A signal, f(t) = $${e^{ - at}}$$ u(t), where u(t) is the unit step function, is applied to the input of a low-pass filter having $$\left| {H(\omega )} \right| = {b \over {\sqrt {{\omega ^2} + {b^2}} }}$$.

Calculate the value of the ratio, $${a \over b}$$, for which 50% of the input signal energy is transferred to the output.

Obtain an expression for the signal in figure, for the signal $${v_3}(t)$$ in Fig for $${v_1}(t) = 100\cos (2000\pi t) + 4\sin (200\pi t)$$. Assume that $${v_2}(t)$$=$${v_1}(t)$$+0.1 $$v_1^2(t)$$ and that the BPF is an ideal unity gain filter with pass band from 800 Hz to 1200 Hz.