Radio Frequency Module Research Articles

All-optical radio-frequency modulation of Anderson-localized modes

All-optical modulation of light relies on exploiting intrinsic material nonlinearities. However, this optical control is rather challenging due to the weak dependence of the refractive index and absorption coefficients on the concentration of free carriers in standard semiconductors. To overcome this limitation, resonant structures with high spatial and spectral confinement are carefully designed to enhance the stored electromagnetic energy, thereby requiring lower excitation power to achieve significant nonlinear effects. Small mode-volume and high quality (Q)-factor cavities also offer an efficient coherent control of the light field and the targeted optical properties. Here, we report on optical resonances reaching Q - 10^5 induced by disorder on novel photonic/phononic crystal waveguides. At relatively low excitation powers (below 1 mW), these cavities exhibit nonlinear effects leading to periodic (up to - 35 MHz) oscillations of their resonant wavelength. Our system represents a test-bed to study the interplay between structural complexity and material nonlinearities and their impact on localization phenomena and introduces a novel functionality to the toolset of disordered photonics.

Design and Implementation of a Compact 3-D Stacked RF Front-End Module for Micro Base Station

In the current 4G Long Term Evolution and the incoming 5G mobile communication technology, as the number of radio frequency (RF) devices in the RF front-end module is increasing fast, miniaturization is essential and significant. The 3-D RF system-in-package (SiP) technology is an excellent miniaturization solution. In this paper, a 700–2900-MHz 3-D stacked RF module with the size of 23 mm $\times$ 23 mm $\times$ 3.3 mm has been designed and implemented, which is used for a micro base station. It is more compact than other reported 3-D RF SiP products used for micro base stations. The 3-D RF module integrates four bare dies, one quad flat no-lead packaged chip, and more than 200 passive devices. Considering the electromagnetic isolation requirement, mechanical performance, and effective interconnection, the detailed structure design is presented in this paper. Simulations are performed for the electrical characterization and the thermal performance evaluation of the stacked module. The simulation results show that the insertion loss ( $S_{21}$ ) and return loss ( $S_{11}$ ) of the RF signal transmission lines are controlled below 0.42 dB and over 15 dB within 3 GHz, respectively. The electromagnetic isolation between different RF and/or intermediate frequency signal transmission lines is no less than 65 dB within 3 GHz. In thermal management simulation, the highest junction temperature of the chips in the 3-D structure is below 94 °C at the severe condition (50 °C ambient temperature and nature air convection). Finally, the assembly flow is presented, and the test results indicate the good electrical performance of the 3-D RF module.

A self-powered radio frequency (RF) transmission system based on the combination of triboelectric nanogenerator (TENG) and piezoelectric element for disaster rescue/relief

We present a self-powered, wireless radio frequency (RF) transmitter based on the combination of triboelectric nanogenerator (TENG) and piezoelectric element, which can send coded signal remotely to a receiver when the sensor is triggered. The piezoelectric element is connected to an energy management module (EMM) which supplies regulated power suitable for powering the RF module; the triboelectric nanogenerators (TENGs) act as sensors, which control the code being transmitted by the RF module. In addition, a switch is embedded in TENG to control the power supply from EMM to the RF module; only at the moment of TENG being pressed, the power stored in EMM (ultimately from the piezoelectric element) is supplied to the RF module, and the intended RF signal is transmitted. The RF signal is then received by the receiver and the transmitted code is deciphered and then visualised by a Labview program on PC. Four TENGs are used as sensing elements of mechanical pressing, and each triggers a different command to be transmitted. It is believed that, with such novel combination of the piezoelectric element for powering and TENG for sensing, this is a novel application of TENG and piezoelectric element to transmit coded RF signal with regulated power supply suitable for many modern electronics. The designed self-powered RF transmission system and the general system structure have potentially widespread applications in wireless communication and sensing, especially in applications where power or electricity is disrupted/unavailable, such as disaster rescue/relief, e.g. entrapment in buildings and natural environments due to lift malfunction, earthquake, landslide, debris flow, and blizzards, etc.

