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Design of Compact Microstrip Stepped-impedance Resonator Bandpass Filters
Available online at www.sciencedirect.com
Procedia Engineering 8 (2011) 30–35
2nd International Science, Social-Science, Engineering and Energy Conference 2010: Engineering Science and Management
Design of Compact Microstrip Stepped-impedance Resonator Bandpass Filters Ravee Phromloungsria*, Nopparat Thammawongsaa , Krissanapong Somsuka, and Pichai Arunvipasb a
Electronics Engineering Department, Faculty of Technology, Udonthani Rajabhat University (UDRU), UdonThani, 41000, Thailand b
Telecommunication Engineering Department, Mahanakorn University of Technology (MUT), Bangkok, 10530, Thailand
Elscvier use only: Received 15 November 2010; revised 15 December 2010; accepted 20 December 2010
Abstract
This paper presents the resonator bandpass filter design using the proposed stepped-impedance resonator technique. The proposed resonator is consisted of a quarter wavelength coupler with the stepped-impedance connected at the end of the lines. Each ports have a step impedance feed line to adjust the impedance of filter closed to the characteristic impedance Z0. This resonator can reduce the spurious response at 2f0 and 3f0. The experimental results and designs of all types are 0.9 GHz to implement bandpass filters. This filter can suppress the second and third spurious response that both the theoretical and experimental performance is presented. © PublishedbybyElsevier Elsevier Ltd. © 2011 2010 Published Ltd. Keywords: Stepped-impedance; Bandpass filter; Spurious response
1. Introduction Microstrip bandpass filters are widely used in modern communication systems to enhance the overall system performance due to its planar structure, ease of synthesis method, light weight and low cost [1]. The microstrip filter parameters can be derived by using both Chebyshev and Butterworth prototypes [2]. It is known that the traditional microstrip coupled lines filters are suffer from the spurious responses at 2f0. The even-mode and the odd-mode phase velocities for a microstrip coupled lines are unequal [3]. Because of it inherent structure, which is a nonhomogeneous medium, consisted of air above and dielectric below medium [4]. Many methods have been proposed
* Corresponding author. Tel.: +66-42-772-391; fax: +66-42-772-392 E-mail address: [email protected], [email protected]
1877–7058 © 2011 Published by Elsevier Ltd. doi:10.1016/j.proeng.2011.03.006
Ravee Phromloungsri et al. / Procedia Engineering 8 (2011) 30–35
31
stepped impedance resonators have been found advantageous in designing bandpass filters [8], [9]. To suppress or reject this spurious response, we introduce the resonator bandpass filter design using the stepped impedance resonators. The SIRs are well known and used to shift or suppress the higher order frequencies. The filter is synthesized based on a parallel-coupled structure. In this paper, we propose a new compact microstrip steppedimpedance resonator for bandpass filter, which has three types. In order to achieve compact circuit size and harmonics suppressed. This paper is organized as follows. Section II presents a comprehensive circuit theory, the proposed technique of the resonator bandpass filter based on the stepped-impedance. In section III, the fabricated resonator shows good bandpass performance. The experimental results are presented and agreed with the simulation results. The finally of this paper is a conclusions as section IV.
Fig 1. Equivalent circuits of a two-pole microstrip bandpass filter using the SIR (a) type1, (b) type2 and (c) type3.
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Ravee Phromloungsri et al. / Procedia Engineering 8 (2011) 30–35
frequency of passband is designed at f0 = 0.9 GHz. Schematic of the designed microstrip resonator of three types are shown in Fig.1. The resonator is designed and fabricated on the substrate of RF60 with parameters Fr 6.0 , G=0.002 , h =1.52 mm . The basically mainly consists of two SIRs. The length of each resonator is Ȝg/4. The input and output ports are the coupling lines with parallel of each resonator therefore the microstrip circuit must have the general layout shown in Fig. 1. This configuration of input and output port feeding causes the magnitude of input/output impedances pulled raise up. Therefore, step impedance transmission lines are employed both in input and output port to step down the port’s impedance close to the magnitude of characteristic impedance Z0. Fig.2 is the structure for the typical SIR. Each resonator has either a symmetric (even-mode) or an asymmetric (odd-mode) voltage distribution on the resonator. The conditions for the determining the resonance frequencies of SIR are given as [8] (1) tan T1 R cot T 2 (odd mod e) at f f1
cot T1
R cot T 2 (even mod e ) at f
f2
(2)
Where R is the impedance ratio of the SIR defined as
Z2 (3) Z1 Impedance ratio R is an important parameter in investigating SIR’s. The length of the type of SIR’s is presented R
by T A
T A 2(T1 T2 ) S / 2 (4) The resonator attains its maximum value when R t 1 and its minimum value when R 1 . The condition yielding a maximum and a minimum length [10] is as follows: T1 T 2 { T0 tan 1 R (5) When R=1, (T1 T2 ) S / 2 at f0, the resonator length is constant because the resonator is UIR. The resonance
frequencies of SIR can be turned by changing the value of R and the lengths of the high and low impedance-Z segments. When T1 T 2 { T0 , the fundamental resonance frequency is presented as f0 and the spurious frequencies of Og / 2 SIR ( f SN for N =1, 2, 3 ….) are defined by
f S1
S ª º 1» f 0 « 1 R ¼ ¬ tan f S1 2 f 0
(6) (7)
fS 2 f S 3 2 f S1 f 0
(8) In this way, the spurious resonance frequency can be controlled by changing the impedance ratio R. So that the spurious resonance frequency of SIR as a function of the impedance ration R has shown as Fig. 3.
