Accuracy monitoring and enhancement for microwave localization using parallel optical delay detector

The localization of radio devices is of great importance for wireless communication systems. Instead of bulky, lossy delay lines in electrical solutions, parallel optical delay detectors (PODD) based on Mach-Zehnder modulator (MZM) can be used to provide a stable and accurate angle-of-arrival (AOA) measurement, or equivalently a time-difference-of-arrival (TDOA) measurement, of a microwave signal by translating the phase shift information into the change of optical power. Since the response of most MZMs starts from near 0 kHz, such scheme is intrinsically broadband as wide as the bandwidth of the engaged MZM. However, there are several potential factors that can cause measurement errors. To improve the accuracy of AOA measurement, in this paper, we propose a solution to increase the noise tolerance without any additional hardware. We analyze that such solution can be used for both IM-PODD and PM-PODD. Based on the proposed solution, the IM-PODD achieves a greatly reduced normalized measurement error from 2.17% to 0.71%.