Bandwidth Signal Processing Research Articles

Modeling aperiodic sampling to increase the signal processing bandwidth of the sampling analog optical path

The paper discusses methods of aperiodic optical pulsed signal sampling in photonic analog-digital systems. We describe numerical modeling of aperiodic sampling and a method for reconstructing a spectrally sparse signal from aperiodicly selected samples. The described method is based on minimizing the l1 norm of the spectral representation of the reconstructed signal. Numerical simulations show that using aperiodic sampling, it is possible to reconstruct a spectrally sparse signal in the 5 GHz band using a sampling rate of 500 MS/s. The work also shows that using window functions it is possible to improve the quality of signal reconstruction from pseudo-random samples.

Novel Multilayer Extreme Learning Machine as a Massive MIMO Receiver for Millimeter Wave Communications

Wireless communication systems working in millimeter-wave (mmWave) frequency bands offer higher bandwidths than traditional radio frequency schemes. This technology allows multibeam steering and data multiplexing with the help of massive multiple-input multiple-output (MIMO) systems. However, supporting large bandwidths at mmWave frequencies is challenging due to the use of large antenna arrays with beamforming, sampling signals with large bandwidths, and baseband signal processing operations at gigabit data rates. Due to the wider bandwidth and higher signal processing requirements of mmWave systems, low-complexity receiver algorithms become important. Previously reported investigations assumed the use of hybrid beamforming structures that reduce power consumption and signal processing tasks. Therefore, the use of artificial neural networks (ANNs) becomes relevant for the processing of mmWave signals as reported in earlier works. In this article, to carry out MIMO combining processing for mmWave communications, we propose a fully complex multilayer extreme learning machine (M-ELM) neural network. We investigate the tuning of the number of neurons in each hidden layer for the proposed method to maximize the system performance and decrease the complexity of the receiver. We compare the results of the introduced M-ELM algorithm with a fully complex extreme learning machine (ELM), fully real ELM, and M-ELM defined in the real plane in terms of spectral efficiency, bit error rate, computational complexity, and processing time. Furthermore, we compare the novel M-ELM strategy with traditional linear MIMO receivers, such as Maximum Ratio and Minimum Mean Square Error, as well as to a multilayer perceptron (MLP) neural network trained offline. The numerical results show that with a good balance between the overall performance and computational cost of the ANN, the fully complex M-ELM MIMO receiver outperforms the other evaluated schemes.

Single-photon microwave photonics

With the rapid development of microwave photonics technology, high-speed processing and ultra-weak signal detection capability have become the main bottlenecks in many applications. Thanks to the ultra-weak signal detection capability and the extremely low timing jitter properties of single-photon detectors, the combination of single-photon detection and classical microwave photonics technology may provide a solution to break the above bottlenecks. In this paper, we first report a novel concept of single-photon microwave photonics (SP-MWP), a SP-MWP signal processing system with phase shifting and frequency filtering functionalities is demonstrated based on a superconducting nanowire single photon detector (SNSPD) and a successive time-correlated single photon counting (TCSPC) module. Experimental results show that an ultrahigh optical sensitivity down to −100 dBm has been achieved, and the signal processing bandwidth is only limited by the timing jitter of single-photon detectors. In the meantime, the proposed system demonstrates an ultrahigh anti-interference capability, only the signal which is phase locked by the trigger signal in TCSPC can be extracted from the detected signals combining with noise and strong interference. The proposed SP-MWP concept paves a way to a novel interdisciplinary field of microwave photonics and quantum mechanism, named by quantum microwave photonics.

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.

Fast speed switching response and high modulation signal processing bandwidth through LiNbO3 electro-optic modulators

Abstract This work outlined the fast speed response and high modulation bandwidth through LiNbO3 electro-optic modulators. The refractive index is analyzed to estimate the switching voltage and modulation bandwidth for these modulators. The modulation voltage and data transmission data rates are analyzed and discussed clearly through LiNbO3 electro-optic modulators. The modulator’s performance efficiency is upgraded with the optimum modulator length of 10 mm and its thickness of 2 mm. The proposed modulators are compared with GaAs electrooptic modulators under various electro-optic modulators dimensions at 1300 nm near-infrared region and room temperature.

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.

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.

Power Efficient Signal Processing for mmWave 5G Systems

mmWave frequencies, being considered for 5G systems, have the potential to provide Gb/s data rates utilizing large bandwidth (GHz) of available spectrum. However, the use of mmWave frequencies comes at the cost of increased power consumption due to the use of large antenna arrays with beamforming, sampling signals with GHz of bandwidth and baseband signal processing operations at Gb/s data rates. In this article, we explore the power consumption issue for mmWave 5G systems and propose power efficient signal processing architectures and algorithms in order to help mitigate power consumption at both the transmitter and the receiver. Two