A Fast Microprogrammed Digital Filter Supporting Early Signal Processing Research

Abstract : In the 1970s research and teaching of digital signal processing was started in several universities in Scandinavia. Special emphasis in the research was on digital filter structures implementable on emerging digital hardware. On the theoretical side, the development of computationally efficient, low-sensitivity digital filter structures was widely investigated. Realization of these novel transfer functions was also important in order to verify the efficiency of the filters in practice. The latest commercial microprocessors indicated that real time signal processing covering the audio range of signals was becoming realistic. A microprogrammable digital signal processor based on high speed bit-sliced architecture was designed at Helsinki University of Technology. With this hardware, the performance of computationally efficient, low-sensitivity digital filter structures was tested. Algorithm research with emphasis on implementation aspects had a great impact on the readiness of Finnish electronics and telecommunications industry to start using programmable digital hardware. Early DSP applications in telecommunications industry were released already in late 1970s. Ten years later, when the first GSM phones were under development, Finnish industry was on the leading edge of applying digital signal processors in a number of applications.