METHODS AND APPARATUS FOR DYNAMICALLY COMPENSATING FOR DC OFFSET DRIFT AND OTHER PVT-RELATED SIGNAL VARIATIONS IN POLAR TRANSMITTERS
First Claim
1. A method of compensating for signal variations in a communications transmitter employing a switch-mode power amplifier (PA), comprising:
- identifying a predetermined signal characteristic in an input signal applied to an input of the switch-mode PA;
sampling a modulated signal containing the identified predefined signal characteristic produced at an output of said switch-mode PA to generate a digital sample representing an actual value of said identified predefined signal characteristic;
comparing said digital sample representing said actual value of said identified predetermined signal characteristic to a digital value representing an expected value; and
compensating for signal variations in said modulated signal based on the comparison of said digital sample representing said actual value to said digital value representing said expected value.
2 Assignments
0 Petitions
Accused Products
Abstract
Methods and apparatus for dynamically compensating for signal variations in communications transmitters employing switch-mode PAs. An exemplary method includes first identifying a predetermined signal characteristic in an input signal applied to an input of a switch-mode PA. A modulated signal produced at the output of the switch-mode PA containing the identified signal characteristic is then sampled at approximately the same time the identified signal characteristic appears at the output of the switch-mode PA, to generate a digital sample representing an actual value of the identified signal characteristic. An error signal representing the extent to which the actual value deviates from an expected value is then generated. Finally, the DC level and/or gain of the input signal to the switch-mode PA is modified to reduce the error. By reducing the error in this manner, signal variations that adversely affect the accuracy of the switch-mode PA output signal are dynamically compensated for.
71 Citations
24 Claims
-
1. A method of compensating for signal variations in a communications transmitter employing a switch-mode power amplifier (PA), comprising:
-
identifying a predetermined signal characteristic in an input signal applied to an input of the switch-mode PA; sampling a modulated signal containing the identified predefined signal characteristic produced at an output of said switch-mode PA to generate a digital sample representing an actual value of said identified predefined signal characteristic; comparing said digital sample representing said actual value of said identified predetermined signal characteristic to a digital value representing an expected value; and compensating for signal variations in said modulated signal based on the comparison of said digital sample representing said actual value to said digital value representing said expected value. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
-
-
10. A polar transmitter, comprising:
-
a baseband processor configured to generate a digital amplitude modulation (AM) data stream, generate a digital phase modulation (PM) data stream, and identify samples in said digital AM data stream representing a predetermined signal characteristic; a first digital-to-analog converter (DAC) configured to generate an analog AM signal having the predetermined signal characteristic from said digital AM data stream; a second DAC configured to generate an analog PM signal from said PM data stream; an amplitude modulator configured to receive said analog AM signal and generate an amplitude modulated power supply signal; a phase modulator configured to receive said analog PM signal and generate a phase-modulated carrier signal; a switch-mode power amplifier (PA) having a first input configured to receive an amplitude modulated power supply signal, a second input configured to receive a phase modulated signal, and an output configured to provide an amplitude- and phase-modulated output signal; and a compensation loop coupled between the output of the switch-mode PA and an input of said baseband processor operable to generate a digital sample of said amplitude- and phase-modulated output signal at approximately the same time said predetermined signal characteristic has propagated from said first DAC and arrived at the output of said switch-mode PA, said digital sample representing an actual value of said signal characteristic at the output of said switch-mode PA, wherein said baseband processor is configured to modify the analog AM signal, based on the actual value represented by said digital sample to compensate for signal variations that affect an envelope accuracy of a signal envelope of said amplitude- and phase-modulated output signal. - View Dependent Claims (11, 12, 13, 14, 15, 16, 17, 18, 19)
-
-
20. A switch-mode power amplifier (PA) apparatus, comprising:
-
a switch-mode PA having an input configured to receive an input signal with a predetermined signal characteristic and an output configured to provide an output signal containing said predetermined signal characteristic; and a circuit coupled to the output of said switch-mode PA configured to sample said output signal at approximately the same time said predetermined signal characteristic appears at the output of said switch-mode PA. - View Dependent Claims (21, 22, 23, 24)
-
Specification