2013 First International Conference on Artificial Intelligence, Modelling & Simulation
Conversion of UHF Composite Low Pass Filter Into Microstrip Line Form
Liew Hui Fang Syed Idris Syed Hassan Mohd Fareq Abd. Malek School of Microelectronic School of Electrical System School of Electrical System Engineering Engineering Engineering Universiti Malaysia Perlis Universiti Malaysia Perlis Universiti Malaysia Perlis Pauh Putra Campus Pauh Putra Campus Pauh Putra Campus 02600 Arau, Perlis 02600 Arau, Perlis 02600 Arau, Perlis MALAYSIA MALAYSIA MALAYSIA Email:[email protected] Email: [email protected] Email: [email protected]
Yufridin Wahab Norshafinash Saudin School of Microelectronic Engineering School of Electrical System Engineering Universiti Malaysia Perlis Universiti Malaysia Perlis Pauh Putra Campus Pauh Putra Campus 02600 Arau, Perlis 02600 Arau, Perlis MALAYSIA MALAYSIA Email: [email protected] Email:[email protected]
Abstract— This paper presents the design of a compact, good selectivity near the passband since they have no composite, low-pass filter circuit into microstrip line form attenuation poles [2,9]. So, both types of low-pass filters using a new, transforming method. The composite, low-pass always have the problem of converting the lumped circuit filter operating in the UHF range were designed and prototype into microstrip when the order number, N, implemented on an FR4 substrate. The circuits were increases, making the circuit larger or more complex. simulated and developed using Advanced Design Software (ADS) for both lumped element and microstrip filters. A Elliptic–function filters have attenuation poles near their correction factor was considered due to fringing inductance passband, making them attractive for highly-selective and capacitance. The ADS simulation results showed that applications [2,4]. The disadvantages of elliptic design the response of the microstrip line circuit of the composite, and implantation are very complicated, and have a ripple low-pass filter with fringing correction factor was well at both in passband and stopband section as well. And the agreement with its lumped circuit. This showed that the new passband elliptic filter consists of highly non-linear transforming method enabled to the lumped element circuit response especially near with band-edge [2,8-9]. into a microstrip line to solve the complex design of The composite low-pass filter is less complex and composite filters. having a sharp roll –off. It was designed by applying the Keywords — microstrip line filter; constant-k filter; m- image parameter method [1-2]. The image parameter [6] derived; microwave communication; composite low pass filter was initiated by defining the image impendence and voltage function for arbitrary reciprocals of a two-port I. INTRODUCTION network because these designed results are required for the cutoff frequency and attenuation characteristics. Microstrip filters always find an important place in During the design of the composite, low-pass filter, two many RF microwave applications. They are most widely of the important factors that must be taken into preferred for selecting or confining the microwave signals consideration are the constant-k filter section and the m- within specified spectral ranges. The challenges on the derived section. microwave filters with requirements such as improved Ashwani Kumar etal [3,4] designed a microstrip line performance, miniature size, lighter weight, and lower composite filter using the defected ground structure(DGS) cost are ever increasing with the emerging applications of method .Its shunt connected series LC circuits are wireless communications. transformed with either quarter-wave short circuiting When the order of the filter increases, the method of stubs or quarter-wave open circuiting stub[4,7]. The calculating the dimensions becomes complicated, and it is performance of DGS composite filter was verified by adequate to specify that the response occurs at minimum comparing lumped elements, microstrip line and DGS stopband and passband attenuation. The most Butterworth measurement results. Overall, the result of DGS based and chebyshev require a high-order design to ensure a
