Bluetooth PRBS Modulation for Spectral Spur Reduction
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Solution Overview
Problem
Bluetooth Low Energy (BLE) transmissions with longer reach modulations, such as Bluetooth Long Range (BLR), experience reduced transmit power due to spectral spurs caused by repetition coding, which limits the link power budget and fails to comply with regulatory standards for RF emissions.
Innovation Solution
Applying a pseudo random bit sequence (PRBS) to the repetition coding in BLR transmissions and using a carrier modifier to spread the spectral energy, thereby reducing narrowband RF spectral energy and increasing transmit power levels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If repetition coding is used in BLR transmission to extend link range, then the link power budget is improved, but spectral spurs are generated that cause non-compliance with RF emission standards
Solution Approach 1:
The patent applies a pseudo-random bit sequence (PRBS) to the repetition coded symbols, changing the statistical parameters of the transmitted signal. This randomization transforms the deterministic repeating pattern into a statistically random sequence, which spreads the spectral energy and eliminates the narrowband spurs while preserving the extended link range benefit of repetition coding
Solution Approach 2:
The patent introduces a pseudo-random sequence as an intermediary element between the data bits and the transmitted signal. This intermediary sequence modulates the repetition coded symbols, acting as a spreading code that distributes the spectral energy across a wider bandwidth and prevents concentration at specific frequencies
2Object-generated harmful factors
If transmit power is reduced to satisfy spectral mask requirements, then RF emission compliance is improved, but the overall transmit energy and link power budget are reduced
Solution Approach 1:
By changing the temporal and spectral parameters of the transmitted signal through PRBS modulation, the patent redistributes the spectral energy density. This allows the signal to maintain higher total transmit power while keeping the spectral density within mask limits at any given frequency, thereby preserving transmit energy budget
3Device complexity
If repetition coding with fixed patterns is used, then encoding simplicity is maintained, but stationary spectral energy increases causing narrowband peaks
Solution Approach 1:
The patent modifies the coding parameters by XORing the repetition coded symbols with a pseudo-random sequence. This simple operation changes the spectral characteristics from stationary to time-varying, eliminating narrowband peaks while adding minimal computational complexity compared to the base repetition coding scheme
Data Source
AI summary
A bitstream modifier is operative on a packet which uses repetition coding. The bitstream modifier increases randomness of the data in a deterministic manner such that spectral spurs from repetition coding are greatly reduced, thereby providing greater available transmit power. In another example of the invention, baseband samples of a header and/or payload for a Bluetooth packet are modified by a canonical sequence with a low slew rate for data such that the variations in frequency may be tracked by a receiver and the transmitted spectral spurs reduced.