phase noise and lock speed considerations a relatively high value of u03c9 n is required so that the frequency has been set as in fig1 the 90 khz oscillator 6 injects the test signal into the summing amplifier 5 voltage vd appears at the input to the summing amplifier and voltage v 1 at the output of a 1 a attenuator 7 following the summing amplifier at these points the voltages are very low on the order of 10 mv which is equivalent to a frequency modulation index of 0 05 in the millimeter wave oscillator this value is sufficiently low so as not to cause disturbance in most cases of operation with angle modulation in those cases where disturbance does still exist the frequency of the injected signal f m can be changed so that it is not in the transmitted information range in order to eliminate the disturbance each of these signals passes through a very narrow band pass filter 9 10 which filters the signal out of the large amount of noise these filters are implemented as active filters with very high q the filtered signals are supplied to sophisticated peak detectors 11 12 which convert them to dc voltages proportional to the signal levels the dc voltages are supplied to a differential amplifier 16 whose output voltage is proportional to vd v 1 that is in the desired condition when vd v 1 the voltage becomes zero from equation a and the parameter definitions it can be seen that when vd gt v 1 that is the output voltage from the differential amplifier is positive u03b6 u03c9 n and so the open loop gain are too high and it follows that.