The different types of dipole antennas used as RF antennas include half wave, multiple, folded, non-resonant, and so on. It is the simplest of all types of antennas. It does take any consideration about the absolute size of the dipole antenna. The short dipole antenna is made up of two co-linear conductors that are placed end to end, with a small gap between conductors by a feeder.

A Dipole is considered as short if the length of the radiating element is less than a tenth of the wavelength. The short dipole antenna is made of two co-linear conductors that are placed end to end, with a small gap between conductors by a feeder. The short dipole antenna is infrequently satisfactory from an efficiency viewpoint because most of the power entering this antenna is dissipated as heat and resistive losses also become gradually high.

A monopole antenna is half of a simple dipole antenna located over a grounded plane as shown in the figure below.

The radiation pattern above the grounded plane will be same as the half wave dipole antenna, however, the total power radiated is half that of a dipole; the field gets radiated only in the upper hemisphere region. The directivity of these antennas become double compared to the dipole antennas. The monopole antennas are also used as vehicle mounted antennas as they provide the required ground plane for the antennas mounted above the earth.

Loop antennas share similar characteristics with both dipole and monopole antennas because they are simple and easy to construct. Loop antennas are available in different shapes like circular, elliptical, rectangular, etc. The fundamental characteristics of the loop antenna are independent of its shape. They are widely used in communication links with the frequency of around 3 GHz. These antennas can also be used as electromagnetic field probes in the microwave bands.

The circumference of the loop antenna determines the efficiency of the antenna as similar to that of dipole and monopole antennas. These antennas are further classified into two types: Electrically small loops of a single turn have small radiation resistance compared to their loss resistance. The radiation resistance of small loop antennas can be improved by adding more turns. Multi-turn loops have better radiation resistance even if they have less efficiency. Due to this, the small loop antenna are mostly used as receiving antennas where losses are not mandatory. Small loops are not used as transmitting antennas due to their low efficiency.

Resonant loop antennas are relatively large, and are directed by the operation of wavelength. They are also known as large loop antennas as they are used at higher frequencies, such as VHF and UHF, wherein their size is convenient. They can be viewed as folded-dipole antenna and deformed into different shapes like spherical, square, etc. Helical antennas are also known as helix antennas. They have relatively simple structures with one, two or more wires each wound to form a helix, usually backed by a ground plane or shaped reflector and driven by an appropriate feed.

The most common design is a single wire backed by the ground and fed with a coaxial line. In General, the radiation properties of a helical antenna are associated with this specification: Helical antennas have two predominate radiation modes: The axial mode is used in a wide range of applications. In the normal mode, the dimensions of the helix are small compared to its wavelength. This antenna acts as the short dipole or monopole antenna.

In the axial mode, the dimensions of the helix are same compared to its wavelength. This antenna works as directional antenna. Another antenna that makes use of passive elements is the Yagi-Uda antenna. This type of antenna is inexpensive and effective. It can be constructed with one or more reflector elements and one or more director elements. Yagi antennas can be made by using an antenna with one reflector, a driven folded-dipole active element, and directors, mounted for horizontal polarization in the forward direction.

The antennas operating at microwave frequencies are known as microwave antennas. These antennas are used in a wide range of applications. For spacecraft or aircraft applications — based on the specifications such as size, weight, cost, performance, ease of installation, etc. These antennas are known as rectangular microstrip antennas or patch antennas; they only require space for the feed line which is normally placed behind the ground plane. The major disadvantage of using these antennas is their inefficient and very narrow bandwidth, which is typically a fraction of a percent or, at the most, a few percent.

A Planar Inverted-F Antenna can be considered as a type of linear Inverted F antenna IFA in which the wire radiating element is replaced by a plate to increase the bandwidth. The advantage of these antennas is that they can be hidden into the housing of the mobile when compared to different types of antennas like a whip, rod or helical antennas, etc.

The other advantage is that they can reduce the backward radiation towards the top of the antenna by absorbing power, which enhances the efficiency. They provides high gain in both horizontal and vertical states. This feature is most important for any kind of antennas used in wireless communications. The antenna that comprises one or more dipole elements placed in front of a corner reflector, is known as corner-reflector antenna.

