JP6529177B2 - Signal generator and method of operating the same - Google Patents

Description

  The present invention relates to a technology capable of outputting signals in the microwave band to the millimeter wave band and signals in the millimeter wave band to the terahertz wave band using one signal generation device.

  In recent years, with the aging of the population, dealing with adult diseases is becoming a major issue. A non-invasive component concentration measuring device that does not collect blood attracts attention because it requires a large amount of blood to be collected when testing blood sugar levels and the like.

  Dielectric spectroscopy has been proposed as a noninvasive component concentration measuring device. Dielectric spectroscopy irradiates the inside of the skin with an electromagnetic wave, absorbs the electromagnetic wave according to the interaction of the blood component to be measured, such as blood cells and proteins, blood sugar, or blood component and water, and observes the amplitude and phase of the electromagnetic wave Do. However, in the method using infrared light as the electromagnetic wave to be irradiated, the influence of scattering in a living body is large, and it has not been put to practical use.

Electromagnetic waves in the microwave band to the terahertz band have a longer wavelength than infrared light, and are less susceptible to scattering in the living body. In addition, a unique absorption peak corresponding to the molecular weight of the blood component is present in each band. For example, blood cells have absorption peaks in the 100 kHz band, proteins in the 1-10 MHz band, lipids in the 100 MHz band, amino acids in the 1 GHz band, and water in the 20 GHz band (Non-patent Document 1). The response characteristic of this absorption peak to electromagnetic waves can be represented by a complex dielectric constant ε ^* , and in the case of a single-component aqueous solution, it can be represented as follows using a linear combination of Debye relaxation model and conductivity loss.

ここでε_∞は静的誘電率、σは水溶液の導電率、ε₀は真空の誘電率、Δε、τはそれぞれ誘電緩和強度及び誘電緩和時間を表し、Δε及びτの添え字s、h、slow、fastはそれぞれ溶質、水和水、水素結合性のバルク水、非水素結合性のバルク水を意味する(非特許文献2)。このスペクトルの周波数帯域は例えばアルブミン、リゾチウムなどが溶質である蛋白質水溶液の場合、1MHzから1THz程度となっており、マイクロ波帯〜THz波帯までの広帯域な高周波信号を用いて誘電分光を行い、取得したスペクトルの解析を行うことにより物質の識別や成分濃度の測定を行う。

Here epsilon _∞ static dielectric constant, sigma is the conductivity of the aqueous solution, epsilon ₀ is the vacuum dielectric constant, [Delta] [epsilon], tau represents the respective dielectric relaxation strength and dielectric relaxation time, subscript s of [Delta] [epsilon] and tau, h, Slow and fast mean a solute, hydration water, hydrogen bonding bulk water and non-hydrogen bonding bulk water, respectively (Non-patent Document 2). The frequency band of this spectrum is, for example, about 1 MHz to 1 THz in the case of a protein aqueous solution in which albumin, lysium and the like are solutes, and dielectric spectroscopy is performed using a wide band high frequency signal from microwave band to THz wave band, Substances are identified and component concentrations are measured by analyzing the acquired spectrum.

  FIG. 7 is a block diagram of a high frequency signal generation method in the conventional method.

  As shown in FIG. 7A, as a conventional method of generating a wide band high frequency signal, there is a method using a synthesizer in the several MHz band to several tens GHz band. The synthesizer generates a wide band signal by combining a voltage controlled oscillator (VCO) composed of a transistor, a diode, a variable capacitance capacitor and the like with a multiplier, or a frequency divider and a mixer (Non-Patent Document 3).

  On the other hand, as shown in FIG. 7B, there is a method using photomixing as a method of generating a wide band high frequency signal of several tens of GHz band to several THz band (Patent Document 1). The present apparatus is configured of a first continuous wave light source, a second continuous wave light source, an optical coupler, and a photo mixer.

Unexamined-Japanese-Patent No. 2010-062619

Yuri Feldman, Irina Ermolina and Yoshihito Hayashi, "Time Domain Dielectric Spectroscopy Study of Biological Systems", IEEE Transactions on Dielectrics and Electrical Insulation, Vol. 10, No. 5, pp. 728-753, 2003 C. Cametti, S. Marchetti, CM C Gambi and G Onori, “Dielectric Relaxation Spectroscopy of Lysozyme Aqueous Solutions: Analysis of the δ-Dispersion and the Contribution of the Hydration Water”, The Journal of Physical Chemistry B, 115, pp. 7144-7153 Tai-You Lu, Wei-Zen Chen, “A 3-to-10 GHz 14-band CMOS Frequency Synthesizer with Spurs Reduction for MB-OFDM UWB System”, proceedings of IEEE International Solid-State Circuits Conference 2008

  However, when trying to generate a signal of several hundred GHz to several THz band using a synthesizer, the cutoff frequency of the transistor limits the frequency of the fundamental wave, making it difficult to generate a high frequency. Also, when trying to generate a signal in the MHz band using photomixing, although the low frequency operation of the photomixer itself is possible, the frequency of the beat signal is due to the line widths and wavelength stability of the two types of continuous wave light sources. Limited and difficult to generate high quality low frequency. Although broad spectrum spectroscopy is possible by using two types of signal generating devices, there is a problem that each frequency generating device has to be switched mechanically.

