Antenna Design

Lab 13 - Small Antenna Impedance Matching

Simulation Guide

I. Simulation

Design frequency: f ₀ = (300 + PIN/10000) MHz; 실습조교 PIN = 0000

Antenna material: copper

Source: discrete port

1. Short Dipole and Impedance Matching

Wavelength: 1 m

Dipole length L: 0.1 wavelength

Wire diameter d: 0.001 wavelength

Feed gap g: 0.001 wavelength

Wire material: copper (conductivity 5.7 × 10⁷ S/m)

Simulation frequency range: 0.93 f₀ - 1.07 f₀ (280-320 MHz)

Impedance matching frequency: f₀ (300 MHz)

Figure: Left = a short dipole antenna, Right = Short dipole with matching elements. Inductors L/2 are inserted in the dipole wire while the capacitor C is connected across the feed gap in parallel with the discrete port.

For the dipole antenna without matching elements,

1) Plot the antenna geometry.

(1) Make a project template.

Project Template

New Template, Microwaves & RF / Optical, Anennas

Create Project Template: Wire, Time Domain

Units: default (mm, GHz)

Frequency Min. : 0.28 GHz

Frequency Max. : 0.32 GHz

Monitors: E-field, H-field, Farfield

Defined at: 0.3 GHz

Template name: short dipole

(2) Make a dipole antenna structure.

A. Make one short the dipole wire using parameter symbols.

Modeling, Cylinder icon, ESC key, Name: solid1, Orientation: Z

Outer radius: d/2, Inner radius: 0

X center:0      Y center:0

Z min: -L/2      Z max : L/2

Material : Copper (annealed)

Wire diameter: 0.001 wavelength

Dipole length: 0.1 wavelength

+

Material: copper

Load from Material Library

B. Make a feed gap

Modeling, Cylinder icon, ESC key, Name: solid2, Orientation: Z

Outer radius: d/2, Inner radius: 0

X center:0      Y center:0

Z min: -g/2      Z max : g/2

Material : Vacuum

Feed gap: 0.001 wavelength

Ok

Shape intersection: Cut away highlighted shape

(3) Add an antenna source. Set up a discrete port.

A. Specify the surfaces between which a discrete port is to be applied.

Modeling

Picks, Pick Points, Pick Face Center

Place the mouse point on the one of gap faces and then double click.

(4) Simulate

Simulation, Setup Solver, Start

(5) Plot the geometry

2) Plot S11 on the Smith chart.

1D Results, S-Parameters

RESULT TOOLS, 1D Plot, Z Smith Chart

3) Plot |S11|(dB) Cartesian.

4) Plot the real and imaginary parts of Z11.

1D Results, Z Matrix, Real and Imaginary

5) Find the antenna input impedance Z11 at f₀.

Z11의 Real/Imaginary plot에서 우클릭, Axis Maker, Pos.: 0.3

Axis Marker 주파수 (0.3 GHz)에서 표시되는 값 기록

Z11 = (1.72) + j (-1140) W

For the dipole with matching elements,

6) Find the matching circuit element values (the first solution).

이론 부분의 ant-imped-match.exe 프로그램을 다운로드 후 실행

실행창 글꼴색, 바탕색 변경: 기본은 글꼴 백색, 바탕 흑색이라서 문서에 삽입하기 부적합

실행창 위 테두리에 커서 두고 우클릭

[속성], [색]

[화면 텍스트(T)] 선택 후 흑색 선택

[화면 배경(B)] 선택 후 백색 선택

ant-imped-match.exe을 실행하여 1st SOLUTION의 matching element 값 기록

L = ( 0.609 ) uH

C = ( 56.2 ) pF

7) Add matching circuit elements and simulate the structure. Plot the antenna geometry.

(1) 안테나 정합용 인덕터를 직렬로 연결하기 위한 gap을 다이폴에 생성

Ok

Shape intersection: Cut away highlighted shape

Ok

Shape intersection: Cut away highlighted shape

(2) 임피던스 정합 소자 연결

Navigation Tee, click the Lumped Elements, the right mouse button

New lumped element

Element1 is C(Capacitor)

(3) Plot the antenna structure in a 3D form.

(4) Simulate

Simulation, Discrete Port

Simulation, Setup Solver, Start

8) Plot S11 on the Smith chart.

1D Results, S-Parameters

RESULT TOOLS, 1D Plot, Z Smith Chart

9) Plot |S11|(dB) Cartesian after matching.

1D Results, S-Parameters

RESULT TOOLS, 1D Plot, dB icon

10) Find the 10-dB bandwidth

Plot |S11|(dB) at 0.31-0.32 GHz and use Measure Lines.

10-dB bandwidth = ( 0.29 ) MHz

10-dB bandwidth = ( 0.096 ) %

2. Small Loop and Impedance Matching

Frequency: f₀ (300 MHz)

Wavelength: 1 m

Loop diameter: 0.1 wavelength

Wire diameter: 0.001 wavelength

Feed gap: 0.001 wavelength

Wire material: coppper

Simulation frequency range: 0.93 f₀ - 1.07 f₀ (280-320 MHz)

Impedance matching frequency: f₀ (300 MHz)

Figure: Small loop and impedance matching. Capacitors 2C₁ are inserted in the loop wire while the capacitor C₂ is connected across the feed gap in parallel with the discrete port.

For the small loop antenna without matching elements

1) Plot the antenna geometry.

(방법: 구조 그리기)

1) 루프생성

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

2) Feed gap 생성

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

Shape Intersection-> Cut away highlighted shape

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

2) Plot S11 on the Smith chart.

3) Plot |S11|(dB) Cartesian.

4) Plot the real and imaginary parts of Z11.

5) Find the antenna input impedance Z11 at f₀.

Z_A = ( 36 ) + j ( 2837 ) ohms

For the small loop antenna with matching elements

6) Find the matching circuit element values (the first solution).

C₁ = ( 0.188 ) pF

C₂ = ( 6.62 ) pF

7) Add matching circuit elements and simulate the structure. Plot the antenna geometry.

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

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

Simulation, Lumped Element

X1, X2 (-0.2)

X1, X2 (+0.2)

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

Shape Intersection-> Cut away highlighted shape

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

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

Simulation, Lumped Element

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

Shape Intersection-> Cut away highlighted shape

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

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

Simulation, Lumped Element

8) Plot S11 on the Smith chart.

9) Plot |S11|(dB) Cartesian after matching.

10) Find the 10-dB bandwidth

Plot |S11|(dB) at 0.29-0.30 GHz and use Measure Lines.

10-dB bandwidth = ( 0.9 ) MHz

10-dB bandwidth = ( 0.3 ) %