Research Of Digital Up-Converter Of Radio

Wireless Communication is widely used in commerce, military and civilian. With the development of modern communication technology, more and more communication systems are applied to practice. And more new communication standards are there, In order to use some old standards, and to make them compatible with each other, we need Soft Defined Radio(SDR). And SDR can also be use to such as CATV.There are many type of modulation of wireless communication, such as AM,FM,BPSK,QPSK,MPSK,QAM. For the purpose of SDR theory , we need a general modulation algorithm to these modulation type. On the principle of orthogonal transform, we can find a method to attain the aim. Based this we design a general modulation model.Quadrature Digital Upconverter(DUC) is the base components of SDR transmitter.It can bring the baseband signal upto the high frequency. This paper design an DUC base on CORDIC algorithm. We use modified CORDIC algorithm to generate quadrature carrier frequency.A substaintial of DUC is lowpass filter. For the purpose of baseband signal matching up the carrier signal, the baseband signal need interpolation. we designed a cascaded integrator-comb(CIC) filter. So the baseband signal can match up the carrier signal. It can supply the demand of Nyquiest sample theory.Another important compenent of the DUC is the numeric controlled oscitrolled(NCO).This paper analyzed the technology of direct digital synthesis(DDS) based on lookup table(LUT). The DDS need a rom LUT to store the Sin. There exists exponential relationship between the ROM and the precision. If it needs good precision, that it needs a large ROM. So this paper designed a CORDIC algorithm to replace the ROM LUT structre. The CORDIC algorithm can realize the high degree accuracy of Sin, that may not make the resource big. But the CORDIC algorithm also have some shortcoming. The first it can't cover the range of 0~2π. The second the speed is limited. We modified the CORDIC algorithm to get over these shortcoming. We let the angle in the range of 0~π/4, later we can recover all Sin according to the character of Sin. The other we can design a method to bring forward the rotation direction , so we need not calculate the direction every time. It can save many times. At the same time , can make the last stages pipeline into one stage, it can also save time.At last, this scheme is designed and simulated on FPGA.