Seminar

report

Jadavpur university

Electronics and

telecommunication engg. dept.

MICROSTRIP

PATCH

ANTENNA

AND ITS

APPLICATION

-DEBDEEP SARKAR (000710701045)

And

MALOY GHOSH (000710701059)

Abstract

In this work we have discussed the various

aspects of Microstrip Patch Antenna. We have

presented the entire discussion in two parts, like

we did during the seminar. The first part deals with

the fundamentals of microstrip patch antenna, its

operating mechanism, design aspect, advantages

and disadvantages. In the second part we have

highlighted the various principles which can be

employed for performance enhancement of

microstrip patch antenna. We have highlighted

classical design techniques along with some novel

techniques employing metamaterials.

PART 1: FUNDAMENTALS

(click on the underlined text to jump to that portion)

1.History

2.Microstrip Antenna Structure

3.Radiation Mechanism

4.Different Components Of Microstrip Patch

Antenna

5.Analytic Models

6.Advantages And Disadvantages

7.Application

HISTORY OF MICROSTRIP ANTENNA

The rapid development of microstrip antenna technology began in the late 1970s. By the early 1980s basic microstrip antenna elements and arrays were fairly well established in terms of design and modelling, and workers were turning their attentions to improving antenna performance features (e.g. bandwidth), and to the increased application of the technology. One of these applications involved the use of microstrip antennas for integrated phased array systems, as the printed technology of microstrip antenna seemed perfectly suited to low-cost and high-density integration with active MIC or MMIC phase shifter and T/R circuitry. The group at the University of Massachusetts (Dan Schaubert, Bob Jackson, Sigfrid Yngvesson) had received an Air Force contract to study this problem, in terms of design tradeoffs for various integrated phased array architectures, as well as theoretical modelling of large printed phased array antennas. The straightforward approach of building an integrated millimetre wave array (or sub-array) using a single GaAs substrate layer had several drawbacks.

First, there is generally not enough space on a single layer to hold antenna elements, active phase shifter and amplifier circuitry, bias lines, and RF feed lines. Second, the high permittivity of a semiconductor substrate such as GaAs was a poor choice for antenna bandwidth, since the bandwidth of a microstrip antenna is best for low dielectric constant substrates. And if substrate thickness is increased in an attempt to improve bandwidth, spurious feed radiation increases and surface wave power increases.

This latter problem ultimately leads to scan blindness, whereby the antenna is unable to receive or transmit at a particular scan angle. Because of these and other issues, they were looking at the use of a variety of two or more layered substrates. One obvious possibility was to use two back to-back substrates with feed through pins. This would allow plenty of surface area, and had the critical advantage of allowing the use of GaAs (or similar) material for one substrate, with a low dielectric constant for the antenna elements. The main problem with this approach was that the large number of via holes presented fabrication problems in terms of yield and reliability. They had looked at the possibility of using a two sided-substrate with printed slot antennas fed with microstrip lines, but the bidirectionality of the radiating element was unacceptable. At some point in the summer of 1984 they arrived at the idea of combining these two geometries, using a slot or aperture to couple a microstrip feed line to a resonant microstrip patch antenna. After considering the application of small hole coupling theory to the fields of the microstrip line and the microstrip antenna, they designed a prototype element for testing. Their intuitive theory was very simple, but good enough to suggest that maximum coupling would occur when the feed line was centered across the aperture, with the aperture positioned below the center of the patch, and oriented to excite the magnetic field of the patch.

The first aperture coupled microstrip antenna was fabricated and tested by a graduate student, Allen Buck, on August 1, 1984, in the University of Massachusetts Antenna Lab. This antenna used 0.062” Duroid substrates with a circular coupling aperture, and operated at 2 GHz. As is the case with most original antenna developments, the prototype element was designed without any rigorous analysis or CAD - only an intuitive view of how the fields might possibly couple through a small aperture. They were pleasantly surprised to find that this first prototype worked almost perfectly – it was impedance matched, and the radiation patterns were good. Most importantly, the required coupling aperture was small enough so that the back radiation from the coupling aperture was much smaller than the forward radiation level.

