ACKNOWLEDGMENTS
The authors are very grateful for the support from National Chip Implementation Center (CIC), Taiwan, for chip fabrication, and Dr. G.W. Huang of the Nano-Device Laboratory (NDL), Taiwan, for high-frequency measurements.
REFERENCES
1. T. Song, H.S. Oh, E. Yoon, and S. Hong, A low-power 2.4-GHz current-reused receiver front-end and frequency source for wireless sensor network, IEEE J Solid State Circuits 42 (2007), 1012–1022. 2. J.A.M. Ja¨rvinen, J. Kaukovuori, J. Ryyna¨nen, J. Jussila, K. Kive-ka¨s, M. Honkanen, and K.A.I. Halonen, 2.4-GHz receiver for sen-sor applications, IEEE J Solid State Circuits 40 (2005), 1426–1433.
3. D.H. Chae, K.H. Han, K.S. Lim, K.H. Seo, K.H. Won, W.D. Cho, and S.S. An, Power saving mobility protocol for sensor network, IEEE Proceedings of Software Technologies for Future Embedded and Ubiquitous Systems, 2004, pp. 122–126.
4. J.H. Chang and L. Tassiulas, Maximum lifetime routing in wireless networks, IEEE Trans Network 12 (2004).
5. V. Peiris, C. Arm, S. Bories, et al., A \ill\V 433/868MHz 25kb/s-FSK 2kb/s-OOK RF transceiver SoC in standard digital 0.18 lm CMOS, International Solid State Circuits Conference, San Francisco, CA, February 2005, pp. 258–259.
6. D.C. Daly and A.P. Chandrakasan, An energy-efficient OOK trans-ceiver for wireless sensor networks, IEEE J Solid State Circuits 42 (2007), 1003–1011.
7. R.G. Meyer and W.D. Mack, A 1-GHz BiCMOS RF front-end integrated circuit, IEEE J Solid State Circuits 29 (1994), 350–355. 8. T.K. Nguyen, N.J. Oh, V.H. Le, and S.G. Lee, A low-power
CMOS direct conversion receiver with 3dB NF and 30-kHz flicker-noise corner for 915-MHz band IEEE 802.15.4 ZigBee standard, IEEE J Solid State Circuits 54 (2006), 735–741.
9. T.K. Nguyen, V. Krizhanovskii, J. Lee, S.K. Han, S.G. Lee, N.S. Kim, and C.S. Pyo, A low-power RF direct-conversion receiver/ transmitter for 2.4-GHz-Band IEEE 802.15.4 standard in 0.18-lm CMOS technology, IEEE J Solid State Circuits 54 (2006), 4062–4071.
10. F. Beffa, R. Vogt, W. Bachtold, E. Zellweger, and U. Lott, A 6.5-mW receiver front-end for bluetooth in 0.18-lm CMOS, IEEE RFIC Symp Dig, Seattle, WA (2002), 391–394.
VC2009 Wiley Periodicals, Inc.
A NOVEL SHORT LENGTH HALF-WIDTH
MICROSTRIP LEAKY WAVE ANTENNA
WITH SUPPRESSED BACK LOBES
Yi-Lin Chiou, Jin-Wei Wu, Jie-Huang Huang, and Christina F. Jou
Department of Communication Engineering, National Chiao Tung University, 1001 University Road, Hsinchu, Taiwan 300, Republic Of China; Corresponding author: [email protected]
Received 27 March 2007
ABSTRACT: A novel short half-width microstrip leaky wave antenna (MLWA) with suppressed back lobes is introduced. The design contains an oblique shape termination and a linked square metal with a grounded via hole. The oblique shape termination changes the direction of the reflected wave, and a linked square metal with a grounded via hole guides the remainder power of the reflected wave to the ground plane. As a result, the large back lobe of the short half-width MLWA could be suppressed. The measured results show that the proposed design (length of only 1k0) improves the back lobes by 9 dB at 4.7 GHz
compared with the original half-width MLWA.VC 2009 Wiley
Periodicals, Inc. Microwave Opt Technol Lett 51: 3024–3026, 2009;
Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24805
Key words: half-width; microstrip leaky wave antenna; reflected wave; back lobe
1. INTRODUCTION
The microstrip leaky wave antennas (MLWA) was first con-structed by Menzel in 1979 [1], using an asymmetric feed line to excite the first higher order mode (TE01mode) and adding slits
on the antenna to suppress the fundamental mode. The complex propagation constant of the leaky mode was discovered subse-quently by Oliner and Lee [2]. The traveling wave in the MLWA would leak power because of a small attenuation constant. In practical applications of the MLWA, it has advantages of simple fabrication, low-profile, narrow beam, and frequency scanning capability. MLWA is suitable for scanning work in the future. The length of MLWA, numbers of wavelength (usually 5k0), is
always too long to be applied. A short length (<5 k0) MLWA
cannot leak the power efficiently, and the remainder power will reflect at the open structure end [3]. Consequently, the reflected wave produces a large back lobe in the opposite direction of main beam. Several researches were studied [4–6] to suppress the back lobe. By using an array topology [4] or a taper-loaded antenna end [5] has been developed. Creating a second-radiated path, a two-directional scanned MLWA with aperture-coupled patch antenna arrays has been investigated in Ref. 6.
