ME or MEng Master of Engineering Master of Electrical Engineering 5

Question 1

In a switched-mode power supply, the 'right-half-plane (RHP) zero' in the boost converter transfer function is problematic because it:

Accepted Answer

Adds 90° phase lag while increasing gain, limiting achievable control bandwidth

Answer

An RHP zero increases gain at +20 dB/decade but simultaneously adds phase lag like a pole, constraining the control loop bandwidth to well below the RHP zero frequency.

Question 2

For a linear time-invariant system, the condition for BIBO (bounded-input bounded-output) stability is:

Accepted Answer

All poles of the transfer function lie in the open left-half s-plane

Answer

A continuous-time LTI system is BIBO stable if and only if all poles of H(s) have negative real parts (lie strictly in the left-half plane).

Question 3

In power electronics, what is the purpose of 'dead time' inserted between gate signals of complementary switches in a half-bridge converter?

Accepted Answer

To prevent shoot-through (cross-conduction) where both switches conduct simultaneously

Answer

Dead time ensures both high-side and low-side switches are off simultaneously before the complementary switch turns on, preventing a low-impedance short-circuit path.

Question 4

A digital FIR filter has linear phase if and only if its impulse response h[n] satisfies:

Accepted Answer

h[n] = -h[N-1-n] (antisymmetric) or h[n] = h[N-1-n] (symmetric)

Answer

Linear phase in FIR filters requires the impulse response to be either symmetric (Type I/II) or antisymmetric (Type III/IV) about its midpoint.

Question 5

In optical fiber communications, 'chromatic dispersion' causes pulse broadening because:

Accepted Answer

Different wavelength components travel at different group velocities in the fiber

Answer

Chromatic dispersion arises because the fiber's refractive index (and thus group velocity) varies with wavelength, spreading out spectrally diverse pulses.

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 5