RF Communication Systems Research Articles

Reduction of TCF effect in FBAR devices using DC bias

This study investigates the effect of applied DC bias on the resonant and antiresonant frequency of FBAR devices. In our model, we introduce linear electrostrictive coefficients and compare the theoretical results with experimental data. The FBAR structure utilizes an air cavity as the acoustic reflector layer, with Mo and AlN as the materials for the top/bottom electrodes and the piezoelectric layer, respectively. The resonant and antiresonant frequencies of the FBAR are designed at 2313.1 and 2374.7 MHz, respectively. Under an applied DC bias ranging from −10 to +10 V, the frequency shifts for the resonant and antiresonant frequencies are 37.7 and 27.7 ppm/V, respectively. The theoretical results, incorporating linear electrostrictive coefficients N=−7×1010 and G=−5×109, show excellent agreement with the measured results of the FBAR device. Finally, we compensated for the frequency drift by applying a 20 V DC bias at high temperatures to the FBAR device. These findings have significant implications for improving the performance of RF communication systems in varying temperature environments.

Power-efficient wideband programmable pseudo differential ring oscillator CP-PLL

A power-efficient, wide-band, programmable pseudo-differential ring-oscillator charge-pump phase-locked loop (CP-PLL) is proposed. The ring-VCO, characterized by its low power consumption and broadband, is achieved based on a feedforward pseudo-differential configuration. The linearity of ring-VCO is improved by using the source negative feedback topology. Through the rail-to-rail operatingamplifier clamping current source, the current matching accuracy is improved to realize a high-performance CP circuit. The results show that the output frequency range of the phase-locked loop is 0.6–6 GHz at a 1.2 V supply voltage, and the power consumption is 1.372 mW at 5 GHz with a lock-up time of 1.72 μs and RMS jitter of 9.3 ps. The power consumption is as low as 0.643 mW at 2.5 GHz and 1.067 mW at 4 GHz, and the final layout area is 0.00716 mm2. The implemented CP-PLL can be used effectively in wireless RF communication system of NB-IoT and intelligent edge computing scenario.

DGS Based CP Antenna for 5G Communication with Harmonic

Higher harmonics in antennas contribute to negative effects on antenna performance such as interference, radiation pattern distortion, impedance mismatch and increased complexity in design, commonly occurring in RF communication systems caused by the non-uniformity of the antenna structure and the presence of parasitic elements. Therefore, a patch antenna operating at 3.65GHz for 5G mobile communication that incorporates techniques to suppress unwanted higher harmonics is presented. The antenna design employs a basic rectangular patch antenna with an inset feed technique to enhance the S11 parameters at the resonant frequency. Additionally, two dumbbell defected ground structures (DGS) are employed to minimize the higher modes of harmonic distortion. To transform the antenna into a circular polarized (CP) antenna, two truncated corners and a cross slot perpendicular to the middle of the patch are introduced. The proposed antenna is able to suppress unwanted harmonics at higher resonances, demonstrating its effectiveness in mitigating harmonic distortion

A Compact Negative Group Delay Microstrip Diplexer with Low Losses for 5G Applications

Microstrip Diplexers play an important role in modern wireless communication systems. In this paper, a novel compact microstrip diplexer based on spiral cells is presented. The proposed resonator primarily consists of two spiral thin lines connected to a pair of coupled lines. This novel resonator is analyzed mathematically to find its behavior and tune the dimensions of the final layout easily. Using the analyzed resonator, two bandpass filters (BPFs) are designed. Then, a novel high-performance microstrip diplexer is obtained by designing and integrating these two BPFs. The center frequencies of the first and second channels of the proposed diplexer are 1.86 GHz and 4.62 GHz, respectively. The proposed diplexer boasts a remarkably small size of 0.004 λg2 and features flat channels with low insertion losses of only 0.048 dB and 0.065 dB for the first and second channels, respectively. The maximum group delays of S21 and S31 are 0.31 ns, 0.86 ns, respectively, which are good values for a modern communication system. Meanwhile, inside its passbands for some frequency ranges, its group delays are negative. Thus, using this diplexer can decrease the signal dispersion. The 1st and 2nd passbands are wide with 47.3% and 47.1% fractional bandwidths (FBW), respectively. Therefore, this diplexer can be easily and successfully used in designing high-performance RF communication systems.

