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微波技術
高頻PCB板特性和阻抗控制
微波技術
高頻PCB板特性和阻抗控制

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=√(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=√(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.

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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”.

5. Radio Frequency Interference (RFI) radio frequency interference
It is an unexpected and undesirable interference, including the appearance of some undesirable transients (Transients) signals, 干擾電子通信設備或其他電子機器的運行,影響其正常功能. 例如, 在早期沒有RFI保護的電視中, 當一輛脚踏機車在附近啟動時, the sparks (Spark) electromagnetic waves emitted by the spark plugs would cause temporary chaos in the picture after being transmitted to the TV. 如果電視塑膠外殼的內壁用含銅或鎳的化學塗料處理, 遮罩層可用於將電磁波導引導至“接地層”,以减少RFI干擾. 至於一些“高頻”焊接車間, 還必須用金屬網將其建築物接地,以避免周圍電子設備發出的高頻電磁波的干擾. 機場通道附近的操作員甚至可能對飛機著陸雷達儀器造成干擾, 對飛行安全構成極大威脅,必須嚴加防範.

6. Reflection
In common sense, 這意味著鏡子反射入射光. 然而, 當高速訊號在電腦主機板中傳播時, 這意味著“訊號”由駕駛員通過訊號線發送,並在接收器上廣播. 如果三者的阻抗值可以匹配, 訊號的能量可以順利到達接收器. 一旦訊號線的質量出現問題, 這會導致“特性阻抗”值超過極限, 這將導致部分訊號能量折回到駕駛員身上, 也被稱為“反射”.

7. Rise Time
This word is an important property of square wave logic signal (Signal) or pulse (Pulse). The "clock" (clock pulse) system composed of the ordinate as the voltage (such as 5V in the early days and 3.現在是3V, 可能還有2個.5V in the future), 橫坐標表示時間; 方波在理論上的傳播, 它應該從低狀態垂直上升到“高狀態”, 但事實上,它是以一定的坡度上升的. 將坡度從10%升高到90%高度所需的時間稱為上升時間, 公共組織是10-9秒, 縮寫為NS, 翻譯為納秒.

8. Ultra High Frequency (UHF)
Refers to the "ultra ultrashort wave" with a frequency between 300MHz and 3GHz or a wavelength between 1 m and 10 cm, 這被稱為UHF. 比如電視, 車載電話, 老大哥手機, 等. 屬於這個範圍, 其中使用的電路板FR-4仍能完成任務. 至於頻率更高的微波電子產品, 聚四氟乙烯PCB are required (see the special article of the 50th issue of the Circuit Board Information Magazine for details). 電磁干擾; 射頻電磁干擾; 無線電波, radio frequency RFI Radio-Frequency Interference; radio frequency interference SHF Super High Frequency; The big brother of wireless or satellite communication) UHF Ultra-High Frequency; Ultra-high frequency electromagnetic waves refer to radio waves with a frequency between 300 and 3,000兆赫, or "ultra ultra short waves" with a wavelength between 1 and 10 dm (10 to 100 cm). 它們是常用於高清影像顯示電視. VHF Very High Frequency; Very high frequency electromagnetic waves (ie ultrashort waves) refer to radio waves with a frequency between 30 and 300 MHz, 波長在1到10米之間, 用於廣播和電視.