Telephone System Doubles Reception Count via Alternating DSP Processing
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Solution Overview
Problem
Existing telephone communications systems face challenges in increasing the reception count of multifrequency signals using digital signal processors (DSPs) due to cost constraints and limitations in improving receiver processing specifications.
Innovation Solution
A telephone communications system that quantizes multifrequency signals at a sampling frequency twice or more than necessary, employs a low-pass filter with a cutoff frequency higher than the maximum frequency of the signals, and alternately performs odd-numbered and even-numbered receiver processing on the filtered data to double the reception count.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the DSP specification is improved to increase reception count, then the reception count increases, but the cost increases
Solution Approach 1:
The patent segments the received signal into multiple independent processing channels. By dividing the signal processing into separate odd-numbered and even-numbered processing paths, the system can handle multiple frequency signals simultaneously using the same DSP hardware, effectively doubling the reception count without requiring more powerful or expensive processors.
Solution Approach 2:
The patent implements periodic action by alternately performing odd-numbered receiver processing and even-numbered receiver processing on the same DSP. This time-division multiplexing approach allows the processor to handle multiple reception tasks in sequence, achieving increased reception capacity without hardware upgrades.
2Measurement precision
If the sampling frequency is increased to improve signal processing capability, then the processing accuracy improves, but the data processing load increases
Solution Approach 1:
The patent extracts and removes frequency components outside the target range using a low-pass filter. By eliminating high-frequency components that are not needed for DTMF/MF signal detection, the system reduces the data processing load while maintaining adequate sampling frequency for accurate signal processing.
Solution Approach 2:
The patent changes the sampling frequency parameter to exactly twice the maximum signal frequency (Nyquist rate) rather than using higher frequencies. This optimal parameter selection provides sufficient processing accuracy for multifrequency signal detection while minimizing the data processing load on the DSP.
3Loss of information
If the cutoff frequency of the low-pass filter is increased to pass more frequency components, then more signal information is preserved, but noise and interference increase
Solution Approach 1:
The patent applies local quality by setting the low-pass filter cutoff frequency specifically at 2 kHz, which is optimized for the DTMF and MF signal frequency ranges. This localized frequency selection preserves all necessary signal information for multifrequency detection while effectively blocking higher frequency noise and interference.
Data Source
AI summary
A telephone communications system includes a quantizing device quantizing a multifrequency signal at a sampling frequency which is twice or more as larger as a sampling frequency necessary for sampling the multifrequency signal to produce quantized data, a low-pass filter low-pass filtering the quantized data at a cutoff frequency higher than a maximum frequency of the multifrequency signal to produce low-pass filtered data, and a multifrequency signal receiver alternately performing an odd-numbered receiver processing and an even-numbered receiver processing on the low-pass filtered data.