978-1-4799-3251-1/13 $31.00 © 2013 IEEE 385391 DOI 10.1109/AIMS.2013.79 Matching High-f Matching low pass filter achieved good stability and more shaper Sharp section cutoff section cut off response than that of microstrip line and the DGS. cutoff It is also having large rejection bandwidth. The m=0.6 constant m- m=0.6 1 k derived 1 performances of composite filter are improved by using Z Zo o 2 T m<0.6 2 defected ground structure. But the disadvantages of DGS is complex circuitry, high power consumption and image Z Z frequency problems. ZiT iT iT Stephane Pinel etal [5] state the compact planar and Figure. 1. Block diagram of circuit components in the composite filter vialess composite filter are designed by using the image [1, 6] parameter method and semiconductor component approaches which operate at C-V band. The lumped A. Constant-k T-section element vialess composite filter are fabricated by using liquid crystal polymer substrate, which consists of The nominal characteristic impedance of constant–k characteristic low cost solution RF, high performance, section is made a constant value for the assigned ultra compact, and millimeter wave application. The frequency, which is given in [1, 2, 3]. overall folded layout of composite filter occupies an ultra The values of L and C for constant K can be calculated compact area and optimized by using full wave simulation by using the following formula. IE3D. The combination of stepped impedance filter and ZL /2 folded stepped impedance resonator performed by lumped co (1) elements schematic filter. And the measurement result exhibit rejection of attenuation pole which is greater than /2 ZC co (2) -40dB.The design was only present lumped element at final layout optimization. Fine tune was performed for the overall structure in order to miniaturize the circuit and L/2 L/2 to avoid the impact of excessive stub length [5]. Mostly all works showed that image parameter method using in designing of lumped elements of C composite filter have not been mentioned clearly the ways of transforming the circuit into mictrosip line. So, a new approach of transforming lumped circuit into microtsrip Figure 2. Low-pass, constant-k filter section in T-network [2] line is presented correction factor due to fringing is introducing so that accurate dimension can be determined An m-derived, low-pass, T-section is shown in Figure 3. without changing the properties of the composite filter. When a new simple and direct approach method is mL/2 mL/2 applied, it can solve the combination complexity of 4 important sections, that is constant-k, matching section, mC m-drive and bisected- π section, of transforming lumped 1 m2 elements. L 4m
HEORY OF OMPOSITE LOW PASS ILTER II. T C - F Figure 3. m-derived T-section [2] DESIGN The design of composite filter involved the input and The inductance and capacitance values can be calculated output impedance fixed as 50 ohm, and the required using [1, 2]. C" mC cutoff frequency response sets as 2.5GHz. The (3) development of composite low pass filter consideration the condition is compulsory to combining the constant-K 1 m2 in cascade and m-derived sharp roll off and matching L' L (4) section at input and output. Figure1show that the 4m important section combination of network constituted in Series component composite filter circuit. mL L" (5) 2 where L and C have the same values as the k-constant section.
386392 B. Matching Section
By combining in cascade, the constant–k section, the m-derived of sharp-cutoff section, and the m-derived matching section, we can produce a filter with the desired attenuation and matching properties. The sharp-cutoff section with m < 0.6 places an attenuation pole near the cutoff frequency to provide a sharp attenuation reaponse, and the constant-k section provides the high attenuation further into the stopbands. The bisected π- section with m=0.6 are palced at the ends of the filter to match the Figure 6. Model for series inductor with fringing capacitors Similarly the capacitance, C with fringing its inductance norminal source and load impendance, Zo, to the internal image impendance, , of the constant-K section and the is modeled as a T-network as shown in Fig. 7 m-derived section.The matching networks are using the m = 0.6 bisected –π section, as shown in Figure 4 [1-2].
