In this paper, we present and demonstrate a low complexity elastic wave signaling and reception method to achieve high data rate communication on dispersive solid elastic media, such as metal pipes, using piezoelectric transducers of PZT (lead zirconate titanate). Data communication is realized using pulse position modulation (PPM) as the signaling method and the elastic medium as the communication channel. The communication system first transmits a small number of training pulses to probe the dispersive medium. The time-reversed probe signals are then utilized as the information carrying waveforms. Rapid timing acquisition of transmitted waveforms for demodulation over elastic medium is made possible by exploring the reciprocity property of guided elastic waves. The experimental tests were conducted using a National Instrument PXI system for waveform excitation and data acquisition. Data telemetry bit rates of 10 kbps, 20 kbps, 50 kbps and 100 kbps with the average bit error rates of 0, 5.75 x 10-4, 1.09 x 10-2 and 5.01 x 10-2, respectively, out of a total of 40, 000 transmitted bits were obtained when transmitting at the center frequency of 250 kHz and a 500 kHz bandwidth on steel pipe specimens. To emphasize the influence of time reversal, no complex processing techniques, such as adaptive channel equalization or error correction coding, were employed.
A wideband, low‐profile, and high‐gain antenna loaded with a dual‐layer metasurface is proposed in this study. The metasurface consists of two metallic layers printed on two dielectric layers, in which each metallic layer contains an array of 4×4 square patch cells. The proposed antenna is fed by an aperture coupled layer under the metasurface. This design makes the antenna work at two different modes with different resonant frequencies close to each other, to enhance the bandwidth. To achieve the best bandwidth performance, a genetic algorithm is adopted to optimise the geometrical parameters of this antenna. This metasurface‐based antenna maintains a low profile of 0.09λ0 at 5 GHz, meanwhile yields wideband characteristics for both the impedance and gain bandwidth. The −10 dB impedance bandwidth of the proposed antenna is about 44% (4.08–6.38 GHz) and the 3 dB gain bandwidth reaches 45% (4.16–6.56 GHz) with a peak realised gain of 11.6 dBi. A prototype of the antenna is fabricated and the measured results demonstrate the authors’ design.
A novel planar bow-tie aperture antenna is proposed for ultra-wide band (UWB) application in this paper. Beveling technique is employed to increase the impedance bandwidth, and slot loading is introduced to improve the impedance matching. The measured impedance bandwidth is from 2.7 to 12 GHz for S 11 < −10 dB, proving the effectiveness of these two techniques. The measured radiation patterns are relatively stable almost over the entire ultra-wide band of 3.1 to 10.6 GHz with low cross-polarization levels of at least −10 dB. Moreover, the proposed antenna maintains the advantages of ease of fabrication and relatively small electrical size.
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