Ansoft Designer

Passive Microwave Component 

Design and Optimization 

Haiqiang Ding 

Senior Application Engineer 

Ansoft Beijing Office 

Jolly Zhou 

Senior Application Engineer 

Ansoft Shanghai Office

Abstract 

• Challenges of Modern Microwave Component and 

Antenna Design 

• Waveguide Slot Array Computer Aided Design and 

Simulation 

• Rapid Direction-Finding Antenna Array Design 

• Satellite Communication Antennas Simulation 

• Rotary Joint Optimization

Modern Microwave Component and 

Antenna Design 

• Higher Performance 

• More Complex 

• Complex Radiation Pattern 

• System Level Design 

• Design Cost and cycle

Benefits of using Electromagnetic Field 

Solvers 

• Make Good Thinking to Good Design 

• Decrease Instruments Time 

• Design Costs and Cycle 

• Human Resource

Requirements of Electromagnetic Field 

Simulators for Modern Design 

• Accuracy,Reliable and Fast 

• Simulation Capacity 

• Real Arbitrary 3D Structure 

• Easy to Use 

• Technical Support

Ansoft HFSS: Golden Tool for Antenna and 

Passive Microwave component Design 

• Powerful Features 

• Accuracy,Reliable and Fast 

• More than 10,000 customer all over the word 

• Adaptive Meshing 

• Technical support

Waveguide Slot Array Computer 

Aided Design and Simulation

Waveguide Slot Array Antenna 

Waveguide Slot Array Antennas are well used 

in Defense such as Radar on Fighter, Missile or 

ground. 

•Good Antenna Gain, low side lobe and VSWR 

•Good Mechanical performance 

Ground Radar 

Radar on Aircraft

Waveguide Slot Array 

Waveguide Slots 

• Slots in Waveguide Slot Array antennas 

• Every slot is different: depend on the array factor 

• Prototype for the slots is tiresome 

• Use HFSS design every slot and get design curve

Waveguide Slot 

• Broadwall Displaced Slot 

• Broadwall inclined Slot 

• Edge Wall Slot

Ansoft HFSS 

Broadwall Displaced Slot Design 

• Y martix in the test port will equal to the Ymartrix in the center of the 

slot when the distance is half of guide wave wavelength 

• To get the guided wavelength, just perform a “ports only” solve in 

HFSS 

• When the slot is resonant, Im(Y(11)) =0 

¼Lg 

½ Lg 

Lg: Guided wave 

wavelength 

Offset 

Test Port 

Short 

length


Broad wall Displaced Slot Design 

Build the simulation model in 

HFSS v9 

Direct parametric 

Very easy to use 

Set variable in /HFSS/design 

properties/local variables 

Design parameters 

• length:resonant length of 

slot, to be optimized 

• Offset: Slot center displace 

from the waveguide center



• When the slot is resonant, Im(Y)=0 

• Use ABS(Im(Y)) as cost function 

• Change offset from 1mm to 8mm, step 

1mm, optimize length (resonant length) 

at every point 

• Design curve is generated


Broadwall Displace Slot Design 

• Optimization variable setting in 

HFSS v9 

• Length will be optimized



• Optimization in HFSS v9 

• Cost function changes when optimization


Generate Slot Design Curve 

• Design curve is generated by HFSS v9 and optimization 

• Resonant length of wave guide slot vs. Offset distance


Broad wall Inclined Slot Design 

• Y martix in the test port will equal to the Ymartrix in the center 

of the slot when the distance is half of guide wave wavelength 

• Also, when the slot is resonant, Im(Y(11)) =0 

¼Lg 

½ Lg 

Lg: Guided wave 

wavelength 

Rang 

Test Port 

Short 

length



• Inclined angle 

changes from 10 

degree to 35 degree, 

5 degree step 

• Optimize resonant 

length at every 

inclined angle


Generate Slot Design Curve 

• Resonant length of wave guide slot vs. Inclined Angle


Waveguide Slot Array Antenna Simulation 

• The whole simulation 

model in HFSS v9, 

Frequency is 3cm band 

• All coupling between the 

slots are taken into account 

• More than 200 radiation 

slots and 40 coupling slots 

• Very large in electric size 

• Symmetry can be used to 

reduce computation time



• 3D radiation pattern 

when two ports are in 

same phase 

• Simulation time(PC): 

• 2:30 CPU time 

• 212,305 Tetrahedral



• 3D radiation pattern when 

two ports are 180 degree 

different in phase 

• Zero lobe in Z axies 

• Being a frequency domain 

solve, HFSS can get this 

without re-solve the project: 

just set the phase of the 

ports



• Compare with test result (two ports in 

same phase) 

• Simulation Result: 

• 3dB lobe width: 3.7 degree 

• back lobe level: -34dBc 

• Test Result: 

• 3dB lobe width: 3.67 degree 

• back lobe level: -34dBc

Rapid Direction Finding 

Antenna Array Design

The Principle of Direction Finding 

• In the traditional interferometer 

Direction-Finding 

r 1 

r 0 

r 2 

4# 

1# 

 

D 

2# 

3#

The Principle of Direction_Finding 

• The electric field of “incident wave” at the various 

antennas is as follows: 

E 

jIl sin θ k 

4π 

ωε 

× k 

r 

θ i = 

exp( − jkr i) 

i = (1,2,3,4 ) 

i 

E 

θi 

= 

E ( r 0) 

exp( − jkr i) 

