Experimental Verification of a Doppler Velocity Measurement Method with Second-Time-Around Echo Suppression for Synthetic Bandwidth Radars

Kentaro ISODA  Teruyuki HARA  

IEICE TRANSACTIONS on Communications   Vol.E100-B   No.10   pp.1968-1975
Publication Date: 2017/10/01
Online ISSN: 1745-1345
Type of Manuscript: PAPER
Category: Sensing
synthetic bandwidth radar,  synthetic high-range-resolution radar,  stepped-frequency,  Doppler velocity,  

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Range resolution is one of the metrics of radar performance. Synthetic bandwidth radar has been proposed for high-range-resolution. The transmitted frequency and down-conversion frequency of this type of radar are shifted by fixed amounts from pulse to pulse. Received signals are synthesized by taking IFFT for high-range-resolution. However, this type of radar has a problem with second-time-around echoes since multiple pulses are utilized. Moreover, a range shift occurs due to Doppler velocity. Thus second-time-around echo suppression and Doppler velocity compensation are required for accurate target range measurement. We show in this paper a Doppler velocity measurement method with second-time-around echo suppression for synthetic bandwidth radars. Our proposed method interleaves the transmission of ascending and descending frequency sequences. The Doppler velocity is measured by using a Fourier transform of the multiplication of the signals received using both sequences. The transmitted frequency difference of the adjacent pulses is wider than the bandwidth of the matched filter, so the second-time-around echoes are down-converted to the outside band of the matched filter and suppressed. We verify the principle of the proposed method using numerical simulations and experiments. The results show that second-time-around echoes were suppressed by 7.8dB, the Doppler velocity could be obtained and the range shift due to Doppler velocity was reduced by 7.37 times compared to the conventional SBR.