Antenna And Microwave Engineering- Revision Quiz

Directivity, gain, and aperture are directly related because they all refer to the ability of an antenna or sensor to focus and concentrate its radiation or reception in a specific direction. Directivity is a measure of how well an antenna can transmit or receive signals in a particular direction, while gain is a measure of the increase in signal strength achieved by an antenna compared to a reference antenna. Aperture, on the other hand, refers to the effective size of the antenna or sensor, which affects its directivity and gain. Therefore, all three concepts are interconnected and directly influence each other.

The far field is the region of the field of the antenna where the angular field distribution is independent of the distance. In this region, the radiated electromagnetic waves have spread out enough to form a nearly spherical wavefront. The far field is characterized by a constant angular field distribution, meaning that the pattern of the radiated electromagnetic waves remains the same regardless of the distance from the antenna. This region is important for long-range communication and is commonly used for applications such as radio broadcasting and satellite communication.

A half wave dipole antenna is a resonant antenna that is commonly used in radio communication. The radiation resistance refers to the resistance that is associated with the conversion of electrical energy into electromagnetic radiation. In the case of a half wave dipole, the radiation resistance is typically around 73 ohms. This value is a result of the antenna's physical dimensions and the wavelength of the transmitted signal. The radiation resistance plays a crucial role in determining the efficiency and performance of the antenna.

The solid angle is a measure of the amount of space an object or light source occupies in three-dimensional space. It is analogous to the concept of an angle in two-dimensional space. The unit used to measure solid angles is called the steradian. The other options listed, radian, elevation angle, and azimuthal angle, are all units or measures related to angles in two-dimensional space and are not applicable to measuring solid angles.

To find the field components of an antenna, the analysis should be started from the point of the radiation. This means that the analysis should begin at the specific location where the radiation is originating from. By starting from this point, it allows for a more accurate and focused analysis of the antenna's field components, enabling a better understanding of its behavior and performance.

The correct answer is "isotropic". An isotropic antenna is a hypothetical antenna that radiates power uniformly in all directions. It is used as a reference to compare the performance of other antennas. The term "isotropic" refers to the equal radiation in all directions, regardless of the polarization or frequency.

The helical antenna is a hybrid of a dipole and loop antenna. It consists of two half wave dipoles in the form of a helix. The helical shape of the antenna allows it to have a wider bandwidth and higher gain compared to a simple dipole or loop antenna. The combination of the dipole and loop elements in the helical antenna helps to achieve a more compact design while maintaining good performance characteristics.

The offset and offset Cassegrain feed techniques in a reflector antenna are designed to avoid blockage. In these techniques, the feed is positioned to the side of the main reflector, allowing the incoming and outgoing signals to pass unobstructed. This arrangement helps to minimize any blockage caused by the feed itself, resulting in improved antenna performance.