The invention relates to a circuit for coupling a signal of electromagnetic energy between a first circuit and a second circuit and, more particularly, for simulating the effect of a slow wave device such as a crossed field amplifier upon a signal.
Devices employing slow wave structures are utilized in radar as well as communication systems for amplifying signals, such devices including crossed field amplifiers and traveling wave tubes. Such slow wave devices tend to modify the signal as by introducing a phase shift and amplitude shift as a function of frequency. The foregoing modification of the signal varies with aging of the crossed field amplifiers and traveling wave tubes.
To correct for the foregoing modifications of the signal, it is desirable to have a reference channel wherein a reference signal is made available to the radar signal processing equipment. However, in the past, such reference signals have often been obtained by extracting a sample of the output signal from the slow wave device. However, the effect of aging, associated with decreased electron emission from a cathode of a crossed field amplifier or traveling wave tube goes undetected in the reference signal in the foregoing example wherein the reference signal is obtained at the output port of the slow wave device. When the signal is obtained prior to the input port of the slow wave device, the reference signal does not show any effects of the foregoing modification of the signal. Thus, no data is available as to the effect of aging of the slow wave device, and no corrective action can be taken by a radar signal processor to compensate for the aging effect on the signal produced by the slow wave device.