  The present invention has been made in view of the above circumstances, and provides a technology capable of outputting a signal of microwave band to millimeter wave band and a signal of millimeter wave band to terahertz wave band using one signal generating device. The purpose is

  In order to solve the above problems, according to a first aspect of the present invention, a first continuous wave light source outputting an optical signal of a predetermined frequency and an optical signal having a frequency different from the frequency of the first continuous wave light source A second continuous wave light source, a light intensity modulator connected to a subsequent stage of the second continuous wave light source, a synthesizer for setting a modulation frequency to the light intensity modulator, and the first continuous wave light source An optical coupler for combining the output and the output of the optical intensity modulator, a photo mixer connected to the subsequent stage of the optical coupler, the first continuous wave light source being turned off, and the second continuous wave light source and the second continuous wave light source The controller is characterized by comprising: a low frequency mode for turning on the synthesizer; and a control unit for switching the high frequency mode for turning on the first continuous wave light source and the second continuous wave light source and turning off the synthesizer.

  A second aspect of the present invention is a method of operating a signal generation device, wherein the signal generation device comprises: a first continuous wave light source outputting an optical signal of a predetermined frequency; a frequency of the first continuous wave light source; A second continuous wave light source outputting an optical signal of a different frequency, an optical intensity modulator connected to a subsequent stage of the second continuous wave light source, and a synthesizer setting a modulation frequency to the optical intensity modulator; The optical coupler includes an optical coupler for multiplexing the output of the first continuous wave light source and the output of the light intensity modulator, and a photo mixer connected to the subsequent stage of the optical coupler, and the operation method is the first continuous Low frequency mode to turn off the wave light source and turn on the second continuous wave light source and the synthesizer, and high frequency mode to turn on the first continuous wave light source and the second continuous wave light source and turn off the synthesizer Feature to switch To.

  According to the present invention, it is possible to output signals in the microwave band to the millimeter wave band and signals in the millimeter wave band to the terahertz wave band using only the signal generation device.

It is a block diagram of a signal generation device concerning a 1st embodiment. It is a figure which shows the operation | movement in the case of producing | generating the signal of a millimeter wave-terahertz wave band in low frequency mode. It is a figure which shows the operation example in the case of producing | generating the signal of a microwave-a millimeter wave band in high frequency mode. It is a block diagram of a signal generation device concerning a 2nd embodiment. It is a block diagram of the signal generation apparatus which concerns on 3rd Embodiment. It is a block diagram of the signal generation apparatus which concerns on 4th Embodiment. It is a block diagram of the production | generation method of the high frequency signal in the conventional method.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

First Embodiment
FIG. 1 is a block diagram of a signal generation apparatus according to the first embodiment.

  The signal generation device includes a first continuous wave light source 1 outputting an optical signal of a predetermined frequency f1, and a second continuous wave light source 2 outputting an optical signal of a frequency f2 different from the frequency of the continuous wave light source 1; The light intensity modulator 3 connected to the subsequent stage of the continuous wave light source 2, the synthesizer 4 for setting the modulation frequency fm to the light intensity modulator 3, the output of the continuous wave light source 1 and the output of the light intensity modulator 3 are combined Optical coupler 5, a photo mixer 6 connected to the subsequent stage of the optical coupler 5, a low frequency mode for turning off the continuous wave light source 1 and turning on the continuous wave light source 2 and the synthesizer 4, the continuous wave light source 1 and the continuous wave The control unit 7 switches the high frequency mode for turning on the light source 2 and turning off the synthesizer 4.

  In the low frequency mode, an optical signal of microwave to millimeter wave band is output from the photo mixer 6, and in the high frequency mode, an optical signal of millimeter wave to terahertz wave band is output from the photo mixer 6.

  The frequency (at least one of f1 and f2) of at least one of the continuous wave light source 1 and the continuous wave light source 2 is variable, and the modulation frequency fm of the synthesizer 4 is variable.

