to Design and Analyse the Performance of Microstrip Ring Slot Antenna for 2.4GHz

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to Design and Analyse the Performance of Microstrip Ring Slot Antenna for 2.4GHz

Thamizhazhagi R1, Abirami D2, Sivasanthiya N3 1Assistant professor, 234Students (Bachelor of Technology), 1234Department of Electronics and Communication Engineering

Dr. S.J.S. Paul Memorial College of Engineering and Technology, Puducherry – 605 502, India

Abstract – A microstrip fed ring slot antenna is designed for 2.4GHz frequency range. To suppress the harmonics in the ring slot antenna inverted U-shaped slot is integrated into CRSA. By this, harmonic suppression over a wide bandwidth is achieved. This DGS can also be applied for the stacked annular ring microstrip-fed ring slot antennas.

Keywords: Circular ring slot antenna (CRSA), Defected ground structure (DGS).

1 INTRODUCTION

THE ADVANCED wireless communication systems require a compact and low-cost transmitter front end without sacrificing system performance. Crucial factors for wireless transmitters include efficiency, size, and bandwidth. Ways of achieving this are typically through high system integration and improved performance. However, this may cause increased electromagnetic interference (EMI) between transmitter subsystems. This paper presents new design techniques which specifically address these factors. These goals are accomplished through increased integration between the amplifier and antenna. In a conventional system, the antenna is typically designed separately and connected to the amplifier by an interconnect.

Additionally, when multiple systems operating at neighboring frequencies exist in close physical proximity, there is an increasing EMI problem. To remedy this, a filter is often placed between the amplifier and antenna to reduce unwanted radiation. Traditionally, these components are designed with 50- input and output impedance and connected together. This conventional method works well at low frequencies and when system design requirements are not tight. However, at high frequencies, interconnects become lossy and may possibly radiate or couple with other elements. . Many planar antennas such as the

microstrip patch or slot antenna can be designed for low input impedance and good radiation characteristics when operated near resonance. Therefore, the antenna and amplifier can be combined together with minimal matching circuitry in between. Perhaps the most crucial factor in power-amplifier design is increasing efficiency. Typically, most of the system power is consumed in the output power- amplifier stage. Since higher dc power adds to both system cost and weight, power-added efficiency (PAE) of the amplifier has to be maximized. Traditionally, this is done by using harmonic tuning, which reflects harmonic power back to the device [2]. Recently, biasing schemes have been reported for increasing PAE [3]. This technique optimized the power-supply voltage in accordance with the input signal level to reach maximum PAE. There are several techniques in harmonic tuning. Typically, higher order harmonics contain only a small amount of power. For this reason, practical designs usually terminate only second and third harmonics. Traditionally, tuning of the second harmonic is done by adding a quarter-wavelength (at the fundamental frequency) short-circuited stub at the output [4], [5]. Typically, this is most often placed at the drain bias line. At lower frequencies, this stub may use considerable circuit space. However, chip capacitors can also be used for rejection of the second harmonic if they have a self-resonance at the second harmonic [6]. Similar methods are used for tuning of the third harmonic. In this paper, we present several alternative methods for harmonic tuning. If designed properly, these methods offer a compact design. The first of these approaches is the active antenna approach. If the antenna input impedance is purely reactive (or zero)

at harmonic frequencies, it can be used to tune harmonics.

This has been demonstrated in [7]. In this case, tuning of the second harmonic with an integrated antenna was shown to increase the PAE by 7%. There are additional benefits to this approach. In addition to increased PAE or output power of the amplifier, a reduction of unwanted harmonic radiation that causes EMI and ultimately degrades system performance can be observed. The previously mentioned harmonic- tuning techniques are typically narrow-band. Some high-performance communication systems, for example those using multicarrier broadband code- division multiple-access communication (CDMA), require high-efficiency broad-band power amplifiers. Broadband harmonic tuning can be achieved using a microstrip filter based on the photonic bandgap (PBG) concept [8]. PBG is a periodic structure which prohibits wave propagation in certain frequency bands. Original PBG research was done in the optical region [9], but PBG properties are scalable and applicable to a wide range of frequencies. In the microwave region, PBG structures have been used in design of antennas [10], cavities [11], frequency- selective surfaces, and many other structures. In this paper, two-dimensional (2-D) structure based on etching a periodic 2-D pattern in the microstrip ground plane is used [12]. This structure has a stopband that is generally wider than can be achieved by using a single or double stub. This periodic structure is added between the antenna and amplifier. This configuration has an additional component, but can be used for broad-band operation. The analysis of active antenna amplifiers is quite challenging. Traditionally, nonlinear analysis such as harmonic balance is used to analyze power amplifiers. This kind of simulation cannot analyze antennas or PBG structures, in which a three-dimensional (3-D) full- wave solution of Maxwells equations is usually required. In this paper, the finite-difference time- domain (FDTD) technique is used because it can simulate arbitrary 3-D structures and provide broad- band frequency response with one simulation. FDTD results can then be incorporated into nonlinear circuit design to analyze the whole structure. The amplifier design examples consist of class-AB, class-B, and class-F amplifiers, which are prevalent at microwave

frequencies. However, with increasing device technology, other potentially higher efficiency types of amplifiers have been reported at microwave frequencies. Recently, a class-E amplifier has been realized at 1 GHz with 73% PAE and output power of

0.94 W [13]. In this case, approximate class-E operation is achieved by open circuiting the second harmonic only. More recently, a four-element integrated-antenna array with class-E performance was demonstrated at 5 GHz [14].

