Coarse-Mixer Digital Down-Converter With Shared Decimation Filters
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Solution Overview
Problem
Existing digital down-converter (DDC) technologies require complex digital circuitry and high power consumption due to the need for multiple decimation filters and complex phasor operations, especially at high sampling rates, which increases power consumption and complexity.
Innovation Solution
A modified digital down-converter that employs a modified decimate-by-N filter, which filters and decimates the input signal before coarse mixing, eliminating the need for separate decimation filters for in-phase and quadrature components by using subfilters and combining their outputs into partial sums, reducing the number of multiplication operations required.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple decimation filters are used for I-phase and Q-phase components in each frequency band, then signal processing accuracy is improved, but device complexity and power consumption increase
Solution Approach 1:
The patent combines the decimation filter operations for both I-phase and Q-phase components into a single unified decimation filter. This is achieved by processing the complex signal (I+jQ) through one filter structure, thereby merging what were previously two separate filter paths into one, reducing device complexity while maintaining processing accuracy
Solution Approach 2:
The unified decimation filter is designed to perform the decimation function for both in-phase and quadrature components simultaneously. This multi-functional filter structure processes both signal components through a single device, eliminating the need for separate dedicated filters for each phase component
2Measurement precision
If complex phasor multiplication operations are performed at high sampling rates, then down-conversion accuracy is improved, but power consumption increases
Solution Approach 1:
The patent performs decimation (reducing sampling rate) before the coarse mixing operation. By preliminary reducing the sampling rate from the original high rate to a lower rate, the subsequent phasor multiplication operations are performed at fewer samples per second, thereby reducing total power consumption while maintaining down-conversion accuracy
Solution Approach 2:
The patent changes the sampling rate parameter from a high value to a lower value through the decimation process. This parameter change occurs before the mixing operation, allowing the same mixing accuracy to be achieved at a lower sampling rate, which directly reduces power consumption of the multiplication operations
3Measurement precision
If decimation is performed after coarse mixing, then down-conversion accuracy is improved, but device complexity increases due to requiring decimation filters for each frequency band
Solution Approach 1:
The patent performs the decimation action before the coarse mixing operation, reversing the traditional sequence. This preliminary decimation reduces the sampling rate first, and then mixing is performed on the already-decimated signal, maintaining accuracy while reducing the complexity of subsequent operations
Solution Approach 2:
The patent inverts the conventional order of operations by performing decimation before mixing instead of after mixing. This inversion of the processing sequence achieves the same down-conversion accuracy while avoiding the need for multiple decimation filters for different frequency bands
Data Source
AI summary
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.