VCO RC Filter Calibration for Wider Tuning and Lower Phase Noise
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Solution Overview
Problem
Existing oscillation signal generation circuits operating in high frequency bands exceeding 100 GHz face challenges in achieving accurate calibration due to accuracy variations between transistors, leading to phase noise issues and reduced design margins, particularly affecting voltage-controlled oscillators (VCOs).
Innovation Solution
An oscillation signal generation circuit is designed with a reference signal source, a variable resistance and capacitance filter to remove noise from the control voltage, and a calibration circuit that adjusts the current value by controlling the resistance value, expanding the calibration range while reducing phase noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an RC filter is inserted into the VCO to reduce noise in the current flowing through the VCO, then phase noise is reduced, but a leakage current flowing through the resistance causes a voltage drop that narrows the calibration range
Solution Approach 1:
The patent applies dynamics by making the resistance value variable rather than fixed. The variable resistance element allows the filter characteristics to be adjusted dynamically during calibration, enabling the system to maintain effective noise filtering while expanding the calibration range by adapting the resistance value to compensate for leakage current effects.
Solution Approach 2:
The patent changes the resistance parameter from a fixed value to a variable value that can be adjusted during calibration. This parameter change allows the system to optimize the balance between noise filtering performance and calibration range, resolving the contradiction by enabling the resistance to take different values depending on the calibration requirements.
2Reliability
If the resistance value in the RC filter is increased to improve noise filtering, then phase noise is reduced, but the voltage drop increases which limits the calibration adjustment range
Solution Approach 1:
The patent makes the resistance dynamic by using a variable resistance element that can be adjusted during calibration. This allows the system to increase resistance when noise filtering is the priority while providing the ability to decrease resistance when calibration adjustment range is needed, thus resolving the contradiction between noise reduction and ease of calibration.
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 effectively expands the calibration range for oscillation conditions and reduces phase noise, enhancing the stability and accuracy of oscillation signals in high-frequency operations.
Implementation Method 1
a first filter that includes a variable resistance and a capacitance and removes noise in the control voltage
Data Source
Figure 1A~1B
Figure 2
Figure 3
AI summary
An oscillation signal generation circuit includes an oscillator and a calibration circuit. The oscillator includes a reference signal source circuit that has a reference signal source outputting a reference signal and converts the output reference signal into a control voltage, a filter that includes a variable resistance and a capacitance and removes noise in the control voltage, a transistor that converts the control voltage which has passed through the filter into a control current and outputs the control current, a core circuit that is driven by the control current and generates an output signal, and an output terminal that outputs the generated output signal. The calibration circuit is connected to the output terminal of the oscillator, detects whether or not the generated output signal is oscillating, and adjusts the current value of the control current by controlling the resistance value of the variable resistance in accordance with the detection result.