Q. A control system is shown in the Figure. Which option represents the correct transfer function of the system? Output of the upper block, C(s) = X(s)*1/(s+4) Output of the lower summing junction = 0. So, feedback signal is zero. So, final transfer function is 1/(s+4) Answer: Option B

  Q. Consider the circuit shown in the Figure with 𝑉𝑖=3 V and 𝑉𝐶𝐶=12 V. Assume 𝑉𝐵𝐸=0.7 V and 𝛽𝑑𝑐=99 for the BJT. Which of the following options is the correct value of the current 𝑰𝒐? Here, feedback is negative  so, V+ = V-  Or, Vi = VE = 3V Then, IE = 3 / 1 mA = 3 mA On the other hand, Ic = β.IB and IE = Ic + IB Or, IB = IE - Ic Or, IB = 3 - β.IB Or, IB(1+β) = 3 Or, IB = 3/100 mA = 30 micro-Ampere Answer: Option D

  For M-QAM (M-ary Quadrature Amplitude Modulation) , the baseband symbols are complex numbers with different amplitudes and phases , unlike M-PSK, where the amplitude is constant. The general baseband symbol is s k = I k + j Q k \boxed{s_k=I_k+jQ_k} where I k I_k is the in-phase component and Q k Q_k is the quadrature component. 1. 4-QAM 4-QAM has 4 symbols, with 2 possible values for each component: I , Q ∈ { − 1 , + 1 } I,Q\in\{-1,+1\} The baseband symbols are S = { − 1 − j , − 1 + j , 1 − j , 1 + j } \boxed{S=\{-1-j,-1+j,1-j,1+j\}} Symbol I I Q Q − 1 − j -1-j -1 -1 − 1 + j -1+j -1 +1 1 − j 1-j +1 -1 1 + j 1+j +1 +1 Each symbol represents log ⁡ 2 4 = 2 \log_2 4=2 bits. 2. 16-QAM 16-QAM has 16 symbols. The possible values of each component are I , Q ∈ { − 3 , − 1 , + 1 , + 3 } I,Q\in\{-3,-1,+1,+3\} Therefore, s k = I + j Q \boxed{s_k=I+jQ} for all 16 combinations of I I and Q Q . 16-QAM constellation Eac...