Wideband Noise Radar based in Phase Coded Sequences

At present, widely-used radar systems either use very short pulses or linear frequency modulated waveforms, and are based on either monoor bi-static configurations. These systems suffer from having stronger sidelobes, thereby masking weaker returns from subtle changes and making it difficult to detect these changes. To overcome the problem of stronger sidelobes, various coding techniques have been proposed with varying degrees of success. One such technique is based on the transmission of pseudorandom binary sequences (PRBS). Although, PRBS are considered a good option in terms of their autocorrelation function, these sequences are not optimal if sidelobes level is taken into account. This problem can be overcome if the transmit process is composed of complementary binary series of sequences known as Golay series [Golay, 1961; Sivaswamy, 1978; Alejos, 2005; Alejos, 2007; Alejos, 2008]. Golay codes are pairs of codes that have non-periodic autocorrelation functions with null sidelobes levels. In the present chapter, we propose the improvement of PRBS-based noise radar sounders by using pairs of complementary binary series of Golay sequences series. We demonstrate, in qualitative and quantitative forms, the improvement reached by employing Golay sequences. The larger dynamic range of the sounder and the better precision in wideband parameter estimation are the main benefits due to the use of Golay sequences. This is important when dealing with large attenuation, as at millimeter frequency bands. Different schemes are explained in order to implement this kind of radar sounders, as well as the measurement procedure is detailed. The processing gain is also explained. Measurements, using both kinds of sequences, have been performed in actual scenarios. Channel functions and parameters have been calculated and compared. Finally the Fleury’s limit [Fleury, 1996] is introduced as a formal way of checking the availability of the obtained results.