The control unit 7 inputs the set frequency fi as the output frequency of the photo mixer 6, and when the set frequency fi is less than a predetermined frequency f _TH, the control frequency is set to the low frequency mode and the modulation frequency fm matches the set frequency fi Control the synthesizer 4 so that the setting frequency fi is equal to or higher than the frequency f _TH , set the high frequency mode and set the difference | f1−f2 | between the frequency f1 of the continuous wave light source 1 and the frequency f2 of the continuous wave light source 2 Match the frequency fi.

The frequency f _TH is, for example, the upper limit frequency of the light intensity modulator 3 or the synthesizer 4 or the like. For example, frequencies below the frequency f _TH belong to the microwave to millimeter wave bands, and frequencies above the frequency f _TH belong to the millimeter wave to the terahertz wave band, for example.

  The set frequency fi is input to the control unit 7 as digital data, for example. Alternatively, the set frequency fi is input to the control unit 7 as an analog value (for example, a voltage that can be converted to the set frequency fi).

  For the light intensity modulator 3, an electro-optical crystal such as lithium niobate (LN) is used.

  FIG. 2 is a diagram showing an operation in the case of generating a millimeter wave to terahertz wave band signal in the low frequency mode.

When the set frequency fi is less than the frequency f _TH , the control unit 7 turns off the continuous wave light source 1 and turns on the continuous wave light source 2 and the synthesizer 4 so that the modulation frequency fm matches the set frequency fi. Control the synthesizer 4 The control unit 7 applies, for example, a sine wave signal of the modulation frequency fm to the synthesizer 4.

Since the continuous wave light source 1 is turned off, the output of the continuous wave of the frequency f1 is turned off. When the intensity of the optical signal output from the continuous wave light source 2, I _0, the intensity of the output of the optical intensity modulator 3 becomes I ₀ × T (V). T (V) is referred to as the transmittance of the intensity-modulated light signal. The transmittance is expressed as follows when the light intensity modulator 3 is a Mach-Zehnder interference type intensity modulator.

ここでVは電気光学結晶に印可される電圧、φ₀は強度変調器内の光路長差に関する係数、V_πは位相差πの遅延を得るのに必要な印可電圧である。T(V)＝0.5となる線形な領域を動作点とすることで変調周波数ｆｍでの強度変調が可能である。強度変調された光信号は光カプラ５を通過しフォトミキサ６へと入力される。

Here, V is a voltage applied to the electro-optic crystal, φ ₀ is a coefficient related to the optical path length difference in the intensity modulator, and V _π is an applied voltage required to obtain a delay of the phase difference π. By using a linear region where T (V) = 0.5 as the operating point, intensity modulation at the modulation frequency fm is possible. The intensity-modulated optical signal passes through the optical coupler 5 and is input to the photo mixer 6.

  The photo mixer 6 can use a photo detector, such as a photo diode or a uni-traveling carrier photo diode (UTC-PD). A photoconductive band or a non-linear optical crystal can be used instead of the light detector.

  The light signal input to the photo mixer 6 is subjected to envelope detection, and the photo mixer 6 outputs a signal of a frequency that matches the modulation frequency fm, that is, a light signal of microwave to millimeter wave band. The side waves output from the light intensity modulator 3 may be output.

  Optical signals can be transmitted through transmission lines, such as coplanar waveguides (CPWs), coplanar lines (Coplanar strips: CPS), microstrip lines (Microstrip lines: MSL) or broadband antennas, through the line or space. To propagate.

  The line width of a general continuous wave light source is about 200 kHz to 500 kHz. For example, when a high frequency signal is generated using a continuous wave light source having a line width of 200 kHz as the continuous wave light sources 1 and 2, the offset is 200 kHz. It is considered to have -3 dBc phase noise. In addition, the wavelength stability of the continuous wave light source is about 1 to 10 pm. For example, when a high frequency signal is generated using a 5 pm light source as the continuous wave light sources 1 and 2, a shift of ± 1.25 GHz occurs. In fact, the above phase noise may occur.

  On the other hand, the phase noise at the offset of 100 kHz of the synthesizer (4) is -100 dBc or less, which is much smaller than the phase noise input from the continuous wave light source (1, 2). Therefore, when producing high frequency signals using intensity modulation, the phase noise derived from one continuous wave light source is dominant, and the frequency stability in the MHz-GHz band is also high, so two continuous wave lights are used More than twice reduction of phase noise can be expected.

  At this time, it is possible to reduce the influence of the crosstalk of the optical coupler by using a single wavelength light source as the continuous wave light source 1 and using an optical filter in the latter stage.

  FIG. 3 is a diagram showing an operation example in the case of generating a microwave to millimeter wave band signal in the high frequency mode.