(BACK TO PART 1 CONTENT)

STRUCTURE OF MICROSTRIP PATCH

ANTENNA Microstrip patch antenna has four structural components. They are

1. Ground plane 2. Dielectric substrate 3. Metal patch 4. Feed line

The top view and side view are shown below:

TOP VIEW SIDE VIEW

LEGENDS:

Ground plane

Dielectric substrate

Metal patch

Feed line

Thus the microstrip patch antenna is a metal deposition on a dielectric material

mounted on a electrical ground plane. A feed-line is used to feed the input power to

the radiating element i.e. patch.

(BACK TO PART 1 CONTENT)

RADIATION MECHANISM

The radiation mechanism of a microstrip patch can be understood by observing the

electric field distribution on the patch element.

Fringe electric field

The electric field lines just below the patch are completely perpendicular to the patch

surface and also completely enclosed by the dielectric substrate. But near the edges

the electric field starts to bend and there exists some fringe electric field which not

completely enclosed by the substrate rather some part of it exposed to free space.

These fringe fields can be modelled assuming the presence of slots near the edges

of the patch which causes the electric field to get out in free space. Thus these slots

act as radiators and the radiation principle is same as slot antenna.

(BACK TO PART 1 CONTENT)

DIFFERNT COMPONENTS

There are four components as already mentioned. Of these four three is to the

designers to choose. These three components are 1. Patch geometry 2. Dielectric

material 3. Different feeding techniques.

1. PATCH GEOMETRY: The geometry of the patch can be of many types for

example square, rectangle, circle, dipole etc.

The parameters to choose from these geometries are

a. Ease of Fabrication: this determines the cost of the device

b. Ease of Analysis: Different shapes lead to analysis in different co-

ordinate systems leading to several levels of numerical complexity

c. Space occupation: This factor determines the packing density of the

designs.

On these parameters microstrip dipole antenna stands out because of its lowest

space occupation and it also lays the foundation of microstrip dipole array which is

extensively used in many applicatons.

2. DIELECTRIC MATERIAL:

The dielectric substance can have relative permittivity of the range . But

lower means lower dielectric loss, higher power radiated to the space hence better

power gain and efficiency which are important performance metric of any antenna.

Whereas higher value of means higher loss and hence lower efficiency but due to

higher capacitance electric field lines are tightly coupled to the substrate, hence

extremely useful for MIC (Microwave Integrated circuit) operations where inter-

device coupling is a important metric.

But when we use any microstrip antenna it cannot be done without integrating with

some other integrated circuits, hence we need to reach a trade of between antenna

performance and the inter device coupling property and use that optimised value. A

value is normally used.

3. THE FEED LINE:

There are many available feeding techniques each having their own advantages and

disadvantages. They are discussed briefly below.

a. Microstrip Feed-line: It is a metallic patch on the dielectric substrate but

of very thin width. It is very easy to fabricate but has certain

disadvantages. However thin they may be in size ,they will be acting as

radiator themselves, and hence would cause spurious radiation and also

would decrease the gain and efficiency of the system.

b. Coaxial feed-line: The outer conductor of the coax cable is connected to

the ground plane and the inner conductor is fed through to the radiating

patch. At microwave frequencies the coax cables are almost lossless and

hence efficiency increases but this type of feeding gets extremely hard

when the height of the substrate is large because then the feeding of the

inner conductor gets tough.

c. Aperture feeding: This is a very important feeding scheme where we

have two separate antennas, both microstrip antenna, one acting as a

feeding element and the other as radiating element. They are connected

via the ground plane and coupled via a hole in the ground plane. Thus it

decouples the feeding and radiating circuits and hence allow us to

independently optimise them both which is extremely important in

microstrip antenna. The electrical properties can be controlled by

controlling the hole.

d. Proximity coupling: The patch is energised by some other source kept in

proximity of the patch.

