High Bandwidth Signal Research Articles

Routing and assignment of wavelengths for bicube in linear array WDM optical networks

Optical networks leverage the principles of optical communication to transmit data over long distances with high bandwidth and low signal loss. They have lots of applications supporting the backbone of modern communication systems. Wavelength division multiplexing (WDM) enables the simultaneous transmission of many signals with distinct wavelengths via one optical fiber, thereby increasing the overall capacity of the network. One of the significant aspects of designing and managing WDM optical networks involves routing and wavelength assignment (RWA), especially as the demand for high-capacity, low-latency communication continues to grow in recent times. Bicube networks possess many attractive properties, one of the salient features being low diameter as compared to a hypercube. Hence, research using bicube topology is very much prevalent in the last few years. In this paper, we use the technique of congestion to study the RWA problem for bicube in a linear array optical network that uses WDM technology. We also propose algorithms to efficiently compute the minimum number of wavelengths.

Analysis and design of a GHz bandwidth adaptive bias circuit for an mmW Doherty amplifier

This paper derives theoretical results for adaptive bias in Doherty amplifiers and presents the design and measurements of an integrated adaptive bias circuit tailored for high peak-to-average high bandwidth signals. Fundamental equations for output power, impedance, and efficiency of the complete Doherty amplifier are derived. Even with ideal transistor models, the Doherty amplifier is fundamentally nonlinear due to saturation of the main amplifier and class-C nonlinearity of the auxiliary. Increasing the transconductance of the auxiliary amplifier mitigates the distortion. Adaptive bias offers the possibility to control the output current characteristic of the auxiliary amplifier. This means that adaptive bias linearises and mitigates the need for an oversized auxiliary amplifier. Both methods, transconductance scaling and adaptive bias, are analysed and compared as well as having a band limited adaptive bias signal. The design of a multiple GHz bandwidth adaptive bias circuit is presented. To verify the circuit design and the theoretical predictions, an mmW Doherty amplifier in 22 nm CMOS-FD-SOI, utilizing the presented adaptive bias circuit, is measured and compared with and without adaptive bias. Comparison is conducted both using continuous-wave and modulated high bandwidth signals. Measured results confirm the predicted improvements by the adaptive bias as derived by the theoretical analysis.

Wideband and low-spurious optical waveform generator for optically addressable quantum systems manipulation and control

Optical manipulation of quantum systems requires stable laser sources able to produce complex waveforms over a large frequency range. In the visible region, such waveforms can be generated using an acousto-optic modulator driven by an arbitrary waveform generator, but these suffer from a limited tuning range typically of a few tens of MHz. Visible-range electro-optic modulators are an alternative option offering a larger modulation bandwidth, however they have limited output power which drastically restricts the scalability of quantum applications. There is currently no architecture able to perform phase-stabilized waveforms over several GHz in the visible or near infrared region while providing sufficient optical power for quantum applications. Here we propose and develop a modulation and frequency conversion set-up able to deliver optical waveforms over a large frequency range, with a high spurious extinction ratio, scalable to the entire visible/near infrared region with high optical power. The optical waveforms are first generated at telecom wavelength and then converted to the emitter wavelength through a sum frequency generation process. By adapting the pump laser frequency, the optical waveforms can be tuned to interact with a broad range of optical quantum emitters or qubits such as alkali atoms, trapped ions, rare earth ions, or fluorescent defects in solid-state matrices. Using this architecture, we were able to detect and study a single erbium ion in a nanoparticle. We also generated high bandwidth signals at 606 nm, which would enable frequency multiplexing of on-demand read-out Pr3+:Y2SiO5 quantum memories.

Integrated segmented IQ-modulator for orthogonal sampling and multi-level high-bandwidth signal generation.

Photonic-assisted signal processing of high-bandwidth signals emerges as a solution for challenges encountered in electronic-based processing. Here we present a concept for a compact, photonic-assisted digital-to-analog converter (DAC) and optical IQ-modulator in one single integrated device based on two innovative concepts: a segmented Mach-Zehnder modulator and orthogonal sampling. For electrically driving the modulator, only a single radio frequency oscillator and no pulse source or electrical DAC are required. The presented and simulated proof-of-concept device with six segments can generate a multi-level and high-bandwidth signal from low-bandwidth electronic drivers; e.g., we show the generation of a 120 Gbps data rate, 16-quadrature amplitude modulation (16-QAM, 30 Gbaud) signal solely based on low-bandwidth (5 GHz) non-return-to-zero (NRZ) signals. Integrated on a silicon photonic platform, the device provides fixable speed and bandwidth operations, positioning it as a viable solution for diverse communication systems.

