Power amplifier linearization
First Claim
1. A combination comprising:
- a high power amplifier (HPA) for transmitting an RF modulated signal said HPA having an input port and an output port, and said HPA being subject to introducing distortions into the transmitted signals produced at its output port;
means for receiving digital baseband signals;
means responsive to said digital baseband signals for digitally up-converting the baseband signals and generating digital signals defining a digital RF waveform corresponding to the baseband signals; and
a digital RF predistorter circuit responsive to the digital signals defining the digital RF waveform and to one of (a) a digitally sampled signal derived from the output of the HPA and (b) stored data pertaining to the characteristics of the HPA, for directly operating on and modifying consecutive digital signal samples defining the digital RF waveform on a point by point basis; and
means for coupling the modified digital signals defining the digital RF waveform to the input port of the HPA for linearizing the response of the HPA and producing an output signal at the output port of the HPA which tends to be a linear function of the baseband signals.
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Accused Products
Abstract
A system for linearizing the output of a high power amplifier (HPA) designed to transmit an RF modulated signal includes in its transmit section a digital up-converter for processing baseband input signals and generating a desired digital RF waveform, T(s). The desired digital RF waveform T(s) is then fed to a digital predistorter circuit for producing a predistorted digital RF waveform P(s)T(s) which, as modified, may be applied via a high sampling speed high linearity digital to analog converter to the high power amplifier (HPA) to produce an output signal which is a linear function of the baseband input signal. The digital predistorter circuit may be of the adaptive type or of the predictive type. Circuits embodying the invention may include encoding circuitry for converting multi-bit signals to a serial stream of single-bit pulses for enabling simplification in the digital to analog conversion. In accordance with the invention, corrections for non-linearity of the HPA may be made directly on the RF waveform using ultra-high speed superconducting electronics (SCE) and decreasing the time delay between sensing a transmitted signal and generating a correcting (linearizing) signal.
67 Citations
30 Claims
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1. A combination comprising:
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a high power amplifier (HPA) for transmitting an RF modulated signal said HPA having an input port and an output port, and said HPA being subject to introducing distortions into the transmitted signals produced at its output port; means for receiving digital baseband signals; means responsive to said digital baseband signals for digitally up-converting the baseband signals and generating digital signals defining a digital RF waveform corresponding to the baseband signals; and a digital RF predistorter circuit responsive to the digital signals defining the digital RF waveform and to one of (a) a digitally sampled signal derived from the output of the HPA and (b) stored data pertaining to the characteristics of the HPA, for directly operating on and modifying consecutive digital signal samples defining the digital RF waveform on a point by point basis; and means for coupling the modified digital signals defining the digital RF waveform to the input port of the HPA for linearizing the response of the HPA and producing an output signal at the output port of the HPA which tends to be a linear function of the baseband signals. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 14, 15, 16)
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13. The combination as claimed in 12, wherein the digital RF predistorter circuit includes means for comparing the digital T(s) signal with a digital signal derived from the output of the HPA and for generating predistortion signals for modifying the T(s) signal applied to the input port of the HPA.
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17. A combination comprising:
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a high power amplifier (HPA) for transmitting an RF modulated signal, said HPA having an input port and an output port, and said HPA being subject to introducing distortions into the transmitted signals produced at its output port; means for receiving baseband signals; means responsive to said baseband signals for digitally up-converting the baseband signals and generating digital signals defining a digital RF waveform corresponding to the baseband signals, where this digital RF waveform is referred to herein as a T(s) signal; and a digital RF predistorter circuit having an input port, an output port and a control port; means for applying the T(s) signal to the signal input port of the digital RF predistorter; means for coupling the output port of the digital RF predistorter to the in put port of the HPA; and means for applying signals to the control port of the digital RF predistorter circuit operable at higher frequencies than the RF waveform for causing the digital RF predistorter circuit to directly operate on, and modify, consecutive the digital signals samples within said T(s) signal and for causing a modified T(s) signal to be applied to the input port of the HPA modifying the waveform on a point by point basis for linearizing the response of the HPA and reducing distortions in the transmitted signals. - View Dependent Claims (18, 19, 20, 21, 22)
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23. A combination comprising:
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a high power amplifier (HPA) for transmitting an RF modulated signal said amplifier having an input port and an output port, said amplifier being subject to introducing distortions into the transmitted signals; means for receiving digital baseband signals; digital up-converting means, including a local oscillator, responsive to said baseband signals for processing said baseband signals and generating digital signals defining a desired digital RF waveform T(s);
where T(s) is a digitally sampled signal at a predetermined frequency;digital predistorter circuitry having an input port, an output port and a control port; means for supplying the digital signals defining the desired digital RF waveform T(s) to the input port of the digital predistorter circuitry and means for supplying signals to the control port of the digital predistorter circuitry for modifying consecutive digital signal samples and modifying the waveform on a point by point by point basis for producing a predistorted digital RF waveform P(s)T(s) at the output port of the digital predistorter circuitry; and means for applying P(s)T(s) to the input port of the HPA for producing an output signal which tends to be a linear function of the baseband signals. - View Dependent Claims (24, 25, 26, 27, 28, 29)
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30. A combination comprising:
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a high power amplifier (HPA) for transmitting an RF modulated signal said amplifier having an input port and an output port, said HPA being subject to introducing distortions into the transmitted signals; means for receiving baseband signals; means responsive to said baseband signals for digitally up-converting the baseband signals and generating digital signals defining a corresponding digital RF waveform representation of the baseband signals, defined herein as T(s); and a digital RF predistorter circuit having an input port, an output port and a control port; and means for applying said T(s) signal to the input port of the digital RF predistorter circuit operable at much higher frequencies than the RF waveform and means for applying a signal representative of preselected characteristics of the HPA to the control port of the digital RF predistorter circuit for directly operating on, and modifying, consecutive digital signal samples of the T(s) signal and modifying the waveform on a point by point basis; and means for coupling the output port of the digital RF predistorter circuit to the input of the HPA for applying the modified signal to the input of the HPA and for linearizing the response of the HPA and minimizing distortions in the transmitted signal.
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Specification