High Bandwidth Signal Research Articles

M-ary quadrature amplitude modulation order optimization for terahertz wireless communications over dispersive channels

Highly accurate atmospheric models, based on molecular resonance information contained within the HITRAN database, were used to simulate the propagation of high capacity single-carrier quadrature amplitude modulated signals through the atmosphere for various modulation orders. For high-bandwidth signals such as those considered in this work, group velocity dispersion caused by atmospheric gases distorts the modulated waveform, which may produce bit errors. This leads to stricter Signal-To-Noise Ratio requirements for error-free operation, and this effect is more pronounced in high-order modulation schemes. At the same time, high-order modulation schemes are more spectrally efficient, which reduces the bandwidth required to maintain a given data rate, and thus reduces the total group velocity dispersion in the link, resulting in less distortion and better performance. Our work with M-ary quadrature amplitude modulated signals shows that optimal selection of modulation order can minimize these conflicting effects, resulting in decreased error rate, and reducing the performance requirements placed on any equalizers, other dispersion-compensating technologies, or signal processing hardware.

An Investigation about All-optical Millimeter Wave Generation Technology for High-speed Communication

With the advent of the network information age, users have higher and higher requirements for the bandwidth and capacity of communication systems. Traditional cellular mobile communications can no longer meet the needs of modern communication systems. It is necessary to find a communication system with larger capacity, higher bandwidth and higher transmission rate. Millimeter wave (MMW) communication has high bandwidth, large capacity and high signal transmission rate. Nowadays, all-optical MMW technology generates high-frequency MMW signals in optical domain, which has become a research hotspot of MMW signal generation technology at home and abroad. In this paper, three typical all-optical MMW generation methods are discussed, including direct modulation method, optical heterodyne method and external modulation method. The advantages and disadvantages of each method are analyzed, and the development prospects of the all-optical MMW generation technology are prospected. It is helpful to research new optical MMW technology in the future.

Performance analysis of LYSO–SiPM detection module for X-ray communication during spacecraft reentry blackout

In view of the demand for high-energy and high-bandwidth signal detection in X-ray communication (XCOM) during spacecraft reentry blackout, a detection module using fast-decay LYSO scintillator coupled with Silicon photomultiplier (SiPM) was proposed in this study. The theoretical model based on the Monte Carlo simulation and Personick’ theory was established and the detector prototype was built. Moreover, the signal to noise ratio (SNR) and bit error rate (BER) performance were investigated. Results present that the SNR of 19.8 dB, 29.9 dB and 35.5 dB could be reached for X-ray with the energy of 17 keV, 59.5 keV and 122 keV respectively. This energy response characteristic is much suitable for the X-ray signal detection during spacecraft reentry blackout. Additionally, the deviation of SNR corresponding to the BER between the theoretical and experimental results does not exceed 0.3 dB when the data rate is 100 kbps, which proves the validity of the theoretical model. Furthermore, the numerical analysis shows that the scheme demonstrates high SNR and low BER performance in high bandwidth and low signal receiving power, which explains the superiorities in X-ray signal detection of the design. This work provides the theoretical basis and design reference for the LYSO–SiPM X-ray signal detection module.

A survey on advanced transmission technologies for high bandwidth and good signal quality for high-speed railways

Ahigh-speedrailway (HSR) has gained very high popularity for passengersdue to the fast, reliable, economical and convenient during traveling a verylong-distance journey. Thedemandfor advancedbroadbandservices such aswatching4K movies, cloud computing andonline gaming, has exponentiallyincreased fortravelerson thehigh-speedtrain(HST).The HSTcan’t providegood bandwidth to facilitate these services for travelers via existingtechnologies such as cellular networksand satellite networks because offrequent handoffs, high penetration and fading.So, the bandwidth degradesdramatically due to these issues. Research workers have developed proposalsto handle these problems by advanced transmission technologies for HSR.Until now,varioustransmissionschemeshave beensuggestedby researchworks with thefocusfor either high bandwidth or signal qualityimprovement. This paper presents a survey on advanced transmissiontechnologies for high bandwidth and good signal quality. In this paper, acomprehensive survey of the appropriate literature published that concentrateon advanced transmission methods in HSR communications in getting higherbandwidth efficiency and maximize the signal quality is presented. Advancedtransmission method can be categorized into orthogonal frequencydivisionmultiplexing (OFDM), multiple-input multiple-output (MIMO) and radio-over-fiber (RoF).

