High-Precision and Stable Demodulation Method for Large-Range and High-Sensitivity Surface Acoustic Wave Sensors

The echo signals of surface acoustic wave (SAW) sensors are characterized by weak energy and fast attenuation. Traditional demodulation algorithms struggle to achieve fast and accurate demodulation. The Prony algorithm, whose frequency resolution is not limited by the signal sequence length, can realize high-frequencyresolution demodulation, but its noise resistance deteriorates with variation in the ratio of sampling frequency to signal frequency. High-sensitivity and large-range SAW sensors often have a large bandwidth, making it difficult for the Prony algorithm to stably demodulate such sensors. To address this, a Prony algorithm based on polyphase decomposition is proposed. This algorithm can adaptively adjust the relationship between the sampling frequency of the demodulation system and the signal frequency. It also avoids ill-conditioning of the autocorrelation matrix, thereby solving the problem of deteriorated noise resistance of the Prony algorithm caused by signal frequency variation. Meanwhile, it reduces the computational complexity of the Prony algorithm. Simulation and experimental results show that compared with traditional demodulation algorithms, this algorithm achieves high-resolution and high-precision demodulation of echo signals. It also exhibits excellent noise resistance and demodulation speed, and is suitable for demodulating echo signals of large-range and high-sensitivity SAW sensors. In the SAW sensor demodulation system applying the proposed algorithm, when demodulating the echo signal frequency of the SAW temperature sensor, the standard deviation is less than 0.3389 kHz, the temperature resolution is less than 0.0259 °C, and the maximum demodulation time is 6.28 ms.