Other

Harris Corporation

Jeffrey M Strang

Stuart Pullen

Patrick Anthony Begley

Arecio A Hernandez

David W Hoyt

David George Hoyt

Pulse width modulated (&ldquo;Class D&rdquo;) amplifiers and controllers switching in the 50 khz to 2 MHz range generate harmonics that interfere with AM radio reception. This interference has precluded wide spread acceptance of class D amplifiers in products that include an AM radio. The amplifier described here uses a a harmonic avoidance modulator when operating with an AM radio to avoid generating harmonics at the receiver selected frequency or the intermediate (IF) frequency thereof.

Dual mode class D amplifiers

Pulse width modulated (&ldquo;Class D&rdquo;) amplifiers and controllers switching in the 50 khz to 2 MHz range generate harmonics which interfere with AM radio reception. This has precluded wide spread acceptance of class D amplifiers in products with an AM radio. The amplifiers described here use a modified modulation technique when operating with an AM radio to avoid generating harmonics at the receiver selected frequency or its intermediate (IF) frequency. One embodiment uses a harmonic avoidance modulator. A second embodiment uses two or more oscillators and tests for the least distorted output signal. A third embodiment switches the mode of operation to a class AB amplifier when an AM signal is amplified.

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Durham, NC, United States of America

Jeffrey M Strang