外文翻譯---波形合成電路的分析與設(shè)計(jì)

1、<p><b>　　附錄二：英文原文</b></p><p>　　The Analysis and Design of Waveform Generator</p><p>　　Xue lian ,Wang Fan ,Zheng Jin-fa</p><p>　　Engineering and Commerce College, So

2、uth-Central University for Nationalities, Wuhan Hubei 430065</p><p>　　Abstract: In this paper, the sinusoidal waves in different frequency were synthesized into square wave according to the method of Fourier

3、 series. Firstly, the needed sinusoidal waves were achieved through the square wave generation circuit, the frequency division circuit and the filter circuit; then, after the sinusoidal waves’ phase position were shifted

4、 and synthesized, the square wave was generated. This circuit in this method was more cheaper than other circuits (eg: DDS). </p><p>　　Keywords: Waveform Generator;Sinusoidal Wave; Filter;Phase Position Shif

5、t</p><p>　　1 waveform synthesis system overview</p><p>　　This is designed to simulate the process of signal synthesis. For a square wave signal by Fourier series spread knowable, it can decompos

6、e the amplitude of the more specific for unlimited odd harmonics, so in turn as long as infinite multiple odd harmonic component, the amplitude and the harmonic proportion in a particular superposition, also will certain

7、ly get a square wave signal. This paper is the simulated the base wave and three harmonic harmonic component synthesis process of square wave s</p><p>　　This system begin with a square wave oscillator to gen

8、erate a frequency of 60KHz pulse signal, again into separate frequency device 10KHz to get a frequency for handling of square wave signal and a frequency of square wave signal for 30KHz, then respectively through the fil

9、ter processing for the sine signal and 30KHz 10KHz to close-spaced 10KHz sine wave as base wave component, 30KHz sine wave as three times, through modulation circuit harmonics of adjust them respectively in fengfeng valu

10、e, can</p><p>　　Figure 1 system structure diagram</p><p>　　2 the hardware circuit design</p><p>　　2.1 square wave generating circuit design</p><p>　　According to the ab

11、ove analysis, the 60kHz should be produced for pulse frequency. Square wave can use digital circuit generation, also can use analog circuits produce. As digital circuits produce waveform amplitude, needs to be smaller us

12、ing simulated circuit to amplify; And compared with mixed-signal circuit pure analog circuits to complex, therefore, in this the paper only with analog circuits to generate square wave. The basic principle is: through th

13、e voltage comparator produce high level; </p><p>　　Front generated for square can't use, this latter stage, still need to pass the follow-up processing, should first except negative voltage isolation, he

14、re with a diode, so after diode for the voltage after subtracting tube voltage half before diode pressure drop. Thus square wave amplitude will more small, in order to achieve the minimum separate frequency circuit requi

15、rements, should be the voltage waveforms were pressurization. In proportion with pressor circuit USES amplifier, get the voltage</p><p>　　Figure 2 square wave generating circuit principle diagram</p>

16、<p>　　2.2. Points frequency circuit design</p><p>　　This points to the former stage frequency circuits are produced, into a square 60KHz 390v for 1/2, frequency respectively. 30KHz And the square wave s

17、ignal 10KHz. This treatment can easily think of using digital counter solve. The counter is commonly used sequential circuits to pulse, it not only can count, can also used for the points frequency, timing, produce beats

18、 pulse, etc. This paper use of its points frequency characteristics, a N disables counter can will it input clock signal, points f</p><p>　　For digital counter choice is the key to realizing points frequency

19、. If using common integrated counter 74LS \ HC163, such as (74LS \ HC161) constitute the counter, required disables 390v will appear uncertain situation, need separate frequency, adding in 390v regulating circuit, which

20、makes the circuit is not stable and structure is more complex. And use trigger level could be behind the counter 390v good control, so the system USES a JK flip-flop composition counter, T flip-flop and D flip-flo</p&

21、gt;<p>　　Figure 3 points frequency circuit principle diagram</p><p>　　2.3 filter and modulation circuit design</p><p>　　Filter circuit 10KHz mainly completes 10KHz sine wave, 30KHz square

22、 to the transformation of 30KHz sine pulse to. Ideal square wave is contains all the odd frequency components, as long as the signal through specific center frequency of frequency selective network, very easy to obtain t