Research on Bulk Acoustic Wave Resonator Based on Phononic Crystal

Abstract With the continuous advancement of information technology and the rapid development of mobile communication technology, from smart home to automatic driving of cars, and then to the application and development of virtual reality, communication technology has evolved from the earliest communication between people to communication between things. The frequency band supported by smart phones and various small mobile terminals is increasing, and their communication frequency is also gradually increasing, which brings some challenges to the traditional RF front-end devices. The traditional RF filter can not meet the current market demand because of its own performance and size constraints. As the best option to integrate with RF circuit or microwave circuit, bulk acoustic wave filter has great development and application prospects in modern RF communication system. This paper will focus on the solid-state assembled resonators based on one-dimensional and two-dimensional phononic crystals, analyze the influence and change law of the performance of bulk acoustic wave devices based on two-dimensional phononic crystals, then explore the main loss mechanism existing in solid-state assembled devices, and propose improvement schemes, which lays a foundation for the application of solid-state assembled resonators in today’s RF front-end.

Design and fabrication of a compact branch-line hybrid coupler with a balanced phase using a new microstrip structure for GSM applications

A novel microstrip quadrature hybrid coupler is mathematically designed, optimized and fabricated in this work. The physical structure of the proposed coupler is new and it occupies a very small area of 0.01 λg2. The novel stubs embedded inside the conventional rectangle are connected parallel lines. The ends of these stubs are connected to a solid rectangle, which make the overall structure different from the previous works. Our branch-line coupler is designed to work at 1.8 GHz for GSM applications. The phase imbalance between S21 and S31 is only 0.01°, which is very small compared to the previous works. Another advantage of the presented coupler is its high isolation, which is about 40 dB. Meanwhile, other parameters such as common port return loss and coupling factors are desired. To design this coupler, two low-loss lowpass filters (LPFs) are designed and embedded in the main structure. A mathematical design method is presented to decrease the losses, where a 0.002 dB insertion loss for the LPF is achieved. We measured the presented structure. The measurement results verifies the simulations with high accuracy. Therefore, due to having a novel structure, very small size, the lowest phase shift, good isolation and good return loss the proposed coupler can be easily used in RF communication systems.

Design and Optimization of a Compact Microstrip Filtering Coupler With Low Losses and Improved Group Delay for High-Performance RF Communication Systems

Design and Optimization of a Compact Microstrip Filtering Coupler With Low Losses and Improved Group Delay for High-Performance RF Communication Systems

Performance analysis of free space optic transmission link for broadband access networks

Abstract Since the last two decades free space optical (FSO) communication transcends the RF communication and microwave systems because of its capability of carrying high bandwidth, license-free, long-range, small size, high bandwidth, low cost and ease of deployment. FSO communication has few limitations as well like beam dispersion, scintillation, weather effects etc. This paper demonstrates the implementation of FSO link and analysis of transmission performance of FSO channel for broadband access networks. The proposed FSO link is simulated in opti-system to analyze the physical characteristics of transmitter and receiver. The transmission performances of FSO link are validated using on/off keying (OOK) and differential phase shift keying (DPSK) at various atmospheric conditions with different data rates and transmission ranges. The transmission performance of the FSO link is analyzed under the influence of key parameters like launch power, beam divergence, atmospheric attenuation, receiver sensitivity and receiver aperture. The proposed model of the FSO link is investigated using key parameters like optical signal to noise ratio (OSNR), noise figure and bit error rate (BER).

Compact 5G Nonuniform Transmission Line Interdigital Bandpass Filter for 5G/UWB Reconfigurable Antenna

