First results of a GNSS-R experiment from a stratospheric balloon over boreal forests

The empirical results of a global navigation satellite systems reflectometry (GNSS-R) experiment onboard the Balloon EXperiments for University Students (BEXUS) 17 stratospheric balloon performed north of Sweden over boreal forests show that the power of the reflected signals is nearly independent of the platform height for a high coherent integration time T-c = 20 ms. This experimental evidence shows a strong coherent component in the forward scattered signal, as compared with the incoherent component, that allows to be tracked. The bistatic coherent reflectivity is also evaluated as a function of the elevation angle, showing a decrease of similar to 6 dB when the elevation angle increases from 35. to 70 degrees. The received power presents a clearly multimodal behavior, which also suggests that the coherent scattering component may be taking place in different forest elements, i.e., soil, canopy, and through multiple reflections canopy-soil and soil-trunk. This experiment has provided the first GNSS-R data set over boreal forests. The evaluation of these results can be useful for the feasibility study of this technique to perform biomass monitoring that is a key factor to analyze the carbon cycle.Peer ReviewedPostprint (author's final draft

Study of RFI signals in protected GNSS bands generated by common electronic devices: effects on GNSS-R measurements

RFI (Radio Frequency Interference) signals are a threat for GNSS-R (Global Navigation Satellite Systems - Reflectometry) due to the very low power of the navigation signals. Interference signals coming from computers or high-speed buses may affect GNSS-R measurements introducing a bias or even corrupting them completely. These RFI may be in-band or near-band and can desensitize GNSS and GNSS-R receivers. A number of techniques are currently under development to mitigate the effect of RFI signals.Peer Reviewe

Study of RFI signals in protected GNSS bands generated by common electronic devices: effects on GNSS-R measurements

RFI (Radio Frequency Interference) signals are a threat for GNSS-R (Global Navigation Satellite Systems - Reflectometry) due to the very low power of the navigation signals. Interference signals coming from computers or high-speed buses may affect GNSS-R measurements introducing a bias or even corrupting them completely. These RFI may be in-band or near-band and can desensitize GNSS and GNSS-R receivers. A number of techniques are currently under development to mitigate the effect of RFI signals.Peer Reviewe

Plasma heating in JET

Preprint of paper at 13. EPS Conf. on Controlled Fusion and Plasma Heating Schliersee (DE)SIGLEAvailable from British Library Document Supply Centre- DSC:4672.262(JET-P--86/21) / BLDSC - British Library Document Supply CentreGBUnited Kingdo

Digital back-end for RFI detection and mitigation in earth observation

A powerful real time Radio-frequency interference (RFI) mitigation back-end system is presented in this work. The interfering signals are estimated by using the wavelet transform to utilize its effective denoising capability. The estimated RFI signals are then subtracted from the total received signal, and ultimately the RFI-mitigated signal is obtained. Here, the hardware implementation and the system tests are demonstrated, showing sinusoid, chirp, and PRN interference mitigation under different Interference to Noise Ratios (INRs).Peer Reviewe

Preliminary performance study of different radio-frequency interference detection and mitigation algorithms in microwave radiometry

This work presents the preliminary performance study of several RFI detection and mitigation algorithms applied to real data. The used algorithms include statistical analysis in the time and frequency domains and time and frequency domains analysis. The data has been acquired in an urban area using a new experimental radiometer called MERITXELL.Peer ReviewedPostprint (published version

Piezoresistance in polycrystalline silicon and its application to pressure sensors

SIGLEAvailable from British Library Document Supply Centre- DSC:D71902/87 / BLDSC - British Library Document Supply CentreGBUnited Kingdo

First results of a GNSS-R experiment from a stratospheric balloon over boreal forests

The empirical results of a global navigation satellite systems reflectometry (GNSS-R) experiment onboard the Balloon EXperiments for University Students (BEXUS) 17 stratospheric balloon performed north of Sweden over boreal forests show that the power of the reflected signals is nearly independent of the platform height for a high coherent integration time T-c = 20 ms. This experimental evidence shows a strong coherent component in the forward scattered signal, as compared with the incoherent component, that allows to be tracked. The bistatic coherent reflectivity is also evaluated as a function of the elevation angle, showing a decrease of similar to 6 dB when the elevation angle increases from 35. to 70 degrees. The received power presents a clearly multimodal behavior, which also suggests that the coherent scattering component may be taking place in different forest elements, i.e., soil, canopy, and through multiple reflections canopy-soil and soil-trunk. This experiment has provided the first GNSS-R data set over boreal forests. The evaluation of these results can be useful for the feasibility study of this technique to perform biomass monitoring that is a key factor to analyze the carbon cycle.Peer Reviewe

Providing temporary support during work on openings in external walls

SIGLEGBUnited Kingdo

Digital back-end for RFI detection and mitigation in microwave radiometers

Radio-frequency interference (RFI) is a serious problem in microwave radiometry. In order to process the received data in real time, a powerful back-end for RFI detection and mitigation system must be implemented. This system includes many techniques against RFI, like time, frequency domain and spectrogram analysis. A wavelet-based RFI-mitigation technique is implemented in hardware. The interfering signal is estimated by using the powerful denoising capabilities of the wavelet transform. Then, this estimate of the RFI signal is subtracted from the total received signal to obtain a RFI-mitigated noise signal. Statistical analysis helps to validate the mentioned methods.Peer Reviewe