Radio Frequency Performance Research Articles

Monolithically Integrated RF MEMS-Based Variable Attenuator for Millimeter-Wave Applications

This paper reports a millimeter-wave radio frequency (RF) microelectromechanical systems (MEMS)-based variable attenuator implemented by monolithically integrating CPW-based hybrid couplers with lateral MEMS varactors on a silicon-on-insulator (SOI) substrate. The MEMS varactor features a Chevron-type electrothermal actuator that controls the lateral movement of a thick plate allowing precise change of capacitive loading on a CPW line leading to a change in isolation between input and output. The proposed variable attenuator is successfully fabricated on an SOI substrate with a device footprint of 3.8 $\text {mm}\times 3.1$ mm. The fabrication process provides flexibility to extend this module and implement more complex RF signal conditioning functions, thus making it more appealing to realize a wide range of reconfigurable RF devices. The measured RF performance shows that the device exhibits attenuation levels ( $S_{{21}}$ ) ranging from 10 to 25 dB, at the center frequency of 60 GHz with a bandwidth of 4 GHz and a return loss of better than 20 dB. The device involves laterally moving 20- $\mu \text{m}$ -thick structures, hence offers reliable operation and eliminates MEMS problems like stiction, dielectric charging, and microwelding observed in surface micromachined thin membranes.

ESD protection circuit for V-band RF applications in a 65nm CMOS technology

To apply radio frequency circuits, nanoscale CMOS technologies are greatly used but this consequence to a thinner gate oxide and silicided drain/source. With this, the electrostatic discharge (ESD) robustness of RF circuits will be much more degraded. Therefore, there is a need for an ESD protection circuit design in RF circuits against ESD damages. In this paper, the proposed ESD protection circuit is presented with concept based silicon-controlled rectifier (SCR) device, two diodes, PMOS transistor and an inductor to efficiently provide protection for radio-frequency (RF) circuits from ESD damages in nanoscale CMOS process. The concept based SCR device is aided with an inductor to provide efficient ESD path discharge to the SCR device. Moreover, the inductor is used to resonate out the parasitic capacitance generated by the ESD protection circuit at the preferred frequency. In addition, the proposed ESD protection circuit is implemented to a low noise amplifier (LNA) at 60-GHz frequency within an efficient area. Furthermore, the ESD protection circuit is simulated to achieve over 2-kV human body model ESD robustness with good RF performances on LNA in 65-nm CMOS technology.

System-Level Performance of Chip-Based Brillouin Microwave Photonic Bandpass Filters

Microwave photonic (MWP) filters using on-chip stimulated Brillouin scattering offer great potential for next-generation radio frequency (RF) applications due to the unprecedented high spectral resolution, flexible programmability, and ultra-wideband frequency agility. Although impressive functionalities have been reported, limited link performance, due to the amplification noise induced by the Brillouin gain process, hinders the practical deployment in existing RF applications. In this paper, we present the first comprehensive numerical and experimental study of chip-based Brillouin MWP bandpass filters implemented in a range of link configurations. In the experiments, key RF performance figures of merit, including link gain, noise figure, passband resolution, bandwidth tunability, and passband extinction of chip-based Brillouin filters are experimentally investigated and numerically analyzed. This comprehensive study points out a preferable filter scheme with optimized system-level performance. The numerical model developed in this paper allows for extrapolations to further improve the performance. The systematic work establishes a feasible design route for achieving high link-performance chip-based Brillouin microwave photonic bandpass filters.

GFET Asymmetric Transfer Response Analysis through Access Region Resistances.

Graphene-based devices are planned to augment the functionality of Si and III-V based technology in radio-frequency (RF) electronics. The expectations in designing graphene field-effect transistors (GFETs) with enhanced RF performance have attracted significant experimental efforts, mainly concentrated on achieving high mobility samples. However, little attention has been paid, so far, to the role of the access regions in these devices. Here, we analyse in detail, via numerical simulations, how the GFET transfer response is severely impacted by these regions, showing that they play a significant role in the asymmetric saturated behaviour commonly observed in GFETs. We also investigate how the modulation of the access region conductivity (i.e., by the influence of a back gate) and the presence of imperfections in the graphene layer (e.g., charge puddles) affects the transfer response. The analysis is extended to assess the application of GFETs for RF applications, by evaluating their cut-off frequency.

