Fig. 4: Experimental demonstration of engineering wave propagation in accordance with frequency sequence.

(a) Equivalent circuit system with variable resistors. The variable resistance values change in the time domain depending on the incoming frequency sequence. In the time domain, the incident frequency is repeatedly changed in a particular sequence, which determines how the position of the DC source is moved. (b) Specific circuit system. JFETs are included and biased by other circuits. (c) Measurement sample designed to operate at three frequencies. (d) Measured transient transmittances during the initial period and in the steady state (left) and their averages (right). f₁, f₂ and f₃ are 3.3, 3.9 and 2.5 GHz, respectively. During the initial period, the number of distinct frequency sequences is determined by N!, where N represents the number of frequency channels available. In contrast, in the steady state, the number of distinct frequency sequences is reduced to a circular permutation of N, namely, (N − 1)!. (e) Normalized spectrogram of the input and output signals (left and right, respectively) using the frequency sequence of f₁, f₂ and f₃. (f) Normalized spectrogram of the input and output signals (left and right, respectively) using the frequency sequence of f₃, f₂ and f₁. (e) and (f) correspond to sequences #1 and #6 in (d), respectively. In these measurements, the input power is set to 20 dBm.