Z1
Z2 T2
T1
Z2 T1
T2
Fig 2. Structure of stepped impedance.
33
Normalized spurious response
Ravee Phromloungsri et al. / Procedia Engineering 8 (2011) 30–35
fS 3 / f0 fS 2 / f0 f S1 / f 0
Impedance ratio R
Fig 3. Spurious response frequencies of the SIR. 3. Simulated and Experiment Results The simulated results are shown in Fig.4. The proposed bandpass filter’s insertion (S21) and return losses (S11) around f0 are about 1.86 dB and less than 20.1dB, while the suppression performances at 2f0, and 3f0 compare with the bandpass filter are approximately 64.1 dB ,and 52.3 dB for type I, 1.80 dB and less than 20.7dB, with 53.4 dB , and 54.6 dB suppression at 2f0, and 3f0 for type II, 1.78 dB and less than 20.8 dB, with 70.6 dB , and 54.5 dB suppression performances at 2f0, and 3f0 for type III. The measurement was performed with HP8720C Vector Network Analyzer calibrated from 0.1 to 3 GHz. Table 1 Parameter for Design Banpass Fillter. Techniques
Components
Proposed
Z0e = 70.27 : Z0o = 34.53 : .
Coupler’s length (T, rad)
W,S,L (mm)
0.50S
1.87, 0.30,37.0
Z stub 508 Rstub 30D
,
Impedance Stub
Wstub 2.25 mm, Lstub 13.36 mm WF 1 0.6 mm, LF 1 20.0 mm WF 2 1.2 mm, LF 2 20.0 mm
Feed Lines 0
0
S-parameters(dB)
-4
Type 1 Type 2 Type 3
-10 -20
-8 -12 -16 -20 0.86
S11
-30
0.90
0.94
-40 S21
-50 -60 -70 -80
0
0.5
1.0
1.5
2.0
2.5
3.0
Frequency(GHz)
Fig 4. The EM simulated results of a two-pole microstrip bandpass filter using the SIR (a) type1, (b) type2 and (c) type3.
34
Ravee Phromloungsri et al. / Procedia Engineering 8 (2011) 30–35
feed filter are shown in Fig. 5. The proposed bandpass filter’s insertion (S21) and return losses (S11) around f0 are about 1.85 dB and less than 17.6dB, while the suppression performances at 2f0, and 3f0 compare with the bandpass filter are approximately 65.3 dB ,and 35.6 dB for type I, 1.83 dB and less than 20.3dB, with 58.4 dB , and 26.7 dB suppression at 2f0, and 3f0 for type II, 1.79 dB and less than 26.8 dB, with 68.2 dB , and 50.2 dB suppression performances at 2f0, and 3f0 for type III, respectively. The photograph of the print circuit board of the resonator bandpass filter type I, type II and type III based on the stepped-impedance resonators have shown in Fig. 6. 0
Type 1 Type 2 Type 3
S-parameters(dB)
-10 -20
0 -10 -20 -30
S11
8.6
9.0
9.4
-30
S21
-40 -50 -60 -70 -80
0
0.5
1.0
1.5 2.0 Frequency(GHz)
2.5
3.0
Fig 5. The measured simulated results of a two-pole microstrip bandpass filter using the SIR (a) type1, (b) type2 and (c) type3.
Fig 6. Photographs of a two-pole microstrip bandpass filter using the SIR (a) type1, (b) type2 and (c) type3.
