order light and the sideband light match as shown in Equation 4. The light intensities of the zero-order light and the sideband light can be known with an optical spectrum analyzer or the like. Therefore, if the conversion efficiency of a device that converts an optical beat signal included in a frequency converter (to be described later) into an electrical signal is acquired in advance, the optical beat signal output by the photoelectric conversion signal generator according to the present invention is used as a fundamental wave. As a result, the accurate power of the measurement radio wave to be measured can be obtained from the measurement result of the spectrum analyzer used.

  Accordingly, it is possible to provide a spectrum analyzer that can measure a high-frequency radio wave such as a millimeter wave band with high accuracy by using the optical beat signal output from the photoelectric conversion signal generator according to the present invention as a fundamental wave. it can.

  The photoelectric conversion type signal generator according to the present invention further includes a first polarization maintaining fiber that connects the optical frequency comb generator and the optical beat signal generator while maintaining the polarization of light. It is desirable to provide. Since the polarization states of the zero-order light and the sideband light can be matched, the power of the optical beat signal can be accurately known.

  The optical beat signal generator of the photoelectric conversion type signal generator according to the present invention comprises: an optical frequency separation module that separates the zero-order light and the sideband light from the optical frequency comb generator for each optical frequency; And an optical frequency coupling module that selects one of the sideband lights separated by the optical frequency separation module and causes interference with the zero-order light separated by the optical frequency separation module. For example, an optical beat signal can be generated by the optical frequency separation module and the optical frequency coupling module.

  The optical beat signal generator of the photoelectric conversion type signal generator according to the present invention is configured to connect the optical frequency separation module and the optical frequency coupling module to each other while maintaining the polarization of light. It further has a wave holding fiber. Since the polarization states of the zero-order light and the sideband light can be matched, the power of the optical beat signal can be accurately known.

  The oscillator of the photoelectric conversion type signal generator according to the present invention adjusts the power of the high-frequency signal so that the light intensity of the sideband light that causes the optical beat signal generator to interfere with the zero-order light is maximized. It is characterized by doing. The light intensity of each sideband light can be adjusted by adjusting the power (modulation index) of the high-frequency signal from the oscillator. For this reason, since the amplitude of the optical beat signal is increased, the SN ratio of the beat frequency can be increased as described in the following visibility.

ここで、光ビート信号の光強度の最大値Ｉ_ｍａｘと最小値Ｉ_ｍｉｎは、
Ｉ_ｍａｘ＝α_ｒ ^２＋α_ｓ ^２＋２α_ｓα_ｒ
Ｉ_ｍｉｎ＝α_ｒ ^２＋α_ｓ ^２−２α_ｓα_ｒ
であるから、光ビート信号のビジビリティＶ_ｂｅａｔは、次式で定義される。

ここで、偏波が一致していた場合、サイドバンド光の光強度を大きくすることでビジビリティＶ_ｂｅａｔは、１に近づき、ビート周波数のＳＮ比は高くなる。 FIG. 5 shows the waveform of the optical beat signal. Visibility V is defined by the following equation.

Here, the maximum value I _max and the minimum value I _min of the light intensity of the optical beat signal are
I _max = α _r ² + α _s ² + 2α _s α _r
I _min = α _r ² + α _s ² -2α _s α _r
Therefore, the visibility V _beat of the optical beat signal is defined by the following equation.

Here, when the polarizations coincide with each other, the visibility V _beat approaches 1 by increasing the light intensity of the sideband light, and the SN ratio of the beat frequency increases.

  The spectrum analyzer according to the present invention receives a measurement radio wave to be measured and an optical fundamental wave intensity-modulated at a predetermined modulation frequency, and reduces the frequency included in the measurement radio wave by the modulation frequency of the optical fundamental wave. A frequency converter that outputs a down-converted signal; and a signal strength measuring device that measures the signal strength of each frequency included in the down-converted signal output from the frequency converter.

  The spectrum analyzer according to the present invention down-converts a measurement radio wave using an optical signal as a fundamental wave. Since light is used, it is possible to obtain a fundamental wave with an easy frequency that is easy to modulate. For this reason, this invention can provide the spectrum analyzer which can measure the high frequency electromagnetic wave like a millimeter wave band with high precision. Furthermore, since light is used, it is possible to use an optical fiber until the fundamental wave is coupled to the frequency converter. Since the waveguide is not used, the degree of freedom of arrangement in the spectrum analyzer can be improved.

