диафрагмированные волноводные фильтры / 1988261c-baea-4022-9b9b-ade1cc8b7ace

M. Hajnorouzi

The University of Guila n

Email: m.hajnorouzi@gmail.com

Abstract – In this paper partial band-p ass waveguide filter using compact resonators are presented which is implemented in partial H-plane waveguide. Partial H-plane band-pass filters compared with E-plane band-pass filters, in the same frequency range, have one qu arter cross section size. Partial H-plane band-pass wav eguide filter with compact resonators has less longitudinally length relative to the conventional partial H-plane filters. Compact resonators in partial H-plane waveguides reduce both the cross section size and the total length of filter, in the sa me frequency range while compared with conventional partial H-plane filters. In the design procedure, the shape of resonators is determined by fitting the characteristic (transfer fun ction) of a desired resonator to that obtained from an equivalent circuit model. The design process is based on opti mization using an electromagnetic simulation to take the eff ect of higher order modes (evanescent mode). The usefulness of the proposed partial H-plane band-pass filter and its performance are verified by designing and simulating two filters.

Keywords – Partial H-plane Waaveguide, E-Plane Waveguide Band-Pass Filters, Half-wavelength Resonator, Quarter Wave-Length Resonator, Compact Resonator.

H. Ghorbaninejad

The University of Guilan

Email: ghorbaninej ad@guilan.ac.ir

shorted to that of conventional E-plane filter about % 29.2 [11].

In this paper partial H-plane band-pass waveguide filter using compact resonators are designed whose longitudinally length is consid erably shorter than that of half wavelength or quarter wa velength waveguide section resonators which is used in th e designed partial H-plane filters. Replacing existing ha lf wavelength or quarter wavelength waveguide sections by this new type resonator reduce the longitudinally size w hile its cross section is one quarter of E-plane waveguide band-pass filter and both have the same frequency responses. Partial H-plane bandpass waveguide filter with co mpact resonators has less longitudinally length relative to the designed partial H- plane filters and in the same ti me its cross section size is one quarter of conventional E-plane filters which leads to further size reduction in the filter structure. The shape of resonators is determined by fitting the characteristic (transfer function) of a desired resonator to that obtained from an equivalent circuit mod el.

Fig.2 shows the structure and geometry of a partial H- plane band-pass filter with half-wave length or quarter wavelength resonator sections and proposed partial H- plane waveguide band-pass filter with compact resonators. H-plane band-pass filter with half-wavelength or quarter wavelength resonator sections [11] is m ade of evanescent waveguide sections and half wavel ength waveguide sections which are placed between the m. In this structure the evanescent waveguide sections act as impedance invertors and half wavelength or q uarter wavelength waveguide sections act as resonators. T he partial H-plane waveguide band pass filter with compact resonators is

admittance invertors. In proposed designed method the length of each resonator is considera bly less than half wavelength waveguide section or evven quarter wave length waveguide sections resonators which leads to longitudinally reduced size filters compared with partial H-plane band-pass filter with half-wavelength or quarter wavelength resonator sections. The me thod of design of this partial H-plane waveguide band-pass filter is straightforward which is extensively explained in [11] which is based on optimization using an electromagnetic simulation. The later section dedicated to the design method of compact resonators usin g high frequency simulation software and circuit theory m odel.

Fig.3 shows top view of a proposed partial H-plane resonator. The resonator is located within a partial H-plane waveguide. The principle of partial H-plane resonator design is based on optimization using HFSS software. To design a waveguide band pass filter, one can calculate an LC equivalent circuit model. Figure 4 illustrated a band pass filter consisting of N parallel resonator and N+1 admittance invertors. The valu es of admittance invertors and parallel resonators can be calculated according to the desired filter specifications such as filter type, center frequency and the bandwidth of filter. This circuit model can be realized using N shunt resonators and N+1 quarter wavelength transmission line sections. In the conventional design methods the length of resonator units is about half wavelength waveguide sections . To obtain the geometry of proposed resonators, the dim ension of resonators, are optimized using an electromag netic simulator (HFSS) so that the frequency response of resonator can be fitted to that of LC circuit model resonators. In the optimization process the dimension of resonators are determined so that the S-parameters of electromagnetic simulator fit to that of LC circuit model, which are evaluated in frequency samples. In this designs 101 frequency samples in the range of frequency domain, 4.5-5.5 GHz, is considered.