Of these 4 methods aperture coupling is the most widely used feeding technique.

(BACK TO PART 1 CONTENT)

ANALYSIS METHODS

There are many methods to analyse micro-strip antenna. The most widely used are

1. transmission line model, 2. Cavity model 3. Full wave model. All these three

models often leads to strenuous mathematics which are beyond the scope of the

seminar. Hence we rather discuss them comparatively.

The transmission line model is the easiest of the three. It gives a good insight but is

less accurate. And modelling of coupling in this model is very hard.

Cavity model is a bit more accurate but it is more complex. Coupling modelling is not

that easy here.

The full wave model, in general, is most accurate, very versatile, can analyse single

element, finite and infinite arrays, stacked elements, arbitrary sized elements,

coupling etc. But it requires most complex models and also gives least insight of the

three.

(BACK TO PART 1 CONTENT)

ADVANTAGES AND DISADVANTAGES

The several advantages of the microstrip patch antenna are listed below:

1. It is just a metallic deposition on a dielectric substrate. Hence it has low

weight and low volume

2. By modern VLSI technology it can be fabricated at low cost and with high

packing density

3. It is mechanically very robust when mounted on rigid surface.

4. It has versatility in terms of polarisation. By intelligent choices of feeding

techniques it can support both linearly and circularly polarised waves.

5. It can easily be integrated with other MIC devices.

6. Its planar configuration makes it conformable to most device surface.

The disadvantages of the patch antenna are listed below:

1. Its bandwidth is very less

2. Its gain and power efficiency values are not great

3. Spurious radiation occurs from different junctions and feeds

4. It introduces surface wave with further reduces the power efficiency and also

introduces unwanted coupling

5. Power handling capacity of such a system is not much due to its small size

There are techniques to improve on these disadvantages. Those are discussed in

the part 2 of the report.

(BACK TO PART 1 CONTENT)

APPLICATION

Microstrip antennas are mostly used as receiving antenna of satellite

communication. Satellite transmitting antennas are separated from the earth plane

by a large distance of variable medium. Hence at the receiving end, the polarisation

cannot be predicted. Hence to ensure proper reception of incoming wave circularly

polarised antenna is a must. MPA s adaptability in terms of both circular and linear

polarisation makes it a prime candidate. Also considering the constraints of weight

and volume in any high end mobile devices its low weight and size makes it a

automatic choices. By modern techniques its other limitations are also overcome.

These are the reason of extensive usage of Microstrip antenna in modern day.

CONCLUSIONS:

Part 1 of the seminar was dedicated to the fundamentals of microstrip patch

antenna. The structure, the radiation mechanism, choices of different components

have been discussed in this part. Its several advantages and disadvantages have

been investigated. Also a specific example is taken up to stress its utility in present

day. Several modern techniques to improve the performance metrics will be

discussed in part 2 of the report.

PART-II: STATE OF THE ART RESEARCH ON

MICROSTRIP PATCH ANTENNA

A. Introduction:

The previous section of this report has already presented the basic radiation

mechanism, merits and demerits of Microstrip Patch Antenna, which can be called

MPA in abbreviated form. In this second part, the focus will be on methodology

which can be employed to enhance the performance of MPAs. We are going to

stress on classical microwave engineering techniques and unorthodox new methods

employing metamaterials for making MPA systems more efficient.