mL/2 mL/2
mC/2 mC/2 Z Zo o 2 1 m L 1 m2 L 2m 2m Figure 7. Model for shunt capacitor with fringing inductors
For inductance, L, the length of the microstrip with Z iT characteristic impedance ZOL = 100 ohm can be calculated Figure 4. Bisected π- matching section [2] using Equation (6):
C L S III. MICROSTRIP LINE DESIGN TECHNIQUES d 1D T d L sin D T (6) 2 E Z U The microstrip inductor and capacitor always oL produce fringing, which must be taken into account and And its fringing capacitor can be calculated as: must be corrected. Four conditions have been studied i.e., C S 1 D d T C fL tanD T (7) 1) the filter is converted directly without correction, 2) the Z E U resonance LC circuit is achieved with a quarter wave stub oL d short to ground, and 3) the resonance LC circuit is For capacitor, C, the length of the microstrip with achieved with a quarter wave stub without ground.4) the characteristic impedance ZOC = 20 ohm can be calculated filter is converted directly with correction The typical using Equation (8): composite filter in lumped components is shown in Fig 5. d 1 d sin CZ (8) C 2 oC And the fringing inductance can be calculated as;
Z Cd S L oC tanD L T fC D T (9) E d U where
c (10) d f r Figure 5. Schematic diagram of composite filters and
To convert the filter into a microstrip line, first = wavelength the inductance L with its fringing capacitor is modeled as d a π-network, as shown in Figure.6 С =velocity of light -3.0e8
387393 = dielectric constants C C C CC - fl3 - fL5 - fL6 d = length of fringing capacitance n 44 C 2 2 2 (22) dL = length of fringing inductance
C fL = fringing capacitance Thus, the circuit with the new values is shown in Figure 9. The lengths of the microstrips for the inductor and the L fC = fringing inductance capacitor were calculated using Equations (6) and (8), respectively, based on these new values. The width of the microstrip line for the capacitor and inductor was calculated using the following formula (approximation): 377 Z o C w S (11) D n .1 57T r E h U
C 377 S w D .1 57Th (12) n D T E Z r U where Wn refers to W100 , W50 , W20, and Z refers to ZoL, Figure 8. Composite, low-pass filters after correction due to fringing Zo, and ZoC. where: L = fringing inductance due to capacitor C fc1 1 The complete microstrip line circuit design of the L = fringing inductance due to capacitor C fc2 2 composite filter using ADS without considers grounding C = fringing capacitance due to inductor L fL1 1 on stub is shown in Figure 10. CfL2 = fringing capacitance due to inductor L2 CfL3 = fringing capacitance due to inductor L3
By considering fringing, the new value of L1, L2, L3 , L4 , L5 , L6 , C1, C2 C3,C4 are: L L fC1 fC2 n LL 11 - - 2 2 (13) L L fC2 fC3 n LL 22 - - 2 2 (14) L L fC3 fC4 n LL 33 - - 2 2 (15) L L fC1 fC2 n LL 44 - - 2 2 (16) Figure 9. Composite low pass filter in microstrip line filter without L fC2 L fC3 L fC4 LL - - - grounding at circle part n 55 2 2 2 (17) The complete microstrip line circuit design of the L fC3 L fC4 composite filter using ADS by considering grounding LL - - n 66 2 stub is shown in Figure 11 as all simulation result analysis 2 (18)by using ADS include lumped elements and microstrip C fL1 C fL4 line composite filter. CC - - n 11 2 2 (19) IV. ADS RESULT AND SIMULATIONS C C C fL1 fL2 fL5 To verify whether this approach is satisfactory or not, n CC 22 - - - 2 2 2 (20) we simulated all four options of composite, low-pass filters. One is without correction factor with grounding C fL2 C fl3 C fL5 C fL6 CC - - - - and another one is without grounding with the cut-off n 33 frequency was set at 2.5 GHz on a substrate that had a 2 2 2 2 (21)
388394 m1 m2 dieletric constant of 4.5 and a thickness of 1.5 mm; the freq=1.073GHz freq=500.0MHz second was the microstrip with considering the fringing dB(S_50(1,1))=-12.676 dB(S_50(2,1))=-0.133 m2 m3 0 m3 correction factor for grounded stub and without ground. m1 freq=1.840GHz dB(S_50(2,1))=-2.930 All the results are given in Figure 11a to Figure 11e -20 m4 below. m4 freq=6.003GHz -40 dB(S_50(2,1))=-40.552 dB(S_50(1,1)) dB(S_50(2,1))
