US 11,695,602 B2 · Filtered coarse mixer based digital down-converter for RF sampling ADCs

Abstract

A digital down converter (DDC) that improves efficiency by taking advantage of the periodicity of the coarse mixing process and the memory inherent in the convolution operation performed by decimation filters. In embodiments, the DDC filters and decimates a received signal to generate subfilter outputs and coarse mixes the subfilter outputs for each frequency band of interest. Accordingly, the DDC eliminates the need for separate decimation filters for each of the in-phase (I-phase) and quadrature (Q-phase) signals of each frequency band. In some embodiments, for each frequency band, the DDC combines the subfilter outputs into partial sums for each of the I- and Q-phases. In some of those embodiments, the coarse mixing operation is performed by multiplying the partial sums by real multiplicands and performing a simple post-rotation operation. In those embodiments, the DDC significantly reduces the number of multiplication operations required to perform the coarse mixing process.

Claims21

Dependent claims

A digital down converter (DDC) operable to down-convert a received signal having a frequency band of interest centered around a center frequency, the DDC comprising:

a decimation filter including a plurality of multipliers, each multiplier operable to filter an input sample by a filter coefficient, the plurality of multipliers being arranged to form a plurality of subfilters, each subfilter being operable to generate a subfilter output;
frequency partition circuitry operable to identify an integer based on the center frequency;
a coarse mixer, coupled to the decimation filter and the frequency partition circuitry, operable to down-convert the subfilter outputs by a coarse frequency proportional to the integer;
and
a fine mixer, coupled to the coarse mixer and the frequency partition circuitry, operable to shift the down-converted subfilter outputs from the coarse mixer by a residual frequency difference.

2 more elements

A method of down-converting a received signal having a frequency band of interest centered around a center frequency, the method comprising:

filtering and decimating input samples of the received signal, by a decimation filter comprising a plurality of multipliers, each multiplier operable to filter an input sample of the received signal by a filter coefficient, the plurality of multipliers being arranged to form a plurality of subfilters;
generating a subfilter output by each subfilter of the decimation filter;
identifying, by a frequency partition circuit, an integer based on the center frequency;
down-converting, by a course mixer, the subfilter outputs by a coarse frequency that is proportional to the integer to form a coarse mixed signal;
and
shifting a frequency of the coarse mixed signal by a residual frequency difference.

3 more elements

A system operable to down-convert a received signal having a first frequency band of interest centered around a first center frequency and a second frequency band of interest centered around a second center frequency, the system comprising:

a decimation filter comprising a plurality of multipliers, each multiplier operable to filter an input sample by a filter coefficient, the plurality of multipliers being arranged to form a plurality of subfilters, each subfilter being operable to generate a subfilter output;
frequency partition circuitry operable to identify a first integer based on the first center frequency and a second integer based on the second center frequency;
a first coarse mixer, coupled to the decimation filter and the frequency partition circuitry, operable to down-convert the subfilter outputs by a first coarse frequency that is proportional to the first integer;
a first fine mixer, coupled to the first coarse mixer and the frequency partition circuitry, operable to shift the down-converted subfilter outputs from the first coarse mixer a first residual frequency difference;
a second coarse mixer, coupled to the decimation filter and the frequency partition circuitry, operable to down-convert the subfilter outputs by a second coarse frequency that is proportional to the second integer;
and
a second fine mixer, coupled to the second coarse mixer and the frequency partition circuitry, operable to shift the down-converted subfilter outputs from the second coarse mixer by a second residual frequency difference.

4 more elements

Dependencies are inferred from the claim text.

Filtered coarse mixer based digital down-converter for RF sampling ADCs

Life of this patent

Filtered coarse mixer based digital down-converter for RF sampling ADCs

Life of this patent

Abstract

Claims21