are less than 0.5 dB and smaller than 180 6 3, respectively, over a frequency range of 20–40 GHz. Figure 5 shows the die photograph of the integrated circuit, the chip size is 0.721.28 mm2including the RF probe pads. As it shows, the area of the balun that is enclosed by the dotted square is about one-third of the total chip area and the rest part is occupied by the conven- tional K-band two-stage LNA.
The prototype was contacted with RF probes to measure the noise figure, power gain, and input and output return loss as well. The measured Sparameters and noise figure are superim- posed in Figure 6. Figure 6(a) shows that the peak single-to-dif- ferential gain of the integrated circuit is 9.2 dB and minimum noise figure is about 5.1 dB at 24 GHz. The measured amplitude imbalance of the differential output ports is smaller than 1.0 dB and phase difference is less than 5 over the frequency range from 20 to 40 GHz, and they all are depicted in Figure 6(b).
Both the measured noise figure and input matching are slightly worse than simulation results, that is, because some parasitic resistive components have not been completely included in EM simulation and affect the practical input matching result. How- ever, other measured performances of the integrated circuit are still consistent with simulated results.
4. CONCLUSIONS
A new type of passive balun consisting of k/8 broadside- coupled lines and a short redundant transmission line is pro- posed to integrate with the conventional two-stage LNA as a low-noise module for single-in differential-out applications.
This miniaturized balun has not only the advantages of low insertion loss and keeping good amplitude and phase balances over a wide operation bandwidth but also occupies a smaller chip area than the tradition distributed-type balun. The mea- surement results of the active balun show that the amplitude imbalance of the balanced ports can be maintained less than 1.0 dB associated with the phase difference of 181 64within the operation bandwidth of 20 GHz. The comparison of the proposed circuit with some other published works is shown in Table 1. Because the proposed distributed balun exhibits the characteristics of low insertion loss and quite good amplitude and phase balances, the integrated subsystem can also achieve the smallest phase difference and amplitude imbalance and lowest power consumption as compared to the other published works. The size of the chip is only slightly larger than the cir- cuit, which uses lumped-element transformer structure, oper- ated at the same frequency band [3]. Furthermore, the noise figure and the power gain of the proposed circuit may be fur- ther improved in the same operation frequency, when more advanced IC fabrication technology, such as the 0.13 lm CMOS RFIC or the BiCMOS technology, is used.
ACKNOWLEDGMENTS
The authors wish to thank the Chip Implementation Center (CIC) of Taiwan for the chip fabrication. This work was supported in part by the National Science Council of Taiwan, Republic of China, under Project NSC97-2221-E-182-016-MY2.
REFERENCES
1. B. Welch, K.T. Kornegay, H.-M. Park, and J. Laskar, A 20-GHz low-noise amplifier with active balun in a 0.25-lm SiGe BICMOS technology, IEEE J Solid-State Circuits 40 (2005), 2092–2097.
2. B.-J. Huang, B.J. Huang, K.-Y. Lin, and H. Wang, A 2–40 GHz active balun using 0.13 lm CMOS process, IEEE Microwave Wireless Compon Lett 19 (2009), 164–166.
3. J.-F. Yeh, C.-Y. Yang, H.-C. Kuo, and H.-R. Chuang, A 24-GHz transformer- based single-in differential-out CMOS low-noise am- plifier, In: Proc. IEEE Radio Frequency Integrated Circuits Symp, 2009, pp. 299–302.
4. Y. Jin, M. Sporito, and J.R. Long, A 60 GHz-band millimeter- wave active balun with 65 phase error, In: Proc. 5th European Microwave Integrated Circuits Conf., 2010, pp. 210–213.
5. C.-I. Shie, Y.-H. Pan, K.-S. Chin, and Y.-C. Chiang, A miniatur- ized microstrip balun constructed with twok/8 coupled lines and a redundant line, IEEE Microwave Wireless Compon Lett 20 (2010), 663–665.
6. E. Adabi, B. Heydari, M. Bohsali, and A.M. Niknejad, 30 GHz CMOS low noise amplifier, In: Proc. IEEE Radio Frequency Inte- grated Circuits Symp, 2007, pp. 625–628.
