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A suppressed feature waveform sonar transmission is produced by modulating a carrier wave with a baseband waveform that is generated from a known pulse sequence. A waveform embodiment of the pulse sequence is modified to create interference among the primary lobes of the constituent waveforms that a

A suppressed feature waveform sonar transmission is produced by modulating a carrier wave with a baseband waveform that is generated from a known pulse sequence. A waveform embodiment of the pulse sequence is modified to create interference among the primary lobes of the constituent waveforms that are representative of the individual pulses. The baseband waveform so created appears as noise, making the baseband waveform modulation of the sonar transmission difficult to detect without knowledge of the pulse sequence or baseband waveform structure. The sonar transmission can be analyzed by cross-correlating the received signal with the baseband waveform or the pulse sequence waveform. The pulse sequence is preferably a complementary sequence. Modification of the pulse sequence may be obtained by passing an embodiment of the pulse sequence through a bandpass filter. In such a modification, the bandpass filter is preferably overdriven by a pulse sequence waveform having a frequency that is about eight to about ten times the bandwidth of the filter.

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The invention claimed is: 1. A method of producing a suppressed feature waveform sonar transmission signal, said method comprising: modifying a pulse sequence waveform by passing said pulse sequence waveform through a bandpass filter to generate a baseband waveform, said baseband waveform resulting

The invention claimed is: 1. A method of producing a suppressed feature waveform sonar transmission signal, said method comprising: modifying a pulse sequence waveform by passing said pulse sequence waveform through a bandpass filter to generate a baseband waveform, said baseband waveform resulting from interference between primary lobes of the modified pulse sequence waveform; and modulating a carrier wave with said baseband waveform to produce the suppressed feature waveform sonar transmission signal. 2. The method of claim 1 wherein said baseband waveform resembles noise. 3. The method of claim 1 wherein said pulse sequence waveform is generated from a pulse sequence that is selected from one of a complementary pulse sequence, a Golay sequence, a Hadamard sequence, a Barker sequence, or a Welti sequence. 4. The method of claim 3 wherein said pulse sequence is a set of two or more sequences, from which a number of members of said set are selected and used independently to generate an equal number of baseband waveforms that are used in either a defined or a pseudo-random order to successively modulate portions of said carrier wave. 5. The method of claim 1 wherein said pulse sequence waveform is generated from a pulse sequence that manifests a complementary property; and wherein said baseband waveform retains said complementary property of said pulse sequence. 6. The method of claim 1 wherein said interference is the result of a broadening of the pulse width of the pulses in said pulse sequence waveform. 7. The method of claim 1 wherein said interference between primary lobes is generated when said pulse sequence waveform is passed through a bandpass filter. 8. The method of claim 7 wherein said pulse sequence waveform is characterized by a frequency that is at least twice the value of the bandwidth passed by said bandpass filter. 9. The method of claim 8 wherein said pulse sequence waveform is characterized by a frequency that is in the range from about eight to about ten times the value of the bandwidth passed by said bandpass filter. 10. The suppressed method of claim 1 wherein said modulation of said carrier wave with said baseband waveform is essentially undetectable by a detector that is not provided with at least one of said pulse sequence waveform, said pulse sequence from which said pulse sequence waveform was generated, or said baseband waveform. 11. The method of claim 1 wherein said modulated carrier wave is further altered by at least one of the following techniques: power management, frequency diversification, directivity selection, or tactical techniques.