B. Review of Classical Methodology for Impedance Bandwidth

Enhancement of MPA:

As we know, any antenna is characterized by some typical performance metrics like:

gain, bandwidth (BW), radiation power efficiency, beamwidth, polarization, front-to-

back ratio etc. In case of MPA one major drawback is its low impedance bandwidth

(although its pattern bandwidth is high). For a single element MPA designed on thin

substrate and operating at the fundamental lowest mode, the typical BW is few

percents. People may argue that why should at all we try to increase the impedance

bandwidth? The answer is quite obvious. We know that MPA has huge application in

modern day wireless mobile communication due to its low cost, compactness and

conformability with VLSI based MMIC design. But today’s requirement is supporting

huge information bit-rate (3G applications), which needs use of UWB patch

antennas. Also there is necessity of tunable antennas having multiband

characteristics. This immediately puts pressure on the microwave engineers to

design more bandwidth efficient MPAs. There are lots of techniques which can be

employed for increasing the BW. We will highlight only a few of them.

The total quality factor of an MPA is dependent on the quality factors due to space

wave losses, conduction and ohmic losses, dielectric losses and surface waves. The

fractional BW of any MPA depends on the total quality factor. After some basic

mathematical steps and physical assumptions, it can be shown that [1] there is a

simplified mathematical relationship between bandwidth and effective permittivity of

the substrate used for MPA as:

eff

r

BW

1 (1)

Here eff

r is the effective dielectric constant of the MPA structure which can be

expressed as:

2

1

)12

1(2

1

2

1

W

hrreff

r

(2)

Here h and W are the height of substrate and patch width respectively; r is the

actual dielectric constant of the substrate. Equations 1 and 2 provide us two logically

obvious means of increasing BW.

As the first technique, we can consider increasing substrate height, since from

equation (2) we get that as h increases, effective permittivity decreases. Hence we

have increase in bandwidth. But this method has some inherent drawbacks because:

(i) Thicker substrate will support surface waves, which will deteriorate the radiation

patterns as well as reduce the radiation efficiency.

(ii) Serious issues with the standard coaxial feeding technique of the antenna will

arise.

(iii) Additionally, depending upon the feeding direction, higher order modes of

resonance will be generated, and this will introduce further distortions in the pattern

and impedance characteristics.

The second technique to increase bandwidth is decreasing the relative permittivity.

But we know that there are a number of trade-offs regarding the choice of dielectric

media as the substrate of MPA, so this method is not so advisable. But if we choose

the dielectric substrate of the antenna based on the constraints, which arise due to

fabrication of MPAs in particular MMICs (Microwave Monolithic Integrated Circuits),

we can play with the effective dielectric permittivity by designing an adjustable air

gap between the substrate and the ground plane []. For such applications the

antenna structure is made of two layers, including the substrate of thickness h and

an air region of thickness D. The effective permittivity is evidently reduced, tending

toward the free space value as the air thickness increases.

The third method regarding bandwidth enhancement is use of suitable impedance

matching networks over a wide bandwidth. Here we can make use of reactive

loading networks like tunable stubs. As we know, the MPA structure can be modelled

as a parallel resonant circuit with suitable L (inductance) and C (capacitance) values

depending on the choice of substrate material and the geometrical configuration.

Reactive loading allows us to change these parameters and allows the antenna to

couple its input power to the free space efficiently. Since L and C values are

changing, we can simultaneously tune the resonant frequency and the reflection

coefficient (S11) using the reactive loading method.

Now from the knowledge of transmission line theory we know that single stubs have

limited tuning range practically. That is why we resort to double stub tuning. The two

stubs are kept on opposite edges of the patch, in line with the coaxial feed point. The

patch is then tuned in an iterative manner by systematic trimming of either of the

stubs. It is observed from experimental study, that thin stubs allow very sensitive

tuning over a limited range, while wide stubs increase the range, but with less

sensitivity. This kind of arrangement is shown in the figure.

But these destructive iterative

trimming of stubs is not used now

a days. Currently research is

going on use of RF MEMS (Micro-

Electro-Mechanical Switches) for

designing reconfigurable antenna

using impedance matching

techniques []. The central idea of

this method is to place different

loads in the vicinity of the MPA

structure. Now MEMS switches

will be used to connect a variety

of load configurations to the main

antenna circuit. The selection of

switches can be done using electrical controls (applying piezoelectric properties).

