Low-power Radio Frequency Research Articles

Modeling and design of 3-D MPPT for ultra low power RF energy harvesters

Radio-Frequency (RF) energy harvesting must cope with the limited availability and high variability of the energy source. In this paper, the modeling of an RF harvester for ultra low power environments is presented. A mathematical model based on theoretical analysis is developed. The model demonstrates that the maximum transferred power point is located in a three-dimensional space defined by the input capacitance, the output voltage, and the load resistance of the rectifier circuit. Moreover, the mathematical model returns results in substantial agreement with the SPICE simulation results, while guaranteeing a remarkable reduction of the required computation time. Furthermore, the paper reports the implementation of a mixed signal system for the 3-D MPPT, to be embedded in an RF harvester, in a 65 nm CMOS technology. The circuit exhibits a simulated power consumption lower than 100 nW, making this solution suitable for ultra low power harvesting.

A 3-stage RF down-converter network for portable, wearable 5G applications

The emerging 5G internet-of-things applications in home automation, smart wearables, healthcare monitoring, automotive sensors require low-cost, area efficient, high-performance and low power radio frequency blocks for effective short-range communication. This growing market demand is addressed in this paper by proposing a fully CMOS RF down-converter (RFDC) network for 5G applications. This work aims to achieve high linearity, low noise figure and high gain simultaneously by optimally splitting the performance between the three stages of the RFDC. The proposed down-conversion system is designed in UMC 180 nm CMOS process technology and the post-layout simulations on layout extracted parameters with Cadence SpectreRF shows an IIP3 of − 3.43 dBm, an IIP2 of 78.13 dBm, double-sideband noise figure of 12.76 dB, a conversion gain of 23.69 dB, the spurious-free dynamic range of 71.7 dB, and the phase noise of − 91.39 dBc/Hz at an offset of 5 MHz. The proposed frequency translation circuit occupies a core area of only 0.0043 mm2 and consumes a low power of 12.6 mW from a 1.8 V supply.

Implementation of a Highly-Sensitive and Wide-Range Frequency Measurement Using a Si3N4 MDR-Based Optoelectronic Oscillator

Microwave photonic technologies have been introduced for achieving broadband radio-frequency signal measurement. However, few of the proposed schemes mention the low-power radio-frequency signal detection, which stringently limits their practical applications in certain areas. In this paper, we designed and demonstrated a wideband low-power radio-frequency signal measurement system with optoelectronic oscillator. Here, the unknown radio-frequency signal matched the potential oscillation mode is allowable to be detected, amplified and estimated. The key component in the tunable optoelectronic oscillator is a silicon nitride micro-disk resonator with a very high Q-factor, which is utilized to achieve frequency selection as a microwave filter. A frequency measurement system range from 1 ∼ 20 GHz with radio frequency power as low as −105 dBm, measurement errors of ±375 MHz and the maximum gain of 61.7 dB were realized experimentally

A Triple-Band High-Gain Multibeam Ambient RF Energy Harvesting System Utilizing Hybrid Combining

Overcoming the challenge of battery recharging and replacement in industry Internet-of-Things (IoT) applications is considered by proposing the design of a triple-band high-gain multibeam ambient radio frequency (RF) energy harvesting system utilizing hybrid combining. The novelty of the design is that it simultaneously exploits frequency, space, and polarization to maximize the harvested RF energy. Wideband hybrid combining is proposed, which enables the harvesting of energy at low RF power densities while maintaining the wide frequency and space coverage necessary for ambient RF energy harvesting. The antenna design consisting of 16-ports has an average area per port of 0.3λ × 0.3λ (where λ is the freespace wavelength at 1.8 GHz) and is demonstrated to achieve a wide relative bandwidth of 38.5% covering the GSM-1800, UMTS-2100, and WiFi frequency bands. Hybrid combining of the 16-port antenna provides multiple antenna beams each with up to 11 dBi antenna gain and these provide broad beam coverage. The design for the rectifiers, using multistub impedance matching, is also provided and these are shown to be efficient over the frequency bands of interest. Measurements in an anechoic chamber demonstrate that the proposed energy harvesting system can provide an output dc voltage of more than 755 mV, an output dc power of more than -6.4 dBm and RF-to-dc efficiencies greater than 40% when the power density is more than 1400 μW/m <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> . It is also shown that the proposed system can provide output dc power of 80 μW and 7.3 μW in real outdoor and indoor ambient environments, respectively.

