at any instant in time as a reference it will be observed that the phase shift of the transmitted radar signal received at the guided missile 14 is a function of the propagation delay of such signal in traveling from the control radar 10 to the guided missile 14 similarly the phase shift of the echo signal received at the guided missile 14 is a function of the sum of the propagation delay of the transmitted radar signal in traveling from the control radar 10 to the target 16 and the propagation delay of the echo signal in traveling from the target 16 to the guided missile 14 it will also be observed that the amplitude of the transmitted radar signal received at the guided missile 14 is greater than the amplitude of the echo signal until such missile enters the terminal phase of its flight with the foregoing in mind it will be obvious that the missile electronics 18 must if the frequency modulation on the transmitted radar signal is to be used be adapted to shift phase and change amplitude to form a replica of the frequency modulation on the echo signal referring now to fig1 a it should first be noted that the representation of the missile electronics 18 in the figure has been limited to a showing of only the elements which are required for an understanding of this invention thus the missile electronics 18 shown in fig1 a consist of a rear receiver 20.