(Twoĭifferent stations cannot broadcast in frequency ranges that overlap.) This In fact, commercial AM radio signals are only allowed to broadcast a bandwidth ofġ0kHz, in order to maximize the number of available stations. Present in audible sound an AM signal would need to have a bandwidth of 40kHz. Is twice the maximum modulation frequency, The difference between the highest and the lowest frequency components of an AM radio signal, which On the carrier frequency, is capable of transmitting useful information. Only a signal that occupies a finite range of frequencies, centered This is an important result.Īn AM radio signal that only consists of a single frequency, such as the carrier frequency, transmits In other words, the signal would have to occupy a
#Bandwidth signal plus#
Minus 20kHz to the carrier frequency plus 20kHz.
Of sinusoidal oscillations with frequencies that range from the carrier frequency To carry all of the information present in audible sound, for which the appropriate modulation frequencies,įrom about 0 Hz to about 20kHz, the signal would have to consist of a superposition , whereas the lower sidebands correspond to the The upper sidebands correspond to the frequencies Is carried in so-called sideband frequencies which are equally spaced on either side of theĬarrier frequency. However, this spike carries no information. The largest spike corresponds to the carrier frequency, The spectrum consists ofĪ series of delta function spikes. Is shown, somewhat schematically, in Figure 53.
The AM frequency spectrum specified in Equations ( 763) and ( 764) Frequency spectrum of an AM radio signal.
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