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The aim of this study is to miniaturize an antenna using the magneto-electric dielectric materials. The size of an antenna can be reduced to half of the antenna by using the magneto dielectric material with high resonant frequency. Usually the size of the antenna is too large for DVB-H to be assembled in the mobile equipments. This is because of the reason that the quarter wavelength in vacuum is about 40cm for the VHF band. For this reason we have introduced the antenna of small size which consist of magneto-dielectric and meander conductive metal pattern layers whose permittivity and permeability is greater than the unity. However, only high permittivity materials were available to decrease the antenna size during the olden days. But the use of such material lead to the increased energy storage in the antenna near field which in turn reduces the antenna bandwidth. Now with the use of both permittivity and permeability the bandwidth can be increased as the energy storage is reduced.
Usually for VHF/UHF band antenna the resonant length of about 40cm is required in vacuum. But this condition is too large for the portable equipments particularly for the mobile equipments. It has to meet certain limit of miniaturization, even though the antenna size can be reduced by the conductive line design (helical coil). The resonant length is shortening by the dielectric material by √e, but when this e is greater there exist the bandwidth problem. For VHF/UHF band antenna the magneto dielectric materials have been employed whose permittivity and permeability is greater than unity and the low loss can shorten the resonant length by √µ * √e. However it has been proved that for the PIFA antenna, the arrangement of magneto dielectric parts show about 54% reductions in size for both experiment and the simulation. As mentioned above the magneto dielectric material has a huge advantage in reducing the size of the antenna.
The main objective of this independent study module is to reduce the size of the antenna using magneto dielectric material whose permittivity and permeability is greater than the unity. Let's check out how this works out and what we get from the results.
2. MAGNETO DIELECTRIC MATERIAL
For the increased bandwidth and simultaneous miniaturization new materials have been sought out. Let us now discuss about the newly introduced magneto dielectric in the design of a MDRA. Generally the size of the antenna can be determined by the wavelength
Where is the wavelength in free space and er is the relative permeability and µr is the relative permittivity. The use of both permittivity and permeability reduces the energy storage. As the energy storage is reduced the ability of the structure to radiate the power over a wider bandwidth is improved.
2.2 Usage of the magneto-dielectric material
There are several methods to reduce the size of the antenna. One of the popular methods is either done by altering the topology or altering the electromagnetic material. Let us now consider about the electro magnetic material. As described earlier the use of the dielectric with the permittivity makes the efficiency to be low. Hence it is suggested to use the magneto dielectric material.
In those magneto dielectric materials the permeability and the permittivity are the complex numbers which can be described by,
Are the dielectric and magnetic loss tangent.
The studies of the magneto dielectric material consist of some components that are metallic which makes the permeability to be changed so easily. But due to the presence of the ferrite component both the magnetic loss of the material and the dielectric are so high.
The miniaturization factor is given by
n = √µr.
this can be also defined as the refractive index.
If the dielectric (permeability equals to 1) is used, then the value of the permittivity is required at a very high value. This is because of the increase in the refractive index. Hence this makes the size of the antenna to be reduced enormously. The value of the permittivity and the permeability is selected accordingly such that the same value of the refractive index is obtained in case of the magneto dielectric substrate. Also the value of the permeability differs from certain unit in the dielectric which lead to certain merits.
Usually the consumers may expect that the device is provided with the size reduction which makes the antenna to be more simplicity and mobility. Hence the small size antenna is often paid more attention in the design of the antenna. There are several types of antenna like chip antenna, patch antenna, planar inverted f antenna. Such kind of antenna especially at low frequency range will have certain problems. Such kind of problems is as follows.
1. decreased efficiency or decreased radiation resistance.
2. The input impedance increases due to the increased reactance. The mismatch in the input impedance is obtained as the input resistance is too low. But generally this problem can be solved by adding the losses.
3. Reduction in the efficiency. The reason is obtained because of the trapped power in a limited space with a very high density.
4. Increased interaction with the surrounded environment.
Hence this problem can be solved with the use of magneto-dielectric materials.
2.3 Difference between the ordinary and the magneto-dielectric material
In the ordinary dielectric material, the intrinsic impedance of the dielectric is less than that of the intrinsic impedance of the dielectric in space. So if the value of the permeability and the permittivity equals to one there will be a impedance mismatch certainly and the surface wave appears that is diffracted.
