DRM Receiver Programmable FFT Downsampling
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Solution Overview
Problem
Current DRM receivers face challenges in reducing computational complexity for demodulating DRM OFDM signals and designing separation filters to distinguish between closely transmitted analog AM and digital DRM signals, due to sub-optimal sampling rates and filter order requirements.
Innovation Solution
A DRM receiver system that employs an analog-to-digital converter for sampling at a specific rate, followed by downsampling and mode identification to determine the DRM mode, using a programmable N-point FFT for demodulation, and incorporates an analog and digital separation filter to separate DRM and AM signals, optimizing sampling frequencies and filter design.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If FFTW is used for demodulation with adaptive planning, then demodulation performance is improved, but computational complexity and processing time increase
Solution Approach 1:
The patent pre-calculates and stores optimal FFT parameters (window sizes, radix values, butterfly operations) for different DRM modes before actual demodulation. This preliminary preparation eliminates the need for runtime planning and adaptive optimization, allowing the receiver to directly apply pre-determined parameters during signal processing, thus reducing processing time while maintaining demodulation performance
Solution Approach 2:
The patent changes the approach from dynamic parameter adaptation to static parameter selection based on pre-defined DRM modes. By mapping each DRM mode to specific FFT parameters in advance, the system eliminates runtime parameter optimization overhead, achieving a balance between demodulation accuracy and processing efficiency
2Measurement precision
If a separation filter is designed to distinguish closely transmitted AM and DRM signals, then signal separation capability is improved, but filter order and complexity increase
Solution Approach 1:
The patent applies different filtering strategies to different signal components based on their characteristics. Instead of using a single high-order filter for all frequencies, the system employs selective filtering where specific filter parameters are applied only to the frequency ranges where AM and DRM signals overlap, reducing the overall filter order while maintaining separation capability
Solution Approach 2:
The patent segments the frequency spectrum into distinct regions for AM and DRM signals, applying targeted filtering only where necessary. By dividing the spectrum and applying filters selectively to overlapping regions rather than across the entire bandwidth, the system achieves effective signal separation with lower filter complexity
Data Source
AI summary
A Digitial Radio Mondiale (DRM) receiver and demodulation method includes a programmable downsampler and a programmable N-point Fast Fourier Transform (FFT) to recover and demodulate the OFDM symbols in a received DRM-encoded RF signal. The received signal is digitally sampled at a rate operably integer downsampled to achieve a number N samples in the useful portion of the OFDM symbol for input to an N-point FFT, where N equal to a power of two. The downsampling rate and size (N-points) of the FFT depend on the DRM encoding and transmission parameters, notably the robustness mode and spectrum occupancy. This reduces the processing/computational requirements and the design complexity of the DRM receiver.