A Software-Defined Always-On System With 57–75-nW Wake-Up Function Using Asynchronous Clock-Free Pipelined Event-Driven Architecture and Time-Shielding Level-Crossing ADC

This work presents an ultra-low-power software-defined always-on wake-up system to drastically decrease the system power of Internet of Things (IoTs) devices, which usually operate in random-sparse-event (RSE) scenarios. It mainly thanks to a clock-free time-shielding level-crossing ADC (TS-LCADC), software-defined clock-free multi-function detectors, and an asynchronous pipelined event-driven architecture. First, by quantifying RSE noisy signals with clock-free adaptive sampling in a signal-noise-rejecting manner, the proposed TS-LCADC reduces number of sampling points and power, and consumes only 41 nW when on-call waiting for IoT events. Second, the proposed clock-free multi-function detectors with offline and online programmability are able to character the signal features of versatile IoTs events and allow versatile and dynamic wake-up functions. Third, the proposed asynchronous pipelined event-driven architecture minimizes the system activity and thus power, because a power-hungry high-performance system (HPS) is only woken up when a detected parameter crosses its corresponding threshold. As such, the long-term average power (LTA-power) is dominated by the always-on circuits in RSE scenarios. The measurement results achieve 71-75 nW for three typical applications, i.e., heart rate, epilepsy, and keyword envelope detection. The LTA power is only 57 nW when waiting for RSE events, which is 30 × lower than a prior general-purpose wake-up chip. Compared with other works of dedicated voice and acoustic wake-up functions, this work consumes 2 × and 17 × less power, respectively, while featuring 16 × higher signal bandwidth and a broader versatility.

Real-time high-bandwidth mm-wave 5G NR signal transmission with analog radio-over-fiber fronthaul over multi-core fiber

This article presents an experimental demonstration of a high-capacity millimeter-wave 5G NR signal transmission with analog radio-over-fiber (ARoF) fronthaul over multi-core fiber and full real-time processing. The demonstration validates the core of the blueSPACE fronthaul architecture which combines ARoF fronthaul with space division multiplexing in the optical distribution network to alleviate the fronthaul capacity bottleneck and maintain a centralized radio access network with fully centralized signal processing. The introduction of optical beamforming in the blueSPACE architecture brings true multi-beam transmission and enables full spatial control over the RF signal. The proposed ARoF architecture features a transmitter that generates the ARoF signal and an optical signal carrying a reference local oscillator employed for downconversion at the remote unit from a single RF reference at the central office. A space division multiplexing based radio access network with multi-core fibre allows parallel transport of the uplink ARoF signal and reference local oscillator at the same wavelength over separate cores. A complete description of the real-time signal processing and experimental setup is provided and system performance is evaluated. Transmission of an 800 MHz wide extended 5G NR fronthaul signal over a 7-core fibre is shown with full real-time signal processing, achieving 1.4 Gbit/s with a bit error rate <3.8times 10^{-3} and thus below the limit for hard-decision forward error correction with 7% overhead.

Noise and distortion analysis of dual frequency comb photonic RF channelizers.

Dual frequency combs are emerging as highly effective channelizers for radio frequency (RF) signal processing, showing versatile capabilities in various applications including Fourier signal mapping, analog-to-digital conversion and sub-sampling of sparse wideband signals. Although previous research has considered the impact of comb power and harmonic distortions in individual systems, a rigorous and comprehensive performance analysis is lacking, particularly regarding the impact of phase noise. This is especially important considering that phase noise power increases quadratically with comb line number. In this paper, we develop a theoretical model of a dual frequency comb channelizer and evaluate the signal to noise ratio limits and design challenges when deploying such systems in a high bandwidth signal processing context. We show that the performance of these dual comb based signal processors is limited by the relative phase noise between the two optical frequency combs, which to our knowledge has not been considered in previous literature. Our simulations verify the theoretical model and examine the stochastic noise contributions and harmonic distortion, followed by a broader discussion of the performance limits of dual frequency comb channelizers, which demonstrate the importance of minimizing the relative phase noise between the two frequency combs to achieve high signal-to-noise ratio signal processing.

