Design and Simulation of Stepped Impedance Microwave Low Pass Filter

Transcription

1 Design and Simulation of Stepped Impedance Microwave Low Pass Filter Neha V. Thigale B.Tech Dept. of Electronics and Telecommunication Dr. Babasaheb Ambedkar Technological University, Raigad (M. S.), India Chetan M. Vibhute B.Tech Dept. of Electronics and Telecommunication Dr. Babasaheb Ambedkar Technological University, Raigad (M. S.), India Pankaj S. Rathod B.Tech Dept. of Electronics and Telecommunication Dr. Babasaheb Ambedkar Technological University, Raigad (M. S.), India Aniket A. Jangam Prof. Dept. of Electronics and Telecommunication Dr. Babasaheb Ambedkar Technological University, Raigad (M. S.), India Abstract in this paper, a generalized Chebyshev Filter is designed. We have used the Stepped Impedance technology in this case. The 5 th order low pass filter designed has a cutoff frequency of 2.5 GHz implemented on FR4 epoxy substrate of εr = 4.4 with a thickness of 1.6mm. The filter has a minimum insertion loss of db and return loss of db. Keywords Microwave filter, stepped impedance, insertion loss and return loss. I. INTRODUCTION In wireless communication and radar systems, filters play a significant role. Filters are microwave devices which possess the properties of being a two-port network, reciprocal, passive and linear device. Basically microwave filters are nothing but designed using inductor and capacitors that is lumped element filter. These filters are not appropriate to be used at microwave frequencies. Lumped elements behave such as their size becomes comparable to wavelength. Thus each part of the circuit acts as an antenna and radiates which is undesirable. Hence these lumped elements are converted into transmission line parameters and can be thus physically realized. In this paper low pass filter with stepped impedance technology is designed at cutoff frequency of 2.5 GHz. The designed filter has been developed using HFSS software which works on Method Of Moments. This filter actually has a microstrip structure. II. Filter Design Steps A. Review Stage The first step includes selecting proper low pass prototype and later its microstrip realization that would correspond to its lumped element filter. Later response for the filter is chosen so as to obtain expected results as demanded by the customer. Among the three filter responses, Chebyshev response proves to be mostly recommended because of low insertion loss and equal ripples produced in the attenuation band as compared to the Butterworth Filter. The general schematic of stepped impedance low pass filter can be recognized as a LC ladder type filter as shown the figure below. In this paper 5 th order filter has been designed with the following specifications: Cutoff Frequency fc = 2.5 GHz Substrate thickness = 1.6mm Dielectric constant = 4.4 Pass band ripple = 0.1 db Lowest Line impedance Z0C = 20 Ω Characteristic impedance Z0 = 50 Ω Highest Line impedance Z0L = 120 Ω B. Circuit Realization The circuit of low pass filter consists of inductors and capacitors arranged in series and parallel respectively. This filter provides cutoff frequency at 2.5GHz with order as N=5. Table1: Values for Lumped Elements Component L1=L3 L2 C1=C2 Value 2.407nH 5.021nH 1.661pF E-ISSN : Page 78

2 These values are calculated with cut off frequency value to be 2.5 GHz. As this filter demonstrates Chebyshev E-ISSN : Page 79

3 Response, the values for inductor and capacitor can be calculated using the following expressions: Li = ( ) gi Ci = ( ) gi These values are needed to be converted into physical parameters i.e. in terms of length and width. To calculate the values of length for inductors and capacitors respectively, we have the following quations: For inductors: Ll = (λgl /2п) sin -1 (ωcl/ Z0L) For Capacitors: Lc = ( λgc /2п) sin -1 (ωcc/z0c) To calculate the values of length for inductors and capacitors respectively, we have the following equations: For inductors with (W/h) 2, W/h = 8e A / (e 2A -2) Where A = (Z0L /60) ) 0.5 ) { (0.11/εr ) } For capacitors with (W/h) 2, W/h = (2/п)[B 1 ln(2b 1 )+ ) {ln(b 1)+0.39 (0.61/εr)}] Where B = 377п/ 2Z0C (εr) 0.5 Thus we can summarize these calculated values in tabular form as below: Table2: Physical values for components Figure 2. Simulated Result for Return Loss For Stepped Impedance Low Pass Filter Sr. Impedance(Ω) Length(mm) Width(mm) No C. SIMULATION RESULTS We have designed the proposed Chebyshev response filter using HFSS The graph is plotted with frequency in GHz on X axis and values in db on Y axis. We have obtained the results for S(1,1) i.e. the reflection parameter and S(2,1) i.e. the insertion loss graph as shown below: Figure 3. Simulated Result For Insertion Loss For Stepped Impedance Low Pass Filter E-ISSN : Page 80

4 Figure 4. HFSS Design For The Proposed Filter E-ISSN : Page 81

5 Stepped Impedance Microstrip Low Pass Filter Using ADS Simulation Tool for Wireless Applications, International Journal of Scientific and Research Publications, Volume 3, Issue 8, August ISSN [8] Sarban Sen, Tamasi Moyra, Design of a Chebyshev Stripline based Lowpass Filter using Open Stubs and Defected Ground Structure (DGS), IEEE WiSPNET 2016 Conference. Figure 5. The physical realization of the filter III. RESULT From the graphs of these two parameters, it has been proved that the low frequency range up to the cutoff frequency is allowed to pass through the filter. Though our cutoff frequency was set to 2.5 GHz we have obtained the results at cutoff frequency as 2.48 GHz.The unwanted frequencies are thus rejected. This filter also shows 0 db reflection coefficient value i.e. S(1,1) for the unwanted frequencies. It shows stopband insertion loss to be dB and return loss of db. IV. CONCLUSION This low pass filter finds its applications in satellite, military, RADAR, test and measurement. Our main aim was to design low pass filter because this filter acts as a prototype and hence we can design other three types of filters by various transformations. ACKNOWLEDGEMENT We express our thanks to Dr. S.L.Nalbalwar Head, Electronics and Telecommunication Engineering Dept. of Dr. Babasaheb Ambedkar Technological University, Raigad for providing lab facilities and encouraging us to take this project so that we could reach towards its completion. We also thank Prof. S.V. Khobragade Sir and Mr. Tejkiran Patil for their help, support and guidance. REFERENCES [1] Pozar, David M. Microwave Engineering 2nd Edition, USA: John Wiley &Sons, Inc,1998. [2] Jia-Shen, Hong, G., & Lancaster, M. J., Microstrip Filters for RF/Microwave Applications. John Wiley & Sons Inc.,2001. [3] Garvansh, Abhay Singh Khushwaha, Navita Singh, Arun Kumar, Implementation of Stepped Impedance Low Pass Microstrip Line Filter for Wireless Communication, IJARCCE Trans, Vol. 3, Issue 7, July [4] Ralph Levy, Life Fellow, IEEE, Richard V. Snyder, Fellow, IEEE, and George Matthaei, Fellow, IEEE, Design Of Microwave Filters, IEEE Trans, Microwave Theory And Techniques, Vol. 50, No. 3, March 2002 [5] Manidipa Nath, Review of Filter Techniques, International Journal of Engineering Trends and Technology- Volume3Issue E-ISSN : Page 82

6 [6] Omid Borazjani and Arman Rezaee, Design, Simulation and Construction of a Low Pass Microwave Filters on the Micro Strip Transmission Line, International Journal of Computer Theory and Engineering Vol. 4, No. 5, October 2012 [7] K.Rajasekaran, J.Jayalakshmi, T.Jayasankar, Design and Analysis Of E-ISSN : Page 83