  The spectrum analyzer according to the present invention further includes the photoelectric conversion signal generator, and the photoelectric conversion signal generator uses the optical beat signal output from the optical beat signal generator as the optical fundamental wave. It inputs to a frequency converter, It is characterized by the above-mentioned. The frequency setting accuracy of the optical beat signal is high, and the power of the optical beat signal can be accurately known. For this reason, this invention can provide the spectrum analyzer which can measure the high frequency electromagnetic wave like a millimeter wave band with high precision.

  The reference radio wave generator according to the present invention receives an oscillator that outputs an electrical signal having a desired frequency, an optical fundamental wave that is intensity-modulated with a constant modulation frequency and the electrical signal from the oscillator, and A frequency converter that outputs radio waves of two frequencies obtained by converting a frequency by the modulation frequency of the optical fundamental wave; and a waveguide filter that transmits radio waves on a high frequency side among the radio waves output by the frequency converter; .

  The reference radio wave generator according to the present invention up-converts the frequency of the generated electrical signal using an optical signal, and outputs it as a radio wave. Since light is used, it is possible to obtain a fundamental wave with an easy frequency that is easy to modulate. For this reason, this invention can provide the reference | standard radio wave generator which can output a high frequency electric wave like a millimeter wave band with high precision. The spectrum analyzer can be accurately calibrated by using the radio wave from the standard radio wave generator according to the present invention as a calibration reference signal for the spectrum analyzer. Therefore, the reference radio wave generator according to the present invention can calibrate the spectrum analyzer so that high frequency radio waves such as millimeter waves can be measured with high accuracy.

  The reference radio wave generator according to the present invention further includes the photoelectric conversion signal generator, and the photoelectric conversion signal generator converts the optical beat signal output from the optical beat signal generator into the optical fundamental wave. Is input to the frequency converter. The frequency setting accuracy of the optical beat signal is high, and the power of the optical beat signal can be accurately known. For this reason, this invention can provide the reference | standard radio wave generator which can output a high frequency electric wave like a millimeter wave band with high precision.

  The present invention can provide a spectrum analyzer that can measure high-frequency radio waves such as millimeter waves with high accuracy.

It is a block diagram explaining the photoelectric conversion type signal generator concerning the present invention. It is a graph showing the maximum output power of each order obtained when input light having an intensity of 10 dBm is input to the optical frequency comb generator and the modulation index at that time. It is a block diagram explaining the spectrum analyzer which concerns on this invention. It is a block diagram explaining the reference | standard radio wave generator which concerns on this invention. It is a figure for demonstrating visibility. It is a block diagram explaining the conventional spectrum analyzer.

  Embodiments of the present invention will be described with reference to the accompanying drawings. The embodiments described below are examples of the present invention, and the present invention is not limited to the following embodiments. In the present specification and drawings, the same reference numerals denote the same components.

(Photoelectric conversion signal generator)
FIG. 1 is a block diagram illustrating a photoelectric conversion signal generator 301 according to an embodiment of the present invention. The photoelectric conversion signal generator 301 is supplied with a light source 11 that outputs a supply light having a constant optical frequency, an oscillator 12 that outputs a high-frequency signal, a supply light from the light source 11 and a high-frequency signal from the oscillator 12. An optical frequency comb generator 13 for generating a plurality of sideband lights with the optical frequency of the supplied light as the zeroth order light and the frequency of the high frequency signal as the optical frequency interval, and the zeroth order light and the sideband from the optical frequency comb generator 13 And an optical beat signal generator 14 for outputting an optical beat signal in which light is input and the zero-order light and one of the sideband lights interfere with each other.

  The light source 11 outputs supply light. The light source 11 keeps the frequency of the supplied light stable. For example, the light source 11 is a laser. The oscillator 12 outputs a high-frequency signal that is a high-frequency electrical signal. For example, the oscillator 12 is an RF synthesizer that outputs a high-frequency signal of 25 GHz.

