scholarly journals Radio-frequency interference mitigating hyperspectral L-band radiometer

2017 ◽  
Vol 6 (1) ◽  
pp. 39-51 ◽  
Author(s):  
Peter Toose ◽  
Alexandre Roy ◽  
Frederick Solheim ◽  
Chris Derksen ◽  
Tom Watts ◽  
...  
Keyword(s):  
Radio Frequency ◽  
Thermal Emission ◽  
Absolute Error ◽  
Radio Frequency Interference ◽  
Frequency Range ◽  
Passive Remote Sensing ◽  
Extended Frequency ◽  
L Band ◽  
Radiometric Signal ◽  
Microwave Radiometers

Abstract. Radio-frequency interference (RFI) can significantly contaminate the measured radiometric signal of current spaceborne L-band passive microwave radiometers. These spaceborne radiometers operate within the protected passive remote sensing and radio-astronomy frequency allocation of 1400–1427 MHz but nonetheless are still subjected to frequent RFI intrusions. We present a unique surface-based and airborne hyperspectral 385 channel, dual polarization, L-band Fourier transform, RFI-detecting radiometer designed with a frequency range from 1400 through  ≈  1550 MHz. The extended frequency range was intended to increase the likelihood of detecting adjacent RFI-free channels to increase the signal, and therefore the thermal resolution, of the radiometer instrument. The external instrument calibration uses three targets (sky, ambient, and warm), and validation from independent stability measurements shows a mean absolute error (MAE) of 1.0 K for ambient and warm targets and 1.5 K for sky. A simple but effective RFI removal method which exploits the large number of frequency channels is also described. This method separates the desired thermal emission from RFI intrusions and was evaluated with synthetic microwave spectra generated using a Monte Carlo approach and validated with surface-based and airborne experimental measurements.

scholarly journals Radio frequency interference mitigating hyperspectral L-band radiometer

2016 ◽  
Author(s):  
Peter Toose ◽  
Alexandre Roy ◽  
Frederick Solheim ◽  
Chris Derksen ◽  
Tom Watts ◽  
...  
Keyword(s):  
Radio Frequency ◽  
Thermal Emission ◽  
Absolute Error ◽  
Radio Frequency Interference ◽  
Frequency Range ◽  
Passive Remote Sensing ◽  
Extended Frequency ◽  
L Band ◽  
Radiometric Signal ◽  
Microwave Radiometers

Abstract. Radio Frequency Interference (RFI) can significantly contaminate the measured radiometric signal of current spaceborne L-band passive microwave radiometers. These spaceborne radiometers operate within the protected passive remote sensing and radio astronomy frequency allocation of 1400–1427 MHz, but despite this are still subjected to frequent RFI intrusions. We present a unique surface-based/airborne hyperspectral 385 channel, dual polarization, L-band Fourier transform, RFI detecting radiometer designed with a frequency range from 1400 through ≈ 1550 MHz. The extended frequency range was intended to increase the likelihood of detecting adjacent RFI-free channels to increase the signal, and therefore increase the thermal resolution, of the radiometer instrument. The external instrument calibration uses three targets (sky, ambient, and warm) and validation from independent stability measurements shows a mean absolute error (MAE) of 1.0 K for ambient and warm targets, while the MAE is 1.5 K for sky. A simple but effective RFI removal method which exploits the large number of frequency channels is also described. This method separates the desired thermal emission from RFI intrusions, and was evaluated with synthetic microwave spectra generated using a Monte Carlo approach and validated with surface-based and airborne experimental measurements.

scholarly journals Surveying RFI for a new Brazilian Solar Spectroscope site

2009 ◽  
Vol 5 (S264) ◽  
pp. 484-486
Author(s):  
José R. Cecatto ◽  
Paulo C. G. Albuquerque ◽  
Ivan O. G. Vila ◽  
Alan B. Cassiano ◽  
César Strauss ◽  
...  
Keyword(s):  
Radio Frequency ◽  
Daily Basis ◽  
High Time ◽  
Radio Frequency Interference ◽  
Frequency Range ◽  
Site Change ◽  
The Moment ◽  
Antenna Location

AbstractBrazilian Solar Spectroscope (BSS) carry out high time (0.01–0.1 s) resolution solar spectral investigations within the frequency range 1–2.5 GHz on a daily basis. At the moment, a new site is imposed to this facility. This site change became necessary due to both factors: the growing level of radio frequency interference (RFI) signals at actual site and requirements of rising up a new building at the BSS antenna location. We present results of RFI signals search at INPE-Cachoeira Paulista area as purpose to define a new BSS site.