7. J.-S. Goo, H.-T. Ahn, D.J. Ladwig, Z. Yu, T.H. Lee, and R.W.
Dutton, A noise optimization technique for integrated low-noise amplifier, IEEE J. Solid-State Circuits 37 (2002), 994–1002.
8. L. Belostotski and J.W. Haslett, Noise figure optimization of induc- tively degenerated CMOS LNAs with integrated gate inductors, IEEE Trans Circuits Syst I 53 (2006), 1409–1422.
VC2012 Wiley Periodicals, Inc.
COMPACT PRINTED COPLANAR WAVEGUIDE-FED ULTRA-WIDEBAND ANTENNA WITH MULTIPLE NOTCHED BANDS
Mohammad Mehdi Samadi Taheri, Hamid R. Hassani, and Sajad Mohammad Ali Nezhad
Electrical and Electronic Engineering Department, Shahed University, Tehran, Iran; Corresponding author:
[email protected] Received 9 November 2011
ABSTRACT:A compact multiband-notched printed ultra-wideband (UWB) coplanar waveguide (CPW)-fed slot antenna is presented. The band notched characteristic is achieved by creating quarter-wavelength stubs in the ground plane. These stubs act as stop-band filters along the feed line over certain narrow frequency bands. Addition of each stub to the antenna structure creates an extra independent notch band. Antenna with single, dual, triple, quadruple, and penta notch bands can be created by this technique. The notch bands can be chosen from practical frequency bands such as 3.5 GHz WiMAX, 5.2 and 5.8 GHz WLAN, 7.25–7.75 GHz for the downlink of X-band satellite communication systems, and ITU at 8.2 GHz band all within the UWB range. Each of the notch bands can be tuned in frequency independently. The antenna has a small size (24270.8 mm3), and almost stable
omnidirectional radiation pattern. The prototype of the antenna is fabricated, and the measured results are in good agreement with the simulations.VC 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 54:2121–2126, 2012; View this article online at
wileyonlinelibrary.com. DOI 10.1002/mop.26998
Key words:CPW feed; multinotched-bands; printed monopole slot antenna; ultra-wideband
1. INTRODUCTION
In recent years, due to the development of ultra-wideband (UWB) communication systems, covering 3.1–10.6 GHz band, a lot of researches have been carried out to design the UWB antenna. The printed antennas are good choice for such UWB systems because of their compactness, wide impedance band- width, high radiation efficiency, omnidirectional radiation pat- tern, low cost, and ease of fabrication [1].
Over the designated UWB frequency band, there are some narrow bands used by other communication systems, such as the
wireless local area network operating at 5.2 GHz (5.15–5.35 GHz) and 5.8 GHz (5.725–5.825 GHz) and worldwide interoper- ability for microwave access (WiMAX) at 3.5 (3.4–3.69 GHz ) and 5.8 GHz (5.25–5.825 GHz), the downlink frequency of X- band satellite communication systems at 7.25–7.75 GHz, and ITU band at 8.2 GHz (8.025–8.45 GHz). Therefore, it is desira- ble to design a UWB antenna with multiband-notched character- istics that rejects such interferences.
In the literature, several techniques have been reported to design printed UWB antennas with single band notch character- istics. This includes: use of a square-ring resonator [2], using an EBG structure [3], embedding a quarter-wavelength and a half- wavelength slot in the ground [4], and use of an inverted U- shaped slot in the feed line [5].
Recently, it is desirable to design multinotched band antenna.
In Ref. 6 parasitic strips are used on the radiator, and in Ref. 7 rectangular and L-shaped slits in the ground plane of the poly- gon slot antenna are cut to create two notched bands. In Ref. 8, notches at frequencies of 3.4 and 5.5 GHz are achieved by
etching two nested C-shaped slots in the radiating patch, while Ref. 9 has used two quarter-wavelength stubs attached to the ground plane. In the latter technique the presence of the stubs short out the radiation of the patch over the UWB range thereby creating a notch band. The antenna design reported in Ref. 9, due to the limitation of the spacing between the stubs, is not suitable for more than two notched bands.