Improved MRD 4H-SiC MESFET with High Power Added Efficiency.

An improved multi-recessed double-recessed p-buffer layer 4H–SiC metal semiconductor field effect transistor (IMRD 4H-SiC MESFET) with high power added efficiency is proposed and studied by co-simulation of advanced design system (ADS) and technology computer aided design (TCAD) Sentaurus software in this paper. Based on multi-recessed double-recessed p-buffer layer 4H–SiC metal semiconductor field effect transistor (MRD 4H-SiC MESFET), the recessed area of MRD MESFET on both sides of the gate is optimized, the direct current (DC), radio frequency (RF) parameters and efficiency of the device is balanced, and the IMRD MESFET with a best power-added efficiency (PAE) is finally obtained. The results show that the PAE of the IMRD MESFET is 68.33%, which is 28.66% higher than the MRD MESFET, and DC and RF performance have not dropped significantly. Compared with the MRD MESFET, the IMRD MESFET has a broader prospect in the field of microwave radio frequency.

Investigation of geometrical and doping parameter variations on GaSb/Si‐based double gate tunnel FETs: A qualitative and quantitative approach for RF performance enhancement

AbstractThis paper compares the radio frequency (RF) performance enhancement of GaSb/Si‐based double gate (DG) tunnel field‐effect transistors (TFETs) and DG TFETs with gate‐drain overlap devices using technology computer‐aided design (TCAD) simulations. The geometrical parameters taken under consideration are gate length (Lg), gate oxide thickness (tox), channel thickness (tch), and doping parameters are channel doping (Nch), drain doping (Nd), and source doping (Ns). These parameters are varied to extract the RF parameters, cut‐off frequency (ft), maximum oscillation frequency (fmax), intrinsic gain, and admittance (Y) parameters. DG TFET with gate‐drain overlap offers highest fmax values of 977 GHz for drain doping of 1e20 cm−3. Higher values of output resistance (Ro) results in high intrinsic gain values for DG TFET with gate‐drain overlap. In terms of Y parameters, DG TFET with gate‐drain overlap shows better Y11 and Y22 values compared with DG TFET. A quantitative model as a function of geometrical and doping parameters is modelled for all the RF parameters that validate the simulated values and predicted values.

Electrostatic and radio frequency performance investigation of δ-doped In0.53Ga0.47As/InP stepped poly gate metal oxide semiconductor field effect transistor

A δ-doped stepped poly gate heterostructure metal oxide semiconductor field effect transistor (HMOSFET) has been analysed. The insertion of a δ-doped layer within the channel region of the proposed In0.53Ga0.47As/InP HMOSFET results in the reduction of short channel effects and the junction capacitance. In the proposed device, the split gate with dissimilar oxide thickness from the source end to drain end have p+ poly in first and third region whereas, n+ poly is in the second region. Further, the δ-doped layer within the channel in stepped poly gate HMOSFET significantly enhances the electrical characteristics of the device. Simulation results reveal that in comparison with stepped poly gate and conventional HMOSFET, δ-doped stepped poly gate HMOSFET gives improved electron transport phenomena and analog characteristics in terms of electron mobility, electric field, electron velocity, transconductance, On resistance, transconductance generation factor and switching ratio. Further, reduction in junction capacitance improves the radio frequency performance metrics in terms of cut-off frequency, maximum frequency and gain bandwidth product.

Practical application of small antennas in hardware platforms

The study discusses the practical challenges of incorporating small antennas into electrically small, power-limited devices, including those intended for wireless connection to the Internet of Things. It describes a number of common pitfalls and provides advice to antenna engineers and device designers on obtaining the best possible radio-frequency performance.

