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Microstrip antennas - Feeding techniques. Presented By: Alejandro Fuentes 260725 Ricardo Pérez 260769. Undergrad thesis. National university of Colombia GMUN - CMUN group 2008. Conrad project and our project logos. http://gmun.unal.edu.co/cmun. Feeding techniques. Coaxial feed
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Microstrip antennas - Feeding techniques Presented By: Alejandro Fuentes 260725 Ricardo Pérez 260769 Undergrad thesis National university of Colombia GMUN - CMUN group 2008 Conrad project and our project logos. http://gmun.unal.edu.co/cmun
Feeding techniques Coaxial feed Coplanar feed Proximity coupled feed Aperture coupled feed Coplanar waveguide feed UNAL 2008 Page 2
COAXIAL FEED UNAL 2008 Page 3
Coaxial feed The inner conductor is soldered to the patch. Source: [1]. R. Garg, P. Barthia, I. Bahl and A. Ittipiboon “Microstrip antenna design handbook,” Artech House, 2001, pp. 17 UNAL 2008 Page 4
Coupling UNAL 2008 Page 5 Excitation of the patch occurs through the coupling of the feed current density Jz to the Ez field. Coupling constant is:
Modeling Source: [1]. R. Garg, P. Barthia, I. Bahl and A. Ittipiboon “Microstrip antenna design handbook,” Artech House, 2001, pp. 719–727 The coaxial feed can be modeled by uniform line current. Input impedance model is: UNAL 2008 Page 6
Inductance compensation • Add a series capacitor • Electromagnetic coupling between the patch and the feed • The feed is terminated in a disk for increased coupling. Etch a concentric slot in the patch UNAL 2008 Page 7
COPLANAR FEED UNAL 2008 Page 8
Edge-coupled feed Source: [1]. R. Garg, P. Barthia, I. Bahl and A. Ittipiboon “Microstrip antenna design handbook,” Artech House, 2001, pp. 21 • It’s the basic technique for matching source and patch. • It’s necessary to set additional circuitry. UNAL 2008 Page 9
Gap-coupled Source: [1]. R. Garg, P. Barthia, I. Bahl and A. Ittipiboon “Microstrip antenna design handbook,” Artech House, 2001, pp. 719–727 • The gap effect can be represented by shunt capacitor. • Requires a narrow gap width for efficient coupling. UNAL 2008 Page 10
Inset feed Source: [1]. R. Garg, P. Barthia, I. Bahl and A. Ittipiboon “Microstrip antenna design handbook,” Artech House, 2001, pp. 719–727 Input resistance at resonance Feed position is selected for achieve a input impedance of 50 Ω. UNAL 2008 Page 11
PROXIMITY COUPLED FEED UNAL 2008 Page 12
Proximity coupled feed Electromagnetic coupling. Patch is on thick substrate (improve bandwidth). Feed line is on thinner substrate (reduce spurious radiations). Source: Balanis, C. “Antenna theory: analysis and design,” John Wiley & sons. 2th ed., chap. 14, section 14.1.2. UNAL 2008 Page 13
APERTURE COUPLED FEED UNAL 2008 Page 14
Aperture coupled feed Ground plane is between two substrates. Radiation from feed line doesn‘t interfere with radiation pattern of patch. Wider bandwidth. Source: Balanis, C. “Antenna theory: analysis and design,” John Wiley & sons. 2th ed., chap. 14, section 14.1.2. Source:Garg, Ramesh “Microstrip Antenna Design Handbook”, Artech House, 2001., Chap 1, section 1.3.4 UNAL 2008 Page 15
COPLANAR WAVEGUIDE FEED UNAL 2008 Page 16
Coplanar waveguide feed Coplanar waveguide is etched in the ground plane. a) Inductive coupling, b) capacitive coupling Mutual coupling between transmission lines are minimized. Source:Garg, Ramesh “Microstrip Antenna Design Handbook”, Artech House, 2001., Chap 1, section 1.3.5 UNAL 2008 Page 17