3DEX发射电路解析与三维感应信号源设计

Analysis of 3DEX Transmitting Circuit and Three-dimension Induction Signal Source Design

分析了感应测井仪器3DEX发射电路的组成、工作原理及性能参数,设计了一种新的三维感应信号源方案。采用直接频率合成(DDS)技术和CAN总线通信接口。硬件电路系统由基于DSP的采集控制板和基于DDS的信号发生器板组成,采集控制板通过USB接口接收PC机控制面板传来的指令,通过SPI接口对DDS信号发生器板进行设置,可产生7对合成正弦波形;采集控制板同时能够对输出信号进行取样采集,并将采集到的波形数据通过USB接口传输到PC机控制面板。PC机控制面板通过USB接口对信号源的参数进行设定,并能够显示信号波形、频谱;测量信号幅度、频率、相位、谐波失真等参数。经过分析和实验验证,信号源的性能参数完全可以达到3DEX发射电路的指标要求,在输出信号频率选择性和频率控制灵活性方面优于3DEX发射电路方案。

The compositions, principles of operation and the performance parameters of 3DEX transmitting circuit in three-dimension induction logging tool are analyzed in this paper and a new three-dimension signal source is designed. The signal source is based on direct digital synthesis （DDS） and controller area network （CAN） bus communication port. The design scheme makes the circuit structure and control logic simple significantly. The hardware circuit consists of DSP- based signal pickup device and DDS-based signal generator; The former, through USB port, receives commands from PC control panel; DDS signal generator panel is set through SPI port; Under DSPB control, the circuit generates seven pairs of synthesic sine signal waves. At the same time, the latter picks up output signals as sample, and sends the picked waves data to PC control panel through USB. The PC control plate is compiled with VB6.0. The signal source parameters are set via LISB port for the PC control panel, so, it can display the signal waves and frequencyl and measure the signal amplitude, frequency, phase and harmonic distortion, etc. The experi- ments and test results are in good accordance with the requirements and performance data of 3DEX. The designed signal source is better than 3DEX transmitting circuit scheme in output signal frequency selectivity and frequency control flexibility.