Recently, one half of the width of the MLWA has been stud-ied in Ref. 7, it’s called the ‘‘half-width’’ MLWA. Based on the fact that the first higher order mode of the microstrip line is an odd mode, a phase reversal, or null, appears along the centerline of the antenna. The width of conventional MLWA could be reduced half by placing a shorting wall. The back lobe elimina-tion work in the half-width MLWA has also been studied. In Ref. 8, the ‘‘half-width’’ MLWA was terminated with a resistive sheet to reduce the back reflection. However, all the methods mentioned earlier still require a long length (about 5k0) of the
half-width MLWA.
In this article, an alternative method with the length of 55 mm (about only 1 k0) is introduced to suppress the back
lobes. By changing the topology of the termination of the half-width MLWA, we can suppress the back lobes successfully. 2. ANTENNA DESIGN
Based on the half-width MLWA, the configuration of the pro-posed short length half-width MLWA is shown in Figure 1(a) which contained the top and side views. The design contains an oblique-shape termination and a linked square metal with a grounded via hole. The proposed MLWA has the length ofL¼ 55 mm (about 1k0) and the width of W¼ 7.5 mm. The whole
configuration is fabricated on a substrate of thickness h ¼ 1.6 mm and dielectric constanter ¼ 4.4. The shorting wall of
the half-width MLWA is realized by a row of grounded via holes. The details of the oblique shape termination and the linked square metal are shown in Figure 1(b), which is a magni-fied picture of the dash line area of Figure 1(a).
By using the oblique shape termination, the direction of the surface wave could be changed. Such that the reflected wave at the end would not travel straightly along the longitude edge of the proposed MLWA. The current distribution of the original half-width MLWA and the proposed MLWA with the oblique shape termination are shown in Figures 2(a) and 2(b), respec-tively. It’s obvious that the current distribution has been
changed at the oblique shape termination of the proposed MLWA.
A square metal with a grounded via hole is linked beside the proposed MLWA, it is used to guide the remainder power to the ground plane. When the remainder power reflected at the oblique shape termination, the reflected wave would be guided to the ground through the linked metal without leakage. One slot at the oblique shape termination is added to ensure that the remainder power is guided to the ground.
By these manners, the reflected wave at the end would not travel straightly and could be guided to the ground plane with-out leaking to air. The back lobe of the proposed short length half-width MLWA would be suppressed successfully.
3. SIMULATED AND MEASURED ANALYSIS
The simulated radiation patterns of the proposed MLWA com-pared with the original half-width MLWA at 4.6 and 4.7 GHz
are shown in Figures 3(a) and 3(b). The original half-width MLWA has the same shorting wall and length as the proposed MLWA. It’s obvious that the back lobes have been suppressed successfully in simulated results, and the measured results of radiation patterns at 4.6 and 4.7 GHz are shown in Figures 4(a) and 4(b), respectively. The gain of the main beam is 13.1 dB higher than the back lobe at 4.6 GHz and 7.2 dB at 4.7 GHz.
It is noticeable to speak of the scanning angle of the main beams about the proposed MLWA and original half-width MLWA. In simulated radiation patterns, the main beams of the proposed MLWA are slightly slanted to broadside direction compared with the original one. It is mainly due to the oblique shape termination. The oblique shape termination destroys the current distribution of the leaky mode of the proposed MLWA [Fig. 2(b)]. Therefore, the scanning region of the proposed MLWA is smaller than the original one but not by much. In the simulated results, the scanning angle of main beam of the origi-nal half-width MLWA is 34, whereas the proposed MLWA is
Figure 1 Structure of the proposed short length half-width MLWA
Figure 2 Current distributions, (a) the original half-width MLWA and (b) the proposed MLWA without the linked square metal
Figure 3 Simulated radiation patterns of the proposed MLWA compared with the original half-width MLWA at (a) 4.6 GHz and (b) 4.7 GHz
30 at 4.7 GHz. There is about 4 difference between the pro-posed MLWA and the original half-width MLWA.
