Parameters of Radiation Pattern (Half Power Beam Width, First Null Beam Width & Front to Back Ratio)

Summary

This engineering lecture video delves into antenna radiation patterns, explaining key parameters like major and minor lobes, side lobes, and back lobes. It covers polar and rectangular representations, emphasizing the significance of the major lobe's maximum radiation. The video also introduces concepts like half-power beam width and front-to-back ratio, crucial for understanding antenna directivity and efficiency.

Takeaways

• 📡 The video discusses parameters of radiation patterns for antennas, building on a previous explanation of different types of radiation patterns.
• 🌐 Isotropic antennas have a spherical radiation pattern, representing uniform radiation in all directions.
• 📶 Directional antennas exhibit radiation patterns with major lobes, side lobes, and back lobes, indicating varying strengths of radiation.
• 🔄 Omnidirectional antennas radiate in a plane, differing from the directional and isotropic types.
• 📊 Radiation patterns can be represented in both polar and rectangular formats, with the latter showing angles on the x-axis and radiation strength on the y-axis.
• 📶 The major lobe in a directional antenna's radiation pattern indicates the direction of maximum radiation.
• 🔵 Side lobes are regions of radiation pattern that have lower power strength compared to the major lobe.
• 🔶 The back lobe is the region opposite to the major lobe, typically having less power than the major lobe.
• 📏 Half power beam width is measured as the angular width of the major lobe from maximum gain to a point three decibels down.
• 🚫 First null beam width refers to the angular width of the major lobe between the first minima (null points) on either side of the maximum gain.
• 📉 The front to back ratio is a measure of antenna directivity, calculated as the ratio of the gain of the major lobe to that of the back lobe.

Q & A

What are the three categories of radiation patterns discussed in the previous video?

The three categories of radiation patterns discussed are isotropic antenna's radiation pattern (spherical), directional antenna's radiation pattern with major lobe, side lobes, and back lobe, and omnidirectional antenna's radiation pattern which radiates in a plane.

What does a radiation pattern represent?

A radiation pattern represents the strength of radiation of a given antenna, showing how the power is radiated in different directions.

What are the two types of representations for radiation patterns mentioned in the script?

The two types of representations for radiation patterns are polar representation and rectangular representation.

What is the significance of the major lobe in a directional antenna's radiation pattern?

The major lobe in a directional antenna's radiation pattern signifies the direction where maximum radiation occurs.

What is the definition of a lobe in the context of radiation patterns?

A lobe is the region of a radiation pattern that contains the power or exhibits field strength.

What is the difference between a major lobe and a back lobe?

A major lobe is the region of the radiation pattern containing the highest power or exhibiting the greatest field strength, while a back lobe is the lobe opposite to the major lobe.

What are minor lobes?

Minor lobes are all the lobes other than the major lobe, which include side lobes and back lobes.

How is the half power beam width defined?

The half power beam width is the angular width of the major lobe from the maximum gain to the point where the gain is three decibels down.

What does the term 'first null' refer to in a radiation pattern?

The term 'first null' refers to the first minima in the radiation pattern with respect to the major lobe.

What is the first null beam width?

The first null beam width is the angular width of the major lobe measured from the first null points on either side of the maximum gain.

How is the front to back ratio defined and what does it indicate?

The front to back ratio is defined as the ratio of the gain of the major lobe to the gain of the back lobe. It indicates the directivity of the antenna, with a higher ratio suggesting greater directivity.