An Integrated RF Power Delivery and Plasma Micro-Thruster System for Nano-Satellites

Progress in satellite technologies is ongoing and eventually finds applications back on Earth. Electric propulsion systems have been proven effective on large scale satellites (NASA DAWN) with better propellant efficiency than chemical or cold gas propulsion, and if miniaturized can be promising for long term operation of nano-satellites (e.g.CubeSats) in low Earth orbit or in deep space (NASA MarCO). However, the power supplies often used to power these electric thrusters, particularly those involving radiofrequency (RF) plasma, typically comprise power inefficient linear mode RF power amplifiers (e.g. class AB). These are simple systems designed to operate reliably under a wide range of loads for versatility, but they suffer low power efficiencies when operating at conditions significantly different from the nominal operating point. The required bulky and heavy thermal management components deem these electric propulsion systems impossible to fit on board nano-satellites. Here we present a compact and efficient switched mode dc-RF power inverter integrated with an electro-thermal plasma micro-thruster for nano-satellite (e.g.Cubesats) propulsion. The integrated system can serve as side panels and structural support of CubeSats, saving precious on-board volume for propellant and/or payloads. A complete assembly has been operationally tested in a space simulation system. This development opens a route for a new generation of power supplies applicable to the space sector, the microelectronics industry as well as the field of bioengineering.

Integrated Cooperative Ambient Power Harvester Collecting Ubiquitous Radio Frequency and Kinetic Energy

An integrated cooperative harvester capable of collecting both electromagnetic [(principally radio frequency (RF)] and kinetic energy simultaneously is proposed and studied in this paper. One single substrate board is demonstrated to accommodate and integrate an electromagnetic kinetic generator, an F-shaped antenna, and a rectifying circuit, having a compact credit-card size. Cooperative harvesting mode enables a significant enhancement of the diode’s power conversion efficiency (PCE) and also greatly strengthening the resilience of harvester at the same time. Measured results suggest that SMS7630 and HSMS-2850-based cooperative harvesters can increase dc output power by 50% to around 100% when both injecting power sources exhibit below −37 dBm with reference to the total added amount of dc power harvested directly from separate RF and kinetic excitation modes. A closed-form method is proposed and used to predict the enhanced efficiency performance of the cooperative harvester within a low power range of interest (from −50 to −30 dBm). Our analysis highlights the roles of the diode’s nonlinear junction resistance and capacitance. Good agreements are observed when comparing the analysis results with harmonic balance simulations by ADS. Furthermore, this method is carefully verified by measured results of two different diode-based harvesters. Measured dc output power rectified from cooperative harvesting mode is reported to be 1.16 and 1.97 times larger with SMS7630 and HSMS-2850, respectively, when both power sources are −40 dBm, compared to the conventional single RF harvesting mode. The proposed cooperative harvester with its strong resilience is highly suitable for ambient power harvesting in an ever-changing environment.

The Effect of a Single 30-Min Long Term Evolution Mobile Phone-Like Exposure on Thermal Pain Threshold of Young Healthy Volunteers.

Although the majority of mobile phone (MP) users do not attribute adverse effects on health or well-being to MP-emitted radiofrequency (RF) electromagnetic fields (EMFs), the exponential increase in the number of RF devices necessitates continuing research aimed at the objective investigation of such concerns. Here we investigated the effects of acute exposure from Long Term Evolution (LTE) MP EMFs on thermal pain threshold in healthy young adults. We use a protocol that was validated in a previous study in a capsaicin-induced hyperalgesia model and was also successfully used to show that exposure from an RF source mimicking a Universal Mobile Telecommunications System (UMTS) MP led to mildly stronger desensitization to repeated noxious thermal stimulation relative to the sham condition. Using the same experimental design, we did not find any effects of LTE exposure on thermal pain threshold. The present results, contrary to previous evidence obtained with the UMTS modulation, are likely to originate from placebo/nocebo effects and are unrelated to the brief acute LTE EMF exposure itself. The fact that this is dissimilar to our previous results on UMTS exposure implies that RF modulations might differentially affect pain perception and points to the necessity of further research on the topic.

