High Data Rate Signal Research Articles

A Self-Calibration SCPA With Storage Capacitor Array Supporting 64-/256-/1024-QAM

This article presents a digital polar Doherty switched-capacitor power amplifier (SCPA) using on-chip self-calibration technique with storage capacitor array (SCA) to compensate the amplitude modulation (AM)–phase modulation (PM) distortion automatically for high data-rate signals. Such a self-calibration technique detects the AM–PM distortion at output and generates the related phase compensation in PM signals. The SCA is proposed to store control voltages of phase shifter for different amplitude code and decrease the settle time for high data-rate, which achieves fast locking of the calibration loop. Based on the proposed self-calibration with SCA, a polar Doherty SCPA is designed and fabricated in conventional 40-nm CMOS technology. This chip achieves 28.9-dBm peak output power ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\textit{P}_\textup{sat}$</tex-math> </inline-formula> ) and 43.9% peak drain efficiency (DE) at 1.8 GHz. It supports 100-MHz 64-QAM/10-MHz 1024-QAM signal with 22.6-/21.3-dBm average output power and 33.9%/32.1% average DE without digital pre-distortion (DPD).

Performance of DSSS Signal Transmission with SCM over Low-Frequency MMF Passbands

The transmission of a high data rate signal over low-frequency passbands of multimode fibers is studied in this paper. The subcarrier multiplexing (SCM) technique is applied to mitigate the frequency-selective nature of the passbands, at which many nulls can degrade the signal transmission. The subcarrier frequencies must be chosen appropriately, especially for some low-frequency passbands; otherwise, poorly received subcarrier signals will be obtained, affecting the entire transmission. Rather than transmitting many subcarrier signals over these passbands, the direct sequence spread spectrum (DSSS) technique can be adopted. In this work, a high data rate signal is transmitted over 1 km of multimode fiber using the 3-dB modal band and six other low-frequency passbands. The signal is separated into four sub-signals transmitted over four different channels: the 3-dB modal band, two low-frequency passbands, and one passband (containing four low-frequency passbands). In the last passband, the sub-signal is transmitted using the DSSS, while the other sub-signals are transmitted through amplitude shift keying (ASK) modulation. The performance of the system is determined using the bit error rate (BER). The findings reveal that by applying the DSSS to some low-frequency passbands, robustness is obtained in the subcarrier frequency for use in the DSSS passband. A BER lower than 10-9 with a total data rate of 600 Mbps is achieved. This data rate is three times higher than the data rate obtained by the 3-dB modal band. This performance is achieved without applying any error-correction code.

Modeling and design of enhanced all optical signal regeneration technique

Optical Signal regeneration in all-optical domain has played a vital in role for long haul optical communication systems. On contrary, the electronic regeneration systems have limitations in terms of real-time infeasibility for high data rate transmission with quality performance. The existing all-optical signal regeneration techniques remain in challenges for its complex design, testing and modeling prospective. The proposed all-optical signal regeneration technique is the new signal regeneration technique that is modeled and designed efficiently in order to regenerate high data rate signal that is degraded during transmission. The proposed all-optical signal regeneration technique is developed using single- pump Phase Sensitive Amplification, designed Optical Frequency Locked Model and noise mitigation model. The PSA performance is examined using various aspects i.e. signal power, noise figures, and phase error detection and correction. The proposed system will add a new dimension for signal regeneration schemes to develop more efficient regeneration systems with better performance analysis approach.

An Ultrafast all optical Encryption Decryption Scheme based on XOR logic for secure transmission in Optical Networks

An ultrafast encryption decryption scheme is proposed at 160 Gb/s for secure transmission over optical networks. Proposed Encryption decryption circuits have been designed using semiconductor optical amplifier based XOR logic with delay interferometer. Delay interferometer is used to mitigate effect of slow carrier recovery in semiconductor optical amplifier which act as a bottleneck specially for high data rate signal transmission. The system performance is evaluated and investigated in terms of extinction ratio and quality factor. The results demonstrate that proposed scheme is feasible and offers high level of security at ultrafast data rate.

