Microstrip Antennas Microwave & Antenna Lab., CAU

Microstrip Patch Antenna (MPA) patch radiator dielectric substrate conductive ground plane 0.01 to 0.1 wavelength Microwave & Antenna Lab., CAU

Characteristics Advantages - thin conformal - light weight - compatible with MIC & MMIC - cost effective - easy fabrication Disadvantages - narrow bandwidth - low power handling Frequency : UHF to 100 GHz Microwave & Antenna Lab., CAU

Application Areas Commercial - PCS, IMT-2000, WLAN, GPS - DBS, mobile satellite communications - medical, etc. Military - radar / missile - communication system Spacecraft - earth remote sensing - aircraft SAR Microwave & Antenna Lab., CAU

Types of MPA probe feed microstrip line feed buried feed aperture-coupled feed Microwave & Antenna Lab., CAU

Radiation Mechanism Lp Lp : patch length Wp : patch width Dl : equivalent extended length of open stub reinforce broadside Wp cancel Microwave & Antenna Lab., CAU

Radiation Pattern Microwave & Antenna Lab., CAU

Directivity & Gain Generally low gain : 6~7 dB High gain can be obtained in array forms. Microwave & Antenna Lab., CAU

Bandwidth General criterion : VSWR=2 (S11= -10 dB) Generally narrow BW ( < 5% ) BW broadening methods - BW is generally proportional to a volume formed by patch. er h Thick, low permittivity substrate Parasitic patch Stacked patch U-slot patch  BW > 30 % for single element BW broadening method by external impedance matching circuit (Van De Capelle, IEEE AP, pp. 1345-1354, Nov. 1989.) Microwave & Antenna Lab., CAU

Dual Polarization Problem of space diversity - Distance between two antennas should be long. Polarimetry systems – polarimetric SAR H-pol V-pol Microwave & Antenna Lab., CAU

Circular Polarization LHCP RHCP RHCP LHCP RHCP LHCP Single feed Dual feed (90o difference) Microwave & Antenna Lab., CAU

Miniaturization Current path < l/4 Inverted F Antenna Slotted Patch Microwave & Antenna Lab., CAU

Practical MPA Design Parameters Patch width y Wp x Patch length Lp er h Microwave & Antenna Lab., CAU

Transmission Line Model Microstrip line feed R : radiation resistance quarter-wave transformer Microwave & Antenna Lab., CAU

Continued probe feed feed point Microwave & Antenna Lab., CAU

Microstrip Patch Antenna Design Example Design Goal Structure Parameters of Printed Circuit Board er = 2.2 h = 1.6 mm er h Microwave & Antenna Lab., CAU

Design Steps y Wp x Lp er h Microwave & Antenna Lab., CAU

Microwave & Antenna Lab., CAU

Microwave & Antenna Lab., CAU

Microwave & Antenna Lab., CAU

Design of ACMPA patch coupling slot feed SSFIP Microwave & Antenna Lab., CAU

Why ACMPA ? Patch and feed circuit can be optimized independently and simultaneously. Spurious slot radiation can be reduced using thin substrate of high er in feed side. Radiation efficiency and bandwidth can be increased using thick substrate of low er in patch side. Back side radiation from slot and feed line can be eliminated by an additional ground plane. Microwave & Antenna Lab., CAU

Improved Transmission Line Model Two back-to-back-microstrip lines coupled by an aperture on the ground plane Reciprocity formulation & Finite Fourier transform Leads to an equivalent circuit formulation Jeong Phill Kim and Wee Sang Park, “Analysis and Network Modeling of an Aperture-Coupled Microstrip Patch Antenna,” IEEE Trans. AP, vol. AP-49, no. 6, pp. 849-854, June 2001. Microwave & Antenna Lab., CAU

- Reciprocity formulation - Finite Fourier transform Turn ratios nf and np - Reciprocity formulation - Finite Fourier transform Slotline parameters - Well-known analysis method Overall input impedance - Network theory Microwave & Antenna Lab., CAU

Design Methodology Spec. of ACMPA Choice of appropriate PCBs Initial guess of dimensions Simulation Comparison no Corrections Patch length / Slot length / Feed line stub yes Fabrication & Measurement Microwave & Antenna Lab., CAU

Initial Guess of Dimensions patch coupling slot feed patch length ~ 0.45 lg width ~ 0.35 lg slot length ~ 0.2 lo width ~ 0.015lo Feed line stub length will be determined from the matching condition. Microwave & Antenna Lab., CAU

Simulation (in detail) Z2 is obtained from [S] by using the improved transmission line model or commercial EM field simulators. reference plane A A’ A A 50 W 50 W Z2 + - Zin A’ A’ Microwave & Antenna Lab., CAU

Commercial Softwares MOM (Method of Moments) - Momentum (Agilent) - IE3D (Zeland Software) - Ensemble (Ansoft) - FEKO (EMSS) FDTD (Finite-Difference Time-Domain) - Microwave Studio (CST) FEM (Finite Element Method) - HFSS (Ansoft) Circuit Simulator - ADS (Agilent) - Serenade (Ansoft) - Genesys (Eagleware) Microwave & Antenna Lab., CAU

Simulation (continued) Input impedance from [S] R2 should be larger than 50 W near required resonant frequency. After stub tuning, Xm = -X2 can be achieved by adjusting the stub length. Microwave & Antenna Lab., CAU

Simulation (continued) Two port simulation Calculate Z2=R2+ j X2 Plot R2 & X2 no R2 > 50 W Increase aperture length Increase path length yes yes no no Decrease path length f1=f0 f1>f0 yes Adjust stub length (Eliminating the reactance) Output design data Microwave & Antenna Lab., CAU

Simulation (Example) Resonant frequency by patch length control Coupling amount by slot length control 50 W R2 R2, X2 f0 f1 Eliminating reactance by stub length control X2 frequency Microwave & Antenna Lab., CAU

Practical Fabrication Rule Microwave & Antenna Lab., CAU

Fabrication Methods Chemical etching Mechanical milling Microwave & Antenna Lab., CAU