Novel Filter-Based Excitation Method for Pulse Compression in Ultrasonic Sensory Systems

Area of Science:

• Engineering
• Signal Processing
• Indoor Positioning Systems

Background:

• Global Navigation Satellite Systems (GNSSs) are effective outdoors, but indoor positioning remains a challenge.
• Existing ultrasonic indoor positioning systems have limited coverage and are susceptible to Doppler effects and bandwidth constraints.
• Accurate indoor positioning is crucial for location-based services (LBSs) and the Internet of Things (IoT).

Purpose of the Study:

• To propose a novel excitation and processing method for ultrasonic positioning systems to improve transmission capabilities and accuracy.
• To enhance the performance of ultrasonic indoor positioning, overcoming limitations of existing systems.
• To optimize ultrasonic signal transmission and reception for better real-time position estimation.

Main Methods:

• A superheterodyne approach enabling simultaneous multi-channel signal transmission and reception.
• Adaptation of signal bandwidths and central frequencies to transducer characteristics.
• Utilization of binary spread spectrum sequences within a multicarrier modulation framework.
• Processing of received ultrasonic signals using filter banks and matched filtering to determine Time Differences of Arrival (TDoA).

Main Results:

• The proposed narrowband ultrasonic scheme reliably operates at distances up to 40 m, exceeding conventional wideband limits (34 m).
• Ranging errors are below 3 cm at 40 m, significantly better than wideband schemes (over 8 cm).
• The narrowband scheme maintains stable operation at SNR as low as -32 dB, compared to -17 dB for wideband systems.

Conclusions:

• The novel narrowband ultrasonic positioning method significantly improves transmission capabilities, range, and accuracy.
• The system demonstrates superior performance in terms of ranging distance, error, and signal-to-noise ratio (SNR) compared to classical wideband approaches.
• The proposed method offers a robust and efficient solution for indoor positioning challenges, validated through digital twin modeling and experimental tests.