Passive WiFi Radar for Human Sensing Using a Stand-Alone Access Point

Human sensing using WiFi signal transmissions is attracting significant attention for future applications in e-healthcare, security, and the Internet of Things (IoT). The majority of WiFi sensing systems are based around processing of channel state information (CSI) data which originates from commodity WiFi access points (APs) that have been primed to transmit high data-rate signals with high repetition frequencies. However, in reality, WiFi APs do not transmit in such a continuous uninterrupted fashion, especially when there are no users on the communication network. To this end, we have developed a passive WiFi radar system for human sensing which exploits WiFi signals irrespective of whether the WiFi AP is transmitting continuous high data-rate Orthogonal Frequency-Division Multiplexing (OFDM) signals, or periodic WiFi beacon signals while in an idle status (no users on the WiFi network). In a data transmission phase, we employ the standard cross ambiguity function (CAF) processing to extract Doppler information relating to the target, while a modified version is used for lower data-rate signals. In addition, we investigate the utility of an external device that has been developed to stimulate idle WiFi APs to transmit usable signals without requiring any type of user authentication on the WiFi network. In this article, we present experimental data which verifies our proposed methods for using any type of signal transmission from a standalone WiFi device, and demonstrate the capability for human activity sensing.

Millimeter wave difference-frequency mixing by mobile carriers in gated monolayer graphene with broken centrosymmetry

Motivated by the device application potential of microwave difference-frequency generation (DFG) in graphene, we develop a theory of this second-order non-linear phenomenon in individual graphene layers lacking center-of-inversion symmetry due to their interaction with a substrate such as SiC or h-BN. Using the Boltzmann equation techniques, we calculate the microwave DFG conductivity of the graphene layer where the number of free carriers is controlled by an external gate voltage. The results obtained shed light on how the doping level of graphene, as well as a substrate-induced bandgap in the graphene’s electronic spectrum, affects the efficiency of the graphene-based frequency downconversion from the millimeter wave band to the microwave one. In particular, it is shown that there are some possibilities to maximize the output power of the microwave DFG by selecting graphene/substrate pairs with smaller substrate-induced bandgap values and by tuning, in the proper way, the Fermi energy of charge carriers via electrostatic gating. The gate controllable DFG enhancement can be achieved in gapped and doped graphene samples at the electron concentration level of the order of cm−2, thus paving the way to electrically tunable frequency downconvertors for millimeter wave applications in high data rate communication systems and signal processing.

Compensation of DAC clock leakage in short-reach DMT system in the presence of sampling frequency offset

Digital-to-analog converter (DAC) with a high sampling-rate has been extensively applied in optical discrete multi-tone (DMT) system for high data-rate signal generation. However, there exist various imperfections during the manufacturing of DAC when its sampling rate is tens of giga-samples per second and beyond. Clock tone leakage (CTL) is a kind of interference in high-speed DACs. One or more data subcarriers of the generated DMT signal may suffer from additional clock tones, which may degrade the overall bit error rate (BER) performance of the optical DMT system. In the literature, several schemes have been proposed to compensate CTL for short-reach applications. Nevertheless, these compensation schemes may not work effectively in the asynchronous DMT system in the presence of sampling clock frequency offset (SFO) between DAC and analog-to-digital converter. In this paper, an effective CTL compensation (CLC) with the digital interpolation scheme is proposed and experimentally investigated in a short-reach 100G DMT transmission system with direct detection. The results indicate that the proposed CLC with a fourth-order interpolation (FOI) scheme can effectively compensate the CTL in the presence of an SFO up to ±1000 parts per million (ppm). What is more, we discuss the impact of SFO estimation error on the BER performance of the 64-ary quadrature amplitude modulation-encoded DMT system. It shows that the BER performance penalty can be ignored by shortening the DMT frame even though the estimation error is up to 2 ppm.

100-Gb/s DMT Transmission for Short-Reach Optical Interconnect With DAC Clock Leakage Compensation

Digital-to-analog converters (DAC) with a high sample rate and large bandwidth are preferred to achieve high data-rate signal generation in an optical discrete multi-tone (DMT) system. Clock leakage is one of the imperfections in high-speed DACs. One or more data subcarriers of the generated DMT signal may be interfered by the additional clock tone, which may cause error floor in bit error rate (BER) performance. In this work, the pre-equalized 16/32QAM-DMT signals with the net data rate up to 121 Gbit/s are generated by an 80 GSa/s DAC with a clock leakage at 20 GHz. Two simple DAC clock leakage compensation (CLC) methods are employed and investigated in the DMT receiver. The results exhibit the two CLC methods have a similar performance. After 2 km of standard single-mode fiber (SSMF) transmission, by using the two CLC methods, the BER performance can be improved by up to about an order of magnitude and below 3.8e-3 for 16QAM-DMT. The receiver sensitivity in terms of the received optical power can be improved by 2-dB in 32QAM case at the BER of 2e-2. Furthermore, the BER performance with two CLC methods has good stability over the measurement period.

