Low-cost Radio Frequency Research Articles

Highly oriented crystalline si on epitaxial Gd2O3/Si(111) substrate using low-cost Radio Frequency sputtering for Silicon on Insulator application

Silicon-on-Insulator (SOI) technology has been the center of attraction with the advancement in Radio Frequency (RF) technology and the advent of Internet-of-Things due to its low-power operation with reduced parasitic and short-channel effects. However, the state-of-the-art smart-cut method used for the SOI wafer is costly. Alternatively, the notion of using the Si channel layer on epitaxial rare-earth oxide has been proposed. In literature, the existing techniques used to achieve the same, such as Molecular beam Epitaxy or reduced-pressure chemical vapor deposition technique, are either costly or non-high-volume manufacturable. In this context, we propose a method to fabricate the highly oriented crystalline Si(111) channel layer (Top-Si) on an epitaxial Gd2O3/Si(111) virtual substrate (SOXI) utilizing the solid phase epitaxy using the high-volume manufacturing friendly (HVM), low-cost RF magnetron sputtering technique. First, we have shown the multicrystalline Si and epitaxial Gd2O3 layer grown on Si(111) substrate, as confirmed using high-resolution X-ray diffraction (HRXRD) and Transmission Electron Microscopy (TEM). Second, we investigated the impact of rapid thermal annealing at 850 °C on the heterostructure using HRXRD and TEM. It is observed that the high-temperature annealing transforms the Top-Si layer into the highly oriented crystalline Si(111) layer by fusing smaller grains towards larger grains. Hence, we demonstrate a low-cost, HVM-friendly technique for the fabrication of SOXI wafers.

SE Analysis and GEE Optimization of Hardware-Impaired Multi-Cell Massive MIMO Systems With Rician Fading and Phase Shifts

We consider a practical hardware-impaired multi-cell massive multi-input multi-output (mMIMO) system with spatially-correlated Rician fading channels, whose line-of-sight component experiences a random phase shift. The multi-cell mMIMO system employs two-layer large-scale fading decoding (LSFD) to mitigate the interference due to pilot contamination. We consider a dynamic analog-to-digital converter (ADC) architecture at the base stations (BS), which enables us to independently vary the resolution of ADC connected to its each antenna, and thus properly choose them to achieve a high spectral efficiency (SE). Both BS and user equipments (UEs) are also equipped with low cost radio frequency chains, which introduce additional hardware impairments. We first derive a closed-form SE expression for this system, and then optimize the UEs uplink data power and LSFD vectors to maximize the global energy efficiency metric. The proposed optimization, which is practically implementable due to its closed-form updates, is derived by combining the quadratic and Dinkelbach transforms, and generalized Rayleigh quotient. We investigate the ADC resolution and hardware impairments values for which LSFD is highly effective, and the values for which its effectiveness reduces.

RFID Authentication System Based on User Biometric Information

Traditional authentication technologies usually perform identity authentication based on user information verification (e.g., entering the password) or biometric information (e.g., fingerprints). However, there are security risks when applying only these authentication methods. For example, if the password is compromised, it is unlikely to determine whether the user entering the password is legitimate. In this paper, we subdivide biometric information into physiological and behavioral information, and we propose a novel user authentication system, RF-Ubia, which utilizes the low-cost radio frequency identification (RFID) technology to capture unique biological or behavioral information rooted in the user and can be used in two schemes for user authentication. Consisting of an array of nine passive tags and a commercial RFID reader, RF-Ubia provides double assurance for security of identity authentication by combining user information and biometric characteristics. It first verifies the user’s password, and then identifies the biometric characteristics of the legitimate user. Due to the coupling effect among tags, any change in tag signal caused by the user’s touch will affect other tag signals at the same time. Since each user has different fingertip impedance, their touch will cause unique tag signal changes. Therefore, by combining biometric information, the tag array will uniquely identify users. The evaluation results show that RF-Ubia achieves excellent authentication performance with an average recognition rate of 93.8%.

