printed dipole antenna

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PRINTED DIPOLE ANTENNA

a) Theoretical background of the antenna including feeding types.

Introduction to Dipole AntennaA dipole antenna, created by Heinrich Rudolph Hertz around 1886, is an antenna that

can be made by a simple wire, with a center-fed driven element for transmitting or receiving radio frequency energy. These antennas are the simplest practical antennas from a theoretical point of view; the current amplitude on such an antenna decreases uniformly from maximum at the center to zero at the ends.

A schematic of a half-wave dipole antenna that a shortwave listener might build

The dipole antenna is simply two wires pointed in opposite directions arranged either horizontally or vertically, with one end of each wire connected to the radio and the other end hanging free in space. Since this is the simplest practical antenna, it is also used as reference model for other antennas; gain with respect to a dipole is labeled as dBd. Generally, the dipole is considered to be omnidirectional in the plane perpendicular to the axis of the antenna, but it has deep nulls in the directions of the axis. Variations of the dipole include the folded dipole, the half wave antenna, the groundplane antenna, the whip, and the J-pole.

The transmission line is often known as a feed element. When the waves reach the antenna, they oscillate along the length of the antenna and back. Each oscillation pushes electromagnetic energy from the antenna, emitting the energy through free space as radio waves. Ideally, a half-wave (λ/2) dipole should be fed with a balanced line matching the theoretical 73 ohm impedance of the antenna. A folded dipole uses a 300 ohm balanced feeder line.

Many people have had success in feeding a dipole directly with a coaxial cable feed rather than a ladder-line. However, coax is not symmetrical and thus not a balanced feeder. It is unbalanced, because the outer shield is connected to earth potential at the other end. When a balanced antenna such as a dipole is fed with an unbalanced feeder, common mode currents can cause the coax line to radiate in addition to the antenna itself, and the radiation pattern may be asymmetrically distorted. This can be remedied with the use of a balun.

The Design and Specification of Dipole Antenna

Properties of Dipole AntennaA Dipole antenna’s size and shape depend on the intended frequency or wavelength of

the radio waves being sent or received. The design of a transmitting antenna is usually not different from that of a receiving antenna. Some devices use the same antenna for both purposes.

COMMUNICATION SYSTEM

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i. Size An antenna works best when its physical size corresponds to a quantity known as the antenna’s electrical size. The electrical size of an antenna depends on the wavelength of the radio waves being sent or received. An antenna radiates energy most efficiently when its length is a particular fraction of the intended wavelength. When the length of an antenna is a major fraction of the corresponding wavelength (a quarter-wavelength or half-wavelength is often used), the radio waves oscillating back and forth along the antenna will encounter each other in such a way that the wave crests do not interfere with one another. The waves will resonate, or be in harmony, and will then radiate from the antenna with the greatest efficiency.

ii. Shape Antennas come in a wide variety of shapes. One of the simplest types of antennas is called a dipole. A dipole is made of two lengths of metal, each of which is attached to one of two wires leading to a radio or other communications device. The two lengths of metal are usually arranged end to end, with the cable from the transmitter or receiver feeding each length of the dipole in the middle. The dipoles can be adjusted to form a straight line or a V-shape to enhance reception. Each length of metal in the dipole is usually a quarter-wavelength long, so that the combined length of the dipole from end to end is a half-wavelength. The familiar “rabbit-ear” antenna on top of a television set is a dipole antenna.

iii. Directivity Directivity is an important quality of an antenna. It describes how well an antenna concentrates, or bunches, radio waves in a given direction. A dipole transmits or receives most of its energy at right angles to the lengths of metal, while little energy is transferred along them. If the dipole is mounted vertically, as is common, it will radiate waves away from the center of the antenna in all directions. However, for a commercial radio or television station, a transmitting antenna is often designed to concentrate the radiated energy in certain directions and suppress it in others. For instance, several dipoles can be used together if placed close to one another. Such an arrangement is called a multiple-element antenna, which is also known as an array. By properly arranging the separate elements and by properly feeding signals to the elements, the broadcast waves can be more efficiently concentrated toward an intended audience, without, for example, wasting broadcast signals over uninhabited areas.

The elements used in an array are usually all of the same type. Some arrays have the ability to move, or scan, the main beam in different directions. Such arrays are usually referred to as scanning arrays.

Arrays are usually electrically large and have better directivity than single element antennas. Since their directivity is large, arrays can capture and deliver to the receiver a larger amount of power.

The Dipole Antenna ParameterThere are several critical parameters that affect an Dipole antenna's performance and

can be adjusted during the design process. These are resonant frequency, impedance, gain, aperture or radiation pattern, polarization, efficiency and bandwidth. Transmit antennas may also have a maximum power rating, and receive antennas differ in their noise rejection properties.


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i. Resonant frequency The resonant frequency is related to the electrical length of the antenna. The electrical length is usually the physical length of the wire multiplied by the ratio of the speed of wave propagation in the wire. Typically an antenna is tuned for a specific frequency, and is effective for a range of frequencies usually centered on that resonant frequency. However, the other properties of the antenna (especially radiation pattern and impedance) change with frequency, so the antenna's resonant frequency may merely be close to the center frequency of these other more important properties.

Dipoles that are much smaller than the wavelength of the signal are called Hertzian, short, or infinitesimal dipoles. These have a very low radiation resistance and a high reactance, making them inefficient, but they are often the only available antennas at very long wavelengths. Dipoles whose length is half the wavelength of the signal are called half-wave dipoles, and are more efficient. In general radio engineering, the term dipole usually means a half-wave dipole (center-fed).

