Radio Power Research Articles

Stochastic Fading Channel Models With Multiple Dominant Specular Components

We introduce a comprehensive statistical characterization of the multipath wireless channel built as a superposition of scattered waves with random phases. We consider an arbitrary number <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$N$</tex-math></inline-formula> of specular (dominant) components plus an undetermined number of other weak diffusely propagating waves. Our approach covers the cases in which the specular components have constant amplitudes, as well as when these components experience random fluctuations. We show that this class of fading models can be expressed in terms of a continuous mixture of an underlying Rician (or Rician shadowed) fading model, averaged over the phase distributions of the specular waves. The proposed model parameters can be adjusted to tailor the statistical distribution of the received radio signal power to a wide variety of wireless scenarios, some of which are not covered by other state-of-the-art stochastic wireless channel models. In this regard, we verify that the proposed models accurately fit experimental measurements for which their multi-modality cannot be properly captured by other current stochastic models. It is shown that the fluctuations of the specular components have a detrimental impact on performance, and it is formally demonstrated that the lower error rate is obtained when the signal power is concentrated on a single specular component, regardless of whether it fluctuates or not.

Complexity Optimized Digital Predistortion Model of RF Power Amplifiers

A novel behavioral modeling technique for digital predistortion of radio frequency power amplifiers (PAs) is proposed. The proposed basis-propagating selection (BAPS) model has an advantage on complexity since its basis functions are constructed as delay or a combination of existing basis functions. The BAPS model effectively optimizes the running time complexity while maintaining the generality of a full Volterra series. A greedy search procedure is applied to select the optimal basis functions. Compared with truncated Volterra models and pruned models obtained by popular pruning techniques, the superior performance of the BAPS model, in terms of accuracy and identification stability, has been fairly justified. The linearization measurements on different types of PAs illustrate that the BAPS model can robustly outperform other models from literature while achieving a low running complexity.

Reducing Power Consumption of Digital Predistortion for RF Power Amplifiers Using Real-Time Model Switching

In this article, we propose a new behavioral modeling method to reduce the running complexity and power consumption of digital predistortion (DPD) models for radio frequency power amplifiers. By employing the proposed method, different cross terms in a DPD model can be switched dynamically in real time. Each cross-term branch can further choose the model coefficients from multiple coefficient sets, which improves the DPD performance with little extra complexity. The switch of both cross-term branches and model coefficients is realized using a decision tree-based switch controller, leading to very low run-time complexity. By optimizing the selection process, different input samples can choose the most suitable model configuration that contributes most to the linearization performance. As only one branch is activated at a time, the power consumption can be greatly reduced. Based on the experimental results, the proposed method can achieve excellent linearization performance with significantly reduced power consumption.

Research on robot wireless charging system based on constant-voltage and constant-current mode switching

The traditional wired charging of robot has the disadvantages of inconvenient charging and manual operation for electrical connection. With the continuous development of radio power transmission, the disadvantages of wired charging are overcome, and the charging process does not need manual intervention. At present, a single compensation network is often used to charge the robot wirelessly, but the single compensation network only has constant current or constant voltage output capability. When the constant voltage or constant current mode is switched in the charging process, additional DC–DC​ circuit is needed for control, which increases the difficulty of system design and system volume, and the control is also more complex. In this paper, based on the robot wireless charging system, a coupling mechanism which can switch topology is designed. The LCC-S/ LCC compensation network is used. In the charging process, the constant current and constant voltage charging mode is switched by switching the compensation network at the receiving end, which simplifies the design difficulty, volume and control method of the system. Finally, an experimental platform is built, and the experimental results verify the feasibility of the proposed topology and control method.

