Forum for Electromagnetic Research Methods and Application Technologies (FERMAT) Planar Leaky-Wave Antennas Based on Microstrip Line and Substrate Integrated Waveguide (SIW) Dr. Juhua Liu liujh33@mail.sysu.edu.cn
Copyright The use of this work is restricted solely for academic purposes. The author of this work owns the copyright and no reproduction in any form is permitted without written permission by the authors. 2
Abstract Abstract: Recent advances of our researches on planar leaky-wave antennas are summarized. The planar leaky-wave antennas are fabricated on microstrip line and substrate integrated waveguide (SIW), which are low profile, low cost and easy to manufacture. They can inherently generate a narrow beam that scans with frequency. Researches were performed with special emphasis on the theoretical calculation and the excitation of the first higher mode in the microstrip leaky-wave antennas, and the endfire radiation and the circular polarization with the SIW leaky-wave antennas. Key words: Leaky-wave antennas, microstrip antennas, SIW antennas, wavenumber. 3
Biography Juhua Liu was born in Heyuan, Guangdong, China, in September, 1981. He received the B.S. and Ph.D. degrees from the Sun Yat-sen University, China, in 2004 and 2011, respectively. From 2008 to 2009, he was a Visiting Scholar in the Department of Electrical and Computer Engineering, University of Houston, Houston, TX, USA. From September 2011 to September 2012, he was a Senior Research Associate with the State Key Laboratory of Millimeter Waves, City University of Hong Kong, Hong Kong, China. From 2012-2015, he was a Lecture in the Department of Electronics and Communication Engineering, Sun Yat-sen University, Guangzhou, China. Since 2015 he has been an Associate Professor in the same department. His present research interests include leaky-wave antennas, microstrip antennas, substrate integrated waveguide antennas, antenna theory, and computational electromagnetics. 4
Outline 1. Introduction 2. Microstrip leaky-wave antennas 3. SIW leaky-wave antennas 4. Conclusion 5
1. Introduction History In 1940, (Hansen) waveguide leaky-wave antenna z y x 1981, (Menzel) microstrip leaky-wave antenna z y x This century, SIW leaky-wave antenna h w ε s d y x via z 6
1. Introduction Advantages Narrow beamwidth, high gain Beam scanning 120 o 90 o 60 o 0 db Simple structure 150 o -10 db 30 o -20 db Easy feeding 180 o -30 db 0 o 7
1. Introduction Applications Collision-avoidance radar (e.g., vehicle), radar sensor Wireless location Military(target tracking in high-speed flight) Wireless communications 8
k z = β jα θ 0 9 1. Introduction Key parameter: propagation wavenumber k z = β jα Phase constant β θ 0 Attenuation constant α θ cosθ θ = = β k 0 0 α k0 2 sin θ 0 Region k z k 0
2. Microstrip leaky-wave antenna Microstrip leaky-wave antenna Simple structure Usually working in the first higher mode Difficulty: k z = β jα 10
2.1. Propagation wavenumber Target: k z = β jα Method: Transverse resonant method Difficulties: Y t = Y t11 + Y t12 Self-admittance Y t11 Mutual admittance Y t12 Methods Substrate ε, µ h y W r r Ground plane Top plane Y0, k x1 Y t x Wiener-Hopf method: Y t11 Spectral domain method: Y t12 W 2 11
