Efficiency improvements of normal mode helical antennas by folded configurations woong hyun jung, naobumi michishita and yoshihide yamada. The helical antenna is a hybrid of two simple radiating elements, the monopole and loop antenna. The axial mode is the most practical because it can use circular polarization over a wide bandwidth. Helical antennas have two popular modes of operation which is normal mode electrically small broadside and axial mode electrically large endfire 2. Helical antenna or helix has a long history and have attracted various study and development for more than 60 years since its first invention 1. The axial mode can exist over a wide range of frequencies and is also circularly polarized.
Parasitic quadrifilar helical antenna aeronetworks. Those operating in the normal mode are used for a mobile radio and in broadcasting antennas. Consequently, operation as a helical antenna is tied to the requirement of a. S vertical separation between turns for helical antenna. The radiation pattern is maintained in the axial mode over wide frequency ranges because of a natural. The antenna, in most cases, is mounted over a ground plane with a feed line connected between the ground plane and the. Long quadrifilar axialmode helical antenna wound in the righthand sense. Depending on the helix geometry, the radiation may, in.
Helical antenna helix antenna bhavin v kakani itnu introduction. This mode of operation is referred to as the normal mode. Helical antennas can be designed to operate in normal or axial modes. A simplified model for normal mode helical antennas. Pdf design and fabrication of an axial mode helical antenna. The helical antenna has many possible modes of radiation as discussed by kraus 1. The parameters of the helix antenna are defined below. Helical antennas can operate in one of two principal modes. Design and fabrication of an axial mode helical antenna. Design and fabrication of wide dualband normal mode helical antenna fatemeh gerangharakhili shahid rajaee teacher training, tehran, iran in this paper, a wide dualband nonuniform normal i. The basics of quadrifilar helix antennas orban microwave. In normal mode the antenna will behave as a monopole antenna. Unfortunately the method of operation and the results obtainable for this type of antenna have been much misunderstood by amateurs and professionals alike. Us5892480a variable pitch angle, axial mode helical antenna.
Normal mode helical normal mode helical uhf tv broadcasting antenna 1954. How to build a helical antenna consumer electronics other. The general polarization of the antenna is elliptical. Folded helical antenna is high efficiency antenna, compared by original type, and the sensitive near the resonant frequency in the 900mhz band. The input impedance of the helical antenna is dependent on the pitch angle and the size of the conducting wire. The most popular helical antenna often called a helix is a travelling wave antenna in the shape of a corkscrew that produces radiation along the axis of the helix. This mode of radiation, called the axial or beam mode, is generated in practice with great ease, and may be dominant over a wide frequency range with desirable pattern, impedance, and polarization characteristics. Considering the tape is narrow, construction and performance analysis of helical antenna operating at 5. The possibility of a normal mode of radiation, as suggested bywheeler,7 is also included as aspecial case. Helical antenna wikimili, the best wikipedia reader. It is the purposeof this paperto discuss the helical antenna from this general point of view including the axial or beam mode of radiation as a particular case. Criteria a helical antenna operating in normal mode is encountered when the diameter or by association the circumference of. Typical helix dimensions for an axialmode helical antenna have a helix circumference of one wavelength at the center frequency, with a helix pitch of 12 to 14 degrees. Normal mode helical antenna, which originally was optimized to provide the minimum voltage standing wave ratio vswr response across band ii 87.
Previously, the small nmha was studied for rfid system at 900 mhz. Introduction normal mode helical antenna nmha is a proper choice of military handsets and recreational. The radiation pattern of this helical antenna is a combination of short dipole and loop antenna. Here, a normal mode helical antenna nmha is considered as a promising candidate by taking into account the circumstances surrounded by metallic objects. Therefore, the axialmode helical antenna is desired for uav applications because of its high. This mode of radiation is obtained if the dimensions of helix are small compared to the wavelength.
The benefits of this antenna is it has a wide bandwidth, is easily. Important properties of normalmode and axialmode helixes are summarized below. In normal mode of radiation, the radiation field is normal to the helix axis. These helixes are referred to as axial mode helical antennas. What is the advantage of using a helical antenna over a. Numerical analysis of normal mode helical dipole antennas. Doubly helical antenna by spiro mode maintaining radiation. These helix antennas are referred to as axialmode helical antennas. Because of its broad bandwidth and circular polarization. In the normal mode the dimensions of the helix are small compared to the wavelength and the antenna acts as an omnidirectional monopole while in the axial mode the dimensions of the helix are comparable to a wavelength and the antenna operates directional. Helical antennas john kraus, w8jk, is the originator. Two 2 types of helical antennas have been designed. The most popular helical antenna helix is a travelling wave antenna in the shape of a corkscrew that produces radiation along the axis of the helix antenna. C circumference of a turn on the helix antenna cpid.
Design, construction and performance analysis of helical. A helical antenna is, as its name implies, an antenna made of a wire wound in a helix. Pdf design of normal mode helical antenna using neural. This paper presents a novel mode and frequency reconfigurable origami quadrifilar helical antenna that can operate in. This paper presented a study of a defected ground structure dgs which affects the performances of the normal mode helical antenna. Jun 29, 2016 i will assume that you are asking about axial mode aerials, which operate with waves travelling along the axis of the helix. The tape helix configuration and the developed helix. In this mode the helix is a broadband antenna, with. Generally, the helical antenna is a combination of a linear antenna and a loop antenna which has two radiating modes.