The optical frequency comb generator 13 receives the supply light from the light source 11 and the high frequency signal from the oscillator 12. The optical frequency comb generator 13 generates a plurality of sideband lights (optical frequency combs) around the optical frequency ν ₀ of the supplied light. The optical frequency difference fm between the sideband lights is equal to the frequency of the high frequency signal of the oscillator 12. For example, when the high-frequency signal is 25 GHz, the optical frequency difference fm is 25 GHz.

In general, in the optical frequency comb, the light intensity of the center 0th-order light having the light frequency ν ₀ is the highest, and the light intensity decreases as the sideband light is separated from the 0th-order light. Here, a plot from the light intensity of the 0th-order light to the light intensity of the high-order sideband light is referred to as a light intensity profile.

  The light intensity profile can be adjusted by the intensity (modulation index) of the high-frequency signal from the oscillator 12. FIG. 2 is a graph showing the maximum output power of each order obtained when input light having an intensity of 10 dBm is input to the optical frequency comb generator 13 and the modulation index at that time. For example, it can be seen that the maximum output power of −30 dBm can be obtained when the light intensity of the 10th-order sideband light is set to a modulation index of 0.3π. The light intensity of the 10th-order sideband light can be adjusted by adjusting the modulation index.

  The optical beat signal generator 14 receives the optical frequency comb from the optical frequency comb generator 13. For example, the first polarization maintaining fiber 15 connects between the optical frequency comb generator 13 and the optical beat signal generator 14. Since the first polarization maintaining fiber 15 propagates light while maintaining polarization, the visibility of the optical beat signal can be increased. The first polarization maintaining fiber 15 is, for example, a PANDA (Polarization-maintaining AND Absorption-reducing) fiber.

  The optical beat signal generator 14 generates an optical beat signal by interfering light of two optical frequencies of the optical frequency comb. The frequency of the optical beat signal (optical beat frequency) corresponds to the optical frequency difference between the two light frequencies that cause interference. The optical beat signal generator 14 desirably uses one of the two light frequencies as zero-order light. This is due to the following reason.

  In the conventional case where two electrical signals having different frequencies interfere with each other, the amplitude of the beat signal is the amplitude of a higher-order signal of the carrier frequency, so the SN ratio of the spectrum analyzer is greatly increased in the conversion efficiency of the frequency converter. It was affected.

  However, when two lights having different optical frequencies are caused to interfere, if the light intensity of one light is strong, the optical beat signal can obtain a constant amplitude even if the light intensity of the other light is weak. Here, the optical frequency comb usually has the strongest light intensity of the 0th order light. For this reason, if the zero-order light of the optical frequency comb is one of the lights, the amplitude of the optical beat signal obtained by interference is large, and the SN ratio of the spectrum analyzer can be increased.

  For example, the optical beat signal generator 14 includes an optical frequency separation module 16 that separates zero-order light and sideband light from the optical frequency comb generator 13 for each optical frequency, and sideband light separated by the optical frequency separation module 16. And an optical frequency coupling module 17 for interfering with zero-order light separated by the optical frequency separation module 16.

  The optical frequency separation module 16 is, for example, an AWG (Arrayed Waveguide Grating). The optical frequency comb input from the optical frequency comb generator 13 is output for each frequency. The optical frequency coupling module 17 is, for example, a wavelength selectable switch. Of the lights for each optical frequency combined from the optical frequency separation module 16, the 0th-order light and the desired sideband light are combined and interfered to output an optical beat signal. The optical frequency separation module 16 and the optical frequency coupling module 17 are connected by the second polarization maintaining fiber 18. Since the second polarization maintaining fiber 18 propagates light while maintaining polarization, the visibility of the optical beat signal can be increased. The second polarization maintaining fiber 18 is, for example, a PANDA fiber.

  In order to bring the visibility of the optical beat signal close to 1 and increase the SN ratio of the optical beat frequency, the oscillator 12 causes the optical intensity of the sideband light that interferes with the zero-order light by the optical beat signal generator 14 to be maximized. Adjust the power (modulation index) of the high-frequency signal.

