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# 高頻PCB板特性和阻抗控制

2021-11-29
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Author：iPCBer

1. AC Impedance AC impedance
AC resistance (Resistance; R), capacitive reactance (CapaciTIve Reactance; Xc), and inductance (InducTIve Reactance; XL) are combined into AC "resistance", referred to as "impedance" (Impedance, representing symbol Z) . The formula is Z=â(R2+(XL-XC)2). This word is related to the signal in high-speed or high-frequency transmission lines (Signal; this word still has other synonyms such as Pulse, 方波, 步進波, 等.). "Charac terisTIc Impedance" (Charac terisTIc Impedance), Its representative symbol is Zo) is completely different from the former, and its formula is Zo=â(L/C). 原來單詞中的AC指的是交流電, 這就是“極性交換電流”. 就是, 隨時間變化的電流, 縮寫為AC. This AC symbol is often used for power supplies that change polarity (Polarity Switching) many times per second, 它的波形通常是正弦波, 方波, 還是三角波.

2. Characteristic Impedance
It means that when there is an electronic "signal" waveform in the conductor, 其電壓與電流之比稱為“阻抗”. Because the "Resistance" that has been mixed with other factors (such as capacitive reactance, 感應電抗, 等.) in an AC circuit or at high frequencies is no longer just a simple direct current "Ohmic Resistance" (Ohmic Resistance), 囙此，在電路中，它不應再被稱為“電阻”, 但應該被稱為“阻抗”. 然而, 說到交流阻抗的實際使用, 這將不可避免地引起混亂. 為了與眾不同, 電子訊號必須稱為“特性阻抗”. 當電路板線路中的訊號傳播時, 影響其“特性阻抗”的因素是線路的橫截面積, 線與地面層之間的綠色資料厚度, 以及它的介電常數. 現時, 有許多板具有高頻率和高傳送速率, 而“特性阻抗”必須控制在一定範圍內. 在電路板的製造過程中, 必須仔細考慮上述三個重要參數和其他合作條件.

3. Frequency
Refers to various periodic motions, 就組織時間內的重複次數而言. Electric frequency is usually in units of "Herz" (Herz, the number of repetitions per second or number of cycles). 電路板電路中的“訊號”以波動的管道傳輸, 所以高頻率是高速運轉的必要條件. 高頻, 薄板的介電常數非常關鍵. 例如, 用於3 GHz以上的高頻微波通信板, 介電常數為4的FR-4.5必須更換為只有2個.6.减少訊號損耗和延遲.

4. Impedance Match impedance matching
If a signal (Signal) is being transmitted in the electronic circuit, it is hoped that it can be transmitted to the receiving end (Load) smoothly from the source of the power source with the least energy loss. 它完全被接收端吸收，沒有任何反射. 為了達到這種良好的傳播或傳播, the impedance (ZL) in the circuit must be equal to the impedance (Zo) inside the "transmitting end", 這叫做“阻抗匹配”.