1 enhancement cut off frequency of microstrip low pass chebyshev filter using dgs
TRANSCRIPT
Outlines
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
To achieve 2.5GHz cut off frequency of
microstrip low pass Chebyshev filter using
DGS.
Objective of the proposed work
Top View Bottom View
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.
Design Specification
To design 5th order Chebyshev Low pass filter using Insertion loss method should be as follows
N=5 Rs = RL = 50Ω. Cut-off frequency fc = 2.5GHz Substrate used: GML 1000 Permittivity of substrate Єr = 3.2 Height h = 0.762mm Ripple=0.01dB
Design Specification Step 1: – Prototype design:
Schematic of LPF filterWhere:go = 1g1 = 0.7563g2 = 1.3049g3 = 1.5773g4 = 1.3049g5 = 0.7563g6 = 1
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/(Ro ωo)Using the transformation with Ro = 50Ω and ωo = 2π(2.5X10 ) the new values are:Rs = 50ΩC1 = 1.1041pfL2 = 4.7624nHC3 = 2.3026pfL4 = 4.7624nHC5 = 1.1041pfRL = 50Ω
9
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
L1 = 3.9596mm,L2 = 9.3392mm,L3 = 8.2577mm,L4 = 9.3392mmL5 = 3.9596mm
where n=1,3,5.
where n=2,4,6
w/d = 1.8322mm for z0 = 50Ω
w/d = 6.3574mm for z0 = 20Ω
w/d = .2940mm for z0 = 120Ω
llncn ZCl /
hhncn ZLl /
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
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 thesubstrate
Fabrication of microstrip filter cont….
Comparison Table of the simulated and tested result of defected ground structure
Simulated result of filter without DGS
Simulated cut off frequency with
DGS
VNA tested cut off frequency with
DGS
2.362 GHz 2.66 GHz 2.715 GHz
Final Fabrication Specification:Size of substrate =50.8 X 50.8mm2
Thickness of Substrate =0.762 mm Dielectric constant of Substrate = 3.2Width of the Microstrip patch (W)W1 = 1.8322mm for z0 = 50ΩW2 = .2940mm for z0 = 120ΩLength of the Microstrip patch (L)L1 = 3.9596mm,L2 = 9.3392mm,L3 = 8.2577mm,L4 = 9.3392mmL5 = 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
Conclusion
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…..
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.
[1] Ahn, D.; Park, J.-S.; Kim, C.-S.; Kim, J.; Qian, Y.; Itoh, T., "A design of the lowpass filter using the novel microstrip defected ground structure," Microwave Theory and Techniques, IEEE Trans. Vol.49, no.1, pp.86-93, Jan 2001.
[2] C. S. Kim, J. S. Park, D. Ahn, and J. B. Lim, “A novel 1-D periodic defected ground structure for planar circuits,” IEEE Microw. Wireless Compon. Lett., Vol. 10, no. 4, pp. 131–133, Apr. 2000
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[6] Karmakar, N.C.; Roy, S.M.; Balbin, I., "Quasi-static modeling of defected ground structure," Microwave Theory and Techniques, IEEE Transactions on , Vol.54, no.5, pp.2160-2168, May 2006.
[7] Easter, B., "The Equivalent Circuit of Some Microstrip Discontinuities," Microwave Theory and Techniques, IEEE Transactions on , Vol.23, no.8, pp. 655-660, Aug 1975.
References
References1.
[08] J.-S. Lim, C.-S. Kim, J.-S. Park, D. Ahn, and S. Nam, "Design of 10dB 90 branch line coupler using microstrip line with defected ground structure," IEEE Electronics Letters, vol. 36, no. 21, pp. 1784 1785, Oct. 2000. [09] J. S. Lim, J. S. Park, Y. T. Lee, D. Ahn, and S. Nam, “ Application of defected ground structure in reducing the size of amplifiers,” IEEE Microwave Wireless Compon. Lett., Vol. 12, pp. 261– 263, July 2002. [10] Lim J-S, Jeong Y-C, Ahn D, Lee Y-T, Cho H and Nam S, “Size-reduction and harmonic-rejection of microwave amplifier using spiral-defected ground structure,” European Microwave Conf., Vol 3, pp. 1421–4, 2003. [11] J. S. Lim, H. S. Kim, J. S. Park, D. Ahn, and S. Nam, “A power amplifier with efficiency improved using defected ground structure,” IEEE Microwave Wireless Compon. Lett., Vol. 11, pp. 170–172, Apr. 2001. [12] Ortega, A, de Menezes, Soares, L.R.A.X. and Abdalla,H., "Design of low-pass microstrip filters based on defected ground structure,”IEEEMicrowave & Optoelectronics Conference,pp.69,Oct.2011. [13]Pirani, Saeid, Nourinia, Javad, Ghobadi and Changiz, “Design of small modified microstrip lowpass filter with folded U-shaped defected ground structure”, ICEE, pp.108-111, 2010 [14]Kumar,A,Choudhari,N.P. and Verma,A.K., “Contest-k and m-derived composite lowpass filter using defected ground structure”, IEEE Advanced Computing & Communication Technologies, pp.454-456, 2012.