Antenna Theory & Types Flashcards
7 cards from real CWS practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Antenna Theory & Types flashcards as text
In a MIMO wireless system, what is spatial multiplexing?
Answer: Transmitting separate, independent data streams simultaneously over multiple spatial paths to increase throughput
Spatial multiplexing leverages multiple independent signal paths between transmitter and receiver antenna arrays to send different data streams simultaneously, multiplying throughput.
What is the primary characteristic of a Yagi-Uda antenna that makes it useful for outdoor wireless links?
Answer: It is a highly directional antenna offering high gain and a narrow beamwidth
A Yagi-Uda antenna uses a driven element, reflector, and multiple director elements to produce high gain in a single direction with a very narrow beamwidth, ideal for point-to-point links.
Why is polarization matching important when aligning antennas in a point-to-point wireless link?
Answer: To maximize received signal strength and minimize polarization mismatch loss between the link endpoints
When transmit and receive antennas share the same polarization orientation (e.g., both vertical), signal transfer is maximized; a cross-polarized mismatch can cause up to 20–30 dB of signal loss.
What is the maximum conducted (transmitter output) power permitted by the FCC under Part 15 rules for 2.4 GHz WLAN devices?
Answer: 1 watt (30 dBm)
FCC Part 15 rules permit a maximum conducted transmit power of 1 watt (30 dBm) for 2.4 GHz 802.11 devices, with EIRP limits applied separately based on antenna gain.
What is beamforming as implemented in 802.11ac and 802.11ax (Wi-Fi 6) wireless standards?
Answer: Steering the transmitted signal toward specific client devices using phase-shifted antenna arrays to improve signal quality
Beamforming uses signal processing to adjust the phase and amplitude of signals across multiple antenna elements, effectively steering the transmitted beam toward a specific client device to improve SNR and throughput.
What is the key difference between a passive antenna and an active antenna system?
Answer: Active antennas integrate amplifiers or radio transceivers within the antenna assembly, while passive antennas contain only radiating elements without active components
Active antenna systems embed low-noise amplifiers (LNAs) or full radio transceivers directly into the antenna housing, minimizing cable losses and enabling advanced features like massive MIMO, unlike passive antennas that are purely passive radiating structures.
When an antenna specification lists a gain of 6 dBd, approximately what is its gain in dBi?
Answer: 8.15 dBi
A half-wave dipole reference (dBd) has approximately 2.15 dBi of gain over an isotropic radiator, so converting dBd to dBi requires adding 2.15 dB; 6 dBd + 2.15 = 8.15 dBi.