A half-wave dipole is cut to length according to the formula [ft], where l is the length in feet and f is the center frequency in MHz. This is because the impedance of the dipole is resistive pure at about this length. The metric formula is [m], where l is the length in meters. The length of the dipole antenna is about 95% of half a wavelength at the speed of light in free space.

The magic numbers above are derived from a one Hz wavelength which is the distance that light radio travels in one second. For English that is 186,282 miles times 5280 feet per mile. To convert to metric multiply the previous total by 12 inches per foot and then, by definition, multiply that by 2.54 cm per inch. Divide this number by 100 to convert this length to meters. Then divide the result by one million to account for MHz rather than hertz. This will give a number which must be divided by two for a dipole antenna. To correct for resistance and impedance multiply the dipole wavelength by about 95% to account for the difference in the velocity of wave propagation in wire as opposed to the same wave in free space. If the wire velocity is known, that value should be used to get the magic numbers of 468 feet or 142.65 metric. All that is left is to divide by the desired frequency as measured in MHz to obtain the length of the antenna element.

ii. Gain and Radiation Pattern In antenna design, gain is the logarithm of the ratio of the intensity of an antenna's radiation pattern in the direction of strongest radiation to that of a reference antenna. If the reference antenna is an isotropic antenna, the gain is often expressed in units of dBi (decibels over isotropic). For example, a dipole antenna has a gain of 2.14 dBi. Often, the dipole antenna is used as the reference (since a perfect isotropic reference is impossible to build), in which case the gain of the antenna in question is measured in dBd (decibels over dipole).


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Radiation pattern and gain

Dipoles have a toroidal (doughnut-shaped) reception and radiation pattern where the axis of the toroid centers about the dipole. The theoretical maximum gain of a Hertzian dipole is 10 log 1.5 or 1.76 dBi. The maximum theoretical gain of a λ/2-dipole is 10 log 1.64 or 2.15 dBi.

iii. Bandwidth

The bandwidth of an antenna is the range of frequencies over which it is effective, usually centered around the resonant frequency. The bandwidth of an antenna may be increased by 13 several techniques, including using thicker wires, replacing wires with cages to simulate a thicker wire, tapering antenna components (like in a feed horn), and combining multiple antennas into a single assembly and allowing the natural impedance to select the correct antenna. Small antennas are usually preferred for convenience, but there is a fundamental limit relating bandwidth, size and efficiency.

iv. Impedance Impedance is similar to refractive index in optics. As the electric wave travels through the different parts of the antenna system (radio, feed line, antenna, free space) it may encounter differences in impedance. At each interface, some fraction of the wave's energy will reflect back to the source, forming a standing wave in the feed line. The ratio of maximum power to minimum power in the wave can be measured and is called the standing wave ratio (SWR). A SWR of 1:1 is ideal. A SWR of 1.5:1 is considered to be marginally acceptable in low power applications where power loss is more critical, although an SWR as high as 6:1 may still be usable with the right equipment. Minimizing impedance differences at each interface (impedance matching) will reduce SWR and maximize power transfer through each part of the antenna system.

Complex impedance of an antenna is related to the electrical length of the antenna at the wavelength in use. The impedance of an antenna can be matched to the feed line and radio by adjusting the impedance of the feed line, using the feed line as an impedance transformer. More commonly, the impedance is adjusted at the load (see below) with an antenna tuner, a balun, a matching transformer, matching networks composed of inductors and capacitors, or matching sections such as the gamma match.

v. Polarization The polarization of an antenna or orientation of the radio wave is determined by the electric field or E-plane. The ionosphere changes the polarization of signals unpredictably, so for signals which will be reflected by the ionosphere, polarization is


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not crucial. However, for line-of-sight communications, it can make a tremendous difference in signal quality to have the transmitter and receiver using the same polarization. Polarizations commonly considered are linear, such as vertical and horizontal, and circular, which is divided into right-hand and left-hand circular.

vi. Efficiency Efficiency is the ratio of power actually radiated to the power put into the antenna terminals. A dummy load may have a SWR of 1:1 but an efficiency of 0, as it absorbs all power and radiates heat but not RF energy, showing that SWR alone is not an effective measure of an antenna's efficiency. Radiation in an antenna is caused by radiation resistance which can only be measured as part of total resistance including loss resistance. Loss resistance usually results in heat generation rather than radiation, and therefore, reduces efficiency.

Common Applications Of Dipole Antennas

i. Set-top TV antenna The most common dipole antenna is the "rabbit ears" type used with televisions. While theoretically the dipole elements should be along the same line, "rabbit ears" are adjustable in length and angle. Larger dipoles are sometimes hung in a V shape with thecenter near the radio equipment on the ground or the ends on the ground with the center supported. Shorter dipoles can be hung vertically.

ii. Folded dipole Another common place one can see dipoles are as antennas for the FM band - these are folded dipoles. The tips of the antenna are folded back until they almost meet at the feedpoint, such that the antenna comprises one entire wavelength. The main advantage of this arrangement is an improved bandwidth over a standard halfwave dipole.

iii. Shortwave antenna Dipoles for longer wavelengths are made from solid or stranded wire. Portable dipole antennas are made from wire that can be rolled up when not in use. Ropes with weights on the ends can be thrown over supports such as tree branches and then used to hoist up the antenna. The center and the connecting cable can be hoisted up with the ends on the ground or the ends hoisted up between two supports in a V shape. While permanent antennas can be trimmed to the proper length, it is helpful if portable antennas are adjustable to allow for local conditions when moved.