Ferroelectric domain induced giant enhancement of two-dimensional electron gas density in ultrathin-barrier AlGaN/GaN heterostructures

With high carrier mobility two-dimensional electron gas (2DEG), AlGaN/GaN heterostructures are widely used in radio frequency and power devices. While due to limited spontaneous and piezoelectric polarization in AlGaN/GaN heterostructures, their practical 2DEG density is around 1013 cm−2 so far. Further enhancement of the 2DEG density is always an attractive topic with both fundamental and application importance. Theoretical studies have shown that the carrier density in the AlGaN/GaN interface can be greatly enhanced by a ferroelectric layer with large polarization. Some experimental results have already been reported, showing signatures of correlation between ferroelectric polarization and 2DEG density. However, they can only realize limited enhancement of 2DEG in AlGaN/GaN heterostructures. Recently, with a simple substrate transfer technique, the hetero-integration of high-quality PbZrxTi1-xO3 (PZT) on the AlGaN/GaN was successfully fabricated by our group. A threshold voltage shifts up to 4 V was achieved by the ferroelectric polarization. Herein, we report further optimization of this structure with ultrathin-barrier layer and in-situ poled ferroelectric domain, where the 2DEG density was non-volatilely enhanced three orders of magnitude up to 2.57 × 1014 cm−2. This result provides good experimental support to the theoretical prediction and might help to further improve the performance GaN based electronic devices.

Location-Based LTE-M Uplink Power Control and Radio Resource Scheduling.

Long-Term Evolution for Metro (LTE-M) is adopted as the data communication system in urban rail transit to exchange bio-direction train-wayside information. Reliable data communication is essential in LTE-M systems for ensuring trains’ operation safety and efficiency. However, the inter-cell inference problem exists in LTE results in throughput reduction, especially when trains are in the edge area of adjacent cells, and has negative effects on train operation. The uplink power control and radio resource scheduling scheme is studied in LTE-M system which differentiates from public cellular networks in user numbers and the availability of the trains’ locations. Since the locations of the trains are available, the interferences from the neighbouring cells can be calculated, and a location based algorithm together with soft frequency reuse is designed. In addition, a proportional fair algorithm is taken to improve uplink radio resource scheduling considering the fairness to different train-wayside communication service requirements. Through simulation, the practicability of the proposed schemes in communication system of urban rail transit is verified in aspects of radio power control and data communication throughput.

The Innovative Development Path of Financial Media Based on Mobile Edge Computing Technology from the Perspective of Rural Revitalization

Rural Revitalization is a systematic and complex strategic project that must keep up with the times while also taking into account the times’ characteristics and social development. The media should be at the forefront of rural revitalization efforts. The interaction of various “forces” is required for the successful implementation of the rural revitalization strategy. The county-level financial media center, as a “force of the media,” will encourage mainstream media to overcome their own development challenges, become an important mainstream public opinion publicity platform, and aid in the realization of the great cause of rural revitalization. For rural comprehensive revitalization, big data provides new means and tools. It is not only a powerful support for rural comprehensive revitalization, but also an important means of realizing the integrated development of the digital economy and rural revitalization, as well as improving the quality and level of rural revitalization. We need to accelerate the realization of agricultural and rural modernization to implement the rural revitalization strategy, and the construction of smart countryside is an important embodiment of agricultural and rural modernization. Mobile edge computing technology has become ingrained in many aspects of social production and daily life. With the power of MEC, urban radio and television must accelerate the pace of multiscreen and multifrequency interaction, as well as online and offline integration; create an all-media instant communication and interactive platform; make new media products suitable for rural audiences; realize integrated development of urban and rural areas; and improve the influence and credibility of new media on agricultural communication. From the perspective of rural revitalization, this paper will investigate the development path of financial media under the influence of data mining (DM) and mobile edge computing technology.

