Filter Circuit Cutoff Frequency Adjustment Using Digital Pulse Counting
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Solution Overview
Problem
Conventional methods for adjusting and measuring the cutoff frequency of filter circuits, such as low pass and high pass filters, require repeated steps involving sine wave input and output monitoring, which is labor-intensive and costly, especially due to the need for high-cost analog signal generation circuits.
Innovation Solution
A filter circuit with a pulse generation circuit that supplies variable frequency pulses and an impedance element selection unit to detect the cutoff frequency by checking the attenuation of output pulses, allowing for easy adjustment and measurement of the cutoff frequency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a conventional sine wave input method is used to adjust and measure cutoff frequency, then measurement accuracy can be achieved, but the process requires repeated steps with high-cost analog signal generation circuits, increasing device complexity and cost
Solution Approach 1:
The patent replaces the analog signal generation system with a digital pulse generation system. Instead of using analog sine wave generators, the invention uses a digital pulse signal generator to produce square wave pulses with varying frequencies. The cutoff frequency is determined by counting the number of input pulses and output pulses, and comparing their difference. This digital approach simplifies the device while maintaining measurement capability.
Solution Approach 2:
The patent uses digital counting and comparison to replicate the functional effect of analog sine wave measurement. By counting pulses at different frequencies and comparing the differences, the system captures the essential measurement information without requiring complex analog signal generation circuits.
2Manufacturing precision
If repeated sine wave input and output monitoring steps are performed, then accurate cutoff frequency adjustment is possible, but the tuning process becomes labor-intensive and time-consuming
Solution Approach 1:
The patent performs preliminary counting of input and output pulses across a frequency range before determining the cutoff frequency. By pre-counting all pulses and calculating their differences in advance, the system identifies the cutoff frequency point without requiring iterative adjustment and monitoring steps, significantly reducing tuning time while maintaining precision.
Solution Approach 2:
The system automatically determines the cutoff frequency by comparing pulse counts and identifying where the difference exceeds a predetermined threshold. This self-determining mechanism eliminates the need for manual repeated monitoring and adjustment, making the process both precise and efficient.
3Reliability
If high-cost analog signal generation circuits are used, then sine wave input for filter testing can be provided, but the overall system cost increases
Solution Approach 1:
The patent substitutes digital pulse generation circuitry for analog sine wave generation circuits. The digital pulse generator produces square wave signals that are fed through the filter under test, and the resulting output pulses are counted and compared. This digital approach achieves reliable signal generation for filter testing without requiring expensive analog components.
Solution Approach 2:
The patent employs simple digital pulse generation and counting mechanisms that are far less expensive than analog signal generation circuits. The system uses basic digital components to generate pulses, count them, and determine cutoff frequency, replacing costly analog equipment with affordable digital alternatives.
Data Source
AI summary
A filter circuit, having a plurality of selectable impedance elements, that has a cutoff frequency dependent on a selected impedance element, comprises a pulse generation circuit that supplies a variable frequency pulse with a successively increasing or decreasing frequency to an input of the filter circuit; and an impedance element selection unit that checks the attenuation of the output pulse of the filter circuit corresponding with the input of the variable frequency pulse and selects the plurality of impedance elements on the basis of the position of a pulse that is attenuated to or below a reference value.