Subelement E: Antenna Systems- 5 Key Topics – 5 Exam Questions— Topic 39: Antenna Systems
Question 8-39E4
Element 8 (RADAR)The center of the transmitted lobe from a slotted waveguide array is:
Explanation
Slotted waveguide arrays are generally designed as traveling-wave antennas. As the electromagnetic wave propagates down the waveguide, each slot acts as a radiator. Due to the progressive phase shift of the wave along the length of the waveguide (where the phase velocity inside the waveguide differs from the speed of light in free space), the radiated energy from each slot combines to form a main lobe that is inherently steered. This causes the center of the transmitted lobe to be offset by several degrees from a line perpendicular to the antenna (also known as broadside).
Therefore, option A is correct. Option B is incorrect because true broadside radiation would require specific in-phase excitation of the slots, which is not typical for a traveling-wave slotted array. Options C and D are incorrect as the main lobe describes a direction of maximum radiation, not a physical point at either end of the antenna.
Related Questions
8-39E2 A typical shipboard RADAR antenna is a:8-39E3 Good bearing resolution largely depends upon:8-39E5 How does antenna length affect the horizontal beamwidth of the transmitted signal?8-39E6 What is the most common type of RADAR antenna used aboard commercial maritime vessels?8-3A1 Frequencies generally used for marine RADAR are in the ___ part of the radio spectrum.