When the set frequency fi is equal to or higher than the frequency f _TH , the control unit 7 turns on the continuous wave light source 1 and the continuous wave light source 2 and turns off the synthesizer 4, and further the frequency f 1 of the continuous wave light source 1 and the frequency of the continuous wave light source 2 The difference | f1-f2 | of the frequency f2 is made to coincide with the set frequency fi. If the difference | f1-f2 | does not match the set frequency fi, the controller 7 changes one of the variable frequencies or, if both are variable, changes one or both of the differences. Is set to match the set frequency fi.

  Since the synthesizer 4 is turned off, the signal output of the modulation frequency fm is turned off, and the light intensity modulation by the light intensity modulator 3 is also turned off. On the other hand, the continuous wave light sources 1 and 2 output optical signals of frequencies f1 and f2, respectively. The optical signal of frequency f 2 passes through the light intensity modulator 3. The optical coupler 5 combines these optical signals. The photomixer 6 outputs an optical signal of a frequency that matches the difference | f1-f2 | of the frequencies f1 and f2 included in the combined optical signal, that is, an optical signal of millimeter wave to terahertz wave band.

  An optical signal propagates in a line or space by connecting to a transmission line, for example, a coplanar waveguide, a coplanar line, a microstrip line, or a wide band antenna.

  For example, if the setting frequency fi is changed little by little from the frequency of the microwave band to the frequency of the terahertz band or vice versa, the output frequency of the photo mixer 6 is slightly changed from the frequency of the microwave band to the frequency of the terahertz band or vice versa Change one by one. That is, frequency sweep can be performed.

  The output frequency of the photo mixer 6 in the low frequency mode may be constant, and when the low frequency mode is instructed to the control unit 7, the control unit 7 turns off the continuous wave light source 1 and the continuous wave light source 2. The synthesizer 4 may be turned on to match the modulation frequency fm to the constant output frequency. In this case, the input of the set frequency fi to the control unit 7 is unnecessary.

  When the output frequency of the photo mixer 6 in the high frequency mode may be constant, and the frequency difference | f1-f2 | matches the constant output frequency, and the high frequency mode is instructed to the control unit 7, The control unit 7 may turn on the continuous wave light source 1 and the continuous wave light source 2 and turn off the synthesizer 4. In this case, it is not necessary to make the frequency (at least one of f1 and f2) of at least one of the continuous wave light source 1 and the continuous wave light source 2 variable. Further, the input of the set frequency fi to the control unit 7 is also unnecessary.

Second Embodiment
FIG. 4 is a block diagram of a signal generation apparatus according to the second embodiment. The differences from the signal generation device according to the first embodiment are as follows.

  That is, the signal generation device includes an optical comb signal source 8 which outputs optical signals of a plurality of different frequencies, an optical filter which is a continuous wave light source 1 and a continuous wave light source 2 which branches the plurality of optical signals. And an optical coupler 9 for input to the optical filter. In the high frequency mode, the optical filter that is the continuous wave light source 1 passes only one of the plurality of optical signals (the optical signal of f1) under the control of the control unit 7. In the low frequency mode and the high frequency mode, the optical filter serving as the continuous wave light source 2 passes only another one of the plurality of optical signals (the optical signal of f2) under the control of the control unit 7.

  According to the second embodiment, optical signals of f1 and f2 can be generated by the optical comb signal source, the optical coupler, and the optical filter.

Third Embodiment
FIG. 5 is a block diagram of a signal generation apparatus according to the third embodiment. The differences from the signal generation device according to the first embodiment are as follows.

  That is, the signal generation device includes the optical amplifiers 11 and 12 at the subsequent stage of the continuous wave light sources 1 and 2. The optical amplifiers 11 and 12 amplify the intensities of the optical signals f1 and f2 in the high frequency mode, respectively.

  According to the third embodiment, by providing the optical amplifiers 11 and 12, the intensities of the optical signals f1 and f2 can be increased, and thus the intensity of the optical signal output from the photo mixer 6 can be increased.

  The optical amplifiers 11 and 12 may be provided in the signal generation apparatus of the second embodiment.

Fourth Embodiment
FIG. 6 is a block diagram of a signal generation apparatus according to the fourth embodiment. The differences from the signal generation device according to the first embodiment are as follows.

  That is, the signal generation apparatus includes the optical phase modulator 13 at the subsequent stage of the light intensity modulator 3, and the control unit 7 supplies the phase control signal S to the optical phase modulator 13 in the low frequency mode. Thus, the optical phase modulator 13 outputs a wide band frequency modulation signal. The signal passes through the optical coupler 5 and the photo mixer 6 and is output.

