Digital Quadrature Demodulation of LFM Signals Obtained by Lowpass Filtering

  • Vera Behar
  • Christo Kabakchiev
Conference paper
Part of the Lecture Notes in Computer Science book series (LNCS, volume 2542)


An effective digital demodulation system based on the technique of Ho, Chan and Inko is designed for quadrature demodulation of signals with a linear frequency modulation (LFM). The influence of LFM-signal parameters on the quality of demodulation is studied. Two variants of a sampling frequency are chosen, and a set of lowpass filters for Q-component generation is designed for each variant of a sampling frequency. The quality of demodulation is estimated in terms of absolute amplitude and phase errors evaluated as a function of system parameters. The results obtained in simulations show that the optimal choice of a sampling frequency (48 MHz) enables to reduce the imbalance phase errors to minimum (0.0012°) if the optimal equiripple lowpass filter with only 6 elements is chosen for Q-component generation.


Sampling Frequency Phase Error Linear Frequency Modulation Absolute Amplitude Linear Frequency Modulation Signal 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.


Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.


  1. 1.
    Rice, D. W., Wu, K. H.: Quadrature Sampling with High Dynamic Range. IEEE Trans., AES-18 (4) (1982) 736–739.Google Scholar
  2. 2.
    Watters, W. M., Jarrett, B. R.: Bandpass Signal Sampling and Coherent Detection. IEEE Trans., AES-18, 4 (1982) 740–749.Google Scholar
  3. 3.
    No, K. C., Chan, Y. I., Inkol, R.: A Digital Quadrature Demodulation System. IEEE Trans., AES-32, 4 (1996) 1218–1226.Google Scholar
  4. 4.
    Rabiner, L. R., Gold, B.: Theory and Application of Digital Signal Processing. Prentice-Hall, New Jersey (1975)Google Scholar
  5. 5.
    Kabakchiev, C., Behar, V.: CFAR Radar Image Detection in Pulse Jamming. IEEE Fourth Int. Symp. ISSSTA’96, Mainz (1996) 182–185.Google Scholar
  6. 6.
    Behar, V., Kabakchiev, C., Doukovska, L.: Adaptive CA CFAR Processor for Radar Target Detection in Pulse Jamming. Journal of VLSI Signal Processing Systems for Signal, Image, and Video Technology, Vol. 26, 3 (2000) 386–396.Google Scholar

Copyright information

© Springer-Verlag Berlin Heidelberg 2003

Authors and Affiliations

  • Vera Behar
    • 1
  • Christo Kabakchiev
    • 2
  1. 1.Dep. of Biomedical EngineeringInstitute of Technology-TechnionHaifaIsrael
  2. 2.Institute of Information TechnologiesBulgarian Academy of SciencesSofiaBulgaria

Personalised recommendations