CTE Wireless & RF Engineering Flashcards

What is the purpose of a Low Noise Amplifier (LNA) placed at the front-end of a receiver?

Answer: To boost the received signal before it degrades in the receiver chain

An LNA amplifies the weak received signal before further processing, minimizing noise added by subsequent stages and improving overall receiver sensitivity.

In RF propagation, what phenomenon causes a signal to arrive at the receiver via multiple paths of different lengths?

Answer: Multipath fading

Multipath fading occurs when reflected, scattered, or diffracted copies of a signal arrive with different delays, causing constructive or destructive interference.

What is the link budget's 'fade margin' designed to account for?

Answer: Expected signal strength variations due to propagation anomalies and fading

Fade margin is extra dB added to the link budget to maintain the required SNR even when the signal fades due to weather, multipath, or other propagation impairments.

Which antenna type has a toroidal (doughnut-shaped) radiation pattern ideal for omnidirectional coverage in the horizontal plane?

Answer: Dipole antenna

A dipole antenna radiates equally in all horizontal directions with nulls at the tips, producing the classic toroidal pattern used for omnidirectional coverage.

In the context of 5G NR, what does 'beamforming' enable that traditional antennas cannot?

Answer: Spatially targeted transmission that increases gain toward specific users

Massive MIMO beamforming uses phase-shifted arrays to concentrate energy toward individual users, improving throughput and reducing interference.

What is the purpose of the Guard Interval (Cyclic Prefix) in OFDM systems?

Answer: To absorb inter-symbol interference caused by multipath delay spread

The cyclic prefix is a copy of the end of each OFDM symbol prepended to the beginning, giving the receiver time for multipath echoes to settle before sampling.