Also there is scope for intelligent programmable switching control. Although

bandwidth might not be increased drastically, we can design multiband antennas in

this way.

The fourth technique that we are going to illustrate uses the mutual coupling

between various MPAs. We again emphasize that MPAs can be modelled as parallel

LC resonators, and the very basic knowledge of circuit theory tells us that interaction

between several such tank circuits can lead to multi-band operation. If the values of

geometrical design parameters are so chosen that the resonant frequencies of the

interacting antennas are placed quite near each other, then it can yield a wideband

configuration.

Now the question is how should we invoke the coupling between MPAs? A very

straightforward means can be to use antennas side by side just as in the Figure.

This figure shows the E-plane coupling between

two MPAs placed at a relative distance s. But this

type of arrangement would practically use up lots

of space. So we go for stacking of MPAs.

The next figure shows a typical stacked circular antenna constructed using two discs

etched on different boards. The lower disc is fed by a coaxial connector through the

ground plane. For such antennas, studies have shown the presence of two

resonances. The variable in our hand is the diameter of both the patches. It is

usually observed experimentally that the lower resonant frequency is relatively

steady over a range of different diameters for the upper conductor, whereas the

second resonance is highly dependent on those diameters [].

There are various applications of such stacked patch configuration in practical

circuits. One of such application shows the cross section of a typical RADAR module

using stacked patch antenna.

It is worth mentioning that, the concept of adjustable air-gap tuning also applies to

stacked patches, performing a tunable arrangement with two stacked discs. In this

case, the upper air gap has the effect of altering the resonant frequency of the upper

resonance, while the lower air gap has more complicated impacts. The air gap does

not affect the radiation fields significantly.

C. Use of Electromagnetic Band-gap Metamaterials for Suppression

of Surface Waves in MPA design:

All the classical design methods which we mentioned before neglected one

important point that there were no methods employed for surface wave suppression.

The surface waves are indeed the main hidden culprits, responsible for limiting

antenna gain, increasing the back-lobe and increasing the mutual coupling between

MPA. The last problem particularly becomes serious in MPA array design. Modern

day researchers decided to use metamaterials (MTMs) to combat the surface wave

issue.

Metamaterials are classically defined by Caloz et al as artificial periodic effectively

homogeneous electromagnetic structures that have unusual properties not readily

available in nature. The idea of MTM first originated in the classic paper by Victor

Veselago, way back in 1968, followed by works of Pendry and Ziolkowski. Although

their unorthodox theoretical properties fascinated people, the application of those

features in solving engineering problems was not possible till 2001, when 3D

volumetric MTMs were first fabricated in labs. Later on we got planar designs too.

Generally in microwave regime MTMs are of two types: one is the permittivity-

permeability based MTMs, namely ENG, MNG and DNG MTMs. Then we have the

Electromagnetic band-gap structures (EBG). The next part of our discussion deals

with the physics of using EBG MTMs to suppress surface waves.

EBG metamaterials are basically engineered surfaces formed using typical

microwave engineering components. The simplest example of a textured

electromagnetic surface is a metal slab with quarter-wavelength deep corrugations,

as shown in Figure. This is often described as a soft or hard surface depending on

the polarization and direction of propagation. It can be understood by considering the

corrugations as quarter-wavelength transmission lines, in which the short circuit at

the bottom of each groove is transformed into an open circuit at the top surface. This

provides a high-impedance boundary condition for electric fields polarized

perpendicular to the grooves and low impedance for parallel electric fields. Soft and

hard surfaces are used in various applications, such as manipulating the radiation

patterns of horn antennas or controlling the edge diffraction of reflectors. Two-

dimensional structures have also been built, such as shorted rectangular waveguide

arrays or the inverse structures, often known as pin-bed arrays. These textured

surfaces are typically one-quarter-wavelength thick in order to achieve a high-

impedance boundary condition.

