Fig. 5: Experimental demonstration of the metasurface towards realistic communication scenarios.
(a) Diagram block of communication scenario using the proposed metasurface and the BPSK modulation scheme. The time length for each bit Tb is set to Tb = 10 ns, while the time slot for each frequency carrier is 300 ns (corresponding to 30 bits). (b) Examples of the received BPSK signals comparing two frequency sequences (left) before and (right) after implementing additive white Gaussian noise. (c) BER vs. S/N analysis using two different frequency sequences. (d, e) Spectrogram of (d) input and (e) output chirp signals sweeping the oscillation frequency during each 300-ns time slot. The centre frequency in each time slot hops between f1, f2 and f3, which correspond to sequence #1 in Fig. 4d. In this example, the chirp signal is swept by 0.4 GHz in each time slot. (f) Transmittance reduction with different sweep frequency ranges. The transmitted energies of chirp signals using different frequency sequences are compared to the transmitted energy of sequence #1 shown in Fig. 4d. (g, h) Spectrogram of (g) input and (h) output frequency-sequence signals corresponding to sequence #1 in Fig. 4d with double-band interference signals at f4 = 2.9 GHz and f5 = 3.6 GHz. (i) Transmittance reduction with different interference-to-signal ratios (I/Ss). The transmitted energies of frequency-sequence signals and interference signals are compared to the transmitted energy of sequence #1 shown in Fig. 4d. Here, the interference signal magnitude (f4 and f5) is swept following the interference-to-signal ratio (I/S) from −14 dB to 0 dB. In these measurements, the input power is set to 20 dBm.
