1295376 18639twf.doc/g 九、發明說明： 【發明所屬之技術領域】 本發明是有關於-種電磁波的電光取樣技術，且特別 是有關於電光取樣裝置與方法，實質上全部以光纖連接， 且可以在無差頻的條件下，對電磁波信號取樣。 【先前技術】 目前’高頻電路的發展已逐漸朝向電磁波或是毫米波 的頻段。各種電磁波積體電路（m〇n〇lithic micr〇wave integrated circuit，MMIC)的操作速度也不斷提高，已超過 傳統的示波器與網路分析儀等檢測設備的頻寬限制。高頻 檢測設備技術也持續在研發。如何提高量測頻寬，降低系 統成本，疋重要且能產生大量產業利益的研究課題。 在眾多高速電場量測系統中，電光取樣技術是已經被 發展的技術，具有高頻操作特性。由於電光效應的反應時 間小於0·1 ps，其對應的頻率為10 THz，若搭配適當壓縮 的光脈衝以進行取樣，就可以使時間解析度小於丨ps等 級，如此能應用於各種電磁波元件，例如微波/毫米波元件 的電性檢測。 現今的電光取樣系統架構，多採用自由空間（仕ee space)傳播的雷射光路。由於其不可避免的光束對準程 序’會影響里測糸統的效盈。此外，為獲得則足夠窄的雷 射脈衝光源’例如需要使用Ti:Sappire等大型雷射，這造 成量測系統變得龐大，另外也產生脈衝重複率可調範圍過 小的缺點。 1295376 lS639twf.doc/g 圖1繪不傳統的電光取樣系統架構示意圖。參閱圖b 傳統的電光取樣系統包括—鈦··藍寳石#射削，做為取 的短脈衝光源。 7 14裡，傳統對微波取樣的機制如下描述。例如研發者 想對微波元件所發出的微波的振幅變化做量測，於是^要 對振幅’在「些時_上做取樣，而後組合分析出振^變 化。由於微波有一固定的頻率，傳統技術是利用改變雷射 ，取樣脈衝的頻率，以使其財-差頻(offset frequency)。 藉由改變差頻的大小，取樣脈衝相對微波的時間座標，就 可以在-些不同時間點上取樣’例如進行電場振幅的择描 取樣。因此’差頻效應對傳統的取樣機制是關鍵技術之一。 接著繼續參閱圖1 ’由鈦:藍寶石雷射1〇〇發出的光俨 號，經過補償器106，極化分光鏡108，物鏡112，而後^ 焦於一電光晶體 114(dectr〇-optical crystal: E0 crystai)，且 由雷射產生的光信號會被電光晶體114反射。又，微波作 號源104控制微波電路u6，以產生待測的一微波。由^ 電光晶體114會隨微波的強度改變折射率，也因此對應改 變橢圓偏極形狀，因此對應產生強度變化量。此變化量在 返回的路徑上，由極化分光鏡108將其分離出來，藉由感 光二極體(photodiode)將光信號轉換成電性信號。 所謂電光效應是指電光晶體在受到電場的影響時，嗦 晶體的折射率橢圓球發生形變’使得經過該晶“ =位的麦化。電光晶體是指具有電光效應的晶體。將電光 晶體與-些光學元雜合後’可以使得經過該晶體的光在 1295376 18639twf.doc/g 強度上發生變化，而且變化的強度與施加在電光晶體上的 電場成正比。利用這個關係，就能藉由 >[貞測光的強度來债 測出電場的強度，進而得知待測元件的特性。 於此如前述，傳統技術根據差頻的方式來進行量測， 因此舄要有差頻的"is说產生102，配合鎖相(phase-locked) 放大器120，將電性信號分離出來給信號分析單元122做 分析。 對於圖1的架構，首先其光信號全部都是在自由空間 傳播，因此系統需要維持對準。因此，傳統上的改良技術 是部分由光纖取代。圖2繪示傳統的另一電光取樣系統架 構示意圖。參閱圖2，其基本架構與圖工的架構類似，其 間差異疋光搞合器128、極化控制器126、與光纖探頭124。 光耦合态128是將光信號轉成光纖傳輸。極化控制器126 對來回經過的光信號做極化控制，以利極化分光鏡1〇8將 反射來的變化量分離。光纖探頭124則將電光晶體黏貼在 一個漸變折射率透鏡(GRINlens)，另外一端連接於光纖。 如此可以減少一部份的對準要求，但是仍有一部分維持以 自由空間傳播，仍要求對準。 旦光纖探頭124可以彈性應用在各種微波電路與天線結 構量測，特別是波導或封閉空間的電場等。 +然而，對於上述二種傳統的架構都使用差頻的設計， f而要產生約1 Hz差頻的信號合成技術，所需要成本甚 ° 不具有頻率獨立操作（frequency independent 叩⑽她得4紐’目此不献料來自域㈣信號進行 8 1295376 18639twf.doc/g 同步取樣。 換句居说，對於電光取樣的傳統架構仍有其缺點，需 要進一步改進與研發。 【發明内容】 #本發明提供-種光纖式電光取樣裝置與方法，可以實 貝上王。Η吏用光纖來傳送光信號，如此可以有效減少對準 的要求或是進而不需要對準。 本發明提供-種光纖式電光取樣裝置與方法，可以操 =於無差，條件下。除了節省由於差頻造成的成本增加 應用且不又頻率^化的影響，還可以使系統有更多方便的 -本發明提出-種光纖式電光取樣裝置，包括一雷射單 70，產生-光信號。-極化控制輯由光纖接收該光信號， =極該光信號…電磁波信號源用以產生-待測電磁波 Μ。-錢探頭藉由光纖與該極化㈣器祕，且將該 j號反射it職極化控㈣。該光纖铜制該待測電 且依該待測電磁波信號的強度，使該被反射光 應改變的一變化量。一光學單元藉由光纖接收 ^反，以將該變化量分離出來，轉換成一取樣 ^虎。-無差頻相移式鎖相迴路，連接於該雷射單元和該 信f源之間，以控制該光信號對應於該待測電磁波 該相位差的改變，以對待測電磁波 k唬取樣。 依照本發_—實_，於前述光纖式電光取樣裝 1295376 18639twf.doc/g ^在該雷射單元與該極化控_之間，包括色散補償光 • 依照本發日月的-實施例，於前述光纖 置，該極化控制器是一光纖式極化控制器，其例如更^ 包括一 λ/2波片與一 χ/4波片。 ▲依照本發明的一實施例’於前述光纖式電光取樣 置，該無差„移式鎖相迴路包括一除頻器，一鎖相迴二 φ 以及一相移器串接所組成。 依照本發明的-實施例’於前述光纖式電光取 置，其中該無差頻相移式鎖相迴路包括一除頻器，—鎖^ 迴路’以及-相位調制電路，以輸出一控制信號 雷射單元的該光信號的一相位延遲。 =本發明的-實施例，於前述光纖式電光取樣裝 ” 中销差_目移式鎖相迴路包括:―相位 =與《磁波信號源減。—加法電路_在該相位頻 瞻 _制11與-迴關波器之間，且接收外部輸人的一直流 電壓、-鑛齒波信號、或是一鑛齒波相位調制信號。 壓控制振盪器接收迴路濾波器的一輪出，且藉由一除頻哭 與該相位頻率偵測器搞接。又，迴路滤波器輸出一控制^ 號，以調整雷射單元的該光信號相對於該待測電磁波信號 的一相位延遲。 依照本發_-實_，於前述光纖式電光取樣裝 置，其中無差頻相移式鎖相迴路包括一相位頻率偵測器， 與該電磁波信號源搞接。-迴路據波器與該相位頻率^測 1295376 18639twf.doc/g =:=電Γ接在該迴繼器之後，且接收由 、工/7錢人的-鑛齒波相位調制信號。 振逢器，接收該加法電路的—輪m “硫徑制 位頻率偵測器输。其中該迴路濾波器輸出—控制作號， 以调整該雷射單it的該光信號相對於該制電磁波信號的 一相位延遲。1295376 18639twf.doc/g IX. Description of the Invention: [Technical Field] The present invention relates to electro-optical sampling techniques for electromagnetic waves, and in particular to electro-optical sampling devices and methods, substantially all connected by optical fibers, and The electromagnetic wave signal can be sampled without the difference frequency. [Prior Art] At present, the development of high frequency circuits has gradually moved toward the electromagnetic wave or the frequency band of millimeter waves. The operating speeds of various electromagnetic wave integrated circuits (MMICs) are also increasing, which exceeds the bandwidth limitations of conventional oscilloscopes and network analyzers. High-frequency testing equipment technology is also continuing to be developed. How to improve the measurement bandwidth, reduce the system cost, and research topics that are important and can generate a lot of industrial benefits. Among many high-speed electric field measurement systems, electro-optic sampling technology has been developed with high-frequency operation characteristics. Since the response time of the electro-optical effect is less than 0·1 ps, the corresponding frequency is 10 THz. If the light pulse is properly sampled for sampling, the time resolution can be made smaller than the 丨ps level, so that it can be applied to various electromagnetic wave components. For example, electrical detection of microwave/millimeter wave components. Today's electro-optic sampling system architecture uses laser light paths that are transmitted by free space. Because of its inevitable beam alignment procedure, it affects the efficiency of the metric system. Further, in order to obtain a laser pulse source which is sufficiently narrow, for example, a large laser such as Ti:Sappire is required, which causes the measurement system to become bulky, and also has the disadvantage that the pulse repetition rate can be adjusted to an excessively small range. 