An 80–84.8 GHz PLL with auto-tracking Miller divider for FMCW applications

To generate high frequency signals for frequency modulated continuous wave (FMCW) application, components such as doubler, tripler or multiplier are usually utilized to process further signals from the low frequency voltage controlled oscillator (VCO). In this paper, a phase-locked loop (PLL) is intended to be the primary part used to generate frequency modulated continuous wave (FMCW) signals from 80 to 84.8 GHz by utilizing a fundamental frequency VCO. To divide those high frequency output signal and large output bandwidth, the auto-tracking Miller divider topology is proposed. This new topology can achieve 9 GHz locking range. In order to generate FMCW signals with a straight-line triangular chirp, the cascaded PLL is used. The integrated jitter from 1 kHz to 1 GHz is 887 fs for the cascaded PLL, while the single stage PLL used 1.264 ps. Moreover, when architecture with doubler or multiplier is used, the fundamental tone has an effect towards the next systems, while the cascaded PLL does not. It can be highlighted that this work achieves the best RMS-FMerror/BWchirp and RMS-FMerror/(BWchirp × fc × Tc) with value of 0.013% and 0.77e−12, respectively. The designed PLL for FMCW signal generator is implemented in 28 nm CMOS technology. By using a supply voltage of 1.2 V, the chip consumes power of 102 mW. Including all the chip pads, the implemented circuit occupies a silicon area of 1440 µm × 820 µm.

Analysis of Bandwidth Reduction and Resolution Improvement for Photonics-Assisted ADC

To keep pace with increasing data rates in the worldwide communication networks and the increased bandwidths requirements in measurement devices, sensors, radar, and many other applications, photonics-assisted analog-to-digital converters (PADCs) may be promising alternatives to circumvent the bandwidth bottleneck in pure electronic analog-to-digital converters (EADCs). Here we analyze optical sub-Nyquist orthogonal sampling with sinc-pulse sequences for the time-interleaving of high-bandwidth input signals into parallel low-bandwidth sub-signals (first sampling stage). These sub-signals are then detected and further processed with low-bandwidth electronic devices in parallel branches (second sampling stage). Orthogonal sampling with ideal devices is error-free. Additionally, in contrast to electronic sample and hold circuits, the first sampling stage is based on a multiplication and not a switching. Therefore, it adds no aperture jitter and the low jitter of today's oscillators can be directly transferred to the sampling of high-bandwidth signals. Compared to the direct detection, in simulations and a proof of concept experimental demonstration, we show around 8.5 dB signal-to-noise and distortion (SINAD) and 1.4 bit effective number of bits (ENOB) improvement for the detection of a 14.5 GHz signal with the proposed method in a three-branch system. With further simulations we analyze the possibilities and limits of the method and derive an equation for the resolution. In a nine-branch system with a jitter of 10 fs for the oscillator and 100 fs for the electronics, 100 GHz input signals can be processed with a resolution of 6 bit in 11 GHz electronics, for instance. The scheme is only based on a modulator and standard RF equipment. Therefore, integration into a single chip, together with the following electronic ADCs is straightforward.

LightR: A Fault-Tolerant Wavelength-Routed Optical Networks-on-Chip Topology

Optical networks-on-chip (NoCs) have emerged as a next-generation solution to overcome the limitations of electrical NoCs. In particular, wavelength-routed optical networks-on-chip (WRONoCs) are well known for their high bandwidth and ultra-low signal delay. Despite these advantages, WRONoCs are challenged by reliability concerns, because the main components in WRONoCs, i.e., microring resonators (MRRs), are susceptible to fabrication inaccuracies. When an MRR along a signal path is defective, the signal transmitted on that path will fail to reach its designated destination, which leads to transmission errors and data loss. In this work, we propose a fault-tolerant WRONoC topology, LightR, which provides two independent signal paths for each master–slave pair to tolerate defective MRRs. Moreover, we minimize the MRR usage to enhance the reliability of the WRONoCs. The experimental results show that LightR is able to provide a higher reliability with a modest MRR usage, insertion loss, and crosstalk noise. As the fault rate or the network size grows, the advantages of LightR in terms of the fault tolerance become even more significant. For example, when considering the 3% fault rate of MRRs and a 64-master × 64-slave network, LightR decreases the number of error signals by 85–90% compared to the typical state-of-the-art WRONoC topologies.

