Fractal television antenna with your own hands. As an aluminum wire or cable make your own hands an antenna for a TV: a simple design for receiving TV signal. With increasing dimension, the total length of the broken line is alineternally increasing,

The first thing I would like to write is a slight introduction to history, theory and use of fractal antennas. Fractal antennas were open recently. Their first invented Nathan Cohen in 1988, then he published his research how to make an antenna for a TV TV and patented in 1995.

Fractal antenna has several unique characteristics, as written in Wikipedia:

"Fractal antenna is an antenna that uses a fractal, self-reserving design to maximize the length or increase the perimeter (in the internal sections or external structure) of a material that can receive or transmit electromagnetic signals within this total surface area or volume."

What exactly does this mean? Well, you need to know what a fractal is. Also from Wikipedia:

"Fractal, as a rule, is a coarse or fragmented geometric shape, which can be divided into parts, each of the parts will be a copy of the whole reduced size - this property called self-similarity."

Thus, the fractal is a geometric shape that repeats itself again and again, regardless of the size of the individual parts.

It was found that fractal antennas are about 20% more efficient than conventional antennas. It can be useful, especially if you want your TV antenna to take digital video or high-definition video, increased the cellular range, wi-Fi range, Receiving radio FM or AM, etc.

In most cell phones, fractal antennas are already standing. You could notice it because cell phones no longer have antennas outside. This is because inside them are fractal antennas, etched on the circuit board, which allows them to better receive a signal and take more frequencies such as Bluetooth, cellular and Wi-Fi from one antenna.

Wikipedia:

"The fractal antenna response is noticeably different from traditional antenna designs by the fact that it is capable of working with good performance at different frequencies at the same time. The frequency of standard antennas must be cut to be able to take only this frequency. Therefore, the fractal antenna, in contrast to the usual, is an excellent design for broadband and multidia-band applications. "

The trick is to design your fractal antenna to resonate on a certain, central frequency you need. This means that the antenna will look different depending on what you want to get. To do this, apply mathematics (or online calculator).

In my example, I'm going to do simple antennaBut you can make more complicated. The harder, the better. I will use the coil from the 18-core wire with a solid core to make an antenna, but you can finalize your own mounting fees in accordance with your aesthetic considerations, make it less or more complex with large resolution and resonance.

I'm going to make TV antenna for receiving digital TV or high-resolution TV. It is easier to work with these frequencies, they are located in the length range from about 15 cm to 150 cm for half the wavelength. For the simplicity and cheapness of details, I'm going to arrange it on a common dipole antenna, it will catch the wave of a range of 136-174 MHz (VHF).

You can add director or reflector to receive the waves of UHF (400-512 MHz), but the reception will be more dependent on the direction of the antenna. VHF also depends on the direction, but instead of directly pointing to the TV station in the event of a UHF installation, you will need to install VHF ears perpendicular to TV stations. Here you will need to make a little more effort. I want to make the most simple design, because it is also a rather complicated thing.

Main components:

• Mounting surface, such as a plastic case (20 cm x 15 cm x 8 cm)
• 6 screws. I used steel screws for sheet metal
• Transformer resistance from 300 ohms to 75 ohms.
• Mounting wire cross section 18 AWG (0.8 mm)
• RG-6 cable coaxial with terminators (and with rubber shell, if the installation will be on the street)
• Aluminum when using the reflector. In the embedding above was such.
• Thin marker
• Two pairs of small pliers
• The line is not shorter than 20 cm.
• Angle measurement conveyor
• Two drills, one slightly smaller diameter than your screws
• Little Cutter for Wire
• Screwdriver or screwdriver

Note: The lower part of the aluminum wire antenna is on the right on the image where the transformer sticks out.

Step 1: Adding a reflector

Collect the case with a reflector under a plastic cover

Step 2: Drilling holes and installation of fastening points

Drill small holes for removal on the opposite side of the reflector in these positions and place the conductive screw.

Step 3: Squeeze, cut and talk wires

Cut four 20-centimeter pieces of wire and place on the housing.

Step 4: Wire Measurement and Marking

Using the marker, mark every 2.5 cm on the wire (in these places there will be bends)

Step 5: Creating Fractals

This step needs to be repeated for each piece of wire. Each bend should be equal to exactly 60 degrees, as we will do equilateral triangles for fractal. I used two pairs of pliers and transport. Each bending is made on the label. Before making bend, visualize the direction of each of them. Use the attached diagram for this.

Step 6: Creating dipoles

Cut more two pieces of wire with a length of at least 15 cm. Wrap these wires around the upper and lower screws going along the long side, and then wrap to the central one. Then cut extra long.

Step 7: Installation of dipoles and installation of the transformer

Secure each of the fractals on the angular screws.

Attach the transformer of the appropriate impedance to two central screws and tighten them.

The assembly is finished! Check and enjoy!

