диафрагмированные волноводные фильтры / 4b860ae3-e5c5-40fe-bbf5-87bfb4cfb758

Figure 17 Radiation pattern for Antenna4 at 3.33 GHz

Figures 12 and 13 show the patterns for Antenna 3. The crosspolarized components are about 15.2 dB and 14 dB down from their co-polarized components. The absolute gains of the antenna are 4.2 dBi and 4 dBi at the two frequencies, respectively. Figures 14 –17 show the patterns for Antenna 4. The cross-polarized components are about 13.7 dB, 14.2 dB, 10 dB, and 18.2 dB down compared with their co-polarized components. The absolute gains of the antenna are 2.2 dBi, 2 dBi, 2.1 dBi, and 1.5 dBi at the resonant frequencies, respectively.

4. CONCLUSION

A novel, compact, single probe-fed rectangular microstrip patch antenna for dual and multi frequency operation has been presented. Because of the additional slot perturbation for the horizontal patch, surface current path as compared with the reference antenna without slot is lengthened, which lowers the corresponding resonant frequencies. Detailed studies of relevant papers reveal that maximum 55% size reduction has been achieved earlier. In our proposed design size reduction of 85% with a high isolation (15.6 dB for antenna 3) between the two modes is demonstrated. Radiation patterns of the reference antenna with different feeding points and those of the proposed antennas with slots are also studied in detail. Results shown here are really encouraging. Because of their compactness with tremendous size reduction with sufficient isolation the proposed antennas are suitable for mobile and wireless communication. It is observed that the beam widths and power gains are worse at lower frequencies for antenna 3 and antenna 4. Extensive efforts are being provided to improve the beam widths and power gain at lower frequencies.

ACKNOWLEDGMENT

The authors are indebted to Japan-Indo Collaborative Project on Infrastructural Communication Technologies Supporting Fully Ubiquitous Information Society for technical help.

REFERENCES

1. A. Serrano-Vaello and S. Hernandez, Printed antennas for dual-band GSM/DCS 1800 mobile handsets, Electron Lett 34 (1998), 140 –141.

2.W.S. Chen, Single-feed dual frequency rectangular microstrip antenna with square slot, Electron Lett 34 (1998), 231–232.

3.S.C. Gao and J. Li, FDTD analysis of a size-reduced, dual-frequency

patch antenna, Progr Electromagn Res 23 (1999), 59 –77.

4.S.C. Pan and K.L. Woung, Dual frequency triangular microstrip antenna with a shorting pin, IEEE Trans Antennas Propagat 45 (1997), 1889 –1891.

5.S.C. Gao and L.W. Li., Small dual-frequency microstrip antenna, IEEE Trans Vehicular Technol 51 (2002).

6.K. Gosalia and G. Lazzi, Reduced size, dual-polarized microstrip patch antenna for wireless communications, IEEE Trans Antenna Prop 51 (2003).

7.X.L. Bao and M.J. Ammann, Compact annular-ring embedded circular patch antenna with a cross-slot ground plane for circular polarization, Electron Lett 42 (2006).

8.S. Bhunia, S. Biswas, D. Sarkar, and P.P. Sarkar, Experimental investigation on dual-frequency broad band microstrip antenna with swastika

Slot, Ind J Phys 81 (2007), 497– 499.

© 2008 Wiley Periodicals, Inc.

A SECTORAL HORN ANTENNA BASED ON THE ELECTROMAGNETIC BANDGAP STRUCTURES

Zeyu Zhao, Qiling Deng, Huiliang Xu, Chunlei Du, and Xiangang Luo

State Key Laboratory of Optical Technologies for Microfabrication, Institute of Optics and Electronics, Chinese Academy of Sciences, Chengdu, Sichuan Province 610209, China; Corresponding author: lxg@ioe.ac.cn

