диафрагмированные волноводные фильтры / c97a4f61-945d-4212-adfa-315690707ae2

need to be further investigated. Finally, when the aperture length R1 is adjusted to 26 mm and r1 is 13 mm, a good impedance matching for the ultrawide bandwidth was achieved in this study. Figure 5 shows the simulated field distributions on the slot region at different resonating frequencies. The current distribution demonstrates that the proposed antenna can generate multiple resonating modes to achieve an UWB.

3. MEASURED AND NUMERICAL RESULTS

In this study the proposed antenna shown in Figure 2 was constructed and tested. Figure 6(a) shows the photograph of the actual folded transmission line and the proposed antenna. The folded antenna was printed on two sides of a 1.6 mm thick FR4 substrate with a ground size of 30.3 mm 40 mm. The geometric sizes for the tapered-curved slot antenna folded with two half-ellipse-shaped planes were R1 r1 (26 mm 13 mm) and R2 r2 (15 mm 8.25 mm), respectively. The folded transmission line fed from the edge was 10 mm long with a sidewall strip width of 1.6 mm, the same as the substrate’s thickness, and the gap distance g of the folded CPW was 0.3 mm.

The experiments were performed using an Agilent HP8363PNA network analyzer. The simulation was performed using HFSS software. The SMA connector was also included in the simulation model. Figure 6(b) shows the measured and simulated reflection coefficient of the folded UWB antenna. When comparing the measured and simulated results, our findings show that the measured bandwidth of the folded slot antenna ranges from 2.87 GHz to 11 GHz. The measured bandwidth is more than 8.13 GHz with a reflection coefficient of less than10 dB. The peak resonant points are at 3.11, 4.43, 7.10, 8.92, and 10.31 GHz, respectively. The simulated results show an 8 GHz bandwidth, which ranges from 3 GHz to 11 GHz, and the peak resonant points are at 3.23, 3.98, 6.35, 8.68, and 10.13 GHz, respectively. The difficulties of manufacturing this antenna result in some unavoidable errors at the resonating frequencies and some shift in frequencies, however, the behavior of the simulated and measured results are similar.

Figure 7 shows the peak gains of the measured folded slot antenna. The antenna gain was measured in the anechoic chamber of NTUST, Taiwan, using a standard double-ridge horn antenna (EMCO 3115). Our findings indicate that the gain of the UWB antenna increases in an approximately linear fashion, but there is some variation over the entire bandwidth from 3 GHz to 10 GHz, reaching the maximum at 10 GHz. The maximum gain is about 9 dBi and the minimum gain is about 3 dBi.

The radiation patterns for the novel folded slot antenna were also investigated. The antenna was measured at both vertical and horizontal polarization on the E-plane (XZ-plane) and H- plane (YZ-plane). Figure 8(a) shows the measured E-plane (XZplane) radiation patterns for the proposed folded slot antenna at 3 and 7 GHz, respectively. Figure 8(b) shows the measured H- plane (YZ-plane) radiation patterns at 3 and 7 GHz, respectively. The measured radiation patterns on the E-plane and H-plane are nearly omni-directional at 3 and 7 GHz, respectively, and the nulls appear at higher frequency bands. The patterns seem to be slightly asymmetrical because of the folding.

4. CONCLUSIONS

This article presented a novel planar folded type antenna with curved radiating slots fed by a folded CPW transmission line for UWB system applications. The measured results confirm that the folded transmission line remains a 50-X transmission line. The performance of the proposed folded antenna was theoreti-

cally investigated using HFSS software. To validate the proposed design, this study performed some parameter measurements. The experimental results compared with the simulation results demonstrated that the folded slot antenna preserves the UWB characteristics.

ACKNOWLEDGMENTS

The authors are grateful to the National Center for High-perform- ance Computing for the computer time and the use of the facilities.

REFERENCES

1.Federal Communications Commission, Authorization of ultra-wide- band technology, First Note and Order (FCC 02-48), Washington, DC, Feb. 14, 2002.

2.S. Roy, J.R. Foerster, V.S. Somayazulu, and D.G. Leeper, Ultrawideband radio design: the promise of high-speed, short-range wireless connectivity, Proc IEEE 92 (2004), 295–311.

3.W.S. Lee, D.Z. Kim, K.J. Kim, and J.W. Yu, Wideband planar monopole antennas with dual band-notched characteristics, IEEE Trans antennas Propag 54 (2006), 2800–2802.