Step 8: more iterations / experiments

I made some new items using a paper template from GIMP. I used a small solid telephone wire. It turned out to be quite small, durable and militant to bend into complex forms that are required for the central frequency (554 MHz). This is the average value of the Digital UHF signal for channels essential television in my area.

Photo attached. Maybe it will be difficult to see the copper wires with weak lighting on the background of cardboard and with a ribbon over, but the idea of \u200b\u200byou is already understandable.

With this size, the elements are rather fragile, so they need to be processed neatly.

I also added a pattern in PNG format. To print the desired size, you need to open it in the photo editor, for example in GIMP. The template is not ideal, because I made it manually with the mouse, but it is convenient enough for human hands.

In mathematics, fractal are called the sets consisting of elements similar to the set as a whole. The best example: if you look close-close the line of the ellipse, it will become straight. Fractal - how much do not mind - the picture will still be difficult and similar to a general view. Elements are bizarre. Consequently, the simplest example of fractal we consider concentric circles. How much do not mind, new circles appear. Examples of fractals set. For example, in Wikipedia, a drawing of cabbage romanesco is given, where the Kochan consists of cones, exactly resembling a drawn kochan. Now readers understand that it is not easy to make fractal antennas. But interesting.

Why are fractal antennas

The appointment of fractal antenna is to catch more smaller victims. In Western video - it is possible to find a paraboloid where the emitter will serve a segment of the fractal tape. There are already made from foil elements of microwave devices, more efficient than ordinary. We will show how to make a fractal antenna to the end, but by agreement are engaged in alone with the METER. We mention that there is a whole site, of course, the overseas, where promoted the corresponding product, there is no drawings. Our homemade fractal antenna is easier, the main dignity - the design will be able to make with your own hands.

The first fractal antennas - biconic - appeared if you believe the video from Fractenna.com, in 1897 by Oliver Lodge. Do not look for Wikipedia. In comparison with the usual dipole, a pair of triangles instead of a vibrator gives an expansion of a strip by 20%. Creating periodic repeating structures, managed to collect miniature antennas not worse than large fellow. Often meet the biconic antenna in the form of two frames or bizarre plates.

Ultimately, this will allow you to take more television channels.

If you type a request for YouTube, a video for the manufacture of fractal antennas appears. It will be better to understand how it is arranged, if you present the six-pointed star of the Israeli flag, in which the angle cut off with the shoulders. It turned out, three corners were left, two one side in place, the second is not. The sixth corner is absent at all. Now we have two similar stars with vertically, central corners to each other, slots left and right, above them - a similar pair. Opened antenna grid. - the simplest fractal antenna.

Stars for corners are connected by the feeder. Parly columns. The signal from the line is removed, exactly in the middle of each wire. The design is assembled on the bolts on the dielectric (plastic) substrate of the appropriate size. The side of the star is exactly inch, the distance between the corners of the stars vertically (the length of the feeder) is four inches, horizontally (the distance between two feeder wires) is inch. Stars have 60 degrees at the tops, now the reader will draw a similar pattern in the form of a template to make a fractal antenna independently. Made a working sketch, the scale is not respected. Do not handle that the stars came out exactly, Microsoft Paint without great opportunities For the manufacture of accurate drawings. Enough to look at the picture so that the fractal antenna device becomes obvious:

1. A brown rectangle is a dielectric substrate. The fractal antenna is shown in the figure has a symmetrical orientation diagram. If you protect the emitter from the interference, the screen is placed on four racks behind the substrate at a distance of inches. At frequencies there is no need to place a solid sheet of metal, there is enough mesh with a third-inch face, do not forget to connect the screen with the cable braid.
2. The feeder with a wave resistance of 75 ohms requires coordination. Find either to make a transformer that converts 300 ohms to 75 ohms. It is better to store the KSV meter and select the desired parameters not to the touch, but by the device.
3. Four stars, wound from copper wire. Varnishing isolation in the place of docking with the feeder will be cleaned (if any). The internal feeder of the antenna consists of two parallel pieces of wire. The antenna is not bad to place in the box to protect against bad weather.

We collect a fractal antenna for digital television

After reading to the end, the fractal antennas will do any. So quickly deepened in the design that they forgot to tell about polarization. We assume it is linear and horizontal. This schemes for reasons:

• Video, obviously, American origin, talking about HDTV. Therefore, we can take the fashion of the specified country.
• As you know, on the planet, few states are broadcast from satellites using circular polarization, among them of the Russian Federation and the United States. Consequently, we believe, other information transfer technologies similar. Why? There was a cold war, we believe, both countries chose strategically and how to transfer, other countries proceed from purely practical considerations. Circular polarization is embedded specifically for spy satellites (moving constantly relative to the observer). Hence the grounds to believe that in television and in broadcasting there is similarity.
• The structure of the antenna says that linear. Here it is simply nowhere to take circular or elliptical polarization. Consequently - if only among our readers there are no professionals who own MMANA - if the antenna does not catch in the accepted position, turn 90 degrees in the plane of the emitter. Polarization will change to the vertical. By the way, many will be able to catch and FM, if the dimensions set more than once in 4. Better wire takes it harder (for example, 10 mm).

