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Electromagnetic Waves in Communication NGSS Performance Expectation MS-P4-3 • Integrate qualitative scientific and technical information to support the claim that digitalized signals are a more reliable way to encode and transmit information than analog signals. Emphasis is on waves used for communication, including the conversation of binary patterns. • Waves carry energy, but did you know that WAVES ALSO CARRY MESSAGES • If my voice (sound ) travels in a Mechanical wave than how does my best friend hear my voice on my cell phone if my cell phone has electromagnetic waves? How does my favorite music artists’ voice play back once downloaded? Hmmmm…… Brain Pop Analog and digital Recording • A lot of our personal world is transmitted digitally in our cellphones: texts, selfies, and emails, but are all waves digital? • Lets see what Tim and Moby have to say about this • https://www.brainpop.com/technolog y/scienceandindustry/analoganddigita lrecording/ So what is Analog • In communication, signals are generated from a transmitter which are sent to receivers to create messages. • One type of Analog technology is a clock Analog • An analog watch tells the time with hands that sweep around a dial: the position of the hands is a measurement of time. It’s ANALOGOUS of the passing of time. Its not the actual passing of time, but it illustrates the passing of time. The ticking of the clock is constantly moving. Analog Before computers, everything was Analog Examples are an old style camera or an old cassette recording. Images captured on chemically treated paper were analogous of the true image and recordings of voice were captured on magnetized tape which was analogous of the true voice. Images and sound were clear. Other Areas of Anaolg Technology • Old telephone networks • Most television broadcasting at present • Radio broadcasting Analog Signals: The Basics Signal Amplitude Frequency = Cycle/Second A typical sine wave Time Cycle Amplitude and Cylce • Amplitude – Distance above reference line • Cycle – One complete wave – Amplitude is what give is AM Radio stations Frequency • Frequency – Cycles per second – Hertz is the unit used for expressing frequency • Frequency spectrum – Defines the bandwidth for different analog communication technologies – Frequency has to do with FM Radio stations Information Representation Using Analog Signals • Analog information is translated into electric pulses of varying amplitude – Analog signal is continuous – Denoted by Sine Wave – Analog technology records waveforms as they actually are – Digital • Digital is entirely different. • In digital technology, translation of information is into binary format (zero and one) where each bit is represented of two distinct amplitudes. – A bit is a one or a zero – A byte is a string of 8 ones and zeros. Digital Signal 1 0 1 1 0 1 0 0 Pulse Pulse Duration Time • A digital signal uses decrete (discontinuous) values • Digital is measured with Sampling • Lets watch this video • https://www.youtube.com/watch?v=b tgAUdbj85E&spfreload=1 Digital Advantage Easier to store information and takes up less space. Ex. MP3 or Kindle More secure:cellphone Editing Processing using computer technology Programmable services Better quality due to being able to reconstruct exact digital patterns at the receiving end Faster communication speeds are possible Digital Disadvantages • Analog is more accurate • Analog last longer – No one has the first email or cell phone conversation Sampling does not precisely capture the original wave when converted so it is not as accurate. Analog Digital Conversion 1 0 1 1 0 1 0 0 A to D Converters, Digital Signal Processors (DSP) etc. • So is Digital better than Analog? You be the judge