SAW Tags With Enhanced Penetration Depth for Buried Assets Identification (Aug. 2020)

To identify buried assets, this article presents a novel design of surface acoustic wave (SAW) tag to enhance its underground penetration capacity. A penetration depth model for a SAW tag buried in materials is established to investigate the depth of detection and guide the design of the SAW tag. Multipulse position with all reflectors in two groups (MPP-ART) coding scheme is proposed to reduce the insertion loss of the SAW chip. A novel embedded monopole microstrip tag antenna is investigated with a stable frequency performance when embedded in diverse types of materials. Furthermore, a linear frequency modulation pulse compression transceiver based on software defined radio is implemented to enhance the penetration depth. The insertion loss of the SAW chip at 920 MHz with the MPP-ART coding scheme, is reduced to 26.58 dB. Through experiments, the penetration depth of the SAW radio frequency identification prototype has reached 0.75 m in river water, 0.8 m in tap water, 1.5 m in wet sand, and 3 m in dry sand, respectively. The experimental results demonstrate that the SAW tag can work in various materials with good penetration depth, relatively immune to electromagnetic interference with adjacent metallic objects, making it suitable for the identification of buried assets for industrial applications.