The directivity of any antenna can be increased by using reflectors. In case of a wire antenna, a conducting sheet is used behind the antenna for directing the radiation in the forward direction. The radiating surface of a parabolic antenna has very large dimensions compared to its wavelength. The geometrical optics, which depend upon rays and wavefronts, are used to know about certain features of these antennas. Certain important properties of these antennas can be studied by using ray optics, and of other antennas by using electromagnetic field theory.

One of the useful properties of this antenna is the conversion of a diverging spherical wavefront into parallel wave front that produces a narrow beam of the antenna. The various types of feeds that use this parabolic reflector include horn feeds, Cartesian feeds and dipole feed.

In this article, you have studied about the different types of antennas and their applications in wireless communications and the usage of Antennas in transmitting and receiving data. For any help regarding this article, contact us by commenting in the comment section below. I like to read about the types of antennas and I also want to know more about reconfigurable antenna.

Can you give some information about how to build quarter wavelength reconfigurable monopole antenna? It is truly a nice and useful piece of information. Please stay us informed like this.

Here’s a Quick Way to Know about Different Types of Antennas

Thank you for sharing. Hi Thank you so much for your feedback And once again please visit our International website http: I will also like to know more about Jampro, Katherine, Jupritech antennas and any other transmission antennas you know about. I will like to know there characteristics and properties. Thank you. And once again please visit our domestic website https: These elements are often identical. A log-periodic dipole array consists of a number of dipole elements of different lengths in order to obtain a somewhat directional antenna having an extremely wide bandwidth. The dipole antennas composing it are all considered "active elements" since they are all electrically connected together and to the transmission line.

A Yagi-Uda antenna or simply "Yagi" , has only one dipole element with an electrical connection; the other parasitic elements interact with the electromagnetic field in order to realize a directional antenna over a narrow bandwidth. There may be a number of so-called "directors" in front of the active element in the direction of propagation, and one or more "reflectors" on the opposite side of the active element. Greater directionality can be obtained using beam-forming techniques such as a parabolic reflector or a horn.

Since high directivity in an antenna depends on it being large compared to the wavelength, narrow beams of this type are more easily achieved at UHF and microwave frequencies. At low frequencies such as AM broadcast , arrays of vertical towers are used to achieve directionality [8] and they will occupy large areas of land. For reception, a long Beverage antenna can have significant directivity.

For non directional portable use, a short vertical antenna or small loop antenna works well, with the main design challenge being that of impedance matching. With a vertical antenna a loading coil at the base of the antenna may be employed to cancel the reactive component of impedance ; small loop antennas are tuned with parallel capacitors for this purpose.

An antenna lead-in is the transmission line , or feed line , which connects the antenna to a transmitter or receiver. The " antenna feed " may refer to all components connecting the antenna to the transmitter or receiver, such as an impedance matching network in addition to the transmission line. In a so-called aperture antenna, such as a horn or parabolic dish, the "feed" may also refer to a basic antenna inside the entire system normally at the focus of the parabolic dish or at the throat of a horn which could be considered the one active element in that antenna system.

A microwave antenna may also be fed directly from a waveguide in place of a conductive transmission line.

Navigation menu

An antenna counterpoise , or ground plane , is a structure of conductive material which improves or substitutes for the ground. It may be connected to or insulated from the natural ground. In a monopole antenna, this aids in the function of the natural ground, particularly where variations or limitations of the characteristics of the natural ground interfere with its proper function. Such a structure is normally connected to the return connection of an unbalanced transmission line such as the shield of a coaxial cable.

An electromagnetic wave refractor in some aperture antennas is a component which due to its shape and position functions to selectively delay or advance portions of the electromagnetic wavefront passing through it.

• Antenna (radio).
• hero application university of alberta!
• download 3gp video songs for mobile bollywood!
• Properties of Antennas?
• wallpaper untuk samsung galaxy ace plus.

The refractor alters the spatial characteristics of the wave on one side relative to the other side. It can, for instance, bring the wave to a focus or alter the wave front in other ways, generally in order to maximize the directivity of the antenna system. This is the radio equivalent of an optical lens. An antenna coupling network is a passive network generally a combination of inductive and capacitive circuit elements used for impedance matching in between the antenna and the transmitter or receiver.

This may be used to improve the standing wave ratio in order to minimize losses in the transmission line and to present the transmitter or receiver with a standard resistive impedance that it expects to see for optimum operation. It is a fundamental property of antennas that the electrical characteristics of an antenna described in the next section, such as gain , radiation pattern , impedance , bandwidth , resonant frequency and polarization , are the same whether the antenna is transmitting or receiving.

