Receiver Antenna Research Articles

Channel estimation and detection with space–time transmission scheme in colocated multiple‐input and multiple‐output system

AbstractIn this study, a space–time transmission scheme is proposed to tackle the limitations of channel estimation with orthogonal pilot information in colocated multiple‐input multiple‐output systems with several transmitting and receiving antennas. Channel information is obtained using orthogonal pilots. Channel estimation introduces pilot heads required to estimate a channel. This leads to bandwidth insufficiency. As a result, trade‐offs exist between the number of pilots required to estimate a channel versus spectral efficiency. The detection of data symbols is performed using the maximum likelihood decoding method as it provides a consistent approach to parameter estimation problems. The moment‐generating function of the instantaneous signal‐to‐noise ratio is used to drive an approximate expression of the symbol error rate for the proposed scheme. Furthermore, the order of diversity is less by one than the number of receiver antennas used in the proposed scheme. The effect of the length of a pilot sequence on the proposed scheme's performance is also investigated.

A Unification of LoS, Non-LoS, and Quasi-LoS Signal Propagation in Wireless Channels

The modeling of wireless communication channels is often broken down into two distinct states, defined according to the optical viewpoints of the transmitter (TX) and receiver (RX) antennas, namely, line-of-sight (LoS) and non-LoS (NLoS). Movement of the TX, RX, both and/or objects in the surrounding environment means that channel conditions may transition between LoS and NLoS leading to a third state of signal propagation, namely, quasi-LoS (QLoS). Unfortunately, this state is largely ignored in the analysis of signal propagation in wireless channels. We, therefore, propose a new statistical framework that unifies signal propagation for LoS, NLoS, and QLoS channel conditions, leading to the creation of the three-state model (TSM). The TSM has a strong physical motivation, whereby the signal propagation mechanisms underlying each state are considered to be similar to those responsible for Rician fading. However, in the TSM, the dominant signal component, if present, can be subject to shadowing. To support the use of the TSM, we develop novel formulations for the probability density functions of the in-phase and quadrature components of the complex received signal, the received signal envelope, and the received signal phase. In addition, we derive an expression for the complex autocorrelation function of the TSM, which will be of particular importance in understanding and simulating its time correlation properties. Finally, we show that the TSM provides a good fit to field measurements obtained for two different body-centric wireless channels operating at 2.45 GHz, which are known to be subject to the phenomena underlying the TSM.

Two-Dimensional Phased-Array Receiver Based on Integrated Silicon True Time Delay Lines

In this work, we first demonstrate a complete 2-D photonics-aided phased-array antenna (PAA) receiver with so far the largest scale of 8 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\times $ </tex-math></inline-formula> 8 by utilizing highly integrated silicon true-time delay line chips. The prototype utilizes the wavelength-division-multiplexing technology to build the crucial optical beamforming network (OBFN) module so as to dramatically reduce the type and amount of silicon binary integrated optical time delay lines. The measured beam scanning range in the frequency range from 2 to 6 GHz is <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$90^{\circ }\,\,\times \,\,90^{\circ }$ </tex-math></inline-formula> with a beam-pointing step of 1°. Furthermore, due to the online channelized signal processing module, we systematically characterize sensitivity, RF gain, and dynamic range of the photonics-aided PAA. Considering that we first utilize the photonic integration technology to realize a 2-D PAA demonstrator with the largest scale and the highest technological maturity, we believe that it presents a milestone in the development of future microwave photonics-based radar systems.

A Compact 3-D Multisector Orientation Insensitive Wireless Power Transfer System

The power conversion efficiency (PCE) in wireless power transfer (WPT) degrades due to angular misalignment between the transmitter (Tx) and the rectenna (Rx) along the azimuth plane. Therefore, a compact 3-D multisector orientation insensitive WPT system is proposed to address this problem. The optimal number of sectors ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$N=8$ </tex-math></inline-formula> ) is determined analytically using patch antenna design equations to mitigate the effects of angular misalignment. In addition, conditions on the receiver antenna radiation pattern are investigated to enhance the performance of the WPT system. Furthermore, the observed conditions are utilized for designing a high gain WPT system at 5.8 GHz with <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$N=8$ </tex-math></inline-formula> sectors. The proposed WPT system provides uniform power harvesting capability in the azimuth plane and 51.2% higher power harvesting capacity than the patch antenna WPT system.