Toward Terabit Receivers for Optical and Wireless Communications

Data rates and bandwidths in global optical communication networks and their wireless access are continuously rising as a result of new applications. Besides communication, high bandwidth devices are also needed for radar, sensors and measurement systems. These increasing bandwidths might lead to problems for the electronic analog-to-digital converters (ADC) in the digital systems. A 1Tbit/s, 16-QAM modulated data signal, for instance, needs an analog processing bandwidth of 80 GHz, which is far beyond the possibilities of today's standard CMOS technology. Additionally, higher bandwidths are accompanied by a lower conversion resolution, which requires higher signal-to-noise ratios for the signals to be detectable. Here we discuss these connections and review possibilities for a solution by a photonics assisted parallelization of the incoming high bandwidth signal into several low bandwidth sub-signals in the time and frequency domain. These sub-signals can then be detected and processed with low bandwidth electronics, circumventing the CMOS bandwidth problem. This review primarily focuses on bandwidth reduction using time-frequency coherence. Since it only needs low bandwidth standard electronics and photonics, the seamless integration with the electronic ADCs into any electronic-photonic platform is straightforward. Therefore, it could become an important component of future terabit receivers in optical and wireless communication.

Integrated optical pattern generation on thin-film lithium niobate with electro-optic modulators and phase-change material cells

Reconfigurable photonic integrated circuits enable high-bandwidth signal shaping with the prospect for scalability and compact footprint. Cointegration of electro-optical tunability with nonvolatile attenuation through functional materials allows for implementing photonic devices that operate on both phase and amplitude. Based on this approach, we propose an integrated photonic design for optical pattern generation deploying a continuous-wave laser and a single electrical function generator. We employ the nonvolatile and reconfigurable phase-change material Ge2Sb2Te5 (GST) as a tunable attenuator for an integrated photonic circuit on the lithium-niobate-on-insulator (LNOI) platform. The GST can be switched between its amorphous and crystalline phases, leading to an optical contrast of ≅18dB. Combining this with integrated electro-optical modulators with a 4 GHz bandwidth in LNOI enables the generation of short optical pulses, based on the principles of inverse discrete Fourier transform.

Focus on test, measurement, quantum metrology, and analytical equipment

Focus on test, measurement, quantum metrology, and analytical equipment

Bandlimited DPD Adapted APD for 5G Communication

Spectrally efficient techniques which help in achieving a high data rate in the communication system also generate signals with a high peak-to-average power ratio (PAPR), which drives the power amplifier (PA) in early saturation. This brief proposes a bandlimited digital predistortion (DPD) adapted analog predistortion (APD) method to linearize the PA. It uses the APD technique first to remove the out-of-band distortion, and then bandlimited DPD is used to remove the in-band distortion. Unlike the conventional DPD, the bandlimited DPD does not require a very high bandwidth feedback signal which is three-to-seven times the input signal bandwidth. The bandwidth of the feedback signal in the bandlimited DPD is the same as that of the input signal. This makes the proposed method more suitable for high bandwidth signals used in advanced communication standards like 5G. The experiments performed with 64-QAM OFDM signals of bandwidth 20 MHz and 100 MHz achieve a maximum normalized mean square error (NMSE) improvement of 21 dB and 18 dB over PA, respectively. The APD circuit used in the method is designed at a central frequency of 3.5 GHz, but the experiments are carried out in an extended frequency range of 2.5 to 4.5 GHz, and the results show that the proposed method delivers significant NMSE improvement in this frequency range.

Parallel Delta-Sigma Modulator-Based Digital Predistortion of Wideband RF Power Amplifiers

In this article, we propose a new robust and highly efficient digital predistortion (DPD) concept for the linearization of wideband RF power amplifiers (PAs). The proposed approach is based on the combination of a parallelized delta-sigma modulator (DSM) and a forward model of the PA. This concept applies multi-rate techniques on a DSM that incorporates the forward PA model in its feedback loop to perform the required signal predistortion. Such a technique eliminates the need of reverse modeling and its associated problems. The multi-rate approach relaxes enormously the clock speed requirement of the DPD, which allows handling high signal bandwidths at feasible sampling rates. Moreover, enhanced performance can be achieved without the need of increasing the order of the modulator which reduces the sensitivity of the system to gain variations and phase distortions caused by the nonlinear PA characteristics. Three time-interleaved parallel DPD (P-DPD) variants are described and introduced, all of them have been shown to offer increased accuracy, and consequently better linearization performance compared to the DSM-based DPD state-of-the-art. The proposed architectures are tested and assessed using extensive real-world RF measurements at the 3.6 GHz band utilizing wideband 100 MHz 5G New Radio (NR) transmit waveforms, evidencing excellent transmit signal quality.