1295376 lS639twf.doc/g Figure 1 shows a schematic diagram of the architecture of an unconventional electro-optical sampling system. Refer to Figure b. The traditional electro-optic sampling system consists of - Titanium Sapphire # shot, used as a short pulse source. In 7-14, the traditional mechanism for sampling microwaves is described below. For example, the developer wants to measure the amplitude variation of the microwave emitted by the microwave component, so it is necessary to sample the amplitude 'at some time', and then combine and analyze the vibration change. Since the microwave has a fixed frequency, the conventional technology By changing the frequency of the laser and sampling the pulse to make it the offset frequency. By changing the magnitude of the difference frequency, the sampling pulse can be sampled at different time points relative to the time coordinate of the microwave. For example, the selective sampling of the electric field amplitude is performed. Therefore, the 'difference frequency effect is one of the key techniques for the conventional sampling mechanism. Then continue to refer to FIG. 1 'The optical nickname issued by the titanium: sapphire laser 1 经过, through the compensator 106 The polarizing beam splitter 108, the objective lens 112, and then the focus is on an electro-optic crystal 114 (dectr〇-optical crystal: E0 crystai), and the optical signal generated by the laser is reflected by the electro-optic crystal 114. 104 controls the microwave circuit u6 to generate a microwave to be tested. The electro-optic crystal 114 changes the refractive index according to the intensity of the microwave, and accordingly changes the elliptical polarization shape, so that the corresponding strong The amount of change is on the return path, which is separated by the polarization beam splitter 108, and the light signal is converted into an electrical signal by a photodiode. The so-called electro-optic effect means that the electro-optic crystal is subjected to When the electric field is affected, the refractive index ellipsoid of the ytterbium crystal is deformed 'because of the graining of the crystal "= position. An electro-optic crystal refers to a crystal having an electrooptic effect. After the electro-optic crystal is hybridized with some of the optical elements, the light passing through the crystal can be varied in intensity at 1295376 18639 twf.doc/g, and the intensity of the change is proportional to the electric field applied to the electro-optic crystal. By using this relationship, the intensity of the electric field can be measured by >[the intensity of the light measurement, and the characteristics of the device to be tested can be known. As described above, the conventional technique performs measurement according to the difference frequency method, so that the difference frequency "is is generated 102, and the phase-locked amplifier 120 is used to separate the electrical signal to the signal. Analysis unit 122 does the analysis. For the architecture of Figure 1, first all of its optical signals are propagating in free space, so the system needs to maintain alignment. Therefore, the traditionally improved technology is partially replaced by optical fibers. Fig. 2 is a schematic view showing the structure of another conventional electro-optical sampling system. Referring to Figure 2, the basic architecture is similar to the architecture of the pictorial, with the difference between the optical combiner 128, the polarization controller 126, and the fiber optic probe 124. The optically coupled state 128 is the conversion of optical signals into optical fibers. The polarization controller 126 performs polarization control on the optical signals that pass back and forth to separate the amount of change reflected by the polarization beam splitters 1〇8. The fiber optic probe 124 attaches the electro-optic crystal to a graded index lens (GRINlens) and the other end to the fiber. This can reduce part of the alignment requirements, but still maintain a part of the free space to propagate, still requiring alignment. The fiber optic probe 124 can be flexibly applied to various microwave circuit and antenna structure measurements, particularly electric fields in waveguides or enclosed spaces. + However, for the above two traditional architectures, the difference frequency design is used, f is to generate a signal synthesis technique with a difference frequency of about 1 Hz, and the cost is very low. There is no frequency independent operation (frequency independent 叩 (10) she has 4 New Zealand 'There is no information from the domain (four) signal to carry out 8 1295376 18639twf.doc / g simultaneous sampling. In other words, the traditional architecture for electro-optical sampling still has its shortcomings, and needs further improvement and research and development. Providing a fiber optic electro-optic sampling device and method can be used to transmit an optical signal by using an optical fiber, so that the alignment requirement can be effectively reduced or not required to be aligned. The present invention provides a fiber-optic electro-optic The sampling device and method can be operated under the condition of no difference, in addition to saving the cost increase due to the difference frequency and not affecting the frequency, the system can be more convenient - the invention proposes an optical fiber The electro-optic