Modeling of dielectric resonator antenna array for retina photoreceptors

The retina encompasses several cone and rod photoreceptors at fovea region i.e., 90 million cells of rod photoreceptors and 4.5million cells of cone photoreceptors. The overall photoreceptors determine the vision of every human. An electromagnetic dielectric resonator antenna has been presented for retina photoreceptors in order to model them at fovea and its peripheral retina with the respected angular spectrum. Three coloring primary system of human eye (R, G, B) can be realized based on the model. Three miscellaneous models i.e., simple, graphene coated, and interdigital models have been presented in this paper. The nonlinear property of interdigital structures is one of the best advantages to use for creating the capacitor. The capacitance property helps improving the upper band of visible spectrum. The absorption of light for graphene as an energy harvesting material and its conversion into electrochemical signals is making it one of the best models. The mentioned three electromagnetic models of human photoreceptors have been expressed as a receiver antenna. The proposed electromagnetic models based on dielectric resonator antenna (DRA) are being analyzed for cones and rods photoreceptors of retina in the human eye by Finite Integral Method (FIM) utilized by CST MWS. The results show that the models are so fine for vision spectrum due to its localized near field enhancement property. The results indicate fine parameters of S11 (return loss below -10 dB) with invaluable resonants in a wide range of frequencies from 405 THz to 790 THz (vision spectrum), appropriate S21 (insertion loss 3-dB bandwidth), very good field distribution of electric and magnetic fields for flowing the power and electrochemical signals. Finally, mfERG clinical and experimental results validate the numeric results by the normalized output to input ratio of these models and it points out that these models can stimulate the electrochemical signals in photoreceptor cells for the best suiting of realizing the new retinal implants.

Direct Modeling of Thermal-Radiation Reception by Antenna in Close Range

In this work, an interesting near-field propagation problem in the microwave radiometer calibration is addressed, which is the antenna reception of thermal radiation from calibration target. Efforts in simultaneously modeling the target and antenna within the same 2-D full-wave scenario are reported. Specifically, the coated pyramids and horn antennas are considered. Based on the incoherent nature of local thermal sources in the coating layer and the fluctuation-dissipation theorem (FDT), the direct modeling of receiving power and further brightness temperature ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$BT$ </tex-math></inline-formula> ) at the antenna waveguide port can be achieved. The direct modeling is then quantified based on the classic concept of antenna reception in an ideal blackbody chamber. Further, it is shown in the results that mutual coupling affects the antenna reception in a fluctuating manner, and the target structural radiation raises the antenna reception in a very close distance. That means, the thermal reception can be affected by both the antenna and target structures in the near field. Also, the Lambertian radiation properties of the coated pyramidal blackbody are clarified in the direct calculated results. This work reveals the complex scenario of close range <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$BT$ </tex-math></inline-formula> transfer, and opens the possibility of quantitatively modeling it for practical applications with further investigations.

Receive antenna selection for MMSE signal detection in multiuser massive MIMO uplink

The problem of arbitrarily selecting only some of the antennas for signal reception in the multiuser massive multiple-input multiple-output (MIMO) uplink is examined. A binary quadratic program (BQP) based on maximizing the sum of signal-to-interference and noise ratio (SINR) is formulated to fulfill this task. It can then be relaxed to be convex and solved efficiently. Simulation results show that using the proposed antenna selection together with the minimum mean-squared error (MMSE) signal detection, if the number of receive antennas is reduced from N to N a , its error-rate performance can be better than that of the system originally equipped with N a receive antennas employing the same MMSE signal detection.

Time-Switching Symmetric Transmitter Array to Increase Sweet Region for Far-Field Wireless Power Transmission Under Receiver Rotation and Location Variation

For wireless power transfer using linear-polarized transmitter (TX) and receiver antennas, the rotation and movement of receiving antenna cause received power variation. The received power pattern is proposed to describe the received power variation from a specific TX antenna under receiver rotation. By placing the peak of the received power pattern of additional TX antennas in null directions of the previous TX antenna, received power variation due to rotation can be compensated. With symmetrically placed TX antennas, the power variation due to location variation can be compensated. This article proposes a time-switching symmetric transmitting array combining both techniques to increase the sweet region for far-field wireless power transfer under rotation and location variation. A sweet region is an area in the 2-D case or volume in the 3-D case, which is defined as an area or a volume inside the TX array that can get guaranteed minimum received power under rotation. The received power calculation using the Friis equation with short dipole antenna pattern shows that a symmetric TX array can achieve a larger sweet region than an asymmetric TX array under the same total transmitted power. The efficiency for the receiver at the origin is 1/2 at the 2-D case and 1/3 at the 3-D case. In the experiment, a linear-polarized TX array at 915 MHz with monopole receiver antenna and power detector is used as the receiver to measure received power under rotation and location variation. Measurement results at 2-D and 3-D cases confirm the received power level predicted by calculation using the Friis equation. The power budget calculation for wirelessly powering a sensor module attached on a bee inside a beehive using the proposed 3-D TX array shows that it is feasible to deliver sufficient power to the sensor module regardless of the orientation and location of the bee inside the beehive.