Estimated approach development and experimental validation of residual stress-induced warpage under the SiNx PECVD coating process

Depositing silicon nitride (SiNx) coating by utilizing the plasma-enhanced chemical vapor deposition (PECVD) procedure is currently an important approach in the semiconductor industry because SiNx coating has several excellent application functions, such as passivation layer and oxygen/vapor barrier. However, residual stress occurs in the thin film resulted from the coefficient of thermal expansion (CTE) mismatch, lattice mismatch, defects, and impurities during the PECVD process. The SiNx-coated wafer would induce harsh warpage generated by coating film's residual stress. Aforementioned issue might generate the defects in the products, thus resulting in disrupted process and reliability problems. Such warpage is also unfavorable to the high flatness requirement for subsequent fabrication with the continuous scaling of advanced-technology devices. Accordingly, this study presents a novel process-oriented simulation methodology integrated with fluid dynamics-mechanical coupling responses to estimate its induced warpage magnitude affected by the pressure and temperature distributions during PECVD process and the initial intrinsic stress of SiNx coating. Under the consideration of the abovementioned loadings, the resultant stress and warpage after force balance for depositing SiNx coatings are obtained through process-oriented layer-by-layer simulation. On the basis of the simulated results and the data of experimental measurements, an intrinsic stress surface for SiNx is established by the radio frequency power, ammonia, and silane gas flow rate. Accordingly, the warpage magnitude and intrinsic stress of PECVD SiNx thin coating prior to actual processing can be immediately and accurately judged by the simulation methodology and SiNx intrinsic stress surface presented in this investigation.

Spectral study of the diffuse synchrotron source in the galaxy cluster Abell 523

ABSTRACTThe galaxy cluster Abell 523 (A523) hosts an extended diffuse synchrotron source historically classified as a radio halo. Its radio power at 1.4 GHz makes it one of the most significant outliers in the scaling relations between observables derived from multiwavelength observations of galaxy clusters: it has a morphology that is different and offset from the thermal gas, and it has polarized emission at 1.4 GHz typically difficult to observe for this class of sources. A magnetic field fluctuating on large spatial scales (∼1 Mpc) can explain these peculiarities but the formation mechanism for this source is not yet completely clear. To investigate its formation mechanism, we present new observations obtained with the LOw Frequency ARray at 120–168 MHz and the Jansky Very Large Array at 1–2 GHz, which allow us to study the spectral index distribution of this source. According to our data the source is observed to be more extended at 144 MHz than previously inferred at 1.4 GHz, with a total size of about 1.8 Mpc and a flux density $S_{\rm 144\, MHz}=(1.52\pm 0.31)$ Jy. The spectral index distribution of the source is patchy with an average spectral index α ∼ 1.2 between 144 MHz and 1.410 GHz, while an integrated spectral index $\alpha \, \sim \, 2.1$ has been obtained between 1.410 and 1.782 GHz. A previously unseen patch of steep spectrum emission is clearly detected at 144 MHz in the south of the cluster. Overall, our findings suggest that we are observing an overlapping of different structures, powered by the turbulence associated with the primary and a possible secondary merger.

Power amplifier behavioral modeling based on LaguerrePolar‐Volterraseries with independent truncations

This article proposes an approach that modifies the Polar-Volterra series expanded by a set of Laguerre Orthonormal Basis Functions and the Polar-Volterra series using independent truncation techniques to significantly reduce the amount of parameters, where the resulting models reproduce the distortions of the nonlinearities of a radio frequency power amplifier (RF PA). An RF PA GaN HEMT class AB, stimulated by a wave centered at 900 MHz modulated by two 3GPP WCDMA envelope signals, each having a bandwidth of 3.84 MHz and shifted by 5 MHz, was used. A comparison of several models showed that the two proposed models, both containing a larger number of independent truncation factors, can provide a reduction over 50% in the number of generated coefficients, reaching a maximum of 84%. In another comparison with the other models, the modified Polar-Volterra series expanded by a set of Laguerre functions significantly improved the modeling accuracy, quantified by improvements of normalized mean square error of up to 6.51 dB.

