Compensating pre-filter for an OFDM transmitter
First Claim
1. A method of generating a filtered analog transmission signal for transmission to a remote device, wherein the filtered analog transmission signal comprises multiple frequency components, the method comprising:
- generating a modulated multi-frequency signal stream from digital frequency-domain samples input to a modulator;
filtering the modulated multi-frequency signal stream using one or more filters to suppress out-of-band spectral components from the filtered analog transmission signal, said one or more filters collectively having a frequency-domain response over the multiple frequency components comprising a first maximum error relative to a desired frequency response; and
pre-compensating one or more of the digital frequency-domain samples using a pre-compensation unit such that a collective frequency-domain response of the pre-compensation unit and the one or more filters comprises a second maximum error relative to the desired frequency response less than the first maximum error.
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Abstract
A method and apparatus for reducing group delay and/or amplitude errors applied to a transmission signal by one or more transmission filters is described herein. The present invention characterizes the errors introduced by one or more transmission filters relative to a desired frequency response, e.g., the group delay and/or amplitude errors relative to a flat group delay and flat amplitude, respectively. Based on the errors, the present invention pre-compensates the digital frequency domain samples used to generate the transmission signal. In so doing, the present invention reduces the errors in the filtered transmission signal without placing limits on the design of the transmission filters.
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Citations
22 Claims
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1. A method of generating a filtered analog transmission signal for transmission to a remote device, wherein the filtered analog transmission signal comprises multiple frequency components, the method comprising:
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generating a modulated multi-frequency signal stream from digital frequency-domain samples input to a modulator; filtering the modulated multi-frequency signal stream using one or more filters to suppress out-of-band spectral components from the filtered analog transmission signal, said one or more filters collectively having a frequency-domain response over the multiple frequency components comprising a first maximum error relative to a desired frequency response; and pre-compensating one or more of the digital frequency-domain samples using a pre-compensation unit such that a collective frequency-domain response of the pre-compensation unit and the one or more filters comprises a second maximum error relative to the desired frequency response less than the first maximum error. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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12. A wireless transceiver configured to generate a filtered analog transmission signal for transmission to a remote device, wherein the filtered analog transmission signal comprises multiple frequency components, the wireless transceiver comprising:
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a modulator to generate a modulated multi-frequency signal stream from digital frequency-domain samples input to the modulator; one or more filters to filter the modulated multi-frequency signal stream to suppress out-of-band spectral components from the filtered analog transmission signal, said one or more filters collectively having a frequency-domain response over the multiple frequency components comprising a first maximum error relative to a desired frequency response; and a pre-compensation unit configured to pre-compensate one or more of the digital frequency-domain samples such that a collective frequency-domain response of the pre-compensation unit and the one or more filters comprises a second maximum error relative to the desired frequency response less than the first maximum error. - View Dependent Claims (13, 14, 15, 16, 17, 18, 19, 20, 21, 22)
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Specification