Compact Band-Pass and Band-Reject Microwave Filters Using Partial H-Plane Waveguide and Dielectric Layers

Transcription

1 Compat Band-Pass and Band-Rejet Mirowave Filters Using ial H-Plane Waveguide and Dieletri ayers A. Ghajar Department of Eletrial Engineering University of Guilan Rasht, Iran H. Ghorbaninejad-Foumani Department of Eletrial Engineering University of Guilan Rasht, Iran Reeived: May 14, 14-Aepted: Deember 8, 14 Abstrat In this paper, mirowave filters were designed using dieletri layers, whih were transversely loated inside a partial H-plane waveguide. The proposed struture an be used to design mirowave filters with arbitrary frequeny response inluding band-pass or band-rejet filters. Its longitude was redued by about 31% ompared with onventional partial H-plane band-pass filters. Sine the ross-setion of partial H-plane waveguide, in a determined frequeny range, is one quarter of the onventional waveguide, then the proposed filter has the ross-setion of one quarter ompared with the ounterpart E-plane waveguide filter. Besides ompatness, it is easy to fabriate, heap, mass produible, mehanially stable, and apable of sustaining high mirowave power and has very good adjustment to any arbitrary ideal filter. The proposed partial H-plane band-pass filter and its performane in terms of ompatness and adjustment to any arbitrary ideal filter were verified by designing and simulating three filters. Keywords-ial H-plane waveguide; ial H-plane filter; Band-pass E-plane filter; Compat mirowave filter; Bandpass mirowave filter. I. INTRODUCTION Mirowave filters have wide appliations in mirowave and ommuniation systems. Some inds of these filters inlude miro-strip filters [1, ], substrate integrated waveguides (SIWs) [3], dieletri resonator (DR) filters [4, 5], waveguide filters filled with dieletri layers [6, 7], and waveguide filters filled with dieletri and magneti layers [8] whih are multi-layer longitudinally inhomogeneous waveguide (IW) [9, 1]. w, restrition in terms of size and weight of mirowave omponents is a momentous onsideration. In fat, in many appliations, the total size of filter is redued. There are always the hallenges of size redution and many methods have been proposed for ompat mirowave omponents. Sine many mirowave filters ontain transmission line setions, some efforts have been made to redue the length of transmission lines suh as using DGS [11], fratal line [1], stepped stubs [13], and non-uniform transmission line [14]. Cut off frequeny has an inverse relation to the dimension of waveguide so that inreasing ut off frequeny leads to size redution [15]. Thus, some hanges should be made to design a filter with suitable size, whih wors at lower frequeny. Three types of band-pass filters using a new type of ompat waveguide, namely partial H-plane waveguide, have been presented [16]. It has been shown that the ross-