Heating of Ti3C2Tx MXene/polymer composites in response to Radio Frequency fields

Here we report for the first time that Ti3C2Tx/polymer composite films rapidly heat when exposed to low-power radio frequency fields. Ti3C2Tx MXenes possess a high dielectric loss tangent, which is correlated with this rapid heating under electromagnetic fields. Thermal imaging confirms that these structures are capable of extraordinary heating rates (as high as 303 K/s) that are frequency- and concentration-dependent. At high loading (and high conductivity), Ti3C2Tx MXene composites do not heat under RF fields due to reflection of electromagnetic waves, whereas composites with low conductivity do not heat due to the lack of an electrical percolating network. Composites with an intermediate loading and a conductivity between 10–1000 S m−1 rapidly generate heat under RF fields. This finding unlocks a new property of Ti3C2Tx MXenes and a new material for potential RF-based applications.

Multipactor Analysis in Circular Waveguides Excited by TM01 Mode

A series of detailed numerical simulations are used to investigate the properties of multipactor breakdown in circular waveguides propagating the TM01 mode. A Monte Carlo model is constructed to track the motion of the electrons, study the multipactor scenarios, and predict the multipactor thresholds. The theoretical and numerical analyses indicate that the product of the frequency and the gap ( ${f}\cdot {D}$ ) affects both the intensity of the ponderomotive force and its spatial distribution, which results from the nonuniformity of the radio frequency (RF) field and significantly influences the electrons’ trajectories and multipactor trends. The decrease in ${f}\cdot {D}$ results in a remarkable enhancement in the magnitude of the ponderomotive force, while the maximal intensity gradually moves toward the half radius R/2 area. Low values of ${f}\cdot {D}$ correspond to high ponderomotive potential, which sustains the short-range electrons and triggers the single-sided multipactor. In contrast, high values of ${f}\cdot {D}$ correspond to low ponderomotive potential, contributing to long-range electrons and exciting the double-sided multipactor. Fitting to the susceptibility diagram produces the border line and a modified ${f}\cdot {D}$ threshold of ( ${f}\cdot {D}$ )th $\approx ~338.4$ GHz mm, which separates the susceptibility diagram into single-sided, double-sided, and mixed-sided zones. The initial electron energy influences their trajectories at high ${f}\cdot {D}$ and low RF power. This effect tends to dominate the multipactor behavior in the mixed-sided region.

A Study on the Effect of Argon-Oxygen Plasma Treatment on Ultra-Thin Expanded PTFE Membrane

Polymer films are plasma treated to improve surface properties making them hydrophilic or hydrophobic. Expanded polytetrafluoroethylene (ePTFE) is used in a wide variety of applications but only a few report on plasma treated ePTFE. Within these very few studies on ePTFE, the use of ultra-thin membrane could hardly be found. The purpose of this study is to investigate the effect of plasma treatment (Argon-Oxygen) on the hydrophobicity of ultra-thin ePTFE membrane (4um thickness). This study used nine (9) experimental legs of ePTFE subjected to respective plasma power (150W, 315W and 600W) and exposure time (300s, 450s and 600s) for each leg. Contact angle was measured prior and after subjecting to plasma condition using contact angle meter. Energy pen was also used to verify its hydrophobicity. Scanning electron microscopy (SEM) with 10,000x magnification was used to check for any change in surface after exposing to each condition. The findings showed that the membrane surface changed after exposure to plasma. All legs became hydrophilic. 102◦ contact angle was measured from raw sample, but the samples exposed to plasma had contact angles ranging from max of 68◦ to min of 48◦. The results showed that the degree of surface change could be correlated to the plasma parameters applied. Furthermore, the highest radio frequency (RF) power applied resulted to contact angle in the range of 60◦ while the lowest RF power applied resulted to the lowest contact angle, in the range of 40◦, measured. On the other hand, no particular trend was observed based on exposure time. Based on the gathered results, the ultra-thin ePTFE, in order to maintain its hydrophobicity, must not be applied with argon-oxygen plasma treatment. However, if the ultra-thin ePTFE is to be made hydrophilic, argon-oxygen plasma treatment could be applied while adjusting the plasma parameters to meet the desired hydrophilicity level.

