A 1–18-Ghz attenuator calibrator

This single-channel parallel IF substitution system performs attenuator calibrations in a stepped frequency mode to 110 dB through 1–18 GHz, with the accuracy of a fixed frequency system. Measurement time is reduced and operation is simplified by use of two digitally controlled, frequency-locked oscillators as signal source and local oscillator, a 30-MHz precision digital substitution standard and an adaptive bandwidth closed-loop substitution technique. Incident power and source impedance at the insertion point are established by a precision broad-band power splitter and a leveling loop using a barretter as the microwave detector. The load impedance is established by a low mismatch masking attenuator. Measurement sequences can be controlled manually or by a programmable calculator which processes the data. The IF substitution process when under calculator control is terminated when a signal buried in the noise is recovered and the servo-loop is balanced.