Short-range Applications Research Articles

A Low-Power Optoelectronic Receiver IC for Short-Range LiDAR Sensors in 180 nm CMOS.

This paper presents a novel power-efficient topology for receivers in short-range LiDAR sensors. Conventionally, LiDAR sensors exploit complex time-to-digital converters (TDCs) for time-of-flight (ToF) distance measurements, thereby frequently leading to intricate circuit designs and persistent walk error issues. However, this work features a fully differential trans-impedance amplifier with on-chip avalanche photodiodes as optical detectors so that the need of the following post-amplifiers and output buffers can be eliminated, thus considerably reducing power consumption. Also, the combination of amplitude-to-voltage (A2V) and time-to-voltage (T2V) converters are exploited to replace the complicated TDC circuit. The A2V converter efficiently processes weak input photocurrents ranging from 1 to 50 μApp which corresponds to a maximum distance of 22.8 m, while the T2V converter handles relatively larger photocurrents from 40 μApp to 5.8 mApp for distances as short as 30 cm. The post-layout simulations confirm that the proposed LiDAR receiver can detect optical pulses over the range of 0.3 to 22.8 m with a low power dissipation of 10 mW from a single 1.8 V supply. This topology offers significant improvements in simplifying the receiver design and reducing the power consumption, providing a more efficient and accurate solution that is highly suitable for short-range LiDAR sensor applications.

A high-performance sub-THz planar antenna array for THz sensing and imaging applications

Terahertz (THz) spectral region from 0.1 to 3 THz is envisaged to hold immense potential in the next generation of wireless technologies. Recently, research has focused on this terahertz gap, because of its unprecedented channel capacities. At the physical layer, the design complexities and fabrication of THz devices, especially antennas are the prime bottlenecks to realize its full potential. This article introduces a cost-effective, easy-to-fabricate, and reproducible sub-THz antenna design based on a single-layer planar printed circuit board technology. The antenna incorporates carefully designed quasi-cross slots and applied machine learning-assisted global optimization techniques to achieve the desired performance metrics. The antenna performance is elucidated through numerical simulations and verified through a rigorous in-house THz experimental framework around 100–110 GHz. The proposed antenna offers a peak gain of 13.90 dBi with less than 1 dB variation within the entire band of 100–110 GHz. The antenna holds the potential to achieve terabits per second data rates and futuristic high-resolution short-range THz imaging applications.

Exploring Design Tradeoffs and Rate Gain Regions in Full-Duplex Wireless Communications

Conventional HD wireless networks operated by using distinct time slots or frequency (freq.) sub-bands for transmission and reception within the same family. Therefore, the wireless research community aims to develop FD operation to enable simultaneous transmission along with reception inside a single time/ freq. channel. This research aims to conduct an analytical investigation of the conditions under which real FD systems may attain higher data rates compared to analogous HD systems. The primary obstacle in real FD systems is to the uncancelled self-interference (SI) signal, which arises due to a confluence of hardware along with implementation defects. First, provide a signal model that encompasses the impact of notable impairments, including oscillator phase noise (PN), along with low-noise amplifier (LNA) noise figure, along with mixer noise, along with analog-to-digital converter quantization noise. The rate gain area (RGA) is examined in this research using the comprehensive signal model. A~1.2x to ~1.4x that of HD systems for short-range applications like class-3 Bluetooth. To get the same rate gain with Class-1 Bluetooth, −70dB in-band PN must be paired with 50dB passive SI suppression.

Coverage Performance of Non-Lambertian Underwater Wireless Optical Communications for 6G Internet of Things