sampling device comprises a laser unit 70 for generating an optical signal. The polarization control is received by the optical fiber, and the optical signal is used for the electromagnetic signal source. - the electromagnetic wave to be measured. - The money probe is made by the optical fiber and the polarization (4), and the j-number is reflected by the polarization control (4). The fiber is made of copper and is based on the electromagnetic wave signal to be measured. The intensity is such a change that the reflected light should be changed. An optical unit receives the inverse by the optical fiber to separate the change amount and converts it into a sample. - No difference frequency phase shift type phase-locked loop, connected Between the laser unit and the source of the signal f, in order to control the change of the phase difference of the optical signal corresponding to the electromagnetic wave to be measured, the electromagnetic wave to be measured is sampled. According to the present invention, in the optical fiber type Electro-optical sampling device 1295376 18639twf.doc/g ^ between the laser unit and the polarization control _, including dispersion compensation light. According to the embodiment of the present invention, the polarization controller is A fiber-optic polarization controller, for example, further comprising a λ/2 wave plate and a χ/4 wave plate. ▲In accordance with an embodiment of the present invention, the fiber-optic electro-optic sampling device is provided. The phase-locked loop includes a frequency divider, a phase-locked return φ and a phase shifter series According to the embodiment of the present invention, in the optical fiber type electro-optic device, the difference-free phase-shifted phase-locked loop includes a frequency divider, a lock circuit, and a phase modulation circuit for outputting a control. A phase delay of the optical signal of the signal laser unit. The embodiment of the present invention, in the optical fiber type electro-optical sampling device, has a pin-out phase-locked phase-locked loop comprising: - phase = and "magnetic wave source source minus - Addition circuit _ between the phase frequency _ 11 and the return wave, and receive the external input of the DC voltage, - mineral tooth wave signal, or a mine tooth wave phase modulation signal. The oscillator receives one round of the loop filter and is connected to the phase frequency detector by a frequency division cry. Further, the loop filter outputs a control signal to adjust a phase delay of the optical signal of the laser unit with respect to the electromagnetic wave signal to be measured. According to the present invention, in the optical fiber electro-optic sampling device, the difference-frequency phase-shifted phase-locked loop includes a phase frequency detector coupled to the electromagnetic wave signal source. - The loop data and the phase frequency are measured 1295376 18639twf.doc/g =:= Electrically connected after the repeater, and receives the - ore tooth phase modulation signal from the worker/seven. The oscillating device receives the wheel m of the adding circuit and the sulfur path frequency detecting device input, wherein the circuit filter outputs a control number to adjust the optical signal of the laser single it relative to the electromagnetic wave One phase delay of the signal.
依照本發明的一實施例，於前述光纖式電光取樣裝 置’其中該f射單元是-半導體雷射，例如是增益開關半 導體雷射。 本發明又長：出一種光纖式電光取樣方法，以對一待測 電磁波信號取樣。此方法包括提供一雷射單元以產生一光 信號，以及一光纖探頭。又，利用光纖，將該光信號引導 至該光纖探頭，其中光纖探頭將光信號該反射回該光纖路 徑，且該光纖探頭依該待測電磁波信號的強度，使該被反 射的光信號產生具有對應改變的一變化量。又，利用光學 極化特性例如極化分光鏡，，將該被反射的光信號的該變 化量分離出來。接著，將該光信號的該變化量轉變成為一 電性信號，以供分析之用。又，該光信號在控制下，以使 相對於待測電磁波信號有無差頻的一相位延遲。 依照本發明的一實施例，於前述光纖式電光取樣方 法，其中該雷射光源與該光纖探頭之間還包括使用一極化 控制器，將該光信號做一偏極控制，以輔助該變化量被分 離出來。 依照本發明的一較佳實施例，於前述光纖式電光取樣 1295376 18639twf.doc/g 方法，其中該雷射光源與該光纖探頭之間還包括 色散補償光纖。 、依照本發明的一較佳實施例，於前述光纖式電光取樣 方法，其中控制該光信號的步驟，是利用一相位調制方法 進行。 ▲為讓本發明之上述和其他目的、特徵和優點能更明顯 易II下文特舉較佳實施例，並配合所附圖式，作詳細說 明如下。 ' 【實施方式】 y本發明整體考量傳統的電光取樣裝置的一些缺點 後，提出幾個解決方法。首先針對傳統使用的大型藍寶 石，射以及在自由空間傳播光信號的問題，本發明提出使 用簡單的半導體雷射或是光纖雷射，又更例如是增益開關 半導體雷射(gain_switch laser diode)。同時，為了使光路徑 轉變成為完全光纖路徑，增益開關半導體雷射或是光纖雷 射了以再配合色散補償光纖(dispersion compensation fiber) 等的光脈衝壓縮技術，可以產生ps等級的短脈衝，如此可 以貫現短脈衝光源光纖化，且符合脈衝重複率可調的需 求。光路徑也可以有效地被轉換成光纖傳播。 又，傳統的取樣脈衝相對待測微波信號的偵測是採 2差頻式鎖相迴路架構。本發明提出以無差頻的鎖相迴路 架構取代，藉由相位追蹤的方法即可與自由振盪微波信號 源的外部時脈(external clock)達成同步。如此對於各種高^ 電路的量測會更具有彈性變化。 ' 12 1295376 18639twf.doc/g 減差頻的鎖相迴路做為待測微波信號取樣In accordance with an embodiment of the present invention, in the fiber optic electro-optic sampling device' wherein the f-element is a semiconductor laser, such as a gain switch semiconductor laser. The invention is further characterized by a fiber optic electro-optic sampling method for sampling an electromagnetic wave signal to be measured. The method includes providing a laser unit to generate an optical signal, and a fiber optic probe. And transmitting, by the optical fiber, the optical signal to the optical fiber probe, wherein the optical fiber probe reflects the optical signal back to the optical fiber path, and the optical fiber probe generates the reflected optical signal according to the intensity of the electromagnetic wave signal to be tested. Corresponding to a change in the change. Further, the