Adjustment of genetic algorithm parameters for solving the problem of topology optimization of the sensory network

The paper is devoted to the optimal placement of devices within a wireless sensor network. Modern requirements to ensure public safety in buildings with a complex structure imply the existence of systems that can detect and position emergency situation, inform rescue and tenants about the status and help them to either evacuate or eliminate the danger. Nowadays the main approach to create indoor emergency system is based on wireless sensor network. The network is built with a big number of usually battery-operating devices, each consists of a sensors set for hazard detection, and radio frequency module for communication. To evaluate the state of indoor environment different sensors can be used, such as temperature, humidity, light, flame, smoke, gas, etc. The problem of optimizing the network topology as a covering problem is formulated. A set of points in the area that is not covered by circles, a set of points belonging to the region and the intersection of two or more circles of coverage, set of points that do not belong to the area need to be minimized. To ensure fault tolerance of the wireless sensor network, it is necessary to allow the connection of each sensor with at least two routers, in case one of the routers is accidentally switched off, and also it is necessary to ensure connection of the router with at least one router. To take into account these additional conditions, the method of penalty functions is used. The genetic algorithm for solving the problem is used. The main genetic operators are adapted to the problem of designing the topology of wireless sensor networks. A computa-tional experiment was carried out, during which the optimal population size was estab-lished; the procedure of homogeneous crossing, procedure of tournament selection is chosen; procedure of homogeneous mutation. As a criterion for stopping the genetic algorithm, the stagnation of the results on the iterations of the algorithm is chosen.

Wireless prototype for monitoring vehicular parking lots

This paper describes the development and implementation of a prototype that monitors the availability of space in a sheltered parking lot, establishing quality of service (QoS) parameters. Consequently, radiofrequency modules were used to transmit the information acquired through a network of adapted sensors. The samples taken from the status (available, occupied) are displayed, as well as the data acquired and sent to a web server where they are stored and displayed in a mobile application and the end user can check the status of the parking space, as well as its parking fee, location and structure. Each sensor has an accuracy of 3 mm ranging between 3 cm and 4 m, while the radio frequency transmission has a power accuracy of 4 dB to insure adequate performance.

OpSecure: A Secure Unidirectional Optical Channel for Implantable Medical Devices

Implantable medical devices (IMDs) are opening up new opportunities for holistic healthcare by enabling continuous monitoring and treatment of various medical conditions, leading to an ever-improving quality of life for patients. Integration of radio frequency (RF) modules in IMDs has provided wireless connectivity and facilitated access to on-device data and post-deployment tuning of essential therapy. However, this has also made IMDs susceptible to various security attacks. Several lightweight encryption mechanisms have been developed to prevent well-known attacks, e.g., integrity attacks that send malicious commands to the device, on IMDs. However, lack of a secure key exchange protocol (that enables the exchange of the encryption key while maintaining its confidentiality) and the immaturity of already-in-use wakeup protocols (that are used to turn on the RF module before an authorized data transmission) are two fundamental challenges that must be addressed to ensure the security of wireless-enabled IMDs. In this paper, we introduce OpSecure, an optical secure communication channel between an IMD and an external device, e.g., a smartphone. OpSecure enables an intrinsically user-perceptible unidirectional data transmission, suitable for physically-secure communication with minimal size and energy overheads. Based on OpSecure, we design and implement two protocols: (i) a low-power wakeup protocol that is resilient against remote battery-draining attacks, and (ii) a secure key exchange protocol to share the encryption key between the IMD and the external device. We evaluate the two protocols using a human body model.

