PLL Bias Current Switching for Stable High-Frequency Locking
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In high-frequency signal processing devices, especially in mobile communications, the PLL circuit faces challenges with injection locking, which increases power consumption and requires optimal current adjustment based on transmission power, leading to abrupt frequency changes and long calibration times, especially with temperature variations.
Innovation Solution
A high-frequency signal processing device with an oscillation circuit, feedback loop circuit, and control circuit that measures frequency differences and approximates relationships to control bias current, using a method that involves switching the coarse adjustment capacitance and power supply voltage to maintain stable oscillation frequencies, thereby reducing calibration time and power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the current of the oscillation circuit is increased to prevent injection locking, then injection locking is prevented, but power consumption of the RFIC is increased
Solution Approach 1:
The oscillation circuit current is dynamically adjusted based on transmission power levels. During transmission, the current is increased to prevent injection locking; during reception, the current is reduced to minimize power consumption. This dynamic adaptation resolves the contradiction between maintaining reliability during transmission and reducing energy consumption during other operations.
Solution Approach 2:
The patent changes the operating parameters (current level) of the oscillation circuit based on operational mode. By switching between different current levels corresponding to different transmission power settings, the system prevents injection locking when needed while minimizing power consumption when transmission is not active.
2Use of energy by moving object
If the current of the oscillation circuit is switched during locking to reduce power consumption, then power consumption is reduced, but oscillation frequencies are abruptly changed causing unlocking
Solution Approach 1:
The system performs preliminary calibration to determine the relationship between oscillation circuit current and free-run frequency before normal operation. This pre-acquired information is stored and used during operation to predict and compensate for frequency changes when current switching is necessary, preventing unlocking while enabling power savings.
Solution Approach 2:
The patent implements a feedback mechanism where the measured frequency deviation caused by current switching is used to adjust the control voltage or digital code of the oscillation circuit. This feedback loop compensates for the abrupt frequency changes, maintaining locking stability even when current is switched to reduce power consumption.
3Reliability
If capacitors of the oscillation circuit are switched simultaneously with current switching to maintain frequency, then frequency stability is maintained, but calibration time is excessively long
Solution Approach 1:
Instead of performing complete calibration for every current switching operation, the patent applies partial correction based on pre-acquired calibration data. The system uses the stored relationship between current and frequency to make immediate adjustments, performing only minimal calibration when necessary rather than full calibration each time, thus maintaining frequency stability while significantly reducing calibration time.
Solution Approach 2:
The system performs comprehensive calibration once during initialization or manufacturing to establish the current-frequency relationship. This preliminary action creates a lookup table or mathematical model that enables rapid frequency compensation during subsequent current switching operations without requiring repeated full calibration, thereby resolving the time-stability contradiction.
4Use of energy by moving object
If the oscillation circuit current is adjusted according to transmission power, then power consumption is optimized, but frequency calibration becomes complex due to temperature dependence
Solution Approach 1:
The patent creates a universal calibration model that accounts for both current and temperature variations. By establishing a comprehensive relationship during initial calibration that incorporates temperature effects, the system can handle multiple operating conditions (different currents, different temperatures) using a single calibration framework, reducing the need for separate calibration procedures for each condition.
Solution Approach 2:
The system introduces temperature as an intermediate parameter in the calibration process. By measuring temperature and using it to select or adjust the appropriate calibration data from pre-acquired tables, the system simplifies the complexity of temperature-dependent calibration while maintaining accuracy across different thermal conditions.
Data Source
AI summary
A high-frequency signal processing device having a frequency synthesizer (PLL: Phase Locked Loop) is provided. A control circuit measures oscillation frequencies obtained upon setting a bias current of an oscillation circuit to first and second bias setting values and acquires a frequency difference amount of the oscillation frequencies. The frequency difference amount may be acquired as difference amount of setting values of a coarse adjustment capacitance setting signal (CTRM) using, for example, an automatic frequency selector unit. The control circuit retains a relationship of a difference amount of bias setting values and a difference value of setting values of the CTRM and approximating the relationship to a linear function. Thereafter, the control circuit defines, upon switching the bias current during locking of the PLL, the CTRM based on the linear function and switches the CTRM together with the bias current.