DCO Gain Compensation for Stable ADPLL Frequency Hopping
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Solution Overview
Problem
Digitally-controlled oscillators (DCOs) exhibit nonlinear behavior across their tuning band, leading to stability issues and uncertainty in phase locked loops (PLLs), particularly in all-digital PLLs (ADPLLs), which complicates frequency locking and signal generation.
Innovation Solution
The implementation of a compensation technique using a normalizing gain multiplier, calculated based on the DCO's nonlinear gain behavior, allows for predictive locking and stable frequency generation by decoupling phase and frequency information from process, voltage, and temperature variations, employing linear interpolation to reduce design complexity and power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by stationary object
If a DCO is used in an ADPLL to reduce area and power dissipation, then area and power consumption are reduced, but nonlinear gain behavior causes stability issues and frequency locking uncertainty
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting the gain multiplier based on the desired output frequency. The gain multiplier is calculated as a function of frequency to compensate for the DCO's nonlinear gain behavior, transforming the system's operational parameters to maintain stability across the tuning band.
Solution Approach 2:
The patent replaces traditional analog compensation mechanisms with a digital solution. Instead of using analog circuits to linearize the DCO response, the invention uses digital calculation of gain multipliers based on frequency-dependent compensation formulas, substituting mechanical/analog approaches with digital signal processing.
2Device complexity
If traditional frequency locking methods are used without compensation, then the system is simpler to implement, but phase error increases and locking speed decreases
Solution Approach 1:
The patent applies preliminary action by pre-calculating and storing gain multiplier values in a lookup table before operation. The compensation values are determined in advance based on the desired frequency range, allowing the system to quickly retrieve and apply the appropriate gain multiplier during frequency locking without real-time computation delays.
Solution Approach 2:
The patent uses copying by creating a lookup table that stores pre-computed gain multiplier values. Instead of calculating compensation values during operation, the system copies the appropriate pre-calculated value from the lookup table based on the desired frequency, reducing computational overhead and speeding up the locking process.
3Measurement precision
If runtime frequency measurement is performed to achieve accurate locking, then frequency accuracy improves, but power consumption and measurement time increase
Solution Approach 1:
The patent introduces an intermediary element - the gain multiplier - that mediates between the desired frequency and the actual DCO output. Instead of measuring the frequency to determine compensation, the system uses the gain multiplier as an intermediary parameter that directly adjusts the DCO's behavior based on the desired frequency, eliminating the need for frequency measurement.
Solution Approach 2:
The patent applies self-service by having the system use its own knowledge of the DCO's nonlinear characteristics to self-correct the frequency output. The gain multiplier is calculated based on pre-characterized DCO behavior, allowing the system to self-compensate without external measurement or intervention.
Data Source
AI summary
Systems and methods are provided for hopping a digitally controlled oscillator (DCO) among a plurality of channels, wherein a gain of the DCO KDCO is a nonlinear function of frequency. A first normalized tuning word (NTW) corresponding to a first channel of the plurality of channels is generated. A first normalizing gain multiplier X is generated based on the nonlinear function of frequency, on an estimate of the nonlinear function of frequency, at a first frequency corresponding to the first channel. The first NTW is multiplied by the first X to obtain a first oscillator tuning word (OTW). The first OTW is input to the DCO to cause the DCO to hop to the first channel. A system for hopping among a plurality of channels at a plurality of respective frequencies comprises a phase-locked loop (PLL), a digitally controlled oscillator (DCO), a multiplexer, and an arithmetic module.