Nonuniform Optical Undersampling for High-Resolution Microwave Frequency Measurements

An optical analog-to-digital converter that uses pulses of multiple wavelengths to nonuniformly sample a microwave signal is used to determine an input microwave frequency to a high accuracy over a large frequency range. Measurement times of 4 μ s lead to frequency errors of ~300 Hz over a measurement range of 10-18 GHz. We also identify the frequency and magnitude of multiple microwave inputs. The simple configuration is robust and practical.