A new configuration for high power propulsion plasmas driven by ion cyclotron resonance energization

The ion cyclotron resonance mechanism can play a crucial role in high-power electric propulsion of space vehicles. Compared with the existing high-power thruster design such as the single-pass configuration in Variable Specific Impulse Magnetoplasma Rocket, we propose a new ion cyclotron resonance configuration that is still efficient under high radio frequency power. A single-ion acceleration theory and particle-in-cell simulations reveal the mechanism of the new configuration by making the phases of the ion and the wave match to each other for more energy gain in the ion cyclotron resonance and a raise of the energy conversion efficiency. Thus, this new configuration can have important applications not only to electric propulsion but also to ion cyclotron resonance heating in nuclear fusion.

The far-infrared/radio correlation for a sample of strongly lensed dusty star-forming galaxies detected by Herschel

Abstract We investigate the radio-far infrared (FIR) correlation for a sample of 28 bright high-redshift (1 ≲ z ≲ 4) star-forming galaxies selected in the FIR from the Herschel-ATLAS fields as candidates to be strongly gravitationally lensed. The radio information comes either from high sensitivity dedicated ATCA observations at 2.1 GHz or from cross-matches with the FIRST survey at 1.4 GHz. By taking advantage of source brightness possibly enhanced by lensing magnification, we identify a weak evolution with redshift out to z ≲ 4 of the FIR-to-radio luminosity ratio qFIR. We also find that the qFIR parameter as a function of the radio power $L_{1.4\, \rm GHz}$ displays a clear decreasing trend, similarly to what is observed for optically/radio selected lensed quasars found in literature, yet covering a complementary region in the $q_{\rm FIR}-L_{1.4\, \rm GHz}$ diagram. We interpret such a behavior in the framework of an in-situ galaxy formation scenario, as a result of the transition from an early dust-obscured star-forming phase (mainly pinpointed by our FIR selection) to a late radio-loud quasar phase (preferentially sampled by the optical/radio selection).

Very Large Array Radio Study of a Sample of Nearby X-Ray and Optically Bright Early-type Galaxies

Abstract Many massive early-type galaxies host central radio sources and hot X-ray atmospheres indicating the presence of radio-mechanical active galactic nucleus (AGN) feedback. The duty cycle and detailed physics of the radio-mode AGN feedback is still a matter of debate. To address these questions, we present 1–2 GHz Karl G. Jansky Very Large Array radio observations of a sample of the 42 nearest optically and X-ray brightest early-type galaxies. We detect radio emission in 41/42 galaxies. However, the galaxy without a radio source, NGC 499, has recently been detected at lower frequencies by the Low-Frequency Array. Furthermore, 27/42 galaxies in our sample host extended radio structures and 34/42 sources show environmental interactions in the form of X-ray cavities. We find a significant correlation between the radio flux density and the largest linear size of the radio emission and between the radio power and the luminosity of the central X-ray point source. The central radio spectral indices of the galaxies span a wide range of values, with the majority of the systems having steep spectra and the rest flat spectra. These results are consistent with AGN activity, where the central radio sources are mostly switched on, thus the duty cycle is very high. Seven out of 14 galaxies with pointlike radio emission (Fanaroff–Riley Class 0; FR 0) also show X-ray cavities indicating that, despite the lack of extended radio structures at 1–2 GHz, these AGNs do launch jets capable of inflating lobes and cavities.