In the electromagnetic material the intrinsic impedance in free space and the intrinsic impedance of the dielectric are equal, such that when the value of the permeability and the permittivity is equal to one the matching between the intrinsic impedance is obtained there by the surface wave disappears that makes the efficiency to be increased as consequence. Now the interaction of the environment is completely destroyed or eliminated. Hence many advantage are obtained by varying the permeability and the permittivity in the magneto dielectric material.
2.4 Reduction in size of the antenna using magnetic conductors
Generally the artificial magnetic conductors can be obtained by using a grounded dielectric slab which is loaded by the periodic patches. Usually the planar micro strip antenna is embedded in such kind of the surface. Eight by eight unit cells are employed in order to represent the artificial magnetic conductor surface. These unit cell size are depicted gradually. At 7.28GHZ the periodic structure is synthesized. This is done so in order to obtain a normal incidence at 7.28GHZ for the artificial magnetic conductors. The directivity and the return loss do not match with the magneto dielectric material. A maximum of 14.64dbi is obtained at 7.275GHZ and the height of the air gap is about 12.5mm. The frequency maximizes the directivity. The artificial magnetic conductors can reduce the size of the antenna only about 1.5 times. This is because of the finite number of the unit cell in the truncated periodic structure. Also the artificial magnetic conductor has a reflection coefficient that makes the angle dependency to be imperfect.
2.4.1 Reduction in size of the antenna using magneto dielectric material
When a magneto dielectric material is added in the antenna structure just beneath the permittivity substrate the values of the both permeability and the permittivity is assumed to be ten. And the thickness of the magneto dielectric material is about 1mm. the height of the air gap is deduced from 18.9mm to 8.9mm in order to get the resonance gain. This is done because of the reason that the wavelength is reduced in the magneto dielectric material. Generally the size of the antenna can be determined by its wavelength. The directivity can be reduced around 1db with respect to the conventional antenna in a magneto dielectric material. The reduction in the directivity is due to the enhancement of the effective permittivity of the whole structure under the substrate. The side lobe also disappears which is an tremendous property of the magneto dielectric material.
In general both the material was applied to reduce the size of the antenna for the planar antenna. But the artificial magnetic conductor, generally have a poor effect on the return loss which do not decrease the directivity of the antenna. Using the magneto dielectric material the directivity has been reduced significantly. Magneto dielectric material provides much wider bandwidth and it also eliminates the side lobes of the radiation pattern.
2.5 Fabrication and evaluation of the dielectric material
Some of the conductive pattern of developed antenna's are inverted f type with the, meander plane conductive pattern. Between the magneto dielectric material and the conductive pattern there is no non magnetic insulating layer. The sample of the antenna has a glass epoxy substrate or made up of ferrite resin composite substrate. Generally the conductive pattern was made by the copper that has been laminated on the glass epoxy substrate.
Let us now consider an antenna whose dimension are 26*12*0.7 mm^3. Generally the magneto dielectric material film was made by the spinal ferrite film which has been deposited on the copper. The conductive pattern of the copper was made by etching of copper which has been laminated on the glass epoxy substrate. All the epoxy layer of glass has been laminated by heat. The deposition of ferrite film on copper foil is about two to three micro meters. The properties of the magneto dielectric material had been obtained by its permeability and the permittivity. This magneto dielectric material has a permittivity of about 5.5 from 100MHZ to 10GHZ. Mean while the fr4 substrate has a permittivity of about 4.2 to 4.6 from 100MHZ to 10GHZ. Both the material has a permittivity smaller than 0.1. also the permeability was so low at a VHF band and at the loss tangent the material has about 0.3, also the level of magnetic loss for these composite material was small at the VHF band.
When using the magneto dielectric material substrate the antenna has its impedance matched at the feed point. For the fr4 substrate the frequency of the resonance was 619MHZ and the VSWR is about 1.4. But for the magneto dielectric substrate the antenna has its impedance matched at the feed point. For the magneto dielectric substrate the frequency of resonance was about 182MHZ and the VSWR is about 1.6, so it has been proved that the magneto dielectric material has 70.5% of resonance frequency lower than that of the fr4 substrate. The researchers have been proved that there is a shortening of wavelength caused by the magneto dielectric material.
2.5.1 Magneto-dielectric- the better substrates
Usually antennas on metal substrates will suffer from the bandwidth and the efficiency. This is due to the reason that the antenna current has a destructive coupled image. The radiation field when cancelled with the antenna results in a highly increased energy storage which results in a low efficiency and a narrow bandwidth.