This is a consequence of the reciprocity theorem of electromagnetics. A necessary condition for the aforementioned reciprocity property is that the materials in the antenna and transmission medium are linear and reciprocal. Reciprocal or bilateral means that the material has the same response to an electric current or magnetic field in one direction, as it has to the field or current in the opposite direction.

Most materials used in antennas meet these conditions, but some microwave antennas use high-tech components such as isolators and circulators , made of nonreciprocal materials such as ferrite. The majority of antenna designs are based on the resonance principle. This relies on the behaviour of moving electrons, which reflect off surfaces where the dielectric constant changes, in a fashion similar to the way light reflects when optical properties change.

In these designs, the reflective surface is created by the end of a conductor, normally a thin metal wire or rod, which in the simplest case has a feed point at one end where it is connected to a transmission line. The conductor, or element , is aligned with the electrical field of the desired signal, normally meaning it is perpendicular to the line from the antenna to the source or receiver in the case of a broadcast antenna.

The radio signal's electrical component induces a voltage in the conductor. This causes an electrical current to begin flowing in the direction of the signal's instantaneous field. When the resulting current reaches the end of the conductor, it reflects, which is equivalent to a degree change in phase. That means it has undergone a total degree phase change, returning it to the original signal. The current in the element thus adds to the current being created from the source at that instant. This process creates a standing wave in the conductor, with the maximum current at the feed.

The ordinary half-wave dipole is probably the most widely used antenna design. The physical arrangement of the two elements places them degrees out of phase, which means that at any given instant one of the elements is driving current into the transmission line while the other is pulling it out.

Monopoles, which are one-half the size of a dipole, are common for long-wavelength radio signals where a dipole would be impractically large. Another common design is the folded dipole , which is essentially two dipoles placed side-by-side and connected at their ends to make a single one-wavelength antenna.

The standing wave forms with this desired pattern at the design frequency, f 0 , and antennas are normally designed to be this size. This allows some flexibility of design in terms of antenna lengths and feed points. Antennas used in such a fashion are known to be harmonically operated. Antennas that are required to be small compared to the wavelength sacrifice efficiency and cannot be very directional.

At higher frequencies UHF, microwaves trading off performance to obtain a smaller physical size is usually not required. The quarter-wave elements imitate a series-resonant electrical element due to the standing wave present along the conductor. At the resonant frequency, the standing wave has a current peak and voltage node minimum at the feed. In electrical terms, this means the element has minimum reactance , generating the maximum current for minimum voltage.

This is the ideal situation, because it produces the maximum output for the minimum input, producing the highest possible efficiency. Contrary to an ideal lossless series-resonant circuit, a finite resistance remains corresponding to the relatively small voltage at the feed-point due to the antenna's radiation resistance as well as any actual electrical losses. Recall that a current will reflect when there are changes in the electrical properties of the material.

In order to efficiently send the signal into the transmission line, it is important that the transmission line has the same impedance as the elements, otherwise some of the signal will be reflected back into the antenna. This leads to the concept of impedance matching , the design of the overall system of antenna and transmission line so the impedance is as close as possible, thereby reducing these losses. Impedance matching between antennas and transmission lines is commonly handled through the use of a balun , although other solutions are also used in certain roles.

An important measure of this basic concept is the standing wave ratio , which measures the magnitude of the reflected signal. Using the appropriate transmission wire or balun, we match that resistance to ensure minimum signal loss. Feeding that antenna with a current of 1 ampere will require 63 volts of RF, and the antenna will radiate 63 watts ignoring losses of radio frequency power.

Now consider the case when the antenna is fed a signal with a wavelength of 1. Electrically this appears to be a very high impedance. The antenna and transmission line no longer have the same impedance, and the signal will be reflected back into the antenna, reducing output. This could be addressed by changing the matching system between the antenna and transmission line, but that solution only works well at the new design frequency.

The end result is that the resonant antenna will efficiently feed a signal into the transmission line only when the source signal's frequency is close to that of the design frequency of the antenna, or one of the resonant multiples. This makes resonant antenna designs inherently narrowband, useful for a small range of frequencies. Sometimes the resulting lower electrical resonant frequency of such a system antenna plus matching network is described using the concept of electrical length , so an antenna used at a lower frequency than its resonant frequency is called an electrically short antenna [14].