Development and beam commissioning of a continuous-wave four-vane heavy ion radio-frequency quadrupole accelerator based on stable operation

Abstract A continuous-wave (CW) heavy ion radio frequency quadrupole (RFQ) accelerator was developed for the Low Energy Accelerator Facility (LEAF) at IMP. The RFQ accelerator is the most effective accelerator for accelerating the low energy high intensity beam, but there are challenges achieving the stable CW operation. This paper presents the development of the LEAF RFQ based on the stable CW operation. In the beam dynamics design, a multi-harmonic buncher is utilized to reduce the longitudinal emittance and the constant-voltage design is applied for low RF power loss. In the radio frequency (RF) design, the constant-voltage four-vane RFQ is selected to reduce the power dissipation. The π -mode stabilizing loop (PISL) is employed to reduce the admixture of the dipole field. In order to ensure the stability of the cavity structure, the multi-physics of the cavity are analysed. The resonant frequency sensitivities of the cooling water temperature are studied to tune the cavity frequency during operation. Through low power test and tuning, the resonance frequency and field distributions are optimized. The beam commissioning ( 4He 1 + , 14N 2 + and 86Kr 13 + ) and some radiation experiments have been performed. The entire processes of the LEAF RFQ development, such as, beam dynamics design, RF design, multi-physics analysis, low power test, high power conditioning, beam commissioning and some radiation experiments, will be detailed presented in this paper. The results of testing and commissioning indicate that the development of the LEAF RFQ has succeeded. And the design scheme for RFQ with stable CW operation in this work can be applied to other future CW RFQs.

Perovskite PV-Powered RFID: Enabling Low-Cost Self-Powered IoT Sensors

Photovoltaic (PV) cells have the potential to serve as on-board power sources for low-power IoT devices. Here, we explore the use of perovskite solar cells to power Radio Frequency (RF) backscatter-based IoT devices with a few {\mu}W power demand. Perovskites are suitable for low-cost, high-performance, low-temperature processing, and flexible light energy harvesting that hold the possibility to significantly extend the range and lifetime of current backscatter techniques such as Radio Frequency Identification (RFID). For these reasons, perovskite solar cells are prominent candidates for future low-power wireless applications. We report on realizing a functional perovskite-powered wireless temperature sensor with 4 m communication range. We use a 10.1% efficient perovskite PV module generating an output voltage of 4.3 V with an active area of 1.06 cm2 under 1 sun illumination, with AM 1.5G spectrum, to power a commercial off-the-shelf RFID IC, requiring 10 - 45 {\mu}W of power. Having an on-board energy harvester provides extra-energy to boost the range of the sensor (5x) in addition to providing energy to carry out high-volume sensor measurements (hundreds of measurements per min). Our evaluation of the prototype suggests that perovskite photovoltaic cells are able to meet the energy needs to enable fully autonomous low-power RF backscatter applications of the future. We conclude with an outlook into a range of applications that we envision to leverage the synergies offered by combining perovskite photovoltaics and RFID.

Low-Power RF Signal Detection Using a High-Gain Tunable OEO Based on Equivalent Phase Modulation

A novel photonic method for low power radio-frequency (RF) signal detection by a tunable optoelectronic oscillator (OEO) with high gain based on equivalent phase modulation (EPM) is proposed and experimentally demonstrated. A dual-parallel Mach-Zehnder modulator is utilized to generate the EPM signal with a controllable optical carrier to sideband ratio, by which the gain to the RF signal by the OEO loop can be enhanced. A phase-shifted fiber Bragg grating (PS-FBG) with a narrow-band notch in its reflection band implements the phase modulation to intensity modulation conversion by removing one sideband of the EPM signal. The gain and noise performance of the detection system are theoretically analyzed and simulated. In the experiment, the maximum gain of 10.4 dB is obtained at 8 GHz, and the detection sensitivity for RF signals from 2 to 18 GHz are within the range of −87.7 to −84.3 dBm by using the developed detection system. Compared to normal phase modulation based scheme, the EPM-based system offers 9.1 dB higher gain. Utility of the proposed approach for detecting modulated RF signal is also investigated and an optimization scheme is discussed.

