Impulse Radio Signals Research Articles

Solar flare observations with the Radio Neutrino Observatory Greenland (RNO-G)

The Radio Neutrino Observatory – Greenland (RNO-G) seeks discovery of ultra-high energy neutrinos from the cosmos through their interactions in ice. The science program extends beyond particle astrophysics to include radioglaciology and, as we show herein, solar observations, as well. Currently seven of 35 planned radio-receiver stations (24 antennas/station) are operational. These stations are sensitive to impulsive radio signals with frequencies between 80 and 700 MHz and feature a neutrino trigger threshold for recording data close to the thermal floor. RNO-G can also trigger on elevated signals from the Sun, resulting in nanosecond resolution time-domain flare data; such temporal resolution is significantly shorter than from most dedicated solar observatories. In addition to possible RNO-G solar flare polarization measurements, the Sun also represents an extremely useful above-surface calibration source.Using RNO-G data recorded during the summers of 2022 and 2023, we find signal excesses during solar flares reported by the solar-observing Callisto network and also in coincidence with ∼2/3 of the brightest excesses recorded by the SWAVES satellite. These observed flares are characterized by significant time-domain impulsivity. Using the known position of the Sun, the flare sample is used to calibrate the RNO-G absolute pointing on the radio signal arrival direction to sub-degree resolution. We thus establish the Sun as a regularly observed astronomical calibration source to provide the accurate absolute pointing required for neutrino astronomy.

A Fully Configurable SoC-Based IR-UWB Platform for Data Acquisition and Algorithm Testing

Research and development of algorithms for processing impulse radio ultrawideband signals is a trending issue within remote sensing applications, personal area networks, and RF imaging among other areas. We have designed an SoC-based platform, conceived for scientific experimentation, with a fully modular and configurable design. Built with off-the-shelf components, our design achieves a configurable UWB-capable sampling rate through an equivalent-time sampling scheme. In this letter, we introduce the system architecture, its main interfaces, and the rationale behind each module implementation.

A dispersion excess from pulsar wind nebulae and supernova remnants: Implications for pulsars and FRBs

Young pulsars and the pulsar wind nebulae (PWNe) or supernova remnants (SNRs) that surround them are some of the most dynamic and high-powered environments in our Universe. With the rise of more sensitive observations, the number of pulsar-SNR and PWN associations (hereafter, SNR/PWN) has increased, yet we do not understand to which extent this environment influences the pulsars’ impulsive radio signals. We studied the dispersive contribution of SNRs and PWNe on Galactic pulsars, and considered their relevance to fast radio bursts (FRBs) such as FRB 121102. We investigated the dispersion measure (DM) contribution of SNRs and PWNe by comparing the measured DMs of Galactic pulsars in a SNR/PWN to the DM expected only from the intervening interstellar electrons, using the NE2001 model. We find that a two-σ DM contribution of SNRs and PWNe to the pulsar signal exists, amounting to 21.1 ± 10.6 pc cm−3. The control sample of pulsars unassociated with a SNR/PWN shows no excess. We model the SNR and PWN electron densities for each young pulsar in our sample and show that these indeed predict an excess of this magnitude. By extrapolating to the kind of fast-spinning, high magnetic field, young pulsars that may power FRBs, we show their SNR and PWN are capable of significantly contributing to the observed DM.

Image Reconstruction of Moving Objects Using Multiple IR-UWB Radar Signals

We propose an image reconstruction method to detect moving objects using multiple impulse radio ultra-wideband signals. In contrast with conventional methods, the proposed approach first reconstructs an image of changes of reflected ultra-wideband signals in the 2D domain, and then detects moving objects using the reconstructed 2D image. We believe that the proposed method is useful because not only it is based on effective 2D modeling of moving objects, but also it incorporates a priori information about the moving object images. We verified experimentally that the proposed method provided improved performance compared with the existing methods.

