Method and device for excess modulation detection for signal analysis

Abstract

An automated process and device for testing both C.W. and swept output signal modulation of a system or unit under test. The invention conditions the output signals to be compatible for measurement, measures incremental cycle periods of the signals using a continuous time counter, converts raw signal data into formatted tables, calculates prescribed parameters relating to the signals, aligns the calculated prescribed parameters relating to the signals, computes incremental signal frequencies from the incremental cycle periods as measured, substarts the incremental signal frequencies from the predicted signal frequencies to form a frequency residual model, constructs a curve using the incremental signal frequencies, and displays the curve. A prediction model is created and used to predict expected results. The prediction model defines ideal behavior of both C.W. and swept signals from a unit under test. The ideal behavior data is subtracted from the actual data, leaving a coarse representation of non-linearities. A combination of digital filtering, least squares curve fitting and the Choelsky method for solving simultaneous equations is used to refine coarse data into a frequency vs. time continuous curve or for other uses by the unit under test. The invention can be used for integrated circuit testing in manufacturing and incoming inspection of all types of fixed oscillators, all types of voltage controlled oscillators, and amplitude modulation and frequency modulation heterodyning chips, and instrument and module testing for manufacturing, incoming inspection, field test and diagnostics for function generators, sweep generators, oscillators and synthesizers.