(Spectrum analyzer)
FIG. 3 is a block diagram for explaining the spectrum analyzer 401 of the present embodiment. The spectrum analyzer 401 receives a measurement radio wave to be measured and an optical fundamental wave intensity-modulated at a predetermined modulation frequency, and outputs a down-converted signal obtained by reducing the frequency included in the measurement radio wave by the modulation frequency of the optical fundamental wave. A frequency converter 21 and a signal strength measuring device 22 that measures the signal strength of each frequency included in the down-converted signal output from the frequency converter 21 are provided.

  The frequency converter 21 receives measurement radio waves and optical fundamental waves. The measurement radio wave is coupled to the waveguide filter 23 from the outside of the spectrum analyzer 401 and input to the frequency converter 21. The waveguide filter 23 is, for example, a waveguide. The waveguide has a function of a high-pass filter and blocks radio waves below the frequency to be measured.

  The optical fundamental wave is coupled to the frequency converter 21 by an optical fiber. The optical fundamental wave is light whose intensity is modulated at a predetermined modulation frequency. For example, the spectrum analyzer 401 further includes the photoelectric conversion type signal generator 301 described with reference to FIG. 1, and the optical beat signal output from the photoelectric conversion type signal generator 301 is used as an optical fundamental wave to the frequency converter 21. You may enter.

  The frequency converter 21 lowers a plurality of frequencies included in the measurement radio wave by a certain amount (down-conversion amount) at a time. The amount of down conversion corresponds to the modulation frequency of the optical fundamental wave. When the photoelectric conversion signal generator 301 is provided, the down-conversion amount corresponds to the optical beat frequency of the optical beat signal. For example, if the optical beat frequency is 250 GHz, the frequency converter 21 down-converts the measurement radio wave near 300 GHz to a signal near 50 GHz.

  The frequency converter 21 is, for example, a waveguide type photomixer equipped with UTC-PD (Uni-Travelling-Carrier-Photo Diode).

  The low noise amplifier 24 amplifies the down-converted signal output from the frequency converter 21 and couples it to the signal strength measuring device 22 with a coaxial cable. The signal strength measuring device 22 measures the signal strength for each frequency included in the down-converted signal. Here, the signal strength measuring device 22 can obtain the accurate power of the measurement radio wave based on the power of the optical beat signal.

(Reference radio wave generator)
FIG. 4 is a block diagram for explaining the reference radio wave generator 402 of the present embodiment. The reference radio wave generator 402 receives an oscillator 32 that outputs an electric signal having a desired frequency, an optical signal from the oscillator 32, and an optical fundamental wave that has been intensity-modulated at a constant modulation frequency. A frequency converter 31 that outputs radio waves of two frequencies converted by the modulation frequency of the wave, and a waveguide filter 33 that transmits radio waves on the high frequency side of the radio waves output from the frequency converter 31 are provided.

  The frequency converter 31 receives an electrical signal having a predetermined frequency and an optical fundamental wave. The electrical signal is coupled from the oscillator 32 to the frequency converter 31 by a coaxial cable. The optical fundamental wave is coupled to the frequency converter 31 by an optical fiber. The optical fundamental wave is light whose intensity is modulated at a predetermined modulation frequency. For example, the reference radio wave generator 402 further includes the photoelectric conversion signal generator 301 described with reference to FIG. 1, and a frequency converter using the optical beat signal output from the photoelectric conversion signal generator 301 as an optical fundamental wave. 31 may be input.

  The frequency converter 31 raises (up-converts) and lowers (down-converts) the frequency of the electric signal by a certain amount (conversion amount) around the frequency. The conversion amount corresponds to the modulation frequency of the optical fundamental wave. When the photoelectric conversion signal generator 301 is provided, the conversion amount corresponds to the optical beat frequency of the optical beat signal. For example, if the frequency of the electrical signal is 70 GHz and the optical beat frequency is 125 GHz, the frequency converter 31 outputs a down-converted 55 GHz radio wave and an up-converted 195 GHz radio wave.

  The frequency converter 31 is, for example, a waveguide type photomixer equipped with UTC-PD.

  The waveguide filter 33 is, for example, a waveguide. The waveguide has a function of a high-pass filter and blocks radio waves below the frequency to be measured. For example, the waveguide filter 33 can block the 55 GHz radio wave out of the 55 GHz and 195 GHz radio waves output from the frequency converter 31 and output only the 195 GHz radio wave as a reference radio wave to the outside.