23、he required frequency sine wave. Considering the effect of grade synthetic after, this system directly choose the integrated bart hepworth fourth-order low-pass filter, simply switched capacitor TLC04ID appropriat</p&

24、gt;<p>　　If the yankees 10KHz sinusoidal signal as 30KHz sine wave, three times as a signal of harmonic, synthetic a 10KHz by square wave signal, then Fourier decomposition knowable, 30KHz 10KHz sinusoidal signal

25、and the extent of the sine signals for 1:3 than needed. Because the former stage two sine signal filtered in fengfeng value is required for 5V, both by the 30KHz 10KHz and amplitude circuit of sine wave 6V respectively i

26、n fengfeng value for adjustment and 2V.</p><p>　　For the sine signals, need 10KHz from fengfeng value 5V 6V, so to boost processing operation circuit whetherisolated selects the proportion. And for 30KHz sin

27、usoidal line number from fengfeng value 5V, need to, so the antihypertensive treatment 2V chose simple resistance points after, to prevent voltage circuit of the resistor network level circuit influence, plus a voltage b

28、ehind need comparators. The operation circuit in the attenuation, because the sine separate frequency filtering line numbe</p><p>　　Figure 4 filter and modulation circuit</p><p>　　2.4 move and a

29、ddition circuit design</p><p>　　In order to strengthen the synthetic effect, need to treat synthetic signal phase shifting processing. Because analog synthesis signal only two, so just click on one of the si

30、gnal can be adjusted. This paper introduces the design of 10KHz sine signals in the phase adjuster phase shifting circuit. By a RC network and a voltage followed sensor into the RC network, including by large resistance

31、(R 100K adjustable, makes the signal phase in 30 ° ~ 90 can ° range adjustment, voltage comparator to pre</p><p>　　Addition to finish last is that the circuit of signal synthesis. Because the syste

32、m in the former stage of the signal amplitude ratio has adjust appropriate and circuit amplification operations in addition, no fixed proportion of input and output signal circuit amplitude adjustment, so here are the si

33、mplicity of a single integrated amp LM358 constitute addition circuit can well satisfy synthetic requirements. As shown in figure 5 shows addition circuit.</p><p>　　Figure 5 addition circuit</p><p

34、>　　2.5 measurement circuit design</p><p>　　The measurement circuit is used for measuring system of internal all sine signals, which is separate from the RMS ahead of a wave synthesis circuit happened digi

35、tal measurement unit. RMS is characterization of the ac signal amplitude is an important parameter for sine signal, the RMS for its peak / 2, i.e. only if the peak namely can get sine wave get their RMS. So in the measur

36、ement of the system as a circuit, let sine signals obtained through a peak detection circuit and the peak, its peak app</p><p>　　For peak detection circuit design, because the peak in 2 are sinusoidal wave b

37、etween 6V, to a larger extent to directly through the most simple, so a diode and capacitance series circuit, which diode rectifier role play half wave, and capacitance is keep peak voltage. Ideally if diode conduction v

38、oltage of 0V, then signal peak can accurately performance, and the actual in capacitance of the diode's conduction pressure drop not negligible, crunches the peak voltage equals conduction pressure drop</p>&l

39、t;p>　　AD chose successive comparison type, which has meet the advantages such as high speed, low consumption, eight precision measurements of the enough to satisfy the design requirements. Measuring signal amplitude 3

40、V only in 1 ~ between only one range, so measurement (0 ~ 5V) can complete, will meet the positive reference voltage input termination VCC, its negative reference voltage grounding can. SCM chose AT89C51, in dealing with

41、 AD transform results, the program adopted average filtering algorith</p><p>　　Figure 6 test circuits</p><p>　　3 system functional testing</p><p>　　Completed by two power system cur

42、rent supply for a + 5v respectively, the single power and a + 5v double power supply. Power supply reference each module circuit analysis.</p><p>　　By above each function module circuit can complete this sys

43、tem. The Chinese wave to create, produce 60KHz 3v circuit, the peak of square wave, through two separate frequency circuit the signal frequency measured respectively, 30KHz and 10KHz are 5-v square-wave peak; In through

44、a low-pass filter to get 30KHz and 10KHz, are 5-v sine wave peak; Two signal amplitude modulation circuit by respectively after treatment 30KHz corresponding 6V 10KHz corresponding 2V,; Phase shifting to 10KHz to after t

