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Objective of the proposed work Methodology to Achieve the Objective Filter Designing Fabrication of Filter. Low pass filter with DGS Operational Mechanism Simulation & Measured Results Conclusion References. Outlines. Objective of the proposed work.

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Objective of the proposed work

Methodology to Achieve the Objective

Filter Designing

Fabrication of Filter

Low pass filter with DGS

Operational Mechanism

Simulation & Measured Results




Objective of the proposed work

To achieve 2.5GHz cut off frequency of microstrip low pass Chebyshev filter using DGS.

Top View

Bottom View

methodology to achieve the objective
Methodology To Achieve The Objective
  • Enhancement cut off frequency in the proposed filter is achieved by using defected ground structure.
  • DGS is using the structures etched in the microwave substrate ground plane. The DGS resonant characteristics are then used in filter design.
  • (a) Simulation cut off frequency 2.66 GHz

(b) VNA tested cut off frequency 2.715 GHz.

filter design
Filter Design

5th order Chebyshev Low pass filter using Insertion loss method

design specification
Design Specification

To design 5th order Chebyshev Low pass filter using Insertion loss method should be as follows


Rs = RL = 50Ω.

Cut-off frequency fc = 2.5GHz

Substrate used: GML 1000

Permittivity of substrate Єr = 3.2

Height h = 0.762mm


design specification1
Design Specification

Schematic of LPF filter


go = 1

g1 = 0.7563

g2 = 1.3049

g3 = 1.5773

g4 = 1.3049

g5 = 0.7563

g6 = 1

Step 1: – Prototype design:

design specification2
Design Specification

Step 2: – Impedance and frequency scaling:

For a new load impedance of Ro and cut-off frequency of ωo, the original resistance Rn ,inductance Ln and capacitance Cn are changed by the following formulae:

R= RoRn

L= (R0Ln)/ ωo

C= Cn/(Roωo)


Using the transformation with Ro = 50Ω and ωo = 2π(2.5X10 ) the new values are:

Rs = 50Ω

C1 = 1.1041pf

L2 = 4.7624nH

C3 = 2.3026pf

L4 = 4.7624nH

C5 = 1.1041pf

RL = 50Ω

design specification3
Design Specification

Step 3: Converting into distributed elements:

The relationship between inductance and capacitance to the transmission line length at the cutoff frequency ωc are

where n=1,3,5.

where n=2,4,6

  • L1 = 3.9596mm,L2 = 9.3392mm,L3 = 8.2577mm,L4 = 9.3392mm
  • L5 = 3.9596mm

w/d = 1.8322mm for z0 = 50Ω

w/d = 6.3574mm for z0 = 20Ω

w/d = .2940mm for z0 = 120Ω

fabrication of microstrip filter
Fabrication of microstrip filter

Photolithography steps

The pattern on the mask is transferred on the substrate by

means of photolithography

Step1. Clean the substrate, dry thoroughly in front of heat blower.

Step2. Coat the substrate with photo-resist material.

Step3. Preheat the substrate in oven at 98oC -100oC for 10 minutes.

Step4. Now aligned the mask on substrate

Step5. Exposed the substrate now to Ultra Violet rays for 2 minutes.

fabrication of microstrip filter cont
Fabrication of microstrip filtercont….

Step6. Keep the substrate in developer

Step7. Now keep the substrate in acetone and then dry in front of

heat blower

Step8. Apply dye on the substrate and then now posts heat the

substance for 10 minutes.

Step9. Protect the ground of substrate with tape.

Step10.Allow the substrate for Etching in the solution of FeCl3

and water, and get the desired pattern on the substrate


Simulated geometry of microstrip filter

Photograph of the fabricated filter

simulation results
Simulation Results

Simulated result of the filter without DGS

simulation results cont
Simulation Results cont….

Simulated result of the filter with DGS

final fabrication
Final Fabrication


Size of substrate =50.8 X 50.8mm2

Thickness of Substrate =0.762 mm

Dielectric constant of Substrate = 3.2

Width of the Microstrip patch (W)

W1 = 1.8322mm for z0 = 50Ω

W2 = .2940mm for z0 = 120Ω

Length of the Microstrip patch (L)

L1 = 3.9596mm,L2 = 9.3392mm,

L3 = 8.2577mm,L4 = 9.3392mm

L5 = 3.9596mm

Dimensions of the DGS slot = 5 x5 mm2

Ground plane dimensions = 50.80 x 50.80 mm2

Cut-off frequency fc = 2.715GHz

  • Design and fabrication of chebyshev low pass filetr is sucessfully done.
  • The method to calculate the cut off frequency of the LPF has been developed based on the modeled equivalent inductance and capacitance, which depends on the dimension of the DGS pattern. Due to presence of DGS in the implemented design, the cut off frequency is improved from 2.362GHz to 2.66GHz and finally 2.715GHz in the realized filter.
conclusion cont
Conclusion cont…..

The fabricated filter show good agreement between the simulated and measured result.

Compactness, easy fabrication and cost effective the proposed filter is useful for commercial wireless communication applications.



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