efficient design of a c-band aperture-coupled stacked microstrip array using nexxim and designer...

Efficient design of a C-band aperture-coupled stacked microstrip array using Nexxim and

Designer

Alberto Di Maria

German Aerospace Centre (DLR) – Microwaves and Radar Institute – Oberpfaffenhofen

(DE)

ANSYS Conference & 27. CADFEM Users’ Meeting 2009 – Nov. 19 th - 2

Synthetic Aperture Radar (SAR)range resolution

synthetic aperture and azimuth resolution

image retrieval

Antenna specifications

Patch design

Array setup

Feeding networks

Antenna assemblyfeeding networks optimization

Solver-On-Demandconfiguration

refining the model

HFSS complete antenna model

Conclusions

Outline


azimuth (x)

height (z)

v

ground-range (y)

frequency

W t

t

phase

range

range resolution cell

range

swath

Synthetic Aperture Radar (SAR)range resolution

Cou

rtesy

of

Matt

eo N

an

nin

i


ground-range (y)

azimuth (x)

height (z)

x0

r(x)

SAR: synthetic aperture azimuth resolution

Cou

rtesy

of

Matt

eo N

an

nin

i

r(x)

xx0

chirpSynthetic Aperture


azimuth (x)

height (z)

range (y)

Synthetic Aperture Radar (SAR)

A Synthetic Aperture Radar (SAR) system allows the retrieval of reflectivity images of the observed scene with high spatial resolution.

A Synthetic Aperture Radar (SAR) system allows the retrieval of reflectivity images of the observed scene with high spatial resolution.

image retrieval

SLC Nominal Resolution: 1x1.5 m E-SAR (L-band) 1998


Antenna specifications

Carrier frequency 5.3 GHz (C-band)

Frequency range 5.05 GHz – 5.55GHz

Bandwidth 500 MHz (up to 800 MHz desirable)

Polarization Dual linear polarization (h, v)

Geometry Planar

Power 1.5 kW (peak)

Gain 17 dBi min

Input adaptation (S11)> 10 dB for 5.05 GHz – 5.55GHz

> 12 dB for 5.1 GHz – 5.5GHz

Azimuth beam width (θ3dB) 12 deg ± 1 deg

Azimuth Side Lobe Level (SLL) > 15 dB

Elevation (range) beam width (θ3dB) 34 deg ± 2 deg

Elevation Side Lobe Level (SLL) > 15 dB

Crosspolarization insulation ≥ 25 dBCritical requirements for SAR are: Bandwidth Azimuth beam width

Critical requirements for SAR are: Bandwidth Azimuth beam width


Patch design

Port1

Port2

W2

x

W1

x

Ls

Aw

A0

x

A0y

Aw


Patch design

4.00 4.50 5.00 5.50 6.00 6.50F [GHz]

-30.00

-25.00

-20.00

-15.00

-10.00

-5.00

0.00

Y1

DLR - Ansoft S parameters (dB) ANSOFT

m1 m2

m3 m4

Curve Info

dB(S(Port1,Port1))Setup 1 : Sw eep 1



Name Delta(X) Delta(Y) Slope(Y) InvSlope(Y)

d(m1,m2) 0.50 0.00 0.01 100.18

d(m3,m4) 0.80 0.26 0.32 3.13

Name X Y

m1 5.05 -21.90

m2 5.55 -21.89

m3 4.90 -16.91

m4 5.70 -16.66

5.002.001.000.500.200.00

5.00

-5.00

2.00

-2.00

1.00

-1.00

0.50

-0.50

0.20

-0.20

0.00 0

10

20

30

40

50

60

708090100

110

120

130

140

150

160

170

180

-170

-160

-150

-140

-130

-120

-110-100 -90 -80

-70

-60

-50

-40

-30

-20

-10

DLR - Ansoft Smith Chart 1 ANSOFT

m1

Curve Info

S(Port1,Port1)Setup 1 : Sw eep 1Name F Ang Mag RX

m1 5.3000 4.9688 0.0721 1.1546 + 0.0145i

The impedance matching has been optimized for bandwidth. S11 < -20dB over the bandwidth.