amount of change in the reflected optical signal is separated by optical polarization characteristics such as a polarization beam splitter. The amount of change in the optical signal is then converted into an electrical signal for analysis. Further, the optical signal is under control to delay a phase with or without a difference frequency with respect to the electromagnetic wave signal to be measured. According to an embodiment of the present invention, in the fiber optic electro-optic sampling method, the laser light source and the fiber optic probe further comprise a polarization controller to perform the polarization control to assist the change. The amount is separated. In accordance with a preferred embodiment of the present invention, in the fiber optic electro-optic sampling method of 1295376 18639 twf.doc/g, wherein the laser source and the fiber optic probe further comprise a dispersion compensating fiber. According to a preferred embodiment of the present invention, in the fiber optic electro-optic sampling method, the step of controlling the optical signal is performed by a phase modulation method. The above and other objects, features, and advantages of the present invention will become more apparent from the description of the appended claims. [Embodiment] y The present invention considers some shortcomings of the conventional electro-optic sampling device as a whole, and proposes several solutions. First, the present invention proposes to use a simple semiconductor laser or a fiber laser for a large-scale sapphire used conventionally, and to emit light signals in free space, and more specifically, a gain-switch laser diode. At the same time, in order to transform the optical path into a complete fiber path, a gain-switching semiconductor laser or a fiber laser is used in conjunction with an optical pulse compression technique such as a dispersion compensation fiber to generate a short pulse of ps level. The short-pulse source fiber can be realized and meets the requirements of adjustable pulse repetition rate. The optical path can also be effectively converted into fiber propagation. Moreover, the detection of the conventional sampling pulse relative to the microwave signal to be tested is a difference frequency phase-locked loop architecture. The present invention proposes to replace the external clock of the free-running microwave signal source by the phase tracking method by replacing the phase-locked loop architecture with no difference frequency. Thus, the measurement of various high-voltage circuits will have more elastic changes. ' 12 1295376 18639twf.doc/g Reduced frequency phase-locked loop as sample of microwave signal to be tested
取樣脈魅號的解與對待測微 同達到同步1而’為了能掃描微波信號 =iiJ以改變取樣脈衝信號的相位，使相對於待 相位有—相位差。如此，依不同的相位差大 小’取樣脈衝信號可以調整在待測微波信號的不同時間點 ^ ’進行取樣。又例如經由適當的自動調制，則可以掃描 待測微波錄。以下舉-些實_做為說明，但是本發明 不僅限於這些實施例。 立圖3 %示依據本發明—實施例，—電絲樣系統架構 不意圖:參閱圖3’本發明的電光取樣系統架構例如包括 一雷射單元，以增益開關半導體雷射300為例。然而，亦 可使用其他的半導體f射或光纖雷射等。X，如果不考慮 成本等，也可以使用傳統的鈦:藍寶石雷射。 增益開關半導體雷射300產生一光信號，即是取樣短 脈衝，藉由光纖被傳送到一光纖耦合器310。如果必要， 可以利用一色散補償光纖308進行脈衝壓縮。光纖耦合器 310的一端繼續將光信號，藉由光纖方式傳送到一極化控 制器312。為達到光纖化的效果，極化控制器312可以是 光纖式極化控制器，但是極化控制器312也可以包括一 λ/2 波片與一 λ/4波片的不同二延遲片所組成。極化控制器312 的作用疋將來回穿過的光的偏極態轉變，以利後續將所要 的光信號的分量分離出來。由增益開關半導體雷射3〇〇來 13 1295376 18639twf.doc/g 的光信號先經過極化控制器312產生預定的偏極態，接著 以光纖傳送到一光纖探頭314。本發明的光纖探頭314的 結構會於圖6做較詳細說明。 另外’此時的待測電磁波例如是由一微波信號源302 控制一微波電路306所產生的一待測微波信號。微波信號 的振幅對應一頻率而振盪。換句話說，在一週期内，在不 同時間點的振幅會有變化，也就是電場會有變化。光纖探 頭314的電光晶體，會依當下時間點上的電場強度，改變 其折射率，因此當光信號被電光晶體反射後，光信號的偏 極態會再度改變，也因此對應地產生強度變化量。此被反 射的光信號返回經過極化控制器312後，其偏極態又再度 被轉變。藉由光纖耦合器將被反射的光信號，藉由光纖^ 迗到一極化分光鏡316。由於極化控制器312的設置，會 將光信號適當轉換成一特定的偏極方向，因此極化分光鏡 316可以將含有強度變化量的光信號分量分離出來。接 著，被分離出來的光信號，例如藉由感光器(ph〇t〜sens〇r)， 例如感光二極體318(ph〇t〇di〇de)，將光信號轉換成電性信 號。此電性信號可供信號分析單元320進行分析。又，^ 配口光、哉化的设计，極化控制器312與極化分光鏡316都 可以採用光纖式的極化控制器與極化分光鏡。 又，針對無差頻機制而言，可以使用二差頻相移式 、貞相圮路304達成。無差頻相移式鎖相迴路3〇4連接於妗 ，關半導體雷射·與微波信號源3〇2之間，用以控^ -相對時間。例如無差頻相移式鎖相迫路3〇4可以同時 1295376 18639twf.doc/g 接收微波信號源302的發出控制微波電路306的信號，根 • 據其頻率控制增益開關半導體雷射300，以發出有相同頻 _ 率但是有一相位差的脈衝光信號。也就是說，相位差會對 應微波信號的一時間點，因此可以測出在此時間點的振 中田。增盈開關半導體雷射3〇〇在適當的驅動電流與震盪頻 率U周制下，可以產生大約是皮秒，DO等級的短 脈衝，已提供光取樣所需的探測光源。又，藉由無差頻相 Φ 移式鎖相迴路Sod，自動調制出一序列的相位差變化以驅 動锫射’就可以自動掃描微波信號的振幅變化。 以下對於各單元的較細部結構做描述。圖4繪示依據 本發明增益開關半導體雷射的電路方塊示意圖。參閱圖 4 仏號產生裔400輸出一驅動信號。驅動信號經功率放 大器402放大後，又經一梳型產生器4〇4產生短脈衝信號 做為增盈開關的调制電流。一 Bias_Tee |馬合電路4Q6，孝馬 合短脈衝信號和一直流電流源。在直流電流低於臨界電流 馨 之操作下驅動雷射二極體408，即可藉由短脈衝調制以產 生增益開關效果。所激發的短脈衝雷射，例如約有2〇 ps 的脈衝寬度。然而，如圖3所述，脈衝寬度可以利用色散 補償機制進一步壓縮，也就可以達到約lps的範圍。當然， 色散補償機制的採用是依實際需要的脈衝寬度而定，但是 至少可以達到1 ps的範圍。依雷射的特性，本發明相同的 5又计原理也可以應用在小於1 pS的範圍。 圖5繪示依據本發明一實施例，無差頻相移式鎖相迴 路結構示意圖。參閱圖5,無差頻相移式鎖相迴路5〇4例 15 1295376 18639twf.doc/g 如是由一除頻器（+N)506，一鎖相迴路(phase-l〇cked loop， • PLL) 508，以及一相移器(Phase shifter)510所串接組成，並 • 且此迴路504與微波信號源5〇〇串接，以滿足待測微波信 號與取樣光脈衝同步的要求。微波信號源5〇〇同步控制微 波電路502，以產生待測微波信號。又，相移器51〇例如 可I二由外加的直流電壓或是一鑛齒波信號 512調制，以改變取樣脈衝相對於微波信號的相位，亦即 • ^調整其相對延遲時間。一般而言，當取樣脈衝的相位改 變時，取樣脈衝對微波信號的取樣時間點也相對改變。只 要掃描一個週期的微波信號，就可完成整個取樣動作。 此外’由於無差頻相移式鎖相迴路5〇4是透過相位改 變來掃描其相對時間延遲，因此即使信號重複率有極大的 改變，也不會實質上影響對待測微波信號的取樣時間的完 整性。如此不但可以取代傳統光學機械式等效光程時間延 ，線的結構，也可以避免可能衍生的量測失真、體積龐大、 φ #描速度慢等的問題。又，本發明可以避免差頻式量測成 本過高與不具頻率獨立(frequency作的缺 點，因此成為高頻電路電光取樣系統同步的較佳方式。、 圖6繪示依據本發明一實施例，光纖探頭結構示意 圖。參閱圖6，光纖探頭例如是由一光纖6〇〇，一玻璃套^ (glass ferrule)602、一石英管(quartz tube)6〇4、一漸變折射 率透鏡(GRIN lens) 606、以及一電光晶體6〇8所組成。光 纖600例如是單模光纖。