2.1. Propagation wavenumber Numerical results (low permittivity) β /k 0 1.4 1.2 1 0.8 0.6 0.4 0.2 ε r, µ r Our accurate Our approximate Oliner MoM HFSS 0 5 6 7 8 9 10 11 12 Frequency (GHz) W W = 15 mm h = 0.794 mm ε r = 2.32, µ r = 1 Phase constant h α /k 0 1.1 1 0.9 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 ε r, µ r Our accurate Our approximate Oliner MoM HFSS 0 5 5.5 6 6.5 7 7.5 8 8.5 9 Frequency (GHz) W W = 15 mm h = 0.794 mm ε r = 2.32, µ r = 1 Attenuation constant h 12
2.1. Propagation wavenumber Numerical results (high permittivity) 1.2 1.1 1 0.9 0.8 ε r, µ r W W = 3 mm h = 0.635 mm ε r = 10.2, µ r = 1 h 1 0.9 0.8 0.7 0.6 ε r, µ r W W = 3 mm h = 0.635 mm ε r = 10.2, µ r = 1 h β /k 0 0.7 0.6 0.5 0.4 0.3 Our accurate Our approximate Oliner MoM HFSS α /k 0 0.5 0.4 0.3 0.2 0.1 Our accurate Our approximate Oliner MoM HFSS 0.2 12 12.5 13 13.5 14 Frequency (GHz) 0 12 12.5 13 13.5 14 Frequency (GHz) Phase constant Attenuation constant Juhua Liu*, D. R. Jackson, Yunliang Long, Propagation wavenumbers for half- and fullwidth microstrip lines in the EH1 mode, IEEE Trans. Microw. Theory Tech., vol. 59, no. 12, pp. 3005 3012, Dec. 2011. 13
2.2. Suppression of EH 0 mode Operating leaky mode: EH 1 mode Unwanted mode: EH 0 mode Decreases the excitation efficiency of EH 1 mode Needs to be suppressed z W x substrate ε r, µ r h y ground plane 14
2.2. Suppression of EH 0 mode Technique: periodic shorting vias Operation principles Stop band generated by periodic shorting vias EH 0 mode decays in the stop band, but not the EH 1 mode EH 0 is effectively suppressed in the stop band y W p d x z p 1 p d x z h ε r 15
2.2. Suppression of EH 0 mode β /k 0 EH 0 stop band vs. EH 1 leaky region 1.5 1.4 1.3 1.2 1.1 1 0.9 0.8 0.7 0.6 1 via 2 vias 3 vias 4 vias 5 vias 0.5 5 6 7 8 9 10 0 Frequency (GHz) 1 0.9 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 α /k 0 β /k 0 1.2 1.1 1 0.9 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 No via (TRM) No via (HFSS) 1 via (HFSS) 4 vias (HFSS) 0 5 6 7 8 9 10 0 Frequency (GHz) 1.2 1.1 1 0.9 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 α /k 0 EH 0 mode EH 1 mode 16
2.2. Suppression of EH 0 mode Wider bandwidth Lower reflection coefficient More stable and higher gain S 11 (db) 0-5 -10-15 -20-25 -30-35 No via, HFSS -40 1 via, HFSS -45 4 vias, HFSS 4 vias, measure -50 6 6.5 7 7.5 8 8.5 9 Frequency (GHz) Gain (dbi) 18 16 14 12 10 8 6 4 2 0-2 No via, HFSS 4 vias, HFSS 4 vias, measure -4 6 6.5 7 7.5 8 8.5 9 Frequency (GHz) 17
2.2. Suppression of EH 0 mode Beam scanning with frequency f = 6.3 GHz 120 o 90 o 0 db 150 o -10 db -20 db -30 db 180 o 60 o 30 o 0 o f = 6.9 GHz 120 o 90 o 0 db 150 o -10 db -20 db -30 db 180 o 60 o 30 o 0 o f = 7.5 GHz 120 o 90 o 0 db 150 o -10 db -20 db -30 db 180 o 60 o 30 o 0 o f = 8.1 GHz 120 o 90 o 0 db 150 o -10 db -20 db -30 db 180 o 60 o 30 o 0 o 210 o 330 o 210 o 330 o 210 o 330 o 210 o 330 o 240 o 270 o 300 o 240 o 270 o 300 o 240 o 270 o 300 o 240 o 270 o 300 o E φ, HFSS E φ, measure E θ, HFSS E θ, measure Juhua Liu*, Yuanxin Li, Yunliang Long, Design of periodic shorting-vias for suppressing the fundamental mode in microstrip leaky-wave antennas, IEEE Transactions on Antennas and Propagation, vol. 63, no. 10, pp. 4297-4304 October 2015. 18