It is basic vhf and uhf antenna which provides circular polarization. The basic geometry of the helix antenna is shown in fig 1. These helix antennas are referred to as axial mode helical antennas. The nmmhas size allows it to be a build in block of a deck commercial receiver. Helical antenna the most popular helical antenna often called a helix is a travelling wave antenna in the shape of a corkscrew that produces radiation along the axis of the helix. If the antennas dimensions are small compared to the wavelength of the signal the antenna will operate in normal mode.
Given generalized requirements for a medium gain circularly polarized cp antenna we design and fabricate an axial mode helical antenna. In addition to circular polarization, this mode is found. One limitation is that the usefulness of the circular polarization is limited since it cannot be easily reversed to the other sense, lefthanded to righthanded or viceversa. The helical antenna is a hybrid of two simple radiating elements, the dipole and loop antennas. A very compact normal mode multiloop helical antenna with. When the helix antenna diameter is much smaller than. Helical antenna free download as powerpoint presentation. Considering the tape is narrow, antenna axis of symmetry and applying the boundary. Optimization of the exchange of energy between a free space wave and current flowing in the conductive helix of an axial mode, helical antenna is achieved by varying the pitch angle of successive turns of the antenna along the axis of the antenna, from a relatively small pitch angle at the base, feed location of the antenna, to a relatively large value at the distal end of the antenna. Consist of a thick cooper wiretube wound in the form of a screw thread forming a helix. The axial mode occurs when the circumference of the helix is on the order of one wavelength and is characterized by radiation along the axis of the helix. The helical antenna has a long history and has been the object of much study and development over the last half century since its invention in 1946 kraus, 1976.
If the circumference of the helix is significantly less than a wavelength and its pitch axial distance between successive turns is significantly less than a quarter wavelength, the antenna is called a normal mode helix. Development of a very small normal mode helical antenna for. The most popular travelling wave antenna is a helical antenna helix that produces radiation along the axis of the helix in axialmode and normal mode. The most popular travelling an approximate directivity expression is given as wave antenna is a helical antenna helix. These aerials are usually used where the polarisation of the wave is circular, or linear but either unknown or varying. If the circumference of the helix is significantly less than a wavelength and its pitch axial distance between successive turns is significantly less than a quarter wavelength, the antenna is called a normalmode helix.
The wireandloop model suggests that the axial ratio of the normal mode helical antenna can be expressed as 2 2 2 2 e s s ar e r c. The presentation includes the design parameter, field equation and radiation pattern associated with different modes of the helical antenna. It is also an ideal feed for a small offset dish if used in satellite applications. The most popular travelling wave antenna is a helical antenna helix that produces radiation along the axis of the helix in axial mode and normal mode. In a normalmode helix, radiation is maximum perpendicular to its axis, while the axialmode helix provides a main beam along the axis. The benefits of this helix antenna is it has a wide bandwidth, is easily constructed, has a real input impedance, and. Pdf design of normal mode helical antenna using neural networks. The charge distribution associated with the t 1 mode can be seen in figure 2b. A helical antenna is a specialized antenna that is considered as a hybrid of the radiating elements loop antennas and the dipole.
Us5892480a variable pitch angle, axial mode helical. Best of all, it is impressively small in size and low in profile. I will assume that you are asking about axial mode aerials, which operate with waves travelling along the axis of the helix. The polarization sense now corresponds to the winding sense of the helices. In normal mode the antenna will behave as a monopole antenna radiating roughly in a plane around the antenna.
A novel mode and frequency reconfigurable origami quadrifilar. The radiation pattern of the normal mode helical antenna is omnidirectional and generally similar to the pattern of a short dipole antenna. Helical antennas can operate in two principal modes. Much has been said for and against what is termed the normalmode helix as used on handheld transceivers. Normalmode helical normalmode helical uhf tv broadcasting antenna 1954. Helical antenna helix antenna bhavin v kakani itnu introduction it is basic broadband vhf and uhf antenna which provides circular polarization. In a helical antenna, the conducting wire is wound in the form of a helix. The helical antenna is a hybrid of two simple radiating elements, the dipole and loop antenna. In the axial radiation mode, the radiation is in the axial direction, while its radiation is perpendicular to the axis in the normal radiation mode. The major drawback which has been overcome with this design is the very narrow bandwidth of the normal mode helical antenna, which originally was optimized to provide the min. Efficiency improvements of normal mode helical antennas by folded configurations woong hyun jung, naobumi michishita and yoshihide yamada department of electrical and electronic engineering, national defense academy 11020 hashirimizu, yokosuka, 2398686 japan email. When the helix is limited in length, it radiates and can be used as an antenna.
These are generally used as the radiator of helical antenna. These helixes are referred to as axialmode helical antennas. Optimization of the exchange of energy between a free space wave and current flowing in the conductive helix of an axial mode, helical antenna is achieved by varying the pitch angle of successive turns of the antenna along the axis of the antenna, from a relatively small pitch angle at the base, feed location of the antenna, to a relatively large value at the distal end of the. Counter clockwise phasing backward helix mode backfire radiation clockwise phasing forward helix mode endfire radiation figure 2. The helical antenna operates in basically two modes. Keywords normal mode multiloop helical antenna, radio services, impedance, bandwidth, gain 1. Consist of a thick cooper wire wound in the form of a screw thread forming a helix. The selfresonant structure enables normal mode helical antennas to have radiation. Design and fabrication of wide dualband normal mode. In the normal mode or broadside helical antenna, the diameter and the pitch of the aerial are small compared with the wavelength.
289 574 1170 1546 1338 1576 173 1390 1004 395 1451 1543 1 1579 955 740 189 640 591 741 780 263 950 76 1189 1014 287 1311 1420 894 876