In order to reduce the interaction with the environment, the reactive impedance have been employed. Let us now define about the re action. This phase is declared as a phase that is reacted in the electric field from the surface of the substrate, as it is illuminated with a plane wave incident. The increase in the bandwidth is obtained when there is a decrease in the interaction between the antenna current and its image. This also led to a good radiation efficiency. The equivalent circuit with the periodic surface can emulate the effect of the impedance surface that ahs been effective accordingly. The surface impedance in the conductor backed substrate which is the most commonly used structure. Since the reactive impedance surface has a conductor backed dielectric substrate its thickness must be at least a quarter wavelengths in the substrate, In order to observe the radiation from the antenna current image. But it results in a low permeability substrate as the thickness is impractical.
But the conductor backed magneto dielectric material can provide a moderate thickness with the reactive impedance characteristic. Even at a very low value of frequencies. Hence the permeability increases gradually as the surface impedance have been increased. Using the unit cell model several magneto dielectric materials have been employed. The unit cell model consists of four vertical walls. An air box was set up as the cell boundary has to be extending to the infinity with the substrate. On the substrate of the incident plane wave only the fundamental mode gets excited. In order to model the backing of the conductive substrate the bottom boundary was set up in order to get the perfect electric conductor boundary. When these phase increases with its bandwidth then the permeability also gets increased. But the permeability get decreases when there is a increase in the zero reaction phase. This phase acts like a magnetic conductor whose thickness h will be equal to its quarter wavelength. This phase will have a permittivity value which is equal to 4.4, where the permeability is varied from 1 to 13. The guided wavelength is same for the magneto dielectric material. For a wide range of frequency the antenna was supported by the magneto dielectric substrate. Hence it is concluded that because of the high reactive surface impedance the magneto dielectric material make better substrates for the planar antennas. The efficiency, bandwidth, and the gain are higher when using the magneto dielectric material.
2.5.1 Realization of the magneto dielectric material
In these type of material synthesis the permeability and the permittivity comes from the magnetic particles. The loss of the material is prevented by the insulating shell while improving its stability with the corresponding frequency. The nickel and the cobalt have a high and non dispersive dielectric constant of 1GHZ which has been provided by the chemical synthesis and the nanotechnology. When this nickel and the cobalt dispersed in a insulating matrix, the following methods are used. Some of them are- when the properties are stable with the frequency, loss in the eddy current as the size of the particle is smaller than the depth of the skin, higher permittivity from the inter facial polarization, magnetic anisotropy cancellation and low loss in the hysteric from the single crystal.
2.5.2 Characterization of the magneto dielectric material
To determine the frequency characteristic of the permeability and the permittivity magneto dielectric substrates are necessary. Let us consider two structures, in which one is sensitivity to the permeability and another one is sensitive to the permittivity. On thin film material these structure can be fabricated easily with the low cost.
The frequency characteristic of the magneto dielectric material is based on two types. One of method is corner probing of parallel plate and another method is the strip inductors. It has been proved that for the frequency dependent the characteristic of a thin film, the corner probing method is employed.
Let us now look at the extraction of the permittivity using the corner probe method. The structures consist of two metal layers which have printed on the top and the bottom of the material. Generally the top layer is framed with one more metal layer. There is a gap between the framing material and the top metal which is of 0.1mm, and the width of the framing is about 0.7mm. by the use of the corner probing the structure is excited in such a way that the ground tip lands on the frame and the signal tip lands on the top metal.
The frequency of response and the amplitude are very sensitive to the change of the permeability and the permittivity. The frequency of resonance of the impedance response can get an accurate characterization of the permittivity. But the parallel plate resonators are generally useful to a particular frequency range in the impedance response. The change in the permittivity makes the impedance response to be more sensitive due to the behaviour of the parallel plate resonator.
In the strip inductors structures with the inductive impedance response are useful to characterize the permeability and the parallel plate resonator characterize the relative permittivity. Strip inductors are used to characterize the permeability of the loss substrate. The strip inductors are similar to that of the parallel plate resonator in such a way that the relative permeability and the magnetic loss tangent used to fit the real and the imaginary part.