-60 0 12345678 freq, GHz
(c). Microstripline filter without correction but grounded stub
m1 freq=1.056GHz m2 dB(S_50(1,1))=-20.017 freq=500.0MHz m2 m3 dB(S_50(2,1))=-0.091 0 m3 -10 freq= 2.219GHz m1 dB(S_50(2,1))=-3.071 -20 m4 m4 -30 freq=6.009GHz dB(S_50(2,1))=-29.056 dB(S_50(1,1)) dB(S_50(2,1)) -40
-50 0 12345678 freq, GHz
(d). Microstripline filter with correction but without grounded stub
m1 m2 freq=1.040GHz freq=500.0MHz dB(S_50(1,1))=-20.282 m2 dB(S_50(2,1))=-0.091 Figure 10. Composite low pass filter in microstrip line filter with m3 0 m3 freq=2.214GHz grounding at circle part -10 m1 dB(S_50(2,1))=-3.021 -20 m4 m4 freq=6.002GHz -30 dB(S_50(2,1))=-28.730
m1 dB(S_50(1,1)) dB(S_50(2,1)) freq=1.405GHz m2 -40 dB(S(1,1))=-31.712 freq=500.0MHz -50 m2 m3 dB(S(2,1))=-6.260E-5 0 12345678 0 m1 m4 freq, GHz m3 -50 freq=2.472GHz dB(S(2,1))=-3.123 -100 (e). Microstripline filter with correction and with grounded stub m4 -150 freq=6.000GHz dB(S(1,1)) dB(S(2,1)) dB(S(2,1))=-39.799 Figure 11 Simulation results of ADS -200
-250 0 12345678 V. ANALYSIS AND DISCUSSION freq, GHz Overall Comparison between all the results are given in Table 1. The table show that the simulation results of (a).Lumped circuit filter circuit have good matching where the return loss is below -20dB and the 2fc attenuation frequency is seemed good m1 m2 freq=1.021GHz freq= 500.0MHz where the amplitude is fall below to -40dB. This means dB(S_50(1,1))=-13.464 dB(S_50(2,1))=-0.133 the attenuation are good enough to suppress the unwanted m2 m3 0 m3 m1 freq=1.845GHz frequency signal. dB(S_50(2,1))=-3.009 -20 (a) The comparison of the lumped-element and microstrip m4 freq=6.008GHz m4 dB(S_50(2,1))=-41.073 line circuits without fringing method (without grounding) -40 dB(S_50(1,1)) dB(S_50(2,1)) showed that the microstrip line circuit without fringing
-60 0 12345678 method (without grounding) for S11 return loss and -3 dB freq, GHz cut-off point were farther away from the design frequency and that, for S21, the insertion loss and the 2fc attenuation (b). Microstriple filter without correction and without grounded stub point were close to the lumped-element values. (b) The comparison between the lumped-element and the microstrip line circuit without fringing method (with grounding) showed that the microstrip line circuit without fringing method (with grounding) had a return loss of for S11 and a -3 dB cut-off point that were farther away from
389395 the design frequency and that, for S21, the insertion loss line, the parameter S11 return loss frequency was close to and the 2fc attenuation point were close to the lumped- that of the lumped-element approach with the microstrip element values. line without fringing method. Further work will be done to (c)The comparison between lumped element and fabricate the filters using micro-electro mechanical system microstrip line circuit with fringing method (without (MEMS) technology. The new approach is applicable for grounding), the result show that microstrip line circuit solving complex circuits for such composite filters, but it with fringing method (with grounding), for S11 point are also can be applied for other types of low-pass filters, such close to lumped element compare to design frequency but as Butterworth, Chebyshev, and elliptical, low-pass filters. getting more better than compare to microstrip line without fringing method, and for insertion loss, -3dB ACKNOWLEDGMENT cutoff and 2fc attenuation point are near with lumped The authors acknowledge University Malaysia element value. Perlis and the Malaysian Ministry of Higher Education (d)The comparison between lumped element and for providing the Fundamental Research Grant Scheme microstrip line circuit with fringing method (with (FRGS Grant No: 9011-00011), which made