Treatment of glioblastoma using multicomponent silica nanoparticles.

Glioblastomas (GBMs) remain highly lethal. This partially stems from the presence of brain tumor initiating cells (BTICs), a highly plastic cellular subpopulation that is resistant to current therapies. In addition to resistance, the blood-brain barrier limits the penetration of most drugs into GBMs. To effectively deliver a BTIC-specific inhibitor to brain tumors, we developed a multicomponent nanoparticle, termed Fe@MSN, which contains a mesoporous silica shell and an iron oxide core. Fibronectin-targeting ligands directed the nanoparticle to the near-perivascular areas of GBM. After Fe@MSN particles deposited in the tumor, an external low-power radiofrequency (RF) field triggered rapid drug release due to mechanical tumbling of the particle resulting in penetration of high amounts of drug across the blood-brain tumor interface and widespread drug delivery into the GBM. We loaded the nanoparticle with the drug 1400W, which is a potent inhibitor of the inducible nitric oxide synthase (iNOS). It has been shown that iNOS is preferentially expressed in BTICs and is required for their maintenance. Using the 1400W-loaded Fe@MSN and RF-triggered release, in vivo studies indicated that the treatment disrupted the BTIC population in hypoxic niches, suppressed tumor growth and significantly increased survival in BTIC-derived GBM xenografts.

Integrated cmos rectifier for rf-powered wireless sensor network nodes

This article presents a review of the CMOS rectifier for radio frequency energy harvesting application. The on-chip rectifier converts the ambient low-power radio frequency signal coming to antenna to useable DC voltage that recharges energy to wireless sensor network (WSN) nodes and radiofrequency identification (RFID) tags, therefore the rectifier is the most important part of the radio frequency energy harvesting system. The impedance matching network maximizes power transfer from antenna to rectifier. The design and comparison between the simulation results of one- and multi-stage differential drive cross connected rectifier (DDCCR) at the operating frequencies of 2.44GHz, and 28GHz show the output voltage of the multi-stage rectifier doubles at each added stage and power conversion efficiency (PCE) of rectifier at 2.44GHz was higher than 28GHz. The (DDCCR) rectifier is the most efficient rectifier topology to date and is used widely for passive WSN nodes and RFID tags.

Flexible lamb wave resonators with high figure of merit

This paper presents a 429 MHz flexible Lamb wave resonator based on lithium niobate thin films with a high figure of merit (FoM) of 205, which is about 10 times higher than the FoM of the flexible resonator presented in our previous work. The measured corresponding quality factor (Q) and electromechanical coupling coefficient (Kt2) are 1268 and 16.2%, respectively. The resonant frequency, Q, and Kt2 of the flexible resonator show maximum changes of only 0.11%, 0.37%, and 0.31%, respectively, under a repeated mechanical bending condition up to 10 000 times at a bending radius of 3 mm. We also found that FlexMEMS technology we proposed not only endows Lamb wave resonators with mechanical flexibility but also improves FoM by ∼180% compared to their counterpart, conventional Lamb wave resonators on rigid silicon substrates. The flexible resonators with much improved FoM will find applications as low-power radio frequency key components in emerging applications, especially Internet of Things.

Lessons learned from the application of machine learning to studies on plant response to radio-frequency

This paper applies Machine Learning (ML) algorithms to peer-reviewed publications in order to discern whether there are consistent biological impacts of exposure to non-thermal low power radio-frequency electromagnetic fields (RF-EMF). Expanding on previous analysis that identified sensitive plant species, we extracted data from 45 articles published between 1996 and 2016 that included 169 experimental case studies of plant response to RF-EMF. Raw-data from these case studies included six different attributes: frequency, specific absorption rate (SAR), power flux density, electric field strength, exposure time and plant type (species). This dataset has been tested with two different classification algorithms: k-Nearest Neighbor (kNN) and Random Forest (RF). The outputs are estimated using k-fold cross-validation method to identify and compare classifier mean accuracy and computation time. We also developed an optimization technique to distinguish the trade-off between prediction accuracy and computation time based on the classification algorithm. Our analysis illustrates kNN (91.17%) and RF (89.41%) perform similarly in terms of mean accuracy, nonetheless, kNN takes less computation time (3.38 s) to train a model compared to RF (248.12 s). Very strong correlations were observed between SAR and frequency, and SAR with power flux density and electric field strength. Despite the low sample size (169 reported experimental case studies), that limits statistical power, nevertheless, this analysis indicates that ML algorithms applied to bioelectromagnetics literature predict impacts of key plant health parameters from specific RF-EMF exposures. This paper addresses both questions of the methodological importance and relative value of different methods of ML and the specific finding of impacts of RF-EMF on specific measures of plant growth and health. Recognizing the importance of standardizing nomenclature for EMF-RF, we conclude that Machine Learning provides innovative and efficient RF-EMF exposure prediction tools, and we propose future applications in occupational and environmental epidemiology and public health.