The Evolution of Integrated CMOS Power Amplifiers for Next Generation Mobile Wireless Transceivers

Wireless communication standard continues to evolve in order to fulfill the demand for high data rate operation. This leads to the exertion on the design of radio frequency power amplifier (RFPA) which consumes high DC power in order to support linear transmission of high data rate signal. Hence, operating the PA with low DC power consumption without trading-off the linearity is vital in order to achieve the goal of achieving fully integrated system-on-chip (SoC) solution for 4G and 5G transceivers. In this paper, the evolution of CMOS PA toward achieving a fully integrated transceiver solution is discussed through the review of multifarious CMOS PA design. This is categorized into the review of efficiency enhancement designs followed by linearity enhancement designs of the CMOS PA.

Examination of Potential Terrestrial System Effects From Raman Pumps Below Cable Cutoff in G.654.E Fibers

ITU G.654.E was recently approved as a new optical fiber standard for terrestrial systems. While G.654-compliant fibers have been used extensively in undersea submarine networks for some time, the G.654.E standard is optimized for terrestrial systems and, in particular, it enables the use of large effective area fibers to extend the reach of new high data rate signals with multilevel modulation formats. The new G.654.E fiber standard increases the maximum cable cutoff wavelength specification to the lower edge of the C- band, 1530 nm. We analyze potential signal impairments that may arise from Raman amplification with pump wavelengths below cable cutoff. We study the case where Raman pump relative intensity noise (RIN) is caused only by Raman pump multipath interference and show that its effect is negligible compared to the contribution from inherent Raman pump RIN that is constant along a fiber propagation length. We find negligible effects are expected even under worst-case condition.

Interference management issues for the future 5G network: a review

The future wireless Fifth Generation (5G) communication network required a higher bandwidth in order to achieve greater data rate. It will be largely characterized by small cell deployments, typically in the range of 200 meters of radius/cell, at most. The implementation of small size networks delivers various advantages such as high data rate and low signal delay. However, it also suffers from various issues such as inter-cell, intra-cell, and inter-user interferences. This paper discusses the issues related to interference management for 5G network from the perspective of Heterogeneous Network and Device-to-Device communication, by using enabling techniques, such as Inter-cell Interference Coordination, Coordinated Multipoint, and Coordinated Scheduling. Furthermore, several pertinent issues have been critically reviewed focusing on their methodologies, advantages and limitations along with the future work. Future directions proposed by the 3rd Generation Partnership Project for interference mitigation has also been outlined. This review will act as a guide for the researchers to comprehend various existing and emerging enabling interference mitigation techniques for further exploration and smooth implementation of 5G wireless network.

Performance Analysis of Single Side Band Orthogonal Frequency Division Multiplexing in Radio over Fiber System with Direct and External Modulation Schemes

Abstract Radio over fiber is a technology in which the light signals at the central station are modulated by a radio frequency signal, and by using the optical fiber it is transmitted to base stations. The data stream being sent is separated into subcarrier frequencies by the technique of orthogonal frequency division multiplexing. The orthogonality between the sub-carriers is provided by FFT modulation, which avoids the demodulators from accepting other frequencies. It is possible to transmit high-data rate signals over short and long distance by implementing orthogonal frequency division multiplexing with radio over fiber system along with the optical fiber. This enhances the system with more coverage area, and without increasing the cost of the system it provides the flexibility. The proposed work is to investigate the performance analysis of single side band orthogonal frequency division multiplexing in radio over fiber system with external and direct modulations using spectral analysers and constellation visualizers. The Mach-Zender modulator is proposed for external modulation, the vertical cavity surface emitting laser is used in direct modulation. The simulations were carried out by using Optisystem Software version 15.0 with global parameters for both intensity modulation schemes.

Laser Phase Noise Tolerance in Direct Detection Optical OFDM Transmission Using Laser Linewidth Emulator