Received 11 September 2007

ABSTRACT: Recently, the electromagnetic band-gap (EBG) material, also known as photonic crystals, has been successfully used to suppress surface-wave for the patch antenna. In this article, a sectoral horn antenna with the mushroom-like EBG material is designed to enhance its gain. A flange plate is attached to the horn antenna mouth and a mush- room-like EBG material is sticked to the flange plate. Because of effective surface-wave suppression, the simulant and test results show that the gain of this sectoral horn antenna has almost increased 1.0 dB within the frequency from 11.7 to 14.0 GHz. This kind of horn antenna has the potential application in mobile and satellite communications. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 965–969, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23254

Key words: electromagnetic band-gap (EBG); surface wave; sectoral horn antenna

1. INTRODUCTION

As feeds for high efficiency reflector antennas, the horn which has been widely used in astronomy and communication domain has simple structure, wide bandwidth, and lower loss. However, because of the propagation of the surface wave along the horn’s side wall, the electromagnetic wave has occurred diffraction on the horn mouth, which has raised the side lobes, reduced the gain, and decreased the front-to-back ratio. Usually, there are two methods to solve these problems. One is diaphragm horn, [1] sticking the diaphragm plate on the side wall of the horn, which make the electromagnetic intensity to become ladder’s distribution and accordingly depress the side lobes. The other is corrugation horn [2, 3] that fabricates a series of complex corrugations on the horn’s side wall to suppress the surface current. These methods have some problems such as complicated designs, difficult fabrication. As a result, the application in a certain extent is limited.

The electromagnetic band-gap (EBG) material, which are realized by 3D periodical structures, have obvious band-gap features and have been suggested in based on the photonic band-gap (PBG) phenomena in optics [4] and have been prevented the propagation of the electromagnetic waves in a specified band of frequency. In recent years, the EBG material have been widely researched and

Figure 1 The EBG E-plane sectoral: (1) E-plane sectoral horn; (2) flange plate; (3) EBG material. The EBG sectoral horn size: 41.98 mm 19.05 mm, length: 47.5 mm; wave-guide size: 19.05 mm 9.525 m; flange plate size: 15 mm 22 mm 1.0 mm

applied in the microstrip antennas to suppress the surface wave propagation that improves antenna’s performance such as increasing the antenna gain and reducing back radiation [5, 6]. Whereas, as the common used components in radar and satellite communications system, the horn antenna with EBG material has been rarely reported on all kinds of literatures [7].

In this article, we mainly utilize the surface-wave suppression effect of the EBG structure to reduce the diffraction of horns. On the basis of this effect, an E-plane sectoral horn antenna with the mushroom-like EBG material is designed to reduce the horn’s diffraction and enhance its gain. Because of effective surface-wave suppression, the simulant and test results show that this sectoral horn has effectively reduced its back radiation and increased its gain.

2. THE ANALYSIS OF THE E-PLANE SECTORAL HORN WITH EBG MATERIAL

2.1.The Structure of the E-Plane Sectoral Horn With EBG Material

The traditional E-plane sectoral horn has obviously side-lobe on the E-plane and lower front-to-back ratio because of the diffraction on the E-plane sectoral horn’s mouth. So, we presented an E-plane sectoral horn with EBG material to reduce the diffraction.

The EBG sectoral horn is consisted of EBG material, traditional E-plane sectoral horn, and flange plate.

Figure 1 shows that the flange plate, which is covered with the EBG material, is attached to the horn antenna mouth. Because of the suppression of the surface-wave, the EBG sectoral horn has effectively reduced its back radiation and increased its main lobe gain.

2.2.The Structure of EBG Material

The EBG material used in the horn consists of patch, ground plate, metallic pin, and substrate, as shown in Figure 2.

Figure 2 The Structure of EBG material: (1) patch; (2) metallic pins; (3) ground plate; and (4) substrate

Figure 3 Comparison of the transmission coefficient results with and without the EBG material. [Color figure can be viewed in the online issue, which is available at www.interscience.wiley.com]

The operation mechanism of this EBG structure can be explained by an LC filter array: the inductor results from the current flowing through the metallic pins, and the capacitor due to the gap effect between the adjacent patches. The values of the inductor L, the capacitor C, the frequency , and the frequency band width, BW, are determined by the following formula (1)–(4) [8]:

where 0 is the permeability of free space, 0 is the permittivity of free space, and is the free space impedance which is 120 .

