FPGA Based Frequency Selective RF Channel Simulator Using IF Sampling

The implementation of a low cost, frequency se- lective, RF channel simulator architecture is explored. The system is implemented almost entirely in the digital domain by use of IF sampling with the signal processing performed in a Texas Instruments TMS320C6701 floating point DSP and a Xilinx XC4044XL FPGA. The prototype system costs less than $3900 and is capable of simulating three delay taps. It is believed that a system capable of simulating 12 delay taps with a bandwidth of 5 MHz could be built at a cost less than $2000, at least an order of magnitude cheaper than commercially available channel simulators of compara- ble performance. I. Summary Designing a modern wireless communication system is a formidable task. Today's users demand good voice quality, have a low tolerance for busy signals or dropped connec- tions, and desire error free, high-speed data transmission. For a system to eciently meet these requirements, it must perform well in many dierent environments where the radio propagation characteristics vary considerably. En- suring a product's performance requires not only analysis and simulation, but also prototyping and testing. Unfortu- nately, eld-testing a wireless product in all of the possible radio environments is cost prohibitive and time consum- ing. A much more practical approach is to use a real time channel simulator that may be congured to emulate the various radio propagation characteristics encountered in the real world. The available channel simulators on the market today are complex and costly (from $24,000 to $500,000 (1)), of- ten requiring several circuit cards and multiple processors. Recent increases in the performance of digital signal pro- cessors (DSPs) and eld programmable gate arrays (FP- GAs) suggest the possibility of greatly reducing the cost and complexity required in implementing a channel simula- tor. This paper presents the implementation of a low cost real-time frequency selective radio frequency (RF) channel simulator