It is important to fit a good insulator at the ends of the dipole, as failure to do so can lead to a flashover if the dipole is used with a transmitter. One cheap insulator is the plastic carrier that holds a pack of beer cans together. This beer can insulator is an example of how a household object can be used in place of an expensive object sold for use as an item of radio equipment. Other objects that can be used as insulators include buttons from old clothing.

Article 1: A Broadband Printed Dipole and a Printed Array for Base Station Applications

b) The antenna design and specifications.


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The integrated balun consists of a microstrip line and a slot line which are printed on the front side and the back side of the substrate, respectively; the dipole is printed on the backside as well. This structure is designed for wireless base station applications at the 2-GHz band, which covers the frequency range from 1.7 GHz to 2.5 GHz.

c) The improvement that have been made on the antenna.The improvement that had been made on the antenna is the adjustment of the feed point

of the integrated balun, featuring a broadband performance and flexibility for the matching to different impedance values.

d) The methods that have been used to achieve the improvement as in c).The printed dipole with adjusted integrated balun is mounted above a ground plane with

dimensions of 200 mm × 160 mm and fed by an SMA connector underneath the ground plane. To keep the antenna profile as low as possible, the slot line is short circuited directly by the ground plane. As a result, the height of the antenna (from the center of the printed dipole to the ground) is roughly a quarter wavelength of the slotline.

e) Conclusions.A printed dipole with an adjusted integrated balun is developed. It is found that this

topology can directly match to a 50-Ω feed and has a bandwidth of more than 40%. The broadband impedance matching can be achieved simply by adjusting the position of the feed point of the integrated balun which is useful for antenna arrays.

Article 2: A Novel Broadband Printed Dipole Antenna with Low Cross-Polarization

b) The antenna design and specifications.A novel broadband printed dipole antenna with low cross-polarization works on the principle of by employing a double-layered structure where the E-field component perpendicular to the dipole arms is minimized and thus low cross-polarization is obtained. This structure employs a novel double-layered printed dipole antenna with integrated baluns with an addition of dielectric layers with printed dipoles for the purpose of suppressing the cross-polarized field component.

The double-layered printed dipole with integrated baluns is shown in figure 1. As observed in the figure, the double-layered dipole employs two layers of substrates. For a conventional single-layered printed dipole, there is a relatively strong transverse E-field component, which is perpendicular to the dipole arms and contributes to the cross-polarization component in the far-field. Thus, double-layered printed dipole with two layers of substrates is used to improve the cross-polarization characteristic.

The proposed double-layered printed dipole antenna with integrated balun is designed and fabricated at a center frequency of about 3.25 GHz. The selected dielectric substrate has the dielectric constant of 2.2 ± 0.02 and a thickness of 0.7874 mm. The nominal dielectric loss tangent of this material is 0.0009 at 10 GHz. The aluminium ground plate is selected to be 240 mm x 240 mm x 4mm.


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Figure 1: The Double-Layered Printed Dipole Antenna with its Geometry

c) The improvement that have been made on the antenna.The simulation diagram of the measured and simulated return loss of the double-layered

printed dipole antenna is shown in figure 2. The return loss bandwidth is about 42% for simulated while for measured is about 50%.

Figure 2: Simulated and Measured Return Loss versus Frequency

At frequency of 3.25 GHz, the measured and simulated radiation patterns both of the E-plane and H-plane are shown in figure 3. The measured 3 dB beamwidths are about 73o and 120o in the E and H plane respectively. However, the measured cross-polarization at broadside is about 36.0 and 47.9 dB down compared with the co-polarization levels in E and H plane respectively.

(a) E-Plane (b) H-Plane

Figure 3: Comparison of Measured and Simulated Radiation Patterns at 3.25 GHZ


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The measured and simulated gain and cross-polarization level at broadside versus frequency are plotted in figure 4. The measured gain varies from 4.5 – 7.2 dBi across the frequency band from 2.6 – 4.6 GHz. At higher frequency, the 3 dB beamwidths in the E and H plane increase, and the radiation patterns begin to split. The beam split becomes serious at about 4.4 GHz and above. The measured cross-polarization levels at broadside are typically less than -30 dB from 2.6 – 4.6 GHz that is about 55% of the frequency band.

d) The methods that have been used to achieve the improvement as in c).The first single-layered printed dipole is adopted face-to-face to another single-layered

printed dipole with their microstrip feed lines combined into one and forms a stripline balun to minimize the transverse E-field components. Thus, the transverse E-field component perpendicular to the dipole arms is expected to counter-acted resulted in lower cross-polarization. The radiating structure for the double-layered dipole has the geometry symmetry in both of the E and H plane. As a result, there will be no beam squint in both of the E and H plane radiating patterns. The symmetry radiating structure also found to be more effective for the suppression of the transverse-field component, thus a lower cross-polarization is expected.

e) Conclusions.By comparing with the conventional single-layered dipole antenna, an extra layer of substrate with printed dipole is added to counteract the cross-polarization component. From the results, it shows that the new dipole antenna achieves a bandwidth over 50% while reducing the cross-polarization level to less than -30 dB within the frequency band. The double-layered printed dipole antenna can be expanded into large scale array and it is suitable for application with low cross-polarization required.