Analysis and Design of RF Energy-Harvesting Systems With Impedance-Aware Rectifier Sizing

Because of the interaction between the internal blocks of an RF energy harvesting (RFEH) system, sizing a rectifier only for high power conversion efficiency (PCE) is insufficient for improving global power harvesting efficiency (PHE). This brief analyzes and sizes the rectifier by taking its input and output impedances into account with a two-port model that combines the rectifier AC and DC characteristics. The AC characteristic in this model is used for impedance-aware rectifier sizing. We target a low input-impedance rectifier for better impedance matching between the receiver antenna and the rectifier. The DC characteristic describes the rectifier power loss allocation and estimates its maximum power point. A proposed parasitic-aware matching network sizing methodology predicts the PHE is finally limited by Ohmic loss in the matching network at a low incident power level. For overcoming this limitation, this brief also analyzes the impact of multiple rectifier stages on RFEH with a high peak-to-average power ratio (high-PAPR) incident waveform for improving the PHE. We design an RFEH prototype with a sized 28nm CMOS two-stage cross-coupled rectifier. Measurement results show sensitivity as low as −28.3 dBm with a peak PHE of 31.1% at −16.5 dBm 2.45-GHz high-PAPR incident power. It has sufficient high output impedance to prevent reverse leakage without the need for an additional self-gating circuit.

Fast Fluid Antenna Multiple Access Enabling Massive Connectivity

Massive connectivity over wireless channels relies on aggressive spectrum sharing techniques. Conventionally, this may be achieved by sophisticated signal processing and optimization of applying multiple antennas and/or complex multiuser decoding at each user terminal (UT). Different from previous methods, this letter proposes a radical approach for massive connectivity, which employs fluid antenna at each UT to exploit the interference null, created naturally by multipath propagation and the randomness of UT’s data, on a symbol-by-symbol basis for multiple access. The proposed fast fluid antenna multiple access ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$f$ </tex-math></inline-formula> -FAMA) system adopts a large, distributed antenna array at the base station (BS) to transmit each UT’s signal from each of the BS antennas and lets each UT overcome the interference on its own using its fluid antenna. Our main contribution is a technique that estimates the best port of fluid antenna for reception at every symbol instance. The proposed approach needs only cross-correlation calculations and single-user decoding at each UT and requires no precoding at the BS. Simulation results demonstrate that for a BS with 16 antennas supporting 16 co-channel users, a multiplexing gain of 14.87 is achieved even when the channel has a strong line-of-sight (LoS) and multipath is few. The multiplexing gain can also rise to 24.36 if a 30-antenna BS is serving 30 co-channel users.

Direction and distribution sensitivity of sup-DOF interference suppression for GNSS array antenna receiver

Introduction: Distributed wideband jamming (interference) is commonly used in navigation countermeasure. Due to the limited volume of GNSS (Global Navigation Satellite System) array antenna receiver, the number of interferences usually exceeds the number of array elements. At present, the anti-jamming capability and mechanism of Global Navigation Satellite System array antenna against distributed sup-DOF (Degree of Freedom) interference have not been fully studied.Methods and innovation: To solve this problem, this paper analyzes the characteristics of GNSS System array antenna against sup-Degree of Freedom interference by formula derivation and simulation. Firstly, the definition of sup-Degree of Freedom interference of Global Navigation Satellite System array antenna is proposed from the perspective of spatial anti-jamming; Secondly, the directional characteristics of Global Navigation Satellite System array antenna for sup-Degree of Freedom interference suppression are analyzed.Results: The results show that the performance of sup-Degree of Freedom interference suppression is sensitive to the direction and distribution of interference. On the one hand, the residual interference power varies from interference direction and distribution, while the minimum value of which is zero and the maximum value is the sum of interference power. On the other hand, the suppression performance of UCA (Uniform Circular Array) and central Uniform Circular Array is periodic along azimuth. If the number of elements on the circumference is M (M ≥ 3), the period of the suppression performance is 4π/M/3+(−1M+1.Discussion: The conclusion of this paper show the upper and lower bounds of sup-Degree of Freedom interference suppression performance and the variation rule in azimuth, which can be used in the fields such as interference deployment, anti-jamming performance evaluation and anti-jamming algorithm development.