The impedance matching has been optimized for bandwidth. S11 < -20dB over the bandwidth.

impedance matching


-200.00 -150.00 -100.00 -50.00 0.00 50.00 100.00 150.00 200.00Theta [deg]

-60.00

-50.00

-40.00

-30.00

-20.00

-10.00

0.00

10.00

Y1

DLR - Ansoft Far Field - Gain (dB) ANSOFT

Curve Info

dB(GainAccepted)Setup 1 : Sw eep 2F='5.3GHz' Phi='0deg'

dB(GainAccepted)_1Setup 1 : Sw eep 2F='5.3GHz' Phi='90deg'

Patch design

Patch antenna gain = 8.5 dB Front to back ratio = 20

dB

Patch antenna gain = 8.5 dB Front to back ratio = 20

dB

radiation pattern


Array setup

Port1

Port2

Port3

Port4

Port5

Port6

Port7

Port8

Port9

Port10

Port11

Port12

patch_offset


Array setup

-100.00 -75.00 -50.00 -25.00 0.00 25.00 50.00 75.00 100.00Theta [deg]

-120.00

-100.00

-80.00

-60.00

-40.00

-20.00

0.00

20.00

Y1

DLR - Ansoft Radiated field - phi=0° ANSOFT

m3m1m2

Curve Info

dB(Ephi)Setup 1 : Sw eep 2F='5.3GHz' Phi='0deg'

dB(Etheta)Setup 1 : Sw eep 2F='5.3GHz' Phi='0deg'

Name Delta(X) Delta(Y) Slope(Y) InvSlope(Y)

d(m1,m2) -12.0000 0.0130 -0.0011 -922.2461

Name X Y

m1 6.0000 10.9124

m2 -6.0000 10.9255

m3 0.0000 13.7438

-100.00 -75.00 -50.00 -25.00 0.00 25.00 50.00 75.00 100.00Theta [deg]

-140.00

-120.00

-100.00

-80.00

-60.00

-40.00

-20.00

0.00

20.00

Y1

DLR - Ansoft Radiated field - phi=90° ANSOFT

Curve Info

dB(Ephi)Setup 1 : Sw eep 2F='5.3GHz' Phi='90deg'

dB(Etheta)Setup 1 : Sw eep 2F='5.3GHz' Phi='90deg'

Patches distance:optimized to obtain the

required beamwidth (12 deg).

Feed voltage tapering:using Dolph-Chebyshev to

obtain the required SLL (-20dB).

