Design And Verification Of Cascaded Delta-sigma Modulator In Digital Transmitter

With the rapid development of wireless communication technology,wireless communication devices have begun to trend toward miniaturization,integration,and low power consumption.Compared with traditional analog transmitters,digital transmitters have the advantages of flexible configuration,reconfiguration,high integration,high efficiency,and low power consumption.Therefore,digital transmitters are one of the trends of wireless transmitter systems in the future.To improve the ACLR of digital transmitters,the usual approach is to increase the oversampling rate OSR,or to increase the number of levels,using a multi-level scheme.The thesis researches the existing digital transmitter with delta-sigma structure and designs the cascade delta-sigma modulator.The main work of the thesis is as follows:First,introduce the existing digital radio frequency transmitter structure,analyze the advantages and disadvantages of these digital transmitters,and introduce the principle of delta-sigma and several delta-sigma structures.This is the delta-sigma structure introduced in this article.The scheme design provides reference.Secondly,research and design and MATLAB simulation of cascaded low-pass delta-sigma structure and cascaded band-pass delta-sigma structure respectively.For the design of the cascaded low-pass delta-sigma structure,the first stage selects tunable delta-sigma modulation,a completely parallel delta-sigma structure,and the second stage uses a look-up table instead of delta-sigma modulation to achieve higher ACLR.The cascaded band-pass delta-sigma structure optimizes the tunable delta-sigma modulation.At the same time,the first and second stages use a completely parallel delta-sigma modulation structure.MATLAB simulation of low-pass and band-pass structures.Third,FPGA implementation and testing of two low-pass band-pass structures.The design of the two structures is combined to implement the hardware,and the structure of some of the main units is introduced in detail,and the main experimental results are described.In summary,the paper designs cascaded low-pass and band-pass delta-sigma structures,and tests and verifies them to achieve a higher ACLR.