Random Edge Injection Locking Circuit for Spur Suppression
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Solution Overview
Problem
Existing injection-locked digital phase locked loops (IL-DPLLs) in Bluetooth Low Energy (BLE) technology face issues with high reference spur and fractional spur due to periodic errors and timing errors between the injection path and PLL path, which are not effectively addressed by current solutions.
Innovation Solution
A circuit and method for random edge injection locking using a digitally controlled delay line and a pulse generator to inject pulses at different phases of the oscillator, breaking repeating patterns and compensating for phase differences to suppress spurs, implemented in a cost-effective manner with smaller area oscillators.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If injection pulses are injected to a fixed phase of the oscillator, then the injection locking is simple to implement, but reference spur and fractional spur are generated due to periodic errors
Solution Approach 1:
The patent applies dynamics by making the injection phase variable rather than fixed. The delay line continuously adjusts the phase of injection pulses based on the phase difference between the oscillator output and reference signal, transforming the static fixed-phase injection into a dynamic adaptive process that eliminates periodic errors causing spurs
Solution Approach 2:
The patent implements feedback by detecting the phase difference between the oscillator output and reference signal, then using this information to adjust the delay line accordingly. This closed-loop feedback mechanism ensures that injection pulses are always applied at the optimal phase to minimize spurious signals while maintaining locking
2Object-generated harmful factors
If a delay line is used to adjust injection phase dynamically, then reference spur and fractional spur are reduced, but device complexity increases
Solution Approach 1:
The patent replaces complex mechanical or analog phase adjustment mechanisms with a digitally controlled delay line. This substitution uses digital control signals to adjust the delay, simplifying the overall system architecture while achieving the same phase adjustment function and reducing spur generation
3Adaptability or versatility
If fractional-N mode is used to enable frequency tuning, then frequency flexibility is improved, but periodic error from DTC delay changes introduces fractional spur
Solution Approach 1:
The patent converts the harmful periodic error from DTC delay changes into a beneficial effect by using the same delay line to adjust the injection phase. The delay line compensates for the timing errors introduced by fractional-N operation, transforming the source of spurs into a mechanism for eliminating them while preserving frequency tuning flexibility
Data Source
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AI summary
A circuit (100) for facilitating random edge injection locking of an oscillator (140) is provided. The circuit comprises a clock signal (101) and a digitally controlled delay line (110), where said digitally controlled delay (110) line is configured to delay the clock signal (101), thereby generating a delayed clock signal (102) . The circuit further comprises an edge selector (120) configured to generate a phase select signal (103) with a random pulse sequence. Moreover, the circuit comprises a pulse generator (130) downstream to the digitally controlled delay line (110) configured to generate injection pulses (104,105) from the delayed clock signal (102) for at least two phases of the oscillator (140) based on the phase select signal (103).