EMLAB 1 초고주파 통신 project 2015 년 2 학기. EMLAB 2 Antenna pattern synthesis.
12
EMLAB 1 초초초초 초초 project 2015 초 2 초초
-
Upload
ginger-howard -
Category
Documents
-
view
226 -
download
0
description
EMLAB 3 Antenna radiation pattern An antenna is a device that helps electrical signals to be radiated in the form of electromagnetic wave. It is well known that a time-varying current segment produces radiated emission which is axially symmetric along the direction of current, and the total radiated power is equal to the energy provided by the current source. If we want to transport substantial electromagnetic waves to the point farther away, we should confine the radiated energy to a region occupying narrow solid angle. There are many ways to squeeze the radiated waves into a narrow angular region. The most frequently used method is utilizing a number of identical antennas fed by current sources with different magnitudes and phase angles. Then, the total electromagnetic field can be obtained by adding up the contributions from each element antenna. Array factor
Transcript of EMLAB 1 초고주파 통신 project 2015 년 2 학기. EMLAB 2 Antenna pattern synthesis.
EMLAB
1
초고주파 통신 project
2015 년 2 학기
EMLAB
2
Antenna pattern synthesis
EMLAB
3Antenna radiation pattern
An antenna is a device that helps electrical signals to be radiated in the form of elec-tromagnetic wave. It is well known that a time-varying current segment produces ra-diated emission which is axially symmetric along the direction of current, and the total radiated power is equal to the energy provided by the current source. If we want to transport substantial electromagnetic waves to the point farther away, we should con-fine the radiated energy to a region occupying narrow solid angle. There are many ways to squeeze the radiated waves into a narrow angular region. The most frequently used method is utilizing a number of identical antennas fed by current sources with different magnitudes and phase angles. Then, the total electromagnetic field can be obtained by adding up the contributions from each element antenna.
N
n
xjkn
jkrN
nn
neIer
klj0
cos
0total sin
4ˆ
θEE
d
z
x0I 2I
xl
1I
d
Array factor
0x 1x 2x
EMLAB
4
If the observation point is far from the antenna array, the total electric field can be ap-proximated by the product of the field due to an element antenna and the ‘array factor’ which are the weighted sum of the element antenna current by the space factor.
N
n
xjkn
neIAF0
cos2
k
By adjusting element antenna current In and distance between element ‘d’, desired ra-diation patterns can be synthesized. The current In has complex value which has mag-nitude and phase.
If the phases and distances between adjacent elements are kept constant, the array fac-tor simplifies to
.0
N
n
jnn eIAF coskd
Top view
d
1R 2R1 2
1r 2r
r
Ox
r
EMLAB
5
(1) Two element array
Examples
2,1,1 10
dII
10
20
30
40
50
30
210
60
240
90
270
120
300
150
330
180 0
10
20
30
40
50
30
210
60
240
90
270
120
300
150
330
180 0
,12
,1,1
10
10
II
dII
(2) Two element array
EMLAB
6
10
20
30
40
50
30
210
60
240
90
270
120
300
150
330
180 0
10
20
30
40
50
30
210
60
240
90
270
120
300
150
330
180 0
(3) Five element array
,2
.1,1,1,1,1 44
33
2210
d
eIeIeIeII jjjj
(4) Five element array
0,2
.1,1,1,1,1 44
33
2210
d
eIeIeIeII jjjj
(5) Five element array
0,8.0.1,1,1,1,1 4
43
32
210
deIeIeIeII jjjj
10
20
30
40
50
30
210
60
240
90
270
120
300
150
330
180 0
3dB Beamwidth
Beam direction
EMLAB
7
(1) Adjust the number of element antennas (N+1), distances (d), phase differences (α), magnitudes of currents to change the radiation patterns.
Design procedures
Design constraint for antenna synthesis:
(1) 주파수 3.7GHz(2) Beam directions should be pointed to +30 ◦ and 135◦ ( 빔이 두개인 멀티 빔 안테나 ,
30 도 및 135 도에 대해 따로 전류를 구한 후 합하면 됨 .)(2) 3-dB Beam width of each beam should be 10◦.(3) Sidelobe 는 주 빔에 비해 30 dB 작음 .(Dolph-Chebyshev type)
EMLAB
8Project report
must include the following items.
(1) Radiation patterns.
(2) Currents of elementary antennas.
(3) Spacings between elementary antennas.
(4) Explanations on the pattern synthesis procedure.
EMLAB
9
clear;clf;
phi=0:0.01:2*pi; %0<phi<2*pilambda = 3e8/1e9; % 1GHzk=2*pi/lambda;d=0.5*lambda;% 0.5 lambda spacing.psi=k*d*cos(phi);
N=15; % number of element antennas.Currents = zeros(1,N);alpha = pi*0.3;
for n=1:N Currents(n) = exp(i*(n-1)*alpha);end
AF=freqz(Currents,1,psi); %Array factor for different phi values.
EF = sin(phi);EF = (EF>0.).*EF; %Element factor for different phi values.E = AF.*EF;
E = db(E)+30; % 최대값에서 30dB 작은 범위까지 그림 .E = (E>0.).*E;E = E-30;
polar(phi,E+30); %Generating the radiation pattern
Sample MATLAB codes
10
20
30
30
210
60
240
90
270
120
300
150
330
180 0
EMLAB
10
Filter synthesis
EMLAB
11설계 과제
비유전율 9.4, 두께 0.5mm 인 유전체 (Alumina) 와 2 온스 두께의 구리를 씌운 microstrip line 을 이용하여 band pass filter 를 설계하고자 한다 . 다음 조건을 만족할 수 있도록 coupled resonator filter 를 만들어라 .
(1) 통과 대역 주파수 : 3.65GHz~3.75GHz
(2) Fractional bandwidth : |S11| < -20dB
(3) Source/load impedance : 50 Ω
(4) 4th order Chebyshev filter
EMLAB
12Project report
리포트 필수 포함 사항
(1) Low pass filter prototype(2) Impedance inverter 로 변환한 회로도(3) Resonator 형태 제안(4) Resonator 하나만의 S-parameter 시물레이션 결과(5) 두 Resonator 간의 간격을 바꾸어 가며 coupling coefficients 를 계산한 결과 .(6) Whole filter layout and simulation results(7) Explanations on the filter synthesis procedure.
