A computer program suppresses the effects of narrow-band radio-frequency interference (RFI) on the data collected by a wide-band radar system. The need for this program arises because some advanced wide-band synthetic-aperture radar systems utilize frequency bands that include frequencies used by other radio services. In this program, the RFI environment is represented by an autoregressive process, the frequency band of which is narrow relative to that of the radar. Most of the RFI signals, both narrow-and wide-band, are estimated in one pass of a least-mean-square (LMS) adaptive filter. The program implements three popular LMS algorithms:the time-domain LMS, the frequency-domain LMS, and the filter-bank LMS adaptive-filter algorithms. The program can be run in a manual or automatic mode. In the manual mode, the user selects the filter parameters prior to execution. In the automatic mode, the program utilizes median-filter and spectral-estimation techniques plus the variable-step-size LMS algorithm for automatic determination of filter parameters, and the parameters are adaptively changed as functions of the inputs, resulting in better overall performance.
This program was written by Charles T-C Le, Scott Hensley, and Elaine Chapin of Caltech for NASA's Jet Propulsion Laboratory . For further information, access the Technical Support Package (TSP) free on-line at www.techbriefs.com/tsp under the Software category.
This software is available for commercial licensing. Please contact Don Hart of the California Institute of Technology at (818) 393-3425. Refer to NPO-40255.
This Brief includes a Technical Support Package (TSP).
Software Reduces Radio-Interference Effects in Radar Data
(reference NPO-40255) is currently available for download from the TSP library.
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Overview
The document titled "GeoSAR Radio Frequency Interference Processor Program Design and Algorithm Description Document, And User Manual" provides a comprehensive overview of a software system developed to mitigate the effects of radio frequency interference (RFI) on synthetic aperture radar (SAR) data. Authored by Charles Le and Scott Hensley from the Jet Propulsion Laboratory, the document is part of NASA's Technical Support Package NPO-40255, aimed at disseminating aerospace-related technological advancements.
The introduction outlines the significance of addressing RFI, which can severely degrade SAR image quality by introducing artifacts and masking important features in the imagery, particularly in low signal-to-noise ratio (SNR) regions. The document emphasizes the necessity of suppressing RFI energy while minimizing distortion to ensure high-quality SAR products.
The core of the document is structured into several sections detailing various algorithms designed to combat RFI. Key algorithms discussed include the TDLMS (Time Domain Least Mean Squares), FDLMS (Frequency Domain Least Mean Squares), and FBLMS (Frequency Block Least Mean Squares) algorithms, along with the Variable Step-Size LMS (VSS-LMS) algorithm. Each algorithm is described in terms of its functionality, advantages, and implementation details, providing a clear understanding of how they operate to filter out RFI from radar data.
The document also includes sections on processor and interface overview, code structure and design, and operational setup, which guide users on how to implement and utilize the software effectively. It highlights the design philosophy and basic code structure, ensuring that users can navigate the software with ease.
Additionally, the document contains a conclusion summarizing the importance of the developed software in enhancing the quality of SAR imagery by effectively reducing RFI effects. It underscores the potential applications of this technology in various fields, including environmental monitoring, urban planning, and disaster response.
Overall, this document serves as a technical manual and user guide, providing essential information for researchers and practitioners in the field of radar technology, while also promoting the broader application of NASA's advancements in commercial technology.