Although in Figure 3 the main beams of the experimental results are slanted to end-fire direction unexpectedly. An error degree in the spinning mechanism of the measurement may take the blame for this issue. However, the scanning region of the main beams could sweep from 13 to 35 between 4.2 and 4.7 GHz in experimental results.
4. CONCLUSIONS
In this article, a novel short half-width MLWA with an oblique-shape termination and a linked square metal with a grounded via hole is introduced. The oblique-shape termination changes the direction of the reflected wave, and the reflected wave would not propagate straightly along the longitude edge of the pro-posed MLWA. The linked square metal with a grounded guides the remainder power to the ground. Compared with the original half-width MLWA, the proposed MLWA with a shorter length (only 1k0) has suppressed back lobes. The proposed novel short
half-width MLWA can be used in scanning systems.
REFERENCES
1. W. Menzel, A new travelling-wave antenna in microstrip, AEU 4 (1979), 137–140.
2. A.A. Oliner and K.S. Lee, The nature of the leakage from higher modes on microstrip line, IEEE MTT-S Int Microwave Symp Dig, Baltimore, MD (1986), 57–60.
3. A.A. Oliner and K.S. Lee, Microstrip leaky wave strip antennas, In: IEEE AP-S International Symposium Digest, Philadelphia, PA, 1986, pp. 443–446.
4. C.J. Wang, C.F. Jou, J.J. Wu, and S.T. Peng, Radiation characteris-tic of active frequency-scanning leaky-mode antenna arrays, IEIEC Trans Electron (1999), 1223–1228.
5. Y.C. Shih, S.K. Chen, C.C. Wu, and C.F. Jou, Active feedback microstrip leaky wave antenna-synthesizer design with suppressed back lobe radiation, IEE Electron Lett 35 (1999), 513–514. 6. I.Y. Chen, C.J. Wang, H.L. Guan, and C.F. Jou, Studies of
sup-pression of the reflected wave and beam-scanning features of the antenna arrays, IEEE Trans Antennas Propag 7 (2005), 2220–2225. 7. G.M. Zelinski, G.A. Thiele, M.L. Hastriter, M.J. Havrilla, and A.J. Terzuoli, Half width leaky wave antennas, IET Proc Microwave Antennas Propag 2 (2007), 341–348.
8. L. Kempel, S. Schneider, J. Radcliffe, D. Janning, and G. Thiele, FE-BI analysis of a leaky-wave antenna with resistive sheet termi-nation, In: IEEE/ACES International Conference on Wireless Com-munications and Applied Computational Electromagnetics, 2005, pp. 670–673.
VC2009 Wiley Periodicals, Inc.
MODIFIED SHORT-CIRCUIT
QUARTER-WAVELENGTH RESONATORS
FOR THE DESIGN OF MICROSTRIP
DUAL-PASSBAND BANDPASS FILTER
Ching-Wen Tang and Huan-Chang Hsu
Department of Communications Engineering, National Chung Cheng University, Chiayi 621, Taiwan, Republic of China; Corresponding author: [email protected]
Received 30 March 2009
ABSTRACT: In this article, a novel microstrip dual-passband bandpass filter has been proposed and developed. This filter is composed of two modified short-circuit quarter-wavelength resonators with a half-wavelength stepped-impedance resonator. Design procedures and theoretical analysis are provided; the prototypical bandpass filter with dual passbands is fabricated and measured as well. Well matched simulated results and experimental data validate the proposed filter.
VC2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 3026–
3029, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24811
Key words: dual-passband filter; bandpass filter
1. INTRODUCTION
Microstrip parallel-coupled filters have been one of the most commonly used filters. Particularly, stepped-impedance resona-tors (SIRs) have been widely used for the parallel-coupled reso-nators. It is indicated in [1] that SIRs have been widely used for analyzing discontinuity with an impedance step in a transmis-sion line.
Moreover, the design formulas of quarter-wavelength coaxial SIRs were analytically derived and applied to bandpass filters or balun for mobile communication in [2–4]. In addition, among various SIRs, the quarter-wavelength SIRs are more attractive in Figure 4 Measured and simulated radiation patterns of the proposed
MLWA at (a) 4.6 GHz and (b) 4.7 GHz
