Electrical Engineering

 Transmission-Media Transmission Media or Communications media  are the paths, or physical channels, is that, over which information travels from one place to another. A key aspect of communication is the movement of information electronically from one place to another. It may be as simple as sending information from one office to another in the same building, or it may be as far- reaching as sending information around the word. Whatever the case, information/signal must travel over some path from its source to its destination. What are the types of Transmission media? Signals are usually transmitted over some transmission media that are broadly classified in to two categories. Guided Media/bounded : These are those that provide a conduit from one device to another that include twisted-pair, coaxial cable and fiber-optic cable. A signal traveling along any of these media is directed and is contained by the physical limits of the medium. Twisted-pair and coaxial c...

Band Limited Signal   A signal is said to be a band limited signal if all of its frequency components are zero above a certain finite frequency. i.e it's power spectral density should be zero above the finite frequency. Figure 1 shows a signal g(t) that is band limited. Bandwidth requirements (communications) The channel bandwidths needed to transmit various types of signals, using various processing schemes. Every signal observed in practice can be expressed as a sum (discrete or over a frequency continuum) of sinusoidal components of various frequencies. The plot of the amplitude versus frequency constitutes one feature of the frequency spectrum (the other being the phase versus frequency). The difference between the highest and the lowest frequencies of the frequency components of significant amplitudes in the spectrum is called the bandwidth of the signal, expressed in the unit of frequency, hertz. Every communication medium (also called channel) is c...

The superhet radio or to give it its full name the super heterodyne receiver is one of the  most popular forms of receiver in use today. Virtually all broadcast radios, televisions  and many more types of receiver use the superhet or super heterodyne principle. First developed at the end of the First World War, with its invention credited to the American Edwin Armstrong, the use of the superhet has grown ever since the concept was first discovered.