PYQs Based Test - 09 : Communication and Optical Instrumentation

Let $s\left(t\right)=rect\left(\frac{t-3}{3}\right)$ be a signal passed through an AWGN (additive white Gaussian noise) channel with noise power spectral density (PSD) $\frac{N_0}{2}$ to get v(t). If v(t) is passed through a matched-filter that is matched to s(t), then output signal-to noise ratio (SNR) of the matched-filter is

The signal m(t) = cos(ω${}_m$ t) is SSB (single side-band) modulated with a carrier cos(ω${}_c$ t) to get s(t). The signal obtained by passing s(t) through an ideal envelope detector is

In a sinusoidal amplitude modulation scheme (with carrier) the modulated signal is given by A${}_m$ (t) = 100 cos(ω${}_c$ t) + 50 cos(ω${}_m$ t) cos(ω${}_c$ t), where ω${}_c$ is the carrier frequency and ω${}_m$ is the modulation frequency. The power carried by the sidebands in % of total power is _________%.

A 100 W light source emits uniformly in all directions. A photodetector having a circular active area whose diameter is 2 cm is placed 1 m away from the source, normal to the incident light. If the responsivity of the photodetector is 0.4 A/W, the photo-current generated in the detector, in units of mA, is

A signal cos (2πf${}_m$ t) modulates a carries cos(2πf${}_c$ t) using the double-sideband-with-carrier (DSB-WC) scheme to yield a modulated signal cos(2πf${}_c$ t) + 0.3 cos(2πf${}_m$ t) cos(2πf${}_c$ t). The modulation index is ________. (Answer should be rounded off to one decimal place)