The structure of spectrum analyzer seems like the oscilloscope which is used for the time domain. There are many function control buttons on the board of the spectrum analyzer. As the adjustment and control of the system control, there are real time spectrum analyzer and scan tune spectrum analyzer. The function of the real time spectrum analyzer is to show the signal amplitude of the frequency domain at the same time. Its working time is as to different frequency signal there are different filters, then send the signal to the CRT screen through the multitask scanning machine. The advantages is that it can show the moment reaction, while the disadvantages is the high cost and the performance is limited by the frequency wide range.