Ravee Phromloungsri et al. / Procedia Engineering 8 (2011) 30–35
35
In this paper, the simple design procedures for the resonator bandpass filter using proposed microstrip steppedimpedance resonator of type1 type2 and type3 are presented. By employing the square impedance located at the end of the parallel coupled line. These resonators give more efficiency of performance to reduce spurious response 2f0 and 3f0 by their structures. The closed form design equations of parallel coupled lines are suitable for using in many wireless and microwave applications. These bandpass filters are easy to design and construct. The proposed bandpass filter can be used in many wireless and microwave. Acknowledgment This work is financially supported by Udonthani Rajabhat University. References D.M. Pozar, Microwave Engineering, 2nd edition. New York: Wiley, chapter 8, 1998. R.K. Mongia, I.J. Bahl, P.Bhartia and J.Hong, RF and Microwave Coupled-Line Circuits, 2 nd edition. Artech house, 2007. [3] Wenzel, R.J. and W.G. Erlinger, “Problems in MicrostripFilter Design”, IEEE Int. Microwave Symp. Digest, pp. 203205,1981. [4] S. L. March, “Phase velocity compensation in parallel-coupled microstrip,” in IEEE MTT-S Int. Microw. Symp. Dig., Jun., pp.581-584, 1982. [5] I. J. Bahl, “Capacitively compensated performance parallel coupled microstrip filter”, IEEE MTT-S Digest, pp. 679-682, 1989. [6] J.-T. Kuo, S.-P. Chen, and M. Jiang, “Parallel-coupled-microstrip filers with over-coupled end stages for suppression of spurious responses”, IEEE Microwave Wireless Compon, Lett., vol. 13, pp. 440-442, 2003. [7] J.-T. Kuo, W.-H. Hsu, and W.-T. Huang, “Parallel coupled microstrip filters with suppression of harmonic response”. IEEE Microwave Wiresless Compon. Lett., vol. 12, pp. 383-385, 2002. [8] M. Makimoto and S. Yamashita, “Bandpass filters using parallel-coupled stripline stepped impedance resonators”. IEEE Trans. Microwave Theory Tech., vol. MTT-28, pp. 1413-1417, 1980. [9] M. Makimoto and S. Yamashita, Microwave Resonators and Filters for Wireless Communication-Theory and Design, Berlin, Germany: Springer, pp. 79-83,2001. [10] M. Makimoto and S. Yamashita, “Compact bandpass filters using stepped impedance resonators”, Proc. IEEE, vol. 67, pp.16-19, 1979. [1] [2]
Procedia Engineering 8 (2011) 30–35
2nd International Science, Social-Science, Engineering and Energy Conference 2010: Engineering Science and Management
Design of Compact Microstrip Stepped-impedance Resonator Bandpass Filters Ravee Phromloungsria*, Nopparat Thammawongsaa , Krissanapong Somsuka, and Pichai Arunvipasb a
Electronics Engineering Department, Faculty of Technology, Udonthani Rajabhat University (UDRU), UdonThani, 41000, Thailand b
Telecommunication Engineering Department, Mahanakorn University of Technology (MUT), Bangkok, 10530, Thailand
Elscvier use only: Received 15 November 2010; revised 15 December 2010; accepted 20 December 2010
Abstract
This paper presents the resonator bandpass filter design using the proposed stepped-impedance resonator technique. The proposed resonator is consisted of a quarter wavelength coupler with the stepped-impedance connected at the end of the lines. Each ports have a step impedance feed line to adjust the impedance of filter closed to the characteristic impedance Z0. This resonator can reduce the spurious response at 2f0 and 3f0. The experimental results and designs of all types are 0.9 GHz to implement bandpass filters. This filter can suppress the second and third spurious response that both the theoretical and experimental performance is presented. © PublishedbybyElsevier Elsevier Ltd. © 2011 2010 Published Ltd. Keywords: Stepped-impedance; Bandpass filter; Spurious response
1. Introduction Microstrip bandpass filters are widely used in modern communication systems to enhance the overall system performance due to its planar structure, ease of synthesis method, light weight and low cost [1]. The microstrip filter parameters can be derived by using both Chebyshev and Butterworth prototypes [2]. It is known that the traditional microstrip coupled lines filters are suffer from the spurious responses at 2f0. The even-mode and the odd-mode phase velocities for a microstrip coupled lines are unequal [3]. Because of it inherent structure, which is a nonhomogeneous medium, consisted of air above and dielectric below medium [4]. Many methods have been proposed
* Corresponding author. Tel.: +66-42-772-391; fax: +66-42-772-392 E-mail address: [email protected], [email protected]
1877–7058 © 2011 Published by Elsevier Ltd. doi:10.1016/j.proeng.2011.03.006
Ravee Phromloungsri et al. / Procedia Engineering 8 (2011) 30–35
31
stepped impedance resonators have been found advantageous in designing bandpass filters [8], [9]. To suppress or reject this spurious response, we introduce the resonator bandpass filter design using the stepped impedance resonators. The SIRs are well known and used to shift or suppress the higher order frequencies. The filter is synthesized based on a parallel-coupled structure. In this paper, we propose a new compact microstrip steppedimpedance resonator for bandpass filter, which has three types. In order to achieve compact circuit size and harmonics suppressed. This paper is organized as follows. Section II presents a comprehensive circuit theory, the proposed technique of the resonator bandpass filter based on the stepped-impedance. In section III, the fabricated resonator shows good bandpass performance. The experimental results are presented and agreed with the simulation results. The finally of this paper is a conclusions as section IV.
