The dependence of the dynamic range of the phase generated carrier (PGC) technique on low-pass filters passbands is investigated using a simulation model. A nonlinear character of this dependence, which could lead to dynamic range limitations or measurement uncertainty, is presented for the first time. A detailed theoretical analysis is provided to verify the simulation results and these results are consistent with performed calculations. The method for the calculation of low-pass filters passbands according to the required dynamic range upper limit is proposed. 1. Introduction Fiber optic interferometric sensors have been intensively developed for the past few decades. Fiber-optic interferometers are used as a sensitive element in fiber optic gyroscopes, hydrophones, and so forth [1]. As a result, many special data acquisition methods, digital signal processing algorithms, and demodulation techniques have been invented to recover measured phase signals. One of the most popular demodulation techniques is phase generated carrier (PGC) demodulation technique [2]. This technique has been used in many applications such as hydroacoustics [3–5], vibration [6], and pipeline leakage detection [7], and its main properties have been thoroughly studied [8–10]. However, implementation methods of demodulation techniques have changed with the advent of high performance field programmable gate arrays (FPGAs). FPGAs allow realizing complex real-time digital signal processing algorithms, and therefore they are ideally suitable for the multichannel PGC technique implementation to demodulate signals from fiber-optic sensor arrays [11]. Unfortunately, the usage of FPGAs for such purposes has got some problems caused by sampling frequency restrictions and finite passbands of digital schemes. This paper is devoted to the detailed analysis of the PGC technique taking into account its practical implementation problems and digital design restrictions. The dependence of the dynamic range of the PGC technique on low-pass filters passbands is investigated for the first time and the nonlinear character of this dependence is shown and explained. 2. Simulation The PGC demodulation scheme is presented in Figure 1 [11]. Its functional model was implemented using MATLAB to investigate dependences of output signals on various parameters. Filter Design and Analysis Tool (FDATool) was used for generating necessary finite impulse response digital filters. Figure 1: PGC demodulation scheme. Several parameters were constants in this model:(i)the duration of simulated signals was 1
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