it possible to grounding), the result show that microstrip line circuit conduct and publish this research. without fringing method (with grounding), for S11 point are close to lumped element compare to design frequency REFERENCES but getting more better than compare to microstrip line without fringing method,, and for insertion loss, -3dB [1] Z.D. Tan, J.S. Mandeep, S.I.S. Hassan and M.F, (2007). Composite Low Pass Filter Design with T and π Network on cutoff and 2fc attenuation point are near with lumped Microstrip Line, Final Year Thesis, University Sains Malaysia, element value. Malaysia. [2] David M. Pozar (2005). Microwave Filters, In: Microwave nd TABLE I. Engineering,3 Edition, Ch. 8, Charity Robey and Susanne SIMULATION RESULT OF COMPOSITE FILTER IN ADS Dwyer, John Wiley & Sons, Inc., Canada. pp.371-396. [3] Ashwani Kumar, Nainu Priya Chaudhari, A.K. Verma, “Constant– Param Lumped Microstrip Microstrip Microstrip Microstrip element line line line with line with k and m-Derived Composite Low Pass Filter using Defected circuit without without fringing fringing Ground Structure,” IEEE Transactions Second International fringing fringing (without (with Conference on Advanced Computing & Communication (without (with grounding) grounding) Technologies,pp.454-456, 2012. grounding) grounding) S11-return -31.71dB -13.46dB -12.67dB -20.02dB -20.28dB [4] A.K. Verma and Ashwani Kumar, “Novel Design of Compact Low loss-20dB Pass Filter Using Defected Ground Structure”, International S21- 0dB -0.13dB -0.13dB -0.09dB -0.09dB Journal Microwave and Optical Technology, Vol 4, No. 5, pp. 276- insertion 282, September 2009. loss- 0.5GHz [5] Stephane Pinel, Ramanan Bairavasubramanian, Joy Laskar, and Cut off 2.47GHz 1.84GHz 1.84GHz 2.22GHz 2.21GHz John Papapolymerou, (2005). Compact Planar and Vialess Freq Composite Low-Pass Filters Using Folded Stepped-Impedance -3dB Resonator on Liquid-Crystal-Polymer Substrate. IEEE S21-2fc -39.80dB -41.16dB -40.55dB -29.06dB -28.73dB Transactions on Microwave Theory and Techniques, vol. 53, No. attenuatio n-6GHz 5, pp. 1707-1712. [6] M. Gil, J. Bonache, J. García-García, J. Marteland F. Martín, “Composite Right/Left Handed (CRLH) Metamaterial Transmission Lines Based on Complementary Split Rings Resonators (CSRRs) and Their Applications to Very Wide Band and Compact Filter Design,” IEEE Transactions Microwave VI. CONCLUSIONS Theory and Techniques, vol. 55, pp. 1296-1304, June 2007. Overall, the simulation results showed that the [7] J. Chen, Z.-B. Weng, Y.-C. Jiao, and F.-S. Zhang. (2007). “Low Pass Filter Design of Hilbert Curve Ring Defected Ground composite filter with fringing taking into consideration Structure,” Progress In Electromagnetics Research, PIER 70, without grounding give values closer to the designed pp.269–280, 2007. prototype than the filter without taking fringing into [8] Lin-Chuan Tsai and Ming-Lu Lee, “Design of Low-pass Filters consideration. The design of the -3 dB cut-off frequency of Using Three-and Two-section Stubs,” IEEE Conference on the lumped-element values fell at 2.472 GHz. The Electron Devices and Solid-State Circuits, pp. 729-732, 2007. [9] Navita Singh, Saurabh Dhiman,PrenaJain,Tanmay Bhardwaj simulation results of the lumped-element and microstrip “Design of Stepped Impedance Microstrip Line Low Pass Filter for filters were in good agreement with each other. However, Wireless Communication,” International Journal of Advances in the microstrip filter with the new approach with Computer Network and Its Security, pp. 215-217, 2009. fringing taking into consideration without grounding with a longer microtsrip line cut-off point was very close to 2.5 GHz, and the parameter S21 insertion loss was close to the value of the lumped-element approach. But, for the microstrip filter with the new approach with fringing taking into consideration with a longer microstrip
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