%
% FUNCTION 2.6 : "cp0201_transmitter_2PPM_TH"
%
% Simulation of a UWB transmitter implementing 2PPM with TH
%
% Transmitted Power is fixed to 'Pow'.
% The signal is sampled with frequency 'fc'.
% 'numbits' is the number of bits generated by the source.
% 'Ns' pulses are generated for each bit, and these pulses
% are spaced in time by an average pulse repetition period
%  'Ts'.
% The TH code has periodicity 'Np', and cardinality 'Nh'.
% The chip time has time duration 'Tc'.
% Each pulse has time duration 'Tm' and shaping factor
%  'tau'.
% The PPM introduces a time shift of 'dPPM'.
%
% The function returns:
% 1) the generated stream of bits ('bits')
% 2) the generated TH code ('THcode')
% 3) the generated signal ('Stx')
% 4) a reference signal without data modulation ('ref')
%
% Programmed by Guerino Giancola
%

function [bits,THcode,Stx,ref]=cp0201_transmitter_2PPM_TH

% ----------------------------
% Step Zero - Input Parameters
% ----------------------------

Pow = -30;       % Average transmitted power (dBm)

fc = 50e9;       % sampling frequency

numbits = 2;     % number of bits generated by the source

Ts = 3e-9;       % frame time, i.e. average pulse
                 %  repetition period [s]
Ns = 1;          % number of pulses per bit

Tc = 1e-9;       % chip time [s]
Nh = 3;          % cardinality of the Time Hopping code
Np = 5;          % periodicity of the Time Hopping code

Tm = 0.5e-9;     % pulse duration [s]
tau = 0.25e-9;   % shaping factor for the pulse [s]   
dPPM = 0.5e-9;   % time shift introduced by the PPM [s]

G = 1;
% G=0 -> no graphical output
% G=1 -> graphical output

% ----------------------------------------
% Step One - Simulating Transmission Chain
% ----------------------------------------

% binary source
bits = cp0201_bits(numbits);

% repetition coder
repbits = cp0201_repcode(bits,Ns);

% Time Hopping code
THcode = cp0201_TH(Nh,Np);

% Pulse Position Modulation + TH
[PPMTHseq,THseq] = ...
   cp0201_2PPM_TH(repbits,fc,Tc,Ts,dPPM,THcode);

% Shaping filter
power = (10^(Pow/10))/1000;     % average transmitted power
                                %  (watt)
Ex = power * Ts;                % energy per pulse
w0 = cp0201_waveform(fc,Tm,tau);% Energy Normalized pulse
                                %  waveform
wtx = w0 .* sqrt(Ex);           % pulse waveform
Sa = conv(PPMTHseq,wtx);        % Output of the filter
                                %  (with modulation)
Sb = conv(THseq,wtx);           % Output of the filter
                                %  (without modulation)

% Output generation

L = (floor(Ts*fc))*Ns*numbits;
Stx = Sa(1:L);
ref = Sb(1:L);

% ---------------------------
% Step Two - Graphical Output
% ---------------------------

if G
    
F = figure(1);
set(F,'Position',[32 223 951 420]);

tmax = numbits*Ns*Ts;
time = linspace(0,tmax,length(Stx));
P = plot(time,Stx);
set(P,'LineWidth',[2]);
ylow=-1.5*abs(min(wtx));
yhigh=1.5*max(wtx);
axis([0 tmax ylow yhigh]);
AX=gca;
set(AX,'FontSize',12);
X=xlabel('Time [s]');
set(X,'FontSize',14);
Y=ylabel('Amplitude [V]');
set(Y,'FontSize',14);
for j = 1 : numbits
    tj = (j-1)*Ns*Ts;
    L1=line([tj tj],[ylow yhigh]);
    set(L1,'Color',[0 0 0],'LineStyle', ...
       '--','LineWidth',[2]);
    for k = 0 : Ns-1
        if k > 0
            tn = tj + k*Nh*Tc;
            L2=line([tn tn],[ylow yhigh]);
            set(L2,'Color',[0.5 0.5 0.5],'LineStyle', ...
               '-.','LineWidth',[2]);
        end
        for q = 1 : Nh-1
            th = tj + k*Nh*Tc + q*Tc;
            L3=line([th th],[0.8*ylow 0.8*yhigh]);
            set(L3,'Color',[0 0 0],'LineStyle', ...
               ':','LineWidth',[1]);
        end
    end
end

end % end of graphical output