Northrop Grumman Systems Corporation

Michael P Johnson

Michael Scott Andrews

Peter E Madden

Paul N Turner

Robert A Bramble

Basil Fedun

A radio-frequency (RF) transmitter power amplifier circuit provides for practically linear performance by predistorting the amplifier input signals to compensate for amplifier distortion at high power levels, and provides a fine degree of control of amplifier power needed to handle complex modulation schemes with widely and rapidly varying power requirements. A predistortion database () contains gain and phase corrections for various transmission types and a separate automatic gain control database () contains fine amplifier gain corrections. A real-time processor () combines the two types of corrections and applies them to the amplifier input signals, and a background processor () continually updates both databases in accordance with a programmable priority scheme. Integration of predistortion and amplifier power control is achieved in a manner that minimizes adverse effects of one type of control on the other. One feature of the invention provides for rapid convergence of the predistortion correction.

Efficient method and means for integration of power control and predistortion in a transmitter

A piston transducer having a central longitudinal axis and at least one piston member and an active transducer section displaced from one another along the longitudinal axis. Movement of the active transducer section is generally in a plane perpendicular to the longitudinal axis and a series of lever arms couple the movement of the active transducer section into a corresponding axial movement of the piston member and which axial movement is with a uniform velocity across the radiating surface thereof. For two-sided radiation, another piston member and series of levers may be connected to the active transducer section.

Transversely driven piston transducer

A method and apparatus for reducing noise originating in a flowing stream of gases in which the noise is progressively absorbed from the flowing stream to provide noise of reduced intensity relative to noise intensity at the upstream end of the stream, and the noise of reduced intensity actively attenuated with controlled sound energy. To facilitate the active attenuation of noise, the flowing stream is preferably divided into a plurality of smaller streams after a level of reduced intensities is attained and the active attenuation performed independently in each of the smaller streams. The apparatus is in the nature of a conduit (10) which defines a single duct extending from the inlet end (14) for a portion of the length of the conduit. Downstream, the single duct joins with a plurality of ducts (32,34) extending to the outlet end (16). An active noise attenuating device is preferably provided in each of the plurality of ducts.

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Shaker Heights, OH, United States of America

Michael P Johnson