GATE EC 2011 Question Paper (13-Feb-2011) (Shift 2)

In the circuit shown below, assume that the voltage drop across a forward biased diode is 0.7 V. The thermal voltage Vₜ = KT/q = 25 mV. The small signal input Vᵢ = V${}_P$ cos (ωt) where

V${}_P$ = 100 mV



The bias current I${}_{DC}$ through the diodes is

In the circuit shown below, assume that the voltage drop across a forward biased diode is 0.7 V. The thermal voltage $V_T$ = KT/q = 25 mV. The small signal input $V_i$ = $V_P$ cos (ωt) where

$V_P$ = 100 mV



The ac output voltage V${}_{ac}$ is

A four phase and an eight phase signal constellation are shown in figure



For the constraint that the minimum distance between pairs of signal points be d for both constellation the radii ${\mathrm{r}}_1$ and ${\mathrm{r}}_2$ of the circle are

Assuming high SNR and that all signals are equally probable, the additional average transmitted signal energy required by 8-ary PSK signal to achieve the same error probability as the 4-ary PSK is