Linear power amplifier with distortion detection

Claim 2

A power amplifier for linearly amplifying RF signals in a predetermined frequency range comprising: an amplifier portion for amplifying an RF input signal and producing an RF output signal, said amplifier portion having a bias controller for controlling a bias of said amplifier; and a distortion detector portion adapted to sample said RF output signal and provide a feedback control signal to said bias controller based on an amount of distortion present in said RF output signal, wherein said feedback control signal causes said amplifier portion to increase said bias when said amount of distortion is above a distortion level, and decrease said bias when said amount of distortion is less than said distortion level.

Claim 3

A power amplifier as claimed in claim 1 wherein said distortion detector portion includes: a sampler for sampling said RF output signal and providing a sampled signal; a loop filter for filtering said sampled signal and providing a filtered signal; a detector for converting said filtered signal to a DC signal proportional to said filtered signal, said amount of distortion being based on said DC signal; and a bias control portion for providing said feedback control signal to said bias controller based on said DC signal.

Claim 4

A power amplifier as claimed in claim 2 wherein said RF output signal includes a linear portion and a non-linear portion, said loop filter includes means for filtering out said linear portion, and said detector produces said DC signal proportional to said non-linear portion, wherein said amount of distortion is based on said non-linear portion.

Claim 5

A power amplifier for linearly amplifying RF signals comprising: an amplifier portion for amplifying an RF input signal and producing an RF output signal, said amplifier portion having a bias controller; and a distortion detector portion adapted to sample said RF output signal and provide a feedback control signal to said bias controller based on an amount of distortion present in said RF output signal, wherein said distortion detector portion includes: a sampler for sampling said RF output signal and providing a sampled signal; a loop filter for filtering said sampled signal and providing a filtered signal; a detector for converting said filtered signal to a DC signal proportional to said filtered signal; and a bias control portion for providing said feedback control signal to said bias controller based on said DC signal, and wherein said RF output signal includes a linear portion and a non-linear portion, said loop filter includes means for filtering out said linear portion, and said detector produces said DC signal proportional to said non-linear portion, and wherein said amplifier portion includes field effect transistor (FET) devices biased as a class `A` configuration and having a quiescent bias point, and wherein said feedback control signal is proportional to said amount of distortion, and said bias control portion is configured to increase said quiescent bias point when said amount of distortion is above a predetermined level, and decrease said quiescent bias point when said amount of distortion is less than said predetermined level.

Claim 6

A power amplifier for linearly amplifying RF signals comprising: an amplifier portion for amplifying an RF input signal and producing an RF output signal, said amplifier portion having a bias controller; and a distortion detector portion adapted to sample said RF output signal and provide a feedback control signal to said bias controller based on an amount of distortion present in said RF output signal, wherein said distortion detector portion includes: a sampler for sampling said RF output signal and providing a sampled signal; a loop filter for filtering said sampled signal and providing a filtered signal; a detector for converting said filtered signal to a DC signal proportional to said filtered signal; and a bias control portion for providing said feedback control signal to said bias controller based on said DC signal, and wherein said RF output signal includes a linear portion and a non-linear portion, said loop filter includes means for filtering out said linear portion, and said detector produces said DC signal proportional to said non-linear portion, and wherein said amplifier portion includes field effect transistor (FET) devices biased as a class `A` configuration and having a quiescent bias point, and wherein said feedback control signal is proportional to said amount of distortion, and said bias control portion is configured to increase said quiescent bias point when said amount of distortion is above a predetermined level, and decrease said quiescent bias point when said amount of distortion is less than said predetermined level.

Claim 7

A power amplifier as claimed in claim 4 wherein said FET devices of said amplifier portion are fabricated from gallium arsenide (GaAs).

Claim 8

A power amplifier as claimed in claim 5 wherein said RF input signal includes K-band multicarrier signals spread out over a bandwidth of five GHz.

Claim 9

A power amplifier as claimed in claim 6 wherein said power amplifier has a power-added efficiency between 20 and 30 percent for output power levels of between 22 and 36 dBm.

Claim 10

A power amplifier as claimed in claim 7 wherein said RF input signal is a K-band multicarrier signal and said amplifier portion amplifies said RF input signal between 30 and 35 dB, and wherein said RF input signal is a multi-carrier signal having noise-like characteristics, and wherein said amplifier portion has a gain of between 7 and 11 dB, and has a power out of between 3 and 4 watts.

Claim 11

A power amplifier as claimed in claim 8 wherein said detector produces said DC signal proportional to harmonics of said RF input signal, said harmonics comprising at least part of said non-linear portion.

Claim 12

A power amplifier as claimed in claim 9 wherein FET devices are pseudomorphic high electron mobility transistor (PHEMT) devices having a gate width between 0.8 and 4.0 millimeters.

Claim 13

A power amplifier for linearly amplifying RF signals in a predetermined frequency range comprising: an amplifier portion for amplifying an RF input signal and producing an RF output signal, said amplifier portion having a bias controller for controlling a bias of said amplifier; a sampler for sampling said RF output signal and providing a sampled signal; a loop filter for filtering said sampled signal and providing a filtered signal; a detector for converting said filtered signal to a DC signal proportional to said filtered signal, said DC signal based on an amount of distortion present in said RF output signal; and a bias control portion for providing a feedback control signal to said bias controller based on said filtered signal, wherein said feedback control signal causes said amplifier portion to increase said bias when said amount of distortion is above a distortion level, and decrease said bias when said amount of distortion is less than said distortion level.