Article 3: A Printed Dipole Antenna for Ultra High Frequency (UHF) Radio Frequency Identification (RFID) Handheld Reader

b) The antenna design and specifications.The proposed new printed dipole antenna for UHF RFID systems consists of a

microstrip-to-coplanar stripline transition, a meandered driven dipole, a closely-coupled parasitic element and a folded finite size ground plane. The antenna should demonstrate a somewhat lower return loss level than that in a usual communication system. This is due to such a system the backscattered signal from a tag is relatively weak and prone to be interfered by the strong reflected signal from the reader antenna terminal. In addition, regarding the public exposure to electromagnetic field and the associate health issue, it would be beneficial if one could design a RFID reader handheld reader antenna with high front-to-back ratio so that the absorbed electromagnetic energy by the users can be substantially reduced.

The design antenna is consisting of microstrip-to-coplanar stripline balun, a meandered printed dipole, a closely coupled parasitic element, and a folded finite size ground plane. The geometry of the proposed antenna is shown in figure 1 with the design parameters. It is suitable for application operating for a frequency of 902 – 928 MHz.


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(a) (b)

Figure 1: Proposed Antenna Configuration (a) Top View and (b) Oblique View

The design parameters for the above designation are: Wm = 2 mm, Lm = 30mm, Lab = 50.5 mm, Lb = 25mm, LCPS = 50 mm, WCPS = 5 mm, GCPS = 2 mm, LD1 = 17 mm, LD2 = 8 mm, LD3 = 15 mm, WD = 3 mm, LP1 = 18 mm, LP2 = 23 mm, LP3 = 8 mm, LP4 = 40 mm, GP = 1 mm, WP = 2 mm, GDP = 2 mm, Wtop = 60 mm, Ltop = 30 mm, Wbot = 50 mm, Lbot1 = 20 mm, Lbot2 = 19 mm, Wtune = 8 mm, Ltune = 16mm and Gtune = 1 mm.

c) The improvement that have been made on the antenna.Figure 2 shows the simulated and measured antenna return loss. From the figure, it was

found that both of the results had reasonable agreement over the frequency band of interest. The simulated and measured center frequencies are 907 MHz and 917 MHz respectively. In addition, the simulated 10 and 14 dB return loss bandwidth are from 885 – 966 MHz and from 893 – 937 MHz respectively. While the corresponding measured data give the value of 892 – 990 MHz and 898 – 967 MHz respectively.

Figure 2: Simulated and Measured Return Loss

Figure 4 and 5 show the simulated and measured E and H plane radiation pattern at 902, 915 and 928 MHz. As illustrated in the figure, it found that a fairly good agreement between the simulated and measured result can be observed over the frequency band of interest. The simulated front-to-back ratio is at least 8.5 dB at 902 MHz and reaches 11.5 dB at 928 MHz. While the measured result shows that the antenna front-to-back ratio can be as high as 13 dB at 928 MHz. From figure 4 and 5, it is noted that both principal cuts the measured cross-


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polarization level generally less than -20 dBi. This observation suggest that the proposed design demonstrates well-behaved end fired radiation with high polarization purity towards positive x direction.

Figure 4: Simulated and Measured Radiation Patterns in the E-Plane at 902, 915 and 928 MHz

Figure 5: Simulated and Measured Radiation Patterns in the H-Plane at 902, 915 and 928 MHz

d) The methods that have been used to achieve the improvement as in c).The antenna is designed for UHF RFID application in the frequency range of 902 – 928

MHz. The proposed antenna consists of microstrip-to-CPS Marc-hand balun, a driven pole, a parasitic element and a truncated ground plane. A 50Ω micostrip line is used to feed the antenna via a SMA connecter. A microstrip-to-CPS Marc-hand balun serves as a matching network, is inserted between the feed line and the dipole element. The lengths of the driven dipole and the parasitic element are optimized for simultaneously achieving excellent input impedance matching and high antenna front-to-back ratio and the dipole arms are meandered to reduce the occupied dimension.

A tuning stub also be introduced to the microstrip feed line and the tuning stab is electrically connected to the top ground and provides a capacitive loading between the feed line and the ground line. It has the ability of improving the antenna input impedance matching.

e) Conclusions.In conclusion, the proposed antenna has the feature of compact size of λg/2 x λg/2, wide 14 dB return loss bandwidth of around 60 MHz, high front-to-back ration from 9 to 13 dB. The designed antenna may find its wide variety application in the areas such as in items level


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automation management, warehouse management, access control system as well as electronic toll collection with UHF RFID techniques.

Article 4: A Printed Dipole Antenna for Wideband Circular Polarization Operation

b) The antenna design and specifications.In this paper, a novel printed dipole antenna for wideband circular polarization is

proposed, which comprises a pair of unequal arms with a small gap which is fed by an L shaped microstrip feedline through a via.

The geometry of the proposed dipole antenna. (a) Profile (b) Rear Side (c) Front Side

Circular polarization is widely used in Satellite Communications Systems, Global Positioning System (GPS), and Radio Frequency Identification (RFID), because circularly polarized characteristics can reduce multipath effects and provide flexibility in the orientation angle between a transmitter and a receiver. There are a number of types of circularly polarized printed antennas. Most of them are reported as various patch antennas, which operate by using small perturbations providing the degenerate modes and 90 degree phase difference. Various techniques for broadband circular polarization have been reported using a radiating element, a parasitic element and a stacked structure.

