Band-Pass Filter Frequency Tracking Without PLL Circuits
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Solution Overview
Problem
Conventional signal detection methods, such as the PLL method, require a signal generator and are ineffective in accurately detecting signals with unknown or changing frequencies due to noise components and complex circuit configurations.
Innovation Solution
A signal detection apparatus utilizing a band-pass filter with a second-order IIR digital filter and a coefficient controller to adjust the filter's coefficients based on phase difference calculations, allowing for accurate detection of signals without a signal generator.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the PLL method is used to detect system signals, then phase detection can be performed, but the circuit configuration becomes complicated due to requiring signal generators and feedback control circuits
Solution Approach 1:
The invention extracts and eliminates the signal generator and feedback control circuits from the PLL method, retaining only the essential phase detection function through a simplified architecture that uses a band-pass filter with variable coefficients and a phase difference detector to achieve phase-locked detection without requiring the complex generator and feedback components
Solution Approach 2:
The band-pass filter automatically adjusts its own characteristics by varying its coefficients based on the detected phase difference, enabling the system to self-tune and lock onto the input signal frequency and phase without external control signals or feedback mechanisms, thus simplifying the overall circuit configuration
2Reliability
If the PLL method is used for phase detection, then phase synchronization can be achieved, but the system cannot accurately detect signals with unknown or changing frequencies due to noise components
Solution Approach 1:
The invention employs a dynamic band-pass filter whose coefficients are continuously adjusted based on real-time phase difference detection. This dynamic adaptation allows the filter to track and synchronize with signals having unknown or time-varying frequencies, improving both reliability and precision by eliminating the fixed-frequency limitation of conventional PLL systems
Solution Approach 2:
The system changes the parameters (coefficients) of the band-pass filter dynamically according to the detected phase difference and signal characteristics. By adjusting these parameters in real-time, the system can accurately track frequency variations and noise conditions, enabling reliable detection of signals with unknown or changing frequencies
Data Source
AI summary
A signal detection apparatus detects the frequency of an input signal without using a PLL. The detection apparatus includes a first and a second orthogonalizer, a phase difference calculator and an integrator, to control the variable coefficient a1 of a band-pass filter. Information e[k]=M·sin(phi) representing the phase difference phi between the input data x[k] and the output data y[k] is calculated with the first and second orthogonalizers and the phase difference calculator. The sign of e[k] is inverted and a predetermined integral calculation is performed with the integrator, and the calculated integral value is set as the coefficient a1 of the band-pass filter. Every time input data x[k] is input, the coefficient a1 is changed by reducing it when e[k]>0 and increasing it when e[k]<0. Thus, the frequency of the output signal of the band-pass filter is matched to the input signal.