New CMOS chip facilitates multibit correlation

Although correlation is a simple mathematical function, its implementation in digital hardware is cumbersome and complex. During the past few years, both digital and analog correlator integrated circuits have helped reduce the cost and size of correlation hardware. Unfortunately, the analog correlators exhibit noise and calibration problems, while the digital devices are generally limited to single-bit resolution, requiring the parallel use of many devices or the use of very coarse signal quantization levels. In response to these objections and to the need for low power correlators, TRW LSI Products is developing the TMC2220, a four-channel, 32-word CMOS digital correlator chip. This paper outlines the architecture of this versatile chip and illustrates some of its advantages in multibit and dual-channel (in phase and quadrature) applications. Potential noise performance of the four-bit correlator is compared to that of similar single-bit and ideal analog devices. A few applications which might best exploit the TMC2220´s architecture are also discussed.