A Neuro-Space Mapping Method for Harmonic Interference Prediction of SOIFET Radio Frequency Switches

With the rapid development of wireless communication, the requirements of high-integration and low-cost radio frequency (RF) front-end modules in mobile phones result in more usage of silicon-on-insulator field effect transistors (SOIFETs) for the manufacturing of RF switches. However, the nonlinear behavior of SOIFET switches in <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">off</small> -state always produces unwanted harmonics distortion interference when they are excited by a large signal. In this article, we simplify the well-known physics-based surface potential model to an interelectrode nonlinear capacitance (INC) model since it adequately describes the harmonic effects produced by the transistor. The INC model, referred to as the coarse model, cannot match the behavior of the real switch, since many parameters of the switch cannot be accurately determined. This article proposes a novel dynamic neuro-space mapping network model, referred to as the fine model, to optimize the INC model. The proposed model takes advantage of the high accuracy of the fine model and the fast speed of the coarse model. Ultimately, the proposed method can accurately predict the harmonics interference for SOIFET switches in the complex RF front-end environment and provides an intuitive guideline under the design stage to prevent EMI problems.

SDR Pathfinder for Understanding Transient and Noise-Level Interference in the Karoo (SPUTNIK)

In this work, the SDR Pathfinder for Understanding Transient and Noise-level Interference in the Karoo (SPUTNIK) is presented. We describe how a low-cost radio frequency interference (RFI) monitoring system, using solely consumer-off-the-shelf (COTS) components, directly contributes to the analysis efforts of a precision 21[Formula: see text]cm cosmology instrument. A SPUTNIK system overview is provided, as well as a generalized software-defined radio (SDR) internal calibration technique to achieve wideband, [Formula: see text][Formula: see text]dBm-level accuracy and a measured dynamic range of [Formula: see text][Formula: see text]dB.

ARMOR: An Anti-Counterfeit Security Mechanism for Low Cost Radio Frequency Identification Systems

Counterfeited products are costing the global economy hundreds of billions of dollars annually. Radio frequency identification(RFID) technology provides a promising solution for this problem, wherein each product is fitted with a secure tag, which is difficult to forge. However, RFID technology is faced with numerous security threats, for example, if the communication link between the reader and the tag is compromised, then it will be possible for a malicious adversary to obtain the private data stored on the device. Tag cloning attacks have also been demonstrated to be feasible, which severely undermines the capabilities of the RFID technology to protect against counterfeiting. One solution to this problem is the use of authentication protocol; however, existing schemes do not support mutual authentication and are still vulnerable to tag cloning attacks. In this article, a new security mechanism is proposed, which consists of a lightweight three-flights mutual authentication protocol and an anti-counterfeit tag design. The proposed solution is based on combining the Rabin public-key encryption scheme with physically unclonable functions (PUF) technology. The security of the proposed protocol is systematically analysed and compared with existing schemes. The implementation cost of the proposed security primitives, assuming the 1024-bit public key, is 10139 GEs, which is suitable for low-cost RFID tags. Our results show that the proposed design is up-to 50 percent more area-efficient compared to systems based on Elliptic Curve Cryptography (ECC).

Sitsen: Passive sitting posture sensing based on wireless devices

Physical health diseases caused by wrong sitting postures are becoming increasingly serious and widespread, especially for sedentary students and workers. Existing video-based approaches and sensor-based approaches can achieve high accuracy, while they have limitations like breaching privacy and relying on specific sensor devices. In this work, we propose Sitsen, a non-contact wireless-based sitting posture recognition system, just using radio frequency signals alone, which neither compromises the privacy nor requires using various specific sensors. We demonstrate that Sitsen can successfully recognize five habitual sitting postures with just one lightweight and low-cost radio frequency identification tag. The intuition is that different postures induce different phase variations. Due to the received phase readings are corrupted by the environmental noise and hardware imperfection, we employ series of signal processing schemes to obtain clean phase readings. Using the sliding window approach to extract effective features of the measured phase sequences and employing an appropriate machine learning algorithm, Sitsen can achieve robust and high performance. Extensive experiments are conducted in an office with 10 volunteers. The result shows that our system can recognize different sitting postures with an average accuracy of 97.02%.