Claim 14

A power amplifier for linearly amplifying RF signals in a predetermined frequency range comprising: an amplifier portion for amplifying an RF input signal and producing an RF output signal, said amplifier portion having a bias controller for controlling a bias of said amplifier; a sampler for sampling said RF output signal and providing a sampled signal; a loop filter for filtering said sampled signal and providing a filtered signal; a detector for converting said filtered signal to a DC signal proportional to said filtered signal, said DC signal based on an amount of distortion present in said RF output signal; and a bias control portion for providing a feedback control signal to said bias controller based on said filtered signal, wherein said feedback control signal causes said amplifier portion to increase said bias when said amount of distortion is above a distortion level, and decrease said bias when said amount of distortion is less than said distortion level.

Claim 15

A power amplifier as claimed in claim 11 wherein said RF output signal includes a linear portion and a non-linear portion, said loop filter includes means for filtering out said linear portion, and said detector produces said DC signal proportional to said non-linear portion.

Claim 16

A power amplifier for linearly amplifying RF signals comprising: an amplifier portion for amplifying an RF input signal and producing an RF output signal, said amplifier portion having a bias controller; a sampler for sampling said RF output signal and providing a sampled signal: a loop filter for filtering said sampled signal and providing a filtered signal: a detector for converting said filtered signal to a DC signal proportional to said filtered signal; and a bias control portion for providing a feedback control signal to said bias controller based on said filtered signal, wherein said RF output signal includes a linear portion and a non-linear portion, said loop filter includes means for filtering out said linear portion, and said detector produces said DC signal proportional to said non-linear portion, and wherein said amplifier portion includes field effect transistor (FET) devices biased as a class `A` configuration, said FET devices fabricated from gallium arsenide (GaAs).

Claim 17

A power amplifier for linearly amplifying RF signals comprising: an amplifier portion for amplifying an RF input signal and producing an RF output signal, said amplifier portion having a bias controller; a sampler for sampling said RF output signal and providing a sampled signal: a loop filter for filtering said sampled signal and providing a filtered signal: a detector for converting said filtered signal to a DC signal proportional to said filtered signal; and a bias control portion for providing a feedback control signal to said bias controller based on said filtered signal, wherein said RF output signal includes a linear portion and a non-linear portion, said loop filter includes means for filtering out said linear portion, and said detector produces said DC signal proportional to said non-linear portion, and wherein said amplifier portion includes field effect transistor (FET) devices biased as a class `A` configuration, said FET devices fabricated from gallium arsenide (GaAs).

Claim 18

A power amplifier as claimed in claim 13 wherein said RF input signal includes K-band multicarrier signals spread out over a bandwidth of five GHz, and wherein said detector produces said DC signal proportional to harmonics of said RF input signal, said harmonics comprising at least part of said non-linear portion.

Claim 21

A method as claimed in claim 15 wherein said RF input signal is a K-band multicarrier signal and the amplifying step includes the step of amplifying said RF input signal between 30 and 35 dB.

Claim 24

A method as claimed in claim 17 wherein said amplifier portion includes a plurality of transistors having said quiescent bias point, and wherein said feedback signal is proportional to an amount of distortion in said amplified signal, and wherein the changing step includes the steps of: increasing said quiescent bias point when said amount of distortion is above a predetermined level; and decreasing said quiescent bias point when said amount of distortion is less than said predetermined level.

Claim 25

A power amplifier for linearly amplifying RF signals comprising: an amplifier portion for amplifying an RF input signal and producing an RF output signal, said amplifier portion having a bias controller; and a distortion detector portion adapted to sample said RF output signal and provide a feedback control signal to said bias controller based on an amount of distortion present in said RF output signal, wherein said distortion detector portion includes: a sampler for sampling said RF output signal and providing a sampled signal; a loop filter for filtering said sampled signal and providing a filtered signal; a detector for converting said filtered signal to a DC signal proportional to said filtered signal; and a bias control portion for providing said feedback control signal to said bias controller based on said DC signal, wherein said RF output signal includes a linear portion and a non-linear portion, said loop filter includes means for filtering out said linear portion, and said detector produces said DC signal proportional to said non-linear portion, wherein said amplifier portion has a bias associated therewith, and said feedback control signal is proportional to said amount of distortion, and said bias control portion is configured to increase said bias when said amount of distortion is above a predetermined level, and decrease said bias when said amount of distortion is less than said predetermined level.

Claim 26

A power amplifier for linearly amplifying RF signals comprising: an amplifier portion for amplifying an RF input signal and producing an RF output signal, said amplifier portion having a bias controller; and a distortion detector portion adapted to sample said RF output signal and provide a feedback control signal to said bias controller based on an amount of distortion present in said RF output signal, wherein said distortion detector portion includes: a sampler for sampling said RF output signal and providing a sampled signal; a loop filter for filtering said sampled signal and providing a filtered signal; a detector for converting said filtered signal to a DC signal proportional to said filtered signal; and a bias control portion for providing said feedback control signal to said bias controller based on said DC signal, wherein said RF output signal includes a linear portion and a non-linear portion, said loop filter includes means for filtering out said linear portion, and said detector produces said DC signal proportional to said non-linear portion, wherein said amplifier portion has a bias associated therewith, and said feedback control signal is proportional to said amount of distortion, and said bias control portion is configured to increase said bias when said amount of distortion is above a predetermined level, and decrease said bias when said amount of distortion is less than said predetermined level.