RF amplifier employing active load linearization
First Claim
Patent Images
1. A power amplifier circuit, comprising:
- an input for receiving an input signal;
a coupler for receiving the input signal and splitting the input signal on two signal paths;
a first amplifier device coupled to the coupler on a first of the two signal paths and receiving the input signal and providing a first amplified signal, said first amplifier device having a first turn on threshold;
a second amplifier device coupled to the coupler on a second of the two signal paths and receiving the input signal and providing a second amplified signal, said second amplifier device having a second turn on threshold and an impedance near zero when said input signal is below said turn on threshold;
an output load coupled to said first and second amplifier devices;
a DC power supply;
a first bias circuit coupled to the first amplifier device and the DC power supply and providing a first bias to the first amplifier device setting the first turn on threshold of said first amplifier device;
bias control means, coupled to the second amplifier device and the DC power supply, for providing a second bias to the second amplifier device setting the second turn on threshold of said second amplifier device at a substantially higher level than said first turn on threshold, said second turn on threshold corresponding to a peak power region of the input signal; and
an output coupled to the first and second amplifier devices via said output load and providing an amplified output signal.
9 Assignments
0 Petitions
Accused Products
Abstract
A power amplifier system for high efficiency signal amplification of digitally modulated carrier signal or multi-carrier signals is disclosed. The linearity of the amplifier is improved by providing dynamic load line adjustments through implementation of suitably defined transfer functions employing dynamic control of operational aspects of active devices in the power amplifier.
-
Citations
19 Claims
-
1. A power amplifier circuit, comprising:
-
an input for receiving an input signal;
a coupler for receiving the input signal and splitting the input signal on two signal paths;
a first amplifier device coupled to the coupler on a first of the two signal paths and receiving the input signal and providing a first amplified signal, said first amplifier device having a first turn on threshold;
a second amplifier device coupled to the coupler on a second of the two signal paths and receiving the input signal and providing a second amplified signal, said second amplifier device having a second turn on threshold and an impedance near zero when said input signal is below said turn on threshold;
an output load coupled to said first and second amplifier devices;
a DC power supply;
a first bias circuit coupled to the first amplifier device and the DC power supply and providing a first bias to the first amplifier device setting the first turn on threshold of said first amplifier device;
bias control means, coupled to the second amplifier device and the DC power supply, for providing a second bias to the second amplifier device setting the second turn on threshold of said second amplifier device at a substantially higher level than said first turn on threshold, said second turn on threshold corresponding to a peak power region of the input signal; and
an output coupled to the first and second amplifier devices via said output load and providing an amplified output signal. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
-
-
9. A radio frequency power amplifier system comprising:
-
an RF input port for receiving an RF input signal;
an RF output port for providing an amplified output signal in response to said input signal;
a power divider network having an input port coupled to the RF input port and first and second output ports;
a first signal delay element having an input port coupled to the first output port of said power divider network and an output port;
a first amplifier having an input port coupled to the output port of said delay element and an output port;
a directional coupler having an input port coupled to the second output port of said power divider network and a through port and a coupled port;
a continuously variable phase shifter for controlling insertion phase, said phase shifter having an input port coupled to the through port of said directional coupler and an output port;
a second amplifier having an input port coupled to the output port of said phase shifter;
a linear envelope detector network having an input port coupled to the coupled port of the said directional coupler and an output port, wherein said envelope detector output port provides signals responsive to the envelope of the input RF signal;
conduction angle control means, having at least one input port and a plurality of output ports, for generating a plurality of different conduction angle control functions, wherein said conduction angle control functions are responsive to the RF signal envelope applied to said RF power amplifier; and
a dynamic signal combiner network having first and second input ports and an output port, wherein the output port of said first amplifier is coupled to the first input port of the dynamic signal combiner network, the output port of said second amplifier is coupled to the second input port of the dynamic signal combiner network, and the output port of said signal combiner network is coupled to the RF output port. - View Dependent Claims (10, 11, 12, 13, 14)
-
-
15. A method for linear and efficient amplification of an RF input signal, comprising the steps of:
-
receiving an RF input signal;
sampling the input signal to provide a sampled input signal;
amplifying the input signal with a first amplifier device and applying the amplified signal across a load to provide an output signal;
amplifying the sampled input signal with a second amplifier device and applying the amplified sampled input signal to the output load in parallel with said amplified signal; and
dynamically varying the impedance of said second amplifier device from a first substantially constant impedance near zero value over the lower major portion of the input signal power range to a second higher impedance in a peak power range of the input signal to substantially reduce the load of the first amplifier device when the input signal approaches the peak power region while maintaining the load substantially constant over the lower major portion of the input signal power range. - View Dependent Claims (16, 17, 18, 19)
-
Specification