An FDM system uses single-sideband modulation to combine 12 independent voice signals and then uses frequency modulation to transmit the composite band 0.3 to 3.4 kHz; the system allocates it a bandwidth of 4 kHz.

For each voice signal, only the lower sideband is transmitted. The subcarrier waves used for the first stage of modulation are defined by ck (t) A k cos (2pkA?0t), 0 < k=””>< 11.=”” the=”” received=”” signal=”” consists=”” of=”” the=”” transmitted=”” fm=”” signal=”” plus=”” white=”” guassian=”” noise=”” of=”” zero=”” mean=”” power=”” spectral=”” density=””>
(a) Sketch the power spectral density of the signal produced at the frequency discriminator output, showing both the signal and noise components.
(b) Find the relationship between the subcarrier amplitudes A k so that modulated voice signals have equal signal-to-noise ratios.