External Broadband Greatly Dither Technology Research In Pipeline Adc

Pipelined ADC has the advantage of high-speed conversion, high accuracy and low power consumption, is widely applied in various occasions, such as wireless communication. Considered various non-ideal factors in ADC, digital calibration is regarded as one of the most important research fields, which can effectively improve ADC’s performance. As one kind of digital calibration technology, Dither is a key technology to improve the performance of ADC.In this paper, the application of Dither technology to improve ADC’s performance is researched, the improvements mainly reflect in three aspects. Firstly, Dither can improve the effective resolution of ADC, which makes the input signal less the1LSB can be distinguished. Secondly, Dither can improve ADC’s SFDR. Dither algorithm is applied to reduce harmonic components in ADC, and then improve the SFDR of ADC. Thirdly, Dither can improve the total DNL error of ADC.A validation scheme for Dither algorithm and four modules for digital processing on the FPGA in the validation scheme are designed, such as a wideband and large amplitude Dither generator module, a PN sequence code delay module, a digital subtracter module and a digital filter module.A12bits pipelined ADC error model as a target ADC model is built in Matlab/Simulink. Then a wideband and large amplitude Dither structure is built and simulated on this target ADC model. The result shows that ADC’s SFDR improving form76.79dB to82.07dB and ADC’s SNR reducing1.6dB, which verifies the Dither technology can improve the SFDR of ADC and reduce SNR. At the same time three shortcomings are finded in this structure, such as the Dither amplitude defect, the DAC demanding defect and the PN sequence code removal defect. A self-adapting Dither structure dependent on the input signal amplitude is proposed based on the shortcoming of Dither amplitude defect, which shows that ADC’s SFDR improving from76.79dB to88.08dB and SNR reducing0.36dB. Then a self-adapting storage type Dither structure is proposed to solve other shortcomings, which shows that ADC’s SFDR improving from76.79dB to91.72dB and SNR reducing0.11dB.The results confirm the self-adapting storage type Dither structure is more advantage in improving ADC’s SFDR and reducing the effect of added Dither signal to ADC’s SNR.