An Angle Demodulator IC Using Periodically Reset Integration for Path Matched Differential Interferometry-Based Sensors

The angle demodulator (ADM) is a key component for sensors based on angle modulation such as in the path matched differential interferometry (PMDI). Conventional ADMs require tens of operational amplifiers (OPAMPs) and bulky capacitors and resistors, making them difficult to be realized as integrated circuits (ICs). Furthermore, the state-of-the-art ADMs demand precisely controlled modulation indices. Thus, the practical optical modulators in the interferometers cannot but need sophisticated and costly calibrations to precisely control the modulation indices. This paper presents the first ADM IC designed for the PMDI-based sensors. It requires only one OPAMP and thus saves significant area and power, making it best suitable for portable applications. In addition, this novel ADM design tolerates a wide range of the modulation depth of the optical interferometer. As a result, the yield of the PMDI sensor significantly increases and no calibration for an accurate modulation index is necessary. A test chip of the proposed ADM has been designed and successfully verified in 0.18- μ \text{m} CMOS. The active area of the proposed circuits is only 476× 368μ² and it consumes only 6.26 mW.