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一个系统的互调失真常常用它的三阶截取值来表示,其是最广泛地用来表明系统线性的品质因子。即使低信号电平加到被测器件,要想准确地和重复地测量互调失真也是相当困难的,而电平在需要的载波(输入信号)以下100db 时,可以做到精确的测量。若在测量系统中附加一个可调谐的带通滤波器和减少测量系统的固有非线性,测定高达+50dbm 的三阶截取值是可能的,比现在使用中的大多数系统大约高20db。
A systematic intermodulation distortion is often expressed by its third-order intercept value, which is the most widely used quality factor to indicate systematic linearity. Even if the low signal level is applied to the device under test, it can be quite difficult to accurately and repeatedly measure intermodulation distortion, and the level can be accurately measured at 100db below the required carrier (input signal). Measuring the system with a tunable band-pass filter and reducing the inherent non-linearity of the measurement system makes it possible to measure third order intercepts of up to +50 dBm, about 20 dB above most systems in use today.