диафрагмированные волноводные фильтры / b28980fb-ebcf-4027-9c65-1d0a260b3047

Abstract — In this paper, two types of partial H-plane bandpass filter are proposed , which are implemented by substrate integrated folded waveguide (SIFW). These filters have advantages of compact, easy for integration, low cost, and mass-producible properties. The presented partial H-plane bandpass filter with H-plane septa has the similar frequency responses as those of traditional E-plane waveguide filter. Another partial H-plane bandpass filter is implemented by inserting H-plane slots in H-plane metal vane. Two filters are designed using the proposed two types of partial H-plane filters. The vertical metal walls of SIFW are realized by closely spaced metallic vias. The tapered line is used as transition between SIFW and microstrip. The two designed partial H-plane filters exhibits excellent performances by simulation.

Index Terms —partial H-plane filter, substrate integrated folded waveguide (SIFW), H-plane septa, H-plane slot, bandpass filter.

I. INTRODUCTION

Traditional metallic waveguide components have been widely used in microwave and millimeter wave systems for their attractive advantages of low insertion loss and high power handling capacity. Unfortunately, metallic waveguides are three-dimensional (3-D) by nature, and are difficult to integrate with planar circuits. Furthermore, at the low frequencies, metallic waveguides have large dimensions and a considerable weight. In order to overcome these disadvantages of metallic waveguides, substrate integrated waveguide (SIW) technology that can be fabricated within printed circuit board (PCB), low temperature co-fired ceramic (LTCC) and thin film process was recently proposed [1-2]. It has attracted much interest because of its clear advantages over metallic waveguides, such as easy fabrication, easy integration with planar transmission lines, planar integration and low cost. The SIW structure consists of a dielectric substrate comprised of between a pair of metal plates which are connected through via holes, as shown in Fig. 1 (a). However, compared with microstrip, stripline and coplanar waveguide components, the width of SIW may be too large for some circuits, especially at low frequencies. So, width reduction and compact integration is still desirable. In order to reduce the width, metallic folded waveguides are proposed [3-4]. Then, the concept and geometry of substrate integrated folded waveguides (SIFW) with walls of metallic via holes are presented [5-6]. Several components have been studied to demonstrate these structures. Configuration of one type SIFW is shown in Fig. 1 (b). The width of the SIFW is nearly half of the width of the original SIW, its height is twice that of the

SIW, and the SIFW also has nearly the same propagation and cutoff characteristics as the SIW [7].

Fig. 1. Configuration of SIW and SIFW: (a) SIW, (b) SIFW

In this paper, two types of partial H-plane bandpass filter based on the SIFW are presented. One type filter employs evanescent waveguide with H-plane septa as K-inverter, which has the similar frequency responses as those of traditional E-plane waveguide filter. Another filter is realized by inserting H-plane slot in H-plane metal vane as J-inverter. Compared with their unfolded counterparts, the two types of bandpass filter are significantly reduced. More importantly, their performances are defined by the metallization on the middle layer which can be defined very accurately using photolithography. Two three-pole bandpass filters are designed using the proposed two types of structure. The tapered line is used as transition between SIFW and microstrip for convenient measurement. The two designed partial H-plane bandpass filters exhibit excellent performances by simulation.

II. THEORY AND DESIGN

The structure of an SIW is shown in Fig. 1 (a) and that of an SIFW in Fig. 1 (b), with a2 being the width of the SIFW and d being the spacing between the H-plane metal vane and the right wall of metallic via holes. The thickness 2h of the SIFW of Fig. 1 (b) is twice that of the h of the SIW in Fig. 1

(a), while its width a2 is nearly half of a. The fundamental mode of the SIFW is TE10 mode. The maximum field is presented at edge of the guide between the middle conductor and sidewall. For the correct choice of a2, h and d, the SIFW can be made to have the identical propagation characteristics to that of the SIW.

Fig. 2. Structure of the proposed partial H-plane filter with H- plane septa.

