How to use beamformer in matlab 2016a using step()

Hi,

For an assignment I have to construct an ultrasound image from rawdata to an actual image showing a word. To construct this image I need to use beamforming, but I have the 2016a version which requires you to use the step() function. When I use this I get an error message: 'Error using phased.PhaseShiftBeamformer/step Not enough input arguments; expected 2 (in addition to the object handle), got 1.'

Does anybody know how to use beamforming and step()? My code is shown below.

Thanks in advance!

if true
  load('Lab2_BMD_course_Data.mat')
RFData=double(RFData);
Pitch = 0.3; % pitch
c0 = 1500; % speed of sound 
fs = 25e6; % sample frquency
fc=6.25e6;
dt=1/fc; % time between each sample
limits=[min(RFData(:)) max(RFData(:))];
depth = [0:c0*dt/2:(size(RFData,1)-1)*c0*dt/2];
D=RFData(:,64);
Dabs=abs(D);
for i=1:128
  [env1 env2]=envelope(RFData(:,i));
  totenv(:,i)=env1;
end
% Definition Elementposition
ElementPos =0:Pitch:127*Pitch;
ElementPos = ElementPos-mean(ElementPos);
% Preallocation of image
x=-20:0.1:20; 
z=0:0.1:50;
N=128; % number elements 
Image =zeros(length(z),length(x));
df=2e6;
lambda=c0/fc;
array=phased.ULA('NumElements',128,'ElementSpacing',Pitch);
array.Element.FrequencyRange=[fc-df fc+df];
beamformer=phased.PhaseShiftBeamformer;
beamformer.SensorArray=array;
beamformer.DirectionSource='Input port';
beamformer.WeightsOutputPort=true;
beamformer.WeightsNormalization='Preserve power';
beamformer.PropagationSpeed=c0;
beamformer.OperatingFrequency=fs;
% Y=step(beamformer,totenv);
test=totenv(:,64);
figure(4)
[y w]=step(beamformer,totenv);
end

Answer 1

[Honglei Chen]

You need to pass in an extra input representing the desired beamforming direction because you set the DirectionSource to 'Input port'.

HTH