The Case for Global Positioning System Arcing and High Satellite Arc Rates

The Global Positioning System (GPS) satellites arc into the space environment. Evidence for this consists of undispersed impulsive radio frequency signals are shown in the dual-frequency RF receivers, that are on-board all GPS satellites, with high rates that track the charging electron environment, detection of appropriate amplitude short-timescale pulses from GPS satellites at 327 and 430 MHz with the Arecibo 305-m Gordon radiotelescope that do not appear in off-source scans, and arcing on laboratory GPS-like solar arrays at voltages similar to those inferred from GPS arc thresholds. In addition, GPS satellites (up to the Block IIRM) have power degradation (in excess of that expected from radiation) of about 1.5% per year. This degradation is primarily in the short-circuit current, consistent with contamination on the solar array cover glasses, which was detected by a thermal monitor on one GPS satellite solar array, and to be consistent with the power degradation observed on a highly arced GPS-like laboratory solar array if extrapolated to GPS undispersed event rates. The GPS arc rates required for solar array contamination and consistent with the onboard observed event rates are very high, in fact, higher than the rates measured previously on SCATHA, CTS, and other satellites. It is conjectured that the effects of these arcs on satellite power systems have been routinely prevented by highly filtering the power system and antenna response, that most satellites have had no way to detect arcing, and that most power losses up to the present time have been ascribed to radiation damage. Results of new optical and radio-frequency radio frequency observations of satellite arcing are discussed, as well as laboratory measurements confirming the high arc rates and their consequences.

Design and performance of an interferometric trigger array for radio detection of high-energy neutrinos

Ultra-high energy neutrinos are detectable through impulsive radio signals generated through interactions in dense media, such as ice. Subsurface in-ice radio arrays are a promising way to advance the observation and measurement of astrophysical high-energy neutrinos with energies above those discovered by the IceCube detector ($\geq$1 PeV) as well as cosmogenic neutrinos created in the GZK process ($\geq$100 PeV). Here we describe the $\textit{NuPhase}$ detector, which is a compact receiving array of low-gain antennas deployed 185 m deep in glacial ice near the South Pole. Signals from the antennas are digitized and coherently summed into multiple beams to form a low-threshold interferometric phased array trigger for radio impulses. The NuPhase detector was installed at an Askaryan Radio Array (ARA) station during the 2017/18 Austral summer season. $\textit{In situ}$ measurements with an impulsive, point-source calibration instrument show a 50% trigger efficiency on impulses with voltage signal-to-noise ratios (SNR) of $\le$2.0, a factor of $\sim$1.8 improvement in SNR over the standard ARA combinatoric trigger. Hardware-level simulations, validated with $\textit{in situ}$ measurements, predict a trigger threshold of an SNR as low as 1.6 for neutrino interactions that are in the far field of the array. With the already-achieved NuPhase trigger performance included in ARASim, a detector simulation for the ARA experiment, we find the trigger-level effective detector volume is increased by a factor of 1.8 at neutrino energies between 10 and 100 PeV compared to the currently used ARA combinatoric trigger. We also discuss an achievable near term path toward lowering the trigger threshold further to an SNR of 1.0, which would increase the effective single-station volume by more than a factor of 3 in the same range of neutrino energies.

Photonic generation and transmission of on–off keying ultra-wideband impulse radio signals over a fiber link utilizing a delay interferometer and a semiconductor optical amplifier

Photonic generation and transmission of on–off keying ultra-wideband impulse radio signals over a fiber link utilizing a delay interferometer and a semiconductor optical amplifier

An Efficient Method of Power Spectral Density Estimation for On-Chip IR-UWB Transmitter Self-Calibration

In ultra-wideband impulse radio communications, process, voltage, and temperature variations may impact the operation of emitters by modifying the emitted power spectral density. In order to compensate the impact of such variations and to respect the spectral emission masks, self-calibration systems able to estimate the output power spectral density have to be integrated in ultra-wideband impulse radio transmitters. In this paper, a new power spectral density estimation method for ultra-wideband impulse radio signals is presented. Unlike the discrete Fourier transform classically used to estimate the power spectral density, the proposed method, which is based on the measurement of the time varying envelope and instantaneous frequency of the emitted pulse, preserves a link between the time and the frequency domain thanks to a piece-wise approximation of these waveforms. This time-to-frequency link enables a straightforward pulse shape control by using simple control methods and allows to comply with spectral masks required by ultra-wideband communication regulations and standards such as the IEEE 802.15.4a. Thus, both envelope and instantaneous frequency extraction techniques are introduced for acquisition of these time domain waveforms in ultra-wideband impulse radio domain. The proposed techniques are validated and allow to consider future hardware implementation in order to build on-chip calibration systems for ultra-wideband transmitters.

Frequency Extended-MUSIC Method for DOA Estimation in Indoor IR-UWB Environment

In recent years, many researchers have been developed in order to ensure an accurate localization. So many techniques have been used the direction of arrival to estimate and track of IR-UWB signals. In this study, we propose a new direction of arrival estimation method for impulse radio UWB signals. This technique based on Extended-Music algorithm. The proposed method has high performances in the multipath channels. Simulation results show that it has more accuracy then others high resolution algorithms, moreover, It is compared the performance corresponding to the Cramer-Rae bound (CRB).

