A digital signal processing algorithm for detecting interrupted continuous wave undersea tracking signals

In order to maintain fleet, readiness, the Navy requires accurate undersea, tracking systems for testing and evaluation. To obtain tracking information, undersea vehicles transmit known acoustic signals into the ocean. Spatially separated undersea microphones called hydrophones convert the received acoustic signals into electrical signals which are cabled back to shore to be processed by a real-time programmable digital signal processor (DSP). The purpose of the DSP is to detect and time-tag the incoming undersea signals for input to a tracking computer. Optimal use of the signal processing capabilities requires computationally efficient signal processing algorithms. A common undersea tracking signal format is the interrupted continuous wave (ICW) signal. This paper presents a computationally efficient complex demodulation algorithm for detecting and time-tagging ICW signals. A complete discussion of the ICW complex demodulation algorithm is presented, as is the design requirements for processing an ICW signal at any given frequency. Implementation of this complex demodulation algorithm increases the flexibility and capabilities of a real-time DSP system