Methods and apparatus for supporting linearization on power combined power amplifiers
Methods and apparatus for implementing a power amplifier circuit assembly an uneven power splitter which feeds two power amplifiers of different amplifier classes are described. By supplying different amounts of power to different amplifier circuits having different performance curves, an overall combined amplifier performance having a relatively uniform, e.g., flat, performance curve over a wide range of frequencies is achieved. In at least some embodiments one of the amplifiers is a class B power amplifier and the other amplifier is a class C power amplifier. In some but not necessarily all embodiments a phase shift is introduced on a signal path to one of the power amplifiers to compensate for a difference in phase shifts introduced by the power amplifiers which are used in parallel.
1. A power amplifier circuit assembly comprising:
an uneven power splitter including a power splitter signal input for receiving a signal to be amplified, a first power splitter output and a second power splitter output, said uneven power splitter providing different amounts of power from an input signal received at said power splitter signal input to said first and second power splitter outputs;
a first power amplifier having a first power amplifier input and a first power amplifier output, the first power amplifier input being coupled to the first power splitter output; and
a second power amplifier, having a second power amplifier input, coupled to the second power splitter output, and a second power amplifier output, said first power amplifier output and the second power amplifier output being coupled to each other and to a signal output of the power amplifier circuit assembly, said second power amplifier being a different class amplifier than said first power amplifier;
wherein the uneven power splitter includes a first transmission path and a second transmission path, said first transmission path including a first impedance, said second transmission path including a second impedance, said first transmission path coupling the power splitter signal input to the first power splitter output, said second transmission path coupling the power splitter signal input to the second power splitter output, the first and second impedances being different; and
wherein one of said first and second transmission paths includes a phase delay element not included in the other one of said first and second transmission paths.
2. The power amplifier circuit assembly of claim 1 ,
wherein the first impedance is a first transmission line impedance; and
wherein the second impedance is a second transmission line impedance.
3. The power amplifier circuit assembly of claim 1 ,
wherein said first transmission path is implemented using one or more of: i) a capacitor, ii) a resistor, or iii) an inductor; and
wherein said second transmission path is implemented using one or more of: i) a capacitor, ii) a resistor, or iii) an inductor.
4. The power amplifier circuit assembly of claim 1 , wherein said first power amplifier is a class-B power amplifier and said second power amplifier is a class-C power amplifier.
5. The power amplifier circuit assembly of claim 4 , wherein the first impedance is lower than said second impedance.
6. The power amplifier circuit assembly of claim 4 , wherein the second impedance is lower than said first impedance.
7. The power amplifier circuit assembly of claim 1 , wherein the uneven power splitter further includes:
a resistor bridging the first and second transmission paths.
8. The power amplifier circuit of claim 1 , wherein said phase delay element is a transmission line.
9. The power amplifier circuit of claim 1 , wherein said phase delay element is implemented using one or more of: i) a capacitor, ii) a resistor or iii) an inductor.
10. The power amplifier circuit assembly of claim 1 , wherein the phase delay element balances a phase difference introduced between the first and second power amplifiers due to a difference in amplifier size and biasing between the first and second power amplifiers.
11. The power amplifier circuit assembly of claim 1 , further comprising:
a power amplifier circuit assembly input for receiving an input signal; and
a signal driver coupling the power amplifier circuit assembly input to the power splitter signal input, the signal driver including an amplifier for amplifying the input signal prior to it being supplied to the power splitter signal input of the uneven power splitter.
12. The power amplifier circuit assembly of claim 11 , wherein the output impedance of the signal driver is different than the input impedance of at least one of the first and second power amplifiers.
13. The power amplifier circuit assembly of claim 1 , wherein the overall gain from the input of uneven power spitter to the signal output of the power amplifier circuit assembly is flat.
14. The power amplifier circuit assembly of claim 1 , wherein the uneven power splitter is wideband.
15. The power amplifier circuit assembly of claim 1 , wherein wideband is intended to mean above 5% fractional bandwidth.
16. The power amplifier circuit assembly of claim 1 , wherein said power amplifier circuit assembly amplifies signals in the microwave range of 1 GHz to 220 GHz.
17. The power amplifier circuit assembly of claim 1 , wherein said power amplifier circuit assembly is part of a large antenna array assembly.