Reports on printed antennas with multiple notch bands (more than two) are quite few. In Ref. 10 and 11, a printed coplanar waveguide fed (CPW) monopole UWB antenna with four slots on the radiating patch, giving notch bands at 3.5, 5.5, and 7.5 GHz, is reported. The third notch band is created by combina- tion of the third and fourth slots. In this technique, due to the space limitation on the patch the number of the notched bands is limited to three. In Ref. 12, combination of a meander shaped stub and two rectangular complementary split ring resonators on the feed line, and an inverted U-shaped slot on the patch is reported to create three notched bands at 3.5, 5.5, and 8.2 GHz.
In Ref. 13, by cutting a pair of hook-shaped slot out of the ground, etching an X shaped slot on the radiating patch, and using semioctagon-shaped resonator on the back plane, three notched bands at 3.5, 5.2, and 5.8 GHz is achieved. Each of the band notches reported in Ref. 12, 13 is produced by a different technique. Quadruple notched bands at frequencies of 2.4, 3.5, 5.5, and 8.7 GHz are achieved by loading stepped impedance resonators on the feed line of the UWB antenna [14].
Figure 1 Configuration of the proposed printed CPW-fed UWB slot antenna with one filtered band. (a) top view, (b) side view. [Color figure can be viewed in the online issue, which is available at wileyonlinelibrary.com]
Figure 2 The equivalent circuit model for the proposed UWB antenna with a single notched band. [Color figure can be viewed in the online issue, which is available at wileyonlinelibrary.com]
Figure 3 Simulated input impedance of the proposed UWB slot antenna with and without stub. [Color figure can be viewed in the online issue, which is available at wileyonlinelibrary.com]
From the literature review of above, one can notice that to increase the number of the notch bands, a new antenna design is required.
In this article, a compact simple to design multiband-notched printed CPW-fed UWB slot antenna is proposed. The filtering behavior is achieved by a unique and simple technique. It con- sists of removing sections from the lower parts of the ground plane of the original UWB slot antenna structure and in effect creating L-shaped stubs in the ground plane. Each L-shaped stub of quarter-wavelength acts as a stop-band filter along the CPW feed line that effectively stops the patch radiating at the desired notch center frequency. Using this technique dual, triple, quad- ruple, and penta band notch antenna can be designed. The pro- posed antenna is fabricated and the measured results are com- pared with the simulations. The simulation results are obtained through the software package Ansoft HFSS.
2. ANTENNA DESIGN
In the following, a printed CPW-fed slot antenna in which the radiating patch is in the shape of a flower, similar to that used in Ref. 15, is used to cover the UWB frequency range.
By removing a section from the bottom part of the slot in the ground plane, effectively creating a stub in the ground, a band notched behavior can be created over the UWB frequency range. The created stub acts as a stop-band filter that rejects a band of frequencies not to reach the patch antenna and radiating into the space, consequently resulting in a band notched charac- teristic. The geometry of the proposed CPW-fed UWB antenna Figure 4 Simulated input impedance of the printed UWB CPW-fed
slot antenna with a single stub for various stub lengths. [Color figure can be viewed in the online issue, which is available at wileyonlinelibrary.com]
Figure 5 Configuration of the proposed printed CPW-fed slot antenna with (a) triple notched-band, (b) penta notched-band, and (c) the fabri- cated penta notched-band antenna. [Color figure can be viewed in the online issue, which is available at wileyonlinelibrary.com]
Figure 6 Simulated reflection coefficient of the UWB printed CPW- fed slot antenna with single, dual, and triple notched-bands. [Color fig- ure can be viewed in the online issue, which is available at wileyonlinelibrary.com]
Figure 7 Simulated reflection coefficient of the printed UWB CPW- fed slot antenna with triple notched bands of various stub lengths. [Color figure can be viewed in the online issue, which is available at wileyonlinelibrary.com]
with a single notch band is shown in Figure 1. The antenna is printed on RT duroid 5870 substrate with a compact size of 24 27 mm2, thickness of 0.8 mm, relative permittivity of 2.33, and loss tangent of 0.0012. The flower-shaped radiating patch consists of two semicircles which are attached to each other and is fed by a CPW line. The surrounding slot is in the shape of a rectangle. The parameters of the proposed UWB antenna with a single notched band are as follows:
R1¼3:5mm;R2¼7mm;WS¼27mm;WF¼2:5mm;
W1¼9:8mm;W2¼23mm;W3¼2 mm;LF¼5:8mm;LS¼24mm;LG¼5:3mm;
L1¼16mm;L2¼9mm;L3¼7mm;andg¼0:45mm As seen in Figure 1, the total length of the created stubLS1
¼ L2 þ L3 ¼ 16 mm is of quarter-wavelength at the desired center frequency 3.5 GHz of the filtered band.