In this study, at two different fifth generation (5G) low-frequency bands (3.7-4.2 GHz and 5.975-7.125 GHz) and based on nonuniform transmission lines (NTLs) theory, a compact three-quarter-wave resonators interdigital bandpass filter (IBPF) is analyzed, designed, and fabricated. The compact proposed filter is considered as a good candidate for reconfigurable 5G low-frequency bands and ultrawide band (UWB) antenna, which will reduce the size of the final RF communication system. Firstly, a uniform transmission line (UTL) IBPF at these two bands is designed and tested; then the NTL concept is applied for compactness. For both UTL and NTL IBPFs, different parametric studies are performed for optimization. At the first frequency band, size reductions of 16.88% and 16.83% are achieved in the first (symmetrical to the third resonator) and second λ/4 resonator of UTL IBPF, respectively, with up to 36.6% reduction in the total area. However, 16.46% and 16.33% size reductions are obtained in the first (symmetrical to the third resonator) and second λ/4 resonator, respectively, at the second frequency band with a 40.53% reduction in the whole circuit area. The performance of the proposed NTL IBPF is compared with the UTL IBPF. The measured reflection coefficient of the proposed NTL IBPF, S11, appears to be less than -10.53 dB and -11.27 dB through 3.7-4.25 GHz and 5.94-7.67 GHz, respectively. However, the transmission coefficient, S12 is around -0.86 dB and-1.7 dB at the center frequencies, fc = 3.98 GHz and 6.81 GHz, respectively. In this study, simulations are carried out using high-frequency structure simulator (HFSS) software based on the finite element method (FEM). The validity of the proposed theoretical schematic of this filter is proved by design simulations and measured results of its prototype.

A Brief Overview of Energy Efficiency Resources in Emerging Wireless Communication Systems

It is crucial to design new communication technologies to surmount the setbacks in RF communication systems. A suitable energy-efficiency scheme helps evade needless energy consumption in wireless communication. Appropriate choice of the most suitable energy-efficiency scheme aids in selecting the most energy-efficient equipment to minimize the expense of energy towards decreasing individual network element energy consumption without affecting their unique features. This review presents the energy efficiency challenges in wireless communication by employing different technologies. The emergence of visible light communication (VLC) provides an energy-efficient wireless communication system despite the various challenges inherent in its adoption that limit its physical realization. This work seeks to harness the potential of the transmission capabilities of VLC while providing an insight into novel practical implementation techniques. The work also addresses the energy consumption problem of low-active components and idle period of active components of base stations by using sleep modes for their systematic turning off and on. The high cost of power supply and the environmental emission of gases from base stations are also addressed by integrating a renewable energy resource into the conventional standalone diesel generators. Overall, the work provides an overview of information necessary for foundational research in energy-efficient resources applied to emerging wireless communication systems.

Statistical Analysis Based Feature Selection Enhanced RF-PUF With >99.8% Accuracy on Unmodified Commodity Transmitters for IoT Physical Security

Due to the diverse and mobile nature of the deployment environment, smart commodity devices are vulnerable to various spoofing attacks which can allow a rogue device to get access to a large network. The vulnerability of the traditional digital signature-based authentication system lies in the fact that it uses only a key/pin, ignoring the device fingerprint. To circumvent the inherent weakness of the traditional system, various physical signature-based RF fingerprinting methods have been proposed in literature and RF-PUF is a promising choice among them. RF-PUF utilizes the inherent nonidealities of the traditional RF communication system as features at the receiver to uniquely identify a transmitter. It is resilient to key-hacking methods due to the absence of secret key requirements and does not require any additional circuitry on the transmitter end (no additional power, area, and computational burden). However, the concept of RF-PUF was proposed using MATLAB-generated data, which cannot ensure the presence of device entropy mapped to the system-level nonidealities. Hence, an experimental validation using commercial devices is necessary to prove its efficacy. In this work, for the first time, we analyze the effectiveness of RF-PUF on commodity devices, purchased off-the-shelf, without any modifications whatsoever. We have collected data from 30 Xbee S2C modules used as transmitters and released as a public dataset. A new feature has been engineered through PCA and statistical property analysis. With a new and robust feature set, it has been shown that 95% accuracy can be achieved using only ∼1.8 ms of test data fed into a neural network of 10 neurons in 1 layer, reaching >99.8% accuracy with a network of higher model capacity, for the first time in literature without any assisting digital preamble. The design space has been explored in detail and the effect of the wireless channel has been investigated. The performance of some popular machine learning algorithms has been tested and compared with the neural network approach. A thorough investigation of various PUF properties has been done. With extensive testing of 41238000 cases, the detection probability for RF-PUF for our data is found to be 0.9987, which, for the first time, experimentally establishes RF-PUF as a strong authentication method. Finally, the potential attack models and the robustness of RF-PUF against them have been discussed.

