phased array antenna simulation

i want to simualte antenna radition pattern of radar rx antenna using 8 element linear antenna (as shown in figure 2).i could able to create the required radiation pattern by placing the antenna element on Y axis(ref figure 1) ,(Matlab code is attached for reference):

%%%%%%%%%START of matlab code for antenna element placing on Y axis %%%%%%%%%%%%%

clc;

clear all;

close all;

%fc = 77e9;

fc = 60e9;

%c = 3e8;

c = physconst('LightSpeed');

lambda = c/fc;

Nt = 2;

Nr = 4;

ang = -90:90;

% % If both arrays have half-wavelength spacing, which are sometimes referred to as full arrays,

% % then the two-way pattern is close to the receive array pattern.

dr = lambda/2;

dt = Nr*(lambda/2);

Vy_pos1 = [0;-lambda;0];

Vy_pos2 = [0;-lambda+(lambda/2);0];

Vy_pos3 = [0;-lambda+ 2*(lambda/2);0];

Vy_pos4 = [0;-lambda+ 3*(lambda/2);0];

Vy_pos5 = [0;-lambda+ 4*(lambda/2);0];

Vy_pos6 = [0;-lambda+ 5*(lambda/2);0];

Vy_pos7 = [0;-lambda+ 6*(lambda/2);0];

Vy_pos8 = [0;-lambda+ 7*(lambda/2);0];

vxarray_4 = phased.ConformalArray('ElementPosition',[Vy_pos1,Vy_pos2,Vy_pos3,Vy_pos4,Vy_pos5,Vy_pos6,Vy_pos7,Vy_pos8]);

figure

viewArray(vxarray_4 ,'ShowIndex','All','ShowNormal',true,'Title',' conformal virtual array ,aantenna elements placed on Y axis');

patv_4 = pattern(vxarray_4,fc,ang,0,'Type','powerdb');

figure;

helperPlotMultipledBPattern(ang,[patv_4],[-30 0],...

{'Two-way Pattern','Virtual Array Pattern'},...

'Patterns of thin/full arrays and virtual array',...

{'-','--'},[1 2]);

%%%%%%%%%End of matlab code for antenna element placing on Y axis %%%%%%%%%%%%%

But my requirement is to achieve the same radaiation pattern by keeping antenna elements placement on X axis insetad of Y axis.please kindly check and confirm on how to realise same pattern by placing antenna element on the X axis(instead of y axis)?

i tried to place antenna elements on X axis and try to plot the resultant pattern but it doesnot meet the my required pattern.

figures and codes of the same are attached for reference.

%%%%%%%%%START of matlab code for antenna element placing on X axis %%%%%%%%%%%%%

clc;

clear all;

close all;

%fc = 77e9;

fc = 60e9;

%c = 3e8;

c = physconst('LightSpeed');

lambda = c/fc;

Nt = 2;

Nr = 4;

ang = -90:90;

% % If both arrays have half-wavelength spacing, which are sometimes referred to as full arrays,

% % then the two-way pattern is close to the receive array pattern.

dr = lambda/2;

dt = Nr*(lambda/2);

Vx_pos1 = [-lambda;0;0];

Vx_pos2 = [-lambda+(lambda/2);0;0];

Vx_pos3 = [-lambda+ 2*(lambda/2);0;0];

Vx_pos4 = [-lambda+ 3*(lambda/2);0;0];

Vx_pos5 = [-lambda+ 4*(lambda/2);0;0];

Vx_pos6 = [-lambda+ 5*(lambda/2);0;0];

Vx_pos7 = [-lambda+ 6*(lambda/2);0;0];

Vx_pos8 = [-lambda+ 7*(lambda/2);0;0];

vxarray_3 = phased.ConformalArray('ElementPosition',[Vx_pos1,Vx_pos2,Vx_pos3,Vx_pos4,Vx_pos5,Vx_pos6,Vx_pos7,Vx_pos8]);

figure

viewArray(vxarray_3 ,'ShowIndex','All','ShowNormal',true,'Title',' conformal virtual array ,antenna elements placed on X axis');

patv_3 = pattern(vxarray_3,fc,ang,0,'Type','powerdb');

figure;

helperPlotMultipledBPattern(ang,[patv_3],[-30 0],...

{'Two-way Pattern','Virtual Array Pattern'},...

'Patterns of thin/full arrays and virtual array',...

{'-','--'},[1 2]);

%%%%%%%%%End of matlab code for antenna element placing on X axis %%%%%%%%%%%%%

please kindly check and confirm on how to realise rquired pattern by placing antenna element on the X axis(instead of y axis)?

Answer 1

[Honglei Chen]

You can set the ArrayAxis in phased.ULA to 'x' to achieve that.

