PLL Bandwidth Adaptation via Charge Pump Amplitude Control
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Solution Overview
Problem
Modern radar systems face challenges in maintaining phase noise within specified limits due to variations in production tolerances, affecting the bandwidth of phase-locked loops in RF transceivers, which impact the reliability and accuracy of radar measurements.
Innovation Solution
An RF circuit and method that utilize a charge pump to generate current pulses with adjustable amplitude and duration, coupled with a capacitive element to produce a tuning voltage for an RF oscillator, allowing for precise control of the frequency through a phase-locked loop, enabling the calculation of current amplitude based on measurement signals and current differences, thereby adjusting the phase-locked loop bandwidth.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the PLL bandwidth is designed according to specified phase noise limits, then phase noise is kept within limits, but production tolerances cause bandwidth variations affecting measurement reliability
Solution Approach 1:
The patent changes the operating parameters of the charge pump dynamically by adjusting the pulse width of control signals. This allows the charge pump current amplitude to be adapted, thereby compensating for manufacturing tolerances in the PLL bandwidth without changing the physical structure or component values.
Solution Approach 2:
The patent implements a feedback mechanism where the actual PLL bandwidth or phase noise characteristics are measured, and this information is used to adjust the charge pump control parameters. This closed-loop control ensures that phase noise remains within specifications despite manufacturing variations.
2Device complexity
If the charge pump current amplitude is fixed, then the circuit is simple, but production tolerances cause bandwidth variations
Solution Approach 1:
The patent transforms the static charge pump current amplitude into a dynamic parameter that can be adjusted through pulse width modulation of control signals. This dynamic adjustment capability allows the system to compensate for manufacturing tolerances while maintaining relatively simple circuit architecture.
3Reliability
If the PLL bandwidth is optimized for minimum phase noise, then phase noise performance is improved, but the system cannot adapt to temperature variations and production tolerances
Solution Approach 1:
The patent enables dynamic parameter changes in the charge pump operation by adjusting pulse width, allowing the PLL bandwidth to be optimized for different operating conditions including temperature variations and production tolerances, thus achieving both good phase noise performance and environmental adaptability.
Solution Approach 2:
The patent performs preliminary characterization of the PLL bandwidth during manufacturing or initialization, and uses this information to pre-adjust the charge pump parameters before actual operation. This preliminary action ensures optimal phase noise performance is achieved despite production 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
This solution effectively stabilizes the phase noise of the RF oscillator, enhancing the reliability and accuracy of radar measurements by compensating for production tolerances and temperature variations, ensuring consistent performance across radar systems.
Implementation Method 1
a capacitive element coupled to the charge pump and configured to receive the current pulses and to generate a tuning voltage depending thereon
Data Source
AI summary
An RF circuit comprises a charge pump configured to generate current pulses having a first current amplitude and a predetermined duration; and a capacitive element configured to receive the current pulses and to generate a tuning voltage depending thereon. An RF oscillator is configured to generate an RF signal having a frequency that is dependent on the tuning voltage. The RF circuit comprises a measuring circuit configured to generate a measurement signal representing the tuning voltage or the frequency of the RF signal. A controller circuit is configured to drive the charge pump in order to change the first amplitude of a current pulse by a current difference, and ascertain a first change in the measurement signal and a second change in the measurement signal. A measurement value for the first amplitude can be calculated based on the first change and the second change based on the current difference.