диафрагмированные волноводные фильтры / acbe8bfd-cdf7-4e93-a2c2-d01ba1841124
.pdfElectromagnetic Modelling of Ridged Waveguide Resonator
Loaded Bandpass Filters
N. Suntheralingam, N. Mohottige and D. Budimir
Wireless Communications Research Group, School of Electronics and Computer Science, University of Westminster, London, W1W 6UW, United Kingdom
E-mail: d.budimir@westminster.ac.uk
Introduction
The rapid expansion of modern wireless communication systems demand microwave filters with improved characteristics. Over the past few decades allmetal inserts placed in the E-plane of a rectangular waveguide have been a sustainable solution for robust, low-cost, mass producible, low loss and high power filters at microwave and millimeter-wave frequencies. However, despite their favorable performances, the attenuation in the second stopband may often be too low and too narrow for diplexer and multiplexer applications.
In recent years, a number of approaches have been proposed in order to improve the performances of rectangular waveguide bandpass filters [4]-[5]. By employing ridged resonators, we can change the cutoff frequency of a conventional waveguide resonator and achieve shorter resonator length. This is due to the reduced guided wavelength of the ridged waveguide relative to those of a wave propagating in a comparable homogeneous resonator structures. Hence the length of a half wavelength resonator is accordingly reduced. In the mean time, it can also be shown that these ridged resonators can be used to produce stopband transmission zeros (TZs) in certain waveguide configurations. This property, of ridged resonators, could very well be utilized to improve stopband performance of bandpass filters.
This paper, therefore, proposes replacement of conventional section of rectangular waveguide E-plane filters with the ridged resonator loaded structures. These structures, while improving stopband performance and compactness, maintain the low-cost and mass-producible characteristics of split-block metal insert E-plane technology.
Proposed Ridged Waveguide Resonator Loaded Filters
The proposed ridged waveguide resonator loaded bandpass filter structures (filter I and II ) are shown in Fig. 1. The proposed filter structures are constructed on dielectric slabs, where the ridged resonators along with the metal septa are etched on a single side of the substrate. Rogers/RT Duruid 5880 is used as the dielectric material which has relative dielectric permittivity of 2.2, thickness of 0.508 mm and the metallization thickness of 0.017 mm. The slabs
are then inserted in the line of symmetry of hollow metallic waveguides thus changing the electromagnetic properties. Standard rectangular waveguides of WG-16 (a = 22.86 mm, b = 10.16 mm) have been used as housings to fit these filter structures.
b
lr4 lr3 
lr2
lr1
ls3
ls2
ls1
a
b
lr5
lr4 
lr3 |
ls4 |
|
lr2 |
ls3 |
lr1 |
ls2 |
ls1
a
Filter I |
Filter II |
Fig. 1. Configurations of ridged waveguide resonator loaded bandpass filters
The electromagnetic analysis, of the proposed ridged resonator loaded waveguide filter structures, is based on the finite element method (HFSSTM) [8]. Dimensions of the proposed filter at 9.45 GHz are given in Table I. The proposed filters, Filter 1 and Filter 2, have their total structure lengths of 47.9 mm and 62 mm respectively. Simulated insertion and return losses of the proposed filters I and II are shown in Fig. 2.
Table I
DIMENSIONS OF THE PROPOSED WAVEGUIDE FILTERS
Parameters |
Ridged resonator |
Ridged resonator loaded |
|
loaded waveguide |
|||
(mm) |
waveguide Filter II |
||
Filter I |
|||
|
|
||
|
|
|
|
Inside waveguide |
22.86x 10.16 |
22.86x 10.16 |
|
dimensions |
(WG-16) |
(WG-16) |
|
Metallization thickness |
0.017 |
0.017 |
|
Dielectric thickness |
0.508 |
0.508 |
|
Length of the |
ls1 = ls3 = 0.8, |
ls1 = ls4 = 1.0, ls2 = ls3 = 4.5 |
|
metal septa( ls) |
ls2 = 3.5 |
||
|
|||
Resonator lengths ( lr) |
lr1 = lr4 = 9.5, |
lr1 = lr5 = 6.9, |
|
lr2 = lr3 = 11.9 |
lr2 = lr3 = lr4 = 12.4 |
||
|
|||
Total structure length |
47.9 |
62 |
|
0 |
|
|
|
|
|
0 |
|
-20 |
|
|
|
|
|
-20 |
|
|
|
|
|
|
|
|
(dB) |
|
|
|
|
|
(dB) |
-40 |
S-Parameters |
|
|
|
|
|
S-Parameters |
|
-40 |
|
|
|
|
|
||
|
|
|
|
|
-60 |
||
|
|
|
|
|
|
||
|
-60 |
|
|
|
|
TZ2 |
|
|
|
|
TZ1 |
|
|
-80 |
|
|
|
|
S21 |
|
|
||
|
|
|
|
|
|
||
|
|
|
S11 |
|
|
|
|
|
-80 |
|
|
|
|
|
-100 |
|
6 |
8 |
10 |
12 |
14 |
16 |
|
|
|
|
Frequency (GHz) |
|
|
|
|
|
|
TZ1 |
|
|
|
|
S21 |
|
|
|
|
S11 |
|
TZ2 |
6 |
8 |
10 |
12 |
14 |
|
|
Frequency (GHz) |
|
|
(a) |
(b) |
Fig. 2. Simulated Insertion and Return losses of the proposed bandpass filters
(a) Filter I (b) Filter II
Conclusion
A new class of E-Plane ridged waveguide resonator loaded filter structures, with improved performances, has been proposed. The proposed structures can be easily realized with metallo-dielectric inserts within the standard rectangular waveguides. These filter structures have been designed and simulated at centre frequency 9.45 GHz. The proposed structures maintain low-cost and mass producible characteristics of E-plane filters while achieving significant size reduction.
References
[1]Vicente E. Boria and Benito Gimeno, “Waveguide Filters for Satellites” IEEE Microwave Magazine, Vol.8, Issue 5, pp.60-70, October 2007.
[2]Ian C. Hunter, Laurent Billonet, Bernard Jarry, Pierre Guillon, “Microwave Filters—Applications and Technology” IEEE Trans. Microwave Theory Tech.,Vol.50, pp. 794-805, Mar. 2002.
[3]D. Budimir, "Generalized Filter Design by Computer Optimization", ISBN 0-89006-579-9, Atrtech House Books, 1998.
[4]D. Budimir, “Optimized E-plane bandpass filters with improved stopband performance,” IEEE Trans. Microwave Theory Tech., vol. 45, pp.212–220, Feb. 1997.
[5]G. Goussetis, and D. Budimir, " Compact Ridged Waveguide Filters with Improved Stopband Performance”, IEEE MTT-S International Microwave
Symposium, pp.953-956, June 8-13, 2003, Philadelphia, USA.
[6]Jingjing Zhang , Hongsheng Chen , Yu Luo , Linfang Shen , Lixin Ran , Jin Au Kong , “Wideband backward coupling based on anisotropic left-handed metamaterial” , Applied Physics Letters , Vol. 90 , No. 4 , pp. 043506 , January 2007.
[7]N. Suntheralingam, A. Shelkovnikov and D. Budimir, “Novel Millimetre Wave Metawaveguide Resonators and Filters”, 37th European Microwave Conference, Munich, Germany, 8-12 October 2007.
[8]HFSS, Ansoft Technologies, 2005