RFI Sources Research Articles

Locating RFI Source by Integrating Ascending and Descending Passes Based on SAR Raw Data

Locating RFI Source by Integrating Ascending and Descending Passes Based on SAR Raw Data

Analysis of efficiency and quality of filters suppressing RFI in radio detection of cosmic rays

Radio stations of the Auger Engineering Radio Array (AERA) investigates radio signals from coherent emissions due to geomagnetic radiation and charge excess processes. The frequency band is limited to 30–80 MHz. In order to improve the signal to noise ratio, RFI filters have to be used to suppress this contamination.The paper compares several (currently in use and proposed) RFI filters. We analyzed: the non-adaptive filter (IIR notch) as well as adaptive filters: IIR notch supported by the virtual NIOS® processor, FIR based on the linear prediction supported by the virtual NIOS® processor and finally the Least Mean Square filter. The LMS filter proposed for the RFI suppression should use correct learning factor, crucial for a stability of the filter, which could be determined by eigenvalues of the auto-correlation matrix built for ADC samples.For typical AERA configuration (4 beacons with fixed frequencies) the best filter seems to be the IIR as introducing very high suppression efficiency with relatively low distortions and low energy consumption. However, when unexpected RFI appears it is worth consider a combination of fixed frequency IIR + IIR filter supported with NIOS processor identifying additional RFI source as well as FIR filters. LMS filters can be used when very fast response on new sources is needed.

Computationally Efficient Radio Frequency Source Localization for Radio Interferometric Arrays

AbstractRadio frequency interference (RFI) is an ever‐increasing problem for remote sensing and radio astronomy, with radio telescope arrays especially vulnerable to RFI. Localizing the RFI source is the first step to dealing with the culprit system. In this paper, a new localization algorithm for interferometric arrays with low array beam sidelobes is presented. The algorithm has been adapted to work both in the near field and far field (only the direction of arrival can be recovered when the source is in the far field). In the near field the computational complexity of the algorithm is linear with search grid size compared to cubic scaling of the state‐of‐the‐art 3‐D MUltiple SIgnal Classification (MUSIC) method. The new method is as accurate as 3‐D MUSIC. The trade‐off is that the proposed algorithm requires a once‐off a priori calculation and storing of weighting matrices. The accuracy of the algorithm is validated using data generated by low‐frequency array while a hexacopter was flying around it and broadcasting a continuous‐wave signal. For the flight, the mean distance between the differential GPS positions and the corresponding estimated positions of the hexacopter is 2 m at a wavelength of 6.7 m.

Adaptive Transient and CW RF Interference Mitigation in HF OTH Radar: Experimental Results

Adaptive Transient and CW RF Interference Mitigation in HF OTH Radar: Experimental Results

RFI Source-Locating on Power Lines-An Update

The author describes a practical and efficient means for locating RI (radio interference) and TVI (television interference) sources on power lines, particularly those operating below 70 kV, where most complaints originate. The main emphasis is on locating sparking sources on overhead lines, but the location of RFI sources occurring in underground lines and the location of nonspeaking power line sources are also treated. Particular attention is given to the use of a vehicular locating set (VLS) and its auxiliary equipment. The VLS, with its oscilloscope presentation, tells the investigator if there is a single source of many sources, and makes it possible to handle these one at a time, and to get within one or two poles of a source. It is also shown that a hot-stick sniffer with a dual VHF/ultrasonic function is effective in rapidly pinpointing RFI sources on low-voltage transmission lines. >

RFI source-locating on power lines-an update

The author describes a practical and efficient means for locating RI (radio interference) and TVI (television interference) sources on power lines, particularly those operating below 70 kV, where most complaints originate. The main emphasis is on locating sparking sources on overhead lines, but the location of RFI sources occurring in underground lines and the location of nonspeaking power line sources are also treated. Particular attention is given to the use of a vehicular locating set (VLS) and its auxiliary equipment. The VLS, with its oscilloscope presentation, tells the investigator if there is a single source of many sources, and makes it possible to handle these one at a time, and to get within one or two poles of a source. It is also shown that a hot-stick sniffer with a dual VHF/ultrasonic function is effective in rapidly pinpointing RFI sources on low-voltage transmission lines.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>