Tutorials / Short Courses

2015 IEEE International Symposium on Circuits and Systems (Nuit de la litterature 2015)

Sunday, 21 May 2015


A1: Multirate I/Q Signal Processing for Communication Systems

, Prof. and , Dr. Tech.

13:30 - 17:30



In communications signal processing, it is common to use the notion of complex signals. In the implementation sense, a complex signal is nothing more than the combination of two real signals (real and imaginary parts) carried, e.g., by two separate wires or bit-streams. However, the convenience of the complex signal notation in frequency domain analysis has made the complex signal concept an essential ingredient in communication theoretic and communications transceiver signal processing literature.

Another important ingredient in communications signal processing is the bandpass signal concept, and the possibility to model a (real) bandpass system with a complex baseband model (in this context, the complex signal concept becomes mandatory). In general, various combinations of real/complex and baseband/bandpass signal and system models are encountered when studying the signal processing algorithms for communications receivers and transmitters.

Most of today's literature is satisfied with a very rudimentary treatment of complex signal and system concepts. However, thorough understanding of the possibilities of complex signal processing, combined with efficient multirate DSP algorithms and digital VLSI technologies offers new tools for efficient communications signal processing implementations.

This tutorial aims to provide a comprehensive overview of continuous-time and discrete-time complex signals and systems, with emphasis on efficient multirate digital signal processing techniques.


1. Complex Signals and Systems

  • Basic concepts and definitions

  • Analytic signals and Hilbert transform

  • Frequency translations and mixing

  • Complex signals and sampling

  • Examples from receiver signal processing

2. Sampling and Multirate DSP with Bandpass and I/Q Signals

  • Sampling theory for bandpass signals

  • Multirate processing of bandpass and I/Q signals

  • Combining mixing and multirate operations for frequency translation

  • Efficient polyphase structures

  • Complex multirate filter banks and frequency-domain signal processing

  • Real vs. complex sampling

  • Quantization and sampling jitter effects

  • Discrete-time analog processing as an alternative to all-digital designs

  • Examples related to advanced receiver structures for software defined radios

3. I/Q Mismatch Problems in Analog I/Q Signal Processing

  • I/Q signal processing in receivers

  • Imbalance effects in receiver front-ends

  • Signal models for I/Q imbalance

  • I/Q imbalance compensation idea

  • Imbalance problem in second-order sampling schemes


Short Biographies

Markku Renfors (Senior Member, IEEE) was born in Suoniemi, Finland, on January 21, 1953. He received the Diploma Engineer, Licentiate of Technology, and Doctor of Technology Degrees from Tampere University of Technology (TUT), Finland, in 1978, 1981, and 1982, respectively. He held various research and teaching positions at TUT during 1976 to 1988. In the years 1988 - 1991 he was working as a Design Manager in the area of video signal processing, especially for HDTV, at Nokia Research Centre and Nokia Consumer Electronics. Since 1992 he has been a Professor of Telecommunications at TUT. His main research areas are multicarrier systems and signal processing algorithms for flexible radio receivers and transmitters.

Mikko Valkama (Member, IEEE) was born in Pirkkala, Finland, on November 27, 1975. He received the M.Sc. and Ph.D. degrees (both with honors) in Electrical Engineering (EE) from Tampere University of Technology (TUT), Finland, in 2004 and 2005, respectively. In 2015 he received the Best Ph.D. Thesis -award by the Finnish Academy of Science and Letters for his thesis entitled "Advanced I/Q Signal Processing for Wideband Receivers: Models and Algorithms". In 2007, he was working as a visiting researcher with the Communications Systems and Signal Processing Institute at SDSU, San Diego, CA. Currently, he is working as a senior researcher and docent with the Institute of Communications Engineering at TUT, Finland. His general research interests include communications signal processing, estimation and detection techniques, signal processing algorithms for software defined flexible radios, and digital transmission techniques such as different variants of multicarrier modulation methods and OFDM.



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