A Compact 16-Way High-Power Combiner Implemented Via 3-D Metal Printing Technique for Advanced Radio-Frequency Electronics System Applications

In this paper, a size-compact and monolithically integrated millimeter-wave 16-way high-power combiner for advanced radio-frequency (RF) electronics applications is developed featuring a wide operational bandwidth and high isolations between the combiner's adjacent ports. The proposed combiner is operating at the X band and is composed of fifteen 3-dB directional coupler units that are properly configured to achieve the overall structural compactness. The combiner is fast-prototyped as a single part by employing a metallic three-dimensional (3-D) printing technique, which successfully overcomes the difficulty in its monolithic implementation by using conventional subtractive manufacturing techniques. The experimental results demonstrate that the 16-way power combiner achieves an approximately 21% operational bandwidth (8.5–10.5 GHz) at the X band with port isolations of more than 20 dB, an amplitude imbalance of about ±1 dB, a phase deviation of around ±1°, and good return and insertion losses. The excellent RF performance of the combiner makes it a good candidate for applications in multiport high-power electronics systems where highly efficient power transmission and conversion among different ports are required.

Optically controlled millimetre‐wave switch with stepped‐impedance lines

A photoconductive grounded coplanar waveguide (GCPW) millimetre-wave switch controlled by a single infrared light-emitting diode is presented. By converting a straight GCPW transmission line into an alternating stepped-impedance line structure, the proposed device shows an on-state insertion loss of <2.9 dB and an off-state isolation of more than 15 dB over a wide-frequency range of 12–30 GHz, with a particularly good radio-frequency performance in the K-band (18–27 GHz). The required optical power and electrical power of the switch are only 199 and 364 mW, respectively. This device also demonstrates an absorptive characteristic with a low reflection coefficient of <−13.5 dB within this frequency range for both the on and off states. In addition, by employing through-holes for illumination of a silicon superstrate, the proposed device can be fabricated with rapid and low-cost laser etching and can be easily integrated with other microwave and millimetre-wave circuits.

Design, fabrication, and radio frequency property evaluation of a through-glass-via interposer for 2.5D radio frequency integration

In this paper, a through-glass-via (TGV) interposer for 2.5D radio frequency (RF) integration is presented. A coplanar waveguide (CPW) transmission line with grounded TGVs on one side interconnects with the mounted RF devices, and an electrical ground plane on the other side. Tapered TGVs are fabricated using a combined method of sandblasting and thinning/polishing process to achieve precise control of the profile of the vias and improve uniformity. The TGVs are metalized by conformal copper (Cu) electroplating to form a vertical interconnection between the upper and lower metal layers, which can maintain RF performance and avoid thermal stress issues. The CPW transmission lines with electrically grounded TGVs and test structures are designed, fabricated and tested to evaluate the TGV’s RF performance and suitability for 2.5D RF integration. The RF measurements show that the insertion loss is about 0.13 dB mm−1@10 GHz for the CPW line with grounded TGV which is less than 0.1 dB@10 GHz for a single TGV. We analyzed S parameter for the tests and simulations when taking into account various factors in the manufacturing process, such as the surface roughness and metal resistivity. The results provide a research direction for the optimization of the parameters in the follow-up study. In addition, a 2.5D RF receiver module based on the proposed TGV interposer in the L-band is assembled and validated. The gain value of the TGV interposer integrated RF module is about 14.4 dB, which is close to the theoretical value.

Short-gate AlGaN/GaN high-electron mobility transistors with BGaN buffer**Project supported by the Foundation Project of the Science and Technology on Electro-Optical Information Security Control Laboratory, China (Grant No. 614210701041705)

Using the semi-insulating property and small lattice constant a of wurtzite BGaN alloy, we propose a BGaN buffer with a B-content of 1% to enhance two-dimensional electron gas (2DEG) confinement in a short-gate AlGaN/GaN high-electron mobility transistor (HEMT). Based on the two-dimensional TCAD simulation, the direct current (DC) and radio frequency (RF) characteristics of the AlGaN/GaN/B0.01Ga0.99N structure HEMTs are theoretically studied. Our results show that the BGaN buffer device achieves good pinch-off quality and improves RF performance compared with GaN buffer device. The BGaN buffer device can allow a good immunity to shift of threshold voltage for the aspect ratio (LG/d down to 6, which is much lower than that the GaN buffer device with LG/d=11 can reach. Furthermore, due to a similar manner of enhancing 2DEG confinement, the B0.01Ga0.99N buffer device has similar DC and RF characteristics to those the AlGaN buffer device possesses, and its ability to control short-channel effects (SCEs) is comparable to that of an Al0.03Ga0.97N buffer. Therefore, this BGaN buffer with very small B-content promises to be a new method to suppress SCEs in GaN HEMTs.

