Digital RF Signal Transport via Dynamic Resampling
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Solution Overview
Problem
Current distributed communications systems face inefficiencies in utilizing serial link bandwidth due to the need for different sample rates for analog-to-digital (A/D) and digital-to-analog (D/A) converters, which is costly and difficult to implement, especially in interfacing with various carriers.
Innovation Solution
Implementing a 'flex-band' approach by re-sampling digitized signals at a selected rate based on factors like bandwidth, allowing for efficient bandwidth utilization without requiring specialized converters, using re-sampling devices that can change sample rates through rational relationships and filtering to prevent aliasing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If different sample rates are used for A/D and D/A converters to match carrier bandwidth requirements, then serial link bandwidth utilization is improved, but device complexity and cost increase due to requiring specialized programmable converters and frequency synthesizers
Solution Approach 1:
The patent applies dynamics by making the sample rate adjustable rather than fixed. The system dynamically changes the sample rate based on the specific carrier bandwidth requirements, allowing the same hardware to adapt to different communication standards (e.g., GSM, CDMA, WCDMA) without physical reconfiguration.
Solution Approach 2:
The patent changes the sampling rate parameter to optimize bandwidth utilization. By adjusting this key parameter according to the carrier type and bandwidth requirements, the system achieves efficient serial link usage while maintaining a single standardized converter design, avoiding the need for multiple specialized converters.
2Adaptability or versatility
If programmable frequency synthesizers are used to generate different sample rates, then adaptability to different carriers is improved, but phase noise increases and cost increases
Solution Approach 1:
The patent extracts the frequency synthesis function from the A/D and D/A converters and places it in a separate, dedicated frequency synthesizer module. This separation allows the converters to operate at fixed, optimized sample rates while the external synthesizer handles the frequency adaptation, reducing phase noise impact on the conversion process.
Solution Approach 2:
The patent introduces a frequency synthesizer as an intermediary component that bridges the gap between the fixed-rate converters and the variable-rate carrier requirements. This intermediary generates the appropriate sample rate signals without requiring the converters themselves to be programmable, thereby maintaining converter reliability while achieving adaptability.
3Reliability
If programmable anti-aliasing filters are used to prevent aliasing at different bandwidths, then signal integrity is improved, but manufacturing complexity and cost increase
Solution Approach 1:
The patent segments the signal processing function by separating the anti-aliasing filtering from the frequency synthesis. Instead of using a single programmable filter that must be reconfigured for each carrier, the system uses fixed filters designed for specific bandwidths, with the frequency synthesizer handling the rate adaptation. This segmentation simplifies manufacturing while maintaining signal integrity.
Data Source
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AI summary
A communication device (100, 200) for use within a communication system comprises: re-sampling circuitry (108a, 108b, 108n, 210a, 210b, 210c, 210n) configured to output re-sampled digital downlink signals by re-sampling digital downlink signals at resample rates (110a, 110b, 110n) based on at least one factor, the re-sampled digital downlink signals having a smaller bandwidth than the digital downlink signals; and framing circuitry (128, 214) configured to multiplex the re-sampled digital downlink signals and to generate a first frame that includes the re-sampled digital downlink signals as framed data for transport to one or more remotely located communication devices (101, 201) of the communication system, wherein the one or more remotely located communication devices (101, 201) of the communication system are configured to transmit radio frequency signals using at least one antenna, wherein the transmitted radio frequency signals are derived from the framed data of the first frame received from the communication device (100, 200).