The "propagation channel" includes things like path loss, multipath reflection effects, multipath fading, Doppler (which can also be induced by moving reflectors in the environment, even if the radio terminals are stationary), fading due to material penetration (e.g., wall penetration, cloud penetration, etc.), etc., etc. In a wireless system this usually includes what I call "the propagation channel" as well as "the radio channel".
#Dish antenna gain equation license
A "channel" is generally, and I'll take a little license here, the medium through which a given set of information is conveyed. For the purposes of this discussion, and in order to fully illuminate the root of the issue, it is good to get a better understanding of what is meant by "channel effects" and "propagation effects". One source of confusion is what is meant by "propagation". So why is there so much confusion around this? Is the Friis equation incorrect? What's happening to our young people these days, anyway? Okay, we'll skip that last one, but we can address the first two, and learn why the propagation of an electromagnetic wave in free space is generally and practically completely independent of frequency. I am often surprised at the number and stature of engineers and researchers in the wireless industry who believe this to be true, though. The received power, P r, then goes up by the square of the wavelength! Clearly it is always desirable to use as low a frequency as possible, correct?Īt least it's evident that propagation is frequency dependent! It is evident from Equation (1) that, all other variables held constant, as the transmission frequency is reduced, the wavelength, λ, increases. Λ - The wavelength of the carrier (i.e., the center frequency of the radiated signal)ĭ - The distance between the transmitting and receiving antennas. G t - The gain of the transmitting antenna. Where the (λ/4πd) 2 term is sometimes referred to as the path loss or free space loss.
#Dish antenna gain equation pdf
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