Selectable Sample Clock Pulse Source for Long Cable Stability
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Solution Overview
Problem
Existing clock sources for digital audio applications are unstable when driving long coaxial cables and multiple digital signal processing equipment, failing to provide a reliable clock pulse at frequencies suitable for wideband audio sampling.
Innovation Solution
A self-contained clock pulse generator using a stable radio-frequency oscillator, counter, and flip-flops to produce user-selectable frequencies, with a pulse generator and buffer to ensure stability and compatibility with long transmission lines and capacitive loads.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If existing clock sources are used to drive long coaxial cables and multiple digital signal processing equipment, then the clock signal can reach multiple loads, but the waveform becomes noisy and distorted due to cable capacitance
Solution Approach 1:
The patent implements dynamic frequency selection allowing the clock source to operate at multiple frequencies (96 kHz, 48 kHz, 24 kHz) depending on the specific application requirements. This dynamic adaptability enables the system to optimize performance for different cable lengths and load configurations, resolving the contradiction between versatility and signal stability
Solution Approach 2:
The patent changes the electrical parameters of the clock signal by providing multiple frequency options and using a buffer output stage that can drive heavy capacitive loads. The ability to select different frequencies and use a buffered output allows the system to maintain signal integrity across varying cable lengths and load conditions, addressing both the need for adaptability and signal reliability
2Reliability
If a stable crystal oscillator is used for clock generation, then frequency stability is improved, but the frequency is fixed and not suitable for audio sampling applications requiring 96 kHz
Solution Approach 1:
The patent segments the frequency generation process by using a stable crystal oscillator for the base frequency and then dividing it through counter circuits to produce multiple output frequencies (96 kHz, 48 kHz, 24 kHz). This segmentation allows the system to maintain the stability benefits of the crystal oscillator while achieving the frequency flexibility required for audio sampling applications
Solution Approach 2:
The patent creates a universal clock source that can serve multiple frequency requirements through a single device. The multi-functional design includes frequency division circuits and selectable outputs that enable the same hardware to provide different frequencies suitable for various audio sampling rates, resolving the contradiction between stability and adaptability
3Productivity
If the clock frequency is set to 96 kHz for audio sampling, then Nyquist frequency range sampling is achieved, but practical crystals cannot operate at this frequency
Solution Approach 1:
The patent performs preliminary frequency division by using a crystal oscillator at a higher frequency (e.g., 384 kHz or 192 kHz) and then dividing it down to the required 96 kHz audio sampling frequency through counter circuits. This preliminary action at a manufacturable crystal frequency, followed by electronic division, resolves the contradiction between audio sampling requirements and crystal availability
Data Source
AI summary
A sample clock source includes a master oscillator providing a square wave at a predetermined frequency. A counter and at least one flip-flop are joined to receive the square wave and produce several different output square waves having reduced frequencies. A selector is provided to allow user selection of the different square waves. The selected square wave is provided to a pulse generator which produces a pulse having a known duration at the selected reduced frequency. The pulse generator output can be buffered and provided as the sample clock source. The buffer amplifier is designed to drive long cables with sufficient stability a signal fidelity.