Based on the filtering effect of the stub, one can consider an equivalent circuit model for the proposed UWB antenna, as shown in Figure 2. The UWB behavior of the antenna can be considered as several adjacent resonances that can be presented by several parallel RLC circuit connected to each other [8]. The open ended stub can be modeled as shunt quarter-wavelength open circuited transmission line that short circuit the antenna at the relevant frequency.
Figure 3 shows the simulated antenna input impedance. As expected, the antenna input impedance is nearly zero around the notch center frequency which confirms the validity of the above equivalent circuit. As a comparison, the simulated input imped- ance of the original UWB antenna is also shown in Figure 3.
Results show that the addition of such a stub has little effect on the input impedance of the original UWB antenna over the pass- band frequencies. A parametric study on the effect of the stub Figure 8 Simulated reflection coefficient of the printed CPW-fed slot
antenna with one to five notched-bands. [Color figure can be viewed in the online issue, which is available at wileyonlinelibrary.com]
Figure 9 Simulated and measured reflection coefficient of the printed UWB CPW-fed slot antenna with penta notched-bands. [Color figure can be viewed in the online issue, which is available at wileyonlinelibrary.com]
Figure 10 Simulated current distribution on the printed UWB CPW-fed slot antenna with penta notched-band at frequencies of (a) 3 GHz, (b) 3.5 GHz, (c) 5.2 GHz, (d) 5.8 GHz, (e) 7.5 GHz, and (c) 8.2 GHz. [Color figure can be viewed in the online issue, which is available at wileyonlinelibrary.com]
length LS1is given in Figure 4. It is seen that by reducing the stub length, the center frequency of the filtered band increases and vice versa.
The above mentioned technique can be implemented to cre- ate multinotched-bands in the UWB frequency rang. Figure 5 (a) shows the geometry of the proposed UWB antenna with three notched-bands at frequencies of 3.5, 5.2, and 5.8 GHz.
Unlike the previous works of Ref. 10–13, in this design all the band notches are created by a single unique technique.
Finally, using the above technique the UWB antenna with penta notched bands is designed and fabricated. Figure 5 (b) and (c) shows the relevant antenna. The proposed antenna can reject frequencies such as 3.5, 5.2, and 5.8 GHz as well as 7.5 and 8.2 GHz bands. The latter two bands, the satellite communication and ITU bands may cause interferences with the UWB opera- tion, thus this structure can reject such potential interferences.
The total length of any of the L-shaped stubs,LS1toLS5, can be obtained approximately from the following formula:
L¼ c 4f ffiffiffiffiffiffiffi
erþ1 2
q (1)
in whicher,c,andfare dielectric constant, the velocity of light in free space, and the center frequency of the desired notched- bands, respectively.
The total length of each of the stubs at notch center frequen- cies of 3.5, 5.2, 5.8, 7.5, and 8.2 GHz areLS1¼16 mm,LS2¼ 13 mm,LS3¼10 mm,LS4¼8.5 mm, andLS5¼7 mm, respec- tively. These dimensions confirm the validity of formula (1). It needs to be mentioned that the width of the stubs and the spac- ing between any two adjacent stubs are 0.3 mm.
To reduce the coupling between any of the two stubs related to the adjacent notched-bands, and in effect improving the qual- ity of the band rejection, the placement of these two stubs should be such that one stub is on one side while the other is on the other side of the patch. For instance,LS2related to 5.2 GHz notch band is placed on the right hand while LS3related to 5.8 GHz is placed on the left hand side of the antenna.