2 setion of partial H-plane waveguide is one quarter of that of the onventional retangular waveguide [17]. In this paper, using partial H-plane waveguide, in whih several dieletri layers are inserted, a new type of ompat band-pass mirowave filter was proposed. The proposed struture did not employ indutive elements suh as diaphragm, rods, irises, and posts; so, it was easy to fabriate. Besides, beause of using partial H-plane waveguide in the proposed filter, its ross-setion was one quarter of that of the onventional one, while their frequeny responses were the same. Another trait of the introdued filter was replaing λ/ waveguide setions as resonators with dieletri layers, whih made it possible to onsiderably redue the total length of the filter. Thus, the proposed filter had both advantages inluding redued rosssetional size and longitudinal length. To design the proposed filter, permittivity and thiness of dieletri layers had to be obtained. Performane of the proposed filter was verified using some theoretial and simulation examples. II. ANAYSIS OF THE PROPOSED FITER Fig. 1 shows the partial H-plane waveguide. ial H-plane waveguide is a onventional retangular waveguide in whih a partial metal vane is inserted in the H-plane. The ross-setion of partial H-plane waveguide has one quarter ross-setion of the onventional waveguide, while the dispersion harateristis of the first two dominant modes are the same [17]. Fig. demonstrates the proposed dieletri filled partial H-plane filter whih was made of K dieletri layers that were transversely inserted in a partial H-plane waveguide. ial H-plane rosssetions were a and b and the vane width and thiness of partial H-plane vane were assumed to be d and zero, respetively. The relative eletri permittivity and thiness of dieletri layers were, and d, respetively, for =1,,, K. The proposed struture did not vary in the transverse diretion; thus, only dominant TE 1 mode was propagated in the positive z- diretion. The frequeny domain analysis of multi-layer longitudinal inhomogeneous waveguides an be used to analyze the proposed struture. Based on this method, the hain parameter matrix of total struture an be written as follows: A B C D K T (1) 1 Fig.1. ial H-plane waveguide. (a) Side view. (b) Top view. Fig.. The proposed dieletri filled partial H-plane filter. where T is hain parameter of the -th dieletri layer and an be written as follows: os( d ) jz sin( d ) T. jsin( d ) / Z os( d ) () In (), β and Z are propagation oeffiient onstants and harateristi impedane, respetively, as follows:, ( f f ). (3) r Z, ( f f ). (4) r where f is the wave number of µ / eletromagneti wave and is the intrinsi impedane of wave both in free spae. For finding sattering parameters, onversion of T-parameter into S-parameter an be used: S S S AZ B CZ DZ (5) 11 AZ B CZ. DZ S Z 1 1 AZ B CZ DZ AZ B CZ DZ AZ B CZ DZ.. (6) (7) where Z is the harateristi impedane of partial H- plane waveguide at the enter frequeny given by: Z 1 ( f f ). (8) III. DESIGN PROCEDURE To design the proposed filter, values of the relative permittivity of dieletri layers and their thinesses had to be obtained so that a predefined frequeny harateristi ould be ahieved in a frequeny domain. The designed method was based on the optimization of a suitable fitness funtion along with limiting onditions for easy fabriation or implementation onsideration. On the other hand, the amplitude of S 1 parameter of the proposed struture was adjusted to the transfer funtion of arbitrary

3 desired filter in a frequeny range. That frequeny range was indiated by some frequeny samples with equal distane. So, the following fitness funtion an be defined for M disrete frequenies f 1, f,, f M all in the frequeny domain: M 1 fitness s f M In (9), f m s f 1 m 1 m H( f m). (9) m 1 is the absolute value of the proposed sattering parameter and is the absolute value of any desired transfer funtion both at frequeny. Here, the fitness funtion is defined based on the mean square error, by whih the amplitude of desired ideal filter is related to the amplitude of S 1 parameter of the proposed struture; so, optimum values inluding dieletri layer lengths and their relative eletri permittivity will be obtained. H ( f m ) The number of dieletri layers inserted in the partial H-plane waveguide was arbitrarily hosen; if the preision of transfer funtion of the designed filter were not aeptable, the number of layers must be inreased. Moreover, some restritions ould be dispensed on dieletri lengths and their permittivity for easy fabriation and implementation onsiderations. These onstrained onditions are as follows: d dmin 1 r, r,max (1) (11) for =1,, K. IV. EXAMPE AND RESUTS Example I: In this setion and in the first example, a third-order Chebyshev band-pass filter with the enter frequeny of 5 GHz, frational bandwidth (FBW) of 5%, and equal ripples of.1db in passband using partial H-plane waveguide was designed. Crosssetional dimensions of this partial H-plane waveguide were a=3.8 mm and b=1 mm and width of the metal vane was d=. mm. Also, the thiness of metal vane was assumed to be zero. The number of dieletri layers inserted in the partial H-plane waveguide was K= 15. In [17], the utoff frequeny of f 3.35 GHz for the dominant mode was alulated by both analyti and numerial methods, whih was equivalent to the dominant ut-off frequeny of the onventional waveguide with the dimension of a=47.55 mm and b=.15 mm. Then, the value of harateristi impedane was Z =485.9 (ohm). Thus, it is obvious that this ind of filter possessed the ross-setion of one quarter ompared to the ounterpart E-plane waveguide filter. Optimization onstrained onditions were set so that dieletri layer thinesses were greater than or equal to d min=.4 mm and maximum relative eletri permittivity was r,max 13. The frequeny range of optimization was GHz, f GHz, and f M 5.5 GHz and the number of equally spaed frequeny samples was M=51. Table I shows optimum relative permittivity and thiness of dieletri layers whih were obtained using optimization proess. Fig. 3 illustrates the optimum relative permittivity of dieletri layers. Also, Fig. 4 demonstrates optimum thiness values of dieletri layers. Fig. 5 ompares the transmission response of the band-pass filter designed with MATAB and simulated by HFSS and that of the ideal one. It is obvious that there was an exellent agreement between three urves in the frequeny range. It an be dedued from the optimum values of Table I that the proposed filter had the length of =1 mm; its length an be ompared with that of three ompat partial H-plane waveguide filters, as presented in [18]; thus, it an be onluded that this filter was 31% shorter than the most ompat one among those filters. TABE I. Optimum parameter of example I of the proposed filter., ε r Fig. 3. Optimum relative permittivity of dieletri layers for example I. Fig. 4. Optimum thiness values of dieletri layers for example I.

