실험(6) 6주차 – Design of Array Antenna

실험(6) – IT시스템종합설계

HONGIK UNIVERSITY

2

Introduction

• Single element vs Array antenna

Dipole

J

J 🡪 E

H

H

E

Plane wave

(Parallel E/H-field to antenna)

Radiation pattern

of dipole/monopole

Phased array antenna

Radiation pattern

of array antenna

실험(6) – IT시스템종합설계

HONGIK UNIVERSITY

3

AESA radar

by Hanwha Systems Co. Ltd.

Autonomous vehicle

Adapted from “Radar Solution

RH850/V1R-M,” by Renesas Electronic Co.

Satellite radar

Adapted from “Korea Multi Purpose

Satellite ,” by Korea Aerospace Ind. Ltd

Introduction

• Applications

Base station

by Korea Telecom Co. Ltd.

실험(6) – IT시스템종합설계

HONGIK UNIVERSITY

4

Array Factor

Z_S

Z_r

Arm 1

Arm 2

Z_S

Z_r

y

z

x

θ

Pattern of

array antenna

• Basis of array factor

N: number of antenna

d: distance between antennas [meter]

d cosθ: delay distance

Plane wave

θ₀: intended angle for beamforming [ ° ]

Input parameters

Array factor:

배열에 따른 방사패턴 척도

🡪 if, θ₀ = 30°, peak of AF is observed at 30°.

실험(6) – IT시스템종합설계

HONGIK UNIVERSITY

5

Array Factor

y

z

x

θ

• Equation of array factor

N: number of antenna

d: distance between antennas [meter]

θ₀: intended angle for beamforming [ ° ]

Input parameters

= delay distance

E-field [V/m]

Propagation direction [/λ₀]

Wavefront

E-field [V/m]

Wavefront

Ψ : phase difference of the incident wavefront at each antenna [per λ₀ , rad or °]

Wavefront

Propagation direction [/λ₀]

2π

2π

π

π

0

0

1

1

E-field [V/m]

Propagation direction [/λ₀]

Wavefront

2π

π

0

2

E-field [V/m]

Propagation direction [/λ₀]

Wavefront

2π

π

0

antenna 1

antenna 1

antenna 2

antenna 2

Total field (Null)

Total field (Peak)

Example 2 (Ψ =180°)

Example 1 (Ψ =0°)

실험(6) – IT시스템종합설계

HONGIK UNIVERSITY

6

N: number of antenna

d: distance between antennas [meter]

θ₀: intended angle for beamforming [ ° ]

Input parameters

d cosθ: delay distance

Wavefront

Array Factor

• Equation of array factor

kd cosθ: phase difference between adjacent antennas [per λ₀ , rad or °]

(θ: angle of radiation pattern)

β : phase difference for the reference

(if, kd cosθ + β = 0°, optimum)

Example (N =4, d =0.5λ₀, θ₀ =0°)

θ [°]

AF [dB]

실험(6) – IT시스템종합설계

HONGIK UNIVERSITY

7

Calculate Array Factor with MATLAB

clc

clear all

close all

​

% 1D Arrayantenna gain[dB] 2D plot�% N : element number / d : element distance

N=4; d=0.5;

​

% steering angle

steering_angle=0;

​

AF=zeros(1,181);

​

for theta=1:181

for n=1:N

element(n,theta) = exp(j*(n-1)*(2*pi*d*(sind((theta-91))-sind(steering_angle))));

AF(1,theta) = AF(1,theta) + element(n,theta);

mag_element(n,theta) = abs(element(n,theta)); % magnitude of each element

pha_element(n,theta) = angle(element(n,theta))*180/pi; % phase of each element

end

end

​

AF=abs(AF); % array factor for magnitude

AF=20*log10(abs(AF)); % array factor for dB

�x=-90:90;

�plot(x,AF, ’LineWidth’,6);

​

grid on

hold on

axis([-90,90,-20,30])

y

z

x

θ

실험(6) – IT시스템종합설계

HONGIK UNIVERSITY