Radio Frequency Performance Projection and Stability Tradeoff of h-BN Encapsulated Graphene Field-Effect Transistors

Hexagonal boron nitride (h-BN) encapsulation significantly improves carrier transport in graphene. This work investigates the benefit of implementing the encapsulation technique in graphene field-effect transistors (GFET) in terms of their radio frequency (RF) performance. For such a purpose, a drift-diffusion self-consistent simulator is prepared to get the GFET electrical characteristics. Both the mobility and saturation velocity information are obtained by means of an ensemble Monte Carlo simulator upon considering the relevant scattering mechanisms that affect carrier transport. RF figures of merit are simulated using an accurate small-signal model that includes non-reciprocal capacitances. Results reveal that the cutoff frequency could scale up to the physical limit given by the inverse of the transit time. Projected maximum oscillation frequencies, in the order of few THz, are expected to exceed the values demonstrated by InP and Si based RF transistors. The existing trade-off between power gain and stability and the role played by the gate resistance are also studied. High power gain and stability are feasible even if the device is operated far away from current saturation. Finally, the benefits of device unilateralization and the exploitation of the negative differential resistance region to get negative-resistance gain are discussed.

Bare die connections via aerosol jet technology for millimeter wave applications

AbstractThis paper presents a comparison of chip connections using aerosol jet (AJ) and bond technology on low-cost printed circuit board (PCB) substrates. First, the behavior of the used gap filler material and the used silver ink for AJ technology on PCBs are characterized. In addition to comparing the radio frequency (RF) performance (DC to 67 GHz) of the two technologies, the mechanical stability is also compared. While the AJ technology transitions score above all for their RF performance and the lower requirements (surface finish, pad size, and adhesion) on the PCB, the bonding technology has clear advantages, especially with a different coefficient of thermal expansion values of the substrates to be connected. Finally, the measurement results of a complete package are shown, whereby the chip connection is realized once by means of AJ and once by bonding wires.

Radiofrequency performance of hydrogenated diamond MOSFETs with alumina

Hydrogenated diamond MOSFETs with self-oxidized alumina as a gate dielectric are fabricated. The diamond MOSFETs show a high maximum drain current density of 466 mA/mm at VGS = −6 V, a transconductance of 58 mS/mm, and an off-state breakdown voltage of −53 V. The maximum output power density reaches 745 mW/mm at 2 GHz continuous wave, which is the highest reported value for diamond transistors measured at 2 GHz. The output power value measured is lower than that estimated. Pulse I-V analysis shows that the main factor that affects the output power of the diamond MOSFETs is the traps in the channel.

Compact Model for Tunnel Diode Body Contact SOI n-MOSFETs

A compact model for tunnel diode body contact (TDBC) silicon-on-insulator (SOI) n-MOSFETs was developed in this paper. The compact model is implemented in Verilog-A to simulate the dc and radio frequency (RF) performance of a TDBC SOI MOSFET. The TDBC SOI MOSFETs are successfully fabricated and are used to measure important transistor electrical parameters. The investigation results reveal that TDBC structure suppresses floating body effects (FBEs) as well as T-gate body (TB) contact structure and shows significant improvement in RF performance without introducing additional parasitic capacitances compared with the TB device. Kink phenomena and an abnormal subthreshold swing originating from FBEs are sufficiently suppressed. It is demonstrated that the TDBC SOI MOSFETs provide a promising concept for digital, analog, and RF applications. The outputs from this analytic model are in fair agreement with the TDBC experimental data, which validates the effectiveness and robustness of the compact model for TDBC SOI technology. Finally, good accuracy ensures that the proposed model is applicable for the implementation in circuit simulation tools.

