EMLAB 1 초고주파 통신 project 2015 년 2 학기

EMLAB 2 Antenna pattern synthesis

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

EMLAB 4 If the observation point is far from the antenna array, the total electric field can be approximated 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. By adjusting element antenna current I n and distance between element ‘d’, desired radiation patterns can be synthesized. The current I n has complex value which has magnitude and phase. If the phases and distances between adjacent elements are kept constant, the array factor simplifies to Top view

EMLAB 5 (1) Two element array Examples (2) Two element array

EMLAB 6 (3) Five element array (4) Five element array (5) Five element array 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 8 Project 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*pi lambda = 3e8/1e9; % 1GHz k=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

EMLAB 10 Filter synthesis

EMLAB 11 설계 과제 비유전율 9.4, 두께 0.5mm 인 유전체 (Alumina) 와 2 온스 두께의 구리를 씌 운 microstrip line 을 이용하여 band pass filter 를 설계하고자 한다. 다 음 조건을 만족할 수 있도록 coupled resonator filter 를 만들어라. (1) 통과 대역 주파수 : 3.65GHz~3.75GHz (2)Fractional bandwidth : |S 11 | < -20dB (3)Source/load impedance : 50 Ω (4)4 th order Chebyshev filter

EMLAB 12 Project 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.