But the above mentioned structures are not so compact so they cannot be used in

MPA regime. Recently, compact structures have been developed that can also alter

the electromagnetic boundary condition of a metal surface but which are much less

than one-quarter-wavelength thick. They are typically built as sub-wavelength

mushroom-shaped metal protrusions, as shown in Figure, or overlapping thumbtack-

like structures. One of such kind of structure is shown below:

The size-wise efficiency of such structures arises because they are sub-wavelength

in nature.

Now the first question is why should we call such periodic engineered surfaces as

electromagnetic band-gap ones? This point will be highlighted first. For that reason,

let us first briefly state some points regarding surface waves. Ordinary metals are

slightly inductive, due to the skin effect, so they support transverse magnetic (TM)

surface waves. At optical frequencies these are often called surface plasmons. At

microwave frequencies, they are simply the ordinary surface currents, very weakly

bound to the surface. A diagram of a TM surface wave is shown for the sake of

convenience. The wave-amplitude decays exponentially away from a surface with

decay constant α. It is also common practice to characterise any surface by its

surface impedance Zs.

While bare metals do not

support TE surface waves,

dielectric-coated metals can

support TE waves above a

cut-off frequency that depends

on the thickness and dielectric

constant of the layer.

Now the figure below is shown to illustrate the formation of effective L and C for an

engineered mushroom type geometry. The figure shows the side view of the

mushroom type EBG surface.

When the period of lattice formation is very small compared to the wavelength of

interest, we may analyze the material as an effective medium, with its surface

impedance defined by effective lumped-element circuit parameters that are

determined by the geometry of the surface texture. A wave impinging on the material

causes electric fields to span the narrow gaps between the neighbouring metal

patches, and this can be described as an effective sheet capacitance C. As currents

oscillate between the neighbouring patches, the conducting paths through the vias

and the ground plane provide a sheet inductance L. These form a parallel resonant

circuit that dictates the electromagnetic behaviour of the material, as shown in the

figure. Its surface impedance is given by the expression:

LC

LjZ s 21

(3)

This expression suggests that the mushroom-type surface lay-out provides a band-

stop nature on the surface. The resonant frequency is given by the well known

expression:

LC

10 (4)

Clearly, when the operating frequency is below the resonant frequency, the surface

offers inductive impedance, behaving as ordinary metals and supporting TM waves.

Above this resonant frequency, the surface has capacitive impedance and it

supports TE waves. But at the resonant frequency the surface has high value of

impedance; hence propagation of surface waves is inhibited. The band-gap for such

surface can be determined by considering its surface impedance versus frequency

plot.

Another important property of such surfaces is the fact that they provide a reflection

phase of 0 degree at some frequencies, if properly designed. This is in significant

contrast with the classical PECs (Perfect Electric Conductors) where the reflection

phase is always 180 degree. Hence such EBG surfaces are often called as PMCs

(Perfect Magnetic Conductors), and are used for directivity enhancement purposes,

but that is out of the scope of this discussion.

Now let us address the second basic question, that how to use these EBG surfaces

for enhancing radiation efficiency of MPAs? The idea is to properly design the EBG

structure so that the resonant frequency of the MPA falls inside the band-gap of the

EBG structure; hence the surface waves that could propagate along the substrate

will be forced to leave the substrate as leaky waves. The following design in inspired

by this methodology, where we have a centrally placed coax-probe-fed MPA

surrounded by suitable EBG structures. The idea of multiple stacking can also be

implemented here for improving space-efficiency.

The second point is to reduce mutual coupling between MPAs by preventing surface

waves. Mutual Coupling reduction by 10-20 dB using EBG structures in between has been

reported. This mutual coupling prevention design is potentially useful for a variety of

array applications.

Finally we should mention that, from a designer’s point-of-view static design like as

we mentioned before may not be suitable. But we have methods to tackle that issue.

