RF Front-end Research Articles

Design of a Novel SiP Integrated RF Front-End Module Based on SOI Switch and SAW Filter.

This paper proposes a novel System-in-Package (SiP) integrated architecture that incorporates Silicon-On-Insulator (SOI) switches and Surface Acoustic Wave (SAW) filters within the chip, aiming to fulfill the demands for miniaturization and multi-functionality for application in emerging wireless technologies. The proposed architecture not only reduces the integration complexity but also considers the architectural design of the integrated module, impedance matching techniques, and signal integrity for carrier aggregation (CA) technology realization. The feasibility of employing SOI switches and SAW filters based on SiP design has been validated through the trial production of a Sub-3GHz radio frequency (RF) front-end diversity receiver module. The resulting RF front-end module demonstrates exceptionally high packaging density and enhanced communication reliability, rendering it suitable for diverse applications in miniaturized RF systems.

Few‐shot cross‐receiver radio frequency fingerprinting identification based on feature separation

AbstractRadio frequency fingerprint identification (RFFI) is a widely used technique for authenticating equipment. It identifies transmitters by extracting hardware defects found in the RF front end. Recent research has focused on the impact of transmitters and wireless channels on radio frequency fingerprint (RFF). Most work is based on the same receiver assumption, while the influence of the receiver on RFF remains unresolved. This paper focuses on the impact of receiver hardware characteristics on RFF and proposes a few‐shot cross‐receiver RFFI method based on feature separation. Data augmentation with noise addition and simulated channels addresses sparse sample issues and enhances the model's robustness to channel variations. Simultaneously, feature separation is realized by reducing the correlation between transmitter and receiver features through classification loss and similarity loss. We evaluate the proposed approaches using a large‐scale WiFi dataset. It is shown that when a trained transmitter classifier is deployed on new receivers with only 30 samples per trained transmitter, the average identification accuracy of the proposed method is 83.6%. This accuracy is 9.45% higher than the baseline method without considering transmitter hardware influence. After fine‐tuning, the average identification accuracy can reach 98.25%.

Bulk acoustic wave—Solidly mounted resonator with a-SiOCN:H as low-Z material

Bulk acoustic wave (BAW) filters have been proven to be of high demand in today's low power RF front-ends for mobile communication devices. Within the launch of 5G applications worldwide, especially in the region of new radio (nr-1) up to 6 GHz, defined frequency bands require filters of wide bandwidths, while simultaneously featuring steep edges and high out-of-band rejection. Due to the coexistence with 4G LTE (long term evolution) wireless standards as well as advanced data transfer concepts such as carrier aggregation, the increasing complexity of antenna systems forces the implementation of highly selective acoustic filters. In contrast to the widely used surface acoustic wave (SAW) technology, BAW filters appear with superior performance for frequencies above 1 GHz. This work describes the fabrication of a BAW-solidly mounted resonator (BAW-SMR) with a tailored material system of a-SiOCN:H as a low impedance (low-Z) material integrated within its acoustic Bragg mirror. A direct comparison to the widely used low-Z material of SiO2 with an acoustic impedance of around 13 MRayl is demonstrated by two equal resonator stacks by replacing only the uppermost low-Z thin film of the acoustic reflector. A single-mask design was chosen with platinum as a bottom electrode to ensure the most equal growth conditions for the piezoelectric aluminum nitride (AlN) layers on both reflectors’ surfaces featuring either the tailored a-SiOCN:H or standard SiO2. The a-SiOCN:H thin films were deposited by plasma-enhanced chemical vapor deposition and the according acoustic impedance was priorly depicted to 7.1 MRayl, which could be exploited to achieve an increase in the effective coupling coefficient beyond 7% as well as a resonator bandwidth of more than 60 MHz.