Multi-channel optical neuromorphic processor for frequency-multiplexed signals

Here we develop the first optical neuromorphic processor for frequency-multiplexed and multi-channel signals and demonstrate its application for orthogonal frequency-division multiplexing and wavelength-division multiplexing. The presented architecture supports multichannel operation through incorporation of the optical Fourier transform and dispersion-managed fiber echo state network analogue enabling processing of dual-quadrature high bandwidth signals. We demonstrate applicability of the design for prediction and equalization tasks. The proposed technology paves the way to multi-channel neuromorphic signal processing.

Multidimensional fiber echo state network analogue

Optical neuoromorphic technologies enable neural network-based signal processing through a specifically designed hardware and may confer advantages in speed and energy. However, the advances of such technologies in bandwidth and/or dimensionality are often limited by the constraints of the underlying material. Optical fiber presents a well-studied low-cost solution with unique advantages for low-loss high-speed signal processing. The fiber echo state network analogue (FESNA), fiber-based neuromorphic processor, has been the first technology suitable for multichannel high bandwidth (including THz) and dual-quadrature signal processing. Here we propose the multidimensional FESNA (MD-FESNA) processing by utilizing multi-mode fiber non-linearity. Thus, the developed MD-FESNA is the first neuromorphic technology which augments all aforementioned advantages of FESNA with multidimensional spatio-temporal processing. We demonstrate the performance and flexibility of the technology on the example of prediction tasks for hyperchaotic systems. These results will pave the way for a high-speed neuromorphic processing of multidimensional tasks, hardware for spatio-temporal neural networks and open new application venues for fiber-based spatio-temporal multiplexing.

Optical Spectral Slicing Based Reconfigurable and Tunable Microwave Photonic Filter

Multiband microwave photonic filters (MPFs) are extensively required in emerging multifunction RF systems and high-performance radar systems. In this article, we present a reconfigurable and tunable multiband MPF. The flexible amplitude and phase controls of the multiband MPF can be achieved via optical spectral slicing by way of a programmable sampling function, i.e., varying the number of samples or the duty cycle of each sample. We verify that the number of uniform passbands can be adjusted (we obtain up to six passbands) and demonstrate a frequency tuning range of up to 432 MHz for a uniform triple-passband MPF. We also show a highly chirped triple-passband MPF with respective in-band chirps up to 30.0 ns/GHz, 42.1 ns/GHz, and 22.8 ns/GHz. These latter results illustrate a potential way to implement highly chirped multiband MPFs for high bandwidth signal processing applications.

PN code tracking based on sub‐Nyquist and non‐commensurate sampling

Increasingly high bandwidths are desired in modern navigation and autonomous RF ranging signal design to achieve better pseudo-noise (PN) ranging accuracy. However, fulfilling the Nyquist criterion for such high-bandwidth signals would be a challenging issue for system design. Considering that the Nyquist criterion is not a necessary condition for PN code tracking, sub-Nyquist sampling can be adopted as a feasible solution to this issue. Nevertheless, it is at the expense of an increase in thermal noise caused by tracking error. This problem is particularly prominent for tracking weak signals such as navigation signals, which limits the applicability of this sampling scenario. As far as high-precision autonomous PN ranging is concerned, however, the tracking error due to digital implementation is not negligible and even becomes the dominating factor instead of thermal noise. This means that the performance loss incurred by sub-Nyquist sampling can be eliminated under high-signal-to-noise ratio conditions. Exploiting this fact, this Letter proposes a novel PN code tracking approach based on sub-Nyquist and non-commensurate sampling, providing a solution to achieving high-ranging accuracy while breaking the bounds of the Nyquist sampling theorem without performance degradation. The approach is very attractive for precise PN ranging applications demanding miniaturised implementation.