Reconfigurable remote radio head design and implementation for super base station applications

This paper proposes a reconfigurable remote radio head (RRH) software and hardware architecture and presents the results of its implementation. The implemented RRH has been designed for a centralized architecture super base station that facilitates the integration of 2G, 3G, and 4G ground base stations and geosynchronous equatorial orbit (GEO) satellite gateway stations. The reconfigurable RRH is a primary aspect of the system. By modifying the programmable software configuration from the perspective of software-defined radio, the RRH can support multiple frequency allocations. The RRH is composed of radio frequency (RF) modules, intermediate frequency (IF) modules, and some of the physical layer functions. The development of a reconfigurable IF module is emphasized. A filter-bank multiplexing technique has been employed for the IF module, which reduces the use of hardware resources. To this end, we experimentally evaluated the main key performance indicators (KPIs) of the RRH. The experimental results demonstrate that the proposed design attains the goal of reducing hardware costs and improving system flexibility and stability.

Dual-feedback mid-infrared cavity-enhanced absorption spectroscopy for H2CO detection using a radio-frequency electrically-modulated interband cascade laser.

A mid-infrared cavity-enhanced sensor system was demonstrated for the detection of formaldehyde (H2CO) using a continuous-wave (cw) interband cascade laser (ICL) centered at 3599 nm. A compact Fabry-Perot (F-P) cavity with a physical size of 38 × 52 × 76 mm3 was developed consisting of two concave mirrors with a radius of curvature of 80 mm and a reflectivity of 99.8% at 3.6 μm. Different from the widely reported electro-optical (EO) external modulation based Pound-Drever-Hall (PDH) locking technique, a radio-frequency electrical internal modulation based PDH technique was used for locking the laser mode to the cavity mode. A dual-feedback control on the laser current and on the piezo transducer (PZT) displacement was utilized for further stabilizing mode locking. A 20 m effective optical path length was achieved with a cavity length of 2 cm and a finesse of 1572. The effectiveness and sensitivity of the sensor system were demonstrated by targeting an absorption line at 2778.5 cm-1 for H2CO measurements. A linear relation between the cavity transmitted signal amplitude and the H2CO concentration was obtained within the range of 0-5 ppm. A 1σ detection limit of 25 parts-per-billion (ppb) was achieved with an averaging time of 1 s based on Allan-Werle variance analysis. The reported dual-feedback RF modulation based PDH technique led to a method for gas detection using a similar experimental setup and measurement scheme.

Multilayered Electromagnetic Interference Shielding Structures for Suppressing Magnetic Field Coupling

Control of electromagnetic interference (EMI) represents a major challenge for emerging consumer electronics, the Internet of Things, automotive electronics, and wireless communication systems. This paper discusses innovative EMI shielding materials and structures that offer higher shielding effectiveness compared with copper. To create high shielding effectiveness in the frequency range of 1 MHz to 100 MHz, multilayered shielding topologies with electrically conductive and nanomagnetic materials were modeled, designed, fabricated, and characterized. In addition, suppression of out-of-plane and in-plane magnetic-field coupling noise with these structures is compared with that of traditional single-layer copper or nickel–iron films. Compared with single-layered copper shields, multilayered structures consisting of copper, nickel–iron, and titanium showed a 3.9 times increase in shielding effectiveness in suppressing out-of-plane or vertically coupled noise and 1.3 times increase in lateral coupling. The superiority of multilayered thin-film shields over conventional shielding enables greater design flexibility, higher shielding effectiveness, and further miniaturization of emerging radiofrequency (RF) and power modules.

Thin film lithium niobate electro-optic modulator with terahertz operating bandwidth.