Low-power fully monolithic MICS band receiver for 402-405 MHz implantable devices

ABSTRACTA 402–405MHz fully monolithic Radio Frequency (RF) low-Intermediate Frequency (IF) receiver is presented. The proposed low-power RF receiver consists of a differential Common gate-Common Source Low-Noise Amplifier (CG-CS LNA) with a positive–negative feedback technique, passive mixer, fully integrated Voltage Controlled Oscillator (VCO), and an IF Variable Gain Amplifier (VGA). To achieve a wide tuning range while keeping a low gain (Kvco), the VCO has 16 bands selectable by a 4-bit digital control. The complete receiver prototype is implemented in a 0.13μm CMOS process and occupies 0.625 mm2 active chip area. The receiver consumes only 3.76 mW of power from a 1.2 V power supply and has a gain of 45 dB and a noise figure of 13.6 dB (integrated from 20 Hz to 0.5 GHz). The design achieves an in-band IIP3 of 2 dBm, IIP2 better than 44 dBm. It presents a 3-dB IF bandwidth of 3 MHz with −80 dBm sensitivity.

An In0.53Ga0.47As/In0.52Al0.48As Heterojunction Dopingless Tunnel FET With a Heterogate Dielectric for High Performance

In this paper, an In <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.53</sub> Ga <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.47</sub> As/In <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.52</sub> Al <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.48</sub> As heterojunction dopingless tunnel field-effect transistor (HDL-TFET) with an HfO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> /SiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> heterogate dielectric is proposed, where the N <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">+</sup> -pocket with variable electron concentration can be formed by adjusting the length of source-side channel (LSC) based on the charge plasma concept, instead of employing conventional ion implantation or dual-material gate techniques. It aims to improve the device performance and simplify the device fabrication. At the drain bias of 0.3 V, numerical simulations show that the on-state current (ION) of the HDL-TFET with LSC = 4 nm can approach ~10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-5</sup> A/μm that is far higher than that of the Si-DL-TFET (~10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-10</sup> A/μm), and the average subthreshold swing (SS <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">avg</sub> ) can approach 36.6 mV/decade that is significantly lower than that of the Si-DL-TFET (89.2 mV/decade). It is also found that the drain-induced barrier lowering (DIBL) effect and the ambipolar current can be effectively suppressed in the HDL-TFET because of an existence of heterojunction. Under the condition of low gate and drain biases, the HDL-TFET exhibits peak values of the cutoff frequency (f <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">T</sub> ) and the maximum oscillation frequency (f <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">max</sub> ) approaching 13 and 4.73 GHz, respectively, while the Si-DL-TFET yields those of 8.05 and 2.26 GHz, respectively, under relatively higher biases. It indicates that the HDL-TFET is a promising device for low-power consumption radio frequency applications.

Valores hemáticos en pacientes sometidos a liposucción con anestesia general más solución de Klein sin lidocaína