We hope to explain the readers how to use the fractal antenna. A pair of advice on a simple assembly. So, try to find a wire with lacquered protection. Bend the shapes, as shown in the picture. Then the designers diverge, we recommend doing this:

1. Slide the stars and feeder wires in the docking grounds. Wire feeder for the ears strengthen the bolts on the substrate in the middle parts. To perform the action correctly, measure inch in advance and spend two parallel lines with a pencil. Along them should lie the wire.
2. Sold down a single design, carefully extinguishing the distances. The authors of the video are recommended to make the emitter so that the stars in the corners are smoothly lying on the feeders, and the opposite ends rest on the edge of the substrate (each in two places). For an exemplary star marked places in blue.
3. To perform a condition, each star is attracted in one place a bolt with a dielectric chomant (for example, from the Cambrid wire PVA and the like). The picture of the fasteners is shown in red for one star. The bolt is schematically drawn by a circle.

The feed cable passes (optional) with back side. Drill hole holes. Setting up KSW It is conducted by changing the distance between the feeder wires, but in this design it is a sadistic method. We recommend simply measure the wave resistance of the antenna. Recall how this is done. It will take a generator to the frequency of the program being viewed, for example, 500 MHz, an additional high-frequency voltmeter that does not save before the signal.

Then the voltage issued by the generator is measured, for which it closes to the voltmeter (parallel). From variable resistance with extremely smaller self-inductance and antenna, we collect a resistive divider (connect consistently after the generator, first resistance, then the antenna). The voltmeter measure the voltage of the variable resistor, simultaneously adjusting the nominal value until the generator readings without load (see above) will not be twice the current. It means that the value of the variable resistor became equal to the wave resistance of the antenna at a frequency of 500 MHz.

Now it is possible to make a transformer in the right way. It is difficult to find the right thing in the network, for lovers to catch the broadcasting found a ready-made answer http://www.cqham.ru/tr.htm. The site is written and drawn how to coordinate the load with a 50-ohm cable. Note, the frequencies correspond to the KV range, SV fit here partially. The wave resistance of the antenna is maintained in the range of 50 - 200 Ohm. How much will the star give, it's hard to say. If there is a device for measuring the wave resistance of the line, recall: if the length of the feeder is more than a quarter of the wavelength, the antenna resistance is transmitted to the output unchanged. For a small and large range, such conditions cannot be ensured (we will remind that the extended range is also included in the features of fractal antennas), but for measurement targets, the mentioned fact is used everywhere.

Now readers know all about these amazing transceiver devices. Such an unusual form suggests that the diversity of the universe does not fit into the typical framework.

UDC 621.396

fractal ultra-wideband antenna based on a circular monopoly

G. I. Abdrakhmanova

Ufa State Aviation Technical University,

Universita Degli Studi Di Trento

Annotation. The article considers the task of designing an ultra-wideband antenna based on fractal technology. The results of studies of change of radiation characteristics are presented depending on the magnitude of the scale coefficientand iteration level. Parametric optimization of the antenna geometry for compliance with the requirements of the reflection coefficient is carried out. The dimensions of the developed antenna are 34 × 28 mm 2, and the operating frequency range is 3.09 ÷ 15 GHz.

Keywords: Ultra-wideband radio communications, fractal technology, antennas, reflection coefficient.

ABSTRACT:The Development Of A New Ultra-Wideband Antenna On The Basis of Fractal Technology is Described in The Paper. The Research Results on Radiation Characteristics Changes Depending On The Value of Scale Factor and Iteration Level Are Presented. The Parametric Optimization of the Antenna Geometry for Satisfying The Reflection Coefficient Requirements Was Applied. The Developed Antenna Size IS 28 × 34 mm 2, And The Bandwidth - 3.09 ÷ 15 GHz.

Key Words: Ultra-Wideband Radio Communication, Fractal Technology, Antennas, Reflection Coefficient.

1. Introduction

To date, ultra-wideband (SSR) communication system are of great interest to developers and manufacturers of telecommunications equipment, since it allows you to transfer huge data streams at high speed in the ultra-wide frequency band on a non-limzen-based basis. Features of the transmitted signals involve the absence of powerful amplifiers and complex components of signal processing in the composition of receiving-transmitting complexes, but limit the range (5-10 m).

The absence of an appropriate element base that can effectively work with supercount pulses, restrains the mass introduction of UCP technology.

