PLL Ramp Linearity Measurement Using MMD Downmixing
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Solution Overview
Problem
Radar systems using phase-locked loops (PLL) face challenges in measuring and correcting ramp nonlinearity, which affects the accuracy of frequency modulation ramps over the entire product life.
Innovation Solution
The implementation of a method and system that includes a PLL with a multi-modulus divider (MMD) for generating frequency modulation ramps, downmixing the MMD output to measure ramp linearity, and calculating the frequency based on these measurements, allowing for internal correction of nonlinearity and determination of the PLL lock condition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If ramp linearity is measured only in the lab during design and verification phases, then manufacturing precision is improved, but reliability deteriorates because nonlinearity cannot be detected or corrected during actual radar operation
Solution Approach 1:
The patent implements a feedback mechanism where the MMD output is continuously measured during radar operation. The measured frequency values are fed back to calculate actual ramp linearity parameters, enabling real-time detection and correction of nonlinearity drift, thus maintaining reliability throughout the product life
Solution Approach 2:
The radar system performs self-diagnosis by using its own MMD output to measure and evaluate ramp linearity. The system automatically calculates frequency values and detects nonlinearity without external intervention, enabling continuous self-monitoring and correction during operation
2Reliability
If an internal measurement mechanism is added to measure ramp linearity during operation, then reliability is improved, but device complexity increases
Solution Approach 1:
The MMD output is utilized for dual purposes: it serves both as a control signal for the PLL and as a measurement signal for ramp linearity evaluation. This multi-functionality approach allows the system to gain measurement capability without adding separate dedicated measurement hardware, thus limiting complexity increase
Solution Approach 2:
The patent uses the MMD output frequency as an intermediary signal that carries information about both PLL locking status and ramp linearity. By measuring this single intermediary signal, the system extracts multiple pieces of information without requiring separate measurement paths for each parameter
3Measurement precision
If the MMD output is measured directly at its original frequency, then measurement precision is improved, but ease of operation deteriorates because high frequency measurement is more difficult and error-prone
Solution Approach 1:
The patent transforms the measurement parameter by converting the high-frequency MMD output into a lower intermediate frequency through mixing with a reference signal. This parameter change makes the signal easier to handle and measure with standard electronics while preserving the linearity information through the frequency relationship
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 enables precise measurement and correction of ramp nonlinearity within the radar system, ensuring timely re-locking of the PLL and improving the accuracy of frequency modulation ramps, thereby enhancing the reliability and efficiency of radar operations.
Implementation Method 1
Radar applications use a phase-locked loop (PLL) to generate high frequency ramps over a specified frequency range
Implementation Method 2
downmixing an output of the MMD to a frequency above zero Hertz
Data Source
AI summary
A phase-locked loop (PLL) for a radar system includes an oscillator configured to have an output frequency and a multi-modulus divider (MMD) configured to implement successive frequency modulation ramps of the oscillator output frequency, each frequency modulation ramp beginning at a first frequency and ending at a second frequency. The PLL is operated by downmixing an output of the MMD to a frequency above zero Hertz, measuring the downmixed output of the MMD to generate a plurality of MMD output measurements for each frequency modulation ramp, and calculating the frequency of the MMD based on the plurality of MMD output measurements for each frequency modulation ramp.