4.X.L. Liang, S.S. Zhong, W. Wang, and F.W. Yao, Printed annular monopole antenna for ultra-wideband applications, Electron Lett 42 (2006), 71–72.

5.C.H. Luo, C.M. Lee, W.S. Chen, C.H. Tu, and Y.Z. Juang, Dual band-notched ultra-wideband monopole antenna with an annular CPW-feeding structure, Microwave Optical Technol Lett 49 (2007), 2376–2378.

6.J.Y. Sze and K. L. Wong, Bandwidth enhancement of a microstrip- line-fed printed wide-slot antenna, IEEE Trans Antennas Propag 49 (2001), 1020–1024.

7.J.Y. Chiou, J.Y. Sze, and K.L. Wong, A broad-band CPW-fed strip-loaded square slot antenna, IEEE Trans Antennas Propag 51 (2003), 719–721.

8.R. Chair, A.A. Kishk, and K.F. Lee, Ultrawide-band coplanar waveguide-fed rectangular slot antenna, IEEE Antennas Wireless Propag Lett 3 (2004), 227–229.

9.C.W. Chiu and C.S. Li, A CPW-Fed band-notched slot antenna for UWB applications, Microwave Opt Technol Lett 51 (2009), 1587–1591.

10.J.S. Sun, Y.C. Lee, and S.C. Lin, New design of a CPW-fed ultrawideband slot antenna, Microwave Opt Technol Lett 49 (2007), 561–564.

11.W.C. Johnson, Transmission Lines and Networks, McGraw-Hill, New York, NY, 1963, p 155.

VC 2010 Wiley Periodicals, Inc.

AN EMBEDDED MULTILAYER LTCC BAND-PASS FILTER USING U-TYPE STEPPED IMPEDANCE RESONATOR

Zhigang Wang, Peng Wu, Bo Yan, Yunchuan Guo, Ruimin Xu, and Weigan Lin

School of Electronic Engineering, University of Electronic Science and Technology of China, Chengdu 610054, People’s Republic of China; Corresponding author: zgwang@ee.uestc.edu.cn or wangzhigang19791@163.com

Received 5 November 2009

ABSTRACT: This article proposes a compact multilayer band-pass filter based on low-temperature co-fired ceramic (LTCC) technology. The filter is constructed using U-type stepped impedance resonators (SIR) with microstrip input and output ports. To validate the proposed filter, a three-order X-band Chebyshev band-pass filter is developed and verified by full-wave simulation. The proposed filter is fabricated using multilayer LTCC technology and measured using vector network analyzer (VNA). Covering area of the fabricated band-pass filter is only

Figure 1 The block diagram of LO branch in LTCC transceiver module

15.3 6.7 mm2 (including via fences). The filter exhibits an insertion loss of lower than 1.8 dB with a 3.2% bandwidth at a center frequency of 9.5 GHz, and the return loss is better than 10 dB in the pass-band.

VC 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52: 1877– 1880, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.25352

Key words: band-pass filter; LTCC; U-type SIR; multilayer configuration

1. INTRODUCTION

Swift development of wireless and mobile communications requires more small size and high-performance microwave filters in many communication systems. Traditional microwave filters are designed commonly based on printed circuit board technology. Obviously, these filters have large size for modern systems. Thus, reducing size of microwave filters has been a hotspot of research. Multilayer technology using low-temperature co-fired ceramic (LTCC) technology gives a new design conception and method of solving these problems [1, 2]. By embedding diversified resonators into multilayer substrates and three-dimensional (3D) structure, LTCC technology offers opportunity to realize very compact filters. When the operating frequency is low, filters based on LTCC technology are usually implemented using LC elements. With increasing of frequency, parasitic effects deteriorate performance of such filters. So, coupling resonators of distributed type and cavity structures are usually used for these filters. Many contributions [3–7] have dealt with the development of filters-based LTCC technology.

In Ref. 7, a miniature embedded multilayer interdigital bandpass filter is proposed. The fabricated filter has quite compact size. However, the insertion loss of the filter is comparatively high for parasitic effect of grounded vias in resonators. To reduce insertion loss, a U-type half-wavelength SIR band-pass filter is proposed in this letter. The designed filter has the same function

as that in Ref. 7, suppressing fundamental and harmonic components of local oscillator (LO) signal in a LTCC transceiver module, as shown in Figure 1. On the basis of the proposed idea, a three-order Chebyshev band-pass filter is developed. Good agreement between simulated and measured response is observed.

