DC offset reduction in a zero-if transmitter
First Claim
Patent Images
1. An apparatus comprising:
- a zero-IF transmitter having a feedback loop and having a DC offset, representative of a carrier feedthrough signal;
a successive approximation register, operatively coupled to the zero-IF transmitter, arranged and constructed external to the feedback loop to successively approximate a value to correct the DC offset; and
a summer, within the feedback loop of the zero-IF transmitter and operatively coupled to the successive approximation register, for adding the value to a desired input to reduce the DC offset.
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Abstract
A zero-IF transmitter (200) has a DC offset, representative of a carrier feedthrough signal. A value to correct the DC offset is successively approximated (207). A summer (201) adds the value to a desired input to reduce the DC offset.
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Citations
20 Claims
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1. An apparatus comprising:
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a zero-IF transmitter having a feedback loop and having a DC offset, representative of a carrier feedthrough signal; a successive approximation register, operatively coupled to the zero-IF transmitter, arranged and constructed external to the feedback loop to successively approximate a value to correct the DC offset; and a summer, within the feedback loop of the zero-IF transmitter and operatively coupled to the successive approximation register, for adding the value to a desired input to reduce the DC offset. - View Dependent Claims (2, 3, 4, 5, 6)
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7. A method of correcting DC offset in a zero-IF transmitter, comprising the steps of:
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opening a feedback loop in the zero-IF transmitter; successively approximating a value to correct the DC offset; and adding the value to a desired input to reduce the DC offset. - View Dependent Claims (8, 9, 10, 11)
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12. A method of correcting DC offset in a zero-IF transmitter, comprising the steps of:
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in a transmitter having a feedback loop and at least one amplifier in a forward path of the feedback loop, opening the feedback loop by driving the at least one amplifier'"'"'s gain to substantially zero; successively approximating a value to correct the DC offset; closing the feedback loop by driving the at least one amplifier'"'"'s gain to a nominal operating value. - View Dependent Claims (13, 14)
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15. An apparatus comprising:
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a zero-IF transmitter having a DC offset and having a feedback loop that has a return path; a summer, within the feedback loop of the zero-IF transmitter, having a first summer input coupled to an input signal, a second summer input coupled to the return path of the feedback loop , a third summer input and a summer output; a successive approximation register (SAR), having an SAR input operatively coupled to the summer output and an SAR output operatively coupled to the third summer input wherein the SAR is arranged and constructed to successively approximate a value to reduce the DC offset. - View Dependent Claims (16, 17, 18, 19)
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20. A method of correcting DC offset in a zero-IF transmitter having a Cartesian feedback loop and a training feedback loop, comprising the steps of:
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opening the training feedback loop in the zero-IF transmitter; successively approximating a value to correct the DC offset within the training feedback loop; adding the value to attenuate the DC offset within the training feedback loop; closing the training feedback loop in the zero-IF transmitter; and integrating DC offset within the Cartesian feedback loop, thereby attenuating the DC offset within the Cartesian feedback loop.
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Specification