What’s so interesting about parabolic reflector antenna? All we know is that it’s the simplest form of the reflector antenna with a paraboloid shape reflector at the front of the feed element.
Because of its paraboloid shape, it has the capability for high aperture gain and narrow bandwidth. Apart from that, the bandwidth range falls between the radio and microwave region which makes it suitable for satellite communication as well.
Is there anything about these antennas that might surprise us? Yes! Its design, basic operating principle, advantages, and disadvantages will certainly show how important these antennas are. Read our thoroughly researched article to gather an in-detailed idea.
What is Parabolic Reflector Antenna?
The theory of parabolic antenna comes from the basic curve of parabola, which is two-dimensional. When this shape is transformed into a three-dimensional, the spherical wave-like structure turns into a shape known as a paraboloid.
The main aim of these types of reflector antenna is to receive and transmit information from one broadcasting tower to another. The feed element, also known as a focus point, radiates radial waves toward the whole reflector.
The reflecting property of the paraboloid transfers these radial waves into plane waves during the transmission of signals. On the other hand, these reflective surfaces also receive the plane waves and convert them to radial waves at the receiving end of the communication system.
In other words, these reflector antennas are also known as parabolic dish antenna for their radio, and TV communication capability. Additionally, the power gain of parabolic reflector antenna is high that’s because the bandwidth is dependent upon the feed antenna properties rather than the reflector antenna. This accounts for more versatility.
Basics Of Parabolic Reflector Antenna
The concept of turning radial waves into plane waves was first proposed by scientist Heinrich Hertz, in the year 1887. He later found out that the parabolic reflectors are the prime equipment to prove such a hypothesis.
he later cascaded the spark-excited dipole antennas with the parabolic reflectors and invented the aperture gain is high with a flexible bandwidth tolerance level.
Hertz later concluded that the invention of parabolic reflector antennas both transmits and receives satellite signals at the same time. A parabolic reflector antenna diagram is shown below for a better understanding:
Importance Of Parabolic Reflector Antenna
The feeding methods of parabolic reflector antenna, which results in high gain, are the main importance that caught scientists’ attention. Due to its high gain, it is compatible with satellite communication, TV broadcasting, Radio astronomy, and so on.
On top of that, the high aperture gain also results in less power loss in parabolic reflector antennas compared to any other antenna model. Additionally, it can be used for both signal receive and transmission.
Furthermore, the operating frequency range of this antenna is above 1 MHz which makes it also suitable for radio communication and connecting to wireless features as well.
Types Of Parabolic Reflector Antenna
The types of parabolic reflector antenna is dependent upon the shape of the reflectors and the arrangement of the feed elements to produce certain plane waves.
According to the shape of the reflectors. There are:
- Paraboloid Reflectors
These are the most common type of reflectors that are widely used in applications. The radial wave from the feed element is projected onto the reflecting surface and the result is plane waves.
- Cylindrical Reflectors
Another name for this type of reflector antenna is the dipole antenna. Though the cross-sectional area is parabolic, there is a cylindrical length that allows the radio waves to superimpose not at a point, but along a line.
- Shaped Beam Reflectors
This antenna type comes with lots of parabolic shapes. In other words, you can say these reflectors are modified to produce the desired shaped beam. In other models, you’ll also find four cylindrical reflectors forming circle reflectors for creating a strong beam at the focal point of the antenna.
According to the arrangement of the feed elements. There are:
- Axial Feed
This is the classic feed arrangement in paraboloid-shaped reflector antennas. The light source or the signal is fed to the reflector and then it is transmitted as plane waves, also light beams, to the receiving end.
As for the three-dimensional structures, these types of reflectors is also called spherical reflectors.
- Off-Axis Feed
These reflectors are asymmetric to keep the angle of incidence of the beam at one side. This keeps the feed structure off the incoming beam path, and hence doesn’t block the beam of light coming from the feed to the reflecting surface.
- Cassegrain Feed
This type of arrangement in the paraboloid reflector antenna consists of a secondary convex hyperboloid reflecting surface. The feed is kept at the paraboloid end which transmits the signals.
These signals are reflected upon the hyperboloid end and then to the paraboloid surface, thus producing the deserved plane waves. One advantage of this type of arrangement is that the aperture efficiency is high, falling between 65 to 70%.
And the other advantage is that it keeps the feed protected between the two reflectors. Additionally, this design makes it suitable for large satellite and radio communications.