Improving Image Quality by Deconvolution Recovery Filter in Ultrasound Imaging.

Due to the advantages of non-radiation and real-time performance, ultrasound imaging is essential in medical imaging. Image quality is affected by the performance of the transducer in an ultrasound imaging system. For example, the bandwidth controls the pulse length, resulting in different axial resolutions. Therefore, a transducer with a large bandwidth helps to improve imaging quality. However, large bandwidths lead to increased system cost and sometimes a loss of sensitivity and lateral resolution in attenuating media. In this paper, a deconvolution recovery method combined with a frequency-domain filtering technique (DRF) is proposed to improve the imaging quality, especially for the axial resolution. In this method, the received low-bandwidth echo signals are converted into high-bandwidth signals, which is similar to the echo signals produced by a high-bandwidth transducer, and the imaging quality is improved. Simulation and experiment results show that, compared with Delay-and-sum (DAS) method, the DRF method improved axial resolution from 0.60 to 0.41 mm in simulation and from 0.62 to 0.47 mm in the tissue-mimicking phantom experiment. The contrast ratio performance is improved to some extent compared with the DAS in experimental and in-vivo images. Besides, the proposed method has the potential to further improve image quality by combining it with adaptive weightings, such as the minimum variance method.

Ultrafast silicon threshold circuitry for chaotic laser time series

Photonic computing has been intensively studied to explore the ultrahigh bandwidth of lightwaves. However, electronic support is indispensable for the post-processing and control of photonic systems owing to the difficulties encountered in all-optical processing. Herein, we demonstrate an ultrafast silicon circuitry capable of conducting thresholding operations on incoming chaotically oscillating high-bandwidth signals. Such circuits are critical elements in ultrafast random-number generators and photonic reinforcement learning that exploit chaotically oscillating time series. The circuit design, including active inductors for bandwidth expansion, and proof-of-principle fabricated device operations are demonstrated using a 180 nm silicon complementary metal–oxide–semiconductor technology node.

Design and Performance Test of Pulse X-Ray Receiver Based on LYSO-SiPM for X-Ray Communication

X-ray communication (XCOM) is a type of wireless optical communication technology that uses modulated X-ray beam as the carrier of data transmission. As a core component of an XCOM system, the X-ray signal receiver determines the upper limit of the communication rate and the quality of communication. A pulse X-ray signal receiver based on an LYSO-SiPM detector and a field-programmable gate array signal processing module is designed to solve the problems of considerable background noise and weak signal strength in the actual XCOM process. The low bit error rate (BER) at the Mbps rate is realized first for XCOM. An XCOM performance test system is used to test the receiver's signal output characteristics and communication performance. The communication rate reaches 1.21 Mbps with BER less than 1.0 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">−5</sup> . The designed pulse X-ray signal receiver can effectively identify X-ray pulse under high bandwidth and weak signal receiving power.

The Envi–City

Our main objective is to change people's perspective on an unbalanced city by viewing a new world through sustainable development goals. When we relate sustainability and a city there are important things to look upon and make a change on it. Some of the problems looked upon are, (i) Reduction in the number of birds due to electromagnetic radiation. (ii) 8-15% loss between powerplant and consumers. (iii) Air pollution. (iv) Waterlogging in city pockets and waste management. The final vision is to make a smart eco-city run fully on renewable energy. Using sustainable energy sources by fitting rooftop solar cells in every house and placing vertical turbines on the roadside reduces the dependency on fossil fuels and can generate employment in many technical fields. We shall even have automated air purifiers run by solar cells, which purify the air depending on the real-time PPM levels of dust and gasses. The smart city that we have a vision of filters out high bandwidth signal waves for mobile and telecommunication while utilizing short-range Wi-Fi devices interconnected with WAN cables which can reduce the harmful effects of high energy electromagnetic radiation on birds. This is an IoT-based city where most of the electronics and other devices are connected, running on automation for easing day-to-day activities. Implementing this project will produce a positive change in the ecosystem.

