![]() There are several ways of using Scilab and the following paragraphs present three methods: using the console in the interactive mode, using the exec function against a le, using batch processing. I hope that this article has provided a good introduction, and we’ll continue the discussion in the next article. In this section, we make our rst steps with Scilab and present some simple tasks we can perform with the interpreter. This is a great reason to use Scilab (or MATLAB, or Octave) for frequency-domain analysis of FM systems. I haven’t extensively studied frequency modulation from the perspective of theoretical analysis, but as far as I can tell it is quite difficult to predict the characteristics of an FM spectrum based on mathematical relationships between the baseband and the carrier. If we return the modulation index to 4 and then reduce the baseband frequency by a factor of 2, the spectrum changes to this: Various factors affect the characteristics of FM spectra for example, if we lower the modulation index to 2, we get the following: It’s important to understand, however, that the specific features shown above are not present in all cases of frequency modulation. Second, the modulated bandwidth (about ☗0 kHz relative to the carrier frequency) is much larger than the bandwidth of the baseband signal (i.e., ☑0 kHz). There are two characteristics here that I want to mention: First, the sideband amplitude can be higher than the amplitude of the component at the carrier frequency. Plot(DFTHorizAxis, FM_DFT_magnitude(1:HalfBufferLength)) HorizAxisIncrement = (SamplingFrequency/2)/HalfBufferLength ĭFTHorizAxis = 0:HorizAxisIncrement:((SamplingFrequency/2)-HorizAxisIncrement) The following commands will produce a frequency-domain representation of the FM signal. We can add the baseband and the integrated baseband into the plot, just in case you want to ponder the relationship between these two signals and the FM waveform. ModulatedSignal_FM = sin((2*%pi*n / (SamplingFrequency/CarrierFrequency)) + (4*BasebandSignal_integral)) If we incorporate a modulation index of 4 into the command used to generate the FM data, the effect of the modulation is much more apparent: ![]() The mathematical relationship that forms the basis of frequency modulation is more complicated: The frequency-domain effects of amplitude modulation are fairly straightforward: the fundamental mathematical operation in an AM system is multiplication, and multiplication causes a spectrum to shift such that it is centered on a new frequency. How to Use Scilab to Analyze Amplitude-Modulated RF Signals.How to Perform Frequency-Domain Analysis with Scilab. ![]() Introduction to Sinusoidal Signal Processing with Scilab.Previous Articles on Scilab-Based Digital Signal Processing The Many Types of Radio Frequency Modulation (and other pages in Chapter 4 of the RF textbook).besselk(n,x) function computes modified Bessel functions of the second kind (K n ), for real order n and argument x. Learning to Live in the Frequency Domain (from Chapter 1 of AAC’s RF textbook) In Scilab besseli(n,x) function computes modified Bessel functions of the first kind (I n), for real order n and argument x.Computing a discrete Fourier transform can help you to analyze the ways in which RF modulation affects the spectrum of a carrier signal.
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