We present a thin film crystal ion sliced (CIS) LiNbO3 phase modulator that demonstrates an unprecedented measured electro-optic (EO) response up to 500 GHz. Shallow rib waveguides are utilized for guiding a single transverse electric (TE) optical mode, and Au coplanar waveguides (CPWs) support the modulating radio frequency (RF) mode. Precise index matching between the co-propagating RF and optical modes is responsible for the device's broadband response, which is estimated to extend even beyond 500 GHz. Matching the velocities of these co-propagating RF and optical modes is realized by cladding the modulator's interaction region in a thin UV15 polymer layer, which increases the RF modal index. The fabricated modulator possesses a tightly confined optical mode, which lends itself to a strong interaction between the modulating RF field and the guided optical carrier; resulting in a measured DC half-wave voltage of 3.8 V·cm-1. The design, fabrication, and characterization of our broadband modulator is presented in this work.

Depth Matters: The Use of Radiofrequency for the Treatment of Gynecologic Conditions [40G

INTRODUCTION: The use of radiofrequency (RF) energy administration to the vaginal canal has been increasing, but questions regarding safety and mechanism of action remain. The type of RF, mode of administration and protocol will impact treatment outcomes. Submucosa cellular changes require that energy penetrate deep into the tissue without causes damage to the mucosal tissue. Data indicate that cryogen-cooled monopolar radiofrequency (CMRF) treatment elicits changes such as fibroblast activation and neocollagenesis while being safe to patients METHODS: Ovine ex vivo and in vivo studies were performed to investigate the depth of penetration and safety of CMRF treatment. Ex vivo treatment was performed on isolated vaginal and peri-vaginal tissue at different regions of the vagina. Gross observations and histopathological analyses were performed. Tissue was isolated following RF treatment and analyzed for tissue effects. Outcome measures include temperature monitoring and histopathology to evaluate the extent of treatment, cellular changes and safety. RESULTS: Data indicate that there are a number of cellular changes in the submucosal layers of the vagina following elevated temperature of these tissues and that these modifications result in increased structural integrity and function. Such changes are likely responsible for clinical benefit reported. In addition, when an energy titration experiment was performed with ex vivo tissue, there were no adverse tissue effects observed. CONCLUSION: The type of RF energy and mode of delivery will have an impact on the tissue affected and the potential clinical benefit. CMRF energy affects the deeper connective tissue in the vaginal canal while protecting the mucosal tissue

(Invited) Toward Wireless Biosensing Using Transparent Graphene Electronics

We present a new type of self-powered, low- interference wireless sensors based on graphene circuits, which can have dual functions: chemical sensing at the molecular level and radio-frequency (RF) modulation. . We have designed two different types of circuits comprising back-gate graphene field-effect transistors (GFETs) and compared in detail their performance and implementation complexity. We have also proposed a reliable readout method based on the machine learning for extracting the mean value and the fluctuation of chemical doping levels in GFETs. We demonstrate that a fully passive, graphene-based harmonic (transponder) sensor can display a chemically sensitive frequency multiplication effect, which, when linked to a hybrid-fed small antenna, can realize an ultrasensitive, low-profile, light-weight, and potentially flexible RF sensor.

Design and Implementation of Smart Home Gateway Based on 433MHz Radio-Frequency Communication

Background: In view of the lack of centralized control of traditional home appliances, this paper implements an intelligent gateway based on the Linux embedded operating system as the software platform and the ARM9 processor S3C2440 as the hardware development platform to solve this problem. Methods: The intelligent gateway is equipped with Wi-Fi, CC1101, Ethernet card and other functional modules, and based on the 433MHz radio-frequency protocol stack and the Linux operating system kernel. We establish the platform of the remote control through the cloud server, so the users can log on the client to achieve smart home remote monitoring. Result: This paper introduces the hardware and software development process of intelligent gateway, which involves the realization of the 433MHz radio-frequency protocol stack, the software design of the 433MHz radio-frequency module, and the design and implementation of the smart home client and so on. Conclusion: The test results show that the intelligent gateway has the characteristics of low-cost, low-power consumption, high reliability. Keywords: Intelligent gateway, 433MHz radio-frequency communication, smart home, CC1101, Linux, S3C2440 cloud platform.