THE SELF-ORGANIZING RADIO NETWORKS AND ULTRA WIDE BAND SIGNALS

The paper proposes to use impulse radio ultra wide band signals in self-organizing ad hoc and MANET networks to solve multiple access and widen networks coverage area problems. New methods of signals reception and information capacity increasing are proposed.

A Cross-Layer Optimization Approach for Lower Layers of the Protocol Stack in Sensor Networks

A cross-layer optimization approach for the physical and medium access control layers of wireless sensor networks is introduced in this article. This approach includes a Markov chain model, simulations, and analytical derivations that are applied to the analysis of sensor networks using impulse radio ultra-wideband signals with noncoherent energy detection. This type of communication system has low-power transmission requirements and noise like signal characteristics with low interference to other wireless systems. The energy efficiency of different Reed-Solomon code rates and uncoded case are studied in a star topology network, where slotted Aloha, as defined in the IEEE 802.15.4a standard, is used as the medium access protocol. Analytical and simulation results clearly show the potential energy gains that can be achieved with the proposed optimization approach that can be also used in the evaluation and optimization of other combinations of physical and medium access control protocols.

Analysis of energy detection receiver for TOA estimation in IR UWB ranging and a novel TOA estimation approach

Ultra wideband (UWB) localization has attracted a lot of attention, as it offers the capability of penetration and high precision positioning with low cost. Time-based UWB ranging can take full advantage of the characteristics of impulse radio (IR) signal. The energy detection (ED) receiver instead of the matched filter is used a lot in the area for its low complexity. In the ED receiver, many factors, such as the integration interval, signal waveform, the upper or lower limit of integration, noise floor and pulse width, affect the ranging performance. These factors have not been studied thoroughly on energy collection in ED-based receivers, while energy collection is very important for IR UWB ranging and localization. Many studies focus on how to estimate the time of arrival (TOA) based on the output of the ED receiver. In the study, we will examine the effects of these factors on energy collection and TOA estimation. Some qualitative conclusions are given. We propose an approach to solve some problems caused by these factors and further improve the ranging accuracy. The approach can break through the performance limitation of TOA estimation with the ED receiver to some extent with some low-cost delayers instead of the high sampling rate analog to digital converters. Simulation results prove that the approach works effectively compared with traditional methods under different channels.

Chipless RFID Tag Localization

A novel localization technique for frequency-domain chipless RF identification (RFID) tag is proposed. A short-duration ultra-wideband impulse radio signal interrogates the tags, and multiple receivers in the interrogation zone capture the backscattered signal from the tags. The received signals from the chipless tags are analyzed for the structural mode radar cross section to determine the relative ranges. Using the range information, the linear least square (LLS) method is employed for accurate localization of tagged items. The accuracy of the localization method is analyzed by moving the chipless tag within a fixed interrogation zone. The whole system is modeled in CST Microwave Studio Suite 2012 to comply with a realistic scenario. The post-processing for range and tag position estimation through LLS is done in MATLAB. The method is also verified in laboratory environment with fabricated chipless RFID tags and multiple receiving units. The range and angular resolution are 2.1 cm and 3.5 °, respectively. The analysis and results create a strong foundation for chipless RFID tags to be used in tracking and localization.

A 60 GHz transceiver for low power ad hoc networks

ABSTRACTThis article presents a low‐power consumption architecture of RF transceiver using impulse radio signals operating at 60 GHz. Both intrinsic features and related technologies of this operating frequency are detailed and the specific topology of this communication and geolocalization system is introduced. The performance of this low‐power consumption system is validated experimentally. The emitter exhibits an energy efficiency down to 10 pJ/bit and data rates up to 10 Mbps. Geolocalization ability of this 60 GHz system is also experimentally demonstrated with localization accuracy in the range of 40 cm. © 2013 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:2640–2643, 2013

Performance of the IEEE 802.15.4a UWB System using Two Pulse Shaping Techniques in Presence of Single and Double Narrowband Interferences

In Cognitive radio (CR) applicationsUltra-wideband (UWB) impulse radio (IR)signals can be designed such as they can co-exist with licensed primary users. Thepulse shape should be adjusted such that the power spectral characteristics not only meet the Federal Communications Commission (FCC) constrains, but also mitigate multiple narrow -band interference at the locations of existing primary users. In this paper, the Parks-McClellan (PM) Algorithm and the Eigen Value Decomposition (EVD) approach for UWB impulse radio waveform shaping areconsidered. The power spectral density (PSD) and the bit -errorrate (BER) performance of the two methods are compared in the presence of single and double narrowband interference (NBI). The interference rejection capabilities of the two methods are evalua ted and compared for different interference and additive noise levels. In particular, the simulations considerthe coexistence of practical IEEE 802.15.4a UWB systems with both IEEE 802.11 wireless LAN systems operating at 5.2 GHz and radio location servic es operating at 8.5 GHz.

