Fractional-N PLL Bandwidth Control Using Adaptive Charge Pump Current
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Phase-locked loops (PLLs) used in frequency modulated continuous wave (FMCW) radar systems face challenges in maintaining consistent loop bandwidth across varying control voltage ranges, leading to potential phase noise variations and increased power consumption.
Innovation Solution
The system incorporates current adjusting circuitry that varies the charge pump current in response to different control voltage ranges, ensuring a consistent bandwidth by compensating for variations in VCO gain (KVCO). This is achieved using current-steering digital-to-analog converters (DACs) that adjust the bias current provided to the charge pump.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the charge pump current is increased to maintain consistent loop bandwidth across varying control voltage ranges, then phase noise variations are reduced, but power consumption increases
Solution Approach 1:
The charge pump current is made dynamically adjustable based on the control voltage range. The system transitions from a static current configuration to a dynamic one where the current magnitude changes according to the operating conditions, specifically adjusting current magnitude based on whether the control voltage is in a first range or a second range
Solution Approach 2:
The patent changes the parameter of charge pump current magnitude from a fixed value to a variable value that depends on the control voltage range. By monitoring the control voltage and adjusting the current magnitude accordingly (higher current in first range, lower current in second range), the system maintains consistent loop bandwidth while optimizing power consumption
2Reliability
If multiple VCOs are used to cover the full bandwidth of the chirp signal, then phase noise variations are reduced, but device complexity increases
Solution Approach 1:
A single VCO is made to perform multiple functions by covering the full bandwidth of the chirp signal through dynamic charge pump current adjustment. The VCO operates across different control voltage ranges with corresponding current magnitude adjustments, allowing one component to replace what would traditionally require multiple specialized VCOs
Data Source
AI summary
Systems and methods for controlling a charge pump current in response to a control voltage provided to a voltage-controlled oscillator (VCO) are disclosed. An example system includes a phase-locked loop including a charge pump and a VCO coupled to the charge pump. Current adjusting circuitry receives the control voltage and controls the charge pump current. The current adjusting circuitry is configurable to cause the charge pump current to increase by a first amount responsive to the control voltage being in a first range, and cause the charge pump current to decrease by a second amount responsive to the control voltage being in a second range. A chirp signal output by the phase-locked loop has a bandwidth defined by a first bandwidth segment that corresponds to the control voltage being in the first range and a second bandwidth segment that corresponds to the control voltage being in the second range.