Examination of a Simple Pulse Blanking Technique for RFI mitigation
N. Niamsuwan (Ohio State)
J.T. Johnson (Ohio State) johnson.1374@osu.edu
S.W. Ellingson (Virginia Tech) ellingson@vt.edu

Radio frequency interference (RFI) mitigation is very important for spectroscopy at L-band due to the presence of numerous interference sources, including strong pulsed RFI from ground-based aviation radars (GBARs). A simple strategy for reducing pulsed RFI is to remove incoming data whose power exceeds the mean power by a specified number of standard deviations. It may also be advantageous to remove data within a specified time region before and after this ``trigger'' data, to ensure that any pre- and post-``pulse'' information is successfully removed. Such an algorithm has been implemented in a fully-digital radiometer developed at the Ohio State University ElectroScience Laboratory; the process is termed ``asynchronous pulse blanking'' (APB) because no periodic properties of the interference source are assumed.

This paper presents results from a simulation of the APB algorithm on data obtained from the L-Band Interference Surveyor/Analyzer (LISA), an airborne instrument developed for observing the RFI in the region 1200-1800 MHz. The LISA instrument included a digital receiver capable of capturing 20 MHz of incoming data; this 20 MHz channel was tuned through the 1200-1800 MHz band throughout system flights. During Jan--Feb 2003, LISA was depolyed on NASA's P3-B aircraft to observe RFI in flights in the US and Japan. This data set is very useful for assessing the APB algorithm, since many RFI environments were observed that include multiple sources of interference. Several aspects of algorithm performance will be reported in the presentation, including the robustness of the method as the RFI environment is varied. Effects of the blanking process on the final output, which is now partially blanked if any pulse is detected, are also examined. Finally, alternate algorithms for the suppression of continuous wave (CW) interference will be discussed.