Development Of Full-waveform Recording Technology In High-power Electrical Transmitter

Full-waveform recorder of the voltage and current of MTEM transmitter plays an important role in MTEM prospecting. The recorder is responsible for continuous sampling of the PRBS current which the MTEM transmitter transmitted. The impulse response of the earth is then calculated by convolving the receiver’s data with the recorder’s data. The accuracy of the collected signal amplitude and the collection time is critical for inversion. This thesis works on designing a full-waveform recorder for monitoring high-power electrical transmitter with delta-sigma converter, FPGA and USB microcontroller, along with EDA tools.Full-waveform recorder of the voltage and current of MTEM transmitter consists of conditioning circuit, collecting circuit, control circuit and a clock board. Front-end conditioning circuit is mainly based on the voltage-division circuit and amplifying circuit with high-speed optical coupler, low-power instrumentation amplifier INA128 which conditions low-speed channel, and low-noise wide-band amplifier OPA3690 which conditions high-speed channel. The PCB boards’ layout and routing are optimized several times to keep the noise low. Acquisition circuit uses Δ-Σ ADC ADS1271 and pipelined ADC AD9226 in low speed and high speed data acquisition, respectively. Low-cost low-power cost-effective Cyclone III FPGA is used in the main control circuit, which also has an external SDRAM as a buffer. The main control circuit is driven by a high-precision atomic clock to acquire and transfer data for all channels. According to the function requirements, the program of full-waveform recorder is done in Quartus, Keil, CCS(Code Composer Studio), VS2010(Visual Studio 2010). The program mainly includes four parts: sample and transfer controlling, firmware in USB microcontroller, synchronizing atomic clock with MSP430, and GUI on PC.By testing the sub-modules, the full-waveform Recorder is verified to meet the need of the acquisition accuracy of high-speed and low speed current channels and high-speed and low speed voltage channels. The whole machine is reliable and stable through long-time tests.