45、w</p><p>　　Finally, using measuring circuit measurements in the system, and the measurement error at various levels in sine wave within 5%.</p><p>　　Figure 7 test waveforms</p><p>　

46、　references</p><p>　　[1] TongShiBai. Analog electronic technology foundation. Beijing: higher education press, 2006 (4th edition)</p><p>　　[2] WuDaZheng with linear system analysis. Signal. Beij

47、ing: higher education press, 2005 (4th edition)</p><p><b>　　附錄三：英文翻譯</b></p><p>　　波形合成電路的分析與設(shè)計(jì)</p><p><b>　　薛蓮 汪帆 鄭錦發(fā)</b></p><p>　　中南民族大學(xué)工商學(xué)院電信系，

48、湖北 武漢 430065</p><p>　　薛蓮 (1981年11月——) 女，漢族，山東淄博，中南民族大學(xué)工商學(xué)院電信系教師，講師，工學(xué)碩士。</p><p>　　摘要：本文根據(jù)傅里葉級(jí)數(shù)展開方法，將各頻率正弦波合成為方波。首先，通過方波產(chǎn)生電路、分頻電路、濾波電路獲取所需頻率的正弦波；再通過移相電路、加法電路將正弦波合成為方波。與其他方式（如DDS）相比，此種方法具有成本低廉、可靠性

49、高等特點(diǎn)。 </p><p>　　關(guān)鍵詞：波形合成器；正弦波；濾波；移相</p><p>　　1 波形合成系統(tǒng)概述</p><p>　　本設(shè)計(jì)是為了模擬信號(hào)合成的過程。對于一個(gè)方波信號(hào)，由傅里葉級(jí)數(shù)展開可知，它可以分解為無限多個(gè)特定幅度的奇次諧波，那么反過來只要無限多個(gè)奇次諧波分量，且這些諧波的幅度按特定的比例疊加，也就一定可以得到一個(gè)方波信號(hào)。本文就是模擬了基波和

50、三次諧波諧波分量合成方波信號(hào)的過程。理論上來說，諧波分量越多時(shí)，合成的波形就會(huì)越趨近于標(biāo)準(zhǔn)的方波波形。</p><p>　　本系統(tǒng)首先用一個(gè)方波振蕩器產(chǎn)生一個(gè)頻率為60KHz的方波信號(hào)，再送入分頻器處理得到一個(gè)頻率為10KHz的方波信號(hào)和一個(gè)頻率為30KHz的方波信號(hào)，然后分別通過濾波器處理為10KHz的正弦信號(hào)和30KHz的正弦信號(hào)，把10KHz的正弦波作為基波分量，30KHz的正弦波作為三次諧波，通過調(diào)幅電路

51、調(diào)節(jié)它們的峰峰值分別為6V和2V，即可滿足傅里葉級(jí)數(shù)展開的系數(shù)比；再把10KHz的正弦信號(hào)送入移相器進(jìn)行相位調(diào)節(jié)后，和30KHz的正弦信號(hào)一起送入加法電路進(jìn)行合成，即完成信號(hào)的疊加。可以推斷，加法器的輸出信號(hào)為一個(gè)近似方波的信號(hào)，且頻率大概為10KHz。系統(tǒng)單元電路如圖1所示。</p><p><b>　　圖1 系統(tǒng)結(jié)構(gòu)框圖</b></p><p><b>

52、　　硬件電路設(shè)計(jì)</b></p><p>　　2.1方波發(fā)生電路設(shè)計(jì)</p><p>　　根據(jù)前面的分析，應(yīng)該產(chǎn)生頻率為60kHz的方波。方波可以用數(shù)字電路產(chǎn)生，也可以用模擬電路產(chǎn)生。由于數(shù)字電路產(chǎn)生的波形振幅較小，還需要應(yīng)用模擬電路進(jìn)行放大；而用數(shù)模混合電路相比純模擬電路要復(fù)雜，因此，在此本文僅用模擬電路來產(chǎn)生方波。其基本原理是：通過電壓比較器產(chǎn)生高低電平；通過反饋回路和延時(shí)

