# FPGA Implementation of ECT Digital System for Imaging Conductive Materials
## 1 Introduction
Typically, the drawbacks of these systems are big size, high power consumption, high cost, as well as hard adaptation to the new system requirements. However, when a real-time operation is required, dedicated hardware must be designed [1]. Therefore, a parallel VLSI architecture is proposed to reduce the consumed time by the high computation image  
Figure 1: An ECT system for imaging conductive materials. reconstruction algorithm and increase the throughput to more than 500 f/s. The new proposed architecture makes the ECT systems more applicable for high dynamic applications. The reconfigurable computing technology is driven by the Field Programmable Gate Arrays (FPGAs) [15]. Advantages of the FPGAs such as the terrific logic capacity, the intense flexibility of their use, and the extensive spread of hardware languages (VHDL, Verilog) have made the FPGA platforms a perfect candidate for developing reconfigurable computing machines. In many applications, FPGA-based systems have proven substantial performance over general-purpose processors. More advantages such as flexibility of the hardware design, modifying the structure and extending an adjusted performance are gained by the ability of the FPGAs to be reconfigured directly by the software [6]. Replacing DSP processors with FPGA platforms enhances the performance of the ECT system since a decent part of the control/data flow of the image reconstruction algorithm can be implemented on the FPGA. The usage of the FPGA speeds up the reconstruction process by reducing the sequential access of the memory. In [16], an Electrical Impedance Tomography (EIT) system generating 100 f/s and consisting of some impedance measurement FPGA modules is developed. Each FPGA module has its particular current source and voltmeter connected through Intra-network FPGA controller. Applying the FPGA in just the data acquisition process without involving it in the image reconstruction procedure causes the low throughput of the system [17]. Other tomography techniques such as Computed Tomography (CT) [18], Electrical Impedance Tomography (EIT) [16], and Positron Emission Tomography (PET) [19] also implemented their image reconstruction algorithms on the FPGA. Superior performance was achieved in [20] when the algorithm uses the intrinsic fine parallelism ability of the FPGA. In addition, the substantial functioning of Graphics Processing Units (GPU) for arithmetically exhaustive algorithms drives the implementation of the 3D ECT system [21]. However, their performance is lower than the FPGA since it needs a lot of random off-chip memory access. Another real-time system utilizing a Spartan FPGA platform for the PET was discussed in [19]. The proposed image reconstruction algorithm was fully implemented on the FPGA to attain high time resolution. Usually, the evaluation of the FPGA designs is based on three parameters: speed, density, and power. Fixed point designs are fast, consume less power, and need fewer gates compared to its equivalent floating-point designs. However, very large and tiny numbers cannot be realized using fixed point and a bit-width of the number affects its range significantly. Many studies have been carried out on the design of fixed point matrix multiplication on the FPGA. High output architecture using a systolic array for bit level matrix multiplication is proposed in [22] and implemented on Xilinx XCV2000E of Virtex-E FPGA. Another type of implementation based on fully parallel matrix multiplier core was discussed by [23]. The proposed work in this paper integrates the Wireless Sensor Networks (WSN) technology and the reconfigurable FPGA technology as new hardware architecture for the ECT system. The developed system is able to image the metal distribution in the LFC process. The proposed ECT system applying the FPGAs architecture attains faster and more compact realization which boosts the reliability of the overall system. This paper is structured as follows: the details of the ECT system are described in Section 2.