radiation pattern


Feeding network

Port1

Port2 Port3

Port4 Port5

Port6 Port7

P=init

W=W

f50

12

W1=W

f50W

2=W50to50

1

23T

U17Tee_Comp_ExtArms6

P=LT1 - W

50to50/2W

=W50to50

P=L1W=Wf50

P=L1W=Wf50

1 2

W1=Wf50W2=WT2

12

W1=Wf50W2=WT2

P=LT2 - WT2/2W=WT2

P=LT2 - WT2/2W=WT2

1

23

T

U1

Tee_

Com

p_E

xtA

rms6

1

23

TU2

Tee_

Com

p_E

xtA

rms6

P=L9

W=W

f55

P=L9

W=W

f55P

=L7

W=W

f50

P=L

7W

=Wf5

0

P=L6W=Wf50

P=L

8W

=Wf5

0

P=L6W=Wf50

P=L

8W

=Wf5

0

1

2T

U3Bend_OptimumMitered6

1

2T

U4

Ben

d_O

ptim

umM

itere

d6

1

2T

U5

Ben

d_O

ptim

umM

itere

d6

1

2T

U6

Bend_OptimumMitered6

1

2T


1

2T

U8Bend_OptimumMitered6 P=L2_1

W=Wf55

P=L2_1W=Wf55

1

2T U9

Bend_O

ptimum

Mitered6

1

2T

U10

Bend_O

ptimum

Mitered6

P=L

10W

=Wf5

5P

=LT3

- W

T3/2

W=W

T3

P=L

10W

=Wf5

5P

=LT3

- W

T3/2

W=W

T3

12

W1=

Wf5

5W

2=W

T3

12

W1=

Wf5

5W

2=W

T3

1

2 3T

U11Tee_Comp_ExtArms6

1

23T

U12Tee_Comp_ExtArms6 P=L5

W=Wf50

P=L

12W

=Wf5

0

1

2T

U13

Ben

d_O

ptim

umM

itere

d6

P=L5W=Wf50

1

2T

U14


P=L

12W

=Wf5

0

P=L3W=Wf100

12

W1=Wf100W2=WT4

P=LT4W=WT4

12

W1=WT4W2=Wf50

P=L4W=Wf50

1

2T

U15

Bend_O

ptimum

Mitered6

P=L

11W

=Wf5

0

P=L3W=Wf100

1 2

W1=Wf100W2=WT4

P=LT4W=WT4

1 2

W1=WT4W2=Wf50

P=L4W=Wf50

1

2T

U16

Bend_O

ptimum

Mitered6

P=L

11W

=Wf5

0

P=L2_2W=Wf55

P=L2_2W=Wf55

Port1

Port2 Port3

Port4 Port5

Port6 Port7

P=i

nit

W=W

f50

12 W1=Wf50

W2=W50to50

1

2 3T

U1Tee_Comp_ExtArms5

P=LT1 - W50to50/2W=W50to50

P=L1LW=Wf50

P=L1RW=Wf50

12

W1=Wf50W2=WT2

1 2

W1=Wf50W2=WT2

P=LT2L - WT2/2W=WT2

P=LT2R - WT2/2W=WT2

P=L3

W=W

f50

P=L3

W=W

f50

P=L4RW=Wf50

P=L5

W=W

f50

P=L4LW=Wf50

P=L5

W=W

f50

1

2T


1

2T

U3

Bend_O

ptimum

Mitered5

1

2T

U4

Bend_O

ptimum

Mitered5

1

2T

U5


P=L7LW=Wf55

P=L7RW=Wf55

1

2TU

6B

end_

Opt

imum

Mite

red5

1

2T

U7

Ben

d_O

ptim

umM

itere

d5

P=LT3L - W

T3/2W

=WT3

P=L8_1R

W=W

f55

12

W1=W

f55W

2=WT3

P=L10RW=Wf50

P=L11RW=Wf100

1 2

W1=Wf100W2=WT4 P=LT4R

W=WT4

1 2

W1=WT4W2=Wf50 P=L12R

W=Wf50

P=L8R+L8_2RW=Wf55

P=L8LW=Wf55

1

2

3T

U8Tee_90_ext3

1

2

3T

U9Tee_90_ext3

1

2T


P=L6W=Wf50 1

2T

U11

Ben

d_O

ptim

umM

itere

d5

P=L6W=Wf50

1

2T


1

2T


P=L8_2RW=Wf55

P=L9R

W=W

f55

12

W1=W

f55W

2=WT3

P=LT3R

- WT3/2

W=W

T3

1

23 T

U14Tee_Comp_aligned3

1

2 3T

U15Tee_Comp_aligned3

P=L12LW=Wf50

12

W1=WT4W2=Wf50

P=LT4LW=WT4

12

W1=Wf100W2=WT4

P=L11LW=Wf100

P=L10LW=Wf50

P=L9L

W=W

f55HH

VV

Special components are created in Designer and inserted in Nexxim.


schematic


Feeding network



layout


Feeding network A full parameterization and the use of Position Relative function assure the layout consistency over the variables variations.


Antenna assembly

PortV

PortH

H

V

Port1 Port2 Port3 Port4 Port5 Port6


U1ArrayOfSixPatches1

H

Port1


U2FeedingNetworkH1

V

Port1


U24FeedingNetworkV1



H

V

H

V

H

V

H

V

H

V

H

V

H

V



H

Port1


V

Port1


H

V



H

Port1


V

Port1


H

V



H

Port1


V

Port1


Port2 Port3

Port8 Port9

H

V

H

V

H

V

The array of six patches and the two feeding networks are combined together in a top level circuit in order to create the entire antenna.

schematic


Antenna assemblylayout


4.30 4.55 4.80 5.05 5.30 5.55 5.80 6.05 6.30F [GHz]

-50.00

-40.00

-30.00

-20.00

-10.00

0.00

Y1

DLR - Ansoft S parameter - Circuit simulation ANSOFT

Curve Info

dB(S(PortV,PortV))LinearFrequency

dB(S(PortV,PortH))LinearFrequency

dB(S(PortH,PortH))LinearFrequency

As the parameterization is retained through the hierarchy, it is possible to set-up optimization of the feeding networks directly in the top level circuit.

Feeding network optimization Antenna assembly


Solver-On-Demand

The Solver-On-Demand lets you choose the simulation engine. Then each antenna part can be simulated either as circuit or with full wave analysis.

configuration


Solver-On-Demand

4.30 4.55 4.80 5.05 5.30 5.55 5.80 6.05 6.30F [GHz]

-60.00

-50.00

-40.00

-30.00

-20.00

-10.00

0.00

Y1

DLR - Ansoft S parameter total - PlanarEM Simulation ANSOFT

Curve Info

dB(S(PortV,PortV))_PlanarEM

dB(S(PortV,PortH))_PlanarEM

dB(S(PortH,PortH))_PlanarEM

dB(S(PortV,PortV))_Circuit

dB(S(PortV,PortH))_Circuit

dB(S(PortH,PortH))_Circuit

Here a full wave analysis has been done. But the three components (feeding networks H and V and the array) are still independent i.e. no mutual coupling between them is considered.