Analyzing the Indirect Effects of Lightning on Unmanned Aerial Vehicle Navigation Receivers

To investigate the interference effects of lightning on unmanned aerial vehicle (UAV) navigation receivers, an analytical approach for the evaluation of indirect lightning effects is suggested. The blocking mechanism of lightning pulses on the receiver is analyzed using the vector method. A behavioral-level simulation model of the receiver’s radio frequency (RF) front-end is constructed, and a lightning pulse injection simulation is performed based on the advanced design system (ADS). The simulation results indicate that lightning pulses induce blocking interference on the RF front-end of the navigation receiver, reducing its sensitivity and dynamic range. This interference is attributed to gain compression and degradation of the noise figure in the low-noise amplifier (LNA). To further validate the simulation results, a pin injection test is carried out to examine the influence of lightning pulses with different peak voltages on receiver sensitivity. The test results indicate a notable reduction in the receiver sensitivity when the lightning pulse peak reaches 250 V. The sensitivity trends across various test panels are consistent, and the damage thresholds are similar. These findings confirm the accuracy of the simulation results.

Gold as a Promising Electrode Material for LiNbO3-on-Insulator (LNOI) SH-SAW Resonators: An Experimental Study.

The need for wideband radio frequency front ends (RFFEs) with next-generation wireless protocols highlights the importance of electromechanical coupling [Formula: see text]. The hetero acoustic layered (HAL) surface acoustic wave (SAW) resonator with aluminum (Al) electrodes has shown superior performance compared to conventional SAW devices. Despite gold (Au) having excellent conductivity and stable properties, its high acoustic absorption and low phase velocity have made it less favorable for electrodes. This work demonstrates that high-performance shear horizontal (SH)-SAW resonators can be fabricated on the lithium niobate-on-insulator (LNOI) platform using a setup specifically designed for an Au electrodes. Experimental validation shows that the device achieves a high quality factor (Q) over 870, excellent [Formula: see text] up to 40%, and operates around 765 MHz. Unwanted transverse spurious modes are suppressed through adequate electrode design, and the temperature stability of LNOI SH-SAW with Au electrodes is discussed. This study highlights gold's potential as an electrode material for high [Formula: see text], clean spectrum, and wideband applications.

Isolation enhancement of a capacitively-fed MIMO antenna using a quasi-fractal parasitic element and defected ground structure

Vehicular Internet of Things (IoT) is facilitated by efficient RF front ends with suppressed mutual coupling for enhanced spatial diversity and increased channel capacity. This paper presents a mutual coupling suppressed MIMO antenna with a hybrid decoupling technique for Vehicle-to-Everything (V2X) communications, enabling IoT in automotive systems. The single elements consist of a radiating patch with a cleaving circular slot to introduce a capacitive effect on the radiating structure. Afterwards, the single-unit design is further extrapolated to a 2 × 2 MIMO antenna. The mutual coupling is suppressed between antenna elements by introducing a quasi-fractal parasitic element and a defected ground structure (DGS). The MIMO antenna is designed to conform to the requirements posed by V2X systems in Dedicated Short-Range Communications (DSRC) and Intelligent transportation system (ITS) scenarios. The proposed MIMO antenna offers measured |S11| < −10 dB of 200 MHz, ranging from 5.77 GHz to 5.97 GHz, fully covering the spectrum guided by the IEEE 802.11p standard. A physical prototype is fabricated and placed on a car roof to assess the congruency between measured and simulated results. The MIMO antenna exhibits exceptional diversity properties, such as enhanced isolation (>28 dB) between its individual elements, a diversity gain (DG) close to the ideal value of 10 dB (9.99 dB), peak realized gain of 6.5 dBi, an ECC below 0.001, and a beam coverage area of 180° in azimuthal and elevation plane by dynamic port switching. Thus, the proposed MIMO antenna module is a considerable candidate for future V2X communication paradigms.

An Adaptive RF Front-End Architecture for Multi-Band SDR in Avionics.