A tunable impedance surface consists of a high-impedance surface in which

adjacent cells have been connected by varactor diodes, which have voltage-tunable

capacitance. The grounded and biased plates are arranged in a checkerboard

pattern as shown in the figure. Half of the vias are grounded, but the other half are

attached to a voltage control network on the back of the surface.

D. Future Directions Use of DNG metamaterials with negative

permittivity and negative permeability characteristics:

In this section we are going to introduce a new class of metamaterials (MTMs) which exhibit negative permittivity and permeability characteristics over a suitable frequency range. For defining such MTMs, we need to investigate about the properties which govern the electromagnetic response of any media in presence of any electromagnetic field. We describe these properties by defining the macroscopic

parameters permittivity and permeability of these materials. Let us construct the co-ordinate system (Fig.1) to get four major categories of materials: i) A medium with both permittivity and permeability greater than zero ( will be designated a double positive (DPS) medium. Example: Most naturally occurring media (e.g., dielectrics) fall under this designation.

ii) A medium with permittivity less than zero and permeability greater than zero ( will be designated an epsilon-negative (ENG) medium.

Example: In certain frequency regimes many plasmas exhibit this characteristic. Noble metals (e.g., silver, gold) behave in this manner in the infrared (IR) and visible frequency domains. iii) A medium with the permittivity greater than zero and permeability less than zero ( will be designated a mu-negative (MNG) medium. Example: In certain frequency regimes some gyrotropic materials, ferrites exhibit this characteristic. iv) A medium with both permittivity and permeability less than zero ( will be designated a DNG medium. To date, this class of materials has only been demonstrated with artificial constructs. It must be noted that artificial materials have been constructed that also have DPS, ENG, and MNG properties.

The above discussion can be summarized by the following diagram:

We have done some simulation study by applying a DNG metamaterial slab as

substrate below a standard microstrip patch antenna using FDTD (Finite Difference

Time Domain) method. The idea of using DNG media as substrate arises from the

fact that its negative permittivity and permeability characteristics can change the

reactive parameters of the MPA structure, enabling it to radiate over a wider

frequency range. The DNG media is modelled using a novel hybrid FDTD scheme,

which deals with the Drude model for complex permittivity behaviour using z-

transform technique and Lorentz model for complex permeability behaviour use ADE

(Auxiliary Differential Equation) method []. Such time-domain scheme is necessary

because they are more accurate compared to frequency domain software like HFSS

(High Frequency Structure Simulator). The detailed parameter listing is shown

below:

Parameter (FDTD+MPA) Value

∆x 0.389 mm

∆y 0.400 mm

∆z 0.265 mm

Mesh-size 60-by-110-by-14

∆t 0.441 ps

L 16 mm

W 12.45 mm

h_sub 0.795 mm

eps_sub 2.2 (Teflon)

Parameter (DNG) [from work of

Lubkowski et al]

Value

Electric plasma frequency 1.463 GHz

Electric Damping Frequency 30.69 GHz

Magnetic radial resonant frequency 9.67 GHz

Magnetic damping frequency 1.24 GHz

High frequency limit of permittivity 1.62

Low frequency limit of permeability 1.26

High frequency limit of permeability 1.12

The first curve is without the use of DNG media, the second one is after using DNG.

Initial studies reveal that use of such DNG media below a 6.4 GHz patch antenna

provides:

i) Increase in the resonant frequency;

ii) Huge improvement in -10 dB bandwidth;

But proper characterization and choice of DNG media and practical design aspects

are yet to be explored. After rigorous studies, the final results will be reported

elsewhere.

E. Conclusions:

This discussion had the main theme of reviewing the MPA performance

enhancement research techniques, along with throwing light on use of MTM

paradigm in this domain. It is quite sure that we will get newer effective methods for

improving MPA characteristics using MTMs through simulation and practical

fabrications.

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Wiley & Sons. Inc.

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