The Implementation Of Host Interface In MTEM System

Transient electromagnetic method (TEM) is a significant geophysical exploration method. Comparing with traditional TEM, multi-channel transient electromagnetic method (MTEM) takes advantages of encoding current, multi-channel observation and seismic-like data processing technology and improves the resolution and depth of ex-ploration sharply. Thus, MTEM is one of the hot spots of electromagnetic exploration.In MTEM system, host is the center of both data processing and system manage-ment. On the one hand, multi-channel observation requires massive multi-channel ac-quisition data to return to the host, the host needs to achieve a high data rate other than data reliability. On the other hand, the host should transform the massive time-ordered acquisition data to channel-order for seismic-like data processing. At the same time, the host needs an efficient way to manage multiple sample channels. Traditional host usually uses network card and RUDP/TCP and protocol stack need to process every message so the data rate is subject to message length and CPU performance. In addi-tion, traditional host use software to realize the sort of acquisition data in general and a mass of data analysis and data copy reduce the sort efficiency. Moreover, traditional host connects to multiple sample channels in star-topology and point-to-multipoint sys-tem management method decreases the efficiency.This thesis takes advantages of high speed character of FPGA in data processing and introduces a design of host interface as the bridge between upper application and MTEM system. Host interface consists of host interface unit and host interface software. In the design of host interface unit, it uses FPGA to realize a geophysical exploration specific reliable data transmission protocol based on gigabit Ethernet physical layer. It leaves out the data processing of protocol stack and decreases the number of times of memory copy. On the other side, host interface unit implements hardware sort of acqui-sition data from time-order to channel-order in FPGA with DDR SDRAM. It reduces the workload of software sort and improves the efficiency. In the design of host in-terface software, on account of idea of distributed management, management software makes use of Ethernet physical address and implements a system management API fit for geophysical exploration. It relieves the load of upper application and improves the efficiency.Test shows that the new host with host interface has99.9%Ethernet bandwidth utilization in any message length and CPU utilization is only about25%. Traditional host achieves lower than55%Ethernet bandwidth utilization when short message length (<256bytes) and CPU utilization is higher than50%.