Comparative Investigation on Bias Dependent RF Performance of SOI Substrates

In this work, direct current (DC) bias effects on radio frequency (RF) performance of three types of RF silicon-on-insulator (RF-SOI) substrates are comparatively investigated by using coplanar waveguide (CPW) lines. It is demonstrated that the loss and harmonic distortion of CPW line on high resistivity silicon-on-insulator (HR-SOI) substrate are more sensitive to variations of DC bias. This is attributed to the parasitic nonlinear capacitance and conductance in the parasitic surface conduction (PSC) layer. In comparison, the influence of DC bias on the RF performance of trap-rich silicon-on-insulator (TR-SOI) substrate can be negligible due to the trap-rich layer which can get rid of the PSC by trapping free carriers inside the substrate. Bias effects on the RF performance of two types of TR-SOI substrates with different high resistivity substrate are also compared. The results show that the RF characteristics of TR-SOI #2 (TR2) is more independent with respect to the applied bias than that of TR-SOI #1 (TR1). This stems from the smaller parasitic effects and increased effective resistivity.

Investigation of RF and linearity performance of electrode work‐function engineered HDB vertical TFET

This work realises a hetero-dielectric buried oxide vertical tunnel held effect transistor (HDB VTFET) and investigates its radio frequency (RF) and linearity characteristics. First time, the concept of hetero-dielectric buried oxide (BOX) in VTFET is used to obtain the superior improvement in terms of different RF and linearity hgure of merits such as C gs , C gd , C gg , f T , Gain Bandwidth Product (GBP), t, Transconductance Frequency Product (TFP), Transconductance Generation Factor (TGF), g m2 , g m3 , VIP 2 , VIP 3 , IIP 3 , IMD 3 and 1-dB compression point. Also, the influence of HfO2 BOX length scaling on these FOMs is analysed. The results reveal that the HDB VTFET can be a promising contender to replace bulk metal-oxide semiconductor held-effect transistors in analogue/mixed signal system-on-chip and high-frequency microwave applications and the accuracy of this device is validated by TCAD Sentaurus simulator.

ZigBee Radio Frequency (RF) Performance on Raspberry Pi 3 for Internet of Things (IoT) based Blood Pressure Sensors Monitoring

Wireless Sensor Network has grown rapidly, e.g. using the Zigbee RF module and combined with the Raspberry Pi 3, a reason at this research is building a Wireless Sensor Network (WSN). this research discusses how sensor nodes work well and how Quality of Service (QoS) from the Sensor node being analyzed and the role of Raspberry Pi 3 as an internet gateway will sending a blood pressure data to the database and displayed in real-time on the internet, from this research it is expected that patients can check the blood pressure from home and don’t need to the Hospital even data can be quickly and accurately received by Hospital Officers, doctors, and medical personnel. the purpose of this research is make a prototype to providing a blood pressure (mmHg) real-time data from systolic and diastolic data patient’s that determine patients suffering from symptoms of certain diseases, i.e, anemia, symptoms of hypertension and even more chronic diseases. this research discusses how sensor nodes work well and how Quality of Service (QoS) from the Sensor node being analyzed and the role of Raspberry Pi 3 as an internet gateway will sending a blood pressure data to the database and displayed in real-time on the internet. Furthermore, Zigbee has the task of sending Blood pressure (mmHg) data in real-time to the database and then sent to the internet from Zigbee end-device communication to ZigBee coordinator. Zigbee communication at a distance of 5 meters, RSSI simulations show a value of -29 dBm and the experiment shows a value of -40 dBm, at a distance of 100 m, RSSI shows a value of -55 dBm (simulation) and -86 dBm (experiment).

Durability testing of electronic textile surface resistivity and textile antenna performance

As wearable electronics become more prevalent in everyday life, there is a growing desire to integrate circuits and antennae into clothing. One way that this integration may occur is through use of electronic textiles (e-textiles). However, changes in environmental and wear conditions may affect the conductive data communication performance of the e-textile, such as surface resistivity and antenna radiation characteristics. In this study, the effects of pilling, wrinkling, abrasion, and laundering of e-textiles were examined for resistivity performance. E-textile resistivity performance from both direct current (DC) and radiofrequency (RF) perspectives were measured following AATCC and ASTM standards. For DC performance, results indicate that pilling causes severe damage to e-textile resistivity, while laundering and wrinkling did not substantially affect e-textile resistivity performance. For RF performance in this study, an e-textile microstrip patch antenna was designed and data were collected under similar environmental and wear conditions. RF performance change corresponds with DC performance change. The findings of this paper highlight limitations of the evaluated e-textile performance, and provide new perspectives regarding improvements to e-textile fabrication for sustaining performance through environmental and wear operations.