Receiving-transmitting antennas are one of the key elements that affect the quality of the transmission / reception of signals. The main direction of patents and research in the design of the design of antenna technology for SSP devices is miniaturization and reduced production costs when ensuring the required frequency and energy characteristics, as well as in the application of new forms and structures.

So, the antenna geometry is built on the basis of a spline with a rectangular P-shaped slot in the center, which allows the strip to operate in the STS with the barrier functionWLAN -Diapazone, the size of the antenna is 45.6 × 29 mm 2. Asymmetric E-shaped figure with a size of 28 × 10 mm 2, located at an altitude of 7 mm relative to the conductive plane (50 × 50 mm 2) is selected as the emitting element in. A planar monopoly antenna (22 × 22 mm 2), designed on the basis of a rectangular emitting element and a staircase resonant structure on the back side, is represented.

2 Problem Statement

Due to the fact that circular structures can provide a fairly wide bandwidth, simplifying the design, small sizes and cost reduction in production, in this paper it is proposed to develop a Circular monopoly antenna. Required operating frequency range - 3.1 ÷ 10.6 GHz in level -10 dB reflection coefficientS 11, (Fig. 1).

Fig. 1. Required Mask for Reflection CoefficientS 11.

In order to miniaturization, the antenna geometry will be upgraded by applying fractal technology, which will also allow to investigate the dependence of radiation characteristics from the value of the scale of the scale δ and the level of fractal iteration.

Next, the task of optimizing the developed fractal antenna is set to expand the working range by changing the following parameters: the length of the central conductor (CP) of the compartment waveguide (kV), the length of the land plane (PZ) kV, the distance "PZ KV - emitting element (IE)".

Modeling antenna and numerical experiments are carried out in the environment "CST Microwave Studio.

3 Selection of antenna geometry

A circular monopol is selected as the base element, the dimensions of which are a quarter of the wavelength of the required range:

where L A. - the length of the emitting antenna element excluding the CPU;f L. - lower boundary frequency,f L. = f. Min UWB. \u003d 3.1 · 10 9 Hz; from- light speed, from = 3 · 10 8 m / s 2.

Receive L A. \u003d 24.19 mm ≈ 24 mm. Considering that the circle of radius is chosen as IEr. = L A. / 2 \u003d 12 mm, and taking the initial length of the CPUL F.also equal r., we obtain zero iteration (Fig. 2).

Fig. 2. Zero iteration antenna

Dielectric substrate thicknessT S. and with parameter valuesε S. \u003d 3.38, TG δ \u003d 0.0025 is used as a base on the front side of which are locatedIE, CPU and PZ . At the same time, the distance "PZ-CPU " Z V. and "PZ-IE" Z H. Adopted equal to 0.76 mm. The values \u200b\u200bof the remaining parameters used in the simulation process are presented in Table 1.

Table 1. Antenna parameters ( δ = 2)

Name	Description	Formula	Value
L A.	Antenna length	2 ∙ r. + L F.	36 mm
W A.	Antenna width	2 ∙ r.	24 mm
L F.	CPU length	r +.0,1	12.1 mm
W F.	Width CPU		1.66 mm
L G.	PZ length	r - T S	11.24 mm
L S.	Length of the substrate	L A. + G S.	37 mm
W S.	Width of the substrate	W A.+ 2 ∙ G S.	26 mm
G s 1	Vertical substrate clearance		1 mm
G s 2.	Horizontal substrate gap		1 mm
T M.	Metal thickness		0.035 mm
T S.	Substrate thickness		0.76 mm
r.	Radius of Circle 0 Oh Iteration		12 mm
r. 1	Radius of the circle of the 1st iteration	r. /2	6 mm
r. 2	Circle Radio 2 Oh Iteration	r. 1 /2	3 mm
r. 3	Radius of circle 3 iterations	r. 2 /2	1.5 mm
ε S.	The dielectric constant		3,38

Antenna is powered by a companary waveguide consisting of a central conductor and plane of the Earth,SMA - Connector and a perpendicular compartment waveguide port perpendicular to it (Fig. 3).

where ε EFF. - Effective dielectric constant:

K. – full elliptical integral of the first kind;

	(5)

Fractality When constructing an antenna lies in a special way of packaging elements: subsequent iterations of the antennas are formed by placing the circles of a smaller radius in the elements of the previous iteration. In this case, the coefficient of scale δ determines how many times the sizes of neighboring iterations will differ. This process For case δ = 2 is shown in Fig. four.

Fig. 4. The first, second and third iterations of the antenna ( δ = 2)

So, the first iteration is obtained by subtracting two circles with a radiusr. 1 From the source element. The second iteration is formed by placing a decreased twice metal circles with a radiusr. 2 In each circle of the first iteration. The third iteration is similar to the first, but the radius isr. 3 . The paper discusses the vertical and horizontal location of the circles.