2. FILTER DESIGN

The structure of typical U-type SIR is shown in Figure 2. For the U-type SIR, infinite number of resonant frequencies exist. Each resonance has either a symmetric (even mode) or an antisymmetric (odd mode) voltage distribution on the resonator. The fundamental resonance occurs in the odd mode, and the first higher order resonance in the even mode, and so forth. The conditions for determining the resonance frequencies of an SIR are given as [8]

where R is the impedance ratio of the U-type SIR and defined as

When R ¼ 1, h1 þ h2 ¼ p/2 at f0. It can be seen from Eqs.

(1) and (2) that the resonance frequencies of an SIR can be tuned by changing the value of R and the lengths of high-imped- ance and low-impedance segments. A simple root-searching program can be employed to calculate the resonant frequencies of the structure.

The configuration of the proposed filter is shown in Figure 3, which consists of three U-type SIR half-wavelength resonators. Figure 3(a) is the cross section, and Figure 3(b) is the top view. The design procedures of the filter are the same as those for conventional parallel-coupled BPF in Ref. 9, which is based on EM simulation extraction of external quality factor Qe and coupling coefficient Kij. First, Parameters such as external quality factor Qei, Qeo, and coupling coefficients Kij are as [9]

where gis are the element values of Chebyshev low-pass prototype filter, FBW is the fractional bandwidth, and n is the order

Figure 3 Configuration of the embedded LTCC filter: (a) Cross section. (b) Top view

of the filter. The coupling coefficient is used to determine the line gap between two resonators. Using the full-wave electromagnetic (EM) simulator HFSS, the coupling coefficient can be calculated as:

where fa and fb are the low and high resonant frequencies of the transmission responses. So the relationships between coupling coefficient and gap of resonators can be gained. Positions from the resonators to the input/output ports microstrip can be used to determine external quality factors. The relationships between external quality factor and position of input/output ports microstrip also can be gained by EM simulation extraction.

The designed filter is used to suppress the leaking fundamental and third-order harmonic components. A three-order U-type SIR Chebyshev band-pass filter is developed to meet the following specifications: (1) center frequency: 9.5 GHz; (2) bandwidth: 600 MHz. According to formulas (4), the parameters (Qe and Kij) of bandpass prototype are obtained as follows: Qei ¼ Qeo ¼ 10, K12 ¼ K23 ¼ 0.086.

The substrate of LTCC transceiver module has thirteen layers. Grid-ground structure is buried at the fourth and sixth metal layer, as grounds of microstrip and resonators. Band-pass

filter is embedded into the upper five layers, as shown in Figure 3. All of the resonators are embedded into LTCC substrate and placed at different layers. The amount of coupling for each resonator is controlled by the space between them, and the Qe is decided by positions from the resonators to the input and output ports’ microstrip. As a result, the radiation loss and volume of this filter are reduced remarkably.

Further more, a fence structure, which is formed by metalfilled vias, is set around the band-pass filter. This is based on consideration as follows: multilayer structure is helpful for reducing size, but it also brings problems caused by complicated EM environment. To avoid electromagnetic interference (EMI) between band-pass filter and other circuits in this module, a fence structure, which connected with the buried ground, is used. The magnitude distribution of E-field is calculated, as shown in Figure 4. It indicates that the EM energy of band-pass filter is mostly restricted inside the fence structure.

The establishment of relationship between physical dimension and parameter (Qe and Kij) is the key process in filter’s design. Using model which is founded in EM software (HFSS), the relationship can be gotten conveniently by simulation. After the initial physical parameters of filter are determined, and Ansoft HFSS is used to simulate and optimize the filter. The final structure dimensions are confirmed as listed in Table 1.

3. FABRICATION AND MEASUREMENTS

The filter is fabricated in a 13-layered DP943 LTCC substrate, of which the relative permittivity is about 7.2 (10 GHz), loss tangent is 0.0009, and thickness of each layer is 0.127 mm. Only the upper five layers are used, another eight layers are stacked to fit with the module’s configuration. The metallic part is fabricated by gold. Photograph of the filter is shown in Figure 5. The covering area of the filter is only 15.3 6.7 mm2 (include via fences).

