Ultra-low Frequency Signal Filtering in the Downhole Based on the Matlab Simulation

In order to be convenient for oil exploration, we need to detect the variation of the pressure, flow, temperature in the oil downhole. When the data is detected, it should be transmitted to the relevant device. The fourth generation mobile communication technology-OFDM (Orthogonal Frequency Division Multiplexing, using ulticarrier modulation transmission technology) is applied to transmit data, in order to use of spectrum bandwidth more effectively. It is simulated through mathematical software Matlab that the Ultra-low frequency signal pass through the 8 order Bessel (Bessel1) low-pass filter, cutoff frequency is 10 Hz. The variation of the signal's phase and amplitude is simulated. Using the group delay flat characteristics of Bessel filter, the signal is received synchronously. The signal (the frequency is 2Hz and 9Hz) is simulated and analyzed concretely in different initial phase. At the same time, 50Hz interference and 1 / f noise is filtered out. Finally the feasibility of using 8 order Bessel low pass filter is analyzed.