The Design Of TD-SCDMA Baseband Signal Generator Using The Digital Intermediate Frequence Technology

At present, TD-SCDMA has been into the commercialization massively, and its evolution versionTD-LTE has been involved into the testing stage in some cities. TD-SCDMA and TD-LTE base stationprocess the baseband signal transmitted from the remote module. Meanwhile a large number of signal sourcesare needed for communication equipment in developing, research and testing process. However, the price ofbaseband signal sources is expensive in the market and they also exhibit some limitations. So, studies ofTD-SCDMA baseband signal source design have certain practical significance.First, a noise model is designed, this model can avoid adding noise repeatedly. We adopt two ways toverify the feasibility of the model design. In view of the defects of the2-D radio channel model, byintroducing a nonzero elevation angle of the arriving wave on the basis of plane azimuthal angle, we model3-D wireless downlink channel using the autoregressive filter technology, and study the statistical properties ofthe channel. Then, fading channel model is achieved in ADS software and downlink channel physical signal isgenerated. And then analyse the generation method of intermediate frequency and generate fading IF signal.Moreover, this thesis gives the framework of the overall design of digital down conversion with AD6654core signal processor. And studies the circuit schematic design of the various hardware modules in detail,including clock circuit design, analog-to-digital converter (ADC) design, the digital down conversion (DDC)design, the control circuit design, power circuit design and so on, then analyses some common problems ofsignal integrity, such as reflection, crosstalk, and gives some improvements. And then, designs the PCB withthe use of Cadence Allegro, laminated design, PCB layout design, power/gnd design and layout design areincluded, among them we especially focus on difference line wiring. And then carry out a detailed analysis anddiscussion of the above design.Finally, we use simulation software SigXplorer of Cadence and ADS software to simulate the key clockline and the data line on the PCB, and use Siwave software to simulate the power integrity of the PCB. PCBlayout is modified by the result of simulation, ensuring the signal integrity and power integrity of the keynetwork.