1. Microstrip Antennas
Microwave & Antenna Lab., CAU

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

3. 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

4. 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

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

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

7. Radiation Pattern
Microwave & Antenna Lab., CAU

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

9. 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 , Nov )
Microwave & Antenna Lab., CAU

10. 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

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

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

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

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

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

16. 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

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

18. Microwave & Antenna Lab., CAU

19. Microwave & Antenna Lab., CAU

20. Microwave & Antenna Lab., CAU

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

22. 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

23. 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 , June 2001.
Microwave & Antenna Lab., CAU

24. - 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

25. 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

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

27. 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

28. 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

29. 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

30. 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

31. 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

32. Practical Fabrication Rule
Microwave & Antenna Lab., CAU

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