Phase dispersion between two or more traveling wave tubes (TWTs) is corrected on a pulse to pulse basis by a feedback loop which compares the relative phase of RF signals to be amplified in traveling wave tubes with one another, and provides a phase correction at the input to at least one of the traveling wave tubes such that the phase difference at the output of traveling wave tubes is the same as the phase difference at the inputs thereto, except for any offset therein which may be purposely inserted as desired. The phase difference at the input and at the output is achieved by phase correlators feeding sample and hold circuits, the outputs of which are converted from rectangular coordinates to polar coordinates including an angle; the phase difference angle at the input being compared with the phase difference angle taken from the output.
An electronic trigger circuit for an RF source, which electronic trigger may be advantageously used in a radar apparatus, for instance. The trigger employs digital logic devices including a register or counter, a circuit for initiating counting in the register in response to a received pretrigger signal and a circuit responsive to the occurrence of selected count in the register for enabling the RF source. A timing signal is generated, based upon the pretrigger signal in timed relationship to the time at which the RF source should nominally generate its RF signal. Typically, the RF source generates its RF signal at sometime after being enabled. A comparator circuit is provided for comparing the phase relationship of the aforementioned timing signal and the occurrence of the RF signal and is in turn coupled to an arithmetic circuit effective for altering the number of states through which the register counts. Preferably, the arithmetic circuit alters the number of states only when the comparison circuit indicates that the phase relationship differs by some preselected period of time. Thus, each time the RF source is fired, its output is compared with the time at which the output should nominally occur and when this difference exceeds a predetermined amount, the amount of delay between the time the pretrigger signal is received and the time the RF source is enabled is varied by changing the number of states through which the aforementioned register counts.