53、環(huán)節(jié)使高低電頻周期性的交替變化。原理圖如圖2所示，圖中滯回比較器的輸出電壓，閾值電壓 ；振蕩周期為。由周期計(jì)算式可知通過改變R3，C，R1與R2比值可以得到所需頻率方波。但是這幾個(gè)變量在實(shí)際電路中會(huì)存在一些約束，在選擇器件參數(shù)時(shí)應(yīng)該通過實(shí)際調(diào)節(jié)來確定。選擇器件時(shí)，建議電阻使用金屬膜電阻，這樣電路產(chǎn)生的熱噪聲就??；選運(yùn)放時(shí)要考慮它的通頻帶，通頻帶較小時(shí)，很難達(dá)到方波要求的頻率，因此我們選擇了性能很好的運(yùn)放OPA820。</p>

54、<p>　　前面所產(chǎn)生的方波還不能為后級(jí)所利用，為此，還需經(jīng)過后續(xù)處理，首先應(yīng)該隔除負(fù)向電壓，在這里用一個(gè)二極管，這樣經(jīng)過二極管后的電壓為二極管前電壓一半減去管壓降。如此一來方波幅度將更小，為了達(dá)到分頻電路要求的最小電壓，應(yīng)該將波形進(jìn)行升壓。升壓電路采用同相比例放大器，得到幅度適度的電壓。這時(shí)的電壓可以為后級(jí)所利用，但為了減小后級(jí)電路負(fù)載對方波產(chǎn)生電路的影響，提高電路帶負(fù)載能力，最后再接一個(gè)射極跟隨器。到此，方波發(fā)生電路就

55、可以達(dá)到預(yù)期要求，可以接上后級(jí)電路。</p><p>　　圖2 方波發(fā)生電路原理圖</p><p>　　2.2．分頻電路設(shè)計(jì) </p><p>　　此處的分頻電路是將前級(jí)產(chǎn)生的60KHz方波，變?yōu)橐粋€(gè)占空比為1/2，頻率分別為30KHz和10KHz的方波信號(hào)。這個(gè)處理可以很容易想到用數(shù)字計(jì)數(shù)器解決。計(jì)數(shù)器是常用的時(shí)序電路，它不僅可以對脈沖進(jìn)行計(jì)數(shù)，還可以用于分頻、定

56、時(shí)、產(chǎn)生節(jié)拍脈沖等。本文利用它的分頻特性，一個(gè)N進(jìn)制的計(jì)數(shù)器可以將它的輸入時(shí)鐘信號(hào)，分頻為占空比為1/N、頻率為輸入信號(hào)1/N的輸出時(shí)鐘信號(hào)。所以為了得到30KHz的方波信號(hào)，可以將60KHz的方波作為時(shí)鐘信號(hào)，接入一個(gè)二級(jí)制計(jì)數(shù)器，則輸出為一個(gè)占空比為1/2、頻率30KHz的方波信號(hào)。而對于10KHz的方波信號(hào)獲取，可以先讓60KHz方波信號(hào)通過一個(gè)三進(jìn)制的計(jì)數(shù)器，對應(yīng)輸出一個(gè)占空比為1/3、頻率為20KHz的方波信號(hào)，再將此信號(hào)作為

57、輸入信號(hào)，接入一個(gè)二進(jìn)制計(jì)數(shù)器，即可得到一個(gè)占空比為1/2、頻率為10KHz的方波。即將60KHz的方波信號(hào)經(jīng)過三個(gè)數(shù)字計(jì)數(shù)器處理，就獲得了滿足1/2占空比要求的10KHz和30KHz的方波信號(hào)。</p><p>　　對于數(shù)字計(jì)數(shù)器的選擇也是實(shí)現(xiàn)分頻的關(guān)鍵。如果采用常見的集成計(jì)數(shù)器如（74LS\HC163、74LS\HC161）構(gòu)成所需進(jìn)制的計(jì)數(shù)器，則會(huì)出現(xiàn)占空比不定的情況，需要在分頻后添加占空比調(diào)節(jié)電路，這就使