From formula (1)–(4), we can initially give the parameters of EBG material such as the width of patch, the gap of the neighboring patches etc. But these parameters are not very accurate. For example, this model does not consider the pin’s radius information. To accurately identify the band-gap region and understand its properties comprehensively, we used the CST soft to simulate and analyze the performance of the EBG sectoral horn. The EBG material we designed resonates at 12.3 GHz, has the following parameters:

r 2.2, h 1.575 mm, W 2.5 mm,

g 0.6 mm, rpin 0.3 mm

rpin is the radius of the metallic pin.

We adopt the patch antenna and microstrip method (PAMM) to analyze the difference of the transmission coefficient (S21) with and without EBG material, respectively, by using the CST software [9]. Figure 3 plots the S21 curves with and without EBG material. It is observed that a clear band gap can be noticed from

Figure 7 The comparative gain between the horn with and without EBG material. [Color figure can be viewed in the online issue, which is available at www.interscience.wiley.com]

back to the generator. It is indicated that using the EBG material cannot depress the total radiation efficiency.

Figure 7 is the horn’s contrastive data of the gain with and without EBG material from 11.7 to 14.0 GHz. The sign “f” and “*” represented the gain of the original horn without the EBG material and the horn with the EBG material, respectively. As the frequency increases, the gain has been improved and enhanced 1.4 dB at 13.0 GHz . It means that the horn with EBG has better performance in gain than the traditional horn.

3. EXPERIMENTAL

3.1. Fabrication of the EBG Sectoral Horn

As shown in Figure 8, a pair of smooth aluminium plates was welded on the horn’s mouth and the EBG material were cemented on the flange plate by the conductor glue.

3.2. Experimental Results

Figure 9 is the comparative results of the radiation pattern which were simulated and experimented at 12.3 GHz: The dashed line is the simulant results and the real line is the testing results. The two kinds of curves are almost overlapped and it means that the simulant results are consistent with the testing results.

Figure 9 The comparative radiation pattern (12.3 GHz):(a) E-plane pattern; (b) H-plane pattern. [Color figure can be viewed in the online issue, which is available at www.interscience.wiley.com]

4. CONCLUSION

In this article, an EBG structure is implemented in the design of E-plane sectoral horn to suppress the surface wave propagation and reduce the diffraction on the horn’s mouth. Compared to the traditional E-plane horn, the EBG horn demonstrates a better performance to improve about 1.0 dB on the gain, compress the beam width, and improve nearly 14.6 dB on the front-to-back ratio. This EBG horn technique can be used in various antenna applications such as mobile and satellite communications.

ACKNOWLEDGMENTS

This work was supported by 973 Program of China (No.2006CB302900). The authors thank Miss Leilei Yang for her kind contribution to this work.

REFERENCES

1.J.D. Kraus and R.J. Mzrhefka, Antenna, 2006.

2.M.S. Narasimhan and V. Venkateswara Rao, Radiation characteristics of corrugated E_plane sectoral horns, IEEE Trans Antennas Propag 3 (1973), 320 –327.

3.C. Granet and G.L. James, Design of corrugated horns: A primer, IEEE Antennas Propag Mag 47 (2005), 76 – 84.

4.E. Yablonovitch, Inhibited spontaneous emission in solid-state physics

and electronics, Phys Rev Lett 58 (1987), 2059 –2062.

5.D. Sievenpiper, High impedance electromagnetic surface with forbidden frequency band, IEEE Trans Microwave Theory Tech 47, (1999), 2059 –2074.