Introducción: La liposucción es una cirugía que tiene alta demanda en actualidad ya que ofrece seguridad por la utilización de técnicas que disminuyen el riesgo para el paciente. Tres aspectos han sido mejorados desde su implementación: la calidad de sus incisiones, la utilización de cánulas más sofisticadas conectadas a una bomba al vacío y la introducción de la técnica tumescente. Sin embargo, aún suceden complicaciones, y una de ellas, es la pérdida sanguínea.&#x0D; Objetivo: Describir los valores de la hemoglobina y el hematocrito en pacientes sometidos a cirugía de liposucción mediante anestesia general mas infiltración de la solución de Klein sin lidocaína.&#x0D; Material y métodos: Se realizó un estudio epidemiológico, descriptivo, retrospectivo en 59 pacientes de 15 a 55 años, sometidos a cirugía de liposucción. El procedimiento quirúrgico se realizó bajo anestesia general e intubación; se infiltró con solución de Klein sin utilizar xilocaina, con la técnica superhúmeda. Fueron utilizadas cánulas metálicas de hasta 6 mm conectadas a una bomba al vacío, aspirando grasa de abdomen, flancos y parte correspondiente de la espalda; se aplicó radiofrecuencia de baja potencia e hidratación y se administraron tres dosis de cefazolina 1g intravenoso.&#x0D; Resultados: El volumen promedio de grasa aspirado fue de 2667 ml, el promedio de descenso de la hemoglobina fue de 4,28 g/dl (IC 95% 3,9 – 4,5), el promedio de descenso del hematocrito fue de 10,3% (IC 95% 9,2 – 12,1).&#x0D; Conclusiones: En esta investigación la disminución de los valores de hemoglobina y hematocrito no fueron significativos ni ocurrió complicaciones, se obtuvo un alto grado de satisfacción de los pacientes. Este procedimiento quirúrgico es seguro si se observan las recomendaciones y protocolos establecidos por la Sociedad Americana de Cirujanos Plásticos.

Hydrogen barrier performance of sputtered La2O3 films for InGaZnO thin-film transistor

We report the hydrogen barrier performance of sputtered La2O3 thin films for the device stability of amorphous indium–gallium–zinc–oxide (a-IGZO) thin-film transistors (TFTs). Hydrogen acts as a shallow donor in a-IGZO films, which makes TFTs conductive, resulting in degradation of their on/off properties. Since hydrogen can be easily incorporated by external environments or post-processing, an appropriate hydrogen barrier is essential for enhancing device stability. La2O3, with its extreme electronegativity, can provide excellent hygroscopic characteristics. Because hydrogen exists in the form of –OH groups inside a-IGZO films, La2O3 is expected to be a promising barrier material for preventing hydrogen incorporation. Therefore, we investigate the growth characteristics of sputtered La2O3 thin films as hydrogen barrier layers, focusing on variations in growth rate, refractive index, and film stress, which depend on various process parameters, such as radio-frequency (RF) power, O2 partial pressure, and substrate temperature during reactive magnetron sputtering. The effects of these parameters on hydrogen barrier properties are systematically investigated and correlated with the microstructures of La2O3 films. The results demonstrate that La2O3 films grown with low RF power and low O2 partial pressure have an amorphous phase and provide excellent hydrogen barrier performance. We anticipate that these experimental results will help improve the environmental stability of a-IGZO TFTs.

A Silicon Photonic RF Phase Shifter With Linear Phase Response and Low RF Power Variation

We propose and experimentally demonstrate a microwave photonic phase shifter based on a tunable silicon photonic interleaver. This device consists of a microring resonator, a tunable interleaver, and a $2\,\times \,1$ multimode interferometer (MMI). By thermally tuning the interleaver, a linear phase shift of 188° is realized with a linearity of 0.08 and a radio-frequency (RF) power variation within 1 dB for a 40-GHz signal.

Highly sensitive, broadband microwave frequency identification using a chip-based Brillouin optoelectronic oscillator.

Detection and frequency estimation of radio frequency (RF) signals are critical in modern RF systems, including wireless communication and radar. Photonic techniques have made huge progress in solving the problem imposed by the fundamental trade-off between detection range and accuracy. However, neither fiber-based nor integrated photonic RF signal detection and frequency estimation systems have achieved wide range and low error with high sensitivity simultaneously in a single system. In this paper, we demonstrate the first Brillouin opto-electronic oscillator (B-OEO) based on on-chip stimulated Brillouin scattering (SBS) to achieve RF signal detection. The broad tunability and narrowband amplification of on-chip SBS allow for the wide-range and high-accuracy detection. Feeding the unknown RF signal into the B-OEO cavity amplifies the signal which is matched with the oscillation mode to detect low-power RF signals. We are able to detect RF signals from 1.5 to 40 GHz with power levels as low as -67 dBm and a frequency accuracy of ± 3.4 MHz. This result paves the way to compact, fully integrated RF detection and channelization.