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A novel instantaneous frequency measurement system based on a programmable photonic chip frequency discriminator is experimentally demonstrated. The microwave signal whose frequency is to be measured is used to modulate the phase of an optical carrier. An optical ring resonator (ORR) in an add-drop configuration is used as a phase-to-intensity modulation converter. By simultaneously using the through and drop outputs of the ORR, an amplitude comparison function (ACF) can be established. Using this ACF, frequency estimation with a standard deviation of 93.6 MHz in the frequency range of 0.5-4 GHz can be achieved. The ACF is fully programmable by tuning the ORR resonance. This is the first demonstration of an instantaneous frequency measurement system using a compact programmable photonic chip.