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 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 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.

Radio Frequency Interference Characteristics of Plate-Like Soft Magnetic Powders-Polymer Composites

2006 ◽  
Vol 510-511 ◽  
pp. 826-829
Author(s):  
Sang Woo Kim ◽  
Y.W. Yoon ◽  
G.Y. Kim ◽  
Kyung Sub Lee
Keyword(s):  
Radio Frequency ◽  
Polymer Composites ◽  
Electromagnetic Interference ◽  
Noise Suppression ◽  
Compaction Pressure ◽  
Complex Permeability ◽  
Al Alloy ◽  
Radio Frequency Interference ◽  
Soft Magnetic ◽  
Dielectric Resonance

Radio frequency interference characteristics of plate-like Fe-Si-Al alloy powders-polymer composites were investigated for effective noise suppression. Broadband reflection loss characteristics were exhibited in the composites below a critical compaction pressure of 1.56 x 108 N/m2, while narrowband characteristics were shown in the composites above the critical pressure. Although the composites at 2.34 x 108 N/m2 had the highest complex permeability and complex permittivity, the loss properties did not show the broadband characteristics. The peculiar broadband characteristics were obtained in the composites with wideband dependency of the imaginary part of permittivity and permeability. These findings led us to conclude that the broadband electromagnetic interference characteristics of the composites are caused by the coupling effects of magnetic and dielectric resonance 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.

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.

Studies of Radio Frequency Interference at Parkes Observatory

1997 ◽  
Vol 161 ◽  
pp. 661-666
Author(s):  
Peter R. Backus ◽  
Sam LaRoque ◽  
Jill C. Tarter ◽  
John Dreher ◽  
Kent Cullers ◽  
...  
Keyword(s):  
Radio Frequency ◽  
Radio Astronomy ◽  
New South ◽  
Radio Frequency Interference ◽  
Frequency Range ◽  
Data Set ◽  
Unique Data ◽  
South Wales ◽  
Left And Right ◽  
The Mean

AbstractFrom February through early June, 1995, Project Phoenix conducted SETI observations of 209 stars over the frequency range from 1195 to 3005 MHz. A byproduct of this search is a unique data set suitable for studying the Radio Frequency Interference (RFI) environment at the Parkes 64-m telescope in New South Wales, Australia. RFI is an increasing problem for SETI and other radio astronomy observations conducted outside of the «protected» frequency bands. The data analyzed for this paper were «mean baseline» spectra in Left and Right Circular Polarization (LCP, RCP), integrated for either 138 or 276 s, covering a 10 MHz bandwidth with 15,552 channels at a resolution of 643 Hz. Channels were identified as contaminated by RFI when the power in the channel exceeded the mean noise by 3%. The «spectral occupancy», the fraction of time RFI was seen, was determined for each channel. The RFI occupancy for LCP and RCP are distinctly different. Approximately 100 MHz of the spectrum was too heavily contaminated for SETI observations.

scholarly journals RFI Survey for the Giant Metrewave Radio Telescope in India

1991 ◽  
Vol 112 ◽  
pp. 190-193
Author(s):  
G. Swarup ◽  
T.L. Venkatasubramani
Keyword(s):  
Radio Frequency ◽  
Radio Telescope ◽  
Radio Astronomy ◽  
Radio Frequency Interference ◽  
Frequency Range ◽  
Extragalactic Astronomy ◽  
Low Level ◽  
Highly Sensitive ◽  
Set Up

ABSTRACTA Giant Meterwave Radio Telescope (GMRT) is being set up at Khodad about 80 km north of Pune in India for operation in the frequency range of about 30 to 1500 MHz. It is to be completed by 1992 and is being designed to investigate many outstanding problems in the fields of galactic and extragalactic astronomy. We present here measurements of man-made radio frequency interference (RFI) conducted at the GMRT site in 1985 and 1988. It is seen that highly sensitive radio astronomy observations can still be made at selected bands in the above frequency range because of the relatively low level of RFI in India. However, this advantage may not remain for more than a decade or two.

scholarly journals Radio Frequency Interference Survey over the 1.0 - 10.4 GHz Frequency Range at the Goldstone - Venus Tracking Station

1991 ◽  
Vol 112 ◽  
pp. 228-239
Author(s):  
S. Gulkis ◽  
E. T. Olsen ◽  
M. J. Klein ◽  
E. B. Jackson
Keyword(s):  
Radio Frequency ◽  
Surveillance System ◽  
Radio Spectrum ◽  
Radio Frequency Interference ◽  
Frequency Range ◽  
Tracking Station ◽  
Radio Signals ◽  
Extraterrestrial Origin ◽  
Low Sensitivity ◽  
Northern And Southern Hemispheres

Plans are currently being made to carry out a comprehensive, all-sky search for radio signals of extraterrestrial origin. The survey will employ the Goldstone tracking station near Barstow, California, and other sites in the northern and southern hemispheres. The principal parameters of this survey are given in Table 1. In preparation for this search, we have constructed a radio spectrum surveillance system (RSSS), and made a series of measurements of the RFI environment at the Goldstone-Venus tracking station. We describe in this paper the receiving system used (Crow et al. 1985), and the results of a low-sensitivity survey performed during February 16-24,1987.

scholarly journals Teaching Electromagnetic Interference on Microcontrollers through Lab Experiments

2013 ◽  
Vol 3 (2) ◽  
pp. 4
Author(s):  
Chiu Choi
Keyword(s):  
Wireless Communication ◽  
Radio Frequency ◽  
Power Supply ◽  
Electromagnetic Interference ◽  
Communication Technologies ◽  
Radio Frequency Interference ◽  
Current Interest ◽  
Lab Experiments ◽  
External Sources ◽  
Sufficient Magnitude

<p class="Abstract">New lab experiments were developed for the students to investigate the effect of electromagnetic interference on the operation of microcontrollers. The objectives of the experiments include exposing students to the effect of noisy power supply on microcontroller performance and to learn how to use modern instruments for recording the results. In the experiments, the noise is restricted to electromagnetic interference picked up by the power supply conductors from external sources at radio frequencies. As wireless communication technologies have been widely used, such lab investigation is of current interest to the students. There was no simple way to produce the radio frequency interference of sufficient magnitude in our lab. A method was used to emulate the picking up of such interference on the power supply conductors. This paper describes such method. It also describes the new experiments, their benefits for the students, the evaluations, and suggestions for improvements.</p>

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