A. type one

The 3-D structure of the proposed type one partial H-plane bandpass filter made by a SIFW is illustrated in Fig. 2. The design idea is inspired from [8], which is based on metallic waveguide. This configuration provides a more compact bandpass filter compared with original design. The proposed filter consists of resonators alternating with evanescent waveguide sections. Evanescent waveguide sections are implemented by inserting H-plane septa between the H-plane metal vane and sidewall of metallic via holes, as shown in Fig. 2. Microstrip to stripline to tapered line to SIFW transition is employed for convenience of test and integration. The partial H-plane bandpass filter based on SIFW is a direct-coupled resonator filter like an E-plane waveguide filter. It is composed of half-wavelength resonators, which are terminated with shorted end. So, the evanescent waveguide can be represented with an impedance inverter (K-inverter) circuit, as shown in Fig. 3.

Fig. 3. Impedance inverter (K-inverter) for evanescent

The design method of the proposed partial H-plane bandpass filter based on SIFW is uniform with that of the partial H-plane filter based on metal rectangular waveguide

[8]. Normalized inverter value K and negative electrical length φ are given by [9]:

Where Zg is a wave impedance of a partial H-plane SIFW. At the same time, the normalized inverter values for an equalripple bandpass filter are [10]:

Where g0, g1, … , gn+1 are element values for an equal-ripple low-pass prototype and n is a normalized cutoff frequency.

g0, g0, and g0 are waveguide wavelengths at center frequency and at lower and upper passband edge frequency.is a relative bandwidth, and n is the order of the filter. The values of the K-inverters are controlled by changing the width (Wj) of the H-plane septa. By method of parameterextraction, relationship between values of the K-inverters and Wj can be established. The length of the half-wavelength resonators is given by [9]

A commercial full-wave 3-D FEM simulator (Ansoft HFSS) is used to analyze and optimize the filter after the initial design.

B. type two

The 3-D structure of the proposed type two partial H-plane bandpass filter made by a SIFW is illustrated in Fig. 4. The design idea is inspired from [11], which is based on metallic waveguide. This configuration provides a more compact bandpass filter compared with original design. The proposed filter consists of resonators alternating with evanescent

waveguide sections. Evanescent waveguide sections are implemented by inserting H-plane slot in H-plane metal vane, as shown in Fig. 4. Microstrip to stripline to tapered line to SIFW transition is employed for convenience of test and integration. The partial H-plane bandpass filter based on SIFW is a direct-coupled resonator filter. It is composed of half-wavelength resonators, which are terminated with opened end. So, the evanescent waveguide can be represented with an admittance inverter (J-inverter) circuit, as shown in Fig. 5.

Fig. 4. Structure of the proposed partial H-plane filter with H- plane intaglio.

Fig. 5. Admittance inverter (J-inverter) for H-plane intaglio.

The design method of the proposed partial H-plane bandpass filter based on SIFW is uniform with that of the partial H-plane filter based on metal rectangular waveguide [11]. Normalized inverter value J and negative electrical length φ are given by [9]:

Where Yg is a wave impedance of a partial H-plane SIFW. At the same time, the normalized inverter values for an equalripple bandpass filter are defined by [9]:

Where g0, g1, … , gn+1 are element values for an equal-ripple low-pass prototype and n is a normalized cutoff frequency.

g0, g0, and g0 are waveguide wavelengths at center frequency and at lower and upper passband edge frequency.is a relative bandwidth, and n is the order of the filter. The values of the J-inverters are controlled by changing the width (Wj) and the depth (Sj) of the H-plane slot. By method of parameter-extraction, relationship between values of the J- inverters and Wj and Sj can be established. The length of the half-wavelength resonators is given by [9]

Full-wave 3-D FEM simulator (Ansoft HFSS) is used to analyze and optimize the filter after the initial design.

III. RESULTS AND DISCUSSION

According to the design method in section two, two threepole bandpass filters are designed using the proposed two types of structure. The layouts of the two designed partial H- plane filters are shown in Fig. 6 and 7, respectively. Through analyzing and optimizing using HFSS, the geometric dimensions of the two filters are determined as follows: for type one filter, W0 = 0.75 mm, W1 = 2.5 mm, W2 = 6.85 mm, W3 = 0.4 mm, W4 = 1.88 mm, R1 = 9.93 mm, R2 = 9.94 mm, Q = 0.5 mm, P = 1 mm, L = 6.3 mm, d = 1.1 mm, a = 8.2 mm; for type two filter, W0 = 0.75 mm, W1 = 1.8 mm, W2 = 1 mm, W3 = 0.6 mm, W4 = 2.2 mm, W5 = 2.22 mm, W6 = 0.5 mm, S1 = 2.68 mm, S2 = 4.43 mm, S3 = 4.68 mm, S4 = 2.55 mm, R1 = 17.91 mm, R2 = 16.54 mm, R3 = 17.8 mm, Q = 0.5 mm, P = 1 mm, L = 7.42 mm, d = 1.1 mm, a = 8.2 mm. The simulated results are shown in Fig. 8 and 9, respectively. It can be seen from Fig. 8 that the designed H- plane bandpass filter with H-plane septa has similar frequency responses as those of traditional E-plane waveguide filter. The insertion loss is better than 1.3 dB and return loss is better than 29 dB in the passband (9.9 GHz-10.1 GHz). By comparing Fig. 9 and Fig. 8, it is obviously that the