High-Bandwidth Arbitrary Signal Detection Using Low-Speed Electronics

The growing demand for bandwidth and energy efficiency requires new solutions for signal detection and processing. We demonstrate a concept for high-bandwidth signal detection with low-speed photodetectors and electronics. The method is based on the parallel optical sampling of a high-bandwidth signal with sinc-pulse sequences provided by a Mach-Zehnder modulator. For the electronic detection and processing this parallel sampling enables to divide the high-bandwidth optical signal with the bandwidth <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$B$</tex-math></inline-formula> into <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$N$</tex-math></inline-formula> electrical signals with the baseband bandwidth of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$B/(\text{2}\,N)$</tex-math></inline-formula> . In proof-of-concept experiments with <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$N=3$</tex-math></inline-formula> , we present the detection of 24 GHz optical signals by detectors with a bandwidth of only 4 GHz. For ideal components, the sampling and bandwidth down-conversion does not add an excess error to the signals and even for the non-ideal components of our proof-of-concept setup, it is below 1%. Thus, the rms error for the measurement of the 24 GHz signal was reduced by a factor of about 3.4 and the effective number of bits were increased by 1.8.

Onto a higher power handling for very high frequency direct antenna modulation

Antennas constrained to platforms that require miniaturisation, significantly smaller than the wavelength of the desired frequency, are inefficient radiators and limited to narrowband operations. To overcome these limitations, a technique called direct antenna modulation (DAM), is incorporated with electrically small antennas to enable transmission of high-bandwidth signals through narrowband antennas. DAM utilises switching circuitry to directly modulate the antenna at its corresponding peak energy moments all while being synchronised to the input signal, yet previous iterations were susceptible to low transmit powers due to limitations in the switching network's power handling capability and tremendous coupling between transistor ports that results in an ambiguous switching signal at the gate. A frequency shift keyed (FSK) DAM antenna topology is proposed, which is capable of high-power transmission through a geometrically symmetrical switching circuitry integrating pairs of complementary GaN transistors. The symmetry assists in removing coupling among transistor ports to effectively switch the transistors OFF and ON without regard to the input RF power. The authors’ theoretical analysis agrees with our simulations and far-field measurements which show the FSK DAM antenna topology is capable of transmit powers up to −1 dBm given a 42 dBm of input RF power.

A Power-Efficient Multichannel Low-Pass Filter Based on the Cascaded Multiple Accumulate Finite Impulse Response (CMFIR) Structure for Digital Image Processing

The author offers a power-efficient multichannel low-pass filter for digital image processing based on the cascade multiple accumulate finite impulse response (CMFIR) structure in this study. The CMFIR filter was created using the outputs of a linear time-invariant system (LTI), which was built using a cascaded integrator comb (CIC) and a MAC low-pass filter. The sample rate convertor based on CIC filters effectively conducts decimation or interpolation. The sample rate convertor with the CIC filter can only accommodate narrowband transmissions and so cannot be utilized for wideband signals. The MAC architecture-based sample rate convertor is a good solution for high-bandwidth signals, but it uses more resources like registers and flip-flops, which increases power consumption. Here, the CMFIR low-pass filter acts as an interpolator, introducing a sample to boost the image's resolution. CMFIR is a useful tool for addressing the issue of aliasing during sampling. In addition, the genetic algorithm was used to increase the filter's resource utilization and power consumption efficiency.

Vector acoustic properties of explosive underwater sound

The relation between acoustic pressure and velocity associated with propagating sound from explosive sources is studied. Data originate from the 2017 Sediment Characterization Experiment where the sound source is 38 g SUS, measurement ranges are order 10 km in waters 75 m; and recent experimental studies on the effects of explosive underwater sound on fish off San Diego where the source is 4.7 kg net explosive weight, ranges are order 100 m in waters 20 m. Horizontal components of velocity are resolved into a single radial component and with the vertical component the intensity vector is derived and associated energy streamlines from simulations are presented. It is also shown how radial component of acoustic velocity is phase- locked with pressure, and nearly corresponds to it upon multiplication by the characteristic impedance; including vertical velocity for total velocity magnitude the correspondence with pressure magnitude is within calibration uncertainty. This self-evident finding concerning high-bandwidth signals is worth noting to inform the discussion on the importance of acoustic velocity to fishes. An exception for short ranges is a low-amplitude, narrow band, Scholte wave arrival that decays precipitously away from the water/sediment interface. [Research support by ONR and by the Navy LMR program.]