Sampling PLL Reference-Voltage Compensation for Supply Noise
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Solution Overview
Problem
Phase-locked loops (PLLs) face challenges in generating precise frequency signals due to fluctuations in the supply voltage, which lead to phase noise and degradation in performance, particularly in wireless devices where precise frequency control is critical.
Innovation Solution
The implementation of a sampler with a reference-voltage circuit that generates a reference voltage based on the supply voltage and subtracts it from the sampled voltage to cancel out supply voltage variations, thereby reducing phase noise and improving the accuracy of frequency generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a PLL uses a standard sampling circuit without reference voltage compensation, then the circuit complexity is low, but the phase noise performance degrades due to supply voltage fluctuations
Solution Approach 1:
The patent introduces a reference voltage circuit as an intermediary component that generates a reference voltage tracking the supply voltage. This reference voltage serves as a mediator between the supply voltage fluctuations and the sampling capacitor, allowing the system to compensate for supply variations without requiring complete redesign of the sampling circuit. The reference voltage circuit includes capacitors and switches that work together to create this compensating reference signal.
Solution Approach 2:
The patent changes the voltage parameter by generating a reference voltage that varies with the supply voltage. By dynamically adjusting the reference voltage level to track supply voltage changes, the system maintains accurate phase sampling despite supply fluctuations. This parameter change approach allows the sampling circuit to adapt to supply variations without increasing fundamental circuit complexity.
2Measurement precision
If a PLL uses a reference-voltage circuit to compensate for supply fluctuations, then the frequency generation accuracy improves, but the device complexity increases
Solution Approach 1:
The reference voltage circuit acts as an intermediary that provides compensation information to the sampling circuit. By introducing this intermediate reference voltage signal, the system achieves frequency generation accuracy comparable to ideal conditions without requiring complete redesign of the PLL architecture. The reference voltage serves as a bridge between the noisy supply and the precision sampling operation.
Solution Approach 2:
The reference voltage circuit performs preliminary action by pre-generating the reference voltage that tracks supply voltage variations before the sampling operation occurs. This advance preparation allows the sampling circuit to operate with accurate reference levels already in place, compensating for supply fluctuations proactively rather than requiring complex real-time adjustment mechanisms during sampling.
3Stability of the object's composition
If the sampler uses only discharge circuits without reference voltage compensation, then the ease of manufacture is high, but the stability of frequency generation deteriorates
Solution Approach 1:
The reference voltage circuit introduces an intermediary compensation mechanism that stabilizes the sampling operation against supply voltage variations. This reference voltage mediates between the unstable supply and the sampling capacitor, maintaining stable frequency generation. The added stability comes from this intermediate reference signal rather than from complicating the discharge circuitry itself.
Solution Approach 2:
The system stabilizes frequency generation by dynamically changing the reference voltage parameter to track supply voltage variations. This parameter adaptation allows the sampler to maintain stable operation despite supply fluctuations, achieving stability without requiring overly complex discharge circuit implementations.
Data Source
AI summary
In certain aspects, a sampler includes a sampling capacitor, a precharge switch coupled to the sampling capacitor, one or more discharge circuits coupled to the sampling capacitor, and a reference-voltage circuit coupled to the sampling capacitor. The reference-voltage circuit is configured to generate a reference voltage based on a supply voltage, and generate a voltage difference between a voltage on the sampling capacitor and the reference voltage.