2.6 Magneto-dielectric Thin Film heterostructure
Thin film hetero structure provide a good opportunity to construct the new material with the unnatural response. They exhibit a very high permittivity and high permeability. The main objective of this material is the combination of permeability with the permittivity such that the wavelength and the characteristic impedance depends upon the both permittivity and the permeability with a magneto dielectric material.
As the ferro-magnetic are metallic the eddy currents become harmful at the high frequencies, while increasing its thickness hence it reduces the permeability there by increases the losses. The good solution for this is to laminate the frequency with a good standard di-electrics such a s silicon dioxide. Also the dielectric material show only a moderate permittivity that is less than 10. The permittivity gets higher when it is being crystallized. However those crystallization temperature are usually observed at 600 degree Celsius. But it is generally not compatible to be with the soft ferro magnetic material. However nowadays the crystallization temperature can be significantly reduced down to 400 degree Celsius.
Thus the goal is to realize a multi-alternation heterostructure. The material is grown by the physical vapour deposition on the thermally oxidized high resistivity silicon. After deposition those material is annealed at 300 degree Celsius in vacuum with 0.05T applied magnetic field. When it is highly saturated high permeability is obtained. The permeability spectrum of the unpatterned magneto dielectric hetero structure is shown in the diagram.
3. Various designs of the Antenna With Magneto dielectric Material
3.1 Monopole Antenna With MIMO Application
The latest trend in the wireless system is the reduction in size and the realization of the multi input and multi output system. In order to understand the downsizing of the antenna with a good characteristics like good impedance matching, broad bandwidth there are many methods to change the topology of an antenna. This can be achieved by the material called magneto dielectric material. By increasing the magnetic loss the magneto dielectric material has a tendency to lose its efficiency thereby obtaining a broader bandwidth because of the impedance matching. However the demerit in magneto dielectric material makes an advantage consequently in MIMO antenna as the isolation between the antenna has been gained by increasing the energy in the magneto dielectric material.
3.1.2 Design Of the Antenna
The dimension and its configuration of the monopole antenna with the magneto dielectric material is shown in the diagram. Here the metal of its ground plane only present at the front side. The antenna is fed by the coaxial line of fifty ohm in which the conductor which is inside is connected directly to the substrate of the feeding part. From the picture (b) the antenna has n-shaped strip metal which is supported by magneto dielectric substance. The radiating element is bent as shown in the diagram (c) according to the folded line in order to obtain a good matching of the impedance and miniaturization of the antenna.
SIDE AND TOP VIEW OF THE PROTOTYPE ANTENNA
THREE DIMENSIONAL VIEW
USE OF THE FOLDED LINE TO OBTAIN THE IMPEDANCE MATCHING
3.1.3 Measured characteristics of the dielectric material.
In a monopole antenna, Let us consider two magnetic dielectric material DM1 and DM2 whose permittivity and permeability varies accordingly. Let us discuss about it now. The dielectric material two is made up of polyolefin carrier resin and the dielectric material one is made up of ferrite powder. When these ferrite powder is added the magnetic loss increases gradually. The following diagram represents characteristic of the dielectric material. The difference between these two material is that in DM1 the impedance matching is good and DM2 has a poor impedance matching. And the gain differs for these two materials, at 3.8 GHZ the gain is 5.5db and 6.5db for DM1 and DM2 respectively. The compared resulted of these two dielectric materials have been tabulated below.
COMPARED RESULT OF THE MATERIAL
(a) complex permeability and (b) complex permittivity
3.1.4 Application of MIMO.
In order to decrease the mutual coupling between the two elements the dielectric material is used often. The performance of the MIMO with the magneto dielectric material been evaluated by its spatial correlation, mutual coupling, channel capacity, envelope correlation, diversity gain. It has been proved that mutual coupling and the correlation are lower and the diversity gain and the capacity are higher with the magneto dielectric material. Hence the performance is good when the dielectric material is used with the MIMO application. Hence with the use of the magneto dielectric material good impedance matching is obtained with a single radiating element. In a single element the antenna has reduced its size thereby obtaining the good impedance matching although the gain is smaller than that of the antenna with the application of the dielectric material. However in MIMO application the spatial correlation, mutual coupling, channel capacity, envelope correlation, and diversity gain are better than those of the antenna with the application of the dielectric material. In the single element, due to the increase in loss the gain is lower, however the use of magneto dielectric material with the MIMO is very helpful for the miniaturization of the antenna.