4 Fig. 5. Transmission response of band-pass filter of example I designed with MATAB and simulated by HFSS and that of the ideal one versus frequeny. Example II: In this setion and in the seond example, the same filter as in example I with new restrition on the maximum value of relative eletri permittivity of dieletri layers was designed. Here, it was assumed that and all other speifiations were the same as the former example. Table II shows optimum relative permittivity and thiness of dieletri layers of example II. Fig. 6 illustrates the optimum relative permittivity of dieletri layers. Also, Fig. 7 demonstrates optimum thiness values of dieletri layers. r,max 1 Fig. 8 ompares the transmission response of the band-pass filter designed with MATAB and simulated by HFSS and that of the ideal one. The length of the filter was =1 mm. It is obvious that, with a limitation on maximum dieletri permittivity, the agreement between the desired and optimum urves was degraded. Also, as the number of dieletri layers, K, inreased, the adjustment preision inreased. TABE II. Optimum parameter for the proposed filter in example II. NO NO, Fig. 7. Optimum thiness values of dieletri layers for example II. Fig. 8. Transmission response of band-pass filter of example II designed with MATAB and simulated by HFSS and that of the ideal one versus frequeny. Example III: In this setion and in the third example, a third-order Chebyshev band-rejet filter with the enter frequeny of 5 GHz, frational bandwidth (FBW) of 1% and equal ripples of 1 db was designed in passband using partial H-plane waveguide. Here, the length of filter was =15mm. Also, it was assumed that,max 15 r and all other speifiations of the struture were the same as the former example. The number of dieletri layers inserted in the partial H- plane waveguide was K= 17. Frequeny range of optimization was 4-6 GHz and the number of equally spaed frequeny samples was M=67. Table III shows optimum relative permittivity and thiness of dieletri layers of example III. Fig. 9 illustrates the optimum relative permittivity of dieletri layers. Also, Fig. 1 represents optimum thiness values of dieletri layers. Fig. 11 ompares the transmission response of the band-rejet filter designed with MATAB and simulated by HFSS and that of the ideal one. As demonstrates, there was about 3 db ripple in the passband of transmission response, whih was negligible in some appliations and had a sort of good stopband. Fig. 6. The optimum relative permittivity of dieletri layers for example II.

