DC-Coupled PLL FM Discriminator With DC Drift Compensation
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Solution Overview
Problem
Phase-locked loop (PLL) circuits face instability due to manufacturing parameter variations and DC voltage drifting over time and temperature, making it challenging to design a single loop filter for all manufacturing processes and affecting the circuit's usefulness.
Innovation Solution
A DC voltage drift detection and reduction circuit is integrated into the PLL, which compares the frequency of the oscillating signal to detect and compensate for DC drift by adjusting the voltage-controlled oscillator, thereby reducing output drift.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single loop filter design is used across all manufacturing processes, then manufacturing complexity is reduced, but manufacturing precision deteriorates due to process variations
Solution Approach 1:
The patent applies parameter changes by making the loop filter characteristics adjustable through digital control. The loop filter includes programmable gain amplifiers and adjustable RC time constants that can be modified via digital signals from a microprocessor, allowing the same physical circuit to be optimized for different manufacturing processes and conditions.
Solution Approach 2:
The patent implements dynamics by transitioning from a static loop filter design to a dynamic one where filter parameters can change over time. The system can adjust loop filter characteristics during operation based on detected drift conditions, temperature changes, or manufacturing variations, enabling adaptive optimization without requiring multiple fixed designs.
2Device complexity
If DC drift compensation is not implemented, then device complexity is reduced, but reliability deteriorates due to DC voltage drifting over time and temperature
Solution Approach 1:
The patent implements feedback by continuously monitoring the DC voltage level at the integrator output and using this information to adjust the loop filter characteristics. A microprocessor detects the DC drift and sends control signals to modify the loop filter gain and time constants, creating a closed-loop system that actively compensates for drift and maintains reliability.
Data Source
AI summary
An electronic assembly having a phase locked discriminator circuit that includes a phase locked loop (PLL), a voltage controlled oscillator (VCO), a signal output integrator, and a direct current (DC) drift reducing circuit. The PLL has an input to receive an oscillating signal. The signal output integrator, the PLL and the VCO are all electrically coupled together. The DC drift reducing circuit is electrically coupled to the PLL, the signal output integrator and the VCO. The DC drift reducing circuit detects a DC drift of an output of the signal output integrator by comparing a frequency of the oscillating signal to the DC drift.