- Gregorian Feed
The only difference in Gregorian feed is that it uses the concave secondary reflecting surface, instead of convex. Apart from that, the working principle of both feeds is similar.
Working And Design Of Parabolic Reflector Antenna
As we have already mentioned before, the working of parabolic reflector antenna includes both receiving and transmitting ends. If we think about the transmitting end, the collimated light, plane waves, is directed from the focus point where the conversion of radial or spherical waves happens.
If we’re talking about the beams of light traveling, the phase difference between the two reflected lights should be the same. We have also mentioned in the previous section that the main aim of these antennas is to produce high gain during the operation.
To do that, the design parameters of parabolic reflector antennas should be well-calculated. There are two parameters to consider during the design, the focal length compared to the aperture.
If the focal length is situated inside the aperture arc, then it will be difficult to produce the collimated beam from the surface, as shown in the diagram below:
On the other hand, the focal length is kept far away from the aperture arc, most of the radiating lights will miss the reflecting surface which will decrease the aperture efficiency. The diagram below will give a generalized idea:
Therefore, to determine the perfect focal length for the incoming light, parabolic reflector antenna formula for focal length is given by:
f=D216 H
where,
f= focal legnth
D= reflector or beam diameter
H=reflector depth
According to electronics desk, the geometry of the focal length is given by one-fourth of the diameter of the parabolic reflector. Additionally, it’s only a suggestion and the design will also depend upon the level of gain desired during the application of these antennas.
Radiation Pattern Of Parabolic Reflector Antenna
So, it’s time to talk about the parabolic reflector antenna radiation pattern. As the antennas are equipped with parabolic dish reflectors, the radiation pattern is most likely to consist of a big major lobe with several small lobes for the small bandwidth operation range.
The diagram below shows the radiation pattern of the parabolic dish or compound reflectors:
Though these antennas with larger reflectors provide sufficient gain, there are certain areas to compromise while using them. Check out the parabolic reflector antenna advantages and disadvantages in the later section.
Advantages Of Parabolic Reflector Antenna
The advantages of parabolic reflector antenna are as follows:
- Produce fewer minor lobes
We’ve already seen from the radiation pattern that there are some minor lobes located at lower frequency range in the parabolic reflect. But, in comparison to other antenna models, the effect of minor lobes is negligible in parabolic antennas which makes it beneficial for usage.
- High apertures gain and directivity
The feed element radiates the radial waves with high gain which are then reflected as plane waves with similar gain and phase difference. As the focal point is removable, it also accounts for high directivity.
- Less power loss
Due to the adjustment of focal length, high gain, and directivity, the parabolic antennas provide less power loss compared to other antennas during the operation.
- Excellent beam adjustment
As the designers gain the freedom to adjust the focal length to account for the gain or directivity, it also accounts for the beam of light as well. Hence, we can say that parabolic antennas also include excellent beam adjustment.
Disadvantages Of Parabolic Reflector Antenna
Here are some disadvantages of parabolic reflector antennas:
- Large Sized Antenna
Due to producing high gain and directivity of plane wave beams, there have to be larger reflectors. These parabolic mirrors take up a lot of space during the installation of the antenna which will also require additional labor for the settings.
- Higher Cost
Maintenance of these large reflectors will require more than one technician, which in turn increases the labor cost of the antenna.
- Bad Weather
As these antennas will be situated out in the sky, their performance might degrade depending on the harsh weather conditions. Though they are built-in with extreme weather tolerance, it’s a good practice to be aware of such situations.
Applications Of Parabolic Reflector Antenna
Down goes the list of parabolic reflector antenna applications, and they’re:
- Distant source satellite communication
- TV broadcasting or radio communication
- Wireless communication
- Radio astronomy
- Distant radar communication
- Lighting devices such as car lights
Read more
FAQs
How does a parabolic reflector work?
A parabolic reflector reflects all the radiating light beam that is being projected from the feed element. The main purpose of a parabolic reflector is to convert the radial waves to plane waves.
What’s the transmission range for parabolic antenna?
The signal transmission range for the parabolic antenna is given by 56 km (from the antenna to the antenna).
Can we use parabolic antennas for Wi-Fi?
Yes! Parabolic antennas are highly directional antennas which is also perfect for wireless communication, hence Wi-Fi.
Conclusion
So, we think now you can explain parabolic reflector antenna, its working principle, and its design. We can think of a number of reasons for choosing a parabolic antenna for communication, it has high aperture gain, directivity, and not to mention, its versatility.