A new method is proposed for measuring cochannel interference for mobile communication systems. In this method, the carrier envelope is sampled, and the ratio of desired carrier to undesired carrier power is calculated by signal processing. Theoretical and experimental evaluations of measurement errors are examined, and the method is proved to be promising. The circuit for the measurement is designed and programmed using a widely available one-chip microprocessor with an A/D converter. Using this circuit, the ratio of desired to undesired carrier power up to 15 dB is measured within high accuracy.