DRM Receiver Analog Digital Separation Filter
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Solution Overview
Problem
Current DRM receivers face high computational complexity due to non-power of two sampling in OFDM symbol portions and difficulty in designing separation filters for coexisting analog and digital signals, especially in simulcast modes.
Innovation Solution
A DRM receiver system that samples RF signals at a frequency of 384 KHz times n, where n is an integer, and uses a programmable N-point FFT with N equal to a power of two, along with an analog and digital separation filter to demodulate DRM-encoded signals and separate them from analog signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If non-power of two sampling is used in OFDM symbol portions, then DRM signal processing can be performed, but computational complexity increases
Solution Approach 1:
The patent changes the sampling rate parameter to be a multiple of 384 KHz, which enables the OFDM symbol to contain an integer number of samples that is a power of two. This parameter change allows the use of efficient power-of-two FFT algorithms while maintaining compatibility with various DRM robustness modes (A, B, C, D) and spectrum occupancy modes (9, 10, 18, 20 KHz).
Solution Approach 2:
The patent introduces a programmable downsampler that can dynamically adjust the downsampling rate based on the detected DRM mode. The downsampler rate is selected from a set of predetermined rates (first, second, third, fourth rates) corresponding to different robustness and spectrum occupancy modes, allowing the system to adaptively optimize computational efficiency for each specific mode while maintaining power-of-two FFT compatibility.
2Reliability
If separation filters are designed for coexisting analog and digital signals in simulcast modes, then signal separation is achieved, but filter design difficulty increases
Solution Approach 1:
The patent changes the sampling rate to a multiple of 384 KHz, which creates a more favorable sampling frequency for filter design. This parameter change results in a lower filter order requirement while maintaining the ability to separate analog and digital signals in simulcast modes, thereby reducing filter design complexity.
Solution Approach 2:
The patent designs a universal separation filter that can handle multiple DRM robustness modes (A, B, C, D) and spectrum occupancy modes (9, 10, 18, 20 KHz) with a single filter structure. The filter is designed to work across different simulcast configurations without requiring mode-specific filter designs, simplifying the overall system architecture.
3Device complexity
If lower filter order is used for separation, then filter design is simplified, but signal separation performance in close frequency proximity may deteriorate
Solution Approach 1:
The patent changes the sampling rate parameter to a multiple of 384 KHz, which improves the frequency resolution and spectral distribution of the sampled signal. This parameter change allows lower order filters to achieve the same separation performance by better aligning the spectral components with the filter's passband and stopband characteristics.
Solution Approach 2:
The patent performs preliminary signal processing steps including downsampling and mode detection before applying the separation filter. By preparing the signal in advance and selecting the appropriate downsampling rate based on the detected DRM mode, the system optimizes the input signal characteristics for the separation filter, enabling it to achieve high separation performance with lower order.
Data Source
AI summary
A Digital Radio Mondiale (DRM) receiver and demodulation method includes an analog and digital separation filter for filtering and separating a DRM-encoded signal and a non DRM-encoded signal from a composite RF signal received at the receiver. The DRM receiver 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. The structure and operation of the receiver in this manner simplifies the design and reduces the required filter order of the analog and digital separation filter.