3.1 Horizontal location of elements

The dynamics of changes in the reflection coefficient depending on the level of iteration is presented in Fig. 5 for δ \u003d 2 and in fig. 6 for δ \u003d 3. Each new order corresponds to one additional resonant frequency. Thus, the zero iteration in the considered range of 0 ÷ 15 GHz corresponds to 4 resonance, the first iteration - 5, etc., while starting from the second iteration, changes in behavior of characteristics become less noticeable.

Fig. 5. The dependence of the reflection coefficient on the procedure of iteration ( δ = 2)

The essence of modeling is that at each stage, the one that is determined as the most promising is selected from the characteristics under consideration. In this regard, the rule was introduced:

If exceeding (difference) in the range, where the shelves are above -10 dB, it is small, then you should select the characteristic that is below the shelves in the operating range (below -10 dB), since as a result of optimization, the first will be eliminated, and the second omitted even lower.

Fig. 6. The dependence of the reflection coefficient on the iteration procedure ( δ = 3)

Based on the data obtained and in accordance with this rule for δ \u003d 2 The curve corresponding to the first iteration is selected for δ \u003d 3 - second iteration.

Next, it is proposed to investigate the dependence of the reflection coefficient on the value of the scale of the scale. Consider a change δ in the range of 2 ÷ 6 in increments 1 within the first and second iterations (Fig. 7, 8).

Interesting charts are that, starting with δ \u003d 3, characteristics become stronger and smooth, the number of resonances remains constant, and growth δ accompanied by increasing levelS 11. In even ranges and decline in odd.

Fig. 7. The dependence of the reflection coefficient of the scale for the first iteration ( δ = 2; 3; 4; 5; 6)

In this case, the value is selected for both iterations. δ = 6.

Fig. 8. Dependence of the reflection coefficient of the scale of the scale for the second iteration ( δ = 2; 3; 4; 5; 6)

δ \u003d 6, since it is characterized by the lowest shelves and deep resonances (Fig. 9).

Fig. 9. Comparison S 11

3.2 Vertical location of elements

The dynamics of changes in the reflection coefficient depending on the level of iteration for the case of the vertical location of the circles is presented in Fig. 10 for δ \u003d 2 and in fig. 11 for δ = 3.

Fig. 10. The dependence of the reflection coefficient on the iteration procedure ( δ = 2)

Based on the data obtained and in accordance with the Rule for δ \u003d 2 I. δ \u003d 3 The curve corresponding to the third iteration is selected.

Fig. 11. The dependence of the reflection coefficient on the iteration procedure ( δ = 3)

Consideration of the dependence of the reflection coefficient on the value of the scale of the scale within the first and second iterations (Fig. 12, 13) reveals the optimal value δ \u003d 6, as in the case of a horizontal location.

Fig. 12. Dependence of the reflection coefficient on the coefficient of scale for the first iteration ( δ = 2; 3; 4; 5; 6)

In this case, the value for both iterations is selected. δ \u003d 6, which also representsn.-start fractal, and therefore it may have to combine the features δ = 2 I. δ = 3.

Fig. 13. The dependence of the reflection coefficient on the scale of the scale for the second iteration ( δ = 2; 3; 4; 5; 6)

Thus, from four compared options, a curve corresponding to the second iteration is selected, δ \u003d 6, as in the previous case (Fig. 14).

Fig. 14. ComparisonS 11. For the four the antenna geometry under consideration

3.3 Comparison

Considering best options Vertical and horizontal geometries obtained in the two previous subsections, the choice stops on the first (Fig. 15), although in this case the difference between these options is not so large. Operating frequency ranges: 3.825 ÷ 4.242 GHz and 6.969 ÷ 13.2 GHz. Next, the design will be upgraded with the aim of developing an antenna operating in the entire SSP range.

Fig. 15. ComparisonS 11. to select the outcome option

4 Optimization

This section discusses the antenna optimization based on the second iteration of the fractal with the value of the coefficient δ \u003d 6. Variable parameters are presented on, and the ranges of their changes are in Table 2.

Fig. twenty. Appearance Antennas: a) facial side; b) back

In fig. 20 shows the characteristics reflecting the dynamics of changeS 11. For steps and proving the validity of each subsequent action. Table 4 shows the resonance and boundary frequencies used below to calculate surface currents and orientation diagrams.

Table 3. Calculated antenna parameters

Name	Source value, mm	Final value, mm
∆ L F.
Z H.	Table 13,133208
6,195	27,910472
8,85	21,613615
10,6	12,503542
12,87	47,745235

The distribution of the surface currents of the antenna on the resonant and boundary frequencies of the SSR range is represented in Fig. 21, and pattern diagrams - in fig. 22.

a) 3.09 GHz b) 3.6 GHz

c) 6,195 GHz d) 8.85 GHz

e) 10.6 GHz e) 12.87 GHz

Fig. 21. Distribution of surface currents

but) F.(φ ), θ \u003d 0 ° b) F.(φ ), θ \u003d 90 °

in) F.(θ ), φ \u003d 0 ° D) F.(θ ), φ \u003d 90 °

Fig. 22. Food diagrams in the polar coordinate system

5 Conclusion

This paper presents a new method of designing a UCP antennas based on the use of fractal technology. This process implies two stages. Initially, the geometry of the antenna is determined by selecting the appropriate scale coefficient and the level iteration of the fractal. Further, parametric optimization is applied to the form of studying the effect of the size of the key components of the antenna on the radiation characteristics.