Hardware-Impaired Rician-Faded Massive MIMO FD Relay: Analysis and Optimization

We consider two-way multi-pair full-duplex (FD) massive multi-input-multi-output (mMIMO) relaying, where multiple FD user-pairs exchange information via a shared FD relay. We derive a closed-form spectral efficiency (SE) lower bound by considering i) dynamic analog-to-digital converter (ADC) and digital-to-analog converter (DAC) architecture at the relay, where each antenna is connected to a different resolution ADC/DAC; and ii) low cost radio frequency (RF) chains at the relay and users. The dynamic ADC/DAC architecture allows us to judiciously choose ADC/DAC resolution to achieve high SE with low power consumption. We unlike, the most existing mMIMO relaying works, consider a correlated Rician fading channel, which captures realistic line-of-sight (LoS) signal propagation and spatial correlation between closely-packed relay antennas. We maximize the derived SE lower bound by first proposing its valid surrogate function, and then by using minorization-maximization approach. We investigate the impact of ADC/DAC and RF impairments, and show that the proposed optimization allows reduction in ADC/DAC resolution without compromising the SE.

An Unmatched Radio Frequency Chain for Low-Field Magnetic Resonance Imaging.

Magnetic Resonance Imaging (MRI) is a safe and versatile diagnostic tool for intracranial imaging, however it is also one of the most expensive and specialized making it scarce in low- to middle-income countries (LMIC). The affordability and portability of low-field MRI offers the potential for increased access to brain imaging for diseases like Hydrocephalus in LMIC. In this tutorial style work, we show the design of a low powered and low cost radio frequency chain of electronics to be paired with a previously reported prepolarized low-field MRI for childhood hydrocephalus imaging in sub-Saharan Africa where the incidence of this condition is high. Since the Larmor frequency for this system is as low as 180 kHz, we are able to minimize the impedance of the transmit coil to 5 ohms rather than match to 50 ohms as is traditionally the case. This reduces transmit power consumption by a factor of 10. We also show the use of inexpensive and commonly available animal enclosure fencing (“chicken wire”) as a shield material at this frequency and compare to more traditional shield designs. These preliminary results show that highly portable and affordable low-field MRI systems could provide image resolution and signal-to-noise sufficient for planning hydrocephalus treatment in areas of the world with substantial resource limitations. Employment of these technologies in sub-Saharan Africa offers a cost-effective, sustainable approach to neurological diagnosis and treatment planning in this disease burdened region.

RF Impairments in Wireless Transceivers: Phase Noise, CFO, and IQ Imbalance – A Survey

Wireless transceivers for mass-market applications must be cost effective. We may achieve this goal by deploying non-ideal low-cost radio frequency (RF) analog components. However, their imperfections may result in RF impairments, including phase noise (PN), carrier frequency offset (CFO), and in-phase (I) and quadrature-phase (Q) imbalance. These impairments introduce in-band and out-of-band interference terms and degrade the performance of wireless systems. In this survey, we present RF-impairment signal models and discuss their impacts. Moreover, we review RF-impairment estimation and compensation in single-carrier (SC) and multicarrier systems, especially orthogonal frequency division multiplexing (OFDM). Furthermore, we discuss the effects of the RF impairments in already-established wireless technologies, e.g., multiple-input multiple-output (MIMO), massive MIMO, full-duplex, and millimeter-wave communications and review existing estimation and compensation algorithms. Finally, future research directions investigate the RF impairments in emerging technologies, including cell-free massive MIMO communications, non-orthogonal multicarrier systems, non-orthogonal multiple access (NOMA), ambient backscatter communications, and intelligent reflecting surface (IRS)-assisted communications. Furthermore, we discuss artificial intelligence (AI) approaches for developing estimation and compensation algorithms for RF impairments.

A novel method for utilizing RF information from IEEE 802.11 frames in Software Defined Networks

Wireless security research using Radio Frequency (RF) data is complex and costly, often requiring expensive equipment and extensive offline processing. To make wireless research more accessible, we have integrated RF signal features with the existing IEEE 802.11 frame layer 2/3 data using the Software Defined Networking (SDN) paradigm. Combining low-cost RF hardware, a novel SDN processing method, and unique RF processing architecture has resulted in a framework that enables advanced wireless security and control research at a significantly lower cost. The method for enabling such functionality consist of the following stages:•During the demodulation process, extract Carrier Frequency Offset (CFO) and Pilot Sub-Carrier Offset from the Frequency Offset Correction section, in addition to the Vector Magnitude from the equalization section.•Append the new RF information to the wireless frame buffer and pass it to the SDR kernel driver module to further process before transferring them to a P4 application via a single API instantiation.•Compile a custom P4 application that combines the new RF features alongside higher OSI layer features to perform advanced networking, security, or control plane operations.