Fig.2. (a) Three view and top v iew Structure of proposed partial H-plane band-pass filter with compact resonators (b) Three view and top view structure of partial H-plane band-pass filter with half-wavelength or quarter wavelength resonator sections [11]

In this section two propo sed partial H-plane Filter utilizing a rectangular waveguide with a=23.8 mm and b= 12 mm. The first design is a for 5-order equal ripple chebyshev filter with center frequency f0 = 5 GHz, the relative bandwidth 5 percent and equal ripples 0.01 dB is designed. In this design thick ness of metal vane has not been considered.

Optimization rang is 4.5-5.5 GHz and frequency sample steps is 10 MHz and it is assumed 15 frequency samples in pass-band and 43 frequency samples in each stop bands. Fig. 5 shows frequency responses of circuit model and that of designed partial H-plane resonators. By symmetry conditions resonators 1 and 2 are the same as resonators 5 and 4 respectively. Fig. 6 shows frequency responses of circuit model and that of designed partial H-plane filter. There is a good agreement between the frequency characteristics of desired filter and that of Designed filter over the frequency range.

Frequency [GHz]

Frequency [GHz]

Frequency [GHz]

(c)

Fig.5. Frequency responses of circuit model and that of designed partial H-plane resonators with zero metal vane thickness (a) resonators 1 and 5 (b) Resonators 2 and 4 (c) resonator 3

Frequency [GHz]

Fig.6. Frequency response of circuit model and that of designed partial H-plane filter with zero metal vane thickness

Frequency[GHz]

Frequency [GHz]

Frequency [GHz]

(c)

Fig.7. Frequency responses of circuit model and that of designed partial H-plane resonators with 0.1 mm metal vane thickness (a) resonators 1 and 5 (b) Resonators 2 and 4 (c) resonator 3

Fig.8. Frequency response of circuit model and that of designed partial H-plane filter with 0.1 mm metal vane thickness

Table 1: Dimensions of proposed designed filter with zero metal vane thickness

Dimensions of proposed designed filter with zero metal vanes are given in table 1. Second design is a 5-order equal ripple chebyshev filter with the same specification in which t=0.1 mm thickness of metal vane has been used. Fig. 7 shows frequency responses of circuit model and that of designed partial H-plane resonators with 0.1 mm thickness vane metal. Fig. 8 shows the frequency response of circuit model and that of designed partial H-plane filter with 0.1 mm thickness vane metal. Dimensions of proposed designed filter with 0.1 mm thickness metal vane are given in table 2.

VI. CONCLUSION

In this paper a compact partial H-plane filter have been presented. The total length of the proposed design filter with zero metal vane thickness is 82.35 millimeter and the total length of proposed designed filter with 0.1mm metal vane thickness is about 80 millimeter. While the length of partial H-plane filters with half wavelength or quarter wavelength section resonators in the best case is 144.11 millimeter [11].

The proposed partial H-plane filters compared with conventional half wavelength or quarter wavelength waveguide section resonators are longitudinally compact about 42 percent, while the cross section of both proposed partial H-plane waveguide filters is the same as conventional partial H-plane waveguide filter which is one quarter of the cross section of the counterpart E-plane waveguide filter. The simulated verification shows good agreement between proposed partial H-plane filter and circuit model results.

ACKNOWLEDGMENT

This work was supported by the I. R. of Iran Telecommunication Research Center.

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