Segregated spectrum RF downconverter for digitization systems
First Claim
1. An apparatus for digitizing an electromagnetic input signal having frequency components within at least first and second segregated frequency bands, comprising:
- a filtering circuit arrangement for passing only frequency components of said input signal substantially within said first and second frequency bands to provide a filtered signal having a spectrum with spectral components below a predetermined power level within a frequency gap between said first and second frequency bands; and
an analog to digital (A/D) converter for sampling said filtered signal at a sampling rate sufficient to provide a digitized output signal having a frequency spectrum including spectral components of said filtered signal at corresponding frequencies thereof, and with a replica of spectral components of one of said frequency bands appearing within said frequency gap.
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Accused Products
Abstract
Disclosed is an apparatus for digitizing an electromagnetic input signal having frequency components within at least first and second segregated frequency bands, particularly useful in a wireless communications system. The apparatus includes a filtering circuit arrangement for passing only frequency components of the input signal substantially within the first and second frequency bands, to provide a filtered signal having a spectrum with spectral components below a predetermined power level within a frequency gap between the first and second frequency bands. An analog to digital (A/D) converter samples the filtered signal at a sampling rate sufficient to provide a digitized output signal with a frequency spectrum corresponding to that of the filtered signal and also with a replica of spectral components of one of the frequency bands appearing within the frequency gap. Preferably, the sampling rate used is less than the Nyquist sampling rate for the composite frequency band extending from the lowest to highest frequencies of the two bands. This allows a single A/D converter to be employed to sample the filtered signal, even when a large frequency gap exists between the segregated bands. A single mixer stage can then be used in conjunction with the single A/D converter in a wireless communications receiver application.
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Citations
19 Claims
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1. An apparatus for digitizing an electromagnetic input signal having frequency components within at least first and second segregated frequency bands, comprising:
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a filtering circuit arrangement for passing only frequency components of said input signal substantially within said first and second frequency bands to provide a filtered signal having a spectrum with spectral components below a predetermined power level within a frequency gap between said first and second frequency bands; and an analog to digital (A/D) converter for sampling said filtered signal at a sampling rate sufficient to provide a digitized output signal having a frequency spectrum including spectral components of said filtered signal at corresponding frequencies thereof, and with a replica of spectral components of one of said frequency bands appearing within said frequency gap. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 14)
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11. In a wireless communications system including an antenna operable to receive a plurality of modulated radio frequency (RF) signals of a corresponding plurality of different frequency channels within at least first and second segregated RF frequency bands, said antenna operable to combine said RF signals to provide a frequency multiplexed input signal, a receiving apparatus for down-converting and digitizing said frequency multiplexed input signal, comprising:
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a single down-converting mixer for translating frequency components of said input signal to corresponding intermediate frequency (IF) frequency components, thereby producing an IF signal having first and second segregated IF bands associated with said first and second RF frequency bands; a filtering circuit arrangement for passing only frequency components of said IF signal substantially within said first and second frequency bands to provide a filtered IF signal having a spectrum with spectral components below a predetermined power level within a frequency gap between said first and second IF frequency bands; and an analog to digital (A/D) converter for sampling said filtered IF signal at a sampling rate sufficient to provide a digitized output signal having a frequency spectrum with corresponding spectral components of said filtered signal, and with a replica of spectral components of one of said IF frequency bands appearing within said frequency gap. - View Dependent Claims (12, 13, 15)
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16. A method for processing a frequency multiplexed analog input signal having frequency components within at least first and second non-contiguous frequency bands, comprising:
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filtering out frequency components of said input signal that are outside said non-contiguous frequency bands to provide a filtered signal having a frequency gap between said first and second frequency bands, said frequency gap defined by power spectral components below a predetermined threshold; and periodically sampling said filtered signal at a sampling rate sufficient to produce a digitally sampled output signal having a frequency spectrum including spectral components of said filtered signal at corresponding frequencies thereof, and also including a replica of spectral components of one of said frequency bands appearing within said frequency gap. - View Dependent Claims (17, 18, 19)
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Specification