Homogeneous spectral broadening of pulsed terahertz quantum cascade lasers by radio frequency modulation.

The authors present an experimental investigation of radio frequency modulation on pulsed terahertz quantum cascade lasers (QCLs) emitting around 4.3 THz. The QCL chip used in this work is based on a resonant phonon design which is able to generate a 1.2 W peak power at 10 K from a 400-µm-wide and 4-mm-long laser with a single plasmon waveguide. To enhance the radio frequency modulation efficiency and significantly broaden the terahertz spectra, the QCLs are also processed into a double-metal waveguide geometry with a Silicon lens out-coupler to improve the far-field beam quality. The measured beam patterns of the double-metal QCL show a record low divergence of 2.6° in vertical direction and 2.4° in horizontal direction. Finally we perform the inter-mode beat note and terahertz spectra measurements for both single plasmon and double-metal QCLs working in pulsed mode. Since the double-metal waveguide is more suitable for microwave signal transmission, the radio frequency modulation shows stronger effects on the spectral broadening for the double-metal QCL. Although we are not able to achieve comb operation in this work for the pulsed lasers due to the large phase noise, the homogeneous spectral broadening resulted from the radio frequency modulation can be potentially used for spectroscopic applications.

Alarm device for locating people submerged beneath water based on the geomagnetic sensor

An alarm device consisting of data collection module, control module and radio frequency module for locating people submerged beneath water is investigated. By combining the magnetic field distribution information and acceleration sensor, the alarm device is able to simulate submerged person movement path in the data collection module. STC89C51 is selected as the main control chip in the control module for alarm switching, information encoding and control of radio frequency mode. A third-generation wireless transceiver chip nRF2401 is adopted in the radio frequency module, allowing data transmission in the international ISM frequency range. The implementation based on the geomagnetic sensor that is simple in design, boasts full functions and has excellent drowning detection sensitivity. Additional wireless emission coordinate capability will improve efficiency and shipwreck rescue and maritime navigation in the future.

Alarm device for locating people submerged beneath water based on the geomagnetic sensor

An alarm device consisting of data collection module, control module and radio frequency module for locating people submerged beneath water is investigated. By combining the magnetic field distribution information and acceleration sensor, the alarm device is able to simulate submerged person movement path in the data collection module. STC89C51 is selected as the main control chip in the control module for alarm switching, information encoding and control of radio frequency mode. A third-generation wireless transceiver chip nRF2401 is adopted in the radio frequency module, allowing data transmission in the international ISM frequency range. The implementation based on the geomagnetic sensor that is simple in design, boasts full functions and has excellent drowning detection sensitivity. Additional wireless emission coordinate capability will improve efficiency and shipwreck rescue and maritime navigation in the future.

Graphene Sensing Modulator: Toward Low-Noise, Self-Powered Wireless Microsensors

We present here new types of self-powered, low-interference wireless sensors based on graphene circuits, which can have dual functions: chemical sensing at the molecular level and radio-frequency (RF) modulation. We demonstrate that a fully passive, graphene-based harmonic (transponder) sensor can display a chemically sensitive frequency multiplication effect, which, when linked to a hybrid-fed small antenna, can realize an ultrasensitive, low-profile, light-weight, and potentially flexible RF sensor. We have designed two different types of circuits comprising back-gate graphene field-effect transistors (GFETs) and compared in detail their performance and implementation complexity. We have also proposed a reliable readout method based on the machine learning for extracting the mean value and the fluctuation of chemical doping levels in GFETs. The proposed graphene-based harmonic sensor may potentially benefit a wide range of sensing applications, including, but not limited to, power-efficient, real-time monitoring of chemical/gas exposures and biological agents, as well as emerging wearable and implantable devices.