In medium- and short-range underwater application scenarios, thanks to the superior performance in transmission bandwidth, link latency, and security, underwater wireless optical communication (UWOC) is growing to be a promising complement to the mature underwater acoustic communication technique. In order to extend the future 6G Internet of Things (IOT) to various challenging and valuable underwater scenarios, the underwater spatial coverage and transmission performance has been actively discussed in typical seawater environments. However, almost all current works focus on underwater scenarios including light-emitting diode (LED) transmitters with well-known Lambertian optical beams and fail to characterize the scenarios adopting LED transmitters with distinctive non-Lambertian beam patterns. For addressing this limitation, in this article, the coverage performance of non-Lambertian UWOC for 6G is analyzed and illustrated. Furthermore, the switchable optical beam configuration scheme is proposed and estimated for UWOC. Numerical results illustrate that, compared with about 15.42 dB signal-to-noise ratio (SNR) fluctuation amplitude for UWOC with baseline Lambertian optical beam configuration, the corresponding SNR fluctuation amplitudes of UWOC based with two typical non-Lambertian optical beams are 8.71 dB and 24.60 dB. Furthermore, once the receiver depth is increased to 6.0 m, the SNR fluctuation amplitude for the above three UWOC coverage with distinct beam configuration could be reduced to 5.61 dB, 1.58 dB, and 10.33 dB, respectively.

A Novel Approach to Raman Distributed Temperature-Sensing System for Short-Range Applications.

A novel approach to the development of Distributed Temperature-Sensing (DTS) systems based on Raman Scattering in Multimode optical fibers operating at around 800 nm is presented, focusing on applications requiring temperature profile measurement in the range of a few hundreds of meters. In contrast to the standard Raman DTS systems, which aim to shorten the pulse space width as much as possible to improve the precision of measurement, the novel approach studied in this work is based on the use of pulses with a space width that is approximately equal to the distance covered by the fiber under test. The proposed technique relies on numerical post-processing to obtain the temperature profile measurement with a precision of about ±3 °C and a spatial resolution of 8 m, due to the transaction phases of the optical pulses. This solution simplifies the electronic circuit development, also minimizing the required laser peak power needed compared to the typical narrow pulse techniques.

Harmonic FMCW Radar System: Passive Tag Detection and Precise Ranging Estimation.

This paper details the design and implementation of a harmonic frequency-modulated continuous-wave (FMCW) radar system, specialized in detecting harmonic tags and achieving precise range estimation. Operating within the 2.4-2.5 GHz frequency range for the forward channel and 4.8-5.0 GHz for the backward channel, this study delves into the various challenges faced during the system's realization. These challenges include selecting appropriate components, calibrating the system, processing signals, and integrating the system components. In addition, we introduce a single-layer passive harmonic tag, developed specifically for assessing the system, and provide an in-depth theoretical analysis and simulation results. Notably, the system is characterized by its low power consumption, making it particularly suitable for short-range applications. The system's efficacy is further validated through experimental evaluations in a real-world indoor environment across multiple tag positions. Our measurements underscore the system's robust ranging accuracy and its ability to mitigate self-interference, showcasing its significant potential for applications in harmonic tag detection and ranging.

Characterizations for eWLB (Embedded Wafer Level Ball Grid Array) Antenna in Molded Package Integrations in 77GHz Automotive Applications

The worldwide IC market has had a significant growth rate in recent years, driving diversified package solutions in the segments of communication, computing, consumer, automotive, industrial, etc. Among these market segments, the automotive market is forecast to have the strongest CAGR (Compound Annual Growth Rate) of any of the end-use segments in the next 5 years, which results in more IC packages and components being designed into automotive vehicle systems such as infotainment, ADAS (Advance Driving Assistance System), instrumentation, body systems, battery control systems and so on. In these applications, the 77GHz short-range radar sensor application that can enable higher EIRP (Effective Isotropic Radiated Power) and adaptive cruise control performance has become more attractive to be commercialized. Due to the benefits of shorter interconnection length, lower conductive loss with smooth Cu surface as well as a lower dielectric constant and dielectric loss of materials in a fan-out wafer level package (FOWLP) technology, the FOWLP is proven as a suitable packaging solution to achieve the high speed and frequency requirements in 5G and mmWave applications. The eWLB Embedded Wafer Level Ball Grid Array) is a versatile FOWLP technology, providing a robust package platform in a space-efficient design with the very dense interconnection and routing of multiple dies as well as a smaller footprint and lower package profile providing a reliable package solution. Meanwhile, since the utilization of an antenna that is integrated into the packages has been studied as a lowcost solution because the packages can be tested in normal FR4 printed circuit board (PCB) instead of the RF function integrated PCB, the eWLB integrated with molded antenna chip packages (called eWLB antenna in molded package) technology is introduced in this paper. The characterizations for assembly process challenges are evaluated and illustrate the process optimizations of equipment handling, antenna molded chip package fabrication, reconstitution process control and warpage characterization of the molded wafer. In addition, the radio frequency (RF) test validation is performed to verify the performance of scattering parameter (S-parameter), radiation pattern, impedance and detection range of the antenna. In order to prove the reliable quality and yield of the evaluated eWLB antenna in molded packages, package-level reliability tests are studied. Through these results, it will show that this eWLB antenna in molded package integration is a robust and costeffective solution for 77GHz automotive applications.

