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Three dual-mode band-pass filters are presented in the present paper. The first filter is realized by dual-mode substrate integrated waveguide (SIW) cavity; the second is based on the integration of SIW cavity with electromagnetic band gap (EBG); and the third is based on the integration of SIW cavity with complementary split ring resonator (CSRR). The dual-mode SIW cavity is designed to have a fractional bandwidth of 4.95% at the midband frequency of 9.08 GHz; the proposed EBG-SIW resonator operates at 9.12 GHz with a bandwidth of 4.38% and the CSRR-SIW resonator operates at 8.66 GHz with a bandwidth of 2.54%. The proposed filters have the high Q-factors and generate a transmission zero in upper stopband, and these by the use of Rogers RT/duriod 5880 (tm).

Rectangular waveguide filters are widely used in RF-Microwave industry, due to its characteristic properties of low losses, and high Q-factor. However, their integrations with planar structures in electronic systems are very difficult and their fabrications are expensive.

To resolve these problems, a new technology is implemented, called the substrate integrated waveguide (SIW). The SIW responds to these constraints in the design of microwave components by taking the advantages of low radiation loss, high power handling and high Q-factor.

The SIW is formed by two solid conductor planes, separated by a dielectric substrate, with conductor sidewalls emulated by rows of metalized through-plated via [

On the other hand, the metamaterials (electromagnetic band gaps (EBGs) and complementary split-ring resonators (CSRRs)) are used for manipulating electromagnetic waves and the unusual properties. The application of metamaterials has allowed a great improvement the performances and the size reduction in planar microwave applications, filter, and antenna [

In this paper, three dual-mode band-pass filters are proposed. These filters have been simulated in a commercial software package HFSS™, and thus a comparison was made between the proposed filters and several previous filters reported in [

The SIW cavity enables propagation of the mode (TE_{m}_{0p}), its parameters necessary are the length (L_{SIW}), the width (W_{SIW}), the diameter D of the metallic via hole and the spacing P between the holes, which are expressed

by the resonant frequency of rectangular cavity (

close to rectangular cavity filled with the same dielectric (ε_{r}) of length (L_{eff}) and width (W_{eff}) as shown in

The size of SIW cavity is designed from the empirical Equations (1) and (2) These Equations are valid for P < 4D and P < λ_{0} (ε_{r}/2)^{1/2} with λ_{0} the space wavelength [

The microstrip transition allows integration SIW to the planar structures (the planar transmission lines). _{T} and W_{T}) and the microstrip line (W_{M}) are expressed from the relations in [

The electromagnetic band gap structures are presented as the complex periodic structures. The electromagnetic band gap materials are used for many applications and especially in the frequency filtering, because of their electromagnetic properties, to create band gaps in the electromagnetic spectrum. The application of EBG has allowed a great improvement the performances of numerous devices in telecommunication systems.

shows the geometric structure of the proposed S-shape EBG.

Where M is the length of EBG, T is the width of EBG and V is the strip-length of EBG. The EBG is founded on the Bragg condition [

On the other, the CSRR is employed as LC resonator, thus the resonant frequency is obtained by the geometric parameters of CSRR. These specific properties are adaptable for many applications and especially the filters [

The dual-mode SIW cavity uses the substrate of Rogers RT/duriod 5880 (tm) (ε_{r} = 2.2, h = 0.508 mm and tanδ

= 0.0009), with D = 0.6 mm and P = 1 mm. By considering two orthogonal modes TE_{102} and TE_{301}, the size of dual-mode SIW cavity is designed from the Equation (4).

The initial dimensions of dual-mode SIW cavity with tapered transitions have been optimized by software package HFSS™. The detailed dimensions are decided as: W_{SIW} = 37.4 mm, L_{SIW} = 22 mm, W_{M} = 1.568 mm, W_{T} = 8 mm and L_{T} = 14.22 mm.

The simulation results for S-parameters of the dual-mode SIW cavity with tapered transitions are shown below in

Simulated results presented in

On the other hand, the integration of SIW cavity with EBG or CSRR allows the creation a dual-mode band-pass filter. The SIW is designed on substrate of Rogers RT/duriod 5880 (tm) (ε_{r} = 2.2, h = 0.508 mm and tanδ = 0.0009), with D = 0.6 mm and P = 1 mm. _{SIW} = 15 mm, W_{M} = 1.568 mm, L_{T} = 14.22 mm and W_{T} = 5.76 mm.

For analyzing the property of S-shaped EBG, one-cell EBG is etched on the top side of SIW. The dimensions of the one-cell EBG are: M = 2 mm, T = 5 mm, V = 0.9 mm. _{21} parameter of standard SIW and one-cell SIW-EBG are shown below in

As shown in

On the other hand, _{101}- mode-based SIW cavity is presented by a square cavity with W_{SIW} = L_{SIW} = 15 mm and the tapered transitions with the same dimensions W_{T} = 5.76 mm, L_{T} = 14.22 mm and W_{M}_{ }= 1.568 mm.

