Q. Consider the Friis’ transmission equation 𝑃𝑅=(𝑃𝑇𝐺𝑇𝐺𝑅𝜆2) (4𝜋𝐷)2 ⁄ , where P𝑅 and 𝑃𝑇 are the received and the transmitted powers, respectively. G𝑇 and 𝐺𝑅 are the gain of transmitting and receiving antennas, respectively, 𝐷 is the distance between the transmitting and receiving antennas, and 𝜆 is the wavelength in free space. Given: 𝐺𝑇=𝐺𝑅=1.0,𝜆=0.30 m and PT = +10 dBm. Choose the distance (D), in km, from the following options at which the received power, PR = −90 dBm? Solution Given, P T ​ = + 10 dBm P R = − 90   dBm P R ​ = − 90 dBm G T = G R = 1 G T ​ = G R ​ = 1 (linear gain) λ = 0.30   m λ = 0.30 m P R ​ (in dBm) − P T ​   (in dBm):  Power difference in dB dB = 10^(dB/10) (in ratio) Pr = Pt.Gt.Gr.λ^2 / (4.π.D)^2 Or, Pr/Pt = Gt.Gr.λ^2 / (4.π.D)^2 Or, 10^(-90-10)/10 = Gt.Gr.λ^2 / (4.π.D)^2 Or, 10^-10 = 1.1.(0.3)^2 / (4.π.D)^2 Or, D = 15/2π Answer: Option B

  Q. In the circuit shown in the Figure, A and B are logic inputs and Y is the logic output. Which of the following logic operations is realized by the circuit? (A) NOR (B) OR (C) XOR (D) AND  Step 1: Identify the transistors Your diagram has 4 transistors. 2 PMOS The two transistors at the top, connected to V D D V_{DD} . 2 NMOS The two transistors at the bottom, connected to ground. Step 2: Remember the ON/OFF rule This is the most important part! Input at gate PMOS NMOS 0 (LOW) ON OFF 1 (HIGH) OFF ON So, PMOS works opposite to NMOS. Step 3: Understand the connections The two PMOS transistors are in series . Current can flow from V D D V_{DD} to Y Y only when both PMOS are ON . The two NMOS transistors are in parallel . The output can connect to ground if at least one NMOS is ON . Step 4: Check all input combinations Case 1: A = 0, B = 0 Both PMOS are ON. Both NMOS are OFF. ...