This study introduces a reconfigurable and agile RF front-end (RFFE) architecture that significantly enhances the performance of software-defined radios (SDRs) by seamlessly adjusting to varying signal requirements, frequencies, and protocols. This flexibility greatly enhances spectrum utilization, signal integrity, and overall system efficiency-critical factors in aviation, where reliable communication, navigation, and surveillance systems are vital for safety. A versatile RF front-end is thus indispensable, enhancing connectivity and safety standards. We explore the integration of this flexible RF front-end in SDRs, focusing on the detailed design of essential components, such as receivers, transmitters, RF switches, combiners, and splitters, and their corresponding RF pathways. Comprehensive performance evaluations confirm the architecture's reliability and functionality, including an extensive analysis of receiver gain, linearity, and two-tone test results. These assessments validate the architecture's suitability for aviation radios and address considerations of size, weight, and power-cost (SWaP-C), demonstrating significant gains in operational efficiency and cost-effectiveness. The introduction of the new RF front-end on a single SDR board not only substantially reduces size and weight but also adds up to 18 dB gain to the received signal. It also allows for a high level of design flexibility, enabling seamless software transitions between different radios and the capacity to manage three times more radios with the same hardware, thereby significantly boosting the system's ability to handle multiple radio channels efficiently.

Enhancing internet of things security using entropy-informed RF-DNA fingerprint learning from Gabor-based images

Internet of Things (IoT) deployments are anticipated to reach 29.42 billion by the end of 2030 at an average growth rate of 16% over the next 6 years. These deployments represent an overall growth of 201.4% in operational IoT devices from 2020 to 2030. This growth is alarming because IoT devices have permeated all aspects of our daily lives, and most lack adequate security. IoT-connected systems and infrastructures can be secured using device identification and authentication, two effective identity-based access control mechanisms. Physical Layer Security (PLS) is an alternative or augmentation to cryptographic and other higher-layer security schemes often used for device identification and authentication. PLS does not compromise spectral and energy efficiency or reduce throughput. Specific Emitter Identification (SEI) is a PLS scheme capable of uniquely identifying senders by passively learning emitter-specific features unintentionally imparted on the signals during their formation and transmission by the sender’s radio frequency (RF) front end. This work focuses on image-based SEI because it produces deep learning (DL) models that are less sensitive to external factors and better generalize to different operating conditions. More specifically, this work focuses on reducing the computational cost and memory requirements of image-based SEI with little to no reduction in performance by selecting the most informative portions of each image using entropy. These image portions or tiles reduce memory storage requirements by 92.8% and the DL training time by 81% while achieving an average percent correct classification performance of 91% and higher for SNR values of 15 dB and higher with individual emitter performance no lower than 87.7% at the same SNR. Compared with another state-of-the-art time-frequency (TF)-based SEI approach, our approach results in superior performance for all investigated signal-to-noise ratio conditions, the largest improvement being 21.7% at 9 dB and requires 43% less data.

(Invited) Low-Frequency Noise in Flexible Carbon-Nanotube Analog Circuits

Since flexible devices can come into close contact with the human body, they are suitable for wearable sensor applications for long-term and non-invasive monitoring of biological and physiological signals in various fields such as medical/health care and sports, among others. In order to achieve a fully flexible sensor system, various electronic circuits need to be integrated on a flexible film, including the analog frontend (AFE) and radio-frequency (RF) frontend, as well as the sensors. Recently, we have demonstrated low-voltage CNT-based analog/digital mixed-signal circuits with excellent stability and robustness against variability, including the AFE. One remaining issue with CNT-based analog circuits is low-frequency noise, which directly impacts the sensitivity of the sensor system within the frequency range of physiological signals such as ECG and EEG.Here, we study the low-frequency noise of flexible carbon nanotube thin-film transistors and their influence on analog circuits. The low-frequency noise exhibits a typical 1/f spectrum. Inserting an interface layer between the CNT channel layer and gate insulator layer reduces Hooge's parameter of the 1/f noise. The results indicate that maintaining distance from the channel to traps in the gate oxide is important for reducing low-frequency noise.

AI-DRIVEN TRANSFORMER NETWORKS IN SHARED SPECTRUM FOR ENHANCED SIGNAL PROCESSING FOR NONLINEAR RECEIVERS

Communication systems face challenges from high-power adjacent channel signals, or blockers, inducing nonlinear behavior in RF front ends. Ensuring robust performance in the presence of blockers is crucial for IoT and other spectrum-consuming devices coexisting with advanced transceivers. This paper proposes a flexible, data-driven solution using a Deep Belief Network (DBN) to mitigate third-order intermodulation distortion (IMD) during demodulation. Numerical evaluations of AI-enhanced receivers employing DBN as an IMD canceler and demodulator show significant improvements in bit error rate (BER) performance. The effectiveness of DBN varies with RF front end characteristics, notably the third-order intercept point (IP3).