2.3. Half-Mode SIW leakywave antenna Half-mode substrate integrated waveguide (HMSIW) leaky-wave antenna Similar to half-width microstrip leaky-wave antenna No need to suppress any other mode (e.g., EH 0 mode) Fundamental mode: leaky mode, similar to the EH 1 mode in the a microstrip line Gain: not as high as a full-width microstrip leaky-wave antenna y d w p x z h ε r, µ r 19
2.3. Half-Mode SIW leakywave antenna Accurate and efficient calculation of the propagation wavenumber Analysis method: Method of auxiliary sources (MAS) Equivalent transverse network Simple, accurate, efficient δ v r δ r u d Y 1n J s w+ x Y 1n Y tn 20
2.3. Half-Mode SIW leakywave antenna Propagation wavenumber k z = β jα Juhua Liu*, Yuanxin Li, Shaoyong Zheng, Yunliang Long, Method of auxiliary sources for analyzing half-mode substrate integrated waveguide, IEEE Antennas Wireless and Propagation Letters, vol. 13, pp. 1043 1046, 2014. 21
2.4. EH 0 leaky mode in vialoaded microstrip line EH 0 mode in non-loaded microstrip line Fundamental mode Slow wave, bound mode Even mode EH 0 mode in via-loaded microstrip line Fast wave Leaky mode Even mode 22
2.4. EH 0 leaky mode in vialoaded microstrip line Via-loaded microstrip line Propagation wavenumber Method of auxiliary sources (MAS) Transverse equivalent circuit W p d y x z h ε r AS CP r r d AS CP Y c x J s W 2 x Y 1n Y tn x 23
2.4. EH 0 leaky mode in vialoaded microstrip line Propagation wavenumber k z = β jα EH 0 mode: even mode EH 1 mode: odd mode 1.4 1.4 1.2 1.2 1 1 β /k 0 0.8 0.6 0.4 0.2 Even Odd p = 3 mm, MAS p = 6 mm, MAS p = 6 mm, HFSS p = 9 mm, MAS p = 12 mm, MAS p =, TRM 0.8 0.6 0.4 0.2 α /k 0 0 5 6 7 8 9 10 11 12 0 Frequency (GHz) 24
2.4. EH 0 leaky mode in vialoaded microstrip line Microstrip EH 0 -mode leaky-wave antenna y x z Juhua Liu*, Yuanxin Li, Yunliang Long, Fundamental even leaky mode in microstrip line loaded with shorting vias, IET Microwaves Antennas & Propagation, vol. 11, no. 1, pp. 129-135, Jan. 2017. 25
3. SIW leaky-wave antennas Substrate integrated waveguide (SIW) Advantages Low cost, light weight Easy fabrication Easy integration Can be approximated as rectangular waveguide s d y x via w z h ε 26
3.1. SIW leaky-wave antenna with transverse slots SIW with periodic transverse slots Leaky-wave antennas: usually can not scan to endfire This antenna: scan to endfire Why? Leaky wave + surface wave Leaky wave: scan from near broadside to near endfire Surface wave: endfire s d y x via w p L W slot z h ε r 27
3.1. SIW leaky-wave antenna with transverse slots Theoretical analysis y L W SIW rectangular waveguide p x Magnetic field integral equation Solve: k z = β jα b ε, µ r a r z mπ L cos π ( kymn1b) π µ a sinc k W 2 k + j In = 0 a ml k b Lb 1 2 a 2 2 2 2 2 m 2 cot r ( zn ) a 1 2 2 2 2 n= m= 1,3,5,... ymn1 16 Juhua Liu*, D. R. Jackson, Yunliang Long, Modal analysis of dielectric-filled rectangular waveguide with transverse slots, IEEE Transactions on Antennas and Propagation, vol. 59, no. 9, pp. 3194-3203, September 2011. 28
1.4 1.2 1 3.1. SIW leaky-wave antenna with transverse slots Numerical results: (a) Leaky mode, (b) surface-wave mode, (c) proper waveguide mode (b) (c) 10 0 10-1 Leaky, Theory Leaky, HFSS 0.8 β /k 0 0.6 0.4 0.2 0 (a) Leaky, Theory Leaky, HFSS Proper, Theory Proper (Surface), HFSS Proper (Waveguide), HFSS 8 9 10 11 12 Frequency (GHz) Phase constant α /k 0 10-2 10-3 10-4 8 8.2 8.4 8.6 8.8 9 9.2 9.4 9.6 9.8 10 Frequency (GHz) Attenuation constant 29
