Nonlinear Signal Processing for Advanced Digital Receive Systems

GMR Research & Technology (GMR) proposes to develop real-time digital methods to compensate for nonlinear distortions in RF receivers including all components. In particular we will address harmonic distortions caused by amplifiers, mixers, and Analog-to-digital converters (ADCs). In particular we propose to investigate the combined techniques of  digital nonlinear equalization of harmonic distortions (NLEQ) and of digital equalization of interleaved modalities (iNLEQ). These two techniques use similar underlying algorithms and are complementary to each other. In conjunction these techniques have the potential for reducing spurious signals and expanding the bandwidth of receiver systems. In the second phase of the SBIR effort we will develop this approach for a receiver system by collaborating with Hittite Microwave corporation and by using one of their receiver designs. We will design, build, and test a digital receiver which will incorporate our nonlinear signal processing approach on a field programmable gate array (FPGA). We expect this type of receiver to have many benefits for the military by significantly increasing the linear dynamic range of receiver systems such as radars and SIGINT platforms. Moreover we expect this solution to be relatively inexpensive and easy to implement with low size, weight and power consumption. BENEFIT: Assuming a successful completion of the proposed research and development there are several potential beneficial results. Receiver systems in many applications require increasing bandwidth while maintaining or increasing their linear dynamic range. Military systems that may benefit include radar systems for which increased linearity (or reduced) spurs represent the ability to detect and estimate smaller or farther targets while minimizing false alarms. SIGINT systems will be able to detect small signals of interest in a wide spectrum in the presence of strong interfering signals on smaller platforms. Commercial uses for such applications include incorporating such approaches into systems built by large defense manufacturers. For civilian applications the expected benefits of the research and development proposed here will allow receiver systems such as future cellular base stations to operate in increasingly crowded spectrum without having to resort to using ever shrinking cells and over wider bandwidths.