Geometric lightguide for near-eye light field displays.

Most near-eye displays with one fixed focal plane suffer from the vergence-accommodation conflict and cause visual discomfort to users. In contrast, light field displays can provide natural and comfortable 3D visual sensation to users without the conflict. This paper presents a near-eye light field display consisting of a geometric lightguide and a light field generator, along with a collimator to ensure the light rays propagating in the lightguide are collimated. Unlike most lightguides, which reduce thickness by employing total internal reflection that can easily generate stray light, our lightguide directly propagates light rays without total internal reflection. The partially reflective mirrors of the lightguide expand the exit pupil to achieve an eyebox of 13m m(h o r i z o n t a l)×6.5m m(v e r t i c a l) with an eye relief of 18mm. The collimator and the light field generator, both having effective focal lengths different in the horizontal and vertical directions, are designed to provide a 40-deg diagonal field of view. The working range of the light field generator, which is 30cm to infinity, is verified qualitatively and quantitatively by experiments. We optimize the illuminance uniformity and analyze the illuminance variation across the eyebox. Further, we minimize the ghost artifact (referring to the split-up of light fields replicated by the partially reflective mirrors) by orienting the partially reflective mirrors at slightly different angles to enhance the image quality for short-range applications such as medical surgery.

Conformal ultra-compact narrowband 60.0 GHz four-port millimeter wave MIMO antenna for wearable short-range 5G application

Conformal ultra-compact narrowband 60.0 GHz four-port millimeter wave MIMO antenna for wearable short-range 5G application

Ultra-Wide band radar and its applications

This paper uses MATLAB software to demonstrate the performance of UWBSAR and conducts a comparative study with data obtained from conventional radar. It compares various antennas that support UWB, such as Vivaldi, MIMO, and monopole antennas, analyzed using SIMULINK. The paper discusses the design of UWBSAR to provide a comprehensive analytical picture of the processed images. The focus is on frequency domain analysis in general and the Range Migration Algorithm (RMA) in particular. The data obtained after signal processing is recorded to estimate the crossrange resolution, which is then compared with conventional SAR. The cross-range resolution estimated using UWBSAR is found to be lower than that of conventional radar, proving that UWBSAR is a better alternative for obtaining sharper images in short-range applications. High-quality images are reconstructed using a combination of UWB radar, SAR processing, and proposed algorithms to improve image quality. The investigation includes positive image generation to enhance sharpness and near-field imaging procedures. This paper also describes Ultra-Wideband (UWB) Synthetic Aperture Radar (SAR) and its application in operating at low frequencies to detect obscured targets beneath foliage. While it has obvious military applications, it also has civilian uses, such as in geophysical studies and weather forecasting. Several applications have been identified for both military and civilian environments.

Design of an edge-truncated patch antenna (ETPA) for near-range vehicular RADAR applications

