ISRO Scientist or Engineer Electronics 2018
For the following questions answer them individually
A four port directional coupler has 4 : 1 power splitting ratio and has dissipation loss of 3dB. The coupler directivity is 40dB. What fraction of input power P1 will go to ports P2 and P3?
A cell phone transmits at a powerlevel of 800 mW with an antenna gain of 3.0 dB. The cell tower has an antenna gain of 10.0 dB and is at a distance of 5 km away. Transmission frequency is 600 MHz. Noise level at Receiver Input is -95 dBm and required Signal to Noise ratio to close the link is 5 dB. Find the link margin in dB. (assume $$\pi^2 = 10$$)
A resistor R1 = 4 kΩ is connected across the secondary of transformer for which L1 = 0.2H, L2 = 10H and flux coupling coefficient k = 0.5. Find the peak voltage across resistor R1 when 250 V peak voltage at 400 rad/sec is applied to primary winding of transformer.
For a network shown in figure, a steady state is reached with switch k is open. Switch is closed at time t = 0. Calculate $$\left(\frac{di_1}{dt}\right)$$ and $$\left(\frac{di_2}{dt}\right)$$ at t = 0+
Fourier transform of $$te^{-at} u(t)$$, (where a > 0, u(t) is the Unit step function) is :