Then it may be said that the coil has lengthened the antenna to achieve an electrical length of 2. For ever shorter antennas requiring greater "electrical lengthening" the radiation resistance plummets approximately according to the square of the antenna length , so that the mismatch due to a net reactance away from the electrical resonance worsens. Or one could as well say that the equivalent resonant circuit of the antenna system has a higher Q factor and thus a reduced bandwidth [14] , which can even become inadequate for the transmitted signal's spectrum.

The amount of signal received from a distant transmission source is essentially geometric in nature due to the inverse-square law , and this leads to the concept of effective area. This measures the performance of an antenna by comparing the amount of power it generates to the amount of power in the original signal, measured in terms of the signal's power density in Watts per square metre. A half-wave dipole has an effective area of 0. If more performance is needed, one cannot simply make the antenna larger.

Although this would intercept more energy from the signal, due to the considerations above, it would decrease the output significantly due to it moving away from the resonant length. In roles where higher performance is needed, designers often use multiple elements combined together. Returning to the basic concept of current flows in a conductor, consider what happens if a half-wave dipole is not connected to a feed point, but instead shorted out. But the overall current pattern is the same; the current will be zero at the two ends, and reach a maximum in the center.

Thus signals near the design frequency will continue to create a standing wave pattern. Any varying electrical current, like the standing wave in the element, will radiate a signal. In this case, aside from resistive losses in the element, the rebroadcast signal will be significantly similar to the original signal in both magnitude and shape.

Different types of Antennas with Properties and thier Working

If this element is placed so its signal reaches the main dipole in-phase, it will reinforce the original signal, and increase the current in the dipole. Elements used in this way are known as passive elements. A Yagi-Uda array uses passive elements to greatly increase gain. It is built along a support boom that is pointed toward the signal, and thus sees no induced signal and does not contribute to the antenna's operation.

The end closer to the source is referred to as the front. Near the rear is a single active element, typically a half-wave dipole or folded dipole. Passive elements are arranged in front directors and behind reflectors the active element along the boom. The Yagi has the inherent quality that it becomes increasingly directional, and thus has higher gain, as the number of elements increases. However, this also makes it increasingly sensitive to changes in frequency; if the signal frequency changes, not only does the active element receive less energy directly, but all of the passive elements adding to that signal also decrease their output as well and their signals no longer reach the active element in-phase.

It is also possible to use multiple active elements and combine them together with transmission lines to produce a similar system where the phases add up to reinforce the output. The antenna array and very similar reflective array antenna consist of multiple elements, often half-wave dipoles, spaced out on a plane and wired together with transmission lines with specific phase lengths to produce a single in-phase signal at the output. The log-periodic antenna is a more complex design that uses multiple in-line elements similar in appearance to the Yagi-Uda but using transmission lines between the elements to produce the output.

Reflection of the original signal also occurs when it hits an extended conductive surface, in a fashion similar to a mirror. This effect can also be used to increase signal through the use of a reflector , normally placed behind the active element and spaced so the reflected signal reaches the element in-phase. For this reason, reflectors often take the form of wire meshes or rows of passive elements, which makes them lighter and less subject to wind-load effects , of particular importance when mounted at higher elevations with respect to the surrounding structures.

The parabolic reflector is perhaps the best known example of a reflector-based antenna, which has an effective area far greater than the active element alone. The antenna's power gain or simply "gain" also takes into account the antenna's efficiency, and is often the primary figure of merit. Antennas are characterized by a number of performance measures which a user would be concerned with in selecting or designing an antenna for a particular application.

A plot of the directional characteristics in the space surrounding the antenna is its radiation pattern. The frequency range or bandwidth over which an antenna functions well can be very wide as in a log-periodic antenna or narrow as in a small loop antenna ; outside this range the antenna impedance becomes a poor match to the transmission line and transmitter or receiver. Use of the antenna well away from its design frequency affects its radiation pattern , reducing its directive gain. Generally an antenna will not have a feed-point impedance that matches that of a transmission line; a matching network between antenna terminals and the transmission line will improve power transfer to the antenna.

