Amplitude Modulation (AM) Process Overview

Amplitude Modulation (AM) Process Overview Modulation is the process of modifying the characteristic of one signal in accordance with some characteristic of another signal. In most cases, the information signal, be it voice, video, binary data, or some other information, is normally used to modify a higher-frequency signal known as the carrier. The information signal is usually called the modulating signal, and the higher-frequency signal which is being modulated is called the carrier or modulated wave. The carrier is usually a sine wave, while the information signal can be of any shape, permitting both analog and digital signals to be transmitted. In most cases, the carrier frequency is considerably higher than the highest information frequency to be transmitted. 4.2 Amplitude Modulation (AM) Amplitude modulation is the process of changing the amplitude of a relatively high frequency carrier signal in proportion with the instantaneous value of the modulating signal (information). The carrier frequency remains constant durin g the modulation process but that its amplitude varies in accordance with the modulating signal. An increase in the modulating signal amplitude causes the amplitude of the carrier to increase. Both the positive and negative peaks of the carrier wave vary with the modulating signal. An increase or decrease in the amplitude of the modulating signal causes a corresponding increase or decrease in both the positive and negative peaks of the carrier amplitude. If you interconnect the positive and negative peaks of the carrier waveform with an imaginary line, then you re-create the exact shape of the modulating information signal. This imaginary line on the carrier waveform is known as the envelope, and it is the same as the modulating signal. Amplitude modulation that results in two sidebands and a carrier is often called double sideband amplitude modulation (DSB-AM). In its basic form, amplitude modulation produces a signal with power concentrated at the carrier frequency and in two adja cent sidebands. Each sideband is equal in bandwidth to that of the modulating signal and is a mirror image of the other. Amplitude modulation is inefficient in terms of power usage and much of it is wasted. At least two-thirds of the power is concentrated in the carrier signal, which carries no useful information; the remaining power is split between two identical sidebands, though only one of these is needed since they contain identical information. 4.2.1 Mathematical Representation of AM Suppose we wish to modulate a simple sine wave on a carrier wave. The equation for the carrier wave of frequency fc, taking its phase to be a reference phase of zero, is The equation for the simple sine wave of frequency fm (the signal we wish to broadcast) is Amplitude modulation is performed simply by adding vm(t) to Vc. The amplitude-modulated signal is then The formula for vam(t) above may be written The broadcast signal consists of the carrier wave plus two sinusoidal waves each with a freque ncy slightly different from fc, known as sidebands. For the sinusoidal signals used here, these are at fc + fm and fc − fm. As long as the broadcast (carrier wave) frequencies are sufficiently spaced out so that these side bands do not overlap, stations will not interfere with one another.

Argument Essay Example | Topics and Well Written Essays - 1250 words - 1

Argument - Essay Example This paper will examine the perception towards slum tourism through literature exploration (Eveline & Rivke, p 113.) In the slum, setting there is nothing that is called garbage. Everyone in the slum wants a better life, Critics argue out the slums are exploitative, and they do not have a place in ethical travelers` itinerary. Professor David Fenell, at Brock University in Ontario, questioned the fact that the tourists visit places to take pictures and observe the lifestyles of the slum residents. He believes that the main purpose of slum tourism is to make the westerners feel better of their lifestyle in comparison to the slum habitants. They feel lucky on their life situation in comparison them. However, the proponents of slum tourism argue that ignoring poverty will not take it away. Slum tourism helps them to understand what poverty means. The big issue is how to conduct it (The New York Times, 2008) There conceptual ambiguity in slum tourism is based on a failure to set specific goals of tourism. The exact thing that attracts people during the tour in the slums and favelas is not precisely known (Manfred, p. 421). The use of poverty tourism indicates that poverty is the reason for the visits. The critiques argue that tours on the human wretchedness, infirmity, and unworthy living conditions should not be termed as a tourist attraction aspect. This issue has been largely fuelled by the mass media who present the pictures of such conditions. However, the proponents suggest that the word poverty tourism demonstrates the anticipated situation that propels them to go to slums (Eveline & Rivke, p 114.) Many organizers of slum tourism encourage active role-playing of the participants aimed at helping the residents. A church group in Mexico runs a tour of local garbage dumps where the scavengers collect trash to earn a living. In the tour, they make sandwiches and provide water in bottles for the scavenger.

Societies Essay Example | Topics and Well Written Essays - 1500 words

Societies - Essay Example It is complex play of power and dominance over the weaker defenseless sex, for superiority and satisfaction. The relationship between man and woman, and the significant role that a woman plays to keep the social and the family scene moving accounts for the hidden power with which women perform her duties regardless of time and age, in 20th century Muslim society or 17th century Chinese society. Men reserved the right to betray, women remained faithful, virtuous and honorable before marriage and even after husbands death. In Alifa Rifaats collection of short stories "Distant View of Minaret" dealing with 20th century Muslim women in Egypt, the reference is to the issues related to woman's suffrage in contemporary Egypt. In the story "Distant View of Minaret" the reference in that context is to lack of privileges, rights, and gender roles and expectations facing woman. Or even simply the basic "Men being in control of woman." However, two unexpected issues are brought up in her book and both are reflected in this story. The first being sex and the second being death.(Rifaat) In this story, she describes the sexual suppression and deprivation of a young married woman. She had long forgotten her desires, needs, and urges. She had adopted a passive role not only in the family lifestyle but in the bedroom as well. "The last time she made such an attempt, so desperate was she at this critical moment that she had dug her fingernails into his back compelling him to remain inside her." ((Rifaat p. 2) The story then goes onto explains how her husband pushes her away and screams at her as though she was trying to kill him. After this failed attempt to pursue her passion she began to feel as though she was asking too much and belittled herself. It made her feel ashamed and embarrassed to even think about the act. Later in the story it points out other occasions where her husband would suppress her urges purposely. "But on each occasion, when breathlessly imploring him to continue, he would-as though purposely to deprive her-quicken his movements and bring the act to an abrupt end." (Rifaat) The act that is supposed to involve two people in passion suddenly dissolves to one.(Rifaat) In his book "The Death of Woman Wang" Jonathan D. Spence projects the life of the rural China in seventeenth century, when the ideologies of Confucius was very strong on the society. The story is about a woman, Wang, who has an illicit affair with a man and she runs away with him. The adultery is dealt very harshly in Chinese society. The husband had the right to punish, penalize or even kill the man as well as the wife. Wang is finally tracked own and returned to her husband, and is finally killed in her own bed by her husband for the disgrace. The projection of the position and the role of the woman in the Chinese society at that time is illustrated revealing the status and position of the woman in the Chinese Confucian society. The story of is the central essence of the book, though it is revealed much later in the book, the picture which is revealed is of village life in T'an-ch'eng, the people, society, their everyday life and interactions between the people in the community. The role of marriage and the transformation which a woman goes through to keep her marriage is one of the key issues emphasized in both the stories