an additional problem is that the imperfections frequency sweep nonlinearities of both the original transmit signal and the delayed version of the transmit signal l o must be closely matched in other words the two signals must be highly correlated at zero delay the receive signal and the lo signal can be compared electronically only during the period where both are ramping up in the present system hereinafter described this is the period referred to as the overlap prior art has resorted to using the signal labeled 34 transmit 34 as the lo fig1 shows that there is little overlap between this signal and the receive signal see p a but a large overlap can be achieved by generating a delayed version of the transmit signal see present this delayed version is shown in the figure as delayed and offset lo and achieves a large overlap with the receive signal an example of the radar 39 s strategy in using the delayed lo would be if it is decided to use the radar to look at targets at around e g 1 km the radar controller of fig2 and 3 would compute the time required for signals to return from targets at that range the delayed lo would then be triggered after that appropriate delay so that the lo ramp would coincide with those of the return signals the present system utilizes two linear frequency sweep generators lfsg generators as described in reference 2 and fig5 with the addition of circuitry that forces the imperfections to be matched it also includes an optional fiber optic delay line which can be used to improve the performance of the basic lfsg see fig2 and 3.