【正文】 signal in frequency 10KHz above all, if digital devices is easy to cause the conversion rate is too low counter can not work normally, the output signal distortion, so this paper chose conversion rate faster TTL devices. Final determination by two 74LS109 (double integration JK flipflop) cascade form a ternary counter and two secondary system counter. Points frequency circuit shows. Figure 3 points frequency circuit principle diagram filter and modulation circuit design Filter circuit 10KHz mainly pletes 10KHz sine wave, 30KHz square to the transformation of 30KHz sine pulse to. Ideal square wave is contains all the odd frequency ponents, as long as the signal through specific center frequency of frequency selective work, very easy to obtain the required frequency sine wave. Considering the effect of grade synthetic after, this system directly choose the integrated bart hepworth fourthorder lowpass filter, simply switched capacitor TLC04ID appropriate choices the chip 1, 2 wide capacitance resistance can determine the filtering frequency selective of center frequency, formulas for the f = 1/ RC. This filter order number is higher, frequency selective effect is good, can get the corresponding frequency better sine wave. If the yankees 10KHz sinusoidal signal as 30KHz sine wave, three times as a signal of harmonic, U 1 AJK 觸發(fā)器1J1~1Q21CLK121K4~1CLR131Q3123二分頻U 2 AJK 觸發(fā)器1J1~1Q21CLK121K4~1CLR131Q3U 3 AJK 觸發(fā)器1J1~1Q21CLK121K4~1CLR131Q3UiUo45678191Ui三分頻Uosynthetic a 10KHz by square wave signal, then Fourier deposition knowable, 30KHz 10KHz sinusoidal signal 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 in fengfeng value for adjustment and 2V. For the sine signals, need 10KHz from fengfeng value 5V 6V, so to boost processing operation circuit whetherisolated selects the proportion. And for 30KHz sinusoidal 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 work level circuit influence, plus a voltage behind need parators. The operation circuit in the attenuation, because the sine separate frequency filtering line number after all contains V dc ponent, if direct capacitive coupling effect by every straight, this paper adopts the bad amplifier single power supply in isolation, after can be reached capacitance straight requirements and the large pendulum space signal. For single power supply amp, need in signal input plus bias circuits, the resistance bias is adopted. For the selection of operational amplifiers, it is LM358 can meet the requirements. Treatment can output excluding dc ponent 10KHz fengfeng value of 30KHz 6V sine signals and 2V sine signals in fengfeng value. As shown in figure 4 10KHz sinusoidal voltage regulation circuit shown. Figure 4 filter and modulation circuit move and addition circuit design 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 signal can be adjusted. This paper introduces the design of 10KHz sine signals in the phase adjuster phase shifting circuit. By a RC work and a voltage followed sensor into the RC work, including by large resistance (R 100K adjustable, makes the signal phase in 30 176。 range adjustment, voltage parator to prevent the latter stage of the phase shifting circuit circuit interference. Addition to finish last is that the circuit of signal synthesis. Because the system 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 simplicity of a single integrated amp LM358 constitute addition circuit can well satisfy synthetic requirements. As shown in figure 5 shows addit