外文翻譯----數(shù)據(jù)采集同步濾波器在鎖定放大器中的應(yīng)用-其他專業(yè)-資料下載頁
2025-01-19 09:11本頁面
【導(dǎo)讀】也很小，并且對濾波器的性能的要求也比較靈活。通過鎖定放大器噪聲中的微小信號。能夠準確的檢測出來，而不像在傳統(tǒng)鎖定放大器需要通過繁瑣的相位調(diào)整。鎖定放大器運用了相敏檢測器和低通濾波器，不僅提供了對頻率的高選擇性，而且即使在中心頻率，也有一個拒絕相外噪聲性能。在測量相位和分布求積分中，相。敏檢測是不可或缺的。參數(shù)的變化使相位發(fā)生漂移，例如一個濾波網(wǎng)絡(luò)檢測它的頻率響應(yīng)。在許多鎖定放大器中相位靈敏調(diào)解器被設(shè)置是為模擬開關(guān)式相。就能夠避免誤差。一個調(diào)諧濾波器，經(jīng)常用來做為預(yù)濾波，然而相頻檢測依賴于通頻。帶，在PSD輸出信號的微小變化就會引起大量的誤差。于PSD相比，新式的鎖定放。起工作時，預(yù)濾波必須被省卻或者通頻帶必須被展寬以免限制掃描范圍。限制相聯(lián)系，同步濾波器只提取方波信號中的基波成分。參考通道由方波發(fā)生電路和移相電路組成,其作用是提供一個與輸。，由觸發(fā)電路將其變換成為規(guī)則的同步脈沖波。
【正文】 with a sweeping external reference signal, a prefilter must be dispensed with or its passband has to be widened in order not to restrict the sweep range. In such a case the lockin amplifier using the synchronous filter can measure a loulevel signal affected by noises and by the harmonics with less error than a usual lockin amplifier owing to the smaller harmonic responses. （ 2） Reference channel The synchronous filter requires such 6phase drive signals as shown in figure 2. The signals can be easily produced by a 6bit ring counter working at the clock frequency of 6 fc. In the internal mode operation, a variable voltage source E, supplies the control voltage of vco (voltage controlled oscillator) to generate the clock signal. Two outputs $1 and $4 of the ring counter let an RS flipflop set and reset respectively to form a square wave offc. This square wave is applied to the following synchronous filter of the same type as in the signal channel. Associating with the band restriction of a lowpass filter (LPF l), the synchronous filter picks only the fundamental ponent out of the square wave. The sinusoidal wave of fc obtained is employed as a reference output signal. Cutoff frequencies of the lowpass filter and the prefilter in the signal channel are set by means of the same front panel dial in conjunction with the setting of E.
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