| Paper: | TH-P1.2 |
| Session: | Radio-Frequency Interference II |
| Time: | Thursday, March 29, 13:40 - 14:00 |
| Presentation: |
Oral
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| Topic: |
RFI and spectrum management: |
| Title: |
Measured performance of improved cross frequency algorithm for detection of RFI from DTV |
| Authors: |
Steen Savstrup Kristensen; Technical University of Denmark | | |
| | Sten Schmidl Søbjærg; Technical University of Denmark | | |
| | Niels Skou; Technical University of Denmark | | |
| | Janne Lahtinen; Harp Technologies Ltd. | | |
| | Josu Uusitalo; Harp Technologies Ltd. | | |
| | Salvatore D'Addio; European Space Agency | | |
| Abstract: |
Ku-band radiometers are widely used by satellites for assessing meteorological parameters such as ocean wind velocities. A major problem with Ku band is that it is not exclusively reserved but shared with broadcasting of Direct Television (DTV) signals from satellites. These signals are reflected by the sea surface and can therefore affect spaceborne radiometers especially near land where the DTV signals are more intense.
To reduce the impact of Radio Frequency Interference (RFI) from this shared use of Ku-band, detection and mitigation of DTV signals are required for future meteorological satellite missions. Current methods applied for detection of RFI comprise:
• Anomalous amplitude,
• Kurtosis
• Cross frequency
Anomalous amplitude method detects RFI producing brightness temperatures at anomalously high level, but not low intensity RFI that may still be detrimental to the meteorological interpretation. Anomalous amplitude method is the first step in RFI detection, but not sufficient. Kurtosis is a statistical method well suited for detecting pulsed RFI like radar signals, but Kurtosis has poor detection capability for continuous signals such as DTV. Cross frequency method divides the spectrum into spectral sub-bands and looks for excessive signal levels within these spectral sub-bands. Cross frequency has proven very useful for detecting narrowband continuous RFI as the division into spectral sub-bands increases the interference to noise ratio (INR). Kurtosis may be combined with cross frequency by applying the Kurtosis method on each spectral sub-band. This improves the detection capabilities of narrowband pulsed RFI. DTV signals are, however, both continuous and of a more broadband nature wherefore new cross frequency methods are needed.
In this work, we have designed an improved cross frequency RFI detection algorithms based on the spectrum of the DTV signals at Ku-band. Simple statistics have been used to predict the performance of these algorithms and the most promising selected. The expected performance of this new algorithm has been verified using extensive Monte Carlo based simulations.
To demonstrate real time online performance a breadboard programmable RFI processor build for demonstrating online detection and mitigation capabilities in spaceborne Ku-band radiometers has been used. The algorithm has been implemented in an FPGA within this RFI processor. The DTU Ku-band radiometer has been used to provide real radiometer input to the breadboard and an arbitrary wave generator (AWG) has been used to insert RFI into this radiometer thus providing a laboratory setup for realistic real time performance measurements. Results from these measurements are presented and compared to both the Monte Carlo based simulations and the simple statistics used for predicting performance during the design.
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