Dither In The Adc In The Research And Application

All the signals in the environment are the analog one; however, the signals which computer can process are the digital one. The analog signals can be converted to digital one by ADC easily, achieving the signals'quantized. At present, the voice of SDR(Software Defined Radio) is becoming louder and louder. SDR uses ADC and DAC as the interface between the analog signals and digital signals,thanks to them, the RF signals can be directly sampled or reconstructed, they must have very high speed for the rate of AD converting,besides, in order to reduce the interference to other channel by the harmonic, the ADC's dynamic performance must be very good. The paper focuses on reducing the harmonic in the spectrum by dither, which is to increase the ADC's dynamic performance(SFDR).Dither has been used in digital image's display for over 60 years, the edge effect in the digital image's display can be eliminated by adding dither, and in addition, dither also can improve the expressiveness of graphic color. Adding dither in the sampled audio can reduce the audio's quantized error, making the digital audio sounds more comfortable when replayed. Dither is also used in the field of measurement widely. The paper first introduces the principle of the ADC and the main type of ADC at present, and then introduces the behavioral model of 12bit pipeline ADC in Simulink, at last introduce the main performance index of ADC.In the part of dither principle, firstly, the paper introduces the history of dither, secondly, the paper introduces the error which results in decreasing the dynamic performance of the ADC, besides discuss the principle which is reducing the error and increasing the ADC's performance by dither. At last makes a simulation of the two main type dither structure in Simulink,besides developes a new structure of wide band dither.In the part of dither's generation, the paper first introduces the circuit of all kind of dither's generation; design the PN(pseudo number) sequence generation circuit for wideband dither. Then the paper develops a new narrow band dither structure based on digital wave memorized; and finishes the digital wave's initialization in quartus. At last the paper introduces the design of the circuit board for dither's verifying, the circuit board can be used to verify the main type of dither. The paper finished the circuit board's testing and debugging. At last the paper verifies the wide band dither and narrow band dither in the real circuit board.