is filtered and then interpolated to the noise, signals and spurious. By doing so, all of the wide- desired data rate. Then, the data is translated to the band noise on the output of the ADC is removed except proper frequency using a modulator and complex NCO. that which lies within the passband of the filter, giving For a typical RSP/TSP channel, the computational rise to what is often referred to as processing gain. load may be as high as 1.5 Giga-operations per second. If Second, the filter shapes the passband characteristics. multiple channels are required, then the process scales Cascaded Cascaded Integrator Coef. Integrator Comb Filter Filter (CIC2) I & Q baseband (CIC5) Real or Quadrature Cascaded SYNC NCO Cascaded Integrator Output SYNC CIC Integrator Coef. Comb Filter SYNC_RCF Filter (CIC2) (CIC5) External JTAG Interface Sync. Circuit Figure 2.3-13 Fixed function transmit signal processor (TSP). Software defined radio CHAPTER 2.3 linearly. At the present time, this load exceeds the ca- Multiple arithmetic logic units pabilities of a general purpose DSP; however, as DSP; Multiply accelerators technology improves, it may be possible to take on some Shifters or all of the processing in the future. Hardware accelerators General purpose DSP On-chip memory Floating/fixed point optimization General purposes DSPs like microprocessors are designed to execute a software program. The software In an SDR, the general purpose DSP is generally tasked for a DSP is developed in the same manner as that for to perform the Nyquist rate processing; that is, the signal a microprocessor using program languages such as "C" processing required at data rates that supports the and assembly. However, DSPs are designed specifically to Nyquist rate of the raw data. In our SDR application that execute code as fast as possible. In fact, DSPs are usually may support a channel as wide as 10 MHz, the actual data designed to execute programs or tasks in real time. Since rate may be as high as 20 MHz. While not all applications the DSP may 