A processing technique for continuous active sonar (CAS) that uses linear frequency modulation (LFM) waveforms is presented. LFM CAS employs wideband long-duration LFMs with 100% transmit duty cycle. The received signals are typically processed in sub-bands by forming a sequence of matched-filter replicas that correspond to consecutive segments of the full waveform; this increases the update rate of the sonar at the cost of decreased performance in each sub-band due to the decrease in processing bandwidth and duration (energy). The algorithm presented in this article achieves fast updates by forming a sequence of unique matched-filter replicas through a number of circular shifts to the transmitted LFM, resulting in processing across the frequency jump between pings. This approach allows increased processing duration and bandwidth (up to the full duration/bandwidth of the LFM) at the cost of reduced independence between updates. The circular-shift algorithm is mainly considered in the limit where the full duration and bandwidth of the waveform are exploited to provide partially independent detection and ranging opportunities. The update rate can be arbitrarily chosen independent of processing duration. The algorithm is validated with sonar data from the LCAS15 sea trial.

中文翻译：

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处理连续主动声纳传输以实现具有完全瞬时带宽的任意快速更新率


提出了一种使用线性频率调制（LFM）波形的连续主动声纳（CAS）处理技术。 LFM CAS 采用具有 100% 传输占空比的宽带长持续时间 LFM。接收到的信号通常在子带中进行处理，形成与全波形的连续段相对应的匹配滤波器副本序列；这提高了声纳的更新率，但代价是由于处理带宽和持续时间（能量）的减少而导致每个子带的性能下降。本文提出的算法通过对传输的 LFM 进行多次循环移位形成一系列独特的匹配滤波器副本，从而实现跨 ping 之间的频率跳跃的处理，从而实现快速更新。这种方法允许增加处理持续时间和带宽（高达 LFM 的整个持续时间/带宽），但代价是更新之间的独立性降低。循环移位算法主要考虑利用波形的整个持续时间和带宽来提供部分独立的检测和测距机会的限制。更新速率可以独立于处理持续时间任意选择。该算法通过 LCAS15 海上试验的声纳数据进行了验证。