電光晶體6〇8的兩側分別鍍上抗 反射臈和高反射膜，有抗反射膜的表面以膠黏合於石英管 1295376 18639twf.doc/g 604上。選擇適當長度的漸變折射率透鏡6〇6，並且調整透 鏡606與電光晶體608之間距，以及透鏡606與玻璃套筒 • 602的距離。如此，可以使光纖600所輸出的光信號，經 由透鏡606準確聚焦到電光晶體608的高反射膜上。接著， 微調電光晶體608相對石英管604的角度，使反射光能準 確耦合回原光纖600中，以降低耦合損耗(coupiingl〇ss)， 也同時提高訊噪比(Signal-to_Noise Ratio)。此外，電光晶 • 體6〇8的選擇也是要考慮。除了晶體的電光係數要考量 外，晶轴的的選擇也是要考慮的因素之一。一般常用的電 光晶體608例如有蹄化辞(znTe)、砷化鎵(GaAs)、鈮酸鋰 (LiNb〇3)、钽酸鋰(LiTa〇3)、磷酸二氫鉀(KDP)等。 在光纖化的設計下，極化控制器312與極化分光鏡 316都可以採用光纖式的極化控制器與極化分光鏡，構成 一種全光纖取樣系統。架設全光纖系統之關鍵，是在於取 樣光源的波長。對於波長為1·3微米或ι·55微米的雷射二 體而言，其相關的光通訊元件的技術已都完備，因此雷射 二極體，配合光纖的技術可以達到廣泛的應用，於此 續詳述。 又，關於無差頻相移式鎖相迴路的設計，其也不僅限 圖5的設計。無差頻相移式鎖相迴路也可以由二除頻哭广 =鎖相迴路，以及一相位調制電路所組成，以輸出一'&制 信號，調整雷射單元的取樣光信號的一相位延遲。圖7繪 示依據本發明一實施例，無差頻相移式鎖相迴路另一結才^ 示意圖。參閱圖7，無差頻相移式鎖相迴路7〇〇，例如:括 17 1295376 18639twf.doc/g 一相位頻率偵測器(phase_Frequency Detector，PDF)704 ,與 微波信號源500耦接，以測得微波電路5〇2所產生的微2 信號的頻率。接著，一加法電路71〇耦接在相位頻率偵測 器^04與一迴路濾波器712之間。加法電路71〇又接收由 功能產生器（functional generat〇r)7〇2所輸入的一直流電 壓、一鋸齒波信號、或是一鋸齒波相位調制信號。迴路濾 波yi2接收加法電路71〇的輸出後，輸出一控制信號給 一電壓控制振盪器(v〇ltage contr〇1 〇sciUat〇r，vc〇) 7〇8。 此電壓控制振盪器708藉由一除頻器(+Ν)706與相位頻率 偵測為704輕接，得到微波信號的頻率訊息，於是輸出一 控制信號，調整增益開關半導體雷射514的取樣光信號相 對於待測微波信號的一相位延遲。另外，可以藉由相位調 制，改變相位延遲的大小，以達到掃描微波信號的取樣。 圖8繪示依據本發明一實施例，無差頻相移式鎖相迴 路又另一結構示意圖。參閱圖8，無差頻相移式鎖相迴路 800也可以有另一種設計，與圖7類似，但是可以配合使 用由微分電路(d/dt)801先進行微分後的鋸齒微分信號。由 相位頻率偵測器704輸出的信號，可以先經過迴路濾波器 802，再藉由加法電路804，將鋸齒微分信號引入，以控制 電壓控制振盪器708，進而調整增益開關半導體雷射514 的取樣光彳a號相對於待測微波信號的一相位延遲。 基本上，無差頻相移式鎖相迴路的作用是要調制增益 開關半導體雷射514 ,以產生與待測微波信號的頻率同步 但是具有所要相位延遲的取樣光信號。至於電路設計上， 1295376 18639twf.doc/g 可以有不同變化，不限於所舉的實施例。 又就方法而言，本發明提出一種光纖式電光取樣方 法’以對一待測電磁波信號取樣。此方法包括提供一雷射 單元以產生一光信號，以及一光纖探頭。又，利用光纖， 將光信號引導至光纖探頭，其中光纖探頭將光信號反射回 光纖路徑，且光纖探頭依待測電磁波信號的強度，使被反 射的光化號產生具有對應改變的一變化量。接著，利用光 φ 學極化特性例如極化分光鏡，將該被反射的光信號的該變 化量分離出來。接著，將該光信號的該變化量轉變成為一 電性b號，以供分析之用。又，光信號在控制下，可以相 對於待測電磁波信號有無差頻的一相位延遲。 又例如，該雷射光源與該光纖探頭之間還包括使用一 極化控制器，將該光信號做一偏極控制，以辅助該變化量 被分離出來。 又例如，該雷射光源與該光纖探頭之間還包括使用一 段色散補償光纖。又例如，控制該光信號的步驟是利用一 ® 相位調制方法進行。 本發明由於採用貫質上全光纖的設計，因此可以有效 減少對準的要求或是進而不需要對準。 本發明提供一種光纖式電光取樣裝置與方法，可以操 作於無差頻的條件下。除了節省由於差頻造成的成本增加 外，且不受頻率變化的影響，可以使系統有更多方便^應 用。 μ 雖然本發明已以較佳實施例揭露如上，然其並非用以 19 1295376 18639twf.doc/g 限^本發明，任何熟習此技藝者，在不脫離本發明之精神 ^範圍内，當可作些許之更動與潤飾，因此本發明之保護 範圍當視後附之申請專利範圍所界定者為準。 【圖式簡單說明】 ^ =示傳統的一種電光取樣系統架構示意圖。 圖2、、、曰示傳統的另一電 ― @ 樣絲構不意圖。The solution of the sampling pulse charm is synchronized with the measurement to achieve synchronization 1 and 'to scan the microwave signal = iiJ to change the phase of the sampling pulse signal so that there is a phase difference with respect to the phase to be phased. Thus, depending on the difference in phase difference, the sampling pulse signal can be adjusted at different time points ^' of the microwave signal to be measured. For another example, via appropriate automatic modulation, the microwave recording to be tested can be scanned. The following are some examples, but the present invention is not limited to these embodiments. Figure 3 shows a system according to the invention - an embodiment of a wire-like system. It is not intended to refer to Figure 3'. The electro-optic sampling system architecture of the present invention includes, for example, a laser unit, exemplified by a gain-switching semiconductor laser 300. However, other semiconductor f-beams or fiber lasers or the like can also be used. X, if you do not consider the cost, etc., you can also use the traditional titanium: sapphire laser. The gain switching semiconductor laser 300 produces an optical signal, i.e., a sampled short pulse, which is transmitted to a fiber coupler 310 by an optical fiber. If necessary, pulse dispersion can be performed using a dispersion compensating fiber 308. One end of the fiber coupler 310 continues to transmit the optical signal to a polarization controller 312 by fiber optics. In order to achieve the effect of fiberization, the polarization controller 312 may be a fiber-optic polarization controller, but the polarization controller 312 may also comprise a λ/2 wave plate and a different lag plate of a λ/4 wave plate. . The role of polarization controller 312 is to shift the polar state of the light passing back and forth to facilitate subsequent separation of the desired components of the optical signal. The optical signal from the gain-switching semiconductor laser 13 1295376 18639 twf.doc/g is first subjected to a polarization controller 312 to generate a predetermined polarization state, and then transmitted to a fiber optic probe 314 as an optical fiber. The structure of the fiber optic probe 314 of the present invention will be described in greater detail in FIG. In addition, the electromagnetic wave to be tested at this time is, for example, a microwave signal to be measured generated by a microwave signal source 302 controlled by a microwave signal source 302. The amplitude of the microwave signal oscillates corresponding to a frequency. In other words, in one cycle, the amplitude of the point will change at different points, that is, the electric field will change. The electro-optic crystal of the fiber optic probe 314 changes its refractive index according to the electric field strength at the current time point. Therefore, when the optical signal is reflected by the electro-optic crystal, the polarization state of the optical signal changes again, and accordingly the intensity variation is correspondingly