Signal Processing & Antenna Theory Flashcards

In radar signal processing, what is the purpose of the I/Q (in-phase/quadrature) demodulation scheme?

Answer: To recover both amplitude and phase of the received signal

I/Q demodulation extracts both the in-phase and quadrature components, preserving full complex signal information including amplitude and phase.

What is the relationship between radar range resolution and pulse width?

Answer: Range resolution = c × PW / 2

Range resolution equals c×τ/2 where τ is the pulse width, because signals must be separated by at least half the pulse duration in range.

Which type of antenna feed method for a parabolic dish results in feed blockage of the aperture?

Answer: Prime focus feed

A prime focus feed places the feed element at the focal point directly in front of the dish, partially blocking the aperture and increasing sidelobes.

Sea clutter in marine radar is most intense at which range condition?

Answer: Short ranges with high sea state

Sea clutter is strongest at short ranges where large sea waves produce intense backscatter returns that can mask small targets.

In a phased array radar antenna, beam steering is accomplished by:

Answer: Controlling the phase of each radiating element

Phased arrays steer the beam electronically by applying progressive phase shifts across the array elements to change the direction of constructive interference.

What is the purpose of a magnetron injection-locking technique in some marine radar transmitters?

Answer: To stabilize and control the magnetron's output frequency

Injection locking synchronizes the magnetron's frequency to a stable reference signal, improving frequency stability for coherent processing.

The antenna pattern's half-power beamwidth (HPBW) for a uniformly illuminated aperture of width D at wavelength λ is approximately:

Answer: 0.886 × λ/D radians

The 3 dB beamwidth of a uniformly illuminated aperture is approximately 0.886λ/D radians, derived from the sinc function zeros.