Circular Polarized Fractal Antenna

PRESENTED BY:-TILAK PATEL (140013111009)

GUIDED BY:-DR. P. R. PRAJAPATI

Introduction

CIRCULARLY POLARIZED (CP) ANTENNAS ARE A TYPE OF ANTENNA HAVING CIRCULAR POLARIZATION CHARACTERISTICS. BECAUSE OF THE ATTRACTIVE FEATURES OF CIRCULAR POLARIZATION

CP ANTENNAS HAVE SEVERAL IMPORTANT ADVANTAGES COMPARED TO LINEAR POLARIZED (LP) ANTENNAS.

FRACTALS ARE CLASSIFIED INTO TWO CATEGORIES: MASS AND BOUNDARY FRACTALS

MASS AND FRACTALS HAVE BEEN USED FOR THE REALIZATION OF MULTIBAND OR WIDEBAND OPERATION

Why there is need of fractal antenna??

Today’s wireless and satellite communication and advance military systems, required antennas of higher performance, higher gain, wider bandwidth, multiband support, low cost and conventionally smaller design dimensions. To fulfil all these requirements researchers looking for more advanced antenna designs. One such field of advanced antenna design is fractal antennas.

Fractal Boundary Generation Procedure

The generation procedure of design of Arc-slot fractal antenna is shown in fig 1

Step:1 As per frequency of interest, calculate the radius of the circular patch refer fig 1(a)

Step:2 Select a generator, which is an arc (e × d), refer Fig.2(a). Step:3 Divide the given circular patch into four quadrants, and

each quadrant is bisected at an angle a = 45 and arc slot is created with the help of generator, which results in iteration one fractal antenna as shown in Fig. 1(b). The arc slot dimensions for generation of the proposed antenna is demonstrated in Fig. 2(b) by taking only the first quadrant for an easy understanding

Step:4 Again choose Arc-slot size reduced by a scale of 50% to the previous one at an angle of reduced scale of 50% to the previous angle, i.e. we encounter two such locations in each quadrant to create slots

Step:5 Repeat step 4 to generate iteration 3 as shown in Fig.1(d). Here, in iteration 3 we encounter four locations in each quadrant to create slots

(a) Basic circular disc microstrip antenna (b) 1st iteration

(c) 2nd iteration (d) 3rd iteration

Fig. 1: Generation procedure of circular patch with Arc-slot fractal geometry.

(a) Arc-slot fractal generator

(b) Circular patch first quadrant

d

Fig.2 : Design geometry of circular patch arc-slot fractal geometry and its first quadrant demonstration in 3rd iteration, dimensions : a = 45 , b = a/2, c = a/4, r = 40 mm, d = 6.05 mm, e = f = d/2, g = e/2, h = d/4, I = e/4.

EXPERIMENTAL RESULTS AND DISCUSSIONS

A laboratory prototype structure was fabricated to validate the simulated results. The antenna was fitted with the standard 50Ω sub-miniature type-A (SMA) connector having a center pin diameter of 1.2 mm.

An anechoic chamber was used for measurement of the radiation properties of the fabricated antenna.

The measurement setup to measure return loss and radiation pattern are shown in Figs. 3(a) and 3(b) respectively.

(a) (b)

Fig.3: Measurement setup (a) return loss measurement with VNA, (b) AR measurement in the anechoic chamber.

The simulated and return loss and AR characteristics and simulated 3D far field radiation pattern are shown in Figs.4 and 5 respectively.

The minimum AR of 1.17 dB is achieved at 1.7 GHz. the return loss bandwidth of 38 MHz (1.68 - 1.718 GHz) and 3-dB

AR bandwidth of 7.9 MHz, ranging from 1.696-1.7039 GHz is obtained

Fig. 4: Simulated S11 and AR of the proposed antenna.

Fig. 5: Farfield radiation pattern of the proposed antenna.

The simulated and measured radiation patterns in the E and H-planes for left hand circular polarization (LHCP) are drawn Fig. 6.

The measured return loss and the AR characteristics is shown in Fig. 7.

The AR is 1.71 dB at 1.66 GHz with a bandwidth of 13 MHz and the impedance bandwidth is 40 MHz at center frequency 1.65 GHz obtained in measurement.

Fig. 6: Simulated and the measured radiation pattern of the proposed antenna at 1.7 GHz (Sim) and 1.657 GHz (Meas.) frequency.

Fig. 7: Measured return loss and AR of the proposed antenna

Application

Use in mobile communication Use in armature radio Use in military network Use in GPS System

CONCLUSION

It is observed that the simulated and measured results are nearly matching. The proposed antenna find applications in Mobile communication networks, Global Position System (GPS), military network systems like telemetry, and amateur radio, etc.

Reference

IEEE Research Paper “Realization of Circular Polarized Microstrip Antenna with Arc-Slot Fractal Geometry” By: (Dr. Pravin R. Prajapati.)

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