The configuration of the proposed printed dipole antenna is shown in figure above. The L-shaped microstrip feedline is located in the centre of the printed dipole antennas and a vertical short strip is connected to the arm of the dipole antenna through via. As shown in figure above, the printed dipole antenna has a L-shaped microstrip feed line which can be considered as microstrip balun. A longer arm of printed dipole and the length of balun are approximately quarter of the wavelength.

By utilizing the coupling effects between unequal arms of dipole antenna and vertical microstrip balun, the degenerated resonant modes with 90 degree phase difference are provided. The proposed antenna is printed on the Taconic substrate, permittivity 3.5, the thickness 1.57mm, the tan loss 0.0018. The substrate size is 30mm×36mm.Various parameters are also noted in figure above.

c) The improvement that have been made on the antenna.d) The methods that have been used to achieve the improvement as in c).

The improvement that have been made and the methods that have been used to achieved the improvement.


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No.The Improvement That

Have BeenThe Methods That Have Been Used To

Achieve The Improvement1. Wide band circular

polarization Comprises a pair of unequal arms with a small gap which is feed by an L- shaped microstrip feedline through via. Dipole antenna geometry is arranged so that the orthogonal surface current has the appropriate phase to provide circular polarization.

2. Impedance Bandwidth Variation of the width of printed arms.By make the width of the arms to be narrow, the impedance matching become batter.As the length of the arm Ls2 is shorted, the impedance bandwidth has significantly changed.When the width of the antenna gap is decreases, the impedance bandwidth become wider.

3. Resonant By utilizing the coupling effects between unequal arms of dipole antenna and vertical microsrip balun, the degenerated resonant modes with 90 degree phase difference are provided.By make the width of the arms to be narrow, the frequency will be shifted upward.

4. Return loss By changed the location of the feed point, the return loss will also alter.As the length of the gap is changed, the changed of return loss also occurred. The length of gap will affect on the location of return loss.

e) Conclusions.Circularly polarized characteristics can reduce multipath effects and provide flexibility in the orientation angle between a transmitter and a receiver. Recently, various printed dipole antennas have been realized due to several attractive features, such as broad bandwidth, lower profile, and lighter weight. A novel printed antenna composed of an asymmetrical dipole and a slotted groundplane, which is fed by L- shaped microstrip line and via, is proposed for wideband circular polarization. By adjusting the length and width of slot/gap, an 3 dB axial ratio bandwidth of greater than 20% is possible.

Article 5: Scattering Analysis Of A Printed Dipole Antenna Using PBG Structures



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Figure below shows a structure and dimensions of a printed dipole antenna which is designed on substrate where consist a dielectric constant of 2.65 and a substrate thickness of 1.6 mm. The length L = λ0/2 = 50 mm, R = 12 mm, M = λ0/4 = 25 mm, S = 27mm and N = 0.4L × 0.5L = 23 mm. In addition, the form of coupling feed is used at the reverse side of substrate. To get efficient excitation and good impedance matching, the length of the protruded strip is can be said as L, l1, l2, l3 and l4 which the length are 14 mm, 0.5 mm, 0.5 mm, 7.5mm and 14 mm, respectively. To excite the wideband operation with good impedance matching, the length of L, l1, l2, l3 and l4 can be adjusted so that the antenna can be achieve in the range of 2.5 to 4.0GHz impedance bandwidth.

Geometry of the proposed microstrip printed dipole antenna.

The figure shows a PBG ground which consisting the square loop structure. It was proved by Bragg reflection factor in optics that the period of PBG structure is about a half of wavelength. Moreover, the period aperture is used to carve on the ground to achieve PBG structure.

Geometry of the proposed PBG ground.

The frequency of PBG structure can be determined by a constant of the distance between apertures. The centered frequency f of a gap frequency range is function of structure period and the wavelength in the centered frequency is two times as long as the period d. So f is given by

where c is the speed of light, d is structure period and is relative permittivity.


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Measured VSWR for the proposed antenna.

c) The improvement that have been made on the antenna.Broadband design of a printed dipole antenna is using PBG (photonic band-gap)

structures. PBG structures are often used for high impedance ground plane, suppressing surface waves at operating frequencies. The form of coupling feed is used so that the size of the proposed antenna which is 45mm × 35mm is obtained and the ground plane uses PBG having the Structure of the square loop. The maximum impedance bandwidth (2.5–4.0 GHz) is formed by the antenna. Meanwhile, the RCS is reduced by 15 dB at resonance frequency and the performance of antenna radiation keep unchanging compared with the microstrip printed dipole antenna not using PBG structures. The figure plots the measured radiation patterns in the E plane and H plane for the microstrip printed dipole antenna above an ideal PEC surface and a realistic metallic PBG surface. Since, the radiation characteristics of the antenna above a realistic metallic PBG surface are better than above an ideal PEC surface where it has a peak antenna gain of 6.06 dB for antenna above a realistic metallic PBG surface while for antenna above an ideal PEC surface is 5.27 dB.

Measured radiation patterns for PBG and PEC

d) The methods that have been used to achieve the improvement as in c).To improve the antenna gain from 6.06 dB to 5.27 dB, the antenna is design above a

realistic metallic PBG surface. Moreover PBG ground plane can increase RCS from 3.7 GHz to 4.5 GHz.