Analysis of Vsat Gyro performance based on the power level of the antenna receiver on the Pelni ship

The satellite communication system that is used for ship communication in Indonesian waters is expected to transmit real time data at any time under any conditions. However, currently, the Vsat Gyrsoscope antenna that is installed on the Pelni ship still uses the Ku band frequency. This frequency band is very susceptible to rain attenuation. Vsat Gyro will automatically search for satellites that cover it. Only when it is raining and the ship is moving towards the port, is there a decrease in the receiving power level. SNR and power and C/N will drop. Therefore, it is necessary to do an analysis to overcome this problem so that it is not disconnected during the transmission. This study conducted an analytical study to validate the analytical predictions of phasing the vsat power signal level on the pelni ship to maintain communication during sea operations, which are included in TKT 3 (three). The tools used in the measurement are vsat modem, PRTG application, laptop, RJ 45 cable, and Spectrum Analyzer. By optimizing the calculation of the margin link budget, the calculation of Qos and the parameters vsat Eb/No, C/N and SNR when adjusted to the operating conditions of the ship with high rain intensity so that communication can continue to run even when the worst conditions can be maintained properly.Â

Multipurpose Laser Instrument for Interplanetary Ranging, Time Transfer, and Wideband Communications

In this paper, we discuss the design and feasibility of a multifunctional laser instrument capable of precision ranging, time transfer, and wideband communications over interplanetary distances throughout our solar system. To simplify the communications discussion, On-Off Keying (OOK) is assumed for the high bandwidth (MHz to GHz) modulation format, and the required laser powers and transmit and receive apertures are determined for each Earth–planet link as a function of data rate. Optimization of the transmitter and receiver antenna gains is reviewed. It is further assumed that the spacecraft is in orbit about the planet of interest in order to justify the need for large data downloads rates and that single-photon sensitive detector arrays can be utilized to aid in the acquisition, detection, and tracking of the opposite terminal. Satellite acquisition and tracking is complicated by the long one-way propagation distances (up to 40 AU), the finite speed of light, the orbital and rotational velocities of the two planets, and, if applicable, the spacecraft orbital speed about the planet. Taking advantage of the highly circular and coplanar planetary orbits within our solar system, point ahead angles are estimated for all combinations of possible Earth–planet positions revealing solar orbital geometries where planetary motion does not introduce a need for point ahead angles. Finally, possible methods for simplifying the initial mutual acquisition of the planetary and Earth terminals and maintaining the coalignment of their respective optical systems is discussed.

Deep Learning Based Channel Estimation for MIMO-OFDM System with Modified ResNet Model

Objectives: The effectiveness of wireless communication systems is significantly influenced by channel estimation. In order to accurately estimate the Channel Impulse Response (CIR) of the channel under varied circumstances, channel estimation is a crucial procedure in the functioning of MIMO-OFDM (Multi-Input and Multi-Output – Orthogonal Frequency Division Multiplexing) systems. Methods: The proposed Deep Learning(DL) based Convolutional Neural Network (CNN) with modified ResNet architecture channel estimation method improves the Bit Error Rate(BER) and Mean Square Error(MSE) performance compared to conventional channel estimation methods. We have compared the proposed CNN method with the Least square (LS), Minimum Mean Square Error(MMSE) and Deep Neural Network(DNN) based channel estimation methods. The results have been discussed by using BER and MSE versus SNR graphs. The simulation results are being performed on the MATLAB platform of the R2021b version. Findings: The DL-based MIMO-OFDM channel estimation can achieve better performance over multipath fading channels if Channel coefficients are perfectly estimated at the receiver. The simulation test is carried out in different test conditions by considering the different number of transmitter and receiver antennas with respect to different QAM modulation order values. Novelty: The DL-based modified ResNet architecture comprises a set of layers modified to estimate the optimal channel parameters. For achieving a great reduction of MSE and BER compared to conventional channel estimation methods, the layers of the ResNet– model are modified. Keywords: Channel estimation; MIMOOFDM system; Deep learning; Neural network; ResNet