It has been established that with an increase in the order of iteration, the amount of resonant frequencies increases, and increasing the coefficient of scale within one iteration is characterized by more severe behaviorS 11. and constancy of resonances (starting with δ = 3).

The developed antenna provides high-quality reception of signals in the frequency band 3.09 ÷ 15 GHz in terms of levelS 11. < -10 дБ. Помимо этого антенна характеризуется малыми размерами 34×28 мм 2 , а следовательно может быть успешно применена в СШП приложениях.

6 Thanks

The study was supported by a grant of the European Union "Erasmus Mundus Action. 2 ", also A. G. I. Thanks ProfessorPaolo Rocca. For a useful discussion.

Literature

1. L. . Lizzi, G. Oliveri, P. Rocca, A. Massa. Planar Monopole UWB Antenna with UNII1 / UNII2 WLAN-BAND NOTCHED CHARACTERISTICS. PROGRESS IN ELECTROMAGNETICS RESEARCH B, VOL. 25, 2010. - 277-292 pp.

2. H. Malekpoor, S. JAM. Ultra-Wideband Shorted Patch Antennas Fed by Folded-Patch with Multi Resonances. Progress In Electromagnetics Research B, Vol. 44, 2012. - 309-326 PP.

3. R.A. Sadeghzaden-Sheikhan, M. Naser-Moghadasi, E. Ebadifallah, H. Rousta, M. Katouli, B.S. Virdee. Planar Monopole Antenna Employing Back-Plane Ladder-Shaped Resonant Structure for Ultra-Wideband Performance. Iet Microwaves, Antennas and Propagation, Vol. 4, ISS. 9, 2010. - 1327-1335 PP.

4. Revision of part 15 of the Commission's Rules Regarding Ultra-Wideband Transmission Systems, Federal Communications Commission, FCC 02-48, 2002. - 118 p.

The world is not without good people:-)
Valery UR3CAH: "Good afternoon, Egor. I think this article (namely," fractal antennas: better less, yes better ") corresponds to the subject of your site and will be interesting to you :) 73!"
Yes, of course interesting. We have already concerned about this topic to some extent when discussing Gexabim Geometry. There, too, there was a dilem with "locking" of the electrical length in geometric dimensions :-). So thanks, Valery, great for the material sent.
Fractal antennas: better less, yes better
Over the past half a century, life has rapidly change. Most of us takes achievements modern technologies How proper. To all that makes life more comfortable, you get used to very quickly. Rarely who wonders "Where did it come from?" And "How does it work?". The microwave oven heats breakfast - well, well, the smartphone makes it possible to talk to another person - excellent. It seems to us an obvious opportunity.
But life could be completely different if a person did not seek explanations to the events. Take, for example, cell Phones. Remember the retractable antennas in the first models? They interfered, increased the size of the device, in the end, often broke. We believe, they are ever sunk in the fly, and in part of the fault ... Fractals.
Fractal drawings fascinate with their patterns. They definitely resemble images of cosmic objects - nebulae, accumulation of galaxies and so on. Therefore, it is quite natural that when Mandelbrot voiced his theory of fractals, his studies aroused increased interest among those who were engaged in the study of astronomy. One of these lovers named Nathan Cohen (Nathan Cohen) After visiting the lecture, Benua Mandelbrot in Budapest caught fire the idea practical application knowledge gained. True, he did it intuitively, and not a last role in his opening played the case. Being a radio amateur, Nathan sought to create an antenna who has as much sensitivity as much as possible.
The only way to improve the antenna parameters, which was known at that time, was to increase its geometric sizes. However, the owner of housing in the center of Boston, which was rented Nathan, was categorically against the installation of large roof devices. Then Nathan began to experiment with various forms of antennas, trying to get the maximum result with minimal sizes. Turning around the idea of \u200b\u200bfractal forms, Cohen, what is called, Naobum made one of the most famous fractals from the wire - "Snezhinka Koch". Swedish mathematician Helge von Koch (Helge Von Koch) came up with this curve back in 1904. It is obtained by dividing the segment into three parts and replacing the middle segment with an equilateral triangle without a part that coincides with this segment. The definition is a bit complicated for perception, but in the figure everything is clear and simple.
There are also other varieties of the "Koch curve", but the approximate form of the curve remains similar.

