HIGH EFFICIENCY DIGITAL TRANSMITTER INCORPORATING SWITCHING POWER SUPPLY AND LINEAR POWER AMPLIFIER
First Claim
1. A method of improving power efficiency of a transmitter having a linear power amplifier, said method comprising the step of:
- generating a reduced bandwidth envelope signal for input to a switched mode power supply, the output of said switched mode power supply applied to the supply input of said linear power amplifier; and
wherein said linear power amplifier is operated in a non-saturated mode.
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Accused Products
Abstract
A novel apparatus and method of improving the power efficiency of a digital transmitter for non-constant-amplitude modulation schemes. The power efficiency improvement mechanism of the invention leverages the high efficiency of a switched-mode power supply (SMPS) that supplies the high DC current to the transmitter'"'"'s power amplifier, while compensating for its limitations using predistortion. The predistortion may be achieved using any suitable technique such as digital signal processing, hardware techniques, etc. A switched mode power supply (i.e. switching regulator) is used to provide a slow form (i.e. reduced bandwidth) of envelope tracking (based on a narrower bandwidth distorted version of the envelope waveform) such that the switching regulator can use a lower switching rate corresponding to the lower bandwidth, thereby obtaining high efficiency in the switching regulator. The resulting AM-AM and AM-PM distortions in the power amplifier are compensated through predistortion of the digital amplitude modulating signal which dictates the envelope at the PA input. Similarly, the phase modulation is also compensated prior to the PA, such that once it undergoes the distortion in the PA, the end result is sufficiently close to the desired phase.
328 Citations
35 Claims
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1. A method of improving power efficiency of a transmitter having a linear power amplifier, said method comprising the step of:
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generating a reduced bandwidth envelope signal for input to a switched mode power supply, the output of said switched mode power supply applied to the supply input of said linear power amplifier; and wherein said linear power amplifier is operated in a non-saturated mode. - View Dependent Claims (2, 3, 4, 5, 6)
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7. A method of improving power efficiency of a transmitter having a linear power amplifier, said method comprising the steps of:
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generating a reduced bandwidth envelope signal for input to a switched mode power supply, the output of said switched mode power supply applied to the supply input of said linear power amplifier, wherein said linear power amplifier is operated in a non-saturated mode; and compensating for power supply dependent distortions in said linear power amplifier to yield a substantially linear output therefrom. - View Dependent Claims (8, 9, 10, 11, 12, 13, 14, 15, 16, 17)
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18. A method of improving power efficiency of a transmitter incorporating a linear power amplifier and switching regulator, said method comprising the steps of:
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generating a slowed envelope tracking signal such that a switching rate corresponding to a lower bandwidth than that of a signal input to said linear power amplifier can be used by said switching regulator; pre-distorting an amplitude modulating signal input that determines the envelope at the power amplifier; and wherein said linear power amplifier is operated in a non-saturated mode of operation. - View Dependent Claims (19, 20, 21)
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22. A method of improving the power efficiency of a transmitter incorporating a linear power amplifier and switching regulator, said method comprising the steps of:
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generating a reduced bandwidth envelope tracking signal input to said switching regulator such that a switching rate corresponding to a lower bandwidth than that of a signal input to said linear power amplifier can be used, the output of said switching regulator input to the supply input of said linear power amplifier; and pre-distorting the input to said power amplifier to compensate for supply-headroom dependent distortions in said power amplifier. - View Dependent Claims (23)
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24. An apparatus for improving the efficiency of a digital transmitter incorporating a switching power supply and a linear power amplifier, comprising:
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an envelope-tracking band limited signal generator operative to generate a band-limited envelope regulator control signal input to said switching power supply; and wherein said linear power amplifier is operated in a non-saturated mode of operation. - View Dependent Claims (25, 26, 27, 28)
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29. A power efficient transmitter, comprising:
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a transmit chain operative to generate an output transmit signal in accordance with a signal input thereto; a switched mode power supply; a linear power amplifier operated in a non-saturated mode; and an envelope-tracking band limiter operative to generate a band-limited envelope control signal input to said switched mode power supply. - View Dependent Claims (30, 31, 32, 33)
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34. A radio, comprising:
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a phase locked loop; a transmitter coupled to said phase locked loop, said transmitter comprising; a transmit chain operative to generate a output transmit signal in accordance with a signal input thereto; a switched mode power supply; a linear power amplifier operated in a non-saturated mode; an envelope-tracking band limited signal generator operative to generate a band-limited envelope regulator control signal input to said switched mode power supply; a receiver coupled to said phase locked loop; and a baseband processor coupled to said transmitter and said receiver. - View Dependent Claims (35)
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Specification