Compressed Sensing Based Active User Detection in MIMO Systems With One-Bit ADC

We investigate an active user detection for massive machine-type communication systems, in which a massive number of users with sporadic transmission communicate with a base station (BS) with multiple antennas. Due to hardware cost and power consumption, it is assumed that each receiver antenna at the BS is equipped with one-bit analog-to-digital converter (ADC). This problem can be formulated as a new compressed sensing problem with one-bit quantized multiple measurement vectors (termed one-bit CS-MMV). In this paper, we propose a novel algorithm (named Turbo-QISTA) by properly incorporating Turbo principle into quantized iterative shrinkage threshold algorithm (QISTA). Our major contribution is to design two key metrics (i.e., extrinsic and a priori information) of Turbo principle suitable for one-bit CS-MMV problem. Via simulations, we demonstrate the superiority of the proposed Turbo-QISTA.

Опыт использования метода ГНСС-рефлектометрии для измерения высоты снежного покрова

Height of the snow cover is an important parameter used to predict crop yields and floods. The traditional method of measuring the height of the snow cover according to the readings of three snow gauges has the disadvantage that in open areas the snow cover is blown out and redistributed under the influence of the wind. The new method of GNSS reflectometry makes it possible to circumvent this disadvantage by averaging the height of the snow cover over a certain local area around the antenna of the ground-based GNSS radio signal receiver. The aim of the study is to assess the accuracy of determining the height of the snow cover using GNSS reflectometry using the example of the IRKM station (Irkutsk city) for the winter period 2021/2022. It has been established that the standard deviation of heights of the snow cover determined by reflectometry of GPS and GLONASS radio signals from heights of the snow cover recorded by the traditional method at a meteorological station was 3,2 cm. The standard deviation of heights of snow cover obtained from the results of processing only GLONASS radio signals was 5,6 cm. At the same time, for the GLONASS system, the dependence of the discrepancies with the reference data on the height of the snow cover is obvious: the greater the depth of the snow cover, the smaller the discrepancies. Thus, the standard deviation of discrepancies, calculated under conditions of the height of the snow cover above 10 cm, is only 3,0 cm. Thus, it can be preliminarily concluded that the GNSS refletometry method is able to supplement the traditional method of measuring the height of the snow cover.

Разработка имитационной модели определения координат воздушных объектов по отраженному от воздушного объекта и принятому на антенну навигационного приемника навигационному сигналу ГНСС

This article is devoted to the development of a simulation model for determining the coordinates of air objects based on the GNSS navigation signal reflected from the air object and received on the antenna of the navigation receiver. To solve the problem of radar of aerial objects using bistatic location based on the use of GNSS satellites, it was necessary to pre-evaluate the energy or energy potential of the satellite navigation signal reflected from the aerial object, which then comes to the receiving antenna of the navigation equipment of consumers. The results obtained in the form of the developed computational schemes will form the basis of the algorithmic and software of the passive radar system and will allow determining the requirements for its technical support carried out within the framework of the grant project of the Ministry of Education and Science of the Republic of Kazakhstan No. AP09260581. In this paper, simulation modeling is understood as such an approach to modeling complex systems, which allows us to develop a single meta-model that combines into an integral set of models of objects and processes of their interaction based on a single information and event space in a single discrete time scale, and implement the resulting meta-model in an electronically equivalent form on an electronic computer. One of the main tasks of the study of complex radio engineering systems by modeling is the choice of modeling principles that should allow the construction of the simulated system in accordance with the goals and objectives of the study in such a way that the model adequately reflects the processes and patterns of behavior of the system under study with the necessary degree of reliability and detail. One of the most productive methods of developing a software and hardware complex of simulation modeling is object-oriented modeling.

On the Performance of Tree-Based Antennas for SLF-VLF Signal Reception

On the Performance of Tree-Based Antennas for SLF-VLF Signal Reception

Angular Localization of Radio-frequency Sources Using a Compact Metamaterial Receive Antenna

Angular Localization of Radio-frequency Sources Using a Compact Metamaterial Receive Antenna

Joint Time Index Modulation and Receive Antenna Selection for RIS-Aided Communications

Joint Time Index Modulation and Receive Antenna Selection for RIS-Aided Communications