Methods and apparatus for reducing the effects of DAC images in radio frequency transceivers
First Claim
1. A transceiver, comprising:
- a transmitter portion including a digital-to-analog converter (DAC);
a receiver portion configured to receive RF signals in a receive frequency band; and
a variable rate clock generator operable to control said DAC,wherein the rate of a variable rate clock provided by the variable rate clock generator is adjustable so that an upconverted version of a DAC image created by said DAC is shifted in frequency away from frequencies within said receive frequency band.
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Accused Products
Abstract
Methods and apparatus for reducing the effects of digital-to-analog converter (DAC) images and transmission spurious effects in a receive frequency band of a radio frequency (RF) transceiver. A transceiver apparatus includes a transmitter portion having a DAC, a receiver portion configured to receive RF signals in a receive frequency band, and a variable rate clock generator. The variable rate clock generator is used to provide an oversampling clock for the DAC. The rate of the oversampling clock is adjustable and is selected so that an upconverted version of a DAC image created by the DAC is steered away from frequencies within the receive frequency band. A notch-effect low-pass filter (NELPF) may also, or alternatively, be used in the transceiver to reduce transmission spurious effects in the receive frequency band.
31 Citations
21 Claims
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1. A transceiver, comprising:
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a transmitter portion including a digital-to-analog converter (DAC); a receiver portion configured to receive RF signals in a receive frequency band; and a variable rate clock generator operable to control said DAC, wherein the rate of a variable rate clock provided by the variable rate clock generator is adjustable so that an upconverted version of a DAC image created by said DAC is shifted in frequency away from frequencies within said receive frequency band. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. A method of processing signals in a transceiver, comprising:
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receiving a digital baseband signal from a digital source; converting the digital baseband signal to an analog baseband signal according to an adjustable oversampling clock; and upconverting the analog baseband signal to a radio frequency (RF) signal, wherein converting the digital baseband signal to an analog baseband signal includes adjusting the rate of the adjustable oversampling clock so that an image created by the conversion process does not fall within a receive frequency band when the image is upconverted to RF by the upconversion process. - View Dependent Claims (10, 11, 12)
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13. A transceiver capable of transmitting and receiving in different transmit and frequency bands, comprising:
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a polar modulation transmitter having a magnitude path and a phase path, at least one of said magnitude and phase paths having a digital-to-analog converter (DAC) configured to receive digital baseband signals from a digital source; a receiver that can be configured to receive radio frequency (RF) signals in any one of several possible receive frequency bands; and an oversampling clock generator operable to provide an oversampling clock to a clock input of said DAC, wherein the oversampling clock provided by the oversampling clock generator is adjustable so that a DAC image created by the DAC and upconverted to RF is shifted away from the receive frequency band in which the receiver is configured to receive. - View Dependent Claims (14, 15, 16)
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17. A mobile communication device, comprising:
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baseband circuitry operable to generate digital symbols; a transmitter having a digital-to-analog converter (DAC) that is operable to convert the digital symbols to analog signals; a receiver configured to receive RF signals in one or more receive frequency bands; and means for frequency shifting an upconverted version of a DAC image created by the DAC to a frequency region that does not substantially overlap with a receive frequency band in which the receiver is configured to receive. - View Dependent Claims (18, 19, 20)
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21. A transceiver, comprising:
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a transmitter portion including a digital-to-analog converter (DAC); a receiver portion configured to receive RF signals in a receive frequency band; and a variable rate clock generator operable to control said DAC, wherein the rate of a variable rate clock provided by the variable rate clock generator is determined based on an operating band of a standard the transceiver is currently configured to operate in.
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Specification