Is a spiral antenna better? Yes, it provides higher ratio bandwidth, frequency-independent performance, and wide bandwidth patterns. This makes it ideal for applications with a strong signal, such as satellite communications.
Wireless technology has progressed a lot over the last decade- and spiral antennas could be in line with what’s to come.
In this article, we look closely at spiral antennae and the technologies they may help to power.
What is Spiral Antenna?
Spiral antennas are one of the most promising technologies for the future of wireless communication. They offer several advantages over traditional antennas, including better radiation efficiency and directivity performance.
It’s a type of antenna whose polarization and radiation patterns are unaffected by a wide bandwidth. It has two or more spiral shape arms.
Which helps to radiate electromagnetic waves more efficiently than traditional linear or planar antennas. As a result, stronger signals can be transmitted over longer distances with power.
In addition, spiral antennas have a much higher directivity than other antennas. This means they can focus their transmission on a specific target, such as a base station or another wireless device.
When was The Spiral Antenna Invented?
The first modern spiral antenna was invented in 1956 by Ed Turner. However, John Dyson and two other researchers from Illinois University patented a design in 1957.
Due to the military need for stronger antennas, the University of Illinois started antenna research in 1948. Initially, they wanted to create an antenna for supersonic aircraft.
Several fruitless efforts were made throughout their project. The making of a conical antenna was one of these unsuccessful efforts.
The issue with this particular conical antenna was unidirectional signals that mostly radiated their energy at an unexpected angle away from the cone’s tip.
After a year of research, they finally created the periodic log antenna, overcoming the conical antenna problem. These antennas are capable of receiving a 40:1 ratio bandwidth signal.
Basics of Spiral Antenna
Spiral antennas have LG (Low gain), but they can produce HG (Higher gain). They receive cross-polarized signals and transmit polarized waves from any direction. Spiral rotation determines antenna polarization.
Multi-spirals may be inserted. Spirals might be flat discs or screw threads. The spiral may be etched or printed over a particular dielectric media like microstrip antennas. Most spirals are Archimedean or logarithmic.
Spirals like those in JEM Engineering’s HSA product line are employed in defensive sensing applications for highly wideband antennas that fit in compact places.
Structure of Spiral Antenna
An antenna typically consists of two conducting spiral arms that radiate outward from the antenna’s central hub.
The polarization of an antenna is determined by the direction of the spiral’s rotation. For a more complex construction, many spirals may be used.
Winding rotation determines spiral structural tightness. Tight spirals exhibit frequency-independent radiation patterns.
As long as the helix is not excessively loose, winding twists have the least influence on spiral performance.
Conductor arm forms match when rotated 180°. This ensures the structure is circularly symmetrical between 0° and 180° on a plane cut.
Operation of Spiral Antenna
This antenna functions on the principle that electromagnetic waves are radiated more strongly with a smaller electrical current at low frequencies in a conductor with many coils and a large radius.
This antenna is suitable for operating in the multi-megahertz range. In general, low-frequency antennas are more efficient, but a spiral antenna is unsuitable for frequencies above 40 GHz.
Radiation of Spiral Antenna
Typically radiation pattern of a spiral antenna has a peak direction perpendicular to the spiral’s plane. The center of radiation for a spiral antenna is located at the point where the wavelength and the radius of the spiral are equal.
Spiral antennas have a lossy cavity supporting them, which limits the transmission to one side and increases the bandwidth at the cost of a 2-3 dB reduction and gain.
While the gain is higher than that of spirals with lossy cavities, the pattern bandwidths and axial ratio are much narrower.
Most of the simulations for spiral elements and arrays were performed in free space, although there may be occasions when it would be preferable to employ a ground plane.
Radiation Frequency of Spiral Antenna
The frequency range of a spiral antenna is from 1 GHz to 36 GHz. With a 5 dBi spiral antenna, the signal can go up to 1148 feet or 350-meters. High-power Spiral Antenna
It’s not always easy to get the best coverage when transmitting or receiving radio signals in a given area. The earth’s curvature blocks most signals at roughly 70 miles. So it’s impossible to go over the 100- and 150-mile range.
Feeding of Spiral Antenna
A microwave spiral antenna can be fed in various ways. One way is to feed it with a matched impedance transmission line such as a coaxial cable, microstrip, stripline, etc. In this case, the feed point is at one of the corners of the spiral.
Another way is to feed it with a line impedance or phase insensitive such as a waveguide, two-wire line, parallel wire line, etc. In this case, the feed point is at the center of the spiral.
This traditional feeding configuration isn’t suitable for the planar antenna. Feeding an archimedean antenna using two transmission lines linked to the outer diameter on opposing sides.
Experimental findings indicate that a 3:1 operating bandwidth radiation matching the center-feeding antenna is feasible.
Current Distribution of Spiral Antenna
Usually, the circular current distribution is used to represent current on spiral antennas. By using the FFT (Fast Fourier transform) method, complex Sommerfeld integral equations can be calculated.
There are two methods to calculate the current distribution on a spiral antenna:
- Conventional Current Distribution
This current distribution model on current antennas. However, the radial component on the spiral arms is absent in this model.
Therefore, it only applies to antennas with very low growth rates in which the radial part of the current is minimal.
- Modified current distribution
The modified current distribution retrieves the radiation parameters of spiral antennas with varying growth rates. The findings are validated by comparing them to those obtained from single-phase full simulations.
Polarization of Spiral Antenna
Unlike many common antennas, such as dipole or monopole, a spiral does not operate with an electric field polarized in one direction.
Rather, the spirals generate fields more uniformly distributed in all directions around the device.
Spiral antennas are typically polarized in a circular direction. The spiral elements are usually spaced far enough for a good axial ratio to produce a low side lobe level.
Advantages of Spiral Antenna
A Spiral antenna has many advantages. One of the most significant ones is that it helps reduce interference. Here are other benefits of a spiral antenna:
- Reduced radiation impedance
- Saves space in the event of a vehicle application
- Reduced size of the antenna
- Easy impedance matching
- Provides good coverage on the wireless systems
- Improves the overall performance of radio communications
Disadvantages of Spiral Antenna
Spiral antennas are very strong radio signal boosters, but they also have some disadvantages. Here are the disadvantages of spiral antennae.
- Because circular polarization bandwidth is limited.
- Difficulty in feeding.
- Poor efficiency because of a small loop.
- Power loss due to low heat resistance.
- Cavity loss due to non-uniform circular polarization.
- Artificial radiation fall-off in the horizontal plane.
- Poor radiation resistance.
Applications of Spiral Antenna
They’re used in applications that demand higher bandwidth and wireless communications. Other uses include frequency monitoring, direction-finding, GPS location and tracking, satellite communications, and military communications.
Why spiral antenna is frequency independent?
A spiral antenna has a very large bandwidth with 30:1. Which means the antenna still be proficient at 30 GHz even though the frequency rate is 1 GHz. That’s why the spiral antenna is frequency-independent.
Is spiral antenna omnidirectional?
Yes, the spiral antenna is omnidirectional. Because of the nature of a spiral antenna with many different lengths, the antenna gain is not uniform. Therefore it’s omnidirectional.
What are the types of spiral antenna?
There are different types of spiral antennae, such as star spiral, archimedean spiral, square spiral, and logarithmic. These types of antennas have different shapes, but there is almost the same function.
A spiral antenna is a type of polarized antenna that is often used in radio and microwave applications. It gets its name because it consists of a helical or spiral shape.
Spiral antennas are commonly used because they’ve a wide range of frequencies and offer a good level of directivity. So, that’s all about today. For any inquiries, please comment below.