Signal Processing & Antenna Theory Flashcards

What is the purpose of a matched filter in radar signal processing?

Answer: To maximize the signal-to-noise ratio at the output

A matched filter maximizes SNR by correlating the received signal with a replica of the transmitted signal.

Which antenna parameter describes how efficiently an antenna converts input power into radiated electromagnetic waves?

Answer: Radiation efficiency

Radiation efficiency is the ratio of radiated power to input power, accounting for ohmic losses in the antenna.

In marine radar, what does STC (Sensitivity Time Control) primarily compensate for?

Answer: Strong returns from nearby sea clutter

STC reduces receiver gain for returns arriving shortly after transmission to suppress strong sea clutter from nearby waves.

What phenomenon causes the radar horizon to extend slightly beyond the geometric horizon?

Answer: Tropospheric refraction bending the radar beam downward

Tropospheric refraction causes radar waves to bend slightly downward, extending the radar horizon beyond the geometric horizon.

A slotted waveguide antenna for marine radar primarily radiates energy through:

Answer: Slots cut into the waveguide walls that act as individual radiators

Slots cut into the broad wall of the waveguide interrupt surface currents, causing each slot to radiate as a small dipole.

What is the Nyquist sampling theorem's implication for radar A/D converters?

Answer: Sampling rate must be at least twice the highest signal frequency of interest

The Nyquist theorem requires sampling at least twice the maximum signal frequency to avoid aliasing.

In radar antenna theory, the first sidelobe level relative to the main beam for a uniformly illuminated aperture is approximately:

Answer: -13 dB

A uniformly illuminated aperture produces a sinc-function pattern with first sidelobes approximately 13.3 dB below the main beam.