function compatible with other uses

src/new/IFOs/FT_GW_sidebands.m

 %--------------------------------------------------------------------------
-% function [Abs] = FT_GW_sidebands(lambda,h0,fsig,L,n)
+% function [Abs] = FT_GW_sidebands(lambda,h0,fsig,L,n,sb_sign)
 %
 % A function for Matlab which calculates the amplitude of the sidebands
 % created when a light beam travels along a path modulated by a
@@ -10,6 +10,9 @@
 % fsig:     Frequency of the gravitational wave [Hz]
 % L:        Length of the path [m]
 % n:        Index refection of the medium through which the beam travels
+% sb_sign:  Sign of the sideband
+%           1:  upper sideband
+%           -1: lower sideband
 %
 % Asb:      Amplitude of the sidebands [sqrt(W)]
 %
@@ -18,7 +21,16 @@
 %--------------------------------------------------------------------------
 %
 
-function [Asb] = FT_GW_sidebands(lambda,h0,fsig,L,n)
+function [Asb] = FT_GW_sidebands(lambda,h0,fsig,L,n,sb_sign)
+    
+    baseid = 'GW_sidebands';
+    
+    % Error meesgaes
+    if sb_sign~=1 && sb_sign~=-1
+        result='Invalid sideband sign: must be -1 (lower) or +1 (upper)';
+        msgid=[baseid,':checkarguments']
+        error(msgid,result);
+    end
 
     % Carrier light parameters
     c = 299792458;
@@ -31,5 +43,11 @@ function [Asb] = FT_GW_sidebands(lambda,h0,fsig,L,n)
     % Sideband amplitude
     Asb = (w0*h0./(2*wsig)) .* sin(wsig*L*n/(2*c));
     
+    % Phase
+    phi_sb = pi/2 - w0*L*n/c - sb_sign * wsig*L*n/(2*c);
+    
+    % Final sideband amplitude and phase
+    Asb = Asb.*exp(1i*phi_sb);
+
 end