The matching network may also limit the usable bandwidth of the antenna system. It may be desirable to use tubular elements, instead of thin wires, to make an antenna; these will allow a greater bandwidth. Or, several thin wires can be grouped in a cage to simulate a thicker element. This widens the bandwidth of the resonance. Amateur radio antennas that operate at several frequency bands which are widely separated from each other may connect elements resonant at those different frequencies in parallel. Most of the transmitter's power will flow into the resonant element while the others present a high impedance.

Another solution uses traps , parallel resonant circuits which are strategically placed in breaks along each antenna element. When used at one particular frequency band the trap presents a very high impedance parallel resonance effectively truncating the element at that length, making it a proper resonant antenna. At a lower frequency the trap allows the full length of the element to be employed, albeit with a shifted resonant frequency due to the inclusion of the trap's net reactance at that lower frequency. The bandwidth characteristics of a resonant antenna element can be characterized according to its Q where the resistance involved is the radiation resistance , which represents the emission of energy from the resonant antenna to free space.

The Q of a narrow band antenna can be as high as On the other hand, the reactance at the same off-resonant frequency of one using thick elements is much less, consequently resulting in a Q as low as 5. Antennas for use over much broader frequency ranges are achieved using further techniques. Adjustment of a matching network can, in principle, allow for any antenna to be matched at any frequency. Thus the small loop antenna built into most AM broadcast medium wave receivers has a very narrow bandwidth, but is tuned using a parallel capacitance which is adjusted according to the receiver tuning.

On the other hand, log-periodic antennas are not resonant at any frequency but can be built to attain similar characteristics including feedpoint impedance over any frequency range. These are therefore commonly used in the form of directional log-periodic dipole arrays as television antennas. Gain is a parameter which measures the degree of directivity of the antenna's radiation pattern. A high-gain antenna will radiate most of its power in a particular direction, while a low-gain antenna will radiate over a wider angle. This dimensionless ratio is usually expressed logarithmically in decibels , these units are called "decibels-isotropic" dBi.

Since the gain of a half-wave dipole is 2. High-gain antennas have the advantage of longer range and better signal quality, but must be aimed carefully at the other antenna. An example of a high-gain antenna is a parabolic dish such as a satellite television antenna. Low-gain antennas have shorter range, but the orientation of the antenna is relatively unimportant.

An example of a low-gain antenna is the whip antenna found on portable radios and cordless phones. Antenna gain should not be confused with amplifier gain , a separate parameter measuring the increase in signal power due to an amplifying device placed at the front-end of the system, such as a low-noise amplifier. The effective area or effective aperture of a receiving antenna expresses the portion of the power of a passing electromagnetic wave which it delivers to its terminals, expressed in terms of an equivalent area. Since the receiving antenna is not equally sensitive to signals received from all directions, the effective area is a function of the direction to the source.

Due to reciprocity discussed above the gain of an antenna used for transmitting must be proportional to its effective area when used for receiving. Therefore, the effective area A eff in terms of the gain G in a given direction is given by:. Therefore, the above relationship between gain and effective area still holds. These are thus two different ways of expressing the same quantity.

A eff is especially convenient when computing the power that would be received by an antenna of a specified gain, as illustrated by the above example. The radiation pattern of an antenna is a plot of the relative field strength of the radio waves emitted by the antenna at different angles in the far-field. It is typically represented by a three-dimensional graph, or polar plots of the horizontal and vertical cross sections. The pattern of an ideal isotropic antenna , which radiates equally in all directions, would look like a sphere. Many nondirectional antennas, such as monopoles and dipoles , emit equal power in all horizontal directions, with the power dropping off at higher and lower angles; this is called an omnidirectional pattern and when plotted looks like a torus or donut.

The radiation of many antennas shows a pattern of maxima or " lobes " at various angles, separated by " nulls ", angles where the radiation falls to zero. This is because the radio waves emitted by different parts of the antenna typically interfere , causing maxima at angles where the radio waves arrive at distant points in phase , and zero radiation at other angles where the radio waves arrive out of phase.

In a directional antenna designed to project radio waves in a particular direction, the lobe in that direction is designed larger than the others and is called the " main lobe ". The other lobes usually represent unwanted radiation and are called " sidelobes ". The axis through the main lobe is called the " principal axis " or " boresight axis ".

