Text: "Parametric arrays: A new concept for sonar." Any two sine-wave frequencies as simultaneous drivers combine to produce a sine-wave difference frequency propagating in water, essentially without sidebands or reverberations. Its pattern has a main lobe approximately equal to that of the high frequency drive, but devoid of sidelobes. The level of the propagating difference frequency is proportional to both the product of the two fundamental drive levels and to the square of the desired value of difference frequency. Believed to apply to scalar electromagnetic effects also. It may indicate a method of producing an electromagnetic sine wave without sidebands. If so, two such pure sine waves of the same frequency but of opposite phase could be utilized to produce a pure scalar (zero-vector) electromagnetic stress wave (longitudinal wave). Electronic Warfare Magazine. June 1977. p. 107-112.

See Also: parametric arrays, underwater communication, signal propagation, scalar electromagnetics.

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