Broadband Antennas

Broadband antennas

Introduction

When talking about antennas we can find a wide variety of them, which are characterized by the frequency they handle, the direction in which they are radiating. This report will be treated more in the background on broadband antennas, which you have a story that would be interesting to treat and express. 

When our physics teachers told us about the importance of this subject and as telecommunications engineers we considered that it was not so important at the time of graduating or working, but we are omitting that much of this subject contributed to many of the studies or theories,It will not be spoken to the molten of physics or some other matter seen at the university.

It should be noted that in 1941 Stratton and Chu raised the spheroidal or spheroidal antenna, this study was carried out based on a simple solution of Maxwell’s equations, we can say that the base structure handled by broadband antennas is due in large partIn the investigation they carried out. However, the decomposition of these spheroidal antennas cannot be used for usual antennas arbitrarily. In 1943, Schelkunoff raised the Biconical or Biconica antenna, this can also be easily expressed with Maxwell’s equations, this study allowed it to be applied to the antennas in general.

Developing

In 1947 an idea of broadband antenna was determined by the Harvard University Research Laboratory. The concept that is given was based on the transmission line that while moving away while the relationship of the internal and external driver is firm.

In 1950 the spiral antenna was added within the class of autonomous frequency antennas. The triangular spiral antenna and the Archimedes antenna are two of the best known spiral antennas.

In 1982 r.H. Dujamel Develop the Sinusoidal Antenna, which was why it gave double linear polarization and a large bandwidth in a narrow volume and below cost. This antenna had a more complex geometry than the spiral antenna had. This antenna offered double linear and orthogonal polarization so that different polarizations or for dual handling antennas were used. Another peculiarity is that the two pairs of exit of the arms can be together to perform simultaneously LHCP and RHCP.

In 1992 the monopolo disc antennas were invented. These antennas since they were invented were made with the purpose of producing a large bandwidth with a simple configuration. Circular, elliptical or trapezoidal: The radiant elements are mounted in the orthogonal form to the mass plane and its diet is given by a coaxial cable, these monopolo antennas its greatest and most interesting application is in ultra bandwidth UWB.

In 1999 the four squares antenna was designed by Virginia Tech Antenna Group Vtag, the previous aforementioned antennas handle a large bandwidth, compared to this antenna that does not have much bandwidth, but has very interesting characteristics that make it really uniqueAs is the unidirectional pattern, dual polarization, compact geometry. Compact geometry is one of its desirable peculiarities for an array of phase and sweeping bandwidth.

This characteristic of the sweeping of the array is determined by the distance of the elements, so the limitation consists of the size of these same. For broadband antennas its operation band is very extensive, making the electrical distance between the measurement elements that add and increase the frequencies larger. 

Perfectly a lower distance from λ/2 is enviable about the frequency band. When the volume of the element is extensive, the space simply exceeds the distance λ/2 at very high frequencies, degrading the peculiarity of the array sweep. For this reason, for the reduced size of the four -square -square antenna, it is very convenient for broadband array antennas

The dipole is also a resonant structure, the preferred or most used is resonant λ/2. If you require, or want to increase the bandwidth you must make the radius of your thickest buckets. If this noticed that the central resonance frequency moves towards slightly lower values. With this, a reduced rectification is presumed in the resonant length of or the dipoles.

When talking about the impedance of a dipole taking into account its λ/2 radio resonance too much and possibly infinitely so thin would be 73+J42 OHM. To eliminate that imaginary part of that impedance, what is done is to place the length a little worthy. Spheroidal antenna: As we mentioned earlier, Stratton and Chu in 1941 presented solutions that not only served for spheroidal antennas, also those solutions served for elongated spheroidal antennas.

Figure 1 demonstrates the evolution that is had from a sphere dipole to a thin dipole of fine thread. Axial symmetry is accepted, and the excitation tension is adapted by means of a GAP in the center. For a spherical driver there is no place where the input reactance is zero;There will always be a capacitive component. It should be noted that it is evident that the largest antennas make the impedance curve wider and for this reason it will offer greater bandwidth.

Stratton and Chu determined that the peculiarities of the spheroidal antenna are very similar in nature, but very different in magnitude respecting the consequence or results of the sphere. Stratton and Chu found that great eccentricity great relationship length-diameter originates solid resonances in contrast to the extensive resonance of the sphere.

conclusion

Remember when we mention that the zero reactance happened when the antenna length is slightly less than λ/2 for long and fine threads with respect to 0.49 λ or for 98% of the antenna length. However, for the wider threads that zero reactance could occur at the time when the antenna length was larger than λ/2. 

Biconical or Biconica Antena: For this antenna we can leave as a concept the basis that a thicker cable offers us greater impedance bandwidth than the one offered by a Dipolo de Cine. Disconous Antenna: Kandoian in 1945 implemented a variation of the finite biking antenna, called Antena Discono, in which a land plane that has a disc form is used in many types of applications. Bow-tie or bowten antenna: This antenna is a flat version that was developed based on the infinite biconic antenna. The Bow-Tie.