Inter and Intra-Cluster Networks Signal Coverage Impact and its Importance for Migration of 3G to 4G Network among Tourism Lake Tana in Bahir Dar -Ethiopia

Tourism is one of the leading economic sources for several countries compared to modern IT industries growth. Ethiopia is one of the leading cultural and tourism revenue-based country, and having huge tourism hot spots for national and international tourist visitors. Specifically, in the Amhara national regional state capital, Bahir Dar, Lake Tana (origin of Blue Nile River) has been very well known to national and international tourists. However, the Lake Tana Basin is still unable to provide sufficient high bandwidth and good signal reception though 3G wireless mobile technology service is deployed. Bandwidth constraint and weak signal strength is creating problems for the society residing and for visitors inand- around many islands of Lake Tana geographical areas. The research work carried out the study for 3G wireless mobile radio access and microwave transmission path link performance in the city and around Lake Tana Basin. Out of two phases of research works, in this paper, we focus the first phase and partly second phase research results for both Inter and Intra- Cluster 3G Network in complete manner. Hence, we analyzed various measures like coverage signal power conditions, various BTSs antenna sizes, geographical mapping issues and other supporting performance parameters. All importance analytical performance study and measures for two major cluster networks both inter and intra-cluster 3G Networks which are geographically located edging curve in and around Lake Tana Basin. Ultimately, complete analysis and results are supported as prime study for Ethiopian Telecommunication Corporation (ETC) technical support before expanding / migrating to 4G from 3G WCDMA network on Lake Tana Basin and also enhance the culture and tourism cost trade -off for both Amhara region of Ethiopia and national wide Ethiopia.

Rapid impedance spectroscopy using dual phase shifted chirp signals for electrochemical applications

Impedance is an important diagnostic feature finding applications in material science, analytical chemistry, understanding biological systems etc. This is particularly true for diagnosis of electrochemical systems such as fuel cells and storage batteries. However the conventional technique for impedance measurement, i.e. Electrochemical Impedance Spectroscopy (EIS), is time intensive and requires sophisticated instrumentation making it unsuitable for online applications. This paper introduces a novel technique that makes use of two high bandwidth and short duration signals having dissimilar phases to estimate impedance. A unique class of signal, viz. the dual phase shifted chirp signal, which comprises two identical chirp signals having a known phase difference, is used to obtain the impedance profile. The technique is validated through both, simulation as well as experiments. The results obtained from this work are in correspondence with those obtained through conventional EIS, albeit in a minuscule fraction of time and with meagre instrumentation. The proposed technique will pave way for a quick and cost effective alternative to EIS and allow for impedance measurement during operation.

An accurate UWB based localization system using modified leading edge detection algorithm

Ultra-wideband (UWB) localization systems have gained wide attention in precise indoor positioning applications, due to the usage of high bandwidth signals. We propose a modified leading edge detection algorithm for estimating the time of arrival (TOA) of the received UWB signal. The proposed method performs well even under low signal-to-noise ratio (SNR) conditions. We simulate a UWB localization system using the proposed algorithm and evaluate its performance under additive white Gaussian noise (AWGN). We study the influence of tuning parameters of the proposed algorithm on the positioning accuracy. We evaluate 1D and 2D positioning accuracies of the localization system using the optimal tuning parameters of the proposed algorithm. We further evaluate the performance of the proposed algorithm in multipath conditions. Simulation results show that the proposed algorithm provides enhanced positioning accuracy compared to the previously published methods including the state-of-the-art methods. We improve the positioning accuracy of the localization system further by deploying more base stations.

Up to 80 Gbaud DP‐16QAM operation using InP‐based high‐bandwidth coherent driver modulator

The authors obtained very good back-to-back bit error rate performance in up to 80 Gbaud DP-16QAM operation by using their coherent driver modulator of a 3-dB electro-optic bandwidth of over 50 GHz. To achieve high bandwidth and good signal integrity, they used double ultra-low loop wires between the driver IC and the modulator and a differential capacitively loaded travelling-wave RF electrode based on straight coupled coplanar waveguide with a ground-signal-signal-ground configuration for their InP modulator. As far as they know, this is the highest bandwidth and baud rate operation so far for the high-bandwidth coherent driver modulator configuration.

Maritime target imaging via simultaneous DVB‐T and DVB‐S passive ISAR

This work presents an analysis of passive inverse synthetic aperture radar images obtained exploiting simultaneously digital video broadcasting-terrestrial (DVB-T) and digital video broadcasting-satellite (DVB-S) as illuminators of opportunity (IOs) over a cooperative maritime target with known motion. The combined exploitation of these two IOs is extremely appealing for passive imaging purposes, given their complementary characteristics. The analysis is first conducted in a simulated environment, to show the different expected outcomes from the two considered bistatic geometries and operating bandwidths. Subsequently, the same analysis is repeated over real data acquired during a field trial, by exploiting experimental setups developed at Fraunhofer FHR. In particular, DVB-T and DVB-S data are focused by means of back projection, which enables an easier comparison of the different ISAR products. Real data results show good match with simulated ones. Target size can be estimated with good accuracy in both DVB-T and DVB-S cases, and dominant scatterers can also be identified. DVB-S also enables target-shape recognition, given its higher signal bandwidth.

