Beilstein J. Nanotechnol.2020,11, 76–91, doi:10.3762/bjnano.11.8
estimation analysis
Amplitudeestimation performance of the three-channel multifrequency demodulators was investigated when a three-tone sinewave was applied as an input signal described by Equation 2. Here, A1 = 500 mV, A2 = 100 mV, A3 = 50 mV, f1 = 50 kHz, f2 = 150 kHz, and f3 = 300 kHz. Figure 9 shows the
amplitudeestimation error () in the time-domain and amplitude estimate power spectral density (PSD) for both low (1%fi) and high (50%fi) tracking bandwidth settings.
When the three-tone sinewave is applied, the performance of each demodulator at low bandwidths is shown to be similar. Each channel is able
(blue), f2 = 150 kHz (red) and f3 = 300 kHz (yellow).
Experimental amplitudeestimation error and power spectral density of amplitudeestimation for the (a) lock-in amplifier, (b) coherent demodulator, (c) Kalman filter, (d) Lyapunov filter and (e) direct-design method for low (1%fi) and high (50%fi
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Figure 1:
(a) Schematic diagram of sample topography amplitude-modulating a cantilever the oscillation of whi...
Beilstein J. Nanotechnol.2017,8, 1407–1426, doi:10.3762/bjnano.8.142
constant-height mode.
Keywords: amplitudeestimation; atomic force microscopy; amplitude modulation; digital signal processing; field-programmable gate array; Introduction
Amplitude modulation is one of the oldest forms of modulation in analog communication systems, mostly due to its simplicity of
realized with scalar operations as shown in Figure 6. The amplitude and phase are recovered by employing the output equations in Equation 4.
RMS-to-DC conversion methods
One of the easiest forms of amplitudeestimation is RMS-to-DC conversion. The root-mean-square (RMS) value yrms of a sinusoidal signal y
setting n = 3, which still guarantees that the component at 2fc is exactly canceled. A comparison of the original and half-period coherent demodulator is presented in Appendix B.
Summary
Table 1 compares the amplitudeestimation techniques discussed in this section. From the classification shown in Figure
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Figure 1:
(a) Time-domain example of an amplitude modulated signal with carrier frequency fc = 50 Hz, modulat...