диафрагмированные волноводные фильтры / 801d538f-5638-41e7-8a70-8ae286a71ead

Abstract- In this paper, a new category of waveguide E-plane filters is summarized. This kind of filters use the planar stripline as the resonating element. This kind of filters using split-block substrate insert E-plane technology can achieve very compact filtering structure at millimeter-wave with very low fabrication cost. Four different waveguide E-plane filters are presented.

I.INTRODUCTION

Waveguide filters are widely used in wireless communication, radar and satellite applications [1] resulting from their benefits of low-loss, high power handling capability and sharp cutoff shirts. However, the conventional waveguide filters were often implemented with large size [2]. Emerging applications continue to challenge waveguide filters with more stringent requirements of higher performance, smaller size, lighter weight, and lower cost. Since the Waveguide E-plane filter was introduced by Y. Konishi and K. Uenakada [3] in 1974, it has been widely used and investigated because this kind of waveguide filter not only keeps some properties of the waveguide but also brings advantages of mass production and low cost. However, in order to improve the filtering performance, this conventional waveguide E-plane filter should cascade more than one half-wavelength resonator, leading to large size and insertion loss. Nevertheless, the typical metal septa E-plane filters are still used in recently designs [4] and [5]. At the same time, many novel waveguide E-plane filters have been developed to improve the filter performance and realize more compact size. In [6], [7] three metal inserts are used to achieve good filter performance and compact size. In [8], a novel filter based on E-plane metaldielectric inserting in a rectangular waveguide was proposed by designing the metallic septa, C- and I-shaped resonators to implement significant size reduction. The S-shape resonators [9] were utilized to improve the stopband performance and compactness. Designing T-shape resonator [10] and extra resonator [11] in the conventional E-plane filter for miniaturization were presented.

In this paper, a new category of waveguide E-plane filters is summaried, including four different E-plane filters. The presented filters are designed by using the planar stripline resonators and waveguide E-plane technology, so they have benefits of low cost and mass production.

Frequency (GHz)

Fig. 1. The simulation results of E-plane filter with multiple transmission zeroes (with g0 = 0.1, g1 = 2, g2 = 0.3, g3 = 0.05, l1 = 0.3, l2 = 0.2, h1 = 3.2, h2 = 3, h3 = 0.8, w = 0.1)

II.E-PLANE FILTERS

A.E-plane Filter with Multiple Transmission Zeroes [12]

In [12], considering the high-pass property of the waveguide, a novel waveguide E-plane bandpass filter is designed by allocating the appropriate transmission zeroes in standard frequency band of the corresponding standard waveguide as shown in Fig. 1. Two pairs of resonators are located on the top of the substrate which is inserted in the center E-plane of the waveguide. In this configuration, the two C-shaped resonators arranged face-to-face are used to introduce two transmission zeroes in the lower stopband of the E-plane bandpass filter. On the other hand, the two centralfolded stripline resonators are used to induce the other two transmission zeroes in the upper stopband. This presented E- plane filter is less than in the transmission direction. Four transmission zeroes introduced by four resonators improve the rejection levels outside the passband and contribute to the selectivity of the passband. The proposed filter can implement different bandwidth with fixed central frequency by designing the sizes and couplings of the two pairs of resonator which determine the locations of the transmission zeroes.

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Frequency (GHz)

Fig. 2. The simulation and measurement results of the dual-band E-plane waveguide filter (with w1 = g2= g3 = 0.1 mm, l1 = 0.3 mm, h1 = 3 mm, h2 = 3.3 mm, h3 = 0.6 mm, g1 = 1 mm, w2 = 0.3 mm, l2 = 0.4 mm and d = 1 mm).

The existing waveguide dual-band filters are almost based on dual-mode cavities, which have the disadvantages of complex design and high cost and are not suitable to mass production. Thus, in order to realize easy fabrication, low cost and mass production, a novel waveguide E-plane dual-band filter is conducted. As discussed in the subsection A, a waveguide E-plane filter was proposed with a single passband by etching two pairs of resonators on the top of a substrate. In order to achieve dual-band performance and compact size, a pair of straight stripline resonators, as shown in Fig. 2, is added to the bottom side of the substrate to construct the proposed waveguide E-plane dual-band filter. The simulation result of S21 is given in Fig. 2 as well. Two passbands with good filtering performance are formed. In addition, there are two transmission zeroes between the two passbands to suppress the interference. This dual-band filter has the advantages of compact sizes, low cost and easy fabrication.

C.E-plane Dual-band Bandstop Filter [14]

A waveguide E-plane dual-band bandstop filter with easy fabrication is proposed by using folded split ring resonators (FSRRs). The proposed filter has high rejection levels in the stopbands and good transmission performance outside the stopbands (in the passbands) as shown in Fig. 3. The FSRRs (denoted by FSRR1 and FSRR2) with different sizes are placed alternatively to introduce two different stopbands. In order to obtain high selectivity, the heights of FSRRs are fixed to be 1 mm. The FSRR1 and FSRR2 have the same values of parameters except for the length l. The distances are carefully designed and optimized. Simulation results of a sample are presented in Fig. 3. Triple passbands in Ka-band are formed by two stopbands which are introduced by the resonances of FSRR1 and FSRR2. The rejections in the stopbands are more than 20 dB and transmission performances in the three passbands are good. The triple passbands have the advantages of high selectivity and low insertion loss. By designing FSRRs, we can design the filters having the required stopbands.

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Frequency (GHz)

Fig. 3. The simulation results of a dual-band bandstop E-plane filter with SRR1 (h = 1 mm, l = 0.7 mm, w = 0.1 mm, g1 = 0.2 mm, and g2 = 0.1 mm) and SRR2 (h = 1 mm, l = 0.86 mm, w = 0.1 mm, g1 = 0.2 mm, and g2 = 0.1 mm).

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Frequency (GHz)

Fig. 4. The simulation results of the EMIT E-plane filter (with h = 3.2 mm,l=2mm and t=0.15mm).

D.EMIT E-plane Filter [15]

Finally, a novel kind of waveguide E-plane filter is presented based on the concept of electromagnetically induced transparency (EMIT). The filter configuration and simulation results are given in Fig. 4. A rectangular ring on the top of substrate is used to model the effect of the opaque situation, which is to introduce a wide absorption band. And two metal strip lines are etched on the opposite side are utilized to induce transparency (E-IT) and magnetic induced transparency (M- IT) simultaneously. The passband of the designed EMIT filter is the superposition of these two transparencies. The length of designed EMIT E-plane selectivity, low insertion loss and flat group delay.

III. CONCLUSION

This paper summarized a new category of waveguide E-plane filters, which use the planar stripline resonators and split-block substrate insert E-plane technology. Four different waveguide E-plane filters are presented, including a waveguide E-plane bandpass filter with multiple transmission zeroes, a waveguide