Fast Fourier transform (FFT) broadband frequency spectrometer design based on AD9864 medium frequency digitization system

Abstract

The invention discloses a fast Fourier transform (FFT) broadband frequency spectrometer based on an AD9864 medium frequency digitization system. After passing an attenuator and a radio frequency switch, a radio frequency input signal is processed through four different channels set according to different measure frequencies. When frequency is smaller than 10MHZz, the radio frequency input signal is directly sampled by AD, frequency measurement is achieved through the FFT, and when the frequency is larger than or equal to 10MHz and smaller than or equal to 4400MHz, the radio frequency input signal is processed through once frequency conversion and the AD9864 and follow-up processing is conducted through a personal computer (PC). The design scheme simultaneously considers user requirements for measurement with large scanning width and high speed, detection is directly conducted and an amplitude value of the input signal is obtained without processing of the AD9864, and therefore the measurement with the large scanning width and the high speed can be rapidly completed. According to the FFT broadband frequency spectrometer based on the AD9864 medium frequency digitization system, the once frequency conversion manner is used for replacing an traditional three-time frequency conversion manner, the PC resources are sufficiently used for replacing requirements of traditional frequency spectrometer for a central processing unit (CPU) with high properties in a medium processing process. Compared with a traditional frequency spectrometer with high properties, the FFT broadband frequency spectrometer based on the AD9864 medium frequency digitization system is simple in design, small in achieving difficulty, low in power consumption and great in reducing user measurement cost.

Description

technical field [0001] The invention relates to a frequency conversion mode, a method for realizing the design of a broadband spectrum analyzer based on an integrated digital chip and using an FFT mode. Background technique [0002] The current sweep spectrum measurement generally adopts the superheterodyne method to down-convert the input signal, so as to analyze and process the signal at a fixed intermediate frequency. Such as figure 1 As shown, due to the existence of the image frequency, three frequency conversions are generally used to convert to a fixed intermediate frequency for processing; this method has high requirements for the frequency resolution and spectrum index of the first local oscillator, and it is easy to have multiple local oscillators in the system. Intermodulation signals are generated, so its cost is high and its structure is complex. Contents of the invention [0003] The purpose of the present invention is based on the AD9864 intermediate f...

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Problems solved by technology

like figure 1 As shown, due to the existence of the image frequency, three frequency conversions are generally used to convert to a fixed intermediate frequency for processing; this method has high requirements for the

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