In recent years, the evolution of vehicular safety systems and the burgeoning field of autonomous vehicles have underscored the need for advanced radar solutions tailored to these specific applications. By addressing this need, this paper presents an innovative radar antenna design—the Edge Truncated Patch Antenna (ETPA) integrated with a Complementary Split Ring Resonator (CSRR). Distinct from prevalent designs, our novel approach hinges on the unique properties of the CSRR to impart broad-spectrum characteristics to the antenna. This innovation culminates in the realization of an ultra-wide bandwidth of 6.24 GHz, which effectively spans from 24.03 to 30.27 GHz. This bandwidth alignment with the primary frequency range predominantly used in short-range vehicular RADAR applications positions the ETPA as a frontrunner in this domain. A noteworthy feature of our design is its compactness. With dimensions of 5.1 × 4.7 × 0.8 mm3, the proposed antenna stands out as one of the most space-efficient and performance-oriented designs in the contemporary literature. The rigorous simulation processes employed revealed an impressive consistency when juxtaposed with measured outcomes. Minor variations between the two are attributed to inevitable fabrication and soldering nuances. Our design process, from the initial conception to the final product, underscores the pivotal role of meticulous parameter optimization and innovative integration of the CSRR. In conclusion, the proposed ETPA, with its enhanced bandwidth, compact footprint, and consistent performance, establishes a new benchmark in the field.

An optimized LSTM-based equalizer for 100 Gigabit/s-class short-range fiber-optic communications

<p>Intensity modulation/direct detection (IM/DD) remains to be the preferred optical transmission scheme for short-range applications for its simplicity of application, inexpensiveness, and small footprint. However, the impairments of low-cost device and fiber chromatic dispersion lead to the limitation of system performance when the data rate rises to 100 Gbps or higher. In this paper, we demonstrated that an equalizer using neural networks can effectively improve the transmission performance of high-speed IM/DD systems. An optimization of a long short-term memory (LSTM) structure in terms of network depth and distribution of neurons in hidden layers leads to an enhancement of the overall performance of the 50 Gbaud PAM4 communications. Furthermore, the results for a system using a LSTM-based equalizer give the better outcome than the traditional feed-forward equalizer (FFE) or artificial neural network (ANN)-based equalizer.</p>

PVT Analysis and Behavioral Modeling of Doherty and Envelope Tracking RF ULP Power Amplifiers using 65 nm CMOS Technology

This research encompasses both Process-Voltage-Temperature (PVT) considerations and behavioral modeling of two proposed Power Amplifier (PA) designs for wireless communication systems. Process variations, supply voltage changes, and temperature changes provide difficulties for the design and optimization of power amplifiers for wireless communication systems and may have a substantial influence on their effectiveness. PVT analysis and behavioral modeling have been conducted to address the aforementioned challenges and characterize the behavior and performance of the power amplifiers under real-world operating conditions. It investigates the impact of process variations, supply voltage variations, and temperature variations on the performance of the PAs. The insights gained from this analysis contribute to a deeper understanding of the power amplifiers' performance, efficiency, and suitability for specific wireless communication standards, laying the foundation for future advancements in RF power amplifier design. The first design focuses on a Doherty PA (DPA) tailored for low-power short-range applications complying with the IEEE Wireless Personal Area Network (WPAN) standard. The second design explores an Envelope Tracking (ET) supply bias control for low-power long-range applications conforming to the IEEE Wireless Local Area Network (WLAN) standard. By examining these factors, the research ensures that the PAs exhibit reliable and optimal performance under real-world operating conditions. The PVT corners show a change in gain of only 0.4 dB for DPA and 0.9 dB for ET PA. Furthermore, behavioral modeling is employed to characterize the power efficiency of the envelope tracking PA, along with the current efficiency and quotient current on the load current scale. These models provide valuable insights into the behavior and performance of the PAs at a higher level of abstraction. The results and findings contribute to a deeper understanding of the PA’s performance, efficiency, and suitability for specific wireless communication standards, laying the foundation for future advancements in RF power amplifier design.

Millimeter-Wave and Short-Range Wireless Communication Antenna Based on High-Conductivity Graphene-Assembled Film.

