VCO Cap-Bank Calibration for Open-Loop Frequency Offset Correction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing signal synthesis devices struggle to correct frequency offsets during open loop operation, especially in low-power modes and under environmental changes like temperature and humidity, which affects the accuracy of frequency generation in wireless communication systems.
Innovation Solution
A signal synthesis apparatus and method that includes a voltage-controlled oscillator (VCO), an energy storage unit, a VCO input selector, and a digital controller, which calculates frequency offsets and adjusts the connection state of capacitors to compensate for frequency deviations using modulation control signals, enabling accurate frequency output in both closed and open loop modes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the PLL circuit operates in open loop mode for low-power operation, then energy consumption is reduced, but frequency offset occurs and frequency accuracy deteriorates
Solution Approach 1:
The patent applies preliminary action by measuring and storing the open-loop frequency offset during a calibration phase when the PLL is in closed-loop mode. This pre-measured offset value is then used to correct frequency deviations during subsequent low-power open-loop operations, eliminating the need for continuous closed-loop operation while maintaining frequency accuracy.
Solution Approach 2:
The patent changes the operating parameter of the PLL circuit by switching between closed-loop and open-loop modes based on power management requirements. During calibration, the system operates in closed-loop mode to measure offset; during normal low-power operation, it switches to open-loop mode while applying correction based on the pre-measured offset, thus optimizing both power consumption and frequency accuracy.
2Measurement precision
If the PLL circuit operates in closed loop mode to maintain frequency accuracy, then frequency offset is corrected, but energy consumption increases
Solution Approach 1:
The system performs preliminary frequency offset measurement during closed-loop operation, stores this calibration data, and then transitions to open-loop mode for power-saving operation. This preliminary calibration action enables accurate frequency generation without continuous closed-loop operation, reducing energy consumption while maintaining accuracy.
Solution Approach 2:
The patent implements periodic calibration where the PLL circuit intermittently operates in closed-loop mode to measure and update frequency offset values, then switches to open-loop mode for extended periods. This periodic closed-loop operation maintains frequency accuracy while minimizing energy consumption compared to continuous closed-loop operation.
3Adaptability or versatility
If capacitor banks are used for frequency modulation in VCO, then frequency modulation capability is improved, but manufacturing precision requirements increase due to process variations
Solution Approach 1:
The patent employs feedback by measuring the actual frequency output of the VCO during calibration mode and comparing it with the expected frequency. Based on this feedback, the system calculates the frequency offset caused by manufacturing variations in the capacitor banks and applies correction to compensate for these variations, thereby reducing the impact of manufacturing precision limitations.
Solution Approach 2:
The system changes the capacitance parameters of the VCO by switching different capacitors in the capacitor banks during calibration to determine the frequency-offset relationship. This parameter variation approach enables the system to characterize and compensate for manufacturing variations, allowing frequency modulation capability while accommodating standard manufacturing tolerances.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution ensures accurate frequency generation and rapid modulation by correcting frequency offsets during low-power operation and environmental changes, enhancing the performance of wireless communication devices like IoT devices.
Implementation Method 1
a voltage-controlled oscillator (VCO) that includes a modulation cap bank having a plurality of capacitors of the same capacitance and an inductor, and generates an output signal having a frequency corresponding to an input voltage
Data Source
Figure 1A~1B
Figure 2
Figure 3A~3B
AI summary
Disclosed is technology related to a signal synthesis apparatus that corrects an offset between a closed loop and an open loop to output a frequency-modulated signal. The signal synthesis apparatus includes a VCO configured to modulate and output a frequency signal in response to an input voltage by including a modulation cap bank having a plurality of capacitors, an energy storage unit configured to output a voltage using stored energy, a VCO input selector configured to connect the VCO to input of the energy storage unit in the case of a closed loop mode and connect the VCO to output of the energy storage unit in the case of an open loop mode, and a digital controller configured to control an operation mode of the VCO input selector and transmit a modulation control signal for adjusting a connection state of the capacitors of the modulation cap bank to the VCO.