VCO Feedback Resistance Control for Wide-Range PLL Stability
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Solution Overview
Problem
Phase locked loops (PLLs) face challenges in reducing the size and cost of integrated circuits due to the use of large capacitors for stabilizing output signals and filtering high-frequency noise, which also limits the frequency range when the gain of the voltage controlled oscillator (VCO) is reduced.
Innovation Solution
A voltage controlled oscillator (VCO) design that includes an amplifier, feedback amplifier with a load of adjustable resistance, and a low pass filter, where the second resistor's resistance is controlled by a resistance control signal from the low pass filter, allowing for a larger frequency range without the need for large capacitors, and incorporating a current mirror and current controlled oscillator to generate an oscillating output signal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If large capacitors are used for stabilizing output signal and filtering high frequency noise, then the PLL achieves better signal stability and noise filtering, but the integrated circuit area and manufacturing cost increase
Solution Approach 1:
The patent changes the resistance parameter of the load in the feedback amplifier to optimize the PLL performance. By adjusting the resistance value, the system achieves better signal stability and noise filtering without requiring large capacitors, thus reducing the integrated circuit area while maintaining reliability
Solution Approach 2:
The patent introduces a dynamically adjustable resistance in the feedback amplifier load, allowing the system to adapt its characteristics based on operating conditions. This dynamic adjustment enables the PLL to maintain stability and filtering performance across different frequencies without relying on large fixed capacitors
2Area of stationary object
If the gain of voltage controlled oscillator is reduced to decrease capacitor size, then the integrated circuit area is reduced, but the frequency range of the PLL is limited
Solution Approach 1:
The patent changes the resistance parameter of the feedback amplifier load to compensate for the reduced VCO gain. By optimizing the resistance value, the system maintains a wide frequency range even with smaller capacitors and reduced VCO gain, thus resolving the contradiction between area reduction and frequency range maintenance
Solution Approach 2:
The patent utilizes the feedback amplifier with an adjustable resistance load to compensate for limitations introduced by reduced VCO gain. The feedback mechanism, combined with optimized resistance values, extends the effective frequency range while allowing the use of smaller capacitors, thereby maintaining adaptability while reducing area
Data Source
AI summary
A voltage controlled oscillator (VCO) is disclosed. The VCO includes an amplifier that receives a control signal and a feedback signal and generates an amplified output signal based on the difference between the control signal and the feedback signal. The VCO also includes circuitry to generate an oscillating output signal based on the amplifier output signal. Additionally, the VCO includes a feedback amplifier that generates the feedback signal based on the output of the amplifier. The feedback amplifier includes a first resistor connected in parallel with a second resistor, the second resistor having an adjustable resistance.