一切的變化都是如此的有跡可循，敢于在變化之中尋找確定性，這是就是日蝕公司，為了更好驗(yàn)證自身的發(fā)展，日蝕公司致力于幫助用戶解決在晶體行業(yè)所遇到的問題，并提供完美的貼片石英晶體解決方案，而對于每一款產(chǎn)品的追求更是以精益求精，創(chuàng)新的設(shè)計(jì)理念仔細(xì)研制，在打磨品質(zhì)與性能方面的細(xì)節(jié)，更是超乎于尋常的工藝，使得用戶能夠感到到極致的體驗(yàn)，以及超一流的性能，同時(shí)在日蝕公司還在不斷塑造自身的價(jià)值，也因此吸引更多與之有著相同價(jià)值觀的用戶。

在當(dāng)今世界，快速流暢的數(shù)據(jù)傳輸至關(guān)重要。網(wǎng)絡(luò)和服務(wù)器系統(tǒng)被設(shè)計(jì)成以閃電般的速度處理和轉(zhuǎn)發(fā)信息。為了實(shí)現(xiàn)這一點(diǎn)，許多應(yīng)用依賴于三位數(shù)兆赫茲(MHz)范圍內(nèi)的頻率。

這樣高的頻率是不能用AT晶體的基音產(chǎn)生的。盡管石英盤具有40到50兆赫基頻是可行的它們的生產(chǎn)涉及相當(dāng)大的努力和相應(yīng)的成本。因此，“泛音晶體”通常用于20兆赫以上的頻率。

泛音與基音

每個(gè)石英坯都有其基本頻率。除了這個(gè)“基音”，每個(gè)石英盤還有幾個(gè)泛音。當(dāng)電壓施加在石英上時(shí)，石英以其基本音調(diào)振蕩。它的泛音也在這個(gè)過程中被觸發(fā)，但它們的信號明顯弱于基音。事實(shí)上，在大多數(shù)情況下，泛音信號只會產(chǎn)生正常的相位噪聲。

通過振蕩器電路的巧妙構(gòu)造，可以激勵(lì)石英的泛音而不是基音。因此，為了放大石英的泛音信號，在振蕩器電路中增加了一個(gè)附加的諧振電路。

這項(xiàng)技術(shù)允許工程師從石英晶體中“擠出”遠(yuǎn)高于其基頻的頻率。例如，如果石英以20MHz的基音振蕩，第三泛音以60MHz振蕩，第五泛音以100MHz振蕩。由于振蕩器電路的電子特性，泛音只能在奇數(shù)整數(shù)范圍內(nèi)被激發(fā)。

泛音石英如何振蕩？

剩下的問題是關(guān)于泛音石英振蕩的形狀。你可以把泛音振蕩想象成晶體基波振蕩的倍數(shù)。

厚度剪切振子在其基音中的振蕩

讓我們拿著厚度剪切振蕩器舉個(gè)例子:在電壓下，石英的頂部和底部在基音中向相反的方向移動。但是在泛音中，不僅是石英的上下兩面在振蕩，它內(nèi)部的分子層也在振蕩。這些層也向相反的方向移動，就像水晶在基礎(chǔ)音調(diào)中的頂部和底部一樣。石英晶振不僅在它的外部振動，也可以說“在它自身”振動。

形象地說，人們可以把泛音石英想象成一個(gè)連接在長鏈上的鐘擺。在基音中，只有鐘擺會擺動，但在泛音中，每個(gè)鏈節(jié)也會擺動。

高達(dá)250兆赫的頻率

受泛音驅(qū)動的石英可以產(chǎn)生頻率高達(dá)250MHz，從而為通信技術(shù)中的快速數(shù)據(jù)傳輸創(chuàng)造了完美的基礎(chǔ)。

Such high frequencies cannot be generated with an AT-crystal in the fundamental tone. Although quartz discs with a fundamental frequency of 40 to 50MHz are feasible, their production involves considerable effort and corresponding costs. For this reason, “overtone crystals” are usually used for frequencies above 20 megahertz.

Overtone vs. Fundamental Tone

Every quartz blank has its basic frequency. Besides this “fundamental tone”, each quartz disc has several overtones. When electric voltage is applied to the quartz, it oscillates on its fundamental tone. Its overtones are also triggered in this process, but their signal is significantly weaker than that of the fundamental tone. In fact, most of the time the overtone signal results in nothing more than normal phase noise.

By clever construction of the oscillator circuit, it is possible to actuate the overtone of the quartz instead of the fundamental tone. Therefore, an additional resonant circuit is added to the oscillator circuit in order to amplify the overtone signal of the quartz.

This technique allows engineers to “squeeze” frequencies far above its fundamental tone out of a quartz crystal. For example, if a quartz oscillates in the fundamental tone at 20MHz, the third overtone oscillates at 60MHz and the fifth overtone oscillates at 100MHz. Due to the electronic properties of the oscillator circuit, the overtones can only be stimulated in the odd integer range.

How Does an Overtone Quartz Oscillate?

The remaining question is about the shape of an overtone quartz’s oscillation. You can imagine the overtone oscillation as a multiple of the crystal’s fundamental oscillation.

Let’s take the thickness shear oscillator as an example: Put under voltage, top and bottom of the quartz move in opposite directions in the fundamental tone. However, in the overtone, not only the upper and lower sides of the quartz oscillate, but also the molecular layers inside it. These layers also move in opposite directions, just like the crystal’s top and bottom in the fundamental tone. The quartz does not only vibrate on its outside, but “in itself”, so to speak.

Figuratively speaking, one can visualize an overtone quartz like a pendulum attached to a long chain. In the fundamental tone, only the pendulum swings, but in the overtone each individual chain link swings as well.

Frequencies of up to 250 Megahertz

A quartz driven by its overtone can generate a frequency of up to 250MHz, thus creating the perfect base for fast data transmission in communication technology.