Integrated demodulator, filter and decimator (DFD) for a radio receiver
First Claim
1. A method for use in a radio receiver, comprising the steps of:
- translating a received radio frequency (RF) signal to an intermediate frequency (IF) signal;
converting the IF signal to a stream of digital samples using a sampling frequency that is four times the IF;
dividing the stream of digital samples into a first set of even samples and a second set of odd samples;
digitally demodulating the stream of digital samples to produce a complex signal with real (I) and imaginary (Q) components at one half of the sampling frequency using two parallel quadrature demodulators with a first quadrature demodulator demodulating only the first set of even samples and a second quadrature demodulator only demodulating the second set of odd samples;
delaying the second set of odd samples by one time period of the sampling frequency; and
filtering the demodulated first set of even samples using a first set of coefficients of a digital filter and the delayed demodulated second set of odd samples using a second set of coefficients of the digital filter to produce a baseband complex signal, the filtering implementing an N-tap finite impulse response (FIR) filter, where N is a positive integer, using block digital filtering with two parallel filtering paths with one of the filtering paths operating at one half of the sampling frequency on the first set of even samples using even coefficients of the N-tap FIR filter and the other of the filtering paths operating at one half of the sampling frequency on the second set of odd samples using odd coefficients of the N-tap FIR filter.
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Accused Products
Abstract
A superheterodyne receiver includes an A/D converter for converting an IF signal to a stream of samples at a sampling frequency that is four times the IF and a splitter that splits the stream of samples into a first set of even samples and a second set of odd samples. A first quadrature demodulator demodulates just the first set of even samples to produce one of real (I) and imaginary (Q) components of a complex signal at one half of the sampling frequency, and a second, parallel quadrature demodulator demodulates just the second set of odd samples to produce the other of the I and Q components. The demodulated first set is filtered using a first subset of filter coefficients, and the demodulated second set is filtered using a second subset of filter coefficients. The filter outputs correspond to a baseband complex signal. The technology disclosed reduces overall hardware complexity and operating frequency by a factor of two or more.
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Citations
23 Claims
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1. A method for use in a radio receiver, comprising the steps of:
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translating a received radio frequency (RF) signal to an intermediate frequency (IF) signal; converting the IF signal to a stream of digital samples using a sampling frequency that is four times the IF; dividing the stream of digital samples into a first set of even samples and a second set of odd samples; digitally demodulating the stream of digital samples to produce a complex signal with real (I) and imaginary (Q) components at one half of the sampling frequency using two parallel quadrature demodulators with a first quadrature demodulator demodulating only the first set of even samples and a second quadrature demodulator only demodulating the second set of odd samples; delaying the second set of odd samples by one time period of the sampling frequency; and filtering the demodulated first set of even samples using a first set of coefficients of a digital filter and the delayed demodulated second set of odd samples using a second set of coefficients of the digital filter to produce a baseband complex signal, the filtering implementing an N-tap finite impulse response (FIR) filter, where N is a positive integer, using block digital filtering with two parallel filtering paths with one of the filtering paths operating at one half of the sampling frequency on the first set of even samples using even coefficients of the N-tap FIR filter and the other of the filtering paths operating at one half of the sampling frequency on the second set of odd samples using odd coefficients of the N-tap FIR filter. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. Apparatus for use in a superheterodyne radio receiver chain, where the radio receiver chain includes an analog-to-digital converter for converting an intermediate frequency (IF) signal to a stream of digital samples at a sampling frequency that is four times the IF, the apparatus comprising:
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a splitter configured to split the stream of digital samples into a first set of even samples and a second set of odd samples; a first quadrature demodulator configured to demodulate only the first set of even samples to produce one of real (I) and imaginary (Q) components of a complex signal at one half of the sampling frequency; a second quadrature demodulator configured to operate in parallel with the first quadrature demodulator to demodulate only the second set of odd samples to produce the other of the I and Q components of the complex signal at one half of the sampling frequency; a first digital filter configured to filter the demodulated first set of even samples using a first set of coefficients; and a second digital filter configured to filter the demodulated second set of odd samples using a second set of coefficients, wherein; the output of the first and second digital filters corresponds to a baseband complex signal, the first and second filters are finite impulse response (FIR) filters used to implement an N-tap FIR filter, where N is a positive integer, with one of the first and second filters being configured to operate at one half of the sampling frequency on the first set of even samples using even coefficients of the N-tap FIR filter and the other of the first and second filters configured to operate at one half of the sampling frequency on the second set of odd samples using odd coefficients of the N-tap FIR filter, and one of the first and second FIR filters includes a delay is configured to delay the second set of odd samples by one time period of the sampling frequency prior to filtering. - View Dependent Claims (10, 11, 12, 13, 14, 15, 16, 17, 18)
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19. An integrated demodulator, filter, and decimator for use in a superheterodyne radio receiver chain, where the radio receiver chain includes an analog-to-digital converter for converting an intermediate frequency (IF) signal to a stream of digital samples at a sampling frequency that is four times the IF and a splitter that splits the stream of digital samples into a first set of even samples and a second set of odd samples, the integrated demodulator, filter, and decimator consisting essentially of:
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a first quadrature demodulator configured to demodulate the first set of even samples to produce one of a real (I) and imaginary (Q) components of a complex signal at one half of the sampling frequency; a second quadrature demodulator configured to operate in parallel with the first quadrature demodulator to demodulate the second set of odd samples to produce the other of the I and Q components of the complex signal at one half of the sampling frequency; a first digital filter configured to filter the demodulated first set of even samples using a first set of coefficients; and a second digital filter configured to filter the demodulated second set of odd samples using a second set of coefficients, wherein; the output of the first and second digital filters corresponds to a baseband complex signal, the first and second filters are finite impulse response (FIR) filters used to implement an N-tap FIR filter, where N is a positive integer, with one of the first and second filters being configured to operate at one half of the sampling frequency on the first set of even samples using even coefficients of the N-tap FIR filter and the other of the first and second filters configured to operate at one half of the sampling frequency on the second set of odd samples using odd coefficients of the N-tap FIR filter, and one of the first and second FIR filters includes a delay is configured to delay the second set of odd samples by one time period of the sampling frequency prior to filtering. - View Dependent Claims (20, 21, 22, 23)
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Specification