generated. . After the reflected optical signal is returned through the polarization controller 312, its polar state is again transformed. The optical signal to be reflected by the fiber coupler is passed through a fiber to a polarization beam splitter 316. Due to the setting of the polarization controller 312, the optical signal is appropriately converted into a specific polarization direction, so that the polarization beam splitter 316 can separate the optical signal component containing the intensity variation. Then, the separated optical signal is converted into an electrical signal by, for example, a photoreceptor (ph〇t~sens〇r), such as a photodiode 318 (ph〇t〇di〇de). This electrical signal is available for analysis by signal analysis unit 320. Moreover, the design of the matching light and the dimming, the polarization controller 312 and the polarization beam splitter 316 can both adopt a fiber-type polarization controller and a polarization beam splitter. Further, for the no-frequency difference mechanism, the two-difference phase shift type and the phase difference path 304 can be used. The difference-free phase-shifting phase-locked loop 3〇4 is connected between the 半导体, the semiconductor laser and the microwave signal source 3〇2 to control the relative time. For example, the difference-free phase-shifting phase-locking forced channel 3〇4 can simultaneously receive the signal of the microwave signal source 302 and the control microwave circuit 306, and control the gain-switching semiconductor laser 300 according to the frequency thereof. A pulsed light signal having the same frequency _ rate but having a phase difference is emitted. That is to say, the phase difference corresponds to a point in time of the microwave signal, so that the vibrating field at this point in time can be measured. The Zener Switch Semiconductor Laser 3 can produce short pulses of approximately picosecond, DO level at the appropriate drive current and oscillation frequency U-cycle, providing the detection source required for optical sampling. Moreover, the amplitude variation of the microwave signal can be automatically scanned by automatically modulating a sequence of phase difference changes to drive the radiance by the difference-free phase Φ-shift phase-locked loop Sod. The following describes the finer structure of each unit. 4 is a block diagram showing the circuit of a gain switching semiconductor laser in accordance with the present invention. Refer to Figure 4 for the nickname Genesis 400 output a drive signal. After the drive signal is amplified by the power amplifier 402, a short pulse signal is generated by a comb generator 4〇4 as a modulation current of the gain-increasing switch. A Bias_Tee | Mahe Circuit 4Q6, Xiaoma combined with a short pulse signal and a current source. Driving the laser diode 408 with a DC current below the critical current can produce a gain switching effect by short pulse modulation. The short pulsed laser that is excited, for example, has a pulse width of about 2 〇 ps. However, as illustrated in Figure 3, the pulse width can be further compressed using a dispersion compensation mechanism to achieve a range of approximately lps. Of course, the dispersion compensation mechanism is based on the actual required pulse width, but can reach at least 1 ps. The same principle of the invention can also be applied in the range of less than 1 pS depending on the characteristics of the laser. FIG. 5 is a schematic diagram showing the structure of a phase-shifted phase-locked loop without a difference frequency according to an embodiment of the invention. Referring to Figure 5, there is no difference frequency phase shifting phase-locked loop 5〇4 cases 15 1295376 18639twf.doc/g If it is a frequency divider (+N) 506, a phase-locked loop (phase-l〇cked loop, • PLL 508, and a phase shifter 510 are connected in series, and the loop 504 is connected in series with the microwave signal source 5〇〇 to meet the requirement of synchronizing the microwave signal to be sampled with the sampled light pulse. The microwave signal source 5 〇〇 synchronously controls the microwave circuit 502 to generate a microwave signal to be measured. Further, the phase shifter 51 can be modulated, for example, by an applied DC voltage or a mine tooth signal 512 to change the phase of the sampling pulse with respect to the microwave signal, i.e., to adjust its relative delay time. In general, when the phase of the sampling pulse changes, the sampling time of the sampling pulse to the microwave signal also changes relatively. The entire sampling action can be completed by scanning the microwave signal for one cycle. In addition, since the phase difference-free phase-locked loop 5〇4 scans its relative time delay through phase change, even if the signal repetition rate is greatly changed, it does not substantially affect the sampling time of the microwave signal to be measured. Integrity. This can not only replace the traditional optical mechanical equivalent optical path delay, the structure of the line, but also avoid the problems of measurement distortion, large volume, slow speed of φ #, etc. Moreover, the present invention can avoid the disadvantage that the differential frequency measurement is too costly and not frequency independent (the frequency is disadvantaged, so it is a better way to synchronize the high frequency circuit electro-optic sampling system. FIG. 6 illustrates an embodiment according to the present invention, Schematic diagram of the fiber optic probe. Referring to Figure 6, the fiber optic probe is composed of, for example, a fiber 6 〇〇, a glass ferrule 602, a quartz tube 6 〇 4, and a gradient index lens (GRIN lens). 