5 TABE III. Optimum parameter for the proposed filter in example III., V. CONCUSION In this artile, a new ind of ompat mirowave filter was proposed. The proposed ompat filter was made of some dieletri layers whih were transversely inserted in a partial H-plane waveguide. Beause of using partial H-plane waveguide, this filter had one quarter ross-setion ompared with the onventional waveguide filter for the same frequeny response. Moreover, it had onsiderably shortened total longitudinal length ompared with that of the existing partial H-plane waveguide filters. Some other advantages of the proposed filter inluded its easy fabriation sine there was no requirement on the indutive elements in its struture, high mehanial stability, ability of being used in high mirowave power, and ability of designing a arbitrary ind of filters. Also, it was possible to arbitrarily lose frequeny response of the proposed filter to that of the desired one by inreasing the number of dieletri layers. Usefulness and performane of the proposed struture were onfirmed and verified by designing and simulating some filters. REFERENCES Fig. 9. The optimum relative permittivity of dieletri layers for example III. Fig. 1. Optimum thiness values of dieletri layers for example III. Fig. 11. Transmission response of band-rejet filter of example III designed with MATAB and simulated by HFSS and that of the ideal one versus frequeny. [1] Matthaei, G..,. Young, and E. M. T. Jones, Mirowave Filters, Impedane-Mathing Networs and Coupling Strutures, Arteh House, Dedham, Mass., 198. [] evy, R., R. V. Snyder, and G. Mattaei, Design of mirowave filters, IEEE Trans. Mirowave Theory Teh., Vol. 5, pp ,. [3] Sotoodeh, Z., B. Beglarbegian, F. H. Kashani, and H. Ameri, A novel band pass waveguide filter struture on SIW tehnology, Progress In Eletromagnetis Researh etters, Vol., pp , 8. [4] Kobaysh, Y. and M. Mihegishi, A band pass filter using high- Q dieletri ring resonators, IEEE-MTT-S Digest, [5] Saliminejad, R. and M. R. Ghafouri Fard, A novel and aurate method for designing dieletri resonator filter, Progress In Eletromagnetis Researh B, Vol. 8, pp , 8. [6] Ghorbaninejad, H. and M. Khalaj-Amirhosseini, "Compat bandpass filters utilizing dieletri filled waveguides, Progress In Eletromagnetis Researh B, Vol. 7, pp , 8. [7] Khalaj-Amirhosseini, M., Mirowave filters using waveguides filled by multi-layer dieletri, Progress In Eletromagnetis Researh, PIER 66, pp , 6. [8] M.Khalaj-Amirhosseini and H. Ghorbaninejad, Arbitrary mirowave filters using waveguides filled by dieletri and magneti layers, Progress in Eletromagnetis Researh Symposium Proeedings, Xi an, China, pp. 6, Marh 1. [9] Khalaj-Amirhosseini, M., Analysis of longitudinally inhomogeneous waveguides using finite differene method, International Conferene on Information and Communiation Tehnologies: From Theory to Appliations, pp , Damasus, Syria, April, 6. [1] Khalaj-Amirhosseini, M., Analysis of longitudinally inhomogeneous waveguides using the fourier series expansion, Journal of Eletromagneti Waves and Appliations, Vol.,. 1, pp , 6. [11] Dwari, S. and S. Sanyal, Size redution and harmoni suppression of miro strip branh-line oupler using defeted ground struture, Mirowave and Optial Tehnology etters, Vol. 48, pp , 6. [1] Chen, W.. and G. M. Wang, Design of novel miniaturized fratal-shaped branh-line ouplers, Mirowave and Optial Tehnology etters, Vol. 5, pp , May 8.

6 [13] Saagami, I., M. Haga, and T. Munehiro, Redued branh line oupler using eight two-step stubs, IEE Pro. Mirow. Antennas Propag., Vol. 146,. 6, pp , [14] Khalaj-Amirhosseini, M., n uniform transmission lines as ompat uniform transmission lines, Progress In Eletromagnetis Researh C, Vol. 4, pp. 5-11, 8. [15] Collin, Foundations for mirowave engineering, IEEE press, pp , 199. [16] Dong-Won Kim and Jeong-Hae ee, ial H-Plane Filters With ially Inserted H-Plane Metal Vane, IEEE Mirowave and wireless omponent letters, Vol. 15,. 5, May 5. [17] Dong-Won Kim and Jeong-Hae ee, A partial H-plane waveguide as a new type of ompat waveguide, Mirowave Opt Tehnol ett 43, pp , Wiley Inter Siene, 4. [18] Dong-Won Kim, Dong-Jin Kim, and Jeong-Hae ee, Compat partial H-plane filters, IEEE transations on mirowave theory and tehniques, Vol. 54,. 11, pp , vember 6. A. Ghajar was born in Qazvin, Iran. He reeived his B. S. degree from Imam Khomeini International University (IKIU) in 1 in Teleommuniation Engineering. w he is M. S. student of university of guilan in Teleommuniation Engineering.His sientifi field of interest is mirowave omponent designing inluding, mirowave filters and frequeny seletive surfaes. H. Ghorbaninejad-Foumani was born in Guilan, Iran. He reeived his B. S. degree from university of guilan in 3 and his M. S. and Ph. D. degrees from Iran University of Siene and Tehnology (IUST) in 5 and 1 respetively, all in Teleommuniation Engineering. He is urrently assistant professor at department of eletrial engineering of university of guilan. His sientifi fields of interest are eletromagneti problems inluding mirowave and spatial filter design, ompat mirowave devies and finding Green s funtion of mirowave strutures.