33 demonstrated with a PAE of 65%. These classes of amplifiers are also expected to benefit from the above techniques.

2. ANTENNA DESIGN

The antenna can be printed on an(60mm x 50mm x 0.8mm) FR4 substrate with a relative permittivity of

4.4 and loss tangent of 0.02 is depicted in fig. 1,and the corresponding photograph(both sides) is presented in Fig. 2. The proposed antenna is a combination of two simple structures, namely the microstrip-fed ring slot antenna. The main objective of this CRSA to induce a fundamental mode at approximately 2.4GHz band. Therefore, annular ring slot of inner radius

a1=10mm and outer radius a2=13.5mm were calculated according to the following.

VSWR

Ansoft Corporation

35.00

XY Plot 3

HFSSDesign1

Curve Info dB(VSWR(LumpPort1))

x +1

Setup1 : Sw eep1

30.00

(1 +2 )

2

dB(VSWR(LumpPort1))

dB(VSWR(LmpPort1))

25.00

Where c is the speed of the light in free space, and

(1 + 2) is the mean circumference of the ring slot antenna. However, the effects tuning various parameters such g and L will be discussed later.

Simulation based on high-frequency structure

20.00

15.00

10.00

1.00 1.50 2.00

Freq [GHz]

2.50 3.00 3.50

simulator(HFSS) was performed on CRSA. The CRSA can induce a fundamental mode(Mode 1)at exactly 2.45GHz,and other four modes were at approximately3.42GHz(Mode2),5.15GHz(Mode3),7.07

Radiation pattern

AnNsaomfteCor

poTrahteitoan

Ang

Mag

m1

0.0000

0.0000

3.1177

Radiation Pattern 1

0

HFSSDesign1

GHz

-90

-60

-30

m1 30

Curve Info

dB(GainPhi) Setup1 : LastAdaptive Freq='2.4GHz' Phi='0deg'

dB(GainTheta) Setup1 : LastAdaptive Freq='2.4GHz' Phi='0deg'

Curve Info

dB(GainPhi) Setup1 : LastAdaptive Freq='2.4GHz' Phi='0deg'

dB(GainTheta) Setup1 : LastAdaptive Freq='2.4GHz' Phi='0deg'

-2.00

-14.00

60

-26.00

-38.00

90

-120 120

-150

-180

150

.

III MEASURED RESULTS AND DISCUSSION

the simulated and measured return loss is of both CRSA and two results validated well with each other in both cases. Here the measured 10-dB impedance bandwidth of 2.4GHz.

S-Parameter

The measured radiation pattern in two principle planes namely the x-y and y-z planes, for both the antenna. The pattern measurement technique used a single axis rotational pattern that involves antenna under test(AUT) placed on a rotational positional.

During the process of measuring the antenna patterns the gain and efficiency were measured via the anechoic chamber. Here the antenna efficiency is defined as the ratio of total power radiated by an antenna to the net power accepted by the antenna from the connected transmitted which is expressed in this work. The efficiency of the proposed antenna is 79%.

IV STACKED ANNULAR RING

AnNsaomfteCorporaXtion Y

XY Plot 1

HFSSDesign1

m10.00 2.4000 -14.0866

dB(S(LumpPort1,LumpPort1))

dB(S(LumpPort1,LumpPort1))

-5.00

-10.00

Curve Info dB(S(LumpPort1,LumpPort1))

Setup1 : Sw eep1

-15.00

m1

1.00 1.50 2.00 2.50 3.00 3.50

Freq [GHz]

S-Parameter REFERENCES

Ansoft Corporation

0.00

XY Plot 1

Curve Info

HFSSDesign1

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    -4.00

    dB(S(LumpPort1,LumpPort1)) Setup1 : Sw eep1

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    dB(GainPhi) Setup1 : LastAdaptive Freq='2.4GHz' Phi='0deg'

    dB(GainTheta) Setup1 : LastAdaptive Freq='2.4GHz' Phi='0deg'

    Curve Info

    dB(GainPhi) Setup1 : LastAdaptive Freq='2.4GHz' Phi='0deg'

    dB(GainTheta) Setup1 : LastAdaptive Freq='2.4GHz' Phi='0deg'

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    poTrahteitoan

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    0.0000

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    AnNsaomfteCor

    poTrahteitoan

    Ang

    Mag

    m1

    0.0000

    0.0000

    3.9801

    Radiation Pattern 1

    0

    HFSSDesign1

    with defected ground structure for a microstrip patch

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    -26.00

    -38.00

    90

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    -120 120

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    V CONCLUSION

    By stacking the annular ring we improve radiation pattern and return loss. This can be used in Bluetooth and Wi-Max application

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