3.2 Meander Line antenna using magneto dielectric material
3.2 .1 Introduction
To obtain the broadband characteristic of the antenna the several techniques enhanced can be categorized into - use of lossy materials, impedance matching, use of multiple resonance. However the lossy materials are not used often as it limits the antenna efficiency.
3.2.2 Antenna design
Structure of the proposed broadband antenna
The meander line antenna is introduced to develop a broadband characteristic of the antenna with a small size. This can be done with accompanied magnetic material as the dielectric substrate. The omni directional pattern is obtained as the ground size is reduced. Here the antenna is edge fed. Initially a pure magnetic dielectric material (both permeability and permittivity is equal to the unity) is used to determine the broadband characteristic and optimize the dimension of the antenna.
3.2.3 Broadband Characteristics
The following diagram shows the return loss against permeability. Here the material which has µ = 5.5 shows the better performance in each band than the others.
RETURN LOSS AGAINST PERMEABILITY
However the performance of the antenna can be achieved still better by optimizing the dielectric constant. When varying the dielectric constant it is necessary to observe the broadband characteristic of the antenna. From the diagram it has been experimented that if the permeability is 3.5 the bandwidth is bigger. The diagram of the broadband antenna against the dielectric constant is shown.
RETURN LOSS AGAINST DIELECTRIC CONSTANT
3.3 Miniaturization of folded monopole antenna
The latest fashion in the handset unit employed in the mobile phones and the portable handy phone system(PHPS) is to decrease the size and the weight. Those antenna used for such a handset most follow the downsizing of handset unit and letting the performance of the antenna to be unchanged. In order to employ a low profile and small in size the built in folded monopole antenna have been introduced recently for the handsets. In analysis, this folded monopole antenna have been placed in a rectangular grounded plane that represent the shielding plate in the handset unit that is being used.
The folded monopole antenna operate at the quarter wavelength as it realizes the low profile and a small in size. It has been proved and confirmed that the folded monopole antenna are better than the planar inverted F- antenna. The physical volume has been miniaturize up to forty two (42%) percentage of the planar inverted F- antenna and the relative bandwidth is also sixteen (16%) percent as same as that of the planar inverted F- antenna.
3.4 Miniaturization of the handset antenna utilizing magnetic material
Antenna's used for the cellular phones must follow the downsizing of the handset. More over the built in antennas are nowadays becoming a intense requirement for the handset antenna's. By altering the antenna's configuration and its utilizing material rather than the conductor the antenna has been downsized. Because of the heavy loss frequency band the utilization of the magnetic material has been limited. But in the latest trend those utilization of the magnetic material are considered for the radio wave absorber as well as electro magnetic shield. Also for the high frequency band the magnetic material with the loss has been utilized in the recent years. In this topic we are analyzing and discussing about the downsizing technology of the antenna for the handset by using the magnetic material. A planar inverted f antenna is more popular built in antenna for the handset.
3.4.2 Structure of the PIFA antenna
The antenna employed here is the planar inverted f antenna which is the more popular built in antenna for the handset. This planar inverted f antenna usually operate at the frequency of 900MHZ. The antenna's dimension are 55*40*02 mm and its conducting box is 120*40*15 mm respectively. Here the operational frequency of the planar inverted f antenna depends on its surrounding length of the antenna element and its length is approximately λ divide by two where this λ is the operational frequency.
3.4.3 Characteristic of the antenna
Here the basic characteristic like the input impedance, radiation pattern and the current distribution are obtained. In the planar inverted f antenna the current is strongly flowed in the feed pin and the short pin respectively. In addition it has been proved that the enormous amount of the current has been flowed on the surface between the conducting box and the antenna element.
3.4.4 VSWR characteristic of PIFA with magnetic material
There are four kinds of magnetic material namely a) plane magnetic material, b) quarter plane magnetic material, c) fragment magnetic material and d) loop magnetic material. These magnetic material are arranged on the planar inverted f antenna and been analyzed. The current flows heavily and strongly on the arrangement of the magnetic material. Those utilized magnetic material has a loss tangent of 0.01 and its permeability is equal to 21 and the permittivity is equal to 2.5
Let us now analyze with the four kind of magnetic material such as plane magnetic material, quarter plane magnetic material, fragment magnetic material and loop magnetic material. The diagram shows the VSWR characteristic for the plane type of the magnetic material. The lowest point frequency of the VSWR is assumed to be the resonant frequency F0. The resonant frequency f0 is shifted by 30 MHZ to low as the planar material is arranged on the planar inverted f antenna surface, while it is shifted by 230 MHZ to low as these planar material is arranged on the reverse side of the planar inverted f antenna.
