Acoustic Clock Synchronization for Wireless Sensor Arrays
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Solution Overview
Problem
Existing multi-channel sound recording systems face challenges in maintaining synchronous clock rates between microphones and a transmitter without the use of wires, which is impractical and expensive, especially in scenarios like virtual reality and ultrasonic applications where wireless and clock-synchronized sampling is necessary.
Innovation Solution
The solution involves calibrating analog-to-digital converters at each microphone to match the transmitter's clock rate using a digital-to-analog converter and a transducer, employing a clock rate estimation process with Hilbert filters, matched filter banks, event detectors, state sequence detectors, and loop filters to adjust the clock phase, allowing for wireless operation without clock rate discrepancies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If all microphones are connected through wires to the transmitter for synchronous sampling, then clock rate synchronization is achieved, but system cost and complexity increase
Solution Approach 1:
The patent extracts the clock synchronization function from the physical wire connection by using acoustic signal transmission. The transmitter embeds a known clock signal in the acoustic waveform, and the receiver extracts this clock signal to synchronize its sampling, eliminating the need for separate wire connections for clock synchronization.
Solution Approach 2:
The acoustic signal itself serves as an intermediary carrier that transmits both the audio data and the clock synchronization information. Instead of using wires as the intermediary for clock transmission, the patent uses the acoustic waveform as the medium to convey timing information to the receiver.
2Reliability
If professional audio equipment with wire connections is used for multi-channel recording, then synchronous sampling is ensured, but system cost increases
Solution Approach 1:
The patent replaces expensive professional audio equipment with simpler, more affordable components. The system uses standard microphones, speakers, and digital signal processing rather than specialized audio interface hardware, making the solution accessible for consumer applications while maintaining synchronization accuracy.
Solution Approach 2:
The patent substitutes the mechanical wire connection system with an acoustic field-based system. Instead of physically connecting microphones to the audio interface through cables, the system uses acoustic wave propagation and digital signal processing to achieve the same synchronization function at lower cost.
3Reliability
If wires are used to connect microphones in virtual reality applications, then clock synchronization is maintained, but ease of operation and user mobility are reduced
Solution Approach 1:
The patent removes the physical wire constraint from the system by extracting the clock signal transmission function and embedding it within the acoustic signal itself. This allows the receiver to synchronize without any physical connection to the transmitter, enabling free movement in virtual reality applications.
Solution Approach 2:
The system transitions from a static, wired configuration to a dynamic, wireless configuration. The receiver can move freely in space while maintaining clock synchronization through continuous acoustic signal reception and processing, adapting to the dynamic nature of virtual reality user movement.
Data Source
AI summary
A predefined signal has been used to facilitate the detection of the clock rate difference between the transmitter and the receiver. First the predefined signal is to be detected by each of the sensors and its time frame boundary information is acquired by a detector. The detector is composed of a matched filter bank, an event detector and a state sequence detector. The phase error is derived with reference to a fixed reference stored. With each of the sensors updating its local clock to the same fixed reference they can be brought to an arbitrary close clock error with one another. Thus, by applying the method disclosed here the transmitter and all the receivers can have an arbitrary small clock rate error with respect to one another. The method described is really fast in the sense that the delay needed for the detection and adjustment is minimal.