  According to the fourth embodiment, the optical phase modulator 13 is provided at the subsequent stage of the optical intensity modulator 3, and the control unit 7 supplies the control signal S of the phase to the optical phase modulator 13 to obtain a wide band frequency. A modulated signal can be output.

  The optical phase modulator 13 may be provided in the signal generation device of the second and third embodiments.

  As described above, according to the signal generation apparatus of each embodiment, it is possible to output signals in the microwave band to the millimeter wave band and signals in the millimeter wave band to the terahertz wave band using only this signal generation apparatus. Therefore, the device can be miniaturized as compared with the case of using two devices. In addition, it is not necessary to switch between two devices, and it is possible to shorten the measurement time, for example, when the generated signal is used for noninvasive component concentration measurement and the like.

  The signal generation device of the present embodiment can be used, for example, for non-invasive measurement of component concentration of solution present in human or animal, and measurement of component concentration of solution collected from human or animal.

1, 2 Continuous wave light source 3 Optical intensity modulator 4 Synthesizer 5, 9 Optical coupler 6 Photomixer 7 Controller 8 Optical comb signal source 11, 12 Optical amplifier 13 Optical phase modulator

Claims (7)

A first continuous wave light source that outputs an optical signal of a predetermined frequency;
A second continuous wave light source outputting an optical signal having a frequency different from the frequency of the first continuous wave light source;
A light intensity modulator connected downstream of the second continuous wave light source;
A synthesizer for setting a modulation frequency to the light intensity modulator;
An optical coupler for combining the output of the first continuous wave light source and the output of the light intensity modulator;
A photo mixer connected to the rear stage of the optical coupler;
A low frequency mode for turning off the first continuous wave light source and turning on the second continuous wave light source and the synthesizer, and turning on the first continuous wave light source and the second continuous wave light source and the synthesizer And a control unit for switching a high frequency mode for turning off the signal. The frequency of at least one of the first continuous wave light source and the second continuous wave light source is variable,
The modulation frequency of the synthesizer is variable,
The control unit
A set frequency as an output frequency of the photo mixer is input, and when the set frequency is less than a predetermined frequency, the synthesizer is controlled so that the low frequency mode is set and the modulation frequency matches the set frequency. On the other hand, when the set frequency is equal to or higher than the predetermined frequency, the high frequency mode is set, and the difference between the frequency of the first continuous wave light source and the frequency of the second continuous wave light source is matched The signal generator according to claim 1, characterized in that: An optical comb signal source that outputs optical signals of a plurality of mutually different frequencies,
The optical filter includes: an optical filter that is the first continuous wave light source; and an optical coupler that inputs the optical filter to the second continuous wave light source.
The optical filter that is the first continuous wave light source passes only one of the plurality of optical signals, and the optical filter that is the second continuous wave light source is only another one of the plurality of optical signals. The signal generator according to claim 1 or 2, wherein Wherein a first optical amplifier connected to the subsequent stage of the first continuous wave light source, claims 1, characterized in that it comprises a second optical amplifier connected to the subsequent stage of the second continuous wave light source 3 The signal generator according to any one of the above. An optical phase modulator is provided after the light intensity modulator,
The signal generation apparatus according to any one of claims 1 to 4, wherein the control unit gives a phase control signal to the optical phase modulator. A method of operating the signal generator,
The signal generation device comprises: a first continuous wave light source outputting an optical signal of a predetermined frequency; and a second continuous wave light source outputting an optical signal having a frequency different from the frequency of the first continuous wave light source; A light intensity modulator connected to the subsequent stage of the second continuous wave light source, a synthesizer for setting a modulation frequency to the light intensity modulator, an output of the first continuous wave light source, and an output of the light intensity modulator And a photo mixer connected to the subsequent stage of the optical coupler,
The operation method is
A low frequency mode for turning off the first continuous wave light source and turning on the second continuous wave light source and the synthesizer, and turning on the first continuous wave light source and the second continuous wave light source and the synthesizer Switching the high frequency mode to turn off the signal generating apparatus. The frequency of at least one of the first continuous wave light source and the second continuous wave light source is variable,
The modulation frequency of the synthesizer is variable,
A set frequency as an output frequency of the photo mixer is input, and when the set frequency is less than a predetermined frequency, the synthesizer is controlled so that the low frequency mode is set and the modulation frequency matches the set frequency. On the other hand, when the set frequency is equal to or higher than the predetermined frequency, the high frequency mode is set, and the difference between the frequency of the first continuous wave light source and the frequency of the second continuous wave light source matches the set frequency. The method according to claim 6, characterized in that:

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