Analogue kurtosis detector for radio-frequency interference in microwave radiometers

2008 ◽  
Vol 44 (11) ◽  
pp. 683 ◽  
Author(s):  
P.N. Mohammed ◽  
J.J. Knuble ◽  
J.R. Piepmeier
Keyword(s):  
Radio Frequency ◽  
Radio Frequency Interference ◽  
Microwave Radiometers

Elimination of noise in telemetry systems by pulse-width discriminator

1980 ◽  
Vol 239 (1) ◽  
pp. H133-H136
Author(s):  
A. Livnat ◽  
R. P. Johnson ◽  
J. E. Zehr
Keyword(s):  
Radio Frequency ◽  
Electromagnetic Interference ◽  
Pulse Width ◽  
Pulse Interval ◽  
Telemetry System ◽  
Radio Frequency Interference ◽  
Pressure Measurements ◽  
Frequency Range ◽  
Noise Filter ◽  
Interval Ratio

A pulse-width-discriminator circuit (PWD) was developed and applied for noise reduction in an FM pulse-interval-ratio modulation telemetry system. The PWD was incorporated as an intermediary between the tuner and the demodulator. The application of the circuit as a noise filter is a result of its ability to distinguish between pulses of different durations and its ability to eliminate pulses whose durations are less than some predetermined value. Since spikes of radio-frequency interference (RFI) occurring at the tuner output were of significantly shorter duration than the encoding pulses, they were virtually eliminated by the PWD. This prevented false triggering of the demodulator and resulted in a noise-free final demodulated output signal. This system was tested during telemetered blood pressure measurements in an unrestrained dog and proved to be extremely effective in eliminating spurious noise caused by electromagnetic interference in the radio-frequency range.

scholarly journals A survey of spatially and temporally resolved radio frequency interference in the FM band at the Murchison Radio-astronomy Observatory

2020 ◽  
Vol 37 ◽  
Author(s):  
S. J. Tingay ◽  
M. Sokolowski ◽  
R. Wayth ◽  
D. Ung
Keyword(s):  
Radio Frequency ◽  
Radio Astronomy ◽  
Angular Resolution ◽  
Low Frequency ◽  
Earth Orbit ◽  
Radio Frequency Interference ◽  
Astronomy Observatory ◽  
Frequency Range ◽  
Radio Astronomy Observatory ◽  
Imaging Mode

Abstract We present the first survey of radio frequency interference (RFI) at the future site of the low frequency Square Kilometre Array (SKA), the Murchison Radio-astronomy Observatory (MRO), that both temporally and spatially resolves the RFI. The survey is conducted in a 1 MHz frequency range within the FM band, designed to encompass the closest and strongest FM transmitters to the MRO (located in Geraldton, approximately 300 km distant). Conducted over approximately three days using the second iteration of the Engineering Development Array in an all-sky imaging mode, we find a range of RFI signals. We are able to categorise the signals into: those received directly from the transmitters, from their horizon locations; reflections from aircraft (occupying approximately 13% of the observation duration); reflections from objects in Earth orbit; and reflections from meteor ionisation trails. In total, we analyse 33 994 images at 7.92 s time resolution in both polarisations with angular resolution of approximately 3.5 $^{\circ}$ , detecting approximately forty thousand RFI events. This detailed breakdown of RFI in the MRO environment will enable future detailed analyses of the likely impacts of RFI on key science at low radio frequencies with the SKA.

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