Presentation for the final discussion of my MSc thesis focused on the "Design of a concept Planar Array for the Biomass Space Mission".

1. Design of a concept Planar Array for
the Biomass Space Mission
Relatore:
Prof. Gaetano Marrocco
Guido Casati
Correlatore:
Ing. Marco Sabbadini

2. BIOMASS Mission

Earth Explorer 7 Mission

Biomass Mapping

Enhancement of carbon cycle model

P-band (435 MHz)

SAR quad-POL (HH, VV, VH, HV)

External calibration through active ground Transponder

3. 
Operating Frequency: 435 MHz (λ=69 cm) Dual-Pol

Bandwidth: 10 MHz (2.3 %)

About 4 m diameter to get required RCS

High Directivity: ~25 dBi Broadside

Very low Back-Radiation and Side Lobe levels: SL< -45 dB

Negligible Cross-Talk: XPD > 40 dB
Calibration Transponder
Requirements of a concept Planar Array
Solution: Planar Array
Geometry: Hexagonal
Spacing: 0.48 m
Illumination law: Tukey

4. Process Flow
Prototyping:
Measurements
Advanced array:
Enhancement of the radiating element
Enhancement of the array design
Preliminary Design
Design and assessment of the radiating element
Performance of different array layouts

5. 
61 dual polarised Sub-Array

4 linearly polarised elements per Sub-Array

244 linearly polarised radiating elements

7 excitation levels, 26 dB dynamic range
Preliminary Design
Central area:
Uniform
Illumination
Tukey Illumination Law
5% tapering

6. 
fo = 435 MHz

L = λo4

Do = 3 dBi

B(Γ=-10dB) = 4.5 %
Preliminary design: PIFA
Planar Inverted-F Antenna
ADF-EMS/3DAM
h
L
z
yx
PEC
w

7. Preliminary design: PIFA
sub-array
ADF-EMS/3DAM
L=166 mm,
W=172 mm
h = 20 mm

8. Preliminary design: Array

Spacing: 535 mm (~480mm)

Diameter: >5m (~4 m)

SL < -40 dB at the horizon (<-45dB)

XPD > 25 dB (>40dB)
SL SL

9. Improvement of performance
Critical points:

Radiation Pattern

Coupling among active and passive elements

Spacing

Array size
Solution:

Reduce the volume of the Radiating Element

10. Advanced Design: Folded PIFA
λ/8λ/4
from “Development and Analysis of a Folded
Shorted-Patch Antenna With Reduced Size”
di M. M. Tentzeris

11. Do = 4 dBi
Advanced Design: Folded PIFA

L = W = 86 mm, h = 22 mm

Lg = Wg = 220 mm

Inductive Zin (Xin>0)

Γ = -17 dB

B(Γ=-10dB) = 6.5 MHz (1.5 %)

12. 
Tukey Illumination Law with 5% tapering

Spacing: 480 mm

Diameter of Sub-array: 330 mm

Overall Diameter: 4.16 m (~4 m)
Advanced Design: Array
x
y

13. 
SL < - 45 dB ( < 45 dB )

XPD > 45 dB ( > 40 dB )

Do = 23 dBi

BW3db = 13°

B(Γ = -20 dB)= 3 MHz
Advanced Design: Array
V-POL
H-POL

14. 
91 sub-array (364 radiating elements)

Diameter: 5 m (~4 m)

Tukey Illumination Law with
2.5 % tapering (9 levels, DR=32 dB)

Do = 25 dBi

SL < -55 dB (<-45 dB)

XPD > 50 dB (>40 dB)
Optimisations: 5 Rings Array

15. Optimisations: spacing
d=440 mm d=480 mm
θ=90°
Optimum for d=440 mm
Analytically:

16. 
Copper patch (height 0.25 mm)

Copper ground plane filled with duroid (height 2 mm)

Copper pin (diameter 2 mm) welded to SMA connector
Prototyping

17. 
ESTEC's CATR: 4 – 110 GHz

300 – 500 MHz, 250 KHz step

Γ = -13 dB a f = 411 MHz

StarLab: Γ = -19 dB a f = 417.5 MHz

B(Γ = -10 dB) = 7 MHz
Measurements: Return Loss
IFFT Filtering FFT

18. Sensitivity analysis
Tilt angle

High sensitivity to small changes of
the tilt angle of the patches
+
-
+
-
Lower patch
Upper patch

19. 
MVI's StarLab: 800 MHz - 18 GHz

NF / FF method

Do = 4.3 dBi, Go = 3.9 dB (e=98.7%)

BW = 120° (H-cut) / 110° (E-cut)
Measurements: radiation pattern
Directivity
H-Cut E-Cut

20. Outcome:

Design of a Planar Array that meet the requirements.

Data about several assessed layouts

Design and prototype of a miniaturised radiating element
Critical points:

Sensitivity of the radiating element

Bandwidth

Complexity of the feeding network
Evolution:

Array-Metasurface solution
Conclusions

21. THANK YOU FOR YOUR ATTENTION.
Info: Guido.casati89 [at] gmail.com
Q&A