什麼是定向耦合器? What is Directional Coupler?

定向耦合器是一種測量元件,可插入 RF 來源 (如訊號產生器、向量網路分析器或發射器) 和負載之間的傳輸線中。此元件可測量從來源至負載的 RF 功率,以及從負載反射回來源的功率。可計算負載的總功率、回波損耗和駐波比。

Directional coupler is a type of measuring device that can be inserted into the transmission line between an RF source (such as a Signal Generator, Vector Network Analyzer, or Transmitter) and a load. This device can measure the RF power from the source to the load, and the power reflected from the load back to the source. It can calculate the total power at the load, return loss, and voltage standing wave ratio (VSWR).

 

定向耦合器規格Directional Coupler Specifications

 

定向耦合器有幾個關鍵特性,包括頻寬、額定輸入功率、插入損耗、頻率平坦度、耦合係數、方向性、隔離度以及殘留電壓駐波比 (VSWR)。
Directional couplers have several key characteristics, including bandwidth, rated input power, insertion loss, frequency flatness, coupling coefficient, directivity, isolation, and residual voltage standing wave ratio (VSWR).

 

  • 頻寬:耦合器的頻寬代表頻率範圍,以 Hz 為單位。在此範圍內,耦合器將按其規格工作。
    Bandwidth: The bandwidth of a coupler represents the frequency range in hertz (Hz) over which the coupler will operate according to its specifications.
  • 額定輸入功率:對於連續波 (CW) 和脈衝輸入訊號,耦合器具有最大輸入功率額定值,以 W 為單位。     此為元件在不會造成性能劣化或實體損壞下,可以處理的最大功率。
    Rated Input Power: For continuous wave (CW) and pulsed input signals, the coupler has a maximum input power rating in watts (W). This is the maximum power the device can handle without degradation of performance or physical damage.
  • 插入損耗:代表因元件插入主傳輸路徑而引起的功率損耗,以 dB 為單位。
    Insertion Loss: It represents the power loss caused by the insertion of the device into the main transmission path, measured in decibels (dB).
  • 頻率平坦度:頻率平坦度指定在元件額定頻寬範圍內,主傳輸路徑的振幅回應變化 (以 dB 為單位),此變化取決於輸入訊號的頻率變化。
    Frequency Flatness: In the amplitude response variation in dB within the rated bandwidth of the device, depending on the frequency variation of the input signal.
  • 耦合係數或耦合因數:耦合係數是指耦合器在所有埠都正確端接時,輸入功率與耦合埠功率的比值,以 dB 為單位。耦合埠的輸出與輸入至輸出這條直接路徑的功率位準呈正比,而比例值則為此已知因數。耦合輸出可連接到示波器等其他儀器,且不會讓儀器有過載危險。
    Coupling Coefficient: The coupling coefficient refers to the ratio of input power to coupled port power when all ports of the coupler are properly terminated, measured in dB. The output of the coupled port is proportional to the input to output power on the direct path, and the proportionality value is this known factor. The coupled output can be connected to other oscilloscopes without overload.
  • 隔離度:當所有埠都正確端接時,輸入埠功率與隔離埠功率的比值,以 dB 為單位。
    Isolation: The ratio of input port power to isolation port power when all ports are correctly terminated, measured in dB.
  • 方向性:當所有埠都正確端接時,耦合埠功率與隔離埠功率的比值,以 dB 為單位。對於三埠型耦合器,將進行兩次功率測量,一次是在常規的前向方向,另一次則是在輸入和輸出埠反轉的情況下。此規格用於測量前向分量與反射分量的分離程度;一般來說,方向性越高,耦合器效能便越好。方向性無法直接測量,但可根據隔離和反轉隔離的測量值計算出來。
    Directivity: The ratio of coupled port power to isolation port power when all ports are correctly terminated, measured in dB. For a three-port directional coupler, power measurements are made twice: once in the conventional forward direction and once with the input and output ports reversed. This specification is used to measure the degree of separation between the forward and reverse components; Generally, the higher directivity, the better performance of the coupler. Directivity cannot be measured directly, but it can be calculated based on the measured values of isolation and reverse isolation.
  • 殘留 VSWR:在耦合器的所有埠都正確端接時,所測得的駐波比。這可用於測量耦合器固有的阻抗匹配。
    Residual VSWR: The standing wave ratio measured when all ports of the coupler are correctly terminated. This can be used to measure the inherent impedance matching of the coupler.

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