S-parameters are measured using Agilent E8363B vector network analyzer (VNA). The simulated and measured S-parame- ters of the filter are shown Figure 6. It can be seen from Figure 6 that the operating bandwidth of measurement results is smaller than that of simulation results, insertion loss is larger, and return loss is worse; these could be attributed to tolerance of manufacture and relativity permittivity, material and radiation loss. In despite of these, the full-wave EM simulation (HFSS) and measurement results still have a good agreement. The filter exhibits an insertion loss of lower than 1.8 dB with a 3.2% bandwidth at a center frequency of 9.5 GHz, which include the effect of two SMA connectors, and the return loss is better than 10 dB in the passband.

Figure 5 Photograph of the LTCC band-pass filter

Figure 6 Simulated and measured S parameters of the LTCC bandpass filter

4. CONCLUSION

In this letter, an embedded multilayer LTCC U-type SIR bandpass filter has been presented. The filter is fabricated using three U-type SIR resonators, and the resonators are placed at different layers. This compact filter is used in LTCC transceiver module to suppress unnecessary frequency components in LO branch. According to validation, measured results are in good agreement with simulated results. Covering area of the fabricated band-pass filter is only 15.3 6.7 mm2 (including via fences).

ACKNOWLEDGMENTS

This work was supported by National Nature Science Foundation of China under Grants 60671028, 60701017, and 60876052.

REFERENCES

1.C.Q. Scrantom and J.C. Lawson, LTCC technology: Where we are and where we’re going-II, IEEE Int Microw Symp Dig, Baltimore, MD (1998), 193–200.

2.L. Xia, R.M. Xu, and B. Yan, LTCC Interconnect modeling by support vector regression, Prog Electromagn Res PIER 69 (2007), 67–75.

3.Z.G. Wang, P. Li, R.M. Xu, and W.G. Lin, A compact X-band receiver front-end module based on low temperature co-fired ceramic technology, Prog Electromagn Res PIER 92 (2009), 167–180.

4.J. H. Lee, S. Pinel, J. Papapolymerou, J. Laskar, and M. M. Tentzeris, Low-loss LTCC cavity filters using system-on package technology at 60 GHz, IEEE Trans Microw Theory Tech 53 (2005), 3817–3824.

5.L.K. Yeung and K.-L. Wu, A compact second-order LTCC bandpassfilter with two finite transmission zeros, IEEE Trans Microw Theory Tech 51 (2003), 337–341.

6.J.H. Lee, N. Kidera, G. DeJean, S. Pinel, J. Laskar, and M.M. Tentzeris, A V-band front-end with 3-D integrated cavity filters/ duplexers and antenna in LTCC technologies, IEEE Trans Microw Theory Tech 54 (2006), 2925–2937.

7.Z.G. Wang, B. Yan, R.M. Xu, and W.G. Lin, A miniature X-band embedded multilayer bandpass filter using LTCC technology, Microw Opt Technol Lett 51 (2009), 1722–1725.

8.M. Makimoto and S. Yamashita, Bandpass filters using parallelcoupled stripline stepped impedance resonator, IEEE Trans Microw Theory Tech MTT-28 (1980), 2925–2937.

9.J.S. Hong and M.J. Lancaster, Mircrostrip filters for RF/microwave applications, Wiley, New York, 2001.

VC 2010 Wiley Periodicals, Inc.

A NOVEL BAND REJECTION FILTER OF TRANSMISSION LINE TYPE USING DOUBLE SPUR-LINES

Soon-Young Eom1 and Ic-Pyo Hong2

1 Antenna Research Team, Electronics and Telecommunications Research Institute (ETRI), Korea; Corresponding author: syeom@etri.re.kr

2 Department of Information and Communication Engineering, KongJu National University, Korea

Received 5 November 2009

ABSTRACT: This letter presents a novel band rejection filter (BRF) using a pair of spur-lines or double spur-lines with an opposite direction, which is embedded in a transmission line. The slot length (L1) of double spur-lines determines a rejection band and the distance (L2) between the end points of each spur-line determines the position of a pass band, which is at the left or right side of a rejection band, respectively. That is, if L2 is shorter than L1, the right side of a pass band can be properly suppressed, otherwise if L2 is longer than L1, the left side of a pass band can be suppressed. Two novel kinds of BRFs were realized at Ku-band using soft Teflon substrate to verify the validity of the proposed structure. The measured performance was well agreed with the simulated one. VC 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52: 1880–1883, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ mop.25351

Key words: band rejection filter; double spur-lines; transmission line

1. INTRODUCTION

The modern microwave and satellite communication systems are expanding rapidly, and the new filters, diplexers, and multiplexers must satisfy high performances, small size, and