The VSWR characteristic for the quarter plane magnetic material is shown in the diagram. The quarter plane magnetic material is placed in four sides on the backside of the planar inverted f antenna. Here the resonant frequency shifts by 180 MHZ. As a result it is understood that it is more effective to order and arrange the magnetic material in the vicinity of the short pin and the feed pin.
The VSWR characteristic with the fragmental magnetic material is shown. Here the fragmental material is arrange din the vicinity of the short pin and the feed pin respectively. Here the resonant frequency shifts by 10 MHZ to low in the first case and the resonant frequency do not shift in the second case while in the third case the resonant frequency shift by 10 MHZ and in the fourth case the resonant frequency shift by 30 MHZ while in the fifth case the resonant frequency shift by 50 MHZ. As a output we understand that the resonant frequency shift to low as a fragmental material is arranged in the vicinity of the short pin. When the fragmental magnetic material is inserted in the feed pin the resonant frequency shift
to low, the bandwidth is about 10 MHZ for both of the calculation and the experiment. If it is short pin case the resonant frequency shift to low, the bandwidth is about 80 MHZ for the calculation and 90 MHZ for the experimental value. There fore it is clear that it is more effective to insert a fragmental magnetic material in the short pin.
However for the loop type of magnetic material the resonant frequency shift by 110 MHZ to low as this magnetic material is arranged in the backside of the planar inverted f antenna.
VSWR characteristic for the PIFA with loop type magnetic material
We have seen downsizing technique of the antenna for the handset by utilizing the magnetic material. The change of the resonant frequency of the planar inverted f antenna was examined by arranging the various types of magnetic material such as plane magnetic material, quarter plane magnetic material, fragment magnetic material and loop magnetic material. As a result it has been determined that fifty percent of the miniaturization of the planar inverted f antenna is possible at the resonant frequency of about 900 MHZ.
4. Effect of permittivity and permeability on bandwidth
In order to determine the effect of the permeability and the permittivity on the bandwidth a investigation is carried for the simulation. The optimal value that maximizes the bandwidth for the slot fed magneto dielectric resonant antenna was found. The improvement of the bandwidth can be obtained by the values of the permittivity and the permeability. The product of the permittivity and the permeability is kept constant at 25 such that the intrinsic impedance is varied accordingly. Also by varying the degree of matching the values of the permittivity and the permeability are adjusted accordingly. In order to achieve the -10 db match modifications are done such as by changing the length of the slot and the position of the magneto dielectric resonant antenna over the slot. It has been noticed that the optimal value for the magneto dielectric resonant antenna is achieved when the square root of the ratio of the permeability and the permittivity is equal to 1.74 such that the value of the permeability is equal to 8.62 and the value of the permittivity is equal to 2.9. so it is clearly demonstrated that the combination of the permittivity and the permeability will yield a efficient and significant bandwidth. By the use of high permittivity material alone makes the impedance matching to be poor and the usage of multi resonant structure becomes more complicated and becomes impossible sometimes. It has been proved that the use of high permittivity alone makes the coupling so poor to the parasitic elements and makes the simulation results to be narrower.
5. Multi resonant design for the increased bandwidth
By using the multi resonant design structure the bandwidth can be increased significantly. In order to double the available bandwidth it combines the dielectric resonant antenna and a slot antenna in particular. It has been noticed that that the dielectric structure and that of the resonance of the slot may be together and combined to get a hundred percentage of bandwidth improvement over which the polarization of the antenna and the radiation pattern are preserved. Using the dielectric material alone makes the bandwidth on the order of twenty five percent were demonstrated with the moderate miniaturization. The only disadvantage of using the slot to feed is that the multi resonant design antenna is back radiation. The slot dimension is necessary to merge with the resonance that may be large enough to allow the non negligible radiation below the ground plane. A probe feed can be used in certain cases where the isolation from lower half space is needed. Use of the probe feed makes the design of the circular polarization to be simpler and ease of implementation. But in general it is more difficult to use the feed probe. The merging resonance to augment bandwidth can be further extended to include the additional resonance from the parasitic element. This parasitic element may yield the third resonance at proper frequency if it is properly designed. For an instance in the original design an aperture is added to the next to the fed aperture in addition. In the multi resonant design antenna, through the electric field the two apertures are coupled as each producing the distinct resonance. All the three resonance will share the same polarization. The problem of the radiation has been exacerbates by the presence of the second aperture. A parasitic probe is added on the other side of the multi resonant design antenna alternatively. Opposite to the fed probe the parasitic probe is short circuited to the ground plane. To achieve more resonance parasitic probe is added in additional that will increase the bandwidth. This approach that is the multi resonance approach is used to design the circularly polarized antenna.