Photonic generation multiband UWB impulse radio signal

A novel method to photonic generation multiband ultra-wide band (MB-UWB) impulse radio signal based on the summation of multiple doublet pulses with different weights and proper time delays is proposed. Microwave sinusoidal signal is used to amplitude modulate a tunable laser to get multi-wavelength source. The optical signal is then phase modulation with Gaussian pulse and fed into a section of single-mode fiber (SMF). The SMF services as phase modulation to intensity modulation (PM-IM) conversion to generate Gaussian doublet pulse, and offers proper time delays to Gaussian doublet pulses with different weights. MB-UWB pulses with sidelobe suppression levels over 25 dB, central frequency from 5 to 8 GHz, 10 dB bandwidth from 2.9 to 3.8 GHz are obtained in experiment.

Indoor Positioning Using UWB-IR Signals in the Presence of Dense Multipath with Path Overlapping

This paper presents a method for positioning using ultra-wideband impulse radio (UWB-IR) signals that is robust in indoor environments characterized by dense multipath channel with path overlapping. Path overlapping effects arising from multipath in dense cluttered environments decrease the direct path resolution in time domain, and hence induce time-of-arrival (TOA) and angle-of-arrival (AOA) based positioning inaccuracy. To mitigate this problem, system design that is capable of resolving the closely-spaced multipath at low cost is of value. Our method yields the least-squares estimation of joint TOA and AOA with low computational cost. It is based on the spectral observation of beam forming, in which the path overlapping effect is mitigated using multipath-aided acquisition. The computational cost is reduced using in-band power spectrum and accurate initial estimations. The performance is verified both in IEEE 802.15.4a CM3 channel model and in a real environment. Simulation results in CM3 channel model show that the TOA and AOA estimation improvements on average are 2.4cm and 13.1° in the dense multipath scenario. Measurement in an indoor open hall environment shows that the AOA error decreases from 10.6° to 7.2°, and the TOA error decreases from 2.1cm to 1.9cm when the path overlapping effects are mitigated in the range of 21m.

Reconfigurable ultra-wideband transmitter for generation of arbitrary impulse shapes and modulation schemes

Abstract. In this paper a reconfigurable ultra-wideband (UWB) impulse radio (IR) transmitter is presented. The IR signal is synthesized at an intermediate frequency (IF) by employing a multi-Nyquist digital-to-analog converter (DAC) with 12 bit resolution and an update rate of 2.3 GHz. Digital generation of signals in a field programmable gate array (FPGA) guarantees very high flexibility of the reconfigurable design. For upconversion to the radio frequency (RF) band, a first order bandpass (BP) sampling concept and an alternative conventional concept with mixer stages, have been realized. The system enables to generate signals with arbitrary modulation schemes and techniques at an external host personal computer (PC) employing MATLAB. Different measurements using a digitizing oscilloscope have been conducted to demonstrate the performance of the transmitter.

A 3.1–4.8-GHz IR-UWB All-Digital Pulse Generator With Variable Channel Selection in 0.13-$\mu\hbox{m}$ CMOS Technology

An all-digital pulse generator in a standard 0.13- CMOS technology for communication systems using an impulse radio ultrawideband signal is presented. A delay-line-based architecture utilizing only static logic gates for pulse generation with low-power characteristic is proposed in this brief. The center frequency and the fixed bandwidth of 500 MHz of the output signal can be digitally controlled to cover three channels in the low band of UWB spectrum. Delay-based binary phase shift keying and pulse position modulation schemes are exploited at the same time to modulate transmitted signals with further improvement in spectrum characteristics. The total energy consumption is 48 pJ/pulse at 1.2-V supply voltage without static bias currents.

A High-Resolution UWB IR Superregenerative Receiver Front End With an SRD Quench Shaper

We present a simple receiver front end that makes use of the baseband superregeneration principle to detect ultrawideband (UWB) impulse radio signals. The UWB antenna is directly connected to the core circuit consisting of a resistor-capacitor (RC) network coupled to a negative resistance that varies under the control of an external quench generator. Due to a step-recovery-diode quench shaper, 50-ps time-domain sensitivity windows are generated that filter the received pulses and reject noise and interference. The circuit achieves high gain, exhibits automatic gain control, and directly demodulates binary phase modulations.