January 30, 2012
University of Phoenix
Technology is constantly changing in communications. The analog signal was used for several years and was limited in number and did not have the ability to handle the amount of data interchange used today, because of the size requirements. Analog signals are still used today, but are more complex and are in most circumstances converted to a digital signal. This paper will compare the different types of analog and digital technology we used and are currently using today. Telecommunication: Analog/Digital Conversions
In the data communication world, there are two basic types of signals that are used in transmitting media: analog and digital. One form of data is captured is referred to as analog signal that can vary in amplitude (strength) and frequency (distance between wave-like peaks). The distance can be measure between the peaks in cycles per seconds, referred to as Hertz (Hz). Additionally, with digital signals, there are two states: ‘off’ or ‘on’ that occur when there is a change in light levels. These signals are sent in a continuous flow and are measured in megahertz per second. This is similar in concept of the two hands of a clock that are constant in motion and represent time. 1 Both frequency and amplitude can be used to encode data.2 An example of analog to digital is the process of faxing. The user starts with a piece of paper (analog), and inserts it into a fax machine. The fax machine converts the text on the paper to a digital form. The modem in turn, converts it to analog. The Class 5 switch at the local exchange converts it to analog. At the other end, his friend via the receiving Class 4 switch converts it to digital. The Class 5 switch at the receiving end local exchange, converts it to analog. . The friend’s modem converts it to digital, and finally the receiving friend’s fax machine prints it out onto paper which is analog. Today, most networks are part digital and part analog. This requires the data to be converted into different forms. Codecs and modems perform the conversion between these different signal types. Another step is to convert the digital we want to transmit in an analog RF signal, which is accomplished via quadrature amplitude modulation (QAM). This was found to be an important step due to field tests that indicated leakage from the digital network, which requires 3 the use of an analog TV channel or CW carrier on the AGC pilot frequency in order for the older amps AGC to work properly. By raising RF level, improvement was noted in the carrier-to-noise ratio. Amplitude Modulation & Frequency Modulation
Amplitude modulation (AM) is a method used most commonly for transmitting information through a radio carrier wave. It works by adjusting the strength of the broadcasted signal relative to the information being sent. The final modulation consists of three components: carrier, lower side band, and upper side band. Various combinations of these components create different types of AM with different properties for information transfer. Also, modulation depth has a big influence on modulation properties. Amplitude modulation is inefficient in power usage; at least two-thirds of the power is concentrated in the carrier signal, which carries no useful information. In frequency modulation (FM), the amplitude of the wave is constant, and the frequency is manipulated to produce the information being sent. One of the advantages to manipulating the frequency is the ability to adjust for travel distance. Low frequency has the benefit to travel much farther distances than high frequency before i The modulation techniques are all analog for the 56k modem, Asymmetrical Digital Subscriber Line (ADSL), and Wireless Fidelity Wi-Fi. However, they are being moved to digital as technology advances.
Modulation technology-56K modem, Asymmetrical Digital Subscriber Line, and...