Amplifiers – With semiconductor amplifying device – Including distributed parameter-type coupling
Reexamination Certificate
2002-02-28
2003-12-23
Choe, Henry (Department: 2817)
Amplifiers
With semiconductor amplifying device
Including distributed parameter-type coupling
C330S295000
Reexamination Certificate
active
06667659
ABSTRACT:
FIELD OF THE INVENTION
This invention relates generally to the field of high efficiency amplifiers. Certain embodiments of this invention are more particularly related to radio frequency distributed power amplifiers with enhanced efficiency.
BACKGROUND OF THE INVENTION
In a conventional linear amplifier, DC to AC conversion efficiency is a function of output signal level relative to the DC supply voltage. Conversion efficiency decreases directly as a function of the output level, decreasing as the output signal level decreases. For battery powered devices such as radio frequency transmitters as used in cellular telephones and two-way radios, this limitation in efficiency imposes significant limitations on the battery life that can be expected for the device.
In some instances, the efficiency of a linear amplifier can be enhanced by modulating the supply voltage to the linear amplifier. In this technique, the amplifier's supply voltage is dynamically modified so that it approximately follows the envelope of the signal driving the linear amplifier. This keeps the supply voltage at or near the output voltage to enhance the amplifier's efficiency. Unfortunately, this technique cannot be universally applied to all linear amplifiers and generally requires that a DC-to-DC converter circuit be used to provide the supply voltage to the amplifier circuitry.
REFERENCES:
patent: 5365197 (1994-11-01), Ikalainen
patent: 5999057 (1999-12-01), Carlsson et al.
patent: 6433640 (2002-08-01), Pavio et al.
Stengel Robert
Thompson Bruce
Choe Henry
Motorola Inc.
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