Ultrawideband Modular RF Frontend Development for Photonically Enabled Imaging Receiver

Ultrawideband Modular RF Frontend Development for Photonically Enabled Imaging Receiver

CMOS IC Solutions for the 77 GHz Radar Sensor in Automotive Applications

This paper presents recent results on CMOS integrated circuits for automotive radar sensor applications in the 77 GHz frequency band. It is well demonstrated that nano-scale CMOS technologies are the best solution for the implementation of low-cost and high-performance mm-wave radar sensors since they provide high integration level besides supporting high-speed digital processing. The present work is mainly focused on the RF front-end and summarizes the most stringent requirements of both short/medium- and long-range radar applications. After a brief introduction of the adopted technology, the paper addresses the critical building blocks of the receiver and transmitter chain while discussing crucial design aspects to meet the final performance. Specifically, effective circuit topologies are presented, which concern mixer, variable-gain amplifier, and filter for the receiver, as well as frequency doubler and power amplifier for the transmitter. Moreover, a voltage-controlled oscillator for a PLL efficiently covering the two radar bands is described. Finally, the circuit description is accompanied by experimental results of an integrated implementation in a 28 nm fully depleted silicon-on-insulator CMOS technology.

LOW POWER DESIGN AND ANALYSIS OF ADAPTIVE RADIOS

This undertaking presents a noteworthy low-power procedure, RF Power Gating, proposing a unique change of the Dynamic Time Proportion (ATR) inside the RF front end at an image time scale. Adapting receiver power consumption to performance requirements without altering the fundamental architecture is the unique challenge that this method addresses. The effect of changing the ATR on the performance of the Bit Error Rate (BER) is carefully examined, with a focus on minimum-shift keying signaling and a basic estimator. To gauge power decrease unequivocally, a complete framework level energy model is determined, considering the qualities and power utilization of individual blocks. This model gives experiences into the particular supporters of force decrease. The review consolidates BER results with the energy model to pinpoint the ideal ATR meeting plan requirements. When this method is applied to the IEEE 802.15.4 standard, it can be seen that an ATR of 20% is a sensible compromise that meets the requirements for the packet error rate while also achieving the highest possible energy reduction ratio. Further investigation utilizing run of the mill block power utilizations uncovers a reachable energy decrease proportion of around 20%. Quite, while power-gating is widely applied, significantly more noteworthy energy decrease proportions (∼60%) are achievable. The proposed procedure is executed in Verilog, displaying its functional materialness, and consistently coordinated into Xilinx apparatuses. The outcomes highlight not just the viability of RF Power Gating in accomplishing a critical decrease in energy utilization yet additionally its versatility to different situations, making it a promising methodology for low-power plan in versatile radios. Key Words: Active Time Ratio (ATR) Blunder Rate (BER) and IEEE 802.15.4 standard.

A 22-mW 0.9-2-GHz mixer-first receiver 8-phase overlap-suppressed 1/4 duty cycle LO for harmonic rejection

This paper presents a mixer-first wideband receiver front-end designed to achieve high linearity and harmonic rejection while minimizing power consumption. The proposed RF front-end adopts LO overlap suppression technology and uses 25 % duty cycle LO for 8-phase operation. In addition, the passive mixer with implicit capacitive stacking provides passive gain to the useful signal and improves harmonic rejection. The total power consumption of this work is less than 22 mW, the majority of which is consumed by the baseband amplifier and buffer, making it superior to existing active harmonic suppression RF front-ends in terms of low power consumption. The receiver is designed in TSMC 65-nm technology with an active area of 0.44 mm2 and is suitable for various communication standards from 0.9 GHz to 2 GHz. Post-layout simulation results show that < −15 dB S11, 16.7-dBm OOB-IIP3@80 MHz, 3.7–6.7 dB DSB-NF, 46.4–49.5 dB total system voltage gain and HRR3 of 35.4–42 dB are achieved. No active components are required for harmonic recombination.

