Antenna Design

Lab 11 - Loop Antenna

 I. Simulation

Design frequency: f ₀ = (1000 + PIN/10000) MHz; 실습조교 PIN = 0000

Loop material: PEC

Source: discrete port

b = λ₀ / 6 = 50 mm  (λ₀ = c / f₀ )

a = b/50 = 1 mm

Feed gap = 2a

Simulation frequency range: Frequency range: 0.2f₀ - 1.5f₀

Solver: Time Domain Solver

Time Domain Solver Parameters: Accuracy = -80 dB

(1) Make the Loop antenna

Modeling, (Torus) 고리 아이콘 선택, ESC 키, Name: solid1, Orientation: Z

Large radius: 51, Small radius: 49

(2) Make the feed gap

Modeling, Brick 아이콘 선택, ESC 키, Name: solid2

Navigation Tree, Components, component1, Loop antenna 클릭

Modeling, Boolean, Subtract, feed gap, 엔터키

3) 포트설정

Modeling, Pick Points, Pick Face Center, gap 한면에 마우스 위치후 더블클릭

Pick Points, Pick Face Center, gap 한면에 마우스 위치후 더블클릭

Simulation, Discrete Port

4) 시뮬레이션 설정

주파수 설정:

Simulation, Frequency, Min. frequency: 0.2, Max. frequency: 1.5

필드 모니터 설정:

Simulation, Field Monitor, E-field, Frequency, Frequency:1, Apply

Simulation, Field Monitor, H-field and Surface current, Frequency, Frequency:1, Apply

Simulation, Field Monitor, Far field/RCS, Frequency, Frequency:1, Apply

메쉬 설정(메모리가 부족하거나, 학생버전에서):

Simulation, Global Properties,

Cells per wavelength: 5

Cells per max model box edge: 5

Fraction of maximum cell near to model: 5

5) 시뮬레이션

Simulation, Setup Solver

Time Domain Solver Parameters: Accuracy = -80 dB

1. Plot the antenna structure

2. |S11| analysis

1) Plot |S11| (dB) at 0.2 - 1.2 GHz.

2) Find the frequency for minimum |S11|. It happens when the loop circumference is one wavelength.

     |S11| = |S11|_min  at f = ( 0.95   ) GHz

Right click, Add Curve Marker, place the mouse pointer on the curve and double click

3) Plot S11 on the Smith chart. Mark the frequency f₀ on the S11 curve.

4) Find Z11 at f₀.

     Z11 = (162.84     ) + j (  43.57  ) Ω

3. Z11 (Input impedance) analysis

1) Plot Re(Z11) and Im(Z11) on a same graph.

2) Find the first resonant frequency f₁ where the antenna can be modelled as a parallel resonant circuit. It happens when the loop circumference is a half wavelength. Find Z11 at f₁.

     f₁ = (   0.402  ) GHz

     Z11 = (35647) + j (0) Ω

3) Find the seconde resonant frequenc f₂ where the antenna can be modeled as a series resonant circuit. It happens when the loop circumference is one wavelength. Find Z11 at f₂.

     f₂ = (0.966) GHz

     Z11 = (137) + j ( 0)  W

4. Find the small loop impedance

Z11 = ( 1.33) + j ( 461) W at 0.2f₀.

5. Check the current distribution on the loop antenna.

1) Plot the surface current on the loop at 0.5f₀.

2) Plot the surface current on the loop at f₀.

6. Investigate 3D far-field directivity patterns.

1) Dabs, Dtheta, Dphi at 0.5f₀.

2) Dabs, Dtheta, Dphi at f₀.

II. Discussions

1. Find the accurate resonant length and resistance of a full-wavelength loop.

2. What is the directivity of a full-wavelength loop.