  The power of the reference radio wave output from the reference radio wave generator 402 is the power of the electrical signal output from the oscillator 32, the power of the optical fundamental wave input to the frequency converter 31, and the conversion efficiency of UTC-PD included in the frequency converter 31. It can be calculated by knowing. Therefore, the reference radio wave generator 402 can be used as a calibration device for the spectrum analyzer 401 described with reference to FIG.

  Specifically, a reference radio wave having a known power is coupled to the waveguide filter 23 of the spectrum analyzer 401, and the signal intensity measuring device 22 or the photoelectric conversion type is used so that the measurement result of the spectrum analyzer 401 becomes the power of the reference radio wave. The spectrum analyzer 401 can be calibrated by adjusting the signal generator 301.

11: light source 12: oscillator 13: optical frequency comb generator 14: optical beat signal generator 15: first polarization maintaining fiber 16: optical frequency separation module 17: optical frequency coupling module 18: second polarization maintaining fiber 21, 31: Frequency converter 22: Signal strength measuring device 23, 33: Waveguide filter 24: Low noise amplifier 32: Oscillator 61: Filter 62: Oscillator 63: Mixer 64: Intermediate frequency filter 65: Envelope detector 301: Photoelectric conversion Type signal generators 401, 420: spectrum analyzer 402: reference radio wave generator

Claims (9)

A light source that outputs a supply light of a constant optical frequency;
An oscillator that outputs a high-frequency signal;
The supply light from the light source and the high-frequency signal from the oscillator are input, and a plurality of sideband lights are generated with the optical frequency of the supply light as zero-order light and the frequency of the high-frequency signal as an optical frequency interval. An optical frequency comb generator;
An optical beat signal generator that receives the zero-order light and the sideband light from the optical frequency comb generator, and outputs an optical beat signal that causes the zero-order light and one of the sideband lights to interfere with each other;
An optoelectric conversion signal generator.   2. The light according to claim 1, further comprising a first polarization maintaining fiber that connects the optical frequency comb generator and the optical beat signal generator while maintaining polarization of light. 3. Electrical conversion signal generator. The optical beat signal generator is
An optical frequency separation module for separating the zero-order light and the sideband light from the optical frequency comb generator for each optical frequency;
An optical frequency coupling module that selects one of the sideband lights separated by the optical frequency separation module and interferes with the zero-order light separated by the optical frequency separation module;
3. The photoelectric conversion type signal generator according to claim 1, further comprising: The optical beat signal generator is
4. The photoelectric conversion according to claim 3, further comprising a second polarization maintaining fiber that connects the optical frequency separation module and the optical frequency coupling module while maintaining a polarization of light. 5. Expression signal generator. The oscillator is
5. The power of the high-frequency signal is adjusted so that the light intensity of the sideband light that causes the optical beat signal generator to interfere with the zero-order light is maximized. 6. The photoelectric conversion type signal generator. Frequency conversion that outputs a measurement radio wave to be measured and an optical fundamental wave intensity-modulated at a predetermined modulation frequency, and outputs a down-converted signal in which the frequency contained in the measurement radio wave is reduced by the modulation frequency of the optical fundamental wave And
A signal strength measuring device for measuring the signal strength of each frequency included in the down-converted signal output by the frequency converter;
A spectrum analyzer comprising: The photoelectric conversion signal generator according to any one of claims 1 to 5, further comprising:
The spectrum analyzer according to claim 6, wherein the photoelectric conversion signal generator inputs the optical beat signal output from the optical beat signal generator to the frequency converter as the optical fundamental wave. An oscillator that outputs an electrical signal of a desired frequency;
The electric signal from the oscillator and an optical fundamental wave intensity-modulated at a constant modulation frequency are input, and radio waves having two frequencies obtained by converting the frequency of the electric signal by the modulation frequency of the optical fundamental wave are output. A frequency converter;
Among the radio waves output by the frequency converter, a waveguide filter that transmits radio waves on the high frequency side,
A reference radio wave generator. The photoelectric conversion signal generator according to any one of claims 1 to 5, further comprising:
9. The reference radio wave generation according to claim 8, wherein the photoelectric conversion signal generator inputs the optical beat signal output from the optical beat signal generator to the frequency converter as the optical fundamental wave. apparatus.

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