Obtain an expression for modulation index of an AM wave. What are power and current relations in such a wave? Why is amplitude of modulating signal kept less than the amplitude of carrier wave?

Why is the amplitude of modulating signal kept less than the amplitude of carrier wave ?

What is the modulation index for an AM wave for which maximum amplitude is a and the minimum amplitudes is b.

The frequency of amplitude modulated wave is equal to

The amplitude of carrier wave is 12 . For modulation index of 50% the amplitude of modulating signal is _____________V.

If a carrier wave of amplitude 10mV is modulated by an audio signal of amplitude 2mV , then amplitude of LSF or USF is given by

If a carrier wave of amplitude 20mV is modulated by an audio signal of amplitude 4mV , then amplitude of LSF or USF is given by

The efficient transmission of signals is achieved by superimposing electrical audio signals on a high frequency carrier wave (the process is known as modulation). When the amplitude of high frequency carrier wave is changed in accordance with the intensity of modulating signal, it is called amplitude modulation. The extent to which the amplitude of carrier wave is changed by the signal is described by modulation factor. It is given as m="Amplitude change of carrier wave"/"Amplitude of unmodulated carrier wave" Let a carrier wave is represented by V_c=V_c cos omega_ct Let the modulation factor be m, the maximum change in amplitude of carrier wave is mV_c So, modulating signal can be represented as v_m=mV_c cosomega_mt So, the amplitude of modulated wave is =V_c+mV_c cosomega_m t Using this value, the instantaneous voltage of modulated wave is E=V_c cos omega_c t+ (mV_c)/2 cos (omega_c+omega_m)t + (mV_c)/2 cos (omega_c-omega_m ) t The above wave contains three frequencies namely, f_c, f_c+f_m and f_c-f_m . The frequencies f_c+f_m and f_c-f_m are called side band frequencies , USB and LSB respectively. The fraction of total power carried by side band frequencies is

If A_m and A_c are the amplitudes of modulating signal and carrier wave respectively, then modulation index is given by