For wireless digital communications, digital user signal is usually at first converted into analog domain and then modulated to radio frequency by one or two steps.
The fault is diagnosed by extracting the fault feature component from the frequency spectrum of the modulatedsignal.
通过对调制信号作谱分析,以其频谱中是否存在某种故障的特征频率分量来诊断有无该种故障。
3
A modulated high-frequencysignal is distorted by the thermal behaviour through complex intermodulation phenomena, although the temperature response of the circuit is slow.