Millimeter-wave and short-range wireless communication is an important part of the Internet of Things due to its advantages of high transmission speed and large data capacity. In this paper, two antenna arrays operating at typical millimeter-wave bands (45 and 60 GHz) based on graphene-assembled films (GAF) are proposed for short-range wireless communication application. The 45 GHz graphene-assembled film antenna array is in the form of a magnetoelectric dipole antenna with a strip slot coupling to achieve bidirectional radiation, which offers an operating bandwidth of 40-49.5 GHz with a realized gain of 11.8 dBi. The 60 GHz graphene-assembled film antenna utilizes a microstrip discontinuous radiation array to achieve radiation with an operating bandwidth of 59-64 GHz, reaching the peak realized gain of 14.92 dBi over the working frequency. Finally, we proposed an experimental validation to verify the transmission performance of both antenna arrays in an actual conference room. The results show that the signal drops slowly in the room with drop rates of 0.064 dB/cm (at 45 GHz) and 0.071 dB/cm (at 60 GHz), while it steeply dropped through the wall with the drop rates of 2.3 and 3.13 dB/cm, more than 35-fold difference in signal drop rates in the room and through the wall. It has been confirmed that the proposed antenna arrays can successfully realize fast indoor short-range wireless communication while also preventing signal leakage through walls, thereby enhancing the security of information. In summary, this is the first time that we have applied graphene-based materials to millimeter-wave and short-range wireless communications, revealing the significant potential of carbon-based materials in high-frequency communication systems.

Design and characterization of mesoscopic dielectric cuboid antenna for operation in WR-3.4 waveguide bandwidth (220–330 GHz)

We designed a mesoscopic dielectric cuboid antenna connected to a flangeless WR-3.4 open-ended waveguide, and the antenna characteristics at 300 GHz were examined through simulations and experiments. Simulations confirmed that the flangeless design eliminated the flange-induced ripples in the radiation pattern, whose shape varied with frequency, and that the antenna operated in the full bandwidth of the WR-3.4 waveguide (220–330 GHz). Prototypes were then fabricated based on the simulation findings. A prototype with an antenna aperture area of 1.5 mm times 1.5 mm and an antenna length of 2.35 mm exhibited an antenna gain of 17.2 dBi at 300 GHz and a voltage standing wave ratio of less than 1.5 throughout the WR-3.4 waveguide bandwidth. The level of the side lobes at about pm 30 degrees in the E-plane pattern was approximately -10 dB that of the main lobe. Therefore, the proposed antenna, connected to a flangeless waveguide, is a promising antenna for use in future short-range high-speed terahertz wireless applications such as kiosk downloads and board-to-board communication.

Enhancing isolation performance of tilted Beam MIMO antenna for short-range millimeter wave applications

The research paper discusses the detailed designing of a compact, simple, and low-profile antenna that provides several desirable features. The antenna is engineered by using a substrate material called Roger 6002, and its dimensions are 12 mm × 6 mm × 1.52 mm. The single antenna element achieves a wideband frequency coverage of 24–30.2 GHz and a high gain of 9 dBi. To enhance the antenna's capabilities, a two-port multiple-input multiple-output (MIMO) configuration is employed by adding a second antenna element orthogonal to the first one. Although the operational band remains the same, the isolation between the two elements is found to be unsatisfactory. A C-shaped decoupling structure is established to address this issue, which effectively improves the isolation. Including the parasitic patch enhances the isolation from −18 dB to −29 dB. An antenna hardware sample is built and tested to validate the recommended work, and the outcomes are compared to the predicted results obtained from the software. The experimental and simulated data exhibit close agreement, confirming the accuracy of the design. Additionally, this outstanding performance in bandwidth and isolation compares with existing literature, presented in the form of a table. Various MIMO parameters are also examined, and it is found that they fall within acceptable ranges. The antenna demonstrates an Envelope Correlation Coefficient (ECC) of approximately 0.005 and a Diversity Gain (DG) of around 9.99 dB. The recommended antenna design is highly suitable for future miniature devices used in Internet of Things (IoT) applications.

A miniaturized quintuple-band frequency selective surface based on enclosed cross slots

Abstract This article presents a low-profile quintuple-band frequency selective surface (FSS) that is designed as a sub-reflector for applications including satellite systems (C band), EPR (electron paramagnetic resonance) spectrometers, motion and traffic light crossing detectors (X band), Direct Broadcast Satellite and broadcasting satellite service (Ku band), and shortrange applications (K band). The dimensions of the miniaturized unit cell 0.08λ0×0.08λ0×0.012λ0, where, λ0 is the free-space wavelength corresponding to the lower cut-off frequency. There are five stop bands, and frequencies at which they resonate are 6.3, 7.06, 9.30, 11.2, 14.0, and 18.64 GHz. The fractional bandwidths (FBW) of these bands are 62.6, 7.5, 9.2, 11, and 11.69%, respectively. Additionally, as a result of the structure’s four-fold symmetry, it exhibits a good polarization-insensitive response as well as a stable response in both the TE and TM modes. Full-wave simulation is performed on the structure, after which an equivalent circuit model is constructed.