58、得電路不穩(wěn)定并且結(jié)構(gòu)比較復(fù)雜。而采用觸發(fā)器級(jí)聯(lián)成的計(jì)數(shù)器則可以很好的掌控占空比，故本系統(tǒng)采用了JK觸發(fā)器組成計(jì)數(shù)器，T觸發(fā)器和D觸發(fā)器也同樣可以選擇。然后需要考慮器件TTL和COMS的選擇，因?yàn)橄到y(tǒng)處理的信號(hào)均在10KHz以上頻率，若數(shù)字器件的轉(zhuǎn)換速率太低則容易導(dǎo)致計(jì)數(shù)器不能正常工作，輸出信號(hào)失真，故本文選擇了轉(zhuǎn)換速率較快的TTL器件。最終確定采用兩片74LS109（雙集成JK觸發(fā)器）級(jí)聯(lián)組成一個(gè)三進(jìn)制計(jì)數(shù)器和二個(gè)二級(jí)制計(jì)數(shù)器。分頻電路

59、如圖3所示。</p><p>　　圖3 分頻電路原理圖</p><p>　　2.3濾波和調(diào)幅電路設(shè)計(jì)</p><p>　　濾波電路主要完成10KHz方波到10KHz正弦波，30KHz方波到30KHz正弦波的轉(zhuǎn)化。理想方波是包含了所有奇頻分量的信號(hào)，只要通過特定中心頻率的選頻網(wǎng)絡(luò)，很容易得到所需頻率的正弦波。考慮到后級(jí)合成的效果，本系統(tǒng)直接選用了集成的巴特沃斯四階低通

60、開關(guān)電容濾波器TLC04ID，只需合適的選擇該芯片1、2的外接電容電阻就可以確定濾波選頻的中心頻率，計(jì)算公式為f=1/1.69RC。該濾波器的階數(shù)較高，選頻效果好，可以得到相應(yīng)頻率較好的正弦波。</p><p>　　若把10KHz的正弦信號(hào)作為基波，30KHz正弦信號(hào)作為三次諧波，合成一個(gè)10KHz的方波信號(hào)，則由傅里葉級(jí)數(shù)分解可知， 10KHz的正弦信號(hào)和30KHz的正弦信號(hào)的幅度比需要為1:3。由于前級(jí)濾波后

61、兩個(gè)正弦信號(hào)峰峰值均為5V，則需通過調(diào)幅電路把10KHz和30KHz正弦波的峰峰值分別調(diào)為6V和2V。</p><p>　　對于10KHz的正弦信號(hào)，需要從峰峰值5V到6V升壓處理，故選用了同向比例運(yùn)算電路。而對于30KHz的正弦線號(hào)，需要從峰峰值5V到2V的降壓處理，故選用了簡單的電阻分壓電路，而防止后級(jí)電路對電阻網(wǎng)絡(luò)的影響，后面需要加上一個(gè)電壓比較器。在此調(diào)幅的運(yùn)算電路中，由于分頻濾波后的正弦線號(hào)均含有2.5

62、V的直流分量，若直接采用電容耦合隔直效果不好，本文采用了運(yùn)算放大器單電源供電后，在進(jìn)行電容隔直則可以達(dá)到要求，并且信號(hào)的復(fù)擺空間較大。對于單電源供電運(yùn)放，需要在信號(hào)輸入端加上偏壓電路，故采用了電阻偏壓。對于運(yùn)算放大器的選取，這里采用LM358即可滿足要求。處理后即可輸出不含直流分量的10KHz峰峰值6V正弦信號(hào)和30KHz峰峰值2V正弦信號(hào)。10KHz正弦波調(diào)壓電路如圖4所示。</p><p>　　圖4 濾波和調(diào)

63、幅電路</p><p>　　2.4移相和加法電路設(shè)計(jì)</p><p>　　為了加強(qiáng)合成效果，需要對待合成信號(hào)進(jìn)行移相處理。因?yàn)槟M合成信號(hào)只有兩個(gè)，所以只需對其中一個(gè)信號(hào)進(jìn)行調(diào)節(jié)即可。本文設(shè)計(jì)了針對10KHz正弦信號(hào)進(jìn)行相位調(diào)節(jié)的移相電路。由一個(gè)RC網(wǎng)絡(luò)和一個(gè)電壓跟隨器組成，其中RC網(wǎng)絡(luò)中R采用大電阻100K可調(diào)，使得信號(hào)的相位可以在30°~90°范圍內(nèi)調(diào)節(jié)，電壓比較器

