Design And Application Of Virtual Spectrum Analysis System Based On LabVIEW

In recent years, withthe development of digital signal processing, the technology is widely applied to communications, computer, aerospace, medical and other fields.The accuracy of signal processing is also higher and higher. In particular the weak signal detection has been one of advanced measurement technology and comprehensive field.Therefore, the birth of high precision low noise spectrum analyzer arises at the historic moment.A bite data,applied to flow of signal processing of simple structure, low interference, high processing speed(use unit operation circuit, such as the adder, multiplier, etc.), can improve the resolution of spectrum analyzer.Firstly,this article introduces the?Σmodulation principle of single bit modulator, ?Σmodulator in adopting the oversampling and noise shaping technology. This can makethe satisfyabout the requirements of high measurement precision.Then this article introduces the NI PXI- 5922 card and the LabVIEW platform. They arethe spectrum analysis system’s software and hardware parts.NI PXI- 5922 card uses a single bit(single- bite) ?Σanalog/digital converter(ADC). It provide high resolution and wide dynamic range for low frequency applications.LabVIEW platform uses the graphical editing language to write the program(we call it G language). The program is in the form of block diagram.The design of the front panel is more humanized, and make stronger maneuverability.In order to verify the accuracy of this system, this paper presents the corresponding waveform simulation results of time domain and frequency domain.When the system processesthe weak signal, its noise of the measuring instrument limit must be lower than the measured output noise of the circuit.The test circuit can be reflected in the measurement of the output noise.The spectrum analysis system’sbackground noise is only 10 nv/rt- Hz. It’s much lower than the common signal processor, so the measurement of weak signal can be more accurate.Then we use the spectrum analyzer to measure the 100 Ω resistor thermal noise and gain 115 OPA627 noise background.Their noise spectrum density is under under1.283 nV/rt-Hz and 1.34 respectively nV/rt-Hz.