When Nathan connected the antenna to the radio reception, it was very surprised - the sensitivity increased dramatically. After the experiment series, the future Professor of the University of Boston realized that the antenna made on a fractal figure has a high efficiency and covers a much wider frequency range compared to classical solutions. In addition, the form of antenna in the form of a fractal curve allows to significantly reduce geometric dimensions. Nathan Cohen even led the theorem proving that to create a broadband antenna, it suffices to give it the form of a self-like fractal curve.

The author patented his opening and founded the firm for the development and design of Fractal Antennas Fractal Antenna Systems, rightly believing that in the future, thanks to its discovery, cell phones will be able to get rid of cumbersome antennas and become more compact. In principle, it happened. True, to this day Nathan is judged with large corporationswho illegally use its discovery to produce compact communication devices. Some famous manufacturers mobile devicesAs, for example, Motorola has already come to a peaceful agreement with the inventor of a fractal antenna. First source

Wire fractal antennas, studied in this appearance, were made by curving the wire along the paper template printed on the printer. Since the wire was bent manually using a tweezers, the accuracy of the manufacture of "bends" antenna was about 0.5 mm. Therefore, for research, the most simple geometric fractal forms were taken: the Koch curve and the "bipolar leap" of Minkovsky.

It is known that fractals make it possible to reduce the size of the antennas, while the size of the fractal antenna is compared with the dimensions of the symmetric half-wave linear dipole. In further studies in the graduation work, wire fractal antennas will be compared with a linear dipole with C / 4-shoulders equal to 78 mm with a resonant frequency of 900 MHz.

Wire fractal antennas based on Koch curve

The paper presents formulas for calculating fractal antennas based on the koch curve (Figure 24).

but) n. \u003d 0 b) n. \u003d 1 V) n. = 2

Figure 24 - Koch curve of various iterations n

Dimension D. The generalized fractal koch is calculated by the formula:

If in formula (35) substitute the standard bending angle of the koch curve \u003d 60, then we get D. = 1,262.

The dependence of the first resonant frequency of the dipole koch f. To from the dimension of fractal D., Iteration numbers n. and resonant frequency of a straight line dipole f. D of the same height as broken koch (at extreme points) is determined by the formula:

For Figure 24, b when n. \u003d 1 I. D. \u003d 1.262 from formula (36) We get:

f. K \u003d. f. D 0,816, f. K \u003d 900 MHz 0.816 \u003d 734 MHz. (37)

For Figure 24, in with n \u003d 2 and d \u003d 1.262 from formula (36) we obtain:

f. K \u003d. f. D 0,696, f. K \u003d 900 MHz 0.696 \u003d 626 MHz. (38)

Formulas (37) and (38) allow you to solve and feedback - if we want fractal antennas to work at frequency f. K \u003d 900 MHz, then straight dipoles should work at the following frequencies:

for n \u003d 1 f d \u003d f k / 0,816 \u003d 900 MHz / 0.816 \u003d 1102 MHz, (39)

for n \u003d 2 f d \u003d f k / 0,696 \u003d 900 MHz / 0.696 \u003d 1293 MHz. (40)

According to the graph in Figure 22, we determine the lengths / 4-shoulders of a straight line dipole. They will be equal to 63.5 mm (for 1102 MHz) and 55 mm (for 1293 MHz).

Thus, 4 fractal antennas were made based on Koch curve: two - with dimensions / 4-shoulders of 78 mm, and two with smaller sizes. Figures 25-28 shows the images of the RK2-47 screen, according to which you can experimentally define resonant frequencies.

Table 2 summarizes the calculated and experimental data, of which it can be seen that theoretical frequencies f. T differ from the experimental f. E no more than 4-9%, and this is quite a good result.

Figure 25 - Screen of RK2-47 when measuring an antenna with an iteration curve of iteration N \u003d 1 C / 4-shoulders equal to 78 mm. Resonant frequency 767 MHz

Figure 26 - Screen of PK2-47 when measuring an antenna with an iteration curve of iteration N \u003d 1 C / 4-shoulders equal to 63.5 mm. Resonant frequency 945 MHz

Figure 27 - Screen of RK2-47 when measuring an antenna with antenna curve of iteration N \u003d 2 C / 4-shoulders equal to 78 mm. Resonance frequency 658 MHz

Figure 28 - Screen of RK2-47 when measuring an antenna with an iteration curve of iteration N \u003d 2 C / 4-shoulders equal to 55 mm. Resonant frequency 980 MHz

Table 2 - comparison of the calculated (theoretical FT) and experimental FE resonance frequencies of fractal antennas based on Koch curve

Wire fractal antennas based on a "bipolar jump". Foci Chart

Fractal lines of the "bipolar leap" are described in operation, however, the formulas for calculating the resonant frequency depending on the size of the antenna in operation is not given. Therefore, it was decided to determine the resonant frequencies experimentally. For simple fractal lines of the 1st iteration (Figure 29, b) 4 antennas were manufactured - with a length of / 4-shoulders equal to 78 mm, with twice as long as long and two intermediate lengths. For complicated in the manufacture of fractal lines of the 2nd iteration (Figure 29, B), 2 antennas were made with lengths / 4-shoulders 78 and 39 mm.

