AM-FM transmitter power amplifier
First Claim
1. A power amplifier circuit for efficiently generating radio frequency output power to a load at plural output power levels comprising:
- a power amplifier for amplifying a modulated, radio frequency carrier and generating an amplified signal;
first matching means for matching an impedance of said circuit to an impedance of said load at a first transmission power level;
second matching means for matching the impedance of said circuit to the impedance of said load at a second transmission power level;
switching means for selectively connecting said amplified signal to said load through said first matching means in a first mode to operate said power amplifier means in a linear mode at a first preferred efficiency at said first transmission power level, and connecting said second matching means to said load through said second matching means in a second mode to operate said power amplifier means in a linear mode at a second preferred efficiency at said second power transmission level.
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Accused Products
Abstract
A power amplifier used in a portable, radio frequency transmitter is switched between different modes of operation when transmitting differently modulated carriers. The first mode of operation corresponds to amplitude modulation (AM), while a second mode corresponds to angle modulation techniques such as frequency modulation (FM). A switching network alters the impedance of the power amplifier to match network for matching the impedance of the transmitter antenna in order to achieve maximum efficiency in each mode of operation. Various switching methods and impedance matching circuits are disclosed.
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Citations
14 Claims
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1. A power amplifier circuit for efficiently generating radio frequency output power to a load at plural output power levels comprising:
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a power amplifier for amplifying a modulated, radio frequency carrier and generating an amplified signal; first matching means for matching an impedance of said circuit to an impedance of said load at a first transmission power level; second matching means for matching the impedance of said circuit to the impedance of said load at a second transmission power level; switching means for selectively connecting said amplified signal to said load through said first matching means in a first mode to operate said power amplifier means in a linear mode at a first preferred efficiency at said first transmission power level, and connecting said second matching means to said load through said second matching means in a second mode to operate said power amplifier means in a linear mode at a second preferred efficiency at said second power transmission level. - View Dependent Claims (2, 3, 4)
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5. A power amplifier circuit for efficiently generating radio frequency output power at plural output power levels to a load, comprising:
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a power amplifier for amplifying a modulated, radio frequency carrier and transmitting an amplified signal on a transmission line to said load; a reactance; and switching means for selectively connecting said reactance to said transmission line to match an impedance of said power amplifier circuit to an impedance of said load at a first power transmission level to operate said power amplifier means in a linear mode at a preferred efficiency in a first mode and for selectively disconnecting said reactance to match the impedance of said power amplifier circuit to the impedance of said load at a second power transmission level to operate said power amplifier means in a linear mode at a preferred efficiency in a second mode. - View Dependent Claims (6, 7)
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8. A power amplifier circuit for efficiently generating radio frequency output power at plural output power levels to a load, comprising:
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power amplifier means for amplifying a modulated, radio frequency carrier and transmitting an amplified signal on a transmission line to said load; harmonic filtering means, connected between said power amplifier means and said load, for filtering undesirable harmonic frequency components, said filtering means including a plurality of reactance means wherein at least one of said reactance means is a variable reactance means; and actuation means for selecting between a first and second impedance of said filtering means by varying said variable reactance means, said actuation means selecting said first impedance to deliver power at an optimal efficiency to said load at a first power transmission level in a linear mode of operation of the power amplifier means and said second impedance to deliver power at an optimal efficiency to said load at a second power transmission level in a linear mode of operation of the power amplifier means. - View Dependent Claims (9, 10, 11, 12)
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13. A power amplifier circuit for efficiently generating radio frequency output power at plural output power levels to a load, comprising:
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power amplifier means for amplifying a modulated, radio frequency carder and transmitting an amplified signal on a transmission line to said load; harmonic filtering means, connected between said power amplifier means and said load, for filtering undesirable harmonic frequency components, said filtering means including a plurality of reactance means wherein said reactance means is switchably selected between alternate reactance values; and actuation means for selecting between a first and second impedance of said filtering means by switchably selecting one of said reactance means to one of said alternate reactance values, said actuation means selecting said first impedance to deliver power at an optimal efficiency to said load at a first power transmission level in a linear operation of the power amplifier means and said second impedance to deliver power at an optimal efficiency to said load at a second power transmission level in a linear mode of operation of the power amplifier means. - View Dependent Claims (14)
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Specification