Digital baseband receiver in a multi-carrier power amplifier
First Claim
1. An apparatus, comprising:
- (a) a signal path having an input and an output and configured to communicate an RF communications signal disposed in a frequency band;
(b) a tunable receiver coupled to the signal path and configured to downconvert at least a portion of the frequency band to an Intermediate Frequency (IF) signal;
(c) at least one intermodulation distortion (IMD) reduction component coupled to the signal path; and
(d) a circuit arrangement configured to convert a time domain representation of the IF signal output by the tunable receiver to a frequency domain representation, identify an IMD product from the frequency domain representation of the IF signal, and control the IMD reduction component to suppress the IMD product at the output of the signal path.
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Accused Products
Abstract
A power amplifier system and method for locating carrier frequencies across a frequency band, identifying the modulation format of each carrier, and locating and suppressing undesired intermodulation distortion (IMD) products generated by the power amplifier. The system includes an amplifier for amplifying RF carrier signals in a main signal path, a variable phase shifter and variable attenuator on a feed forward path, and a tunable receiver that digitizes a portion of the frequency band to baseband. The tunable receiver includes a tunable voltage controlled oscillator which provides an oscillating frequency to a mixer and is phase-locked to a highly stable reference oscillator. The mixer downconverts a desired RF based on the oscillating frequency to IF. A filter passes only a selected portion of the IF signals, and the filter has a passband sufficient to discern both narrowband and wideband carriers and their associated IMD products. Based on the locations of the carrier frequencies, a processing unit determines the IMD locations of the carrier frequencies, determines the IMD locations, and adjusts the variable phase shifter and variable attenuator on the feed forward path until the IMD products in the main signal path are suppressed below a desired threshold.
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Citations
37 Claims
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1. An apparatus, comprising:
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(a) a signal path having an input and an output and configured to communicate an RF communications signal disposed in a frequency band;
(b) a tunable receiver coupled to the signal path and configured to downconvert at least a portion of the frequency band to an Intermediate Frequency (IF) signal;
(c) at least one intermodulation distortion (IMD) reduction component coupled to the signal path; and
(d) a circuit arrangement configured to convert a time domain representation of the IF signal output by the tunable receiver to a frequency domain representation, identify an IMD product from the frequency domain representation of the IF signal, and control the IMD reduction component to suppress the IMD product at the output of the signal path. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37)
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23. A multi-carrier power amplifier, comprising:
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(a) a main signal path having an input and an output and configured to communicate a multi-carrier RF communications signal disposed in a frequency band;
(b) an amplifier disposed within the main signal path;
(c) a feed forward path coupled to the main signal path;
(d) a tunable receiver coupled to the main signal path and configured to downconvert at least a portion of the frequency band to an Intermediate Frequency (IF) signal;
(e) at least one intermodulation distortion (IMD) reduction component disposed in the feed forward path; and
(f) a circuit arrangement configured to convert a time domain representation of the IF signal output by the tunable receiver to a frequency domain representation, identify a plurality of carrier signals and an IMD product from the frequency domain representation of the IF signal, and control the IMD reduction component to suppress the IMD product at the output of the main signal path.
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24. A method of suppressing an intermodulation distortion (IMD) product from an RF communications signal disposed in a frequency band, the method comprising:
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(a) downconverting at least a portion of the frequency band for the RF communications signal to an Intermediate Frequency (IF) signal;
(b) converting a time domain representation of the IF signal to a frequency domain representation;
(c) identifying an IMD product from the frequency domain representation of the IF signal; and
(d) controlling an IMD reduction component to suppress the IMD product from the RF communications signal.
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Specification