Hope this helps

[Mani]

Hi honglei, I have already tried placing arrayaxis in phased.ula to x axis (Please refer matlab Code attached Above under title "%%%%%%%%START of matlab code for antenna element placing on X axis %%%%%%%%%%%%%" This gives different radiation pattern than what I get with placing on y axis..

So I want to achieve same radiation pattern by placing on x x axis too..how to do ?please check and know ,any mistake I did in my code.. Regards, Mani

[Honglei Chen]

In general if you put elements on x axis, then the pattern would be different. Could you explain what you mean by "the same radiation pattern"? If it's the same shape but rotated then that's possible. Otherwise, in general it is not expected that the two patterns can match.

Also, when I mentioned seeting the array axis to 'x', I meant

phased.ULA('ArrayAxis','x')

[Mani]

hi honglei,

i m just adding few more additional information here over the reply i have sent it via mail in the morning.this info might helpful to get better understanding on my requirement and issue.

i have just used the matlab example "increasing angular resolution with virtual arrays"- this example shows how to simulate a coherent MIMO radar signal processing chain using Phased Array System Toolbox.

my requirement also same simulating radar model to detect the target present infront of the antenna.only changes need is antenna element placement on the X-axis instead of Y-axis and try to detect the targets.

(i have attached the matlab example code below for your reference

%%%%%%%%%%% start of matlab increasing angular resolution with virtual arrays example %%%%%%%%

clc;

close all;

clear all;

%%%%%%%%%%%%%%%% TDM MIMO MATLAB EXAMPLE %%%%%%%%%

% the two-way pattern of a conventional phased array radar. The two-way pattern of a phased array radar is the product of its transmit array pattern and receive array pattern. For example,

% consider a 77 GHz millimeter wave radar with a 2-element transmit array and a 4-element receive array.

fc = 77e9;

c = 3e8;

lambda = c/fc;

Nt = 2;

Nr = 4;

% % If both arrays have half-wavelength spacing, which are sometimes referred to as full arrays,

% % then the two-way pattern is close to the receive array pattern.

dt = lambda/2;

dr = lambda/2;

%%%%%%%%% to place antenna elements on y axis %%%%

txarray = phased.ULA(Nt,dt,'ArrayAxis','y');

rxarray = phased.ULA(Nr,dr,'ArrayAxis','y');

%%%%%%%%% to place antenna elements on X axis %%%%

% txarray = phased.ULA(Nt,dt,'ArrayAxis','x');

% rxarray = phased.ULA(Nr,dr,'ArrayAxis','x');

ang = -90:90;

pattx = pattern(txarray,fc,ang,0,'Type','powerdb');

patrx = pattern(rxarray,fc,ang,0,'Type','powerdb');

pat2way = pattx+patrx;

helperPlotMultipledBPattern(ang,[pat2way pattx patrx],[-30 0],...

{'Two-way Pattern','Tx Pattern','Rx Pattern'},...

'Patterns of full/full arrays - 2Tx, 4Rx',...

{'-','--','-.'});

% % If the full transmit array is replaced with a thin array, meaning the element spacing is wider than half wavelength, then the two-way pattern has a narrower beamwidth.

% % Notice that even though the thin transmit array has grating lobes, those grating lobes are not present in the two-way pattern.

dt = Nr*lambda/2;

txarray = phased.ULA(Nt,dt);

pattx = pattern(txarray,fc,ang,0,'Type','powerdb');

pat2way = pattx+patrx;

figure

helperPlotMultipledBPattern(ang,[pat2way pattx patrx],[-30 0],...

{'Two-way Pattern','Tx Pattern','Rx Pattern'},...

'Patterns of full/full arrays - 2Tx, 4Rx',...

{'-','--','-.'});

varray = phased.ULA(Nt*Nr,dr);

patv = pattern(varray,fc,ang,0,'Type','powerdb');

figure

helperPlotMultipledBPattern(ang,[pat2way patv],[-30 0],...

{'Two-way Pattern','Virtual Array Pattern'},...

'Patterns of thin/full arrays and virtual array',...

{'-','--'},[1 2]);

%%%%%% TDM-MIMO Radar Simulation%%%%

waveform = helperDesignFMCWWaveform(c,lambda);

fs = waveform.SampleRate;

transmitter = phased.Transmitter('PeakPower',0.001,'Gain',36);

receiver = phased.ReceiverPreamp('Gain',40,'NoiseFigure',4.5,'SampleRate',fs);

txradiator = phased.Radiator('Sensor',txarray,'OperatingFrequency',fc,...

'PropagationSpeed',c,'WeightsInputPort',true);

rxcollector = phased.Collector('Sensor',rxarray,'OperatingFrequency',fc,...

