5. Frequency-Modulated Pulse

  1. Nadav Levanon and
  2. Eli Mozeson

Published Online: 18 AUG 2004

DOI: 10.1002/0471663085.ch5

Radar Signals

Radar Signals

How to Cite

Levanon, N. and Mozeson, E. (2004) Frequency-Modulated Pulse, in Radar Signals, John Wiley & Sons, Inc., Hoboken, NJ, USA. doi: 10.1002/0471663085.ch5

Publication History

  1. Published Online: 18 AUG 2004
  2. Published Print: 9 JUL 2004

ISBN Information

Print ISBN: 9780471473787

Online ISBN: 9780471663089

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Keywords:

  • radar;
  • LFM;
  • nonlinear-FM;
  • Costas signal;
  • orthogonality;
  • ambiguity function;
  • stationary phase;
  • pulse compression;
  • resolution;
  • sidelobes;
  • weight window

Summary

Two additional frequency modulated signals are described that are different from the linear-FM signal discussed in the previous chapter.

The first is the Costas signal, in which the frequency evolution is random-like, in contrast with the linear evolution in LFM. The resulting ambiguity function (AF) has a thumbtack shape, in contrast to the ridge found in LFM. The Costas signal is explained in detail, and the Welch construction algorithms are described. Appendix 5.1 includes a MATLAB code that implements those algorithms.

Because LFM exhibited relatively high autocorrelation sidelobes, some form of amplitude weighting was necessary in order to reshape the spectrum and thus reduce the autocorrelation sidelobes. In nonlinear-FM, the second signal discussed in this chapter, the spectrum is shaped not by amplitude weighting, but by spending more time in the frequencies that need to be emphasized. Several different nonlinear frequency evolution laws and their performances are described.