3.1. SIW leaky-wave antenna with transverse slots Microstrip line Vias Slots Microstrip line 0 12.9 22.5 10.5 4.55 40-5 -10 30 220 30 Units: mm S (db) -15-20 -25 S 11, HFSS -30 S 21, HFSS -35 S 11, measured S 21, measured -40 9.5 10 10.5 11 11.5 12 12.5 Frequency (GHz) Antenna configuration S11 & S21 30
3.1. SIW leaky-wave antenna with transverse slots Capable to scan to endfire Measured Theory HFSS (infinite) HFSS (finite) 0 db 150 120-10 db 90 60 f = 10.2 GHz 30 180 0 Measured Theory HFSS (infinite) HFSS (finite) 0 db 150 120-10 db 90 60 f = 11.7 GHz 30 180 0 Theory HFSS (infinite) HFSS (finite) 0 db 150 120-10 db 90 60 30 180 0 f = 12 GHz 210 330 210 330 210 330 240 270 300 240 270 300 240 270 300 Juhua Liu*, D. R. Jackson, Yunliang Long, Substrate integrated waveguide (SIW) leakywave antenna with transverse slots, IEEE Transactions on Antennas and Propagation, vol. 60, no. 1, pp. 20-29, January 2012. 31
3.2 Endfire radiation Consider: a traveling-wave antenna MM zz = AA zz ee jjββzz Usually, when ββ < kk 0, a line source with uniform AA zz distribution has a higher directivity than a tapered one. However, when when ββ > kk 0, we found that the rule is not correct. 32
3.2 Endfire radiation Comparison of different amplitude distributions When ββ > kk 0, a tapered distribution provides a higher peak directivity than the uniform one. Amplitude distribution Directivity 33
3.2 Endfire radiation SIW travelling-wave antenna with tapered slots Geometry Top view Bottom view 34
3.2 Endfire radiation The pattern for the tapered antenna with the highest directivity Juhua Liu*, David R. Jackson, Yuanxin Li, Chaoqun Zhang, and Yunliang Long, Investigations of SIW leaky-wave antenna for endfire-radiation with narrow beam and sidelobe suppression, IEEE Transactions on Antennas and Propagation, vol. 62, no. 9, pp. 4489-4497, September 2014. 35
3.3. SIW leaky-wave antenna with H-shaped slots SIW with H-shaped slots Circular polarization High and flat leakage constant y x s d via w L 1 L 2 p slot W r z h ε r 36
3.3. SIW leaky-wave antenna with H-shaped slots Analysis method: magnetic field integral equation h w L 1 ε r L 2 s d p y slot x W via r z b z ε r a p r y L 1 W L 2 x Juhua Liu*, Yunliang Long, A full-wave numerical approach for analyzing rectangular waveguides with periodic slots, IEEE Transactions on Antennas and Propagation, vol. 60, no. 8, pp. 3754-3762, August 2012. 37 37
3.3. SIW leaky-wave antenna with H-shaped slots Modes: (a) leaky-wave mode, (b) surface-wave mode, (c) proper waveguide mode Leaky constant: flat, high 1.2 (b) (c) 0.03 1 0.025 0.8 0.02 β /k 0 0.6 (a) α /k 0 0.015 0.4 0.2 Closed waveguide Leaky, MFIE Leaky, HFSS Proper, MFIE Proper (surface-wave), HFSS Proper (waveguide), HFSS 0.01 0.005 Leaky, MFIE Leaky, HFSS 0 10 10.5 11 11.5 12 12.5 Frequency (GHz) Phase constant 0 10 10.5 11 11.5 Frequency (GHz) Leakage constant 38 38