FMM (Fast Multipole Method) is used to analyze scattering property of the printed dipole antenna. For achieving efficient excitation and good impedance matching, the length of the protruded strip is denoted as L, l1, l2, l3 and l4 of which the optimal length are found to be 14 mm, 0.5 mm, 0.5 mm, 7.5mm and 14 mm. By varying the length of L, l1, l2, l3 and l4, the


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wideband operation of the microstrip printed dipole antenna can be excited with good impedance matching.

e) Conclusions.In conclusion, the method was discovered a reduction of RCS. Since the centered frequency

of reduction can be chosen according to requirement. The main advantage is the design of the antenna above a realistic metallic PBG surface is can be said batter than above an ideal PEC surface.

Article 6: Printed-Circuit Elliptical Dipole Antenna for 3.1-10.6 GHz UWB Application

b) The antenna design and specifications.The geometry of a printed-circuit elliptical dipole antenna is presented in the figure

below. Since there are the same photographs of elliptical dipole antennas of the same design but fabricated with different dielectric constant, 4.2 and 10.2 is shown. In its simplest configuration, antenna dipole with the upper and lower radiation elements having an elliptical shape is designed to produce a broad-beamwidth and broad bandwidth with linear polarization.

In the lower elliptic radiator, a portion of the area is cut off in the shape of an ellipse to accommodate the 50 ohm micro stripe feed line. This 50 ohms feed line extends into the dipole center or attached point of the two adjacent elliptical radiators. It was found that the current on the radiator at all frequencies is largely concentrated on the peripheral edge with very low current density approaching inward towards the center. For elliptic dipoles, one can effectively picture that numerous semi-elliptic thin-line dipoles of varying lengths are effectively formed to excite multi-linear modes hence resulting in a very wide bandwidth. To achieve the 3.42:1.00 UWB impedance bandwidth properties, low eccentricity elliptic dipole radiators with major diameter 2a = 19 mm and minor diameter 2b = 18 mm were etched on FR4 PCB with a thickness d = 0.762 mm and dielectric constant 4.2. With overall FR4 PCB size of 24 mm x 46 mm, this elliptic dipole provides suitable impedance properties and nearly omnidirectional patterns from lower 3.1 GHz to 10.6 GHz.

(a) (b)(a) Geometry of an elliptical printed-circuit dipole antenna, (b) Elliptical dipole antennas etched

on PCB with dielectric constant =4.2 (Right) and 10.2 (Left)

c) The improvement that have been made on the antenna.


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The printed-circuit board (PCB) antenna is useful for bandwidth covering from 3.1 GHz to 10.6 GHz ultra wideband (UWB). In addition, that was a spectrum with a swept frequency return loss of about 11dB. The radiation patterns on the x-y, y-z, and x-z planes of this elliptic dipole antenna were measured in an anechoic chamber at frequency of 3.0, 6.5, and 10.0 GHz as shown below. Results indicate reasonable omnidirectional radiation patterns on all the three planes. The consistency of the patterns can be observed across the frequency band, which is similar to a typical dipole radiation pattern.

(a) (b) (c)(a) Measured radiation pattern on x-y plane of the elliptic dipole etched on FR4 with = 4.2, (b) Measured radiation pattern on y-z plane of the elliptic dipole etched on FR4 with = 4.2, and (c)

Measured radiation pattern on x-z plane of the elliptic dipole etched on FR4 with = 4.2

d) The methods that have been used to achieve the improvement as in c).To achieve the 3.42:1.00 UWB impedance bandwidth properties, low eccentricity

elliptic dipole radiators with major diameter 2a = 19 mm and minor diameter 2b = 18 mm were etched on FR4 PCB with a thickness d = 0.762 mm and dielectric constant 4.2. Moreover, to reduce the size of the product, an elliptical dipole antenna of the same design is etched on a flexible laminate PCB with a thickness d = 0.635 mm and =10.2. With overall PCB size of 15 mm x 28 mm, this elliptic dipole provides suitable impedance properties across major portion of the frequency spectrum.

e) Conclusions.In conclusion, this antenna which using a single-feed network is very useful for UWB

application in the range of bandwidth from 3.1 GHz up to 10.6 GHz for both minor and major diameter. The starting operating frequency can be easy to locate by choosing the minor diameter which is about 0.34 times the guided wavelength as one of the advantages of this design.

Article 7: Low Cost UWB Printed Dipole Antenna with Filtering Feature

b) The antenna design and specifications.This paper introduces a new ultra-wideband (UWB) printed circular dipole antenna

having a filtering feature for rejecting the Wi-Fi band (4.9-5.9 GHz). UWB regulation in Europe and Japan require the rejection or the avoidance of the 5 GHz Wi-Fi frequency band, but due to the very wide frequency band used by UWB technology, it is also particularly exposed to other systems disturbances. Some experiments revealed problems of coexistence between UWB and the local wireless networks working in the WLAN bands. The proposed


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paper describes a Wi-Fi band rejection filter included in a previously developed compact UWB antenna. Constraints such as the size and the cost of the antenna are taken into account in the design. Efficiency measurements of the realized filtering small antenna, using Schantz’s method, are in conformance with simulations.

Figure 1: View UWB antenna Figure 2: View filter design

At the present time UWB approach is another way to create high data rate links between devices. Such standard is based on very low power level over very large bandwidth (3.1-10.6 GHz). Nevertheless, in the WLAN band between 4.9 and 5.9 GHz the level of EIRP must be very low (-70 dBm). This imposes to introduce filtering after or inside the antenna. Many solutions on frequency notched UWB antenna using the second approach with slots and/or arms in the antenna have been proposed, but such solutions have generally poor level of rejection and narrow bandwidth. A stripline band reject filter was introduced in the low part of the antenna allowing improved Wi-Fi band rejection. The stop band filter proposed is based on coupling open stubs and its form factor is imposed by the antenna shape.

c) The improvement that have been made on the antenna.d) The methods that have been used to achieve the improvement as in c).