Figure 30 shows all manufactured fractal antennas. Figure 31 shows the appearance of the experimental installation with a fractal antenna "bipolar leap" of the 2nd iteration. Figures 32-37 shows the experimental definition of resonant frequencies.

but) n. \u003d 0 b) n. \u003d 1 V) n. = 2

Figure 29 - Minkowski curve "Bipolar leap" of various iterations n

Figure 30 - appearance of all manufactured wire fractal antennas (wire diameters 1 and 0.7 mm)

Figure 31 - Experimental Installation: Panoramic meter KSVN and weakening of RK2-47 with fractal antenna type "Bipolar leap" of the 2nd iteration

Figure 32 - Screen of RK2-47 when measuring the antenna "Bipolar leap" of iteration n \u003d 1 C / 4-shoulders equal to 78 mm.

Resonant frequency 553 MHz

Figure 33 - Screen of RK2-47 when measuring the antenna "Bipolar leap" of iteration n \u003d 1 C / 4-shoulders equal to 58.5 mm.

Resonant frequency 722 MHz

Figure 34 - RK2-47 screen when measuring the "bipolar leap" antenna of iteration N \u003d 1 C / 4-shoulders equal to 48 mm. Resonant frequency 1012 MHz

Figure 35 - RK2-47 screen when measuring the "bipolar leap" antenna of iteration n \u003d 1 C / 4-shoulders equal to 39 mm. Resonant frequency 1200 MHz

Figure 36 - RK2-47 screen when measuring the antenna "bipolar leap" of iteration n \u003d 2 C / 4-shoulders is 78 mm.

First resonant frequency 445 MHz, Second - 1143 MHz

Figure 37 - RK2-47 screen when measuring the antenna "Bipolar leap" of iteration N \u003d 2 C / 4-shoulders equal to 39 mm.

Resonant frequency 954 MHz

As shown by experimental studies, if we take a symmetrical half-wave linear dipole and the fractal antenna of the same lengths (Figure 38), then fractal antennas like a "bipolar jump" will operate at a lower frequency (by 50 and 61%), and fractal antennas in the form of a curve Koch operates at frequencies below 73 and 85% than the linear dipole. Therefore, indeed, fractal antennas can be done smaller. Figure 39 shows the dimensions of fractal antennas for the same resonance frequencies (900-1000 MHz) in comparison with the shoulder of the usual half-wave dipole.

Figure 38 - "Normal" and fractal antennas of the same length

Figure 39 - Antenna dimensions for the same resonance frequencies

5. Measurement of fractal antennas radiation diagrams

The antennic patterns are usually measured in the "non-email" chambers, the walls of which are absorbed by the emissions falling on them. In this thesis, measurements were carried out in a conventional laboratory of the physico-technical faculty, and the reflected signal from metal enclosures and iron stands made some error in measurements.

As a source of microwave signal, a private generator of the Panoramic Meter of KSWN and the attenuation of RK2-47 was used. As a receiver of a fractal antenna radiation receiver, an ATT-2592 electromagnetic field level was used, which allows measurements in the frequency range from 50 MHz to 3.5 GHz.

Preliminary measurements have shown that significantly distorts the diagram of the pattern of symmetric half-wave linear dipole radiation from the outside coaxial cablewhich was directly (without matching devices) connected to the dipol. One of the ways to reduce the transfer line is the use of a monopoly instead of a dipole together with four mutually perpendicular / 4 "counterweights" playing the role of "land" (Figure 40).

Figure 40 - / 4 Monopol and fractal antenna with "counterweights"

Figures 41 - 45 shows the experimentally measured patterns of the direction of the studied antennas with "counterweights" (the resonant frequency of radiation during the transition from the dipole to the monopoly is practically not changed). Measurements of the density of the power flow of the microwave radiation in the microbrats per square meter were carried out in horizontal and vertical planes through 10. Measurements were carried out in the "long" antenna zone at a distance of 2.

The first was studied an antenna in the form of a straight-line / 4-vibrator. From the selectivity diagram of this antenna, it can be seen (Figure 41), which is different from the theoretical. This is explained by the measurement errors.

Measurement errors for all the antennas studied may be the following:

Reflection of radiation from metal objects inside the laboratory;

The absence of strict mutual perpendicularity between the antenna and counterweights;

Not a complete suppression of the radiation of the outer shell of the coaxial cable;

Inaccuracy of the countdown of angular values;

Inaccurate "targeting" of the ATT-2592 meter on the antenna;

Interference from cell phones.