3.3. SIW leaky-wave antenna with H-shaped slots Microstrip line Vias H-shaped slots Microstrip line 12.9 10.5 50 22 30 220 30 Units: mm Antenna configuration S (db) 0-5 -10-15 -20-25 -30-35 S 11, HFSS S 21, HFSS S 11, Measured S 21, Measured -40 9.5 10 10.5 11 11.5 12 12.5 Frequency (GHz) S11 & S21 39
3.3. SIW leaky-wave antenna with H-shaped slots At 10.6 GHz, circular polarization. Pattern (db) 0-10 -20 0 10 20 30 40 50 60 70 80 90 9 f = 10.6 GHz θ (deg.) AR (db) 6 3 0 0 20 40 60 80 θ (deg.) Juhua Liu*, Xihui Tang, Yuanxin Li, Yunliang Long, Substrate integrated waveguide leaky-wave antenna with H-shaped slots, IEEE Transactions on Antennas and Propagation, vol. 60, no. 8, pp. 3962-3967, August 2012. 40
4. Conclusion Microstrip leaky-wave antenna Calculate k z for the EH 1 mode accurately Suppress the unwanted EH 0 mode with the stop band generated by shorting vias Analyze the half-mode SIW leaky-wave antenna using the method of auxiliary sources (MAS) Investigate the EH 0 leaky mode in via-loaded microstrip line SIW leaky-wave antenna SIW leaky-wave antenna with transverse slots for endfire scanning capability A tapered traveling wave antenna provides higher endfire directivity than a uniform one SIW leaky-wave antenna with H-shaped slots for circular polarization 41
References [1]. Juhua Liu*, D. R. Jackson, Yunliang Long, Propagation wavenumbers for half- and full-width microstrip lines in the EH1 mode, IEEE Transactions on Microwave Theory and Techniques, vol. 59, no. 12, pp. 3005-3012, December 2011. [2]. Juhua Liu*, Yuanxin Li, Yunliang Long, Design of periodic shorting-vias for suppressing the fundamental mode in microstrip leaky-wave antennas, IEEE Transactions on Antennas and Propagation, vol. 63, no. 10, pp. 4297-4304 October 2015. [3]. Juhua Liu*, Yuanxin Li, Shaoyong Zheng, Yunliang Long, Method of auxiliary sources for analyzing half-mode substrate integrated waveguide, IEEE Antennas Wireless and Propagation Letters, vol. 13, pp. 1043 1046, 2014. [4]. Juhua Liu*, Yuanxin Li, Yunliang Long, Fundamental even leaky mode in microstrip line loaded with shorting vias, IET Microwaves Antennas & Propagation, vol. 11, no. 1, pp. 129-135, Jan. 2017. [5]. Juhua Liu*, D. R. Jackson, Yunliang Long, Modal analysis of dielectric-filled rectangular waveguide with transverse slots, IEEE Transactions on Antennas and Propagation, vol. 59, no. 9, pp. 3194-3203, September 2011. [6]. Juhua Liu*, D. R. Jackson, Yunliang Long, Substrate integrated waveguide (SIW) leaky-wave antenna with transverse slots, IEEE Transactions on Antennas and Propagation, vol. 60, no. 1, pp. 20-29, January 2012. [7]. Juhua Liu*, David R. Jackson, Yuanxin Li, Chaoqun Zhang, and Yunliang Long, Investigations of SIW leaky-wave antenna for endfire-radiation with narrow beam and sidelobe suppression, IEEE Transactions on Antennas and Propagation, vol. 62, no. 9, pp. 4489-4497, September 2014. [8]. Juhua Liu*, Yunliang Long, A full-wave numerical approach for analyzing rectangular waveguides with periodic slots, IEEE Transactions on Antennas and Propagation, vol. 60, no. 8, pp. 3754-3762, August 2012. [9]. Juhua Liu*, Xihui Tang, Yuanxin Li, Yunliang Long, Substrate integrated waveguide leaky-wave antenna with H- shaped slots, IEEE Transactions on Antennas and Propagation, vol. 60, no. 8, pp. 3962-3967, August 2012. 42
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