top of page

Antenna Interference And Antenna Isolation

Writer's picture: Santa Fe TechnologiesSanta Fe Technologies

Modern wireless devices tend to apply multiple communication techniques which utilize different frequencies. As a result of the development of wireless technology, there is a proliferation of antennas in smart devices. The crowding of antennas in a single unit can overdrive the receiver signal strength or degrade the receiver signal quality. For example, there are several transmitter and receiver antennas in a home security control box or smartphone. However, the lack of separation between antennas leads to interference issues. Minimizing interference problem can be achieved by antenna isolation design.


The consequences of tight coupling between antennas are aggravated by the trend of compact sizing in wireless -enabled devices. In certain devices, different antennas might operate under overlapped bandwidth. In such systems, there is a high probability for transmitted power to interfere with the receiver signal, which causes the loss of data, signal degradation, or circuit component failures. For example, cellular LTE, GPS/GNSS and Wi-Fi/BT antennas in a smartphone functioning simultaneously. For this reason, it is essential to include antenna isolation in such devices. S-parameters, S21 and S12, describe the effect on port 2 due to port 1 and vice versa and determine the insertion loss and isolation between the antennas. Antenna isolation measurements are carried out using specialized RF equipment. Large values of antenna isolation measurements indicate good antenna separation, meaning fewer interference issues.


Multiple antennas are often embedded in a single device. The lack of separation between antennas causes different interferences in the form of direct radiation, enclosure resonances, waveguide mode excitation, and noise coupling. Implementing sufficient antenna separation assists mitigate the following issues:


A. Transmitter noise: High-density communication generates broadband RF noises in the transmitter, called sidebands. The sidebands generated in the exciter stage get amplified in further stages until they reach the output stage. Noise levels in the transmitter can be worsened by the type of modulation as well.


B. Receiver desensitization: Receiver desensitization occurs when the receiver gets overloaded by off-frequency signals. The strength of the signals is so high that the receiver becomes dysfunctional. The receiver stops responding to any signals under these conditions.


C. Intermodulation issues: Receiver designs sometimes overload the front-end of the system, leading to intermodulation distortion. Receiver signals are mixed with unwanted interference signals, generating intermodulation distortion products in the receiver.


Antenna isolation is the approach of separating antennas that coexist so that there is only acceptable degrees of interference between systems. Antennas can be isolated in several ways. Some antenna isolation techniques are:


A. Physical separation: By vertical or horizontal separation of antennas, physical distance between the antennas is increased to prevent interference.


B. Radiation pattern optimization: The correlation coefficient between the antenna patterns can be reduced by directing the peak radiation from the antenna in different directions.


C. Pattern polarization: Antenna polarization generally allows the antenna to either receive or transmit signals with a particular polarization. Using different polarization minimizes the interference between antennas.


D. Frequency filtering: When physical separation, polarization, and orientation are not sufficient, further antenna isolation can be ensured by incorporating RF filters. RF filters minimize the received power of unwanted frequencies.

41 views0 comments

Comments


Santa Fe Technologies, INC.

TEL: +886-984-518915

info@stftechs.com

© 2017 by Santa Fe Tech., Inc. All rights reserved.

Santa Fe Logo are registered trademarks of Santa Fe Technologies, Inc.

bottom of page