A novel reconfigurable H-plane Horn leaky wave Substrate Integrated Waveguide MIMO antenna for K band

In this paper a novel reconfigurable H-plane horn Multiple Input Multiple Output (MIMO) leaky wave substrate integrated waveguide (SIW) antenna is proposed. The antenna is operating at two resonant frequencies, 22.8 GHz and 26.32 GHz. The transverse periodic leaky wave slots are radiating power in the broadside direction at 22.8 GHz and pattern diversity is achieved at 26.32 GHz. Dielectric loading and an array of meta-material structures are used, which further improve gain of the antenna. The antenna achieves better matching with a return loss of –33.5 dB at 22.8 GHz and maximum isolation of −38.7 dB at 26.32 GHz is achieved between antenna elements. A 2x2 and 4x4 MIMO SIW antenna is designed and analyzed in this paper. All the MIMO performance measurement parameters have values within limits. The antenna achieves a maximum gain of 7.3 dBi and 8.1 dBi. The proposed antenna operates in the K band (18 GHz–27 GHz) region, making it suitable for automotive radars and short-range applications.

Two-Stage Link Loss Optimization of Divergent Gaussian Beams for Narrow Field-of-View Receivers in Line-of-Sight Indoor Downlink Optical Wireless Communication (Invited)

The predominant focus of research in high-speed optical wireless communication (OWC) lies in line-of-sight (LOS) links with narrow infrared beams. However, the implementation of precise tracking and steering necessitates delicate active devices, thereby presenting a formidable challenge in establishing a cost-effective wireless transmission. Other than using none-line-of-sight (NLOS) links with excessive link losses and multi-path distortions, the simplification of the tracking and steering process can be alternatively achieved through the utilization of divergent optical beams in LOS. This paper addresses the issue by relaxing the stringent link budget associated with divergent Gaussian-shaped optical beams and narrow field-of-view (FOV) receivers in LOS OWC through the independent optimization of geometrical path loss and fiber coupling loss. More importantly, the geometrical path loss is effectively mitigated by modifying the transverse intensity distribution of the optical beam using manipulations of multi-mode fibers (MMFs) in an all-fiber configuration. In addition, the sufficiently excited higher order modes (HOMs) of MMFs enable a homogenized distribution of received optical powers (ROPs) within the coverage area, which facilitates the mobility of end-users. Comparative analysis against back-to-back links without free-space transmission demonstrates the proposed scheme’s ability to achieve low power penalties. With the minimized link losses, experimental results demonstrate a 10 Gbps error-free (BER < 10−13) LOS OWC downlink transmission at 2.5 m over an angular range of 10° × 10° without using any optical pre-amplifications at a typical PIN receiver. The proposed scheme provides a simple and low-cost solution for high-speed and short-range indoor wireless applications.

A Novel Bow-Tie Balun-Fed Dual-Polarized Crossed Dipole Antenna

A broadband dual-polarized crossed dipole antenna is proposed in this paper. To achieve a wide impedance bandwidth and low-profile configuration, a novel bow-tie balun is applied to this antenna. Firstly, the working mechanisms of both bow-tie baluns and the antenna are introduced. Then, the parametric study and design guidelines are presented. Finally, the optimized antenna is fabricated, measured, and analyzed. The simulated and measured results show that the antenna has a wide impedance bandwidth from 2.42 GHz to 6.48 GHz. The fractional bandwidth is 91.2%. Moreover, within the whole band, the E-plane and H-plane radiation patterns are stable. The port isolation is greater than 20 dB, and the cross-polarization discrimination ratio is better than 25 dB. The proposed antenna achieves a realized gain of 7.5 dBi ± 0.5 dBi. It can be a good candidate for sub-6 GHz wireless communications or short-range radar applications.