Laser phase noise tolerance in direct detection optical orthogonal frequency division multiplexing (OFDM) transmission system is experimentally demonstrated using laser linewidth emulator. With this linewidth emulator, the linewidth of the laser can be broadened independently without inducing other laser's noise characteristics such as relative intensity noise and chirping. The results show the effect of phase-to-intensity noise conversion due to the laser's phase noise and chromatic dispersion. This induces noise pedestals not only onto the optical carrier, but also to each of the subcarriers, and thus produces intersubcarriers interference. Measurements show 6 dB Q-degradation is suffered by the system when 10 MHz linewidth is used as compared to using narrowest emulator linewidth of 256 kHz. Transmission with the linewidth emulator set to 20 MHz is also shown where it can still be tolerated by 400 km of fiber at the Q of 9.606 dB with respect to $1.6\,\times \,10^{{\rm - 3}}$ bit error rate. Simulation of 16 quadratic-amplitude modulation (QAM) (∼128 Gb/s) and 4 QAM (∼100 Gb/s) using VPItransmissionMaker are also presented to demonstrate the effect of carrier's phase-to-intensity noise conversion when a high data rate and wide OFDM signal bandwidth are used with the linewidth emulator as the system's laser source. The results show that a phase rotation term is insignificant for lower M -size QAM with fiber length less than 500 km. This presents the high effectiveness and reliability of the laser linewidth emulator to discretely determine an independent phase noise tolerance from the other laser's noise characteristics in the optical OFDM transmission system.

Photonic-Assisted mm-Wave and THz Wireless Transmission towards 100 Gbit/s Data Rate

Abstract This paper presents photonic-assisted 60 GHz mm-wave and 325 GHz system approaches that enable the transmission of spectral-efficient and high data rate signals over fiber and over air. First, we focus on generic channel characteristics within the mm-wave 60 GHz band and at the terahertz (THz) band around 325 GHz. Next, for generating the high data rate baseband signals, we present a technical solution for constructing an extreme bandwidth arbitrary waveform generator (AWG). We then report the development of a novel coherent photonic mixer (CPX) module for direct optic-to-RF conversion of extreme wideband optical signals, with a&gt;5 dB higher conversion gain compared to conventional photodiodes. Finally, we experimentally demonstrate record spectral efficient wireless transmission for both bands. The achieved spectral efficiencies reach 10 bit/s/Hz for the 60 GHz band and 6 bit/s/Hz for the 325 GHz band. The maximum data rate transmitted at THz frequencies in the 325 GHz band is 59 Gbit/s using a 64-QAM-OFDM modulation format and a 10 GHz wide data signal.

UWB over fiber transmission to multiple radio access units using all-optical signal processing

An ultra-wideband over fiber architecture is proposed where multiple coherent pulsed optical signals are used for transmitting high data rate signals to five different radio access units (RAUs). The RAUs are placed in a star topology to form a broadcast distributive antenna system architecture. The architecture transmits $$5 \times 1.25$$5?1.25 Gbps data from control unit to the RAUs using a wavelength division multiplexed signal. The multiple pulsed optical carriers forming the wavelength division multiplexed signal are generated using a single continuous wave optical source. The data modulated coherent optical pulsed signals are all-optically converted to electrical Gaussian mono-cycle pulses at the RAUs. The proposed architecture is cost-efficient and gives good bit-error rate results.

Design of a compact multilayer circularly polarized phased array transmit antenna system for satellite applications

An active phased array antenna which can scan its beam direction to a wide range of scan angles is presented in this paper. The paper proposes a new technique to compact a phased array antenna and making it suitable for applying in satellite payloads. This antenna should transmit high data rate signal from satellite to ground stations; and by spatial power combining the needed Effective Isotropic Radiated Power (EIRP) for the transmission link will be provided. The main beam can be scanned to 50° from normal. Polarization of the radiated wave of this antenna is circular. The designed antenna benefits from microstrip technology and has a unique low mass multilayer structure with two different substrates. For implementing antenna’s RF circuits, Microwave Monolithic Integrated Circuits (MMICs) have been used and they are integrated expertly with microstrip radiators. Beam controller board sends necessary commands to MMICs for setting phase and amplitude of each array module. For decreasing side lobe level in high scan angles, genetic algorithm is applied and excitations of array elements are optimized. Design stages and simulation results of the array antenna are summarized in this paper and the results are compared with test results.