Fig 1. Equivalent circuits of a two-pole microstrip bandpass filter using the SIR (a) type1, (b) type2 and (c) type3.
32
Ravee Phromloungsri et al. / Procedia Engineering 8 (2011) 30–35
frequency of passband is designed at f0 = 0.9 GHz. Schematic of the designed microstrip resonator of three types are shown in Fig.1. The resonator is designed and fabricated on the substrate of RF60 with parameters Fr 6.0 , G=0.002 , h =1.52 mm . The basically mainly consists of two SIRs. The length of each resonator is Ȝg/4. The input and output ports are the coupling lines with parallel of each resonator therefore the microstrip circuit must have the general layout shown in Fig. 1. This configuration of input and output port feeding causes the magnitude of input/output impedances pulled raise up. Therefore, step impedance transmission lines are employed both in input and output port to step down the port’s impedance close to the magnitude of characteristic impedance Z0. Fig.2 is the structure for the typical SIR. Each resonator has either a symmetric (even-mode) or an asymmetric (odd-mode) voltage distribution on the resonator. The conditions for the determining the resonance frequencies of SIR are given as [8] (1) tan T1 R cot T 2 (odd mod e) at f f1
cot T1
R cot T 2 (even mod e ) at f
f2
(2)
Where R is the impedance ratio of the SIR defined as
Z2 (3) Z1 Impedance ratio R is an important parameter in investigating SIR’s. The length of the type of SIR’s is presented R
by T A
T A 2(T1 T2 ) S / 2 (4) The resonator attains its maximum value when R t 1 and its minimum value when R 1 . The condition yielding a maximum and a minimum length [10] is as follows: T1 T 2 { T0 tan 1 R (5) When R=1, (T1 T2 ) S / 2 at f0, the resonator length is constant because the resonator is UIR. The resonance
frequencies of SIR can be turned by changing the value of R and the lengths of the high and low impedance-Z segments. When T1 T 2 { T0 , the fundamental resonance frequency is presented as f0 and the spurious frequencies of Og / 2 SIR ( f SN for N =1, 2, 3 ….) are defined by
f S1
S ª º 1» f 0 « 1 R ¼ ¬ tan f S1 2 f 0
(6) (7)
fS 2 f S 3 2 f S1 f 0
(8) In this way, the spurious resonance frequency can be controlled by changing the impedance ratio R. So that the spurious resonance frequency of SIR as a function of the impedance ration R has shown as Fig. 3.
Z1
Z2 T2
T1
Z2 T1
T2
Fig 2. Structure of stepped impedance.
33
Normalized spurious response
Ravee Phromloungsri et al. / Procedia Engineering 8 (2011) 30–35
fS 3 / f0 fS 2 / f0 f S1 / f 0
Impedance ratio R
Fig 3. Spurious response frequencies of the SIR. 3. Simulated and Experiment Results The simulated results are shown in Fig.4. The proposed bandpass filter’s insertion (S21) and return losses (S11) around f0 are about 1.86 dB and less than 20.1dB, while the suppression performances at 2f0, and 3f0 compare with the bandpass filter are approximately 64.1 dB ,and 52.3 dB for type I, 1.80 dB and less than 20.7dB, with 53.4 dB , and 54.6 dB suppression at 2f0, and 3f0 for type II, 1.78 dB and less than 20.8 dB, with 70.6 dB , and 54.5 dB suppression performances at 2f0, and 3f0 for type III. The measurement was performed with HP8720C Vector Network Analyzer calibrated from 0.1 to 3 GHz. Table 1 Parameter for Design Banpass Fillter. Techniques
Components
Proposed
Z0e = 70.27 : Z0o = 34.53 : .
