function b_ami( bitstream )
%B_AMI Bipolar Alternate Mark Inversion
% sample data:
% d = [ 0 1 0 0 1 1 0 0 0 1 1 ]
% usage:
% b_ami(d)
% author:
% Anastasios Latsas

% pulse height
pulse = 5;

% assume that current pulse level is a "low" pulse (binary 1)
% this is the pulse level for the bit before given bitstream
current_level = -pulse;

for bit = 1:length(bitstream)
% set bit time
bt=bit-1:0.001:bit;

if bitstream(bit) == 0
% binary 0, set to zero
y = zeros(size(bt));
else
% each binary 1 has the opposite pulse level from the previous
current_level = -current_level;
y = (bt<bit) * current_level;
end

% assign last pulse point by inspecting the following bit
try
% we care only about ones as they use alternate levels
if bitstream(bit+1) == 1
y(end) = -current_level;
end
catch e
% bitstream end; assume next bit is 0
y(end) = -current_level;
end

% draw pulse and label
plot(bt, y, 'LineWidth', 2);
text(bit-0.5, pulse+2, num2str(bitstream(bit)), ...
'FontWeight', 'bold')
hold on;
end
% draw grid
grid on;
axis([0 length(bitstream) -pulse*2 pulse*2]);
set(gca,'YTick', [-pulse 0 pulse])
set(gca,'XTick', 1:length(bitstream))
set(gca,'XTickLabel', '')
title('Bipolar Alternate Mark Inversion')
end

i needed it very much .................thanks alot sir........