The improvement that have been made and the methods that have been used to achieved the improvement.

No. The Improvement That Have BeenThe Methods That Have Been Used To

Achieve The Improvement1. Return loss

- A return loss become better (-8dB from 6.68 to 10.6 GHz) from the previous (-10dB over all the UWB bandwidth).

With the integrated filter that had been introduced in the feeding striped part of the antenna.

2. Frequency- The frequency is shifted from 100 to 200MHz.

By using the new value of permittivity and loss tangent

3. Efficiency By using the Schantz’s method (tha measurement conducted in metallic spehere) well suited for small antennas.By using an integrated filter.

e) Conclusions.The advantages of this stand alone design are cheap, very easy to implement for

classical mass production process and it allows simplification of the system for the DAA COMMUNICATION SYSTEM

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(Detection And Avoidance) implementation while ensuring an immunity of UWB devices against Wi-Fi systems.

Article 8: Modified Printed Dipole Antennas for Wireless Multi-Band Communication Devices


(i) (ii)

Figure i. Omni-directional Modified Dipole, 1. ML, 2. CSP, 3. Split Dipole (2 strips), 4. Short ML to CSP.

ii. Directional Modified Dipole, 1. ML 2. Directive Dipole 3. CSP balloon 4. Split Dipole 5. Ground Plane 6. Shorting of the Directive Dipole to the ground. 7. Shorting ML to CSP.

Modified Printed Dipole Omni-directional AntennaThe antenna structure consists of two conductive layers, first is the Micro-strip Line

(ML) and the second is the split dipole and Coplanar Strip (CPS) balloon line – with a shorting via at the end of the ML. Between the conductive layers there is a dielectric substrate with permittivity εr1. The overall dimensions of the antenna will depend on the ε r1 value, in the sense that the size will decrease with the increase of εr1.

Modified Printed Dipole Directional AntennaBy adding a third layer to the omni-directional antenna, we obtain a Modified

Directional Dipole Antenna as depicted in Figure ii. The goal, by adding the third layer, was both to reduce the influence of the human body (hand) and/or ground planes and to increase the gain. The geometric configuration consists of three conductive layers: first is the ML and the directive dipole, the second is the split dipole and the CPS balloon line with shorting via at the end of ML and, the third is the reflective ground plane. The directive dipole is shorted to ground through the shorting via. Between the first two layers the dielectric permittivity ε r1 is much higher than εr2 the dielectric permittivity between the second and the third layer. The height of the second layer h2 is twice the size of the first layer h1.

c) The improvement that have been made on the antenna.The improvement that had been made on the antenna is the combination of features of

two antenna types which is a Modified Printed Dipole Omni-directional Antenna and Modified Printed Dipole Directional Antenna.

d) The methods that have been used to achieve the improvement as in c).COMMUNICATION SYSTEM

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Modified Printed Dipole Omni-directional Antenna1. The geometric shape is obtained by splitting the classic dipole in 2 or more conductive

strips following the general printed dipole conditions, strip width less than 0.05 λo, and the total length less than 0.5 λo. The splitting will increase the total gain by reducing the surface wave loss and the loss in the conductive layer. On the other hand, the number and the shape of the conductive strips also affect the bandwidth of the antenna. A certain number of “via holes” (not shown in the figure) are added around the dipole.

2. The antenna feed is realized using a balloon from ML to coplanar strips CPS. The ML is connected to one strip of CSP via a conductive shorting pin at the end of the ML. In this arrangement the position of the shorting pin and the slot of CPS are very sensitive to the antenna performance related to the gain “distributions” in the frequency bands. The goal is to have approximately the same gain in all frequency bands.

Modified Printed Dipole Directional Antenna1. The geometric shape of the dipole, the inner layer, is obtained by splitting the classic

dipole in 2 or more conductive strips as described before. As described before, the number of slits and the depth of the slot will affect the bandwidth at high frequencies, while the length of the dipole will affect the lower frequency band.

2. The shape of the directive dipole, the upper layer, is a derived PEANO3 fractal shape; it increases the total gain by reducing the surface waves and the loss in the conductive layer. The number of conductive strips has effect on the high frequency bandwidth while the length of the dipole is sensitive to the lowest frequency band.

3. A number of via holes around the dipole (not shown in the figure) will increase the total gain by reducing the surface waves and radiation in the dielectric material.

e) Conclusions.Starting with known antenna geometry they had designed two antennas with enhanced

performance to be used in mobile multi-protocol wireless communication systems. This new better antenna is designed for multiple communication protocols and able to cover multiple frequency bands. This antenna also has to be as less disturbed as possible by the presence of the human body and ground planes.

Article 9: Wideband and Dual-Band Design of a Printed Dipole Antenna

The improvement is getting a larger bandwidth and dual-band capabilities. The dipole antenna also can work at the L-and S-bands. The printed dipole antenna is with integrated balun feed. In order to further get a larger bandwidth and dual-band capabilities of this antenna, some rectangle apertures are used and etched onto the surface of the printed dipole antenna, and it brings forth a good effect and achieves dual-band behavior. The dependence of VSWR on the sizes of the rectangle aperture is investigated.


