Chapter: 12th Physics : UNIT 10b : Communication Systems
Antenna Size
ANTENNA SIZE
Antenna is used at both transmitter
and receiver end. Antenna height is an important parameter to be discussed. The
height of the antenna must be a multiple of λ/4.
where λ is wavelength ( λ= c/υ ), c is the velocity of light and ν is the frequency of the signal to be transmitted.
An example
Let us consider two baseband
signals. One signal is modulated and the other is not modulated.
The frequency of the original
baseband signal is taken as ν = 10 kHz while the modulated signal is ν = 1 MHz.
The height of the antenna required
to transmit the original baseband signal of frequency ν = 10 kHz is
The height of the antenna required
to transmit the modulated signal of frequency ν = 1 MHz is
Comparing equations (10.2) and
(10.3), we can infer that it is practically feasible to construct an antenna of
height 75 m while the one with 7.5 km is not possible. It clearly manifests
that modulated signals reduce the antenna height and are required for long
distance transmission.
Related Topics