SBIR-STTR Award

This Small Business Innovation Research Phase I project demonstrates an adaptive linearizer (ALIN) that uses a real-time digital signal processing technique to dramatically reduce harmonic and intermodulation distortion by approximately 24 dB over an extremely wide range of input frequencies, signal types, and amplitudes, and in rapidly changing environments (such as wide temperature variations). The technology adaptively tracks nonlinear distortion and subtracts out the errors. ALIN significantly improves the performance of RF amplifiers or the combination of devices in an RF transmit chain (e.g., amplifiers, mixers, digital-to-analog converters). This technology significantly improves the dynamic range, which enables very accurate and efficient synthesis of wideband signals at high intermediate frequencies (IF) or directly at high RF. By compensating for nonlinear compression effects in power amplifiers, the technology improves the amplifier efficiency by operating closer to saturation than with traditional amplifiers. Therefore, lower power, lower mass, lower cost amplifiers can be used in place of inefficient, high-power amplifiers. This pre-distortion waveform shaping significantly reduces out-of-band distortion components, which reduces interference and bandpass filter requirements. The linearizer is based on V Corp’s proprietary phase-shift polynomial model (which has been successfully tested using open-loop calibration methods). The enhancement of using adaptive calibration routines significantly simplifies or even eliminates system calibration. For example, an adaptive routine can be used to monitor the system output and interactively adjust the digital signal processing to minimize the nonlinear distortion without any external calibration signal sources or by interrupting the normal operation of the system. The real-time digital signal processing can be implemented in FPGA hardware, a DSP chip, a custom ASIC, or a software algorithm. The ALIN architecture will always exceed state-of-the-art because it can easily be upgraded as new, more powerful amplifier and converter products become available. V Corp is currently working with Analog Devices, Inc. on developing and packaging various high-performance converter technologies and digital signal processing techniques. During Phase I, V Corp will demonstrate the ALIN technique via testing with a power amplifier module and a digital-to-analog converter. During Phase II, a real-time implementation of the ALIN system will be implemented and integrated in a target system (e.g., advanced digital RF transceivers).

Keywords:
High-Resolution, High-Speed, Linearity Compensation, Amplifier, Intermodulation, Radio Frequency Communications

This Small Business Innovation Research Phase II project demonstrates a combination of two powerful adaptive digital signal processing technologies that enable broadband, high-power amplification with high linear dynamic range and high output efficiency. The technologies are the Adaptive Pre-Distortion Linearizer (ALIN), and the Adaptive Branch Matching (ABM) algorithm. Combined, these two unique technologies will significantly improve the performance of LINC architecture power amplifiers, as well as being directly applicable to a very wide range of other military and commercial RF Power Amplifiers. The Adaptive Pre-Distortion Linearizer (ALIN) uses a real-time digital signal processing technique to reduce harmonic and intermodulation distortion over a wide range of input frequencies, signal types, and amplitudes, and in rapidly changing environments. Pre-distortion is necessary to enable power amplifiers to perform efficiently and is required in the LINC configuration to meet performance requirements. The technology adaptively tracks nonlinear distortion and cancels the errors The Adaptive Branch Matching (ABM) technology accurately matches the gain and phase of the branches in the ExLINC power amp architecture to insure optimal cancellation of the nonlinear distortion components. The ability to maintain gain and phase matching between the branches of LINC power amplifiers is critical and has been a limiting factor in previous LINC systems. This technology overcomes this important limitation which improves stability and performance. Both the ALIN and ABM technologies are blind adaptive algorithms that automatically track parameters that drift without requiring external calibration signals. During Phase II, the ALIN and ABM algorithms will be implemented and tested in real-time FPGA hardware and applied to a number of different amplifier modules, including a broadband Extended-Range Dual-LINC (ExLINC) prototype amplifier system (to be developed in conjunction with OnQ Technologies, Inc. and Omega Wireless, Inc.) with preliminary target goals of compact size (<36 sq. in), broadband (tunable from 500 MHz to 2.5 GHz), and high-output for extended range (100W). Also as a goal, the technologies implemented in the Phase II will be directly applicable to Rockwell Collins Quad LINC architecture to significantly enhance its performance and operating stability. The processing will be demonstrated with this and other amplifier modules in operationally relevant environments in partnerships with industry (such as Analog Devices, Digital Receiver Technologies, and Raytheon -- testimonials attached) to achieve a Technology Readiness Level (TRL) of 7 (via a Phase II Option).

Keywords:
Pre-Distortion Linearization, Power Amplifier, Linc, Branch Matching, Adaptive, Broadband, Digital Signal Processing, Rf Transmitter