3. RESULTS AND DISCUSSION
Figure 6 shows the simulated reflection coefficient of proposed UWB CPW-fed slot antenna with single, dual, and triple notched bands. As a comparison the reflection coefficient of the original UWB antenna is also depicted in Figure 6. It is evident that when a stub is added, the previous notch band is almost unaffected confirming that notch bands are almost independent of each other.
The simulated reflection coefficient of the proposed antenna with triple notched bands for various stub length, LS1–LS3, is shown in Figure 7. It is seen that tuning of the notch center fre- quency can easily be achieved by changing the relevant stub length. Based on the value of the notch center frequency and the stub length, one can confirm the validity of formula (1).
The simulated reflection coefficient of the proposed antenna with one to five notched-bands is shown in Figure 8. Similar to the triple notch design, results show that when the number of stubs increases, no significant effect is seen on the previous notch bands.
The simulated and measured reflection coefficient of the pro- posed UWB antenna with penta notched-band is shown in Fig- ure 9. It is seen that most of the notched bands are sharp and narrow, with good band rejection quality. This means that the quality factor of the filtered bands is high. Also there is a good
agreement between the simulated and measured reflection coefficients.
To better understand the band notch behavior of the antenna, the simulated surface current distribution of the proposed Figure 11 Measured radiation pattern of the proposed antenna in dB at various frequencies of (a) 3 GHz, (b) 4.5 GHz, and (c) 9 GHz. Solid line represents H-plane (x–zplane), and dashed line represents E-plane (y–zplane). [Color figure can be viewed in the online issue, which is available at wileyonlinelibrary.com]
antenna is presented in Figure 10. From Figure 10 (a), it is seen that, at frequency of 3 GHz, all the stubs are inactive and the current is only strong on the radiating patch, while as shown in Figure 10 (b) to (f) the current distribution is strong in the stubs related to the relevant notched-bands, meaning that the radiating patch is being filtered by the stub at the desired notch frequency band. As the current is maximum at one end, and minimum at the other end of the stub, it is obvious that the stubs are of quar- ter wavelength, confirming the validity of formula (1).
The measured radiation patterns of the antenna in both E- and H-planes at three passband frequencies of 3, 4.5, and 9 GHz are shown in Figure 11. As expected the proposed antenna has a good omnidirectional radiation pattern in the H-plan (x–z plane) and bidirectional radiation pattern in the E-plane (y–zplane).
The measured antenna peak gain is shown in Figure 12. The reduction in the antenna gain at the notch bands is significant and confirms the band rejection behavior of the proposed antenna.
It can be shown through simulation that the antenna radiation efficiency is higher than 90% over the passband frequencies over the UWB range. From the above results it is seen that the antenna performance over the passband frequencies is unaffected both in terms of reflection coefficient and radiation pattern.
4. CONCLUSION
The design of UWB printed CPW-fed slot antenna with multi- notch bands is presented. Band notched characteristic is pro- duced by removing a section from the bottom of the ground plane and in effect creating quarter-wavelength L-shaped stub in the ground plane. The notch achieved by this technique has a sharp and almost narrow band rejection behavior meaning that the quality factor of the proposed filter is quite high. In this work, design of a single, dual, triple, quadruple, and penta notched band antenna at frequencies of 3.5, 5.2, 5.8, 7.5, and 8.2 GHz is given. The approach is capable of designing an antenna with even more number of notched bands. The proposed antenna has an almost stable and omnidirectional radiation pattern.
REFERENCES
1. B. Ahmadi and R. Faraji-Dana, A miniaturised monopole antenna for ultra-wide band applications with band-notch filter, IET Micro- wave Antennas Propag 3 (2009), 1224–1231.
2. W.-J. Lui, C.-H. Cheng, and H.-B. Zhu, Improved frequency notched ultrawideband slot antenna using square ring resonator, IEEE Trans Antennas Propag 55 (2007), 2445–2450.
