Explore essential concepts of antennas and Multiple Input Multiple Output (MIMO) technology in mobile communications with this quiz. Enhance your understanding of signal propagation, diversity techniques, antenna types, and their roles in modern wireless systems.
Which fundamental role does an antenna play in a mobile communication system while transmitting signals?
Explanation: The correct answer is that an antenna converts electrical signals into electromagnetic waves for transmission over the air. Antennas do not simply store energy or increase the physical size of radio waves. While some antennas can have bandwidth-limiting properties, their primary role is not to limit the frequency range but to facilitate efficient signal transmission.
Which of the following antenna types is most commonly used in handheld mobile devices due to its compact size?
Explanation: Patch antennas are often used in mobile devices because they are flat, compact, and can be easily integrated into device enclosures. Parabolic dish antennas are large and suited for point-to-point links, not portable devices. Yagi-Uda and log-periodic antennas are mainly used for fixed installations requiring directional properties, not for compact handheld use.
In a 2x2 MIMO system, what do the numbers represent regarding antennas used for transmission and reception?
Explanation: A 2x2 MIMO system employs 2 antennas for transmitting and 2 for receiving signals, enabling spatial multiplexing and diversity. The numbers do not refer to frequencies, time slots, modulations, codes, users, or base stations. Incorrect options confuse hardware setup with unrelated technical parameters.
How does spatial diversity provided by antennas in a MIMO system improve signal quality in urban environments?
Explanation: Spatial diversity means using multiple antennas to receive multiple versions of the same signal, which helps reduce multipath fading. Lowering transmitted power below the noise floor would make communication unreliable, and bandwidth narrowing is unrelated to diversity gain. Echo interference is typically an unwanted effect, not a means of improving signal quality.
A dipole antenna typically has which form of radiation pattern in free space, making it suitable for general mobile applications?
Explanation: A dipole antenna radiates energy equally in all directions around its axis in the horizontal plane, making it omnidirectional and well-suited for mobile applications. Highly directional beams are characteristic of antennas like parabolic dishes. Null at all angles would mean the antenna cannot radiate, and a pure figure-eight pattern appears only in free space in the vertical plane, not as it’s commonly used.