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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To achieve 2.5GHz cut off frequency of microstrip low pass Chebyshev filter using DGS.
(b) VNA tested cut off frequency 2.715 GHz.
5th order Chebyshev Low pass filter using Insertion loss method
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
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:
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:
L= (R0Ln)/ ωo
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
Step 3: Converting into distributed elements:
The relationship between inductance and capacitance to the transmission line length at the cutoff frequency ωc are
w/d = 1.8322mm for z0 = 50Ω
w/d = 6.3574mm for z0 = 20Ω
w/d = .2940mm for z0 = 120Ω
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.
Step6. Keep the substrate in developer
Step7. Now keep the substrate in acetone and then dry in front of
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
Photograph of the fabricated filter
Simulated result of the filter without DGS
Simulated result of the filter with DGS
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
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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