Here a full wave analysis has been done. But the three components (feeding networks H and V and the array) are still independent i.e. no mutual coupling between them is considered.

refining the model – step 1


4.30 4.55 4.80 5.05 5.30 5.55 5.80 6.05 6.30F [GHz]

-60.00

-50.00

-40.00

-30.00

-20.00

-10.00

0.00

Y1

DLR - Ansoft S parameter total - FULL PlanarEM ANSOFT

Curve Info

dB(S(PortH,PortH))

dB(S(PortH,PortV))

dB(S(PortV,PortV))

dB(S(PortV,PortH))1

dB(S(PortH,PortH))1

dB(S(PortV,PortV))1

4.30 4.55 4.80 5.05 5.30 5.55 5.80 6.05 6.30F [GHz]

-60.00

-50.00

-40.00

-30.00

-20.00

-10.00

0.00

Y1

DLR - Ansoft S parameter total - FULL PlanarEM ANSOFT

Curve Info

dB(S(PortH,PortV))_FULL

dB(S(PortV,PortV))_FULL

dB(S(PortH,PortH))_FULL

dB(S(PortV,PortV))_Circuit

dB(S(PortV,PortH))_Circuit

dB(S(PortH,PortH))_Circuit

dB(S(PortV,PortV))1

dB(S(PortV,PortH))1

dB(S(PortH,PortH))1

Solver-On-Demand

Simulation shows that, when the entire antenna is simulated at once, the matching is up to 8dB worse than what we obtained with optimization at the circuit level.

What can be done?

Simulation shows that, when the entire antenna is simulated at once, the matching is up to 8dB worse than what we obtained with optimization at the circuit level.

What can be done?

8dB8dB

refining the model – step 2


Solver-On-Demand

Simulation shows that, when the entire antenna is simulated at once, the performance is up to 8dB worse than what we obtained with optimization at the circuit level.

What can be done?

Simulation shows that, when the entire antenna is simulated at once, the performance is up to 8dB worse than what we obtained with optimization at the circuit level.

What can be done?

Through Solver-On-Demand (as the parameterization is retained) it is possible to optimize again the antenna matching, running the simulation with PlanarEM engine.

Through Solver-On-Demand (as the parameterization is retained) it is possible to optimize again the antenna matching, running the simulation with PlanarEM engine.

The entire antenna can be exported in one click to HFSS, retaining all the variables and parameters. The final optimization can be run in HFSS. Other elements can be taken in account (connectors, screws, vertical elements)

The entire antenna can be exported in one click to HFSS, retaining all the variables and parameters. The final optimization can be run in HFSS. Other elements can be taken in account (connectors, screws, vertical elements)



The model is electrically large and complex


Distributes mesh sub-domains to networked processors and memory



HFSS complete antenna modelDomain Decomposition Solver Profile

8 Domains


HFSS complete antenna modelField Animation: Antenna, feed and enclosureVertical Polarization


HFSS complete antenna modelField Animation: Antenna, feed and enclosureHorizontal Polarization


Conclusions

The design of an array antenna suitable for an airborne SAR system, operating at C-Band has been presented.

Every antenna component has been designed separately with a fully parameterized model and has been easily tuned and optimized with Designer, to meet the dimensional and frequency requirements.

The individual components are then assembled and interconnected in the Nexxim circuit simulator to form the entire array. The assembly is tuned and optimized using the speed capability of Nexxim.

The Solver-On-Demand feature lets us choose which part of the antenna will be solved with a full wave analysis and which part will be solved with a fast circuit simulation.

The entire antenna has been then exported in HFSS. The final tuning is hence done in a very detailed model.

The design of an array antenna suitable for an airborne SAR system, operating at C-Band has been presented.

Every antenna component has been designed separately with a fully parameterized model and has been easily tuned and optimized with Designer, to meet the dimensional and frequency requirements.

The individual components are then assembled and interconnected in the Nexxim circuit simulator to form the entire array. The assembly is tuned and optimized using the speed capability of Nexxim.

The Solver-On-Demand feature lets us choose which part of the antenna will be solved with a full wave analysis and which part will be solved with a fast circuit simulation.

The entire antenna has been then exported in HFSS. The final tuning is hence done in a very detailed model.


Thank you

efficient design of a c-band aperture-coupled stacked microstrip array using nexxim and designer...

Documents

cadfem users

schematicansys conference

dbansys conference

layoutansys conference

patch designansys conference

array setup ansys conference

cband aperture

antenna assemblythe