BROADBAND PATCH ANTENNA
The diagram shows the structure of the antenna which is done by using the air gap and fr4 substrate. The antenna which is on the air gap and fr4 substrate is in between those of the ground plane and fr4 substrate. The return loss of the antenna is about -23.32 db at 5.3 GHZ and it has a bandwidth of about 0.8 GHZ. The gain and the impedance are about 3.16 db and 46.26 + j 5.41 ohm at 5.43 GHZ respectively. Now let us compare the single magneto dielectric material and the double magneto dielectric material and the magnetic substrate with the air gap that will be compared with each other.
Let us now do with the single magneto dielectric substrate in which the entire antenna size is almost equals to the reference antenna. Since that permeability and the permittivity are together with the single magneto dielectric material, size reduction is possible. The size can be reduced significantly if the substrate is employed at the antenna design. The value of the permeability and the permittivity are varied. But the performance of the bandwidth, return loss, gain and the impedance are not good even if the single magneto dielectric is used. Because of the decrease in the efficiency, the bandwidth does not exist. The highest gain and the lowest gain will show the difference as -0.5db and -19.31db, also the impedance did not match by 39.41-j43.53 ohm. When the values of the permeability and the permittivity are five, seven and ten the antenna works like an magnetic antenna. The purpose of the low efficiency is because of the mismatch in the impedance and this mismatch in the impedance is caused when permittivity and the permeability employed together in the single substrate.
Let us now compare with the double substrate of the magneto dielectric material, between the ground plane and the dielectric substrate, the antenna with the magnetic substrate and dielectric substrate is obtained. In order to determine the relation about the thickness of the dielectric substrate the antenna with the magnetic substrate and dielectric substrate is obtained. In order to determine the relation about the thickness of the substrate like dielectric and magnetic substrate it is necessary to change the thickness of the dielectric substrate from 0mm to 5mm. The antenna can operate like a magnetic antenna when the permeability is too high. Hence the permeability and the permittivity are chosen by five. Due to this addition of the permeability the frequency of the resonance may have lower than that of the addition frequency. The frequency of resonance moved to the higher value as the dielectric substrate thickness becomes thick. There by it makes the effect of resonance to be weaker. It is due to the dispersion intensity of the permeability that becomes weak. At low efficiency the bandwidth do not exist at -10db. When the value of d is 1mm the return loss is about -6.64db at 3.25GHZ. Hence the impedance is mismatched by 16.44+j21.19 ohm. The higher gain and the lower gain are 2.51db and -0.1db.
Finally the antenna structure that has an magnetic substrate and the air gap are same. Also the reference antenna and the antenna size are equal in nature. On the air gap there is a antenna and the substrate of the magnet is in between the air gap and the ground. Now the value of the permeability is chosen by five because it has a tendency that the antenna operates like the magnetic antenna if the value of the permeability is too high. In order to find out the effect of the permeability about the bandwidth and the resonance frequency the air gap thickness is changed from 0mm to 5mm. Now the frequency of the resonance moves lower than the reference antenna because of the strong effect of permeability and permittivity that reduces the size of the antenna. Also the resonance that is dual becomes stronger. When the value of h is about 3mm, the antenna has a return loss of about -30.98 db at 4-95GHz and the bandwidth of about 2.5 GHz. Finally the gain is 2.35 db and the impedance matching is about 47.41+j0.94 ohm. So the theoretical operation of the magneto dielectric material was constructed for the stack and mixed structure. The single magneto dielectric substrate and the double magneto dielectric substrate have the advantage of miniaturizing the antenna size. On the other hand they exhibit a poor performance of the bandwidth and efficiency. So the combination of the magnetic substrate which is equal to five and the use of the air gap whose value is chosen at one makes the bandwidth broader and there by reduces the size.