'PropagationSpeed',c);

radar_speed = 100*1000/3600; % Ego vehicle speed 100 km/h

radarmotion = phased.Platform('InitialPosition',[0;0;0.5],'Velocity',[radar_speed;0;0]);

car_dist = [40 50]; % Distance between sensor and cars (meters)

car_speed = [-80 96]*1000/3600; % km/h -> m/s

car_az = [-10 10];

car_rcs = [20 40];

car_pos = [car_dist.*cosd(car_az);car_dist.*sind(car_az);0.5 0.5];

cars = phased.RadarTarget('MeanRCS',car_rcs,'PropagationSpeed',c,'OperatingFrequency',fc);

carmotion = phased.Platform('InitialPosition',car_pos,'Velocity',[car_speed;0 0;0 0]);

channel = phased.FreeSpace('PropagationSpeed',c,...

'OperatingFrequency',fc,'SampleRate',fs,'TwoWayPropagation',true);

rng(2017);

Nsweep = 64;

Dn = 2; % Decimation factor

fs = fs/Dn;

xr = complex(zeros(fs*waveform.SweepTime,Nr,Nsweep));

w0 = [0;1]; % weights to enable/disable radiating elements

for m = 1:Nsweep

% Update radar and target positions

[radar_pos,radar_vel] = radarmotion(waveform.SweepTime);

[tgt_pos,tgt_vel] = carmotion(waveform.SweepTime);

[~,tgt_ang] = rangeangle(tgt_pos,radar_pos);

% Transmit FMCW waveform

sig = waveform();

txsig = transmitter(sig);

% Toggle transmit element

w0 = 1-w0;

txsig = txradiator(txsig,tgt_ang,w0);

% Propagate the signal and reflect off the target

txsig = channel(txsig,radar_pos,tgt_pos,radar_vel,tgt_vel);

txsig = cars(txsig);

% Dechirp the received radar return

rxsig = rxcollector(txsig,tgt_ang);

rxsig = receiver(rxsig);

dechirpsig = dechirp(rxsig,sig);

% Decimate the return to reduce computation requirements

for n = size(xr,2):-1:1

xr(:,n,m) = decimate(dechirpsig(:,n),Dn,'FIR');

end

end

xr1 = xr(:,:,1:2:end);

xr2 = xr(:,:,2:2:end);

xrv = cat(2,xr1,xr2);

nfft_r = 2^nextpow2(size(xrv,1));

nfft_d = 2^nextpow2(size(xrv,3));

figure

rngdop = phased.RangeDopplerResponse('PropagationSpeed',c,...

'DopplerOutput','Speed','OperatingFrequency',fc,'SampleRate',fs,...

'RangeMethod','FFT','PRFSource','Property',...

'RangeWindow','Hann','PRF',1/(Nt*waveform.SweepTime),...

'SweepSlope',waveform.SweepBandwidth/waveform.SweepTime,...

'RangeFFTLengthSource','Property','RangeFFTLength',nfft_r,...

'DopplerFFTLengthSource','Property','DopplerFFTLength',nfft_d,...

'DopplerWindow','Hann');

[resp,r,sp] = rngdop(xrv);

plotResponse(rngdop,squeeze(xrv(:,1,:)));

respmap = squeeze(mag2db(abs(resp(:,1,:))));

ridx = helperRDDetection(respmap,-10);

xv = squeeze(sum(resp(ridx,:,:),1))';

doa = phased.BeamscanEstimator('SensorArray',varray,'PropagationSpeed',c,...

'OperatingFrequency',fc,'DOAOutputPort',true,'NumSignals',2,'ScanAngles',ang);

[Pdoav,target_az_est] = doa(xv);

fprintf('target_az_est = [%s]\n',num2str(target_az_est));

doarx = phased.BeamscanEstimator('SensorArray',rxarray,'PropagationSpeed',c,...

'OperatingFrequency',fc,'DOAOutputPort',true,'ScanAngles',ang);

Pdoarx = doarx(xr);

figure

helperPlotMultipledBPattern(ang,mag2db(abs([Pdoav Pdoarx])),[-30 0],...

{'Virtual Array','Physical Array'},...

'Spatial spectrum for virtual array and physical array',{'-','--'});

%%%%%%%%%%% End of matlab increasing angular resolution with virtual arrays example %%%%%%%%

Note: antenna placement axis can be changed in the above code by commenting/uncommenting phased.ULA code line in the above code.

my question:

1. with antenna elements placed on Y-axis ,target Azimuth angles are estimated

target_az_est = [-6 10] correctly close to theortical values car_az = [-10 10] in the initial position.

but with antenna elements placed on X-axis ,target Azimuth angles are estimated

target_az_est = [72 16] incorrectly compare to theortical values of car_az = [-10 10] in the initial position.

its clear that this incorrect estimation is happening due to antenna pattern only,

my requirement is to detect the target azimuth angle correctly with antenna elements placed on X-axis.

please check and let me know how to do it? and what changes need to be done in the code?

Regards,

Mani