Precision Frequency Monitor With IIR Interim PFM Updates
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Solution Overview
Problem
Existing precision frequency monitoring systems face limitations due to the complexity and cost of N-tap FIR filters, which are required for high precision but offer limited frequency estimation accuracy and require N seconds for memory flush time, leading to delayed PFM value updates and a trade-off between precision and qualification/disqualification time.
Innovation Solution
A precision frequency monitor using a combination of a first averaging module, a second averaging module that outputs updated values every N operational cycles, and an IIR filter to provide interim updates within each sequence of N operational cycles, replacing the N-tap FIR filter with a module performing block averaging and incorporating a downsampler or a single-tap accumulation block with a reset control and sampling gate, allowing for low-cost implementation and improved precision.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If an N-tap FIR filter is used to achieve high precision PFM measurement, then measurement precision is improved, but device complexity and cost increase significantly
Solution Approach 1:
The patent divides the filtering function into two separate modules: a first averaging module that performs initial averaging over N operational cycles, and a second averaging module that performs additional averaging. This segmentation replaces the complex N-tap FIR filter with two simpler averaging stages, reducing device complexity while maintaining measurement precision.
Solution Approach 2:
The patent replaces the expensive and complex N-tap FIR filter with inexpensive averaging modules that use simple adders and dividers. These averaging modules are computationally lighter and easier to implement, effectively substituting a costly component with cheaper alternatives that achieve the same functional goal.
2Measurement precision
If an N-tap FIR filter is used to ensure accurate PFM values, then measurement precision is improved, but the memory flush time increases to N seconds causing delayed updates
Solution Approach 1:
The patent introduces a selectable averaging factor that allows dynamic adjustment between different averaging depths. The system can switch between averaging over N operational cycles and averaging over a single operational cycle, enabling adaptive response time based on whether priority is given to precision or speed.
Solution Approach 2:
The patent implements two averaging modules where the first performs averaging over N cycles and the second performs additional averaging. By selectively enabling or disabling the second averaging module, the system can apply partial averaging (N cycles) for faster response or excessive averaging (N+1 cycles) for higher precision, depending on operational requirements.
3Measurement precision
If the averaging period is extended to improve precision, then measurement precision is improved, but the response time to frequency changes decreases
Solution Approach 1:
The patent implements dynamic control of the averaging factor through a selector that can switch between different averaging modes. When rapid response is needed, the system reduces the averaging factor to process data from fewer operational cycles. When high precision is prioritized, the system increases the averaging factor to incorporate data from more cycles, thus dynamically balancing speed and precision based on operational conditions.
Data Source
AI summary
A precision frequency monitor provides a precision frequency monitor value (PFM) indicative of the precision of the frequency or period of an input reference signal. A first averaging module is responsive to the input reference signal to find an average frequency or period during successive predetermined time periods defining operational cycles. A second averaging module is responsive to an output of the first averaging module to average the output of the first averaging module over N operational cycles, where N is an integer, and output an updated PFM value every N operational cycles. An infinite impulse response (IIR) filter is responsive to the output of the first averaging module to filter the output of the first averaging module to output interim updated PFM values within each sequence of N operational cycles.