A FPGA-Based Replacement for a Network Analyzer in an Instrumentation-Based 200 GHz Radar

We are entering an exciting time where millimeter-wave (MMW) systems are encroaching into everyday life, examples being communications, auto-navigation, and security. It is instinctive to consider these systems in industrial settings, as well. Given the current energy climate, it may be possible to apply MMW technology in an effort to improve efficiency in power generation industries. Paper is one such industry, specifically in the Kraft-Recovery process. In the Kraft process, pulping salts and organic compounds, byproducts of extracting fiber from wood, are retrieved through combustion. The process of incinerating the solution generates a surplus of heat that is reclaimed in the form of processand power generatingsteam. Heavy sooting of salt in the heat-exchanger is normally experienced and a MMW imaging system was proposed to measure these deposits to aid in the reduction of maintenance steam consumption. Imaging at 200 GHz is attractive due to the electrical properties of the salts as well as the need for millimeter scale resolution; however, wide-band imaging systems operating at these frequencies are generally built from instrumentation and a need for dedicated hardware exists. To this end, we will present a method for constructing a dedicated 200 GHz radar and the requisite signal processing techniques for such an imaging system. Our previous research developed a stepped-frequency continuous-wave (SFCW) 200 GHz, 20 GHz bandwidth, imaging radar capable of measuring soot thickness deposited on boiler tubes (Figure 1). This radar uses a NWA as a sweep source and receiver. A dedicated and lower-cost unit was desired, inspiring the construction of a FPGA-based demonstrator. A favorable comparison of both the NWAand FPGA-based systems will be presented in this article.