• The propagating path differences between various 

antennas by the “incident wave” 

φ 

φ 

12 

34 

2πD 

= sinϕ 

cosϑ 

λ 

2πD 

= cosϕ 

cosϑ 

λ 

D—length of the baseline, —wavelength ,—the elevation 

of “incident wave”,—the azimuth of “incident wave”

The Principle of 

Direction_Finding 

• The azimuth of “incident wave” 

ϕ = 

φ 

arctg( 

φ 

12 

34 

) 

• The accuracy of DF is very low when the incident wave 

comes from the specific direction (in parallel with the 

baselines)

The PPD of pair at the invariant D 

• The propagating path difference (PPD)VS the azimuth 

angle of “incident wave” 

012.9 

All terminals load 50Ω 

03.3


• The propagating path difference VS the azimuth angle 

of “incident wave” 

06.9 

0-28.7 

037.3 

Pair terminals load 50Ω

The Principle of High DF 

Accuracy 

• Muti-coordinates systems can be implemented by 

rotating 

• DF baseline (AiBi) system, 

2 

A 

4 

A3 

A 2 

B 

n 

1 3 

A1 

B 1 

A n 

B 2 

n 4 

B4 

F1 

B 3

Design DF Array Completely in Software 

• Obtain the high DF antenna array system 

• using muti-coordinates systems theory 

• Design parameters of the length of baseline, antenna and 

matching and compensating network using calibration projects 

• Simulate phase 

• Distortion of the 

• incident wave in 

• a real DF system 

• Obtain the phase characteristic of 

any array with coupling between 

• antennas by any incident 

• wave in the real DF system .




02.5 

03.2 

pair terminals are opened




09.3 

0-2 

All terminals are opened 

09.7

The PPD of pair at the variant D 



5.58.3 

-2.9-27 

pair terminals load 50Ω 

3176.7




03.4 

0-1 

pair terminals load 50Ω 

0-37.3


• So, it is the effective way to improve the DF 

accuracy 

• to enlarge the length of the baseline 

We find that 

When D = 0 .5m 

= 0.17λ The PPD are extended to 176.7 

When D = 0.5λ The PPD are extended to 130 

or, reduced to 70 

When D →1λ The PPD’s are almost equal to 0

The PPD of pair at the Five Array 



-0.8-5.5 

0.96.5 

02.8 

All terminals load 50Ω,D=3m

The PPD of pair at the Five Array 



1.5-6 

1.842 

-0.8-18,0.415 

All terminals load 50Ω,D=3m

The Matching and Compensating 

Network 

• The topological chart of antenna matching 

n:1 

n:1 

R 

L 1 

L 2 

 

L 

C 

R 

 

n:1 

 

n:1 

R 1 

L R 2 

R 

C 

L

The Five Cells Array of DF 

• All terminals load matching and compensating 

Network ,D=3m 

R 1 

41 

L R 2 

Z 0 

=50Ω 

R 1 

antenna cell with 

matching network 

the azimuth angle of “incident wave”


• The PPD VS the azimuth angle of “incident wave” 

All terminals load matching 

and compensating network , 

D=3m 

2.32.8 

-1.92.9


• The PPD VS the azimuth angle of “incident wave” 

All terminals load matching 

and compensating network , 

D=3m 

-2.29.2 

-230


• The error of the PPD VS the azimuth angle of 

“incident wave”

Satellite Communication Antennas 

Simulation


Simulation(1) 

• Initial Design 

• Scalar Horn 

Antenna


Simulation(1) 

• Radiation pattern 

• Simulation time: 

• 00:5:15 CPU time 

• 00:2:38 real time on dual 

CPU computer 

• 17,433 tetrahedral


Simulation(1) 

• Add a dielectric len on 

the horn


Simulation(1) 

• The radiation pattern on 

Phi=90degree is expanded 

• Simulation time: 

• 00:9:05 Simulation time on 

Desktop PC 

• 30,028 Tetrahedral


Simulation(2) 

• The initial design 

• Circle Waveguide feeded 

• Cone and the Circle plane reflector


Simulation(2) 

• Initial Design result 

• The radiation pattern does not meet design goal 

• The VSWR is OK, but the best t is not at the desired 

frequency 

Best frequency 

Desired working 

frequency


Simulation(2) 

• At the best VSWR frequency, 

the radiation pattern seems 

closer to the desired


Simulation(2) 

• Improved design 

• We get the desired radiation 

pattern 

• All this can be done in one 

morning


Rotary Joint Optimization 

• Initial Design in HFSS v8.5

Rotary Joint Simulation and 

Optimization



• Model in HFSS v9 

• Direct parametric 

• Easier to optimize



• Optimized result 

• From 3.01GHz to 

3.62GHz VSWR



• Phase animation in 

HFSS v9 post 

processor 

• From the Complex Mag 

E plotting, we can get 

and calculate the 

maximum work power of 

this device: 103KW

Conclusion 

• HFSS: the golden tool for 

Microwave Component Design 

• Accuracy, reliable and fast 

• Real Arbitrary 3D Structure 

• You Build the Structure, Ansoft 

Solve the Maxwell’s Equation 

• Happy Electromagnetics Design!

Ansoft Designer

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