Listening in

Professor Yongxin Guo from the National University of Singapore talks to us about his research on biomedical antennas. In a collaboration with the University of Electronic Science and Technology of China, Professor Guo presents an optimised bandwidth biomedical antenna. The fabricated circularly polarised antenna was constructed on a single-layer planar substrate With the advancement of wireless technologies, researchers have been able successfully to implant antennas inside the human body, which has allowed the wireless monitoring of vital signs. Transdermal or percutaneous wires running out of the body from an implanted device can be cumbersome and lead to infection, making them unsuitable for long term uses and applications. The use of biomedical antennas allows low impact, long-term monitoring. Data can be transmitted wirelessly from a variety of different implantable medical devices such as pacemakers, insulin pumps and cochlear implants. Recently, various research groups have also tried to wirelessly power implanted devices using far-field antennas, which would enable devices to remain inside the body for long periods of time. Antenna research for biomedical applications focuses heavily on topics such as antenna miniaturisation. The antennas, in general, are designed to operate in a desired frequency band, say 2.4–2.5 GHz. Those produced for implantable applications have several design considerations. For long-term implants the tissue thicknesses of the patient will change over time, resulting in an overall resonance frequency shift of the antenna. If a narrowband antenna is used, the frequency will be detuned and the new frequency will have to be found by trial and error. A redesign of the external transceiver would also be required. Broadband antennas are better adapted for these situations, as minor shifts in frequency will still remain inside the usable operational bandwidth. A large bandwidth corresponds to high data rate signal. This is useful for certain applications like capsule endoscopy, where video signals are transmitted outside of the body, broadband antennas can provide high data rates for their large operational bandwidth. Through the analysis of antennas in human body models, known as voxels, their performances can be stabilised and safety issues caused by the radiation can be accounted for. Broadband antennas, like the one proposed in this paper, are highly useful for reliable telemetry in implantable medical devices. A broad bandwidth enables information to be transmitted quickly and with higher reliability. Transmitting over multiple channels using a broadband antenna provides greater flexibility for a telemetry signal. In this paper the team used a cross-shaped structure to generate two orthogonal modes for circularly polarised radiation. By embedding the cross-shaped slot in the ground plane and optimising its dimensions, the impedance and axial ratio bandwidth have been enhanced to cover the 2.4–2.48 GHz ISM band. There are several slot geometries that can be embedded in the ground plane for axial ratio bandwidth enhancement, but cross-shaped slots achieve good circularly polarised radiation with simple structure. For biomedical antennas, one of the design practices is to keep the antenna design simple. With the advancements in material sciences, novel materials are being developed that mimic human tissues. Advances in semiconductor technology and electronic components have led to the miniaturisation of the biomedical devices such as microchip implants. The next decade might witness further miniaturisation of electromagnetic interfaces suitable for integration with the micro-scaled biomedical devices. With such devices, the hope is that researchers will be able to address the diseases that have been untreatable, and will enhance their capability to help with current health issues with much higher precision. A Gustav voxel model was used to access the effects of the human body on the antennas performance

Possibilities for Advanced Encoding Techniques at Signal Transmission in the Optical Transmission Medium

This paper presents a possible simulation of negative effects in the optical transmission medium and an analysis for the utilization of different signal processing techniques at the optical signal transmission. An attention is focused on the high data rate signal transmission in the optical fiber influenced by linear and nonlinear environmental effects presented by the prepared simulation model. The analysis includes possible utilization of OOK, BPSK, DBPSK, BFSK, QPSK, DQPSK, 8PSK, and 16QAM modulation techniques together with RS, BCH, and LDPC encoding techniques for the signal transmission in the optical fiber. Moreover, the prepared simulation model is compared with real optical transmission systems. In the final part, a comparison of the selected modulation techniques with different encoding techniques and their implementation in real transmission systems is shown.

Modified algorithm of 16 kb/s ADPCM

This paper presents a new modified algorithm of 16 kb/s ADPCM. The modification is related to the adaptive predictor rather than the adaptive quantiser. The purpose of this modification is to reduce the nonlinear distortion introduced by ADPCM when a high data rate signal passes through it. The performances of standard and modified algorithms are studied using a QAM signal at a data rate of 9.6 kb/s. The simulation results show that the performance of modified ADPCM is better than the standard ADPCM.

New high-accuracy spacecraft VLBI tracking using high data-rate signal: A demonstration with Chang’E-3

As the scientific data volume in deep-space exploration rapidly grows, spacecraft heavily relies on high data-rate signals that span several megahertz to transmit data back to Earth. Employing high data-rate signals for high-accuracy radiometric interferometry can simultaneously deal with data transmission and spacecraft navigation. We demonstrate very long baseline interferometry (VLBI) tracking of the Chang’E-3 lander and rover to determine their relative lunar-surface position using downlink high data-rate signals. A new method based on the VLBI phase-referencing technique is proposed to obtain the differential phase delay, which is much more accurate than the differential group delay acquired by conventional VLBI approaches. The systemic errors among different signal channels have been well calibrated using the new method. The data from the Chang’E-3 mission were then processed, and meter-level accuracy positions of the rover with respect to the lander have been obtained. This demonstration shows the feasibility of high-accuracy radiometric interferometry using high data-rate signals. The method proposed in this paper can also be applied to future deep-space navigation.