08-11-2012, 11:26 AM
Antenna Tutorial
[attachment=38532]
AeroComm is engaged in the research, development and manufacture of highperformance,
low-cost, 2.4GHz radios. A significant portion of AeroComm customers are Original
Equipment Manufacturers (“OEMs”) that integrate these radios into their products. Each OEM
has unique antenna requirements to meet packaging and performance criteria. AeroComm has
worked with a number of these OEMs to identify off-the-shelf antenna solutions or has developed
proprietary antenna designs to meet specific needs.
An antenna is a crucial element in the successful design of any radio system. This paper
explores antenna characteristics and different types of antennas that OEMs should consider
when selecting an antenna.
Antenna Characteristics
An antenna is a device that is made to efficiently radiate and receive radiated
electromagnetic waves. There are several important antenna characteristics that should be
considered when choosing an antenna for your application as follows:
• Antenna radiation patterns
• Power Gain
• Directivity
• Polarization
Antenna Radiation Patterns
An antenna radiation pattern is a 3-D plot of its radiation far from the source. Antenna
radiation patterns usually take two forms, the elevation pattern and the azimuth pattern. The
elevation pattern is a graph of the energy radiated from the antenna looking at it from the side as
can be seen in Figure 1a. The azimuth pattern is a graph of the energy radiated from the antenna
as if you were looking at it from directly above the antenna as illustrated in Figure 1b. When you
combine the two grap
Directivity
The directive gain of an antenna is a measure of the concentration of the radiated power
in a particular direction. It may be regarded as the ability of the antenna to direct radiated power
in a given direction. It is usually a ratio of radiation intensity in a given direction to the average
radiation intensity.
Polarization
Polarization is the orientation of electromagnetic waves far from the source. There are
several types of polarization that apply to antennas. They are Linear, which comprises, Vertical,
Horizontal and Oblique, and circular, which comprises, Circular Right Hand (RHCP); Circular Left
Hand (LHCP), Elliptical Right Hand and Elliptical Left Hand. Polarization is most important if you
are trying to get the maximum performance from the antennas. For best performance you will
need to match up the polarization of the transmitting antenna and the receiving antenna.
Dipole Antenna
All dipole antennas have a generalized radiation pattern. First, the elevation pattern
shows that a dipole antenna is best used to transmit and receive from the broadside of the
antenna. It is sensitive to any movement away from a perfectly vertical position. You can move
about 45 degrees from perfect verticality before the performance of the antenna degrades by
more than half. Other dipole antennas may have different amounts of vertical variation before
there is noticeable performance degradation.
A sample elevation pattern can be seen above in Figure 1a. From the azimuth pattern,
you find that the antennas work equally well in a full 360 degrees around the antenna. This is
illustrated above in Figure 1b. This graph shows that the dipole antenna is not a directive
antenna. Its power is equally split through 360 degrees around the antenna. Physically, dipole
antennas are cylindrical in nature, and may be tapered or shaped on the outside to conform to
some size specification. The antennas are usually fed through an input coming up to the bottom
of the antenna but can be fed into the center of the antenna as well.
Multiple Element Dipole Antennas
Multiple element dipole antennas have some of the same general characteristics as the
dipole. We see a similar elevation radiation pattern, as well as a similar azimuth pattern. The
biggest differences will be the directionality of the antenna in the elevation pattern, and the
increased gain that is a result of using multiple elements.
By using multiple elements to construct the antenna, the antenna can be configured with
different amounts of gain. This allows for multiple antenna designs with similar physical
characteristics. As can be seen from the elevation pattern in Figure 2, multiple element dipole
antennas are very directive in the vertical plane. Since the dipole antenna radiates equally well
in all directions on the horizontal plane it is able to work equally well in any horizontal
configuration.
[attachment=38532]
AeroComm is engaged in the research, development and manufacture of highperformance,
low-cost, 2.4GHz radios. A significant portion of AeroComm customers are Original
Equipment Manufacturers (“OEMs”) that integrate these radios into their products. Each OEM
has unique antenna requirements to meet packaging and performance criteria. AeroComm has
worked with a number of these OEMs to identify off-the-shelf antenna solutions or has developed
proprietary antenna designs to meet specific needs.
An antenna is a crucial element in the successful design of any radio system. This paper
explores antenna characteristics and different types of antennas that OEMs should consider
when selecting an antenna.
Antenna Characteristics
An antenna is a device that is made to efficiently radiate and receive radiated
electromagnetic waves. There are several important antenna characteristics that should be
considered when choosing an antenna for your application as follows:
• Antenna radiation patterns
• Power Gain
• Directivity
• Polarization
Antenna Radiation Patterns
An antenna radiation pattern is a 3-D plot of its radiation far from the source. Antenna
radiation patterns usually take two forms, the elevation pattern and the azimuth pattern. The
elevation pattern is a graph of the energy radiated from the antenna looking at it from the side as
can be seen in Figure 1a. The azimuth pattern is a graph of the energy radiated from the antenna
as if you were looking at it from directly above the antenna as illustrated in Figure 1b. When you
combine the two grap
Directivity
The directive gain of an antenna is a measure of the concentration of the radiated power
in a particular direction. It may be regarded as the ability of the antenna to direct radiated power
in a given direction. It is usually a ratio of radiation intensity in a given direction to the average
radiation intensity.
Polarization
Polarization is the orientation of electromagnetic waves far from the source. There are
several types of polarization that apply to antennas. They are Linear, which comprises, Vertical,
Horizontal and Oblique, and circular, which comprises, Circular Right Hand (RHCP); Circular Left
Hand (LHCP), Elliptical Right Hand and Elliptical Left Hand. Polarization is most important if you
are trying to get the maximum performance from the antennas. For best performance you will
need to match up the polarization of the transmitting antenna and the receiving antenna.
Dipole Antenna
All dipole antennas have a generalized radiation pattern. First, the elevation pattern
shows that a dipole antenna is best used to transmit and receive from the broadside of the
antenna. It is sensitive to any movement away from a perfectly vertical position. You can move
about 45 degrees from perfect verticality before the performance of the antenna degrades by
more than half. Other dipole antennas may have different amounts of vertical variation before
there is noticeable performance degradation.
A sample elevation pattern can be seen above in Figure 1a. From the azimuth pattern,
you find that the antennas work equally well in a full 360 degrees around the antenna. This is
illustrated above in Figure 1b. This graph shows that the dipole antenna is not a directive
antenna. Its power is equally split through 360 degrees around the antenna. Physically, dipole
antennas are cylindrical in nature, and may be tapered or shaped on the outside to conform to
some size specification. The antennas are usually fed through an input coming up to the bottom
of the antenna but can be fed into the center of the antenna as well.
Multiple Element Dipole Antennas
Multiple element dipole antennas have some of the same general characteristics as the
dipole. We see a similar elevation radiation pattern, as well as a similar azimuth pattern. The
biggest differences will be the directionality of the antenna in the elevation pattern, and the
increased gain that is a result of using multiple elements.
By using multiple elements to construct the antenna, the antenna can be configured with
different amounts of gain. This allows for multiple antenna designs with similar physical
characteristics. As can be seen from the elevation pattern in Figure 2, multiple element dipole
antennas are very directive in the vertical plane. Since the dipole antenna radiates equally well
in all directions on the horizontal plane it is able to work equally well in any horizontal
configuration.