ME or MEng Master of Engineering Master of Electrical Engineering 4

Question 1

In digital communication, what is the Nyquist intersymbol interference (ISI)-free condition for a pulse shaping filter?

Accepted Answer

The pulse has zero crossings only at multiples of the symbol period T

Answer

A pulse is ISI-free if it equals 1 at t=0 and 0 at all other sampling instants t=nT, which requires zero crossings at all nonzero multiples of T.

Question 2

A PID controller with derivative kick can be avoided by applying the derivative action to:

Accepted Answer

The process output y(t) only, not the reference r(t)

Answer

Applying derivative to y(t) instead of e(t) eliminates the 'derivative kick' that occurs when a step change in setpoint is introduced.

Question 3

In electromagnetic compatibility (EMC), the concept of 'ground loops' causes interference primarily through:

Accepted Answer

Magnetically induced voltages in loops formed by multiple ground paths

Answer

Ground loops act as antenna loops that pick up time-varying magnetic flux, inducing a voltage V = -dΦ/dt = -jωBA in the loop.

Question 4

For a first-order phase-locked loop (PLL), the closed-loop transfer function H(s) = ω_n/(s + ω_n) implies that the PLL:

Accepted Answer

Acts as a low-pass filter for phase deviations with bandwidth ω_n

Answer

H(s) = ω_n/(s+ω_n) is a low-pass transfer function; the PLL tracks slow phase changes (below ω_n) and attenuates fast phase noise.

Question 5

Which semiconductor device structure is used in insulated-gate bipolar transistors (IGBTs) to combine high input impedance with low on-state voltage drop?

Accepted Answer

MOSFET channel in series with a PNP BJT collector-emitter path

Answer

An IGBT uses a MOSFET input stage (high impedance gate) to drive a PNP bipolar transistor output stage, combining MOS controllability with BJT low saturation voltage.

ME or MEng Master of Engineering Practice Test

ME or MEng Master of Engineering Practice Test

ME or MEng Master of Engineering Master of Electrical Engineering 4