LoRa Radio Frequency Fingerprinting with Residual of Variational Mode Decomposition and Hybrid Machine-Learning/Deep-Learning Optimization

Radio Frequency Fingerprinting (RFF) refers to the technique for identifying and classifying wireless devices on the basis of their physical characteristics, which appear in the digital signal transmitted in space. Small differences in the radio frequency front-end of the wireless devices are generated across the same wireless device model during the implementation and manufacturing process. These differences create small variations in the transmitted signal, even if the wireless device is still compliant with the wireless standard. By using data analysis and machine-learning algorithms, it is possible to classify different electronic devices on the basis of these variations. This technique has been well proven in the literature, but research is continuing to improve the classification performance, robustness to noise, and computing efficiency. Recently, Deep Learning (DL) has been applied to RFF with considerable success. In particular, the combination of time-frequency representations and Convolutional Neural Networks (CNN) has been particularly effective, but this comes at a great computational cost because of the size of the time-frequency representation and the computing time of CNN. This problem is particularly challenging for wireless standards, where the data to be analyzed is extensive (e.g., long preambles) as in the case of the LoRa (Long Range) wireless standard. This paper proposes a novel approach where two pre-processing steps are adopted to (1) improve the classification performance and (2) to decrease the computing time. The steps are based on the application of Variational Mode Decomposition (VMD) where (in opposition to the known literature) the residual of the VMD application is used instead of the extracted modes. The concept is to remove the modes, which are common among the LoRa devices, and keep with the residuals the unique intrinsic features, which are related to the fingerprints. Then, the spectrogram is applied to the residual component. Even after this step, the computing complexity of applying CNN to the spectrogram is high. This paper proposes a novel step where only segments of the spectrogram are used as input to CNN. The segments are selected using a machine-learning approach applied to the features extracted from the spectrogram using the Local Binary Pattern (LBP). The approach is applied to a recent LoRa radio frequency fingerprinting public data set, where it is shown to significantly outperform the baseline approach based on the full use of the spectrogram of the original signal in terms of both classification performance and computing complexity.

Dual-Frequency, Dual-Mode Reconfigurable Digital Atmospheric Radar Receiver Design

A new dual-frequency, dual-mode reconfigurable digital receiver based on Field-Programmable Gate Array (FPGA) dynamic reconfiguration is proposed, which is based on a common hardware platform of high-bandwidth RF front-end, high-speed data acquisition, and real-time signal processing. The receiver adopts the design of dynamically reconfigurable down-conversion, filter extraction, and matched filtering in the digital domain. In this study, we completed the design and development of the digital receiver, experimental platform construction, and field detection test with hardware and software cooperation. The experimental results show that the receiver achieves full digital reception and signal processing for 53.8 MHz stratosphere–troposphere (ST) detection and 35.0 MHz meteor detection and successfully acquired the number of meteors versus time, the meteor trail, and low-altitude atmospheric radial winds. This dual-frequency, dual-mode reconfigurable digital receiver can be applied to new-generation multifunction integrated radar systems such as dual-frequency ST/meteor radars.

Aluminium Scandium Nitride Thin Film BAW Resonators (FBAR) for 5G Applications

With the growing impact of 5G communication system, Radio-Frequency Micro-Electro-Mechanical-Systems (RF MEMS) technologies are becoming increasingly important in our daily lives. Development of filters in the 5G frequency range is being carried out tremendously. The rapid rise in smartphone usage, heightened data demands, congestion in the frequency spectrum, and advancements in technology have posed numerous challenges for the development of RF filters. The ultimate goal is to simplify the RF Front End Module used in smart phones, thereby achieving better selectivity. In this paper, a high frequency - high Q thin film bulk acoustic wave resonator of piezoelectric material Aluminium scandium nitride (AlScN)based FBAR is designed for 5G Application. Finite element analysis conducted using the COMSOL Multiphysics software assess the characteristics of the constructed FBAR. The outcomes indicate that the device resonates effectively at 5 GHz, exhibiting commendable return loss and a Q-factor of 1490. A high-resonance-frequency FBAR device offers advantages for 5G mobile technology.