606, and an electro-optic crystal 6 〇 8. The optical fiber 600 is, for example, a single-mode optical fiber. The electro-optical crystal 6 〇 8 is respectively plated with anti-reflection 高 and high-reflection film, and the surface of the anti-reflection film is bonded to the quartz. Tube 1295376 18639twf.doc/g 604. Select a gradient index lens 6〇6 of appropriate length, and adjust the distance between the lens 606 and the electro-optic crystal 608, and the distance between the lens 606 and the glass sleeve 602. Thus, the fiber can be made The optical signal outputted by 600 is accurately focused onto the highly reflective film of the electro-optic crystal 608 via the lens 606. Next, the angle of the electro-optic crystal 608 relative to the quartz tube 604 is fine-tuned so that the reflected light can be accurately coupled back to the original light. In the fiber 600, to reduce the coupling loss (coupiingl〇ss), and also improve the signal-to-noise ratio (Signal-to_Noise Ratio). In addition, the choice of electro-optical crystal body 6〇8 is also considered. In addition to the electro-optic coefficient of the crystal to be considered The choice of the crystal axis is also one of the factors to be considered. The commonly used electro-optic crystal 608 is, for example, hoof (znTe), gallium arsenide (GaAs), lithium niobate (LiNb〇3), lithium niobate (LiTa). 〇3), potassium dihydrogen phosphate (KDP), etc. In the fiber optic design, both the polarization controller 312 and the polarization beam splitter 316 can use a fiber-type polarization controller and a polarization beam splitter to form a full Fiber-optic sampling system. The key to erecting an all-fiber system is the wavelength of the sampled source. For lasers with a wavelength of 1.3 μm or ι·55 μm, the technology of the associated optical communication components is complete. Therefore, the laser diode can be used in a wide range of applications with fiber optics. Further, the design of the phase-shifted phase-locked loop with no difference frequency is not limited to the design of Figure 5. Phase-shifted phase-locked loop can also be divided by two frequency divisions = lock phase The loop, and a phase modulation circuit, are configured to output a '& signal to adjust a phase delay of the sampled optical signal of the laser unit. FIG. 7 illustrates a phase shift-free lock according to an embodiment of the invention. The other phase of the phase loop is shown in Fig. 7. The phase difference phase shifting phase-locked loop 7〇〇, for example: 17 1295376 18639twf.doc/g phase_Frequency Detector (PDF) 704, The microwave signal source 500 is coupled to measure the frequency of the micro 2 signal generated by the microwave circuit 5〇2. Then, an adder circuit 71 is coupled between the phase frequency detector ^04 and the loop filter 712. The adding circuit 71 receives the DC voltage, a sawtooth signal, or a sawtooth phase modulation signal input by the functional generator 7r2. After receiving the output of the adding circuit 71A, the loop filter yi2 outputs a control signal to a voltage controlled oscillator (v〇ltage contr〇1 〇sciUat〇r, vc〇) 7〇8. The voltage controlled oscillator 708 is connected to the phase frequency detection 704 by a frequency divider (+Ν) 706 to obtain a frequency information of the microwave signal, and then outputs a control signal to adjust the sampling light of the gain switching semiconductor laser 514. The signal is delayed relative to a phase of the microwave signal to be measured. In addition, the phase delay can be changed by phase modulation to achieve sampling of the scanned microwave signal. FIG. 8 is a schematic diagram showing still another structure of a phase-shifted phase-locked loop without a difference frequency according to an embodiment of the invention. Referring to Figure 8, the difference-free phase-shifted phase-locked loop 800 can have another design, similar to Figure 7, but can be used in conjunction with a saw-tooth differential signal that is differentiated by a differential circuit (d/dt) 801. The signal output by the phase frequency detector 704 may first pass through the loop filter 802, and then the adder circuit 804 introduces the sawtooth differential signal to control the voltage controlled oscillator 708, thereby adjusting the sampling of the gain switching semiconductor laser 514. The aperture a is delayed relative to a phase of the microwave signal to be measured. Basically, the effect of the difference-free phase-shifted phase-locked loop is to modulate the gain-switching semiconductor laser 514 to produce a sampled optical signal that is synchronized with the frequency of the microwave signal to be measured but has the desired phase delay. As for the circuit design, 