Stochastic Geometry-Based Interference Characterization for RF and VLC-Based Vehicular Communication System

In this article, we characterize various aspects of stochastic behavior of intervehicular interference by modeling location of road vehicles as a spatial Poisson point process. We make use of various analytical tools of stochastic geometry to provide an analytical framework to access the performance for both vehicular-radio frequency (V-RF) communication and vehicular-visible light communication (V-VLC) for dense, medium, and sparse traffic scenarios. The developed framework is also precise in terms of capturing the impact of reducing field-of-view (FOV) of receiver on the level of interference experienced from interferers for V-VLC. The performance has been evaluated and compared under normal atmospheric conditions as well as different environmental deterrents viz., light fog, dense fog, and dry snow conditions in terms of probability of successful transmission as a performance metric. Irrespective of any traffic scenario, the performance of V-VLC communication under normal atmospheric condition always outperforms V-RF communication. However, the performance of V-RF communication is comparatively better than V-VLC under various environmental deterrents. The proposed result motivates the benefit of employing RF-based or VLC-based vehicular-to-vehicular (V2V) communication which takes into account different environmental conditions as well as meets the diverse application requirements for future intelligent transportation system.

Recent Progress of 2D Nanomaterials for Application on Microwave Absorption: A Comprehensive Study

Rapid advancements and wide spread of microwave- and RF-communication systems over the years have led to an abundant increase in electromagnetic energy radiation in our living environment. Such an increase in microwave sources is due to the development and advancement in communication techniques (mobile phones, laptops, and antennas for aeronautics or automobile) and electronic warfare in the military field (radar and satellite). Recently research efforts are focused on finding solutions to guarantee protection from electromagnetic (EM) radiations. The EM absorbing materials are used to overcome these issues to ensure public protection as well as safe military operations. Various types of EM absorbing materials comprising composite materials have been progressively developed and researched. This kind of material is developed by impeding absorbing charges (magnetic or dielectric) into a host matrix material. Recently, carbon allotropes such as graphene, MXenes, carbon nanotubes (CNTs), and carbon fibers have attracted increasing attention owing to their EMI shielding characteristics and lightweight. This work presents a comprehensive study on the recent research progress on the application of nanomaterials for electromagnetic shielding and absorption. The review will cover the microwave absorption mechanism and absorption performance using graphene, MXenes, carbon nanotubes (CNTs), carbides, and ferromagnetic metals. Overall, the review will present a timely update on the research progress of microwave absorption performance of various nanomaterials.

Performance analysis of EBG bandstop filter using U: shaped meander type electrostatically actuated RF MEMS switch

Now a days, filters became essential component in many of the RF, satellites and wireless communication networks and system. The size and complexity of the system increases while dealing with multiple frequencies which employs a large number of filters. Hence, a single filter which can reconfigure at multiple frequencies is much more needed in the present scenario. In this paper, a reconfigurable band stop filter is designed by integrating RF MEMS switch. The proposed switch is modelled with U—shaped meanders which offers low spring constant of 1.54 N/m to reduce the Pull—in—voltage to 5.2 V. The suspended beam in the switch is actuated to reconfigure the frequency of the filter by varying the capacitance from upstate to down state. The reconfiguration in the frequency of filter is observed from 16.36 to 12.34 GHz showing good isolation of – 22.7 dB at 16.36 GHz and − 36.85 dB at 12.34 GHz. The analysis in the paper is carried out using COMSOL and HFSS FEM tools to understand the electromechanical and electromagnetic characteristics of both switch and Filter for Ku-band frequency application.

Power Management IC for a Dual-Input-Triple-Output Energy Harvester.

We present the design of a power management integrated circuit that processes harvested energy from radio frequency waves and piezoelectric vibrations. The rectification of piezoelectric and RF sources has a power conversion efficiency (PCE) of 87.73% and 74.70%, respectively. The asynchronous and microcontroller-less integrated circuit (IC) is designed to be low power, so the bulk of the harvested energy goes to three loads. The output peak powers of 111 μW, 156 μW, and 128 μW will be sufficient to run small devices for RF communication systems.

Antenna Diversity to Increase Reliability in Industrials Wireless Sensors Networks

Industrial WSNs are gradually gaining space in industry due to low cost of installation and maintenance. However, RF communications systems are prone to several propagation phenomena which can compromise reliability in terms of missed message deadlines. This work aims to increase the robustness of industrial WSN. In order to achieve this goal, it is necessary to correct inherent problems in wireless communications, some of which are channel noise, interference, and multipath fading. Multipath can be considered the main factor that makes communications in wireless sensor networks a real challenge when compared to other types of mediums, such as optical fiber, cable, or even directional radio transmissions. In this sense, antenna diversity is proposed as a solution to deal with these effects, with the aim of improving radio reliability to make the use of dense industrial WSN feasible. The potential of antenna diversity in WSN is not fully exploited in industrial applications. This article presents the combination of selection technique for industrial WSN through an algorithm that selects the transceiver port that has the highest link quality indicator and performs antenna switching in the radio modules. The results obtained are analyzed to verify the diversity gain by using antenna spatial diversity at reception and thus reduce packet error rate. The results corroborate with theory by increasing radio reliability in terms of diversity gain, quadrupling the received signal power when the correct antenna is chosen.

