International Journal of Emerging Technologies and Engineering (IJETE)

Volume 1 Issue 4, May2014, ISSN 2348 – 8050

103

www.ijete.org

A Study of the Performance of a Stimulated Flame

Retardant-4 Based Microwave Photonic

Band Stop Filter

1Pooja Sahoo,

2P.K.Singhal

Madhav Institute of Technology & Science, Gwalior, India

Abstract—In this article, we explore the design,

computation, and simulated analysis of photonic Filter,

with a special emphasis on structures with Flame

Retardant-4 substrate that make a connection with

practically realizable systems. We analyze the periodic

dielectric structures that have a band gap for

propagation. The Photonic band gap of periodically

loaded air column on a dielectric substrate is simulated

using CST. For microstrip lines PBG structures offered a

wide stop band and the design equations presented can

precisely predict the bandwidth and the stop band Centre

frequency.

Index Terms— Photonic structure, FR-4 substrate, Band

gap filters, CST (Computer Simulation Technology)

software

I. INTRODUCTION

Filtering is one of the most important parts of

microwave circuit systems. Filters can be implemented

with shunt stubs or stepped impedance lines in a

microstrip circuit [1], but these techniques require large

circuit layout size and provide a narrow band and a

spurious pass band in stop band. Photonic bandgap

(PBG) structures have been considered as an alternate to

solve these problems in microwave circuit applications

[2]. Many researchers have proposed and demonstrated

several PBG structures for microstrip circuit application

with filtering characteristics. A serial connection of

several different PBG structures for wide rejection

bandwidth requires large size and had a limitation of

compactness in microstrip circuit applications [3].

One of the PBG structure used as filters are

demonstrated in Figure1 and that offers a wide

bandwidth in Figure 5. This forms a structure with more

flexibility, higher compactness, lower radiation loss, and

easier integration with the uni-planar circuits.

PBG structures in the ground plane of coplanar

waveguide can be implemented by etching holes in the

ground plane with an open connected with the gap

between strip line and ground plane [5]. At the resonant

frequencies of the periodic structure, there exists a stop

band for the transmission of microwave signals [6]. This

provides an effective methode to suppress higher order

harmonics in active circuits[6,7].

Figure.1. Circle shaped slots PBG in the ground plane

II. PBG UNIT CELL CONFIGURATION

Figure. 1 shows the proposed etched lattice for the

PBG circuit, which is located on the ground metallic

plane. The line width is chosen for the characteristic

impedance of 50Ω microstrip line [8]. Microstrip PBG

can be considered as a wide stop-band filter. For this

PBG design considered CST software [9]. This idea

could be extended to the ground plane of the microstrip

line allowing a periodic fluctuation in impedance and

thus restricting some frequencies in the pass band [10]. It

is the purpose of this work to analyze periodic structures

to determine effective and realizable uses for microwave

circuits and antennas [11].

Figure.2. Geometry 1-D PBG Cell

International Journal of Emerging Technologies and Engineering (IJETE)

Volume 1 Issue 4, May2014, ISSN 2348 – 8050

104

www.ijete.org

TABLE.I. CIRCUIT PARAMETERS FOR THE

PROPOSED PBG SECTION

Ground

plane

Dimension 150mm

x50mm

Height 0.038mm

Material PEC

PBG Cell

Dimension 20mm x

20mm

Inner circle

radius (R1)

8mm

Outer circle

radius (R2)

8.5mm

Substrate

Dielectric

constant ɛr

4.7

Material FR-4

Thickness 1.6mm

Microstrip

Design

Width 1.46mm

Length 150mm

Impedance 50Ω

Thickness 0.038mm

Material PEC

Figure.3.View of the proposed micro-strip line

This microstrip photonic structure can be analyzed like a

single-mode Bragg reflector or grating satisfying the

Bragg condition with guided wave number k in the

perturbed microstrip line and d the period of the

perturbation as

2d sin θ = n λ

When θ = 90ο and for the first mode

2d=n λ

2k= 2π/λ

And the guided wavelength λg is

λg =2d

The performance of this structure shows a deep and

broad rejected frequency band around the design

frequency.

III. RESULTS & DISCUSSION

Effect of Substrate Parameter on Band Gap

The substrate parameters like dielectric constant ɛr and

substrate thickness h influences the location, depth and

width of the stop band. the dielectric constant between

the etched and the un-etched portion of the substrate

should be in the ratio ≥ 2: 1. For this reason substrate

having dielectric constant ɛr ≥ 4, Variation with respect

to dielectric constant are shown in figure 4.

TABLE.II. SIMULATED -10 dB BANDWIDTH

VARIATION DUE TO DIELECTRIC CONSTANT Ɛr

FOR FR-4 SUBSTRATE, h=1.6

Dielectric

constant ɛr

4.7 8 12

Corner

frequencies(GHz)

2.94-

5.96

2.30-

4.79

1.89-

4.0

Cutoff

frequency(GHz)

4 3.12 2.406

Bandwidth(GHz) 3.02 2.49 2.1

Effect of the psition of the transmission line

The effect of the position of the transmission line with

respect to the PBG ground plane is studied. When the

transmission line was just above the center of PBG

structures in the ground plane, the S12 characteristics

showed reasonable width and depth in the stop band. As

the transmission line got shifted towards the Centre of

the PBG structure the stop band depth and width are

found to decreases as shown in Figure 5 & 6.

Effect of Number of Cells “n”

The depth of rejection in the transmission

characteristics is found to increase with number of cells

n as per figure 7. It is found that more than one cell is

needed in the ground plane of the microstrip line to

produce band gap for a given PBG structure.

TABLE.III. DEPTH OF REJECTION WITH NUMBER

OF CELLs ɛr= 4.7, h=1.6 mm, d= 20mm

Number of cells Rejection Depth

(Experimental)

1 -1.9011

4 -5.4740

12 -12.8442

24 -23.6565

Figure.4.Variation of cut off Frequency with different

Dielectric constant ɛr of FR-4 Substrate

International Journal of Emerging Technologies and Engineering (IJETE)

Volume 1 Issue 4, May2014, ISSN 2348 – 8050

105

www.ijete.org

Figure.5.Variation of S12 (dB) with Frequency for

different position of the transmission line for n=6

Figure.6.Variation of S11 (dB) with Frequency for

different position of the transmission line for n=6

Figure.7.Depth of rejection experimental with nunber of

cells

IV. CONCLUSION

In this paper the effect of PBG structures for band stop

filters is presented. For microstrip line PBG structure

offered a wide stop band and the design equations

presented can precisely predict the bandwidth and the

stop band center frequency. By reducing or eliminating

the effect of surface waves with photonic crystals, a

broadband response can be obtained In addition, it is also

proposed that the behavior of the photonic structure will

lead to improvements in radiation pattern and antenna

efficiency by the elimination of surface waves. In detail

For microstrip lines PBG structures offered a wide stop

band and Simulated values of cut-off frequency and -10

dB bandwidth are found to be in good agreement with

the predicted values and these results are tabulated in

table II.

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