Preclinical development of a novel coaptive vessel sealing device for liver resection

Presenter: Lucas Thornblade MD, MPH | City of Hope Cancer Center Background: The safety of liver resection has increased dramatically, in great part due to advances in devices for parenchymal transection. We identified five limitations to existing vessel sealer technology: bulky jaws, short seal-zones, propensity for tissue shearing, tissue-char fouling, and the cost of fully disposable units. We sought to develop an affordable sealing device platform that could safely reduce the time required for open liver resection. Methods: We partnered with engineers to develop a radiofrequency (RF) powered coaptive sealing device with five features unique among existing vessel sealers. First, the device achieves a 6.5cm long seal zone, allowing faster parenchymal transection (Figure panel A). Second, lower-profile jaws reduce tissue tearing upon insertion into liver parenchyma. Third a spring-loaded hinge provides parallel apposition and reduces tissue shear. Fourth, the device applies saline to the sealing surface which reduces fouling upon repeated firings. And lastly, the reusable handle and low-cost RF generator facilitates an affordable alternative to conventional vessel sealers. The device was tested on 12 partial hepatectomies in six live canine models in compliance with 510(k) processes in an accredited large animal lab. Necropsy was performed 7-9 days postoperatively by a veterinary pathologist. Results: All subjects tolerated liver resection with minimal blood loss ( < 20cc). Figure panel B demonstrates a completed partial hepatectomy of the canine liver. Transaminases peaked by postoperative day four (mean ALT 194 U/L). At necropsy, no hematoma or bile collections were found. Novel design elements were registered with the U.S. Patent Office. Conclusion: By careful study of the limitations of existing designs, surgeons have a unique opportunity to impact changes in future surgical technology. Further work includes design refinement, regulatory overview for testing in humans, and partnership with industry.

Characterization of Shorted Dipole Antennas for Low-Cost RFID Reader Applications

This article presents a comprehensive study on shorted dipole antennas aiming for low-cost radio frequency identification (RFID) reader applications. Starting from a low-profile shorted bowtie dipole antenna, it is found that by varying the shorting wall position, three different types of resonant antennas could be realized with different radiation features. A low-profile planar inverted F antenna (PIFA) -type dipole is obtained by moving the shorting wall toward the feeding, which exhibits a low resonance frequency without obvious back lobe radiation or sidelobes. When the shorting wall is placed in the middle of the radiating patch, a mushroom-type dipole antenna can be built. A zeroth-order mode is also observed. This structure differs from the magnetoelectric dipole due to a low-profile structure. Placing the wall toward the end of the dipole arm leads to a loop-type antenna with a broader beam and a reduced gain. It also shifts the resonance toward the higher frequency. Based on the PIFA- and mushroom-type structures, two circularly polarized antennas with crossed shorted dipoles are designed and investigated carefully. Finally, two optimized, compact, and low-cost RFID reader antennas based on simple metal stamping process and screws are designed, fabricated, and tested, showing an excellent RF reading range. This study demonstrates that for the shorted dipole antennas, miniaturization and bandwidth control can be achieved simultaneously. Particularly, for higher gain and smaller size, the shorting wall should be placed close to the feeding to suppress the loop mode. For omnidirectional radiation, the loop mode should be enhanced by moving the shorting wall close to the end of the dipole arm.

All transparent high-performance solar-blind n-ITO/p-NiO/n-ZnO ultraviolet heterojunction bipolar phototransistor

All transparent high-performance solar-blind n-ITO/p-NiO/n-ZnO ultraviolet heterojunction bipolar phototransistors (HBPTs) were fabricated using a low-cost radio frequency magnetron sputtering system. In the HBPT structure, ITO, NiO, and ZnO were employed as the emitter, base, and collector, respectively. The applied voltage is across the emitter and collector, and the base is floating. The photocurrent increases with the collector–emitter voltage (VCE). The prepared HBPTs presented the highest optical gain of 7.4 × 104 and a responsivity of 1.67 × 104 A/W, at VCE = 4 V for the 280-nm illumination wavelength. As VCE exceeds 4 V, the optical gain and responsivity decrease owing to the punch-through effect. The prepared HBPTs have an ultraviolet (UV)/visible rejection ratio of more than three orders, allowing their use in practical applications as UV detectors for weak UV signals.