6.G.H. Huff and J.T. Bernhard, Improvements in the performance of microstrip antennas on finite ground planes through ground plane edge serration, IEEE Trans Microwave Wireless Compon Lett 12 (2002), 308 –310.

7.A.R. Weily and K.P. Esselle, Linear array of woodpile EBG sectoral horn, IEEE Trans Antennas Propag 54 (2006), 2263–2274.

8.D. Sievenpiper, L. Zhang, F.J. Broas, N.G. Alexopolous, and E. Yablonovitch, High-impedance electromagnetic surfaces with a forbidden frequency band, IEEE Trans Microwave Theory Tech 47 (1999), 2059 –2074.

9.H. Xu, Y. Lv, X. Luo, and C. Du, Method for identifying the surface wave frequency band-gap of EBG structures, Microwave Opt Technol Lett 49, (2007), 2668 –2672.

© 2008 Wiley Periodicals, Inc.

A COMPACT MEANDERING BANDPASS FILTER WITH DUAL PASSBAND PERFORMANCE FOR 2.4/5.7 GHZ WLANS

Hon Kuan

Department of Technology Electro-Optical Engineering, Southern Taiwan University, Taiwan; Corresponding author: q1893113@mail.ncku.edu.tw

Received 20 August 2007

ABSTRACT: In this letter, a compact dual-band bandpass filter (BPF) using the meandering stepped impedance resonators (MSIRs) for the wireless local area networks (WLANs) is proposed. The dual-band performance of the BPF is adjusted by the physical length ( ) and impedance ratio (K) of the MSIRs. The proposed BPF is designed and fabricated, showing good dual-passband responses at 2.4/5.7 GHz and a high isolation between the two passbands. The overall circuit size of the BPF is much smaller than the previous work. Good agreement with response of electromagnetic (EM) simulation and measurement is obtained.

© 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 969 –971, 2008; Published online in Wiley InterScience (www.interscience.wiley. com). DOI 10.1002/mop.23267

Key words: stepped impedance resonators (SIRs); dual-band; selectivity; filter

1. INTRODUCTION

Planar radio frequency (RF) and microwave filters are always important and essential components in modern wireless and mobile communication systems. Recently, dual-band bandpass filters (BPFs) have become very popular for the developed multi-service (multi-band) RF/microwave communication system, especially in the new developed wireless local area networks (WLANs) standards such as IEEE 802.11b/g (2.4 GHz) and IEEE 802.11a (5.2–5.8 GHz) specifications [1]. Many published papers have been widely studied in dual-band BPF design [1– 6]. Ryynanen et al. proposed the RF circuit by switching two bands in 900/1800 MHz [3]. However, this approach has disadvantages of large circuit sizes and high power consumptions. A cascade dual-band BPF using open-loop resonator was proposed [4], however, poor isolation between two passbands is introduced and too large circuit size. A low-loss dual-band BPF using folded open-loop ring resonators (OLRRs) was reported [5], however the tuning range of the dual-band using OLRRs was less in compared with that of the stepped impedance resonators (SIRs).

In past, SIRs are used to shift or suppress the higher order resonant modes [7], while some approaches also use the spurious frequencies of SIRs to create the second passband [1]. Sun and Zhu proposed a dual-band BPF using the coupled meandering SIRs (MSIRs) [6]. However, the circuit size and in-between isolation are still not good enough for requirements of the mobile WLANs. Additionally, a dual-band BPF with compact size, low loss, and high selectivity are much imperative demand in the WLANs.

In this letter, we propose a compact dual-band BPF using the coupled meandering stepped impedance resonators (MSIRs), which create two passbands located at 2.4/5.7 GHz through a single filter topology. It is shown that the designed dual-band BPF has good passband performances and high selectivity due to the transmission zeros located between two desired frequencies by using the set of coupled MSIRs. The theory and guidelines for selecting the geometric parameters of SIRs are clearly presented in next section. Finally, the compact dual-band BPF is designed, fabricated, and characterized.

Figure 1 Configuration of the proposed BPF. Gray area indicates the metallic