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Dipole Antenna at front side

On the 36 mm x 18 mm rectangle metal coat, the big rectangle aperture is depicted with parameters of A and B , and the dimensions of the small rectangle aperture are depicted with a scaling factor, ∂=1/3. The whole rectangle metal coat is considered as a periodic cell. Three periodic cells are placed alone the dipole antenna arm, and four periodic cells are placed alone the long slot direction of the dipole antenna where the long slot is still reserved. By introducing some rectangle apertures onto the surface of the dipole antenna, the current distribution over the whole antenna surface is altered, and produced multi-resonance behavior.

A wideband and dual-band dipole antenna with an integrated balun feed is given. The antenna structure is optimized and a 41.5% bandwidth is obtained where voltage standing wave ratio (VSWR) is less than 2. Through investigating rectangle aperture with different sizes, a 47.8% bandwidth is obtained at L-band, and a 15.1% bandwidth comes true at S-band.

Figure 1: Model structure of dipole antenna

The initial model of the dipole is shown in Fig. 1. The radiation metal arm of the dipole antenna is etched onto a Teflon substrate with a thickness of 1 mm and a relative permittivity of 2.2. The arm length is designed at approximately λ0/2, , where λ0 is the free space wavelength corresponding to an operating frequency of 1.3 GHz, and width h1 = 18 mm. The height of the dipole antenna is 80.5 mm. A long slot is cut on the metal coat of the dipole antenna along z-direction with length h3 = 63.5 mm, and width w1 = 3 mm. The integrated transmission line (dashed line) used as matching balun is on the opposite side of the substrate, and takes h4 = 9 mm, h5 = 30 mm, h6 =32 mm, h7 = 41 mm, and d3 = 23.75 mm, respectively. The feed strip has a length of h4, and width w4 = 3 mm. The inclined strip has a vertical height of h5 with an angle φ of 72, and width w2 = 3 mm. The U-shaped strip is made up of three sections with lengths of h6, h7 and d3, respectively, and width w3 = 1.5 mm.


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Figure 2: Calculated and measured VSWRs Figure 3: Calculated VSWR of the optimized dipole antenna

Fig. 2 gives the plots of VSWR versus frequencies based on the initial design. At the same time, an approximate 35.3% bandwidth of VSWR is obtained, in which the center frequency, fc is defined as (fH + fL) /2, where fH and fL are the lower and higher frequencies with VSWR equal to 2.

Through investigating different aperture dimensions, different VSWR characteristics are obtained. In Fig. 5, the curves of VSWR versus frequencies are given when parameter A takes different values. It can be seen that the curves are moved toward lower frequencies with the increase in the size of A whereas, in Fig. 5(b), with the decrease in the size of A, the curves of VSWR become much flatter. Therefore appropriately choosing A can lower the resonant frequency and broaden the bandwidth.

The dipole antenna exhibits a wideband characteristic, which makes it a good candidate for emerging broadband wireless communication schemes. The novel dipole antenna is also tested at Land S-bands, and yields a bandwidth of about 600 and 480 MHz, respectively, which is very suitable for wireless applications requiring frequency agility technology.

Article 10: Design of a Dual Band Planar Dipole Antenna for WLAN Applications

In this article, a dipole antenna is designed to operate dual-band in the 2.4 and 5.2 GHz for WLAN applications. T-shape slit is embedded in the dipole antenna to achieve dual band operation and to avoid increasing the area of the antenna. A rectangular dipole antenna is demonstrated, where two embedded T-shape slits generate new resonant mode to achieve dual-band operation from 2.23 to 2.62 and 4.84 to 5.38 GHz for WLAN applications. The proposed antenna is fed with a 50 ohm mini coaxial line.

Figure 4: Proposed antenna WLAN geometry


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The configuration of the proposed antenna is shown on figure 4 with dimension of Wsub

= 7 mm, Lsub = 43.96 mm and H = 0.8 mm. the proposed dual-band dipole antenna is printed on FR4 substrate with a relative dielectric constant εr = 4.4 and a thickness H = 0.8 mm. the proposed antenna is fed in the middle of the structure and connected to a 50 ohm mini coaxial line. The basis of the antenna structure is two rectangular arms with dimension of W1 = 5 mm and L1 = 16.53 mm. the horizontal design, a T-shape slit, is embedded in each arm of rectangular dipole antenna to generate a new resonant mode at 5.2 GHz. Combining the 2.4 GHz band of the rectangular dipole antenna and the 5.2 GHz band newly generated meets the requirements of WLAN systems.

Figure 5: Measured radiation patterns in the y-z and x-z plane

The figured show the measured radiation patterns at 2.4 and 5.2 GHz in both the x-z and y-z planes. Since the feed lines is located parallel to the y-axis, the y-z plane radiation pattern has nulls in +y direction and –y direction. It is noted that the radiation pattern in the x-z plane of the antenna is with omni-directional radiation characteristics.

The development of antennas used on mobile communication devices is extremely important. The advantages of the printed dipole antenna are including low profile, light weight and low cost. Furthermore, it is very suitable for installation in notebook computers.

The antenna proposed for WLAN applications supports a dual band operation at 2.23 to 2.62 GHz and 4.84 to 5.38 GHz with good radiation characteristics in both operating. The proposed antenna has a simple structure, low profile and small dimensions. Therefore, it will be an attractive candidate for WLAN applications and is very suitable for installation in notebook computers, PDAs and other portable devices.


printed dipole antenna

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