The space surrounding an antenna can be divided into three concentric regions: These regions are useful to identify the field structure in each, although there are no precise boundaries. The far-field region is far enough from the antenna to ignore its size and shape: It can be assumed that the electromagnetic wave is purely a radiating plane wave electric and magnetic fields are in phase and perpendicular to each other and to the direction of propagation.

This simplifies the mathematical analysis of the radiated field. Efficiency of a transmitting antenna is the ratio of power actually radiated in all directions to the power absorbed by the antenna terminals. The power supplied to the antenna terminals which is not radiated is converted into heat. This is usually through loss resistance in the antenna's conductors, or loss between the reflector and feed horn of a parabolic antenna. Antenna efficiency is separate from impedance matching , which may also reduce the amount of power radiated using a given transmitter.

How much of that power has actually been radiated cannot be directly determined through electrical measurements at or before the antenna terminals, but would require for instance careful measurement of field strength. The loss resistance and efficiency of an antenna can be calculated. The loss resistance will generally affect the feedpoint impedance, adding to its resistive component.

That resistance will consist of the sum of the radiation resistance R r and the loss resistance R loss. If a current I is delivered to the terminals of an antenna, then a power of I 2 R r will be radiated and a power of I 2 R loss will be lost as heat. According to reciprocity , the efficiency of an antenna used as a receiving antenna is identical to the efficiency as defined above.

The power that an antenna will deliver to a receiver with a proper impedance match is reduced by the same amount. In some receiving applications, the very inefficient antennas may have little impact on performance. At low frequencies, for example, atmospheric or man-made noise can mask antenna inefficiency. Antennas which are not a significant fraction of a wavelength in size are inevitably inefficient due to their small radiation resistance. AM broadcast radios include a small loop antenna for reception which has an extremely poor efficiency. This has little effect on the receiver's performance, but simply requires greater amplification by the receiver's electronics.

Contrast this tiny component to the massive and very tall towers used at AM broadcast stations for transmitting at the very same frequency, where every percentage point of reduced antenna efficiency entails a substantial cost. The definition of antenna gain or power gain already includes the effect of the antenna's efficiency. Therefore, if one is trying to radiate a signal toward a receiver using a transmitter of a given power, one need only compare the gain of various antennas rather than considering the efficiency as well.

This is likewise true for a receiving antenna at very high especially microwave frequencies, where the point is to receive a signal which is strong compared to the receiver's noise temperature. However, in the case of a directional antenna used for receiving signals with the intention of rejecting interference from different directions, one is no longer concerned with the antenna efficiency, as discussed above.

In this case, rather than quoting the antenna gain , one would be more concerned with the directive gain , or simply directivity which does not include the effect of antenna in efficiency. The directive gain of an antenna can be computed from the published gain divided by the antenna's efficiency.

The polarization of an antenna refers to the orientation of the electric field E-plane of the radio wave with respect to the Earth's surface and is determined by the physical structure of the antenna and by its orientation. A simple straight wire antenna will have one polarization when mounted vertically, and a different polarization when mounted horizontally. Reflections generally affect polarization. Radio waves reflected off the ionosphere can change the wave's polarization.

For line-of-sight communications or ground wave propagation, horizontally or vertically polarized transmissions generally remain in about the same polarization state at the receiving location. Matching the receiving antenna's polarization to that of the transmitter can make a very substantial difference in received signal strength. Polarization is predictable from an antenna's geometry. An antenna's linear polarization is generally along the direction as viewed from the receiving location of the antenna's currents when such a direction can be defined.

For instance, a vertical whip antenna will transmit and receive in the vertical polarization. Antennas with horizontal elements are horizontally polarized.

• Types of Antennas;
• descargar wifi analyzer para blackberry.
• the weather channel download for android.
• big sean detroit download iphone?
• Antenna basics, antenna types, antenna functions?
• ios written in which language?
• .

Even when the antenna system has a vertical orientation, such as an array of horizontal dipole antennas, the polarization is in the horizontal direction corresponding to the current flow. The polarization of a commercial antenna is an essential specification. In the most general case, polarization is elliptical , meaning that the polarization of the radio waves varies over time.

Two special cases are linear polarization the ellipse collapses into a line as discussed above, and circular polarization in which the two axes of the ellipse are equal. In linear polarization the electric field of the radio wave oscillates back and forth along one direction. In circular polarization, the electric field of the radio wave rotates at the radio frequency circularly around the axis of propagation.