Some of the most important antenna parameters are return loss, S11, and VSWR.

一些最重要的天線參數包括回波損耗、S11 和駐波比。

All of these are connected to one another, but let's have a first look at each of them separately.

所有這些都是相互關聯的，但讓我們先分別看看它們。

VSWR stands for Voltage Standing Wave Ratio.

VSWR 代表電壓駐波比。

If the impedance of an antenna and the cable are different, part of the feeding signal is reflected back.

如果天線和電纜的阻抗不同，部分饋電信號就會反射回來。

The reflected signal adds up with the feeding signal into a single wave called a standing wave.

反射信號與饋電信號疊加成一個波，稱為駐波。

The ratio of maximum and minimum value of the standing wave is VSWR.

駐波的最大值和最小值之比就是駐波比。

Ideally, VSWR is 1 to 1, which means the impedance of the antenna and the cable are exactly equal.

理想情況下，駐波比為 1 比 1，即天線和電纜的阻抗完全相等。

In the real world, the VSWR is for example 2 to 1, meaning there is a mismatch and some of the input signal is reflected back.

在現實世界中，駐波比是 2 比 1，這意味著存在失配，部分輸入信號會被反射回來。

If it's 3 to 1, there is an even bigger mismatch, and so on.

如果是 3 比 1，則不匹配程度更高，依此類推。

Return loss tells us what portion of the input power is reflected from the antenna due to the mismatch.

回波損耗告訴我們，由於失配，有多少輸入功率從天線反射出去。

For example, if return loss is 30 dB, it means the reflected signal is 30 dB weaker than the input signal.

例如，如果回波損耗為 30 dB，則表示反射信號比輸入信號弱 30 dB。

S11, also known as the reflection coefficient, is the ratio of the voltage wave reflected from the antenna port to the input voltage wave.

S11 也稱為反射係數，是從天線端口反射的電壓波與輸入電壓波的比值。

Ideally, S11 is as close to minus infinity as possible.

理想情況下，S11 儘可能接近負無窮大。

In reality, minus 20 dB is considered a very good S11.

實際上，負 20 dB 已被認為是非常好的 S11。

Minus 10 dB is a standard adopted by many RF engineers as an acceptable limit of good matching.

最小 10 dB 是許多射頻工程師採用的標準，作為良好匹配的可接受極限。

Anything above minus 10 dB is usually considered mismatched.

超過負 10 dB 通常被認為是不匹配。

These parameters relate to each other through simple equations.

這些參數通過簡單的方程式相互關聯。

S11 can be described in terms of VSWR and vice versa.

S11 可以用駐波比來描述，反之亦然。

The return loss is equal to minus S11.

回波損耗等於減去 S11。

The impedance of the antenna and the cable are never exactly equal, and it only depends on the real world application how much of a reflection is acceptable.

天線和電纜的阻抗永遠不會完全相等，只能根據實際應用情況來確定可接受的反射程度。

In the world of RF engineering, the unwritten standard of good matching is S11 equal to minus 10 dB, in other words, the VSWR of 2.

在射頻工程領域，良好匹配的不成文標準是 S11 等於負 10 dB，即駐波比為 2。

More serious manufacturers, though, have often better standards to deliver high quality products.

不過，更嚴肅的製造商往往有更好的標準來提供高質量的產品。

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