type two filter has better rejection out of band in upper than the type one filer. The insertion loss and return loss of the designed H-plane bandpass filter with H-plane slot are better than 1.3 dB and 20 dB in the passband (9.9 GHz-10.1 GHz).

Fig. 6. Layout of the three-pole partial H-plane filter with H- plane septa (type one).

Fig. 7. Layout of the three-pole partial H-plane filter with H- plane intaglio (type two).

Frequency (GHz)

Fig. 8. Simulated results of the three-pole partial H-plane filter with H-plane septa.

IV. CONCLUSION

This paper has presented two types H-plane bandpass filters based on SIFW. One type filter employs evanescent waveguide with H-plane septa as K-inverter, which has the similar frequency responses as those of traditional E-plane waveguide filter. Another filter is realized by inserting H- plane slot in H-plane metal vane as J-inverter. Two three-pole bandpass filters are designed using the proposed two types of structure. The two designed partial H-plane bandpass filters exhibit excellent performances by simulation.

Frequency (GHz)

Fig. 9. Simulated results of the three-pole partial H-plane filter with H-plane intaglio.

REFERENCES

[1]H. Uchimura, T. Takenoshita, and M. Fujii, “Development of “a laminated waveguide”.” IEEE Trans. Microw. Theory Tech., vol. 46, no. 12, pp. 2437-2443, Dec. 1998.

[2]D. Deslandes and K. Wu, “Integrated microstrip and rectangular waveguide in planar form,” IEEE Microw. Wireless Compon. Lett., vol. 11, no. 2, pp. 68-70, Feb. 2001.

[3]Kim, D.W., and Lee, J.H.: ‘A partial H-plane waveguide as a new type of compact waveguide’, Microw. Opt. Technol. Lett., 2004, 43, (5), pp. 426-428

[4]G. L. Chen, T. L. Owens, and J. H. Whealton, “Theory Study of the Folded Waveguide,” IEEE Trans. Microw. Theory Tech., vol. 16, no. 2, pp.305-311, Apr. 1988.

[5]N. Grigoropoulos, and P. R. Young, “Compact Folded Waveguide,” in 34th Eur. Microw. Conf., Amsterdam, The Netherlands, 2004, pp. 973-976.

[6]N. Grigoropoulos, B. S. Izquierdo, and P. R. Young, “Substrate Integrated Folded Waveguides (SIFW) and Filters,” IEEE Microw. Wireless Compon. Lett., vol. 15, no. 12, pp. 829-831, Dec. 2005.

[7]W. Q. Che, L. Geng, K. Deng, and Y. L. Chow “Analysis and Experiments of Compact Folded Substrate Integrated Waveguide,” IEEE Trans. Microw. Theory Tech., vol. 56, no. 1, pp.88-93, Jan. 2008.

[8]D. W. Kim, D. J. Kim, and J. H. Lee, “Compact Partial H-plane filters,” IEEE Trans. Microw. Theory Tech., vol. 54, no. 11, pp.2923-2930, Nov. 2006.

[9]G. Matthaei, L. Yong, and E. M. T. Jones, “Microwave Filter, Impedance-Matching Networks, and Coupling Structures,” Boston, MA: Artech House, 1980.

[10]R. Levy, “Theory of direct-coupled-cavity filters,” IEEE Trans. Microw. Theory Tech., vol. 15, no. 6, pp. 340-348, Jun. 1967.

[11]D. J. Kim, and J. H. Lee, “Partial H-plane Filters With Multiple Transmission Zeros,” IEEE Trans. Microw. Theory Tech., vol. 56, no. 7, pp.1693-1698, Jul. 2008.