# What Is an Antenna Aperture?

Andrew Kirmayer
Andrew Kirmayer

Antenna aperture is the area around an antenna where power is derived from the effects of an electromagnetic field. Also called the capture area, the antenna effective aperture is in the shape of a circle around the antenna. It is determined by a number of factors, including the available voltage and the density of the electromagnetic field present around the antenna. The size of the antenna aperture is dependent on the strength of the signal sent in a single direction. The gain will be larger for wider apertures, while narrower apertures will support a weaker gain.

The efficiency of antenna aperture can be measured in a couple of ways, including comparing the aperture of one antenna to another. A specialist can take a measurement of the gain and power in watts, and use mathematical calculations to characterize the aperture of the antenna. Bigger antennas tend to have larger apertures in comparison to smaller devices. Antenna effective aperture, however, is not always directly related to how big or small an antenna is. Shape, antenna type, polarization, power, and other design elements have enabled small antennas with apertures similar in size to physically bigger systems.

Aperture size is just one important function to consider with an antenna. Others include bandwidth, impedance, the width of the beam, and frequency. In large radio antennas, the aperture is important, as well as in smaller ones such as the aperture coupled microstrip antenna. It can have a square or circular shape and has a multiple layer structure with elements for forming the antenna’s aperture built in. Computer aided design software can be used to manufacture small antennas while calculating the antenna aperture before the device is even built.

Antenna aperture can be modified for smaller antennas used in cell phones, global positioning systems (GPS), and wireless networks. It is also important in calculating the level of received power. This level can be determined by multiplying the effective area by the strength of an incoming electromagnetic wave, while the level of wattage is important to consider as well. Overall, the antenna aperture is dependent on waves that come in toward the antenna on the same path power is directed outward. Aperture size helps users know how well an antenna can capture a signal, the area around it which can absorb an incoming signal, and whether or not it is suitable for a particular application.