Enhancement Cut off Frequency of Microstrip Low pass Chebyshev Filter using DGS

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.

Filter Design

5th order Chebyshev Low pass filter using Insertion loss method

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….

Simulated geometry of microstrip filter

Photograph of the fabricated filter

Simulation Results Simulated result of the filter without DGS

Simulation Resultscont….Simulated result of the filter with DGS

VNA result of the fabricated filter With DGS

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

[3] Liu, H., Z. Li, and X. Sun, “Compact defected ground structure in microstrip technology,” Electron. Lett., Vol. 41, No. 3, pp. 132–134, 2005.

[4] Mandal, M. K. and S. Sanyal, “A novel defected ground structure for planar circuits,” IEEE Microwave Compon. Lett., Vol. 16, No. 2, pp. 93–95, 2006.

[5] J.-S. Lim, C.-S. Kim, Y.-T. Lee, D. Ahn, and S. Nam, “Design of lowpass filters using defected ground structures and compensated microstrip line”, Electron Lett, Vol.38, pp. 1357–1358, 2002.

[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.