Coupler’s length (T, rad)
W,S,L (mm)
0.50S
1.87, 0.30,37.0
Z stub 508 Rstub 30D
,
Impedance Stub
Wstub 2.25 mm, Lstub 13.36 mm WF 1 0.6 mm, LF 1 20.0 mm WF 2 1.2 mm, LF 2 20.0 mm
Feed Lines 0
0
S-parameters(dB)
-4
Type 1 Type 2 Type 3
-10 -20
-8 -12 -16 -20 0.86
S11
-30
0.90
0.94
-40 S21
-50 -60 -70 -80
0
0.5
1.0
1.5
2.0
2.5
3.0
Frequency(GHz)
Fig 4. The EM simulated results of a two-pole microstrip bandpass filter using the SIR (a) type1, (b) type2 and (c) type3.
34
Ravee Phromloungsri et al. / Procedia Engineering 8 (2011) 30–35
feed filter are shown in Fig. 5. The proposed bandpass filter’s insertion (S21) and return losses (S11) around f0 are about 1.85 dB and less than 17.6dB, while the suppression performances at 2f0, and 3f0 compare with the bandpass filter are approximately 65.3 dB ,and 35.6 dB for type I, 1.83 dB and less than 20.3dB, with 58.4 dB , and 26.7 dB suppression at 2f0, and 3f0 for type II, 1.79 dB and less than 26.8 dB, with 68.2 dB , and 50.2 dB suppression performances at 2f0, and 3f0 for type III, respectively. The photograph of the print circuit board of the resonator bandpass filter type I, type II and type III based on the stepped-impedance resonators have shown in Fig. 6. 0
Type 1 Type 2 Type 3
S-parameters(dB)
-10 -20
0 -10 -20 -30
S11
8.6
9.0
9.4
-30
S21
-40 -50 -60 -70 -80
0
0.5
1.0
1.5 2.0 Frequency(GHz)
2.5
3.0
Fig 5. The measured simulated results of a two-pole microstrip bandpass filter using the SIR (a) type1, (b) type2 and (c) type3.
Fig 6. Photographs of a two-pole microstrip bandpass filter using the SIR (a) type1, (b) type2 and (c) type3.
Ravee Phromloungsri et al. / Procedia Engineering 8 (2011) 30–35
35
In this paper, the simple design procedures for the resonator bandpass filter using proposed microstrip steppedimpedance resonator of type1 type2 and type3 are presented. By employing the square impedance located at the end of the parallel coupled line. These resonators give more efficiency of performance to reduce spurious response 2f0 and 3f0 by their structures. The closed form design equations of parallel coupled lines are suitable for using in many wireless and microwave applications. These bandpass filters are easy to design and construct. The proposed bandpass filter can be used in many wireless and microwave. Acknowledgment This work is financially supported by Udonthani Rajabhat University. References D.M. Pozar, Microwave Engineering, 2nd edition. New York: Wiley, chapter 8, 1998. R.K. Mongia, I.J. Bahl, P.Bhartia and J.Hong, RF and Microwave Coupled-Line Circuits, 2 nd edition. Artech house, 2007. [3] Wenzel, R.J. and W.G. Erlinger, “Problems in MicrostripFilter Design”, IEEE Int. Microwave Symp. Digest, pp. 203205,1981. [4] S. L. March, “Phase velocity compensation in parallel-coupled microstrip,” in IEEE MTT-S Int. Microw. Symp. Dig., Jun., pp.581-584, 1982. [5] I. J. Bahl, “Capacitively compensated performance parallel coupled microstrip filter”, IEEE MTT-S Digest, pp. 679-682, 1989. [6] J.-T. Kuo, S.-P. Chen, and M. Jiang, “Parallel-coupled-microstrip filers with over-coupled end stages for suppression of spurious responses”, IEEE Microwave Wireless Compon, Lett., vol. 13, pp. 440-442, 2003. [7] J.-T. Kuo, W.-H. Hsu, and W.-T. Huang, “Parallel coupled microstrip filters with suppression of harmonic response”. IEEE Microwave Wiresless Compon. Lett., vol. 12, pp. 383-385, 2002. [8] M. Makimoto and S. Yamashita, “Bandpass filters using parallel-coupled stripline stepped impedance resonators”. IEEE Trans. Microwave Theory Tech., vol. MTT-28, pp. 1413-1417, 1980. [9] M. Makimoto and S. Yamashita, Microwave Resonators and Filters for Wireless Communication-Theory and Design, Berlin, Germany: Springer, pp. 79-83,2001. [10] M. Makimoto and S. Yamashita, “Compact bandpass filters using stepped impedance resonators”, Proc. IEEE, vol. 67, pp.16-19, 1979. [1] [2]