Compare AM and NBFM.
AM:
AM stand for amplitude modulation. Bandwidth of the amplitude modulated signal is \(2f_m\), where \(f_m\) is the maximum modulating signal frequency. The mathematical expression of AM waveform is defined as
\(S\left(t\right)=A_c\left(1+\mu x\left(t\right)\right)cos2\pi f_ct\)
Here μ is the modulation index and it is defined by the ratio between amplitude of the modulating signal and amplitude of the carrier signal. For truthful communication without distortion the modulation index varied from 0 to 1. Depend on the value of depth of modulation, the modulation processes may be classify in three broad categories such as under modulation, hundred percent modulation and over modulation. Signal contamination by the noise is less. Power requirement is higher than NBFM.
NBFM:
NBFM stand for narrow band frequency modulation. A narrow band FM is the FM wave with a small bandwidth. The modulation index β of narrow band FM is small as compared to one radian. Hence, the spectrum of narrowband FM consists of the carrier and upper side band and lower side band. The bandwidth of NBFM is \(2f_m\), where \(f_m\) is the maximum modulating signal frequency. Signal contamination by the noise is more than AM. Power requirement is less than AM.
The narrow band FM can be defined as
\({S\left(t\right)}_{FM}=E_csin\omega_ct+\beta\frac{E_c}{2}sin\left(\omega_c+\omega_m\right)t-\beta\frac{E_c}{2}sin\left(\omega_c+\omega_m\right)t\)
Explain with proper expression
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Fig. 14(a)
Fig.23