The simulation results for S-parameters of the proposed SIW resonator are shown below in

To make the characteristics of proposed SIW resonator clear, the width (W_{SIW}) is discussed in details. The simulation results for S_{21 }parameter of the SIW resonator with different values of W_{SIW} are shown below in

W_{SIW} (mm) | Passband frequency (GHz) | Center frequency (GHz) | Fractional bandwidth (%) | Insertion loss (dB) |
---|---|---|---|---|

15 | 8.94 to 9.27 | 9.11 | 3.73 | 0.371 |

15.4 | 8.84 to 9.17 | 8.98 | 3.67 | 0.4 |

15.8 | 8.74 to 9.05 | 8.87 | 3.49 | 0.42 |

As illustrated in _{SIW}) of SIW resonator increases the center frequency and the fractional bandwidth are decreasing, while the insertion loss becomes higher.

After studying the characteristics of SIW cavity and EBG, an EBG-SIW resonator is designed on the same substrate of Rogers RT/duriod 5880 (tm) (ε_{r} = 2.2, h = 0.508 mm and tanδ = 0.0009).

Simulated results presented in

Symbol | Value (mm) | Symbol | Value (mm) |
---|---|---|---|

D | 0.6 | L_{T} | 14.22 |

P | 1 | W_{M} | 1.568 |

W_{SIW} | 15 | M | 2.4 |

L_{SIW} | 15 | T | 5.4 |

W_{T} | 5.76 | V | 0.9 |

On the other hand, the characteristics of CSRR are analyzed, by using a simple model as shown in

In order to make the characteristics of proposed CSRR clear, its side-length (A) is discussed in details, with the same conditions as ε_{r} = 2.2, h = 0.508 mm, W_{T} = 5.76 mm, W_{M} = 1.568 mm, L_{T} = 14.22 mm, W_{SIW} = 15 mm, D = 0.6 mm, P = 1 mm. The influence of the side-length (A) is simulated and shown in

Simulated results presented in

After studying the characteristics of CSRR, a CSRR-SIW resonator is designed on the same substrate of Rogers RT/duriod 5880 (tm) (ε_{r} = 2.2, h = 0.508 mm and tanδ = 0.0009).

A (mm) | Centre stop band frequency (GHz) | Attenuation (dB) |
---|---|---|

3.6 | 11.06 | 36.66 |

3.8 | 10.32 | 38.84 |

4 | 9.65 | 40.88 |

Symbol | Value (mm) |
---|---|

D | 0.6 |

P | 1 |

W_{SIW} | 15 |

L_{SIW} | 15 |

W_{T} | 5.76 |

L_{T} | 14.22 |

W_{M} | 1.568 |

A | 3.5 |

F | 0.3 |

W | 0.3 |

G | 0.3 |

Simulated results presented in

In order to verify the characteristics of proposed filters, some comparisons between the proposed filters and several previous filters reported in the references are summarized in

In this paper, three dual-mode band-pass filters are proposed. The dual-mode SIW cavity filter has a center frequency of 9.08 GHz with a bandwidth of 4.95%. The insertion loss is 0.43 dB and the return loss is better than 20 dB across the band of interest. In addition, a transmission zero at 9.38 GHz and Q-factor is 414. The EBG-SIW resonator has a center frequency of 9.12 GHz with a bandwidth of 4.38%. The insertion loss is 1.18 dB and the return loss is better than 15 dB across the band of interest. In addition, a transmission zero at 12 GHz and Q-factor is 179. The CSRR-SIW resonator has a center frequency of 8.66 GHz with a bandwidth of 2.54%. The insertion loss is 0.55 dB and the return loss is better than 20 dB across the band of interest. In addition, a transmission zero at 11.73 GHz and Q-factor is 640. The simulation processes of the structures are done by using HFSS software. The design methods are discussed and presented.

Dual-mode band pass filters | Centre frequency (GHz) | Fractional bandwidth (%) | Insertion loss (dB) | Q-factor |
---|---|---|---|---|

[ | 2.41 | 4.50 | 1.38 | 151 |

[ | 2.40 | 12.50 | 0.39 | 182 |

[ | 14.42 | 2.64 | 2.60 | 146 |

[ | 5.00 | 4.00 | 0.70 | 322 |

Dual-mode SIW cavity | 9.08 | 4.95 | 0.43 | 414 |

EBG-SIW resonator | 9.12 | 4.38 | 1.18 | 179 |

CSRR-SIW resonator | 8.66 | 2.54 | 0.55 | 640 |

The proposed filters have a small size, high Q-factor and low loss, and can be directly integrated with other circuits without any additional mechanical assembling tuning. Additionally, these filters are easily scalable over microwave and millimeter frequency ranges.

AhmedRhbanou,MohamedSabbane,SeddikBri, (2015) Design of Dual-Mode Substrate Integrated Waveguide Band-Pass Filters. Circuits and Systems,06,257-267. doi: 10.4236/cs.2015.612026