Abstract This paper discusses how black holes are created. It studies the ideas of physicist John Mitchell, his discoveries and how Isaac Newton's physics ideas helped lead to his discoveries on black holes. It also covers white dwarfs (stellar corpses), the most famous being Sirius.
From the Paper "The black hole was first named by the English physicist John Mitchell in 1783, more than two hundred years ago. But what are these black holes? Do they really exist? Based on planet movement studies made by Tycho Brahe and Johannes Kepler, John Mitchell deduced the existence of a force that made the Sun, the Earth, the Moon and everything contained in the cosmos."
Abstract This paper analyzes and simulates the performance of the frequency modulation (FM). The paper begins with an introduction to FM modulation and provides a full mathematical background information in regards with the FM. (This includes FM spectral analysis and introducing and simulating the role of the Bessel function and the frequency sidebands). The FM bandwidth requirements is discussed and simulated by using the MATLAB/Simulink. The simulation model and initialization steps are completely demonstrated and the results are discussed. The effect of adding noise to a FM modulated signal is analyzed and the results are presented. (This includes analysis of threshold effect and the mathematical relationship between signal to noise and carrier to noise.) The results of practical measurements are presented at the end of each part. The paper includes figures and graphs.
Contents:
1. Abstract
2. Frequency Modulation
A. Description:
B. Why Modulation?
C. Modulation Types
D. FM Modulation
E. FM Spectral analysis
3. Determining Kf (the deviation constant)
A. DC Method
B. Time Domain method
C. The Spectrum Analyzer Method
D. FSK Method
4. Effect of Band-pass Filtering
Simulating the Effect of Band-pass Filtering using SIMULINK
5. Effect of Adding Noise to an FM Signal
6. Conclusion
7. References
From the Paper "As explained before, in FM modulation, there is a linear relation between frequency deviation and voltage variation. (At the receiver site, demodulator use this property to extract the message from the modulated signal). In other word, this means that if we sketch the graph of modulated signal frequency versus message signal's voltage for an arbitrary FM system, the slope of the graph would be a constant value and would be equal to Kf (deviation constant)."