3. M. Yazdi and N. Komjani, Design of a band-notched UWB monopole antenna by means of an EBG structure, IEEE Antennas Wireless Propag Lett 10 (2011), 170–173.
4. Y.D. Dong, W. Hong, Z.Q. Kuai, and J. X. Chen, Analysis of pla- nar ultrawideband antennas with on-ground slot band-notched structures, IEEE Trans Antennas Propag 57 (2009), 1886–1893.
5. L.-N. Zhang, S.-S. Zhong, X.-L. Liang, and C.-Z. Du, Compact omnidirectional band-notch ultra-wideband antenna, Electron Lett 45 (2009), 659–660.
6. K.S. Ryu and A. A. Kishk, UWB antenna with single or dual band-notches for lower WLAN band and upper WLAN band, IEEE Trans Antennas Propag 57 (2009), 3942–3950.
7. L.-H. Ye and Q.-X. Chu, 3.5/5.5 GHz dual band-notch ultra-wideband slot antenna with compact size, Electron Lett 46 (2010), 325–327.
8. Q.-X. Chu and Y.-Y. Yang, A compact ultrawideband antenna with 3.4/5.5 GHz dual band-notched characteristics, IEEE Trans Antennas Propag 56 (2008), 3637–3644.
9. M. M. Samadi Taheri, H.R. Hassani, and S. Mohammad ali nez- had, UWB printed slot antenna with Bluetooth and dual notch bands, IEEE Antennas Wireless Propag Lett 10 (2011), 255–258.
10. N.D. Trang, D.H. Lee, and H. C. Park, Compact printed CPW-fed monopole ultra-wideband antenna with triple subband notched characteristics, Electron Lett 46 (2010), 1177–1179.
11. D. Trang, D. H. Lee, and H. C. Park, Design and analysis of com- pact printed triple band-notched UWB antenna, IEEE Antennas Wireless Propag Lett 10 (2011), 403–406.
12. D.-O. Kim and C.-Y Kim, CPW-fed ultra-wideband antenna with triple-band notch function, Electron Lett 46 (2010), 1246–1248.
13. W.T. Li, X.W. Shi, and Y.Q. Hei, Novel planar UWB monopole antenna with triple band-notched characteristics, IEEE Antennas Wireless Propag Lett 8 (2009), 1094–1098.
14. Y. Zhang, W. Hong, C. Yu, J.-Y. Zhou, and Z.-Q. Kuai, Design and implementation of planar ultra-wideband antennas with multi- ple notched bands based on stepped impedance resonators, IET Microwave Antennas Propag 3 (2009), 1051–1059.
15. M. Koohestani and M. Golpour, Very ultra-wideband printed CPW-fed slot antenna, Electron Lett, 45 (2009), 1066–1067.
VC2012 Wiley Periodicals, Inc.
MEASUREMENT AND MODELING OF A UHF-RFID SYSTEM IN A METALLIC CLOSED VEHICLE
Leire Azpilicueta,1Francisco Falcone,1Jose Javier Astrain,2 Jesus Villadangos, 2I. J. Garcı´a Zuazola,3Hugo Landaluce,3 Ignacio Angulo,3and Asier Perallos3
1Department of Electrical and Electronic Engineering, Public University of Navarre, 31006 Pamplona, Spain; Corresponding author: [email protected]
2Department of Mathematical and Computer Engineering, Public University of Navarre, 31006 Pamplona, Spain
3Deusto Institute of Technology (DeustoTech), University of Deusto, 48007 Bilbao, Spain
Received 15 November 2011
ABSTRACT:In this work, the characteristics radiopropagation of a wireless system within an indoor vehicle is presented. An analysis of the physical radio channel propagation inside a van full of dielectric buckets is presented based on three-dimensional ray launching in house code. Simulation as well as measurement results from a real in-vehicle scenario confirm the topological dependence and impact on a RFID system is shown.VC 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 54:2126–2130, 2012; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27010
Key words:3D ray launching; RFID system; intravehicular wireless channel
Figure 12 The measured peak gain of the proposed antenna with penta notched bands versus frequency. [Color figure can be viewed in the online issue, which is available at wileyonlinelibrary.com]