Framework for The Development of a Low-Cost Radio Frequency Identification (RFID) Based-System for Supporting Vaccine Immunization and Uptake in a Developing Country

Framework for The Development of a Low-Cost Radio Frequency Identification (RFID) Based-System for Supporting Vaccine Immunization and Uptake in a Developing Country

Secure Outsourcing Algorithms for Composite Modular Exponentiation Based on Single Untrusted Cloud

AbstractModular exponentiation, as a fundamental operation used in many public-key cryptosystems, has always be considered to be very time-consuming. It is difficult for some devices with limited computation capability, such as mobile devices and low-cost radio frequency identification (RFID) tags, to perform large-scale modular exponentiations. In cryptosystems, one typical case of modular exponentiation is that the modulus is a composite number. For instance, in RSA algorithm, the modulus is the product of two distinct prime numbers. In this paper, we investigate how to securely and efficiently outsource composite modular exponentiations and put forward two secure outsourcing algorithms for composite modular exponentiations based on single untrusted cloud. The first algorithm, named MCExp, is designed for outsourcing single composite modular exponentiation, i.e. $u^a$ mod $N$. The second algorithm, named SMCExp, is designed for outsourcing simultaneous composite modular exponentiation, i.e. $\prod ^{n}_{i=1}u^{a_i}_{i}$ mod $N$. Different from algorithms based on two untrusted servers, the proposed algorithms are very practical because they avoid the strong assumption that there must exist two servers without collusion. The proposed algorithms not only protect the privacy of the exponent and the base simultaneously, but also enable users to verify the correctness of the result returned by the cloud with high probability. Compared with using the square-and-multiply algorithm, the user can achieve higher efficiency by using the proposed algorithms. Besides, we prove the security of our algorithms and conduct several experiments to demonstrate the efficiency of the proposed algorithms. Finally, we show that the proposed algorithms can be used to construct the secure outsourcing algorithms for Shamir’s identity-based signature and identity-based multi-signature.

Epitaxial growth of Cu2ZnSnS4 thin film on Si by radio frequency magnetron sputtering

Environmentally friendly and earth abundant Cu2ZnSnS4 (CZTS) based thin films are potential absorbers for next generation photovoltaics. Their optical properties provide the option to be used as upper cells for Si based tandem solar cells, together with a similar structure to Si, triggering interest in investigation of CZTS/Si tandem cells. However, epitaxially growing CZTS on Si can be challenging. Here, we heteroepitaxially grow tetragonal Cu2ZnSnS4 (CZTS) thin films on single crystalline cubic Si (111) wafers with a 4° miscut by simple and low-cost radio frequency magnetron sputtering from a single target. The CZTS film displays a mirror-like surface with a surface roughness of 8.46 nm. The absorption coefficients of the epitaxial CZTS are over 104 cm−1 at 1.5 eV and 1.0 × 105 cm−1 at 2.1 eV. The bandgap is 1.45 eV, and the photoluminescence lifetime is 7.04 ns. Our results demonstrate the potential of the epitaxial CZTS films fabricated by sputtering on the Si substrate for application in CZTS/Si based tandem solar cells.