Improvement of energy efficiency by dynamic load consolidation in C‐RAN

SummaryThe Fifth Generation (5G) network is the next step in the evolution of cellular networks, which are anticipated to encounter a remarkable growth in traffic. To meet this traffic requirement, the network capacity must be increased, which would inevitably necessitate the expansion of additional base stations (BSs). Moreover, the expenses and energy consumption of BSs are excessively high. The highly complex signal processing in baseband units contributes to a substantial amount of energy consumption. Consequently, cloud radio access network (C‐RAN) has been demonstrated as an effective approach to overcoming 5G wireless challenges through an energy‐efficient means. C‐RAN architecture has a baseband unit (BBU) pool that consists of the number of BBUs and remote sites, which are called remote radio heads (RRHs). As a sharing of ancillary subsystems into one location, BBU pooling has a significant impact on reducing power consumption. However, C‐RAN necessitates a novel paradigm of energy consumption for resource optimization. In this article, a C‐RAN with a dynamic load consolidation algorithm depending on traffic condition is presented to jointly take the power consumption and energy efficiency targeting to decrease power consumption and increase energy efficiency. To capture the energy consumption of C‐RAN, a new energy consumption scheme considering the BBU cloud, optical link, and radio side power has been proposed that optimizes the BBU resources. Numerical results come about based on simulation settings illustrate that the presented model accomplishes an improved energy‐efficient performance with respect to the referred baseline RAN system scheme.

An Empirical Study on Using CNNs for Fast Radio Signal Prediction

Accurate radio frequency power prediction in a geographic region is a computationally expensive part of finding the optimal transmitter location using a ray tracing software. We empirically analyze the viability of deep learning models to speed up this process. Specifically, deep learning methods including CNNs and UNET are typically used for segmentation, and can also be employed in power prediction tasks. We consider a dataset that consists of radio frequency power values for five different regions with four different frame dimensions. We compare deep learning-based prediction models including RadioUNET and four different variations of the UNET model for the power prediction task. More complex UNET variations improve the model on higher resolution frames such as \(256\times 256\). However, using the same models on lower resolutions results in overfitting and simpler models perform better. Our detailed numerical analysis shows that the deep learning models are effective in power prediction and they are able to generalize well to the new regions.

The Unusually Weak and Exceptionally Steep Radio Relic in A2108

Abstract Mergers between galaxy clusters often drive shocks into the intracluster medium, the effects of which are sometimes visible via temperature and density jumps in the X-ray and via radio emission from relativistic particles energized by the shock’s passage. A2108 was selected as a likely merger system through comparing the X-ray luminosity to the Planck Sunyaev–Zeldovich signal, where this cluster appeared highly X-ray underluminous. Follow-up observations confirmed it to be a merging low-mass cluster featuring two distinct subclusters, both with a highly disturbed X-ray morphology. Giant Metrewave Radio Telescope (GMRT) data in bands 2, 3, &amp; 4 (covering 120–750 MHz) show an extended radio feature resembling a radio relic near the location of a temperature discontinuity in the X-rays. We measure a Mach number from the X-ray temperature jump (  X = 1.6 ± 0.2 ). Several characteristics of radio relics (location and morphology of extended radio emission) are found in A2108, making this cluster one of the few low-mass mergers (M L−M = 1.8 ± 0.4 × 1014 M ⊙) likely hosting a radio relic. The radio spectrum is exceptionally steep (α = −2 at the lowest frequencies), and the radio power is very weak (P 1.4 GHz = 1 × 1022 W Hz−1). To account for the shock/relic offset, we propose a scenario in which the shock created the relic by re-accelerating a cloud of pre-existing relativistic electrons and then moved away, leaving behind a fading relic. The electron-aging timescale derived from the high-frequency steepening in the relic spectrum is consistent with the shock travel time to the observed X-ray discontinuity. However, the lower flux in GMRT band 4 data causing the steepening could be due to instrumental limitations and deeper radio data are needed to constrain the spectral slope of the relic at high frequencies. A background cluster, 4′ from the merger, may have contributed to the ROSAT and Planck signals, but SZ modeling shows that the merger system is still X-ray underluminous, supporting the use of this approach to identifying merger-disrupted clusters.

