Obtaining a dataset from bandpass function

Greetings, I am trying to obtain a filtered dataset from the bandpass function I applied to my sampled data. I am trying to demodulate the higher harmonic signal and plot the time-dependent components as a function of a distance. For that I need the filtered time signal, however I don't know how to obtain it from the bandpass function. Any help would be much appreciated.

So far my code looks like this :

clear;

clc;

%Tip oscillation variables

a = 10e-9; % Radius of the tip

f = 50000; % frequency of 50kHz

w = 2*pi*f; % Angular frequency of the oscilating tip

epsilon_tip = -10+2*1i; % Complex permittivity of the gold tip at lambda = 633 nm

%FFT variables

fs = 12*f; %fft sampling frequency = 5 times the oscillation frequency

T = 1/fs; % sampling period

N = 360; % Length of the signal

tf = (0:N-1)*T; % time vector

kf = 0:N/2;

freq = kf.*fs./N;

z = 20e-9+20e-9*cos(2*pi.*f.*tf); % distance between the tip and the sample surface

% Calculation of the near-field dipole-dipole interraction

epsilon_sample = 15; % permittivity of silicon sample at lambda = 633 nm

alpha = 4*pi*a^3*((epsilon_tip-1)./(epsilon_tip+2)); % Polarizability of the gold tip

beta = (epsilon_sample-1)./(epsilon_sample+1); % Dielectric surface response of the mirror dipole induced in the sample

alpha_eff = (((alpha.*(1+beta))./(1-(alpha.*beta)./(16*pi.*(a+z).^3)))).*1e+23; % Effective polarizability of the coupled tip-sample system

figure (5);

bandpass (alpha_eff, [99000 101000], fs);

Answer 1

[Paul]

Hi Patrik,

Is the output argument 'y' from bandpass the filtered time signal that is needed?

[Patrik Micek]

yes that is the one