How to Measure Antenna Radiation Pattern
Antenna radiation pattern is a crucial parameter in the design and analysis of antennas. It provides essential information about the distribution of the antenna’s radiation in space, which is vital for various applications such as wireless communication, radar systems, and satellite communication. Accurate measurement of the antenna radiation pattern ensures optimal performance and helps in avoiding interference and multipath effects. In this article, we will discuss various methods to measure antenna radiation patterns and their respective advantages and limitations.
One of the most common methods to measure antenna radiation patterns is the far-field measurement technique. This method involves placing the antenna at a distance much larger than its largest dimension, typically 10 times the wavelength of the operating frequency. The antenna is then excited with a signal, and the radiation pattern is measured using a directional antenna or a set of sensors. The far-field measurement technique is widely used due to its simplicity and accuracy. However, it requires a large test range and can be time-consuming.
Another popular method is the near-field measurement technique, which involves measuring the electric and magnetic fields close to the antenna. The near-field data can then be used to calculate the far-field radiation pattern. Near-field measurements can be performed using a probe scanner or a network analyzer. The probe scanner method involves moving a probe along the surface of the antenna and measuring the fields at various points. The network analyzer method uses a probe to measure the reflection coefficient and transmission coefficient of the antenna. Both methods have their advantages and limitations, but the near-field technique is generally more time-consuming and requires specialized equipment.
The ground plane technique is another method used to measure antenna radiation patterns. This method involves placing the antenna on a ground plane and measuring the fields at various points above the plane. The ground plane technique is particularly useful for measuring the radiation pattern of compact antennas and can be performed in a smaller test range compared to the far-field and near-field methods. However, the accuracy of the ground plane technique depends on the characteristics of the ground plane and the antenna.
To improve the accuracy of antenna radiation pattern measurements, various calibration techniques can be employed. These techniques involve measuring the radiation pattern of a reference antenna with known characteristics and then correcting the measurements of the test antenna based on the reference antenna’s data. Calibration techniques can be categorized into open-calibration, closed-calibration, and hybrid calibration methods. Open-calibration methods require a separate reference antenna, while closed-calibration methods use the test antenna itself as the reference. Hybrid calibration methods combine both open and closed calibration techniques.
In conclusion, measuring antenna radiation patterns is a critical task in antenna design and analysis. Various methods, such as far-field, near-field, and ground plane techniques, can be used to measure the radiation pattern of an antenna. Each method has its advantages and limitations, and the choice of method depends on the specific requirements of the application. Additionally, calibration techniques can be employed to improve the accuracy of the measurements. By selecting the appropriate method and applying calibration techniques, engineers can ensure optimal antenna performance and minimize interference and multipath effects in wireless communication systems.
