Spectrum analyzer is a device for studying the spectrum structure of electrical signals.The modern analytical instruments usually use function generators.It is used for measuring signal parameters such as signal distortion, modulation, spectrum purity, frequency stability and crosstalk, and can be used to measure some of the circuit systems such as amplifiers and filters Parameter, is a versatile electronic measuring instrument. It can be called frequency domain oscilloscope,the name is a little similar with the Universal Frequency Counter. tracking oscilloscope, analysis oscilloscope, harmonic analyzer, frequency analyzer or Fourier analyzer. Modern Spectrum Analyzers display the results of an analysis either analogue or numerically and analyze the electrical signals of all radio bands from very low to sub-millimeter bands below 1 Hz. If the inside structure use digital circuits and microprocessors, with storage and computing functions; configure the standard interface, it is easy to form automatic test system.