64、防止后級(jí)電路對移相電路的干擾。</p><p>　　加法電路即是為了完成最后的信號(hào)合成。由于系統(tǒng)在前級(jí)對信號(hào)的幅度比例已調(diào)節(jié)合適且電路放大運(yùn)算比例固定，不用在加法電路進(jìn)行輸入輸出信號(hào)的幅度調(diào)節(jié)，所以這里采用簡單的單個(gè)集成運(yùn)放LM358構(gòu)成加法電路就可以很好的滿足合成要求。加法電路如圖5所示。</p><p><b>　　圖 5 加法電路</b></p>

65、<p><b>　　2.5測量電路設(shè)計(jì)</b></p><p>　　測量電路是用來測量系統(tǒng)內(nèi)部的所有正弦信號(hào)的有效值，它是獨(dú)立于前面波形發(fā)生合成電路的一個(gè)數(shù)字測量單元。有效值是表征交流信號(hào)幅值的一個(gè)重要參量，對于正弦信號(hào)，其有效值為其峰值的/2，即只要得到正弦波的峰值即可以得到其有效值。因此在系統(tǒng)的測量電路中，先讓正弦信號(hào)通過一個(gè)峰值檢測電路得到其峰值，并且該峰值表現(xiàn)為一個(gè)相對恒定

66、的直流量，再把該直流量通過AD轉(zhuǎn)化為對應(yīng)的數(shù)字量，送入單片機(jī)進(jìn)行處理，即運(yùn)算為信號(hào)的有效值，最后用LCD給以顯示。</p><p>　　對于峰值檢測電路的設(shè)計(jì)，由于正弦波峰峰值均在2~ 6V之間，幅度較大，故直接采用最簡單的一個(gè)二極管和電容串聯(lián)回路，其中二極管起到半波整流作用，而電容則為保持峰值電壓。理想情況下若二極管的導(dǎo)通電壓為0V，則信號(hào)峰值可以精確的表現(xiàn)在電容上，而實(shí)際二極管的導(dǎo)通壓降不可忽略，會(huì)使得實(shí)際峰

67、值電壓等于導(dǎo)通壓降加上原信號(hào)峰值，這也是本測量電路的主要誤差所在，故本測量電路采用以下辦法克服該誤差：（1）選用導(dǎo)通壓降較小的二極管（鍺管，1N5189）；（2）采用軟件補(bǔ)償，減掉二極管的導(dǎo)通壓降。電容選用105的瓷片電容即可。峰值檢查電路如圖6所示。</p><p>　　AD選用了逐次比較型的TLC549，它具有速度較高、功耗低等優(yōu)點(diǎn)，8位的精度足夠滿足本設(shè)計(jì)的測量要求。測量信號(hào)幅度只在1~3V之間，所以測量只

68、需一個(gè)量程（0~5V）即可完成，將TLC549的正向參考電壓輸入端接VCC,將其負(fù)向參考電壓接地即可。單片機(jī)選用了AT89C51，在處理AD轉(zhuǎn)換結(jié)果時(shí)，程序采用了平均濾波算法，這樣可以減小AD轉(zhuǎn)誤差，程序設(shè)定對數(shù)據(jù)保留兩位小數(shù)。最后用LCD SMC162對有效值數(shù)據(jù)給以顯示。</p><p><b>　　圖6 測試電路</b></p><p><b>　　3

69、 系統(tǒng)功能測試</b></p><p>　　系統(tǒng)供電由兩個(gè)電源完成，分別為一個(gè)+5v的單電源和一個(gè)±5V的雙電源。供電參考各模塊電路分析。</p><p>　　由以上各個(gè)功能模塊電路即可完成本系統(tǒng)。其中方波產(chǎn)生電路，產(chǎn)生60KHz，3v的峰值的方波，經(jīng)過分頻電路測得兩個(gè)信號(hào)的頻率分別為30KHz和10KHz，峰值均為5v的方波；在通過低通濾波器得到30KHz和10KH

70、z，峰值均為5v的正弦波；兩個(gè)信號(hào)經(jīng)過調(diào)幅電路處理后幅度分別為30KHz對應(yīng)2V，10KHz對應(yīng)6V；對10KHz進(jìn)行移相電路微調(diào)后，將兩個(gè)信號(hào)送入合成電路，將輸出端用示波器檢查，看觀察到方波波形如圖7。</p><p>　　最后用測量電路測量系統(tǒng)內(nèi)的各級(jí)正弦波，測量誤差可以在5%以內(nèi)。</p><p><b>　　圖7 測試波形</b></p><