RFID Enabled Framework for Substation Maintenance Management

Objectives: Effective substation maintenance management based on low cost and reliable Radio Frequency Identification (RFID) enabled implementation framework. Methods/Statistical Analysis: Economical operation of substation by minimizing the equipment maintenance cost is the prime concern for all the power distribution utilities. Number of maintenance management strategies has been developed for optimizing the substation equipment maintenance cost. Effectiveness of these optimized maintenance strategies lies on the actual implementation in the field. Currently equipment maintenance activities are carried out with off-line association with equipment. Also, equipment maintenance data is acquired and populated manually into host computer which is running maintenance cost optimization applications. Inherently manual process suffers from various drawbacks and results in poor maintenance management. RFID based technology along with embedded system is identified for making the above off-line process into an on-line process with data integrity. Findings: Present paper proposes a Radio Frequency Identification (RFID) enabled implementation framework to perform the maintenance with on-line association with equipment. This allows on-line access with the equipment and eliminates the manual process of acquiring data from equipment at the substation level. Also, ensures the on-line update of pre-maintenance and postmaintenance information of equipment in the Computerised Maintenance Management System (CMMS). Conventional RFID readers which are based on multi-purpose hand-held computers are driven by high level operating systems and programming languages. Due to high level system software on handheld readers, the network latency increases and data refresh rate decreases. This paper proposes a low cost microcontroller based RFID reader with up-stream data interface using low level network programming to address the above issues. Host computer data interface is implemented using a TCP/IP protocol which assures the data integrity. The low level programming at the host computer for network communication minimizes the network latency in the data transfer and improves the data refresh rate. Maintenance process with RFID framework is designed and explained. Application/Improvements: Maintenance management strategies can be implemented effectively using the proposed RFID enabled framework with customized RLU along with low level network interface to CMMS. Present implementation based on Ethernet interface over TCP/IP can be extended seamlessly for wireless (Wi-Fi) as well. Keywords: JSP, Maintenance, RFID, Substation, TCP/IP

Radio frequency identification to measure the duration of machine-paced assembly tasks: Agreement with self-reported task duration and application in variance components analyses of upper arm postures and movements recorded over multiple days

Technical advances in inertial measurement units (IMUs) with data logging functionality have enabled multi-day collection of fullshift upper arm postures and movements. Such data are useful for characterizing job-level exposures and, when coupled with task-level information, can inform interventions to mitigate high-exposure tasks. Previously reported methods for capturing task-level information, however, were limited primarily to self-report diaries or direct observation. In this study of machine-paced manufacturing workers (n=6), a low-cost radio frequency identification (RFID) system was used to collect information about when, and for how long, specific assembly tasks were performed during up to 14 consecutive work shifts (76 total work shifts across the six participants). The RFID data were compared to information collected with a self-report diary using Bland-Altman analyses. In addition, the RFID data were paired with IMU data to identify task-level exposures from within full-shift recordings of upper arm postures and movements. These data were then used to estimate the relative contributions of between- and within-worker sources of variance to overall variance in posture and movement summary measures using hierarchical random-effects analysis of variance (ANOVA) techniques. Average estimates of daily task duration based on RFID data were comparable to estimates obtained by self-report (mean bias < ±1 minute) but with substantial variability (limits of agreement > ±100 minutes). In addition, the ANOVA models containing task-level information suggested a substantial amount of the overall exposure variance was attributed to repeated observations of the same task within a work day. These findings (i) suggest that while the RFID system used in this study performed adequately, further refinement, validation, and/or alternative strategies may be needed and (ii) underscore the importance of repeated full-shift and task-based measurement approaches in characterizing physical exposures, even in machine-paced environments.

Non-Uniform Wavelet Sampling for RF Analog-to-Information Conversion

Feature extraction, such as spectral occupancy, interferer energy and type, or direction-of-arrival, from wideband radio-frequency (RF) signals finds use in a growing number of applications as it enhances RF transceivers with cognitive abilities and enables parameter tuning of traditional RF chains. In power and cost limited applications, e.g., for sensor nodes in the Internet of Things, wideband RF feature extraction with conventional, Nyquist-rate analog-to-digital converters is infeasible. However, the structure of many RF features (such as signal sparsity) enables the use of compressive sensing (CS) techniques that acquire such signals at sub-Nyquist rates; while such CS-based analog-to-information (A2I) converters have the potential to enable low-cost and energy-efficient wideband RF sensing, they suffer from a variety of real-world limitations, such as noise folding, low sensitivity, aliasing, and limited flexibility. This paper proposes a novel CS-based A2I architecture called non-uniform wavelet sampling. Our solution extracts a carefully-selected subset of wavelet coefficients directly in the RF domain, which mitigates the main issues of existing A2I converter architectures. For multi-band RF signals, we propose a specialized variant called non-uniform wavelet bandpass sampling (NUWBS), which further improves sensitivity and reduces hardware complexity by leveraging the multi-band signal structure. We use simulations to demonstrate that NUWBS approaches the theoretical performance limits of $\ell_{1}$ -norm-based sparse signal recovery. We investigate hardware-design aspects and show ASIC measurement results for the wavelet generation stage, which highlight the efficacy of NUWBS for a broad range of RF feature extraction tasks in cost- and power-limited applications.