Design and testing of a 96-channel neural interface module for the Networked Neuroprosthesis system

BackgroundThe loss of motor functions resulting from spinal cord injury can have devastating implications on the quality of one’s life. Functional electrical stimulation has been used to help restore mobility, however, current functional electrical stimulation (FES) systems require residual movements to control stimulation patterns, which may be unintuitive and not useful for individuals with higher level cervical injuries. Brain machine interfaces (BMI) offer a promising approach for controlling such systems; however, they currently still require transcutaneous leads connecting indwelling electrodes to external recording devices. While several wireless BMI systems have been designed, high signal bandwidth requirements limit clinical translation. Case Western Reserve University has developed an implantable, modular FES system, the Networked Neuroprosthesis (NNP), to perform combinations of myoelectric recording and neural stimulation for controlling motor functions. However, currently the existing module capabilities are not sufficient for intracortical recordings.MethodsHere we designed and tested a 1 × 4 cm, 96-channel neural recording module prototype to fit within the specifications to mate with the NNP. The neural recording module extracts power between 0.3–1 kHz, instead of transmitting the raw, high bandwidth neural data to decrease power requirements.ResultsThe module consumed 33.6 mW while sampling 96 channels at approximately 2 kSps. We also investigated the relationship between average spiking band power and neural spike rate, which produced a maximum correlation of R = 0.8656 (Monkey N) and R = 0.8023 (Monkey W).ConclusionOur experimental results show that we can record and transmit 96 channels at 2ksps within the power restrictions of the NNP system and successfully communicate over the NNP network. We believe this device can be used as an extension to the NNP to produce a clinically viable, fully implantable, intracortically-controlled FES system and advance the field of bioelectronic medicine.

Fiber echo state network analogue for high-bandwidth dual-quadrature signal processing.

All-optical platforms for recurrent neural networks can offer higher computational speed and energy efficiency. To produce a major advance in comparison with currently available digital signal processing methods, the new system would need to have high bandwidth and operate both signal quadratures (power and phase). Here we propose a fiber echo state network analogue (FESNA) - the first optical technology that provides both high (beyond previous limits) bandwidth and dual-quadrature signal processing. We demonstrate applicability of the designed system for prediction tasks and for the mitigation of distortions in optical communication systems with multilevel dual-quadrature encoded signals.

Bonded thin film lithium niobate modulator on a silicon photonics platform exceeding 100 GHz 3-dB electrical modulation bandwidth.

We demonstrate an ultra-high-bandwidth Mach-Zehnder electro-optic modulator (EOM), based on foundry-fabricated silicon (Si) photonics, made using conventional lithography and wafer-scale fabrication, oxide-bonded at 200C to a lithium niobate (LN) thin film. Our design integrates silicon photonics light input/output and optical components, such as directional couplers and low-radius bends. No etching or patterning of the thin film LN is required. This hybrid Si-LN MZM achieves beyond 106 GHz 3-dB electrical modulation bandwidth, the highest of any silicon photonic or lithium niobate (phase) modulator.

A Simple Envelope-Assisted RF/IF Digital Predistortion Model for Broadband RoF Fronthaul Transmission

For emerging 5G fronthaul, broadband radio over fiber (RoF) transmission has been found much more cost-effective than conventional digital fiber transmission. Current digital predistortion (DPD) techniques may not be effective in linearizing broadband RoF links. This work presents a simple envelope-assisted radio frequency (RF)/intermediate frequency (IF) DPD model for linearization of broadband/multiband RoF transmission. The model uses both RF/IF signals and baseband envelopes, resulting in the short-term and long-term memory effect mitigated efficiently even for high signal bandwidth. The model complexity is lower than the existing baseband DPDs and does not increase with the increase of the signal bands. The model is experimentally evaluated in three scenarios: two 20 MHz long-term evolution (LTE) signals spaced by 100 and 40 MHz, and three 20 MHz LTE signals spaced by 50 MHz. It is shown that the proposed DPD results in comparable performance as today's baseband models.