An investigation on time dependency of K index-based geomagnetic storm conditions observed over different locations of North America

Today, the scientists and researchers from almost every corner of the world are well aware of the adverse effects of geomagnetic storms on our highly expensive electrical and electromagnetic systems such as power grid transmission, satellite communication, RF communication systems, etc. The severe damaging effects of these storms on human health and on other inhabitants of the biosphere are also not unknown. A survey of literature on space science reveals that location or space dependency of these geomagnetic storms has already been established. Now the question may arise—Are geomagnetic storms time-dependent? To answer this question, a laborious exercise has been performed. K-index data obtained from the US Department of Commerce, NOAA, Space Weather Prediction Center, for the year, started from 1994 to 2014 (21 years) over three different locations namely Fredericksburg, College, and Estimated Planetary, are analyzed statistically for the eight different time periods namely 00:00–03:00, 03:00–06:00, 06:00–09:00, 09:00–12:00, 12:00–15:00, 15:00–18:00, 18:00–21:00, 21:00–24:00 hours respectively. Results thus obtained have concluded that apart from space or location dependency the geomagnetic storms are time-dependent also.

A novel hybrid FSO / RF communication system with receive diversity

This paper presents a novel model for hybrid Free Space Optical / Radio Frequency (FSO / RF) communication system with receive diversity. It is the first time that in a one-hop hybrid FSO / RF system, receive diversity is being used. Also, it is the first time that a one-hop hybrid FSO / RF system is being investigated in Negative Exponential atmospheric turbulence. For the first time, closed-form expression for Outage Probability of the presented system is being derived and verified through MATLAB simulation. It is shown that at low average Signal to Noise Ratio (SNR), FSO system with receive diversity performs better than RF system with receive diversity and almost equal to the proposed system, but by the increase of average SNR, its performance degrades compared with the two other systems. This system has a complex receiver, but it should be noted that the addition of this complexity, significantly reduces power consumption and improves system performance.

RF energy harvesting systems: An overview and design issues

One of the main challenges in implementing sensor devices for internet of things (IoTs), is the means for the operating power supply. RF energy harvesting (RFEH) presents a promising solution as RF power is a suitable choice particularly for cases where solar harvesting is not feasible. However, in spite of RF communication system design being a well-established, there are several challenges poised for the implementation of the RFEH systems especially for harvesting the ambient RF signals. The challenges can be widely categorized as the overall conversion efficiency, bandwidth, and form factor. In this article, an exhaustive survey on the different RFEH system that is reported is carried out and discussed. Important design issues are identified with insights drawn. First, we have presented the challenges in designing antennas for RFEH systems. This is followed by rectifier circuits and matching networks, and eventually a general frame work for designing of ambient RFEH systems is deduced.

Critical Events of Fog Attenuation Using Visibility Data in Lahore, Pakistan.

Free-space optics (FSO) communication system is mature, unique and promising technology which is used in various countries to meet high data rate demand and last mile connectivity. FSO link has a capacity to be utilized as a primary communication links by replacing RF communication systems because of its advantages of unregulated bandwidth, broader spectrum of frequency at low power consumption. Now a days researchers has great interest in this technology because of several features and benefits of larger bandwidth, less power consumption, low installations cost, simple to install, no congestion in spectrum, secure and reliable communication without issues of right of way. In free space optical communication, environment layer is used for signal transmission which can be effected from severe weather conditions like smog, dust, smoke, rain and fog etc. In all these severe weather environments, winter fog is one of the main problem because of it offers high optical attenuation on communication link. In this investigation the entire winter season has been observed. There are four fog events which attenuate the optical signal most. Optical attenuation is estimated using three famous fog prediction models like Al Naboulsi, Kim and at wavelengths of 850nm, 1350nm, and 1550 nm.