The Research And Implementation Of Automatic Test System Of Spectrum Analyzer Based On GPIB Bus

Spectrum analyzer is an instrument that measures the input signal spectrum(amplitude-frequency relationship)over a range of frequencies.Its main role is to measure the power spectrum of the signal.The input signal of the spectrum analyzer is an electrical signal.By analyzing the input electrical signal,the main frequency,power,distortion,harmonics,bandwidth and other spectral components of the signal can be observed in the displayed spectrum.These parameters are not easy to detect in the time domain analysis.But they are very useful when describing electronic devices such as wireless transmitters and analyzing the characteristics of complex space electromagnetic environments.Many spectrum analyzers have problems such as component aging and temperature drift during use.The performance of the instrument is degraded and a series of measurement problems may occur,such as inaccurate measurement parameters or signal waveform distortion.Many foreign instrument manufacturers have begun to reasearch the automatic calibration system of such instruments,use real-time calibration of the instrument to ensure the accuracy of the measurement to reduce the above situation.Domestic instrument manufacturers are seldom engaged in related work,and there are relatively few studies on automatic calibration systems.In such environment,this paper conducts an automatic calibration research of the spectrum analyzer,it designs and implements a spectrum analyzer automatic calibration system for daily calibration in the Delphi environment through the GPIB bus.The main content of the article is divided into two parts: the first part is the research on the automatic calibration method of spectrum analyzer;the second part is to design and implement a spectrum analyzer automatic calibration system written by Delphi,and verify the calibration result and analysis system uncertainty.In the first part,this paper designed several calibration methods for the main calibration parameters according to JJF 1396-2013 spectrum analyzer calibration specification,which mainly involves the following parameters: frequency reading,resolution bandwidth,absolute amplitude,input Frequency response,display average noise level,etc.The content of the system software in the second part is mainly divided into four parts: instrument control,data acquisition and processing,implementation of calibration method and user interface.Among them,the instrument control mainly uses the GPIB bus to realize the computer control of the signal source,power meter,frequency meter and spectrum analyzer.The main content of data acquisition and processing is the collection and preservation of calibration data.The software implementation of the calibration method is the core of this paper,mainly through the software function module of the above calibration method to obtain the required calibration data.The main content of the user interface is to implement the automatic calibration system operation interface and display the calibration results.Finally,the calibration results were verified and the uncertainty of the system was analyzed.The system is currently in use and can quickly and accurately calibrate the spectrum analyzer.