1295376 18639twf.doc/g may vary, and is not limited to the embodiment. Still in terms of method, the present invention provides a fiber optic electro-optic sampling method for sampling a signal to be measured. The method includes providing a laser unit to generate an optical signal, and a fiber optic probe. Moreover, the optical signal is guided to the optical fiber probe by using the optical fiber, wherein the optical fiber probe reflects the optical signal back to the optical fiber path, and the optical fiber probe generates a change amount corresponding to the changed actinic number according to the intensity of the electromagnetic wave signal to be measured. . Next, the amount of change in the reflected optical signal is separated by optical polarization characteristics such as a polarization beam splitter. The amount of change in the optical signal is then converted to an electrical b number for analysis. Moreover, under control, the optical signal can be delayed by a phase relative to the electromagnetic wave signal to be measured. For another example, the laser source and the fiber optic probe further comprise a polarization controller to perform a polarization control to assist in separating the variation. For another example, the laser source and the fiber optic probe further comprise a dispersion compensation fiber. For another example, the step of controlling the optical signal is performed using a ® phase modulation method. The present invention utilizes a design of a permeated all-fiber to effectively reduce alignment requirements or, in turn, eliminate alignment. The present invention provides a fiber optic electro-optical sampling apparatus and method that can operate under conditions of no difference frequency. In addition to saving the cost increase due to the difference frequency, and not being affected by the frequency change, the system can be more convenient. Although the present invention has been disclosed in the above preferred embodiments, it is not intended to be limited to the scope of the present invention, and any one skilled in the art can make it without departing from the spirit of the invention. The scope of protection of the present invention is defined by the scope of the appended claims. [Simple description of the figure] ^ = shows a schematic diagram of a conventional electro-optical sampling system architecture. Figure 2, and Figure 2 show the traditional electric _ @丝丝结构不意.
口 乂、、日不依據本發明_實施例，一 示意圖。 貝1』 兒先取樣系統架構 圖4繪示依據本發明〜實 的電路方塊示意圖。 貫j胃皿開關+導體雷射 圖5繪示依據本發明〜實 路結構示意圖。 貝_無差頻相移式鎖相迴 热差頻相移式鎖相迴 圖8繪示依據本發明〜實施例， 路又另一結構示意圖。 【主要元件符號說明】 100 :鈦:藍寶石雷射 102 :信號產生器 104 :微波信號源 106:補償器 108:極化分光鏡 112:物鏡 406:Bias-Tee_ 合電路 4〇8:雷射二極體 5〇〇:微波信號源 502:微波電路 504:無差頻相移式鎖相迴路 506:除頻器 18639twf.doc/g 1295376The present invention is not illustrated in accordance with the present invention. The first sampling system architecture of Fig. 1 is a block diagram of a circuit according to the present invention. j 胃 胃 + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + Bell_No Difference Frequency Phase Shifted Phase Locked Back Thermal Differential Frequency Phase Shifted Phase Locked Back Figure 8 is a schematic diagram showing another structure according to the embodiment of the present invention. [Main component symbol description] 100: Ti: Sapphire laser 102: Signal generator 104: Microwave signal source 106: Compensator 108: Polarizing beam splitter 112: Objective lens 406: Bias-Tee_ Combined circuit 4〇8: Laser two Polar body 5〇〇: microwave signal source 502: microwave circuit 504: no difference frequency phase shifting phase-locked loop 506: frequency divider 18639twf.doc/g 1295376
114 :電光晶體 116 : 微波電路 118 :感光二極體 120:鎖相放大器 122 :信號分析單元 124 :光纖探頭 126 : 極化控制器 128 :光耦合器 300 ·.增益開關半導雷射 302 :微波信號源 304:無差頻相移式鎖相迴路 306 : 微波電路 308 :色散補償光纖 310 :光纖柄合器 312 : 極化控制器 314 :光纖探頭 316 : 極化分光鏡 318 :感光二極體 320 :信號分析單元 400 ·.信號產生器 402 : 功率放大器 404 ·.梳型產生器 508:鎖相迴路 510:相移器 512:鋸齒波信號 514:增益開關半導雷射 600:光纖 602:玻璃套筒 604:石英管 606:漸變折射率透鏡 608·.電光晶體 700:無差頻相移式鎖相迴路 702:功能產生器 704:相位頻率偵測器 706:除頻器 708:電壓控制振盪器 710:加法電路 712:迴路濾波器 800:無差頻相移式鎖相迴路 801:微分電路 802:迴路濾波器 804:加法電路 21114: electro-optical crystal 116: microwave circuit 118: photodiode 120: lock-in amplifier 122: signal analysis unit 124: fiber optic probe 126: polarization controller 128: optocoupler 300 · gain switch semi-guided laser 302: Microwave signal source 304: no difference frequency phase shifting phase locked loop 306: microwave circuit 308: dispersion compensating fiber 310: fiber optic shank 312: polarization controller 314: fiber optic probe 316: polarizing beam splitter 318: photodiode Body 320: Signal Analysis Unit 400. Signal Generator 402: Power Amplifier 404. Comb Generator 508: Phase Locked Loop 510: Phase Shifter 512: Sawtooth Signal 514: Gain Switch Semi-Directed Laser 600: Fiber 602 : Glass sleeve 604: Quartz tube 606: Gradient index lens 608 · Electro-optical crystal 700: No difference frequency phase shifting phase-locked loop 702: Function generator 704: Phase frequency detector 706: Frequency divider 708: Voltage Control oscillator 710: Addition circuit 712: Loop filter 800: No difference frequency phase shift type phase locked loop 801: Differentiating circuit 802: Loop filter 804: Adding circuit 21