clear?all;
%======================================================================
%%%?（I）?parameters‘?definition
%======================================================================
c=3e+8;			?%?speed?of?light
pi=3.1415926;	?	?%?pi
j00=sqrt（-1）;		?%?square?root?of?-1

res_a=1;		?%?required?azimuth?resolution
res_r=1;		?%?required?range?resolution
k_a=1.2;		?%?azimuth?factor
k_r=1.2;		?%?range?factor

Ra=4000.;		?%?radar?working?distance
va=76.;?????????????????????????%?radar/platform?forward?velocity
Tp=1.e-6;???????????????????????%?transmitted?pulse?width??????
fc=3e+9;????????????????????????%?carrier?frequency?
FsFactor?=?1.2;
theta=85*pi/180;		%?squint?angle?

%======================================================================

lamda=c/fc;			????%?wavelength
Br=k_r*c/2./res_r;??????????????????%?required?transmitted?bandwidth
Fs=Br*FsFactor;			????%?A/D?sampling?rate
bin_r=c/2./Fs;		????????????%?range?bin
Kr=Br/Tp;			????%?range?chirp?rate	??

La=Ra*k_a*lamda/2/res_a/sin（theta）;?%?required?synthetic?aperture?length
Ta=La/va;			????%?required?synthetic?aperture?time
fdc=2*va*cos（theta）/lamda;??????????%?doppler?centriod
fdr=-2*（va*sin（theta））.^2/lamda/Ra;	%?doppler?rate
Bd=abs（fdr）*Ta;				%?doppler?bandwidth
prf=round（Bd*2）;			%?PRF	

%======================================================================
%%%（II）?echo?return?modelling?（point?target）
%======================================================================

Na=fix（Ta*prf）;	???			%?azimuth?sampling?number
ta=（（1:Na）-Na/2）/prf;		????????%?slow?time?along?azimuth
xa=va*ta-Ra*cos（theta）;		????????%?azimuth?location?along?flight?track

%x0=[??0??0??0??0??0?];?????????????%?define?multi?points?if?you?want
%R0=[-20?-10?0?10?20?];?????????????%?x0:?azimuth?location?（positive?towards?forward?velocity）
????????????????????????????????????%?R0:?slant?range?location?（positive?towards?far?range）

x0=[?0??0??0??50];??R0=[?-200???-50??0??0];
Npt_num?=?length（x0）;

ra=zeros（Npt_num?length（xa））;??????%?calculate?every?point?target‘s?slant?range?history
for?i=1:Npt_num????????????????????????????????????
	ra（i:）=sqrt（（Ra*sin（theta）+R0（i））.^2+（xa+x0（i））.^2）;		?
end???

rmax=max（max（ra））;			%?max.?slant?range
rmin=min（min（ra））;			%?min.?slant?range
rmc=fix（（rmax-rmin）/bin_r）;		%?range?sample?number

rg=0*ra;???????