The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
May. 29, 2001
Filed:
May. 12, 1998
Michel Darveau, Aylmer, CA;
Edgar Velez, Kanata, CA;
Nortel Networks Limited, Montreal, CA;
Abstract
A method and apparatus for filtering interference (e.g. transmitter feed-through and RF) in a modem receiver. The method of reducing transmitter feed-through (Tx-FT) interference at a receiver of a modem to obtain a desired receive (Rx) signal having a spectrum at a carrier frequency for input into a QAM demodulator includes attenuating the Tx-FT interference and passing the Rx signal at the carrier frequency using an analog filter. The output signal from the analog filter is converted to a digital representation by a analog-to-digital (ADC) converter. A digital band pass filter is used to pass the Rx signal at the carrier frequency and to attenuate the Tx-FT interference further. A mixer is then used to shift the carrier frequency of the spectrum of the Rx signal to an intermediate frequency. The mixer introduces at least one spectral transmitter feed-through image Tx-FT(I) and a receive signal image Rx(I). A digital low pass filter is used to pass the Rx signal at the intermediate frequency and attenuating the image spectrums Tx-FT(I) and Rx(I). A final decimation function is performed to downsample the Rx signal at a downsampling rate from the second digital filter to match the sampling rate of the QAM demodulator. Interference filtering is improved by dividing the functions between an analog filter prior to conversion and a pair of digital filters after conversion.