RDMST- A Novel Distributed Topology Control Algorithm for Low Probability of Detection Mobile Communication Networks

One aim of a military tactical network is to Lower the Probability of Detection, LPD, in order to hide the network from a possible adversary. Whilst there are numerous ways that communications can be hidden from an adversary the approach used in this paper is to minimise the transmitted power of the network's radios, whilst keeping the radios connected. Results from previous simulation experiments demonstrated the potential efficacy of these algorithms. In this paper we have implemented these algorithms into mobile radios and performed field trials to determine whether the LPD algorithm would transfer over into a more realistic environment. Problems associated with the noisy wireless medium were overcome and promising results obtained. This paper describes the field trials of the LPD algorithm, discusses some emerging issues, and presents the results from these trials.

CALIBRATION OF HIGH AND ULTRA-HIGH FREQUENCY POWER METERS IN THE RANGE OF UP TO 30 MHZ

High-frequency (HF) and ultra-high-frequency (UHF) power measurements are applied in various industries both in the development and design of radio-electronic equipment and in testing, commissioning, or repair. Since such measurements are one of the basic types of measurement for metrological support in the field of radio engineering and communication, it is necessary to ensure metrological traceability of the calibration of working standards and measuring instruments to standards on fundamental constants in wide frequency and dynamic ranges. The National primary standard of Ukraine for units of power of electromagnetic oscillations in coaxial paths reproduces units of power in the frequency range 0.03 … 18 GHz, and the frequency range of the nomenclature of watt-meters and power converters are much wider – from 9 kHz, and for some types of converters even from direct current. The calibration and measurement capabilities of HF and UHF power measurement of national laboratories of different countries were studied for the possibility of solving the issue of expanding the frequency range of calibration of HF and UHF power meters. The analysis of data on the calibration factor and the efficiency factor in coaxial paths with a resistance of 50 Ohm in the Database of Key Comparisons of the International Bureau of Weights and Measures was carried out. A study of possible solutions was carried out and a scheme was developed to reproduce a unit of power by units of voltage and resistance using a precision voltmeter Boonton 9242 RF for the calibration of measuring transducers Rohde&amp;Schwarz NRP-Z55 and NRP6A in the frequency range from 0.1 … 30 MHz. A reproduction model was created based on the developed scheme, and the contributions of the reproduction model components to the calibration result and the corresponding uncertainties of the model components were estimated. The measurement uncertainty budget was drawn up based on the proposed calibration model of radio signal power measuring transducers.

Development of the ion cyclotron emission diagnostic on the HL-2A tokamak

An ion cyclotron emission (ICE) diagnostic, which is based on a B-dot probe, has been recently designed and installed on HL-2A tokamak. The diagnostic is used to study various high-frequency magnetic field fluctuations which can be excited by energetic ions and runaway electrons in the plasma. The ICE diagnostic on HL-2A includes a high-frequency B-dot probe, direct current (DC) block, radio frequency splitters, filter bank and power detectors. The filter bank is composed of 16 channels filters, with the center frequency covering from 10 to 160 MHz, 10 MHz step length and 8 MHz bandwidth. The log detectors with a large dynamic range (from −80 dBm to −20 dBm) are used to detect the bandpass power. Test results of the B-dot probe, filters and power detectors are shown. The signals can also be sampled with a fast analog-to-digital converter with a 14-bit depth, 100 MHz bandwidth and 250 MSample/s sampling rate.

Reconfigurable Power Divider-Enabled Dynamic Hybrid m-MIMO Transmitter

A promising solution for massive Multiple-Input Multiple-Output (m-MIMO) systems is Hybrid digital-analogue (HDA) beamforming as it offers a balanced trade-off between energy efficiency (EE) and spectral efficiency (SE). The lack of practical demonstrations in the open literature is primarily because those most existing works require a large number of phase shifters (PSs), radio frequency (RF) switches, power dividers (PDs), and power combiners which contribute to high hardware complexity and energy consumption (due to insertion loss). In this paper, we introduce a practical dynamic subarray m-MIMO structure that is based on reconfigurable power dividers (RPDs). The extensive system simulation results, considering hardware imperfection extracted from a practical RPD implementation, indicate that the proposed RPD-based dynamic HDA m-MIMO outperforms the fixed subarray counterpart.