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lec 2 communication

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  1. 19ECE214- COMMUNICATION THEORYLec2: Basics

  2. By Fourier theory, any waveform can be represented by a summation of a (possibly infinite) number of sinusoids, each with a particular amplitude, frequency and phase. Such a representation is referred to as the signal's spectrum (or it's frequency-domain representation). It is often easier to analyze signals and signal networks in terms of their spectral representations. By Fourier theory, any waveform can be represented by a summation of a (possibly infinite) number of sinusoids, each with a particular amplitude, frequency and phase. Such a representation is referred to as the signal's spectrum (or it's frequency-domain representation). It is often easier to analyze signals and signal networks in terms of their spectral representations.

  3. Basic Signals and Spectrums

  4. Band Width • Bandwidth is a key concept in several technological fields. • For Band pass signals, it describes the difference between upper and lower cut off frequencies • For Base band signals band width equivalent to the highest frequency

  5. Frequency Translation

  6. Frequency Translation • Frequency translation involves translating the signal from one region in frequency to another region. • The information in the original message signal at baseband frequencies can be recovered back even from the frequency-translated signal.

  7. Filters • A filter is a circuit capable of passing certain frequencies while attenuating other frequencies. • The four primary types of filters include the low-pass filter, the high-pass filter, the band-pass filter, and the notch filter (or the band-reject or band-stop filter). 

  8. Information signals are impressed upon a higher-frequency carrier signal for transmission. This process is called modulation. Now we’re dealing with two signals: 1. Original (“baseband”) information signal - frequency is too low to transmit efficiently 2. Higher frequency (“carrier”) signal - we can transmit this efficiently, so we use it to carry our information

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