Design and Fabrication of 3.5 GHz Band-Pass Film Bulk Acoustic Resonator Filter.

With the development of wireless communication, increasing signal processing presents higher requirements for radio frequency (RF) systems. Piezoelectric acoustic filters, as important elements of an RF front-end, have been widely used in 5G-generation systems. In this work, we propose a Sc0.2Al0.8N-based film bulk acoustic wave resonator (FBAR) for use in the design of radio frequency filters for the 5G mid-band spectrum with a passband from 3.4 to 3.6 GHz. With the excellent piezoelectric properties of Sc0.2Al0.8N, FBAR shows a large Keff2 of 13.1%, which can meet the requirement of passband width. Based on the resonant characteristics of Sc0.2Al0.8N FBAR devices, we demonstrate and fabricate different ladder-type FBAR filters with second, third and fourth orders. The test results show that the out-of-band rejection improves and the insertion loss decreases slightly as the filter order increases, although the frequency of the passband is lower than the predicted ones due to fabrication deviation. The passband from 3.27 to 3.47 GHz is achieved with a 200 MHz bandwidth and insertion loss lower than 2 dB. This work provides a potential approach using ScAlN-based FBAR technology to meet the band-pass filter requirements of 5G mid-band frequencies.

Plasma-enhanced chemical vapor deposition a-SiOCN:H low-Z thin films for bulk acoustic wave resonators

The 5th generation (5G) wireless telecommunication standards with newly defined frequency bands up to 6 GHz are currently established around the world. While outperforming surface acoustic wave (SAW) filters above 1 GHz, bulk acoustic wave (BAW) resonators in multiplexers for radio-frequency front-end (RFFE) modules continuously face higher performance requirements. In contrast to free-standing bulk acoustic resonators (FBARs), solidly mounted resonator (SMR) technology uses an acoustic Bragg mirror, which has already been successfully applied for several GHz applications. In this work, we investigate the potential of amorphous hydrogenated silicon-oxycarbonitride (a-SiOCN:H) thin films synthesized with low-temperature plasma-enhanced chemical vapor deposition (PECVD) as a low acoustic impedance (low-Z) material. Compared to the state-of-the-art where in Bragg mirrors up to now SiO2 is used as standard, the acoustic impedance ratio against the high-Z material tungsten (W) is enhanced for a better device performance. To limit the expected increase in viscous loss when the acoustic impedance is reduced, to a minimum, predominantly the mass density was reduced while keeping the mechanical elasticity high. By doing so, acoustic impedance values as low as 7.1 MRayl were achieved, thereby increasing the impedance ratio of high-Z to low-Z materials from 8:1 up to 14:1.

A 0.5–15 GHz reconfigurable IR-UWB receiver in 28 nm CMOS

A 0.5–15 GHz ultra-wideband (UWB) RF reconfigurable receiver in UMC 28 nm CMOS used for IR-UWB (impulse radio UWB) radar system is proposed in this paper. This receiver employs a 0.5–8 GHz path and an 8–15 GHz path to achieve the wide frequency band, and we proposed an RF channel select voltage-to-time converter (VTC) circuit. Two different low noise amplifiers (LNAs) are adopted in the two paths to obtain the high performance of noise figure (NF) and gain. The common drain stage and resistance negative feedback technology as well as the source degeneration inductive technology are introduced to achieve a high flat gain and fine input matching. The R-2R variable load network of a programable gain amplifier (PGA) gives it a nearly 24 dB dynamic range and approximately linear gain control. A 500MS/s time domain analog to digital converter (TD-ADC) with an equivalent sampling rate of 16GS/s is shared for the two paths which can realize the direct RF sampling. The input RF signal path selection is implemented by configuring the Band_sel signal. The receiver has reconfigurability of the RF front end and better power consumption and area. In the frequency of 0.5–8 GHz, the S11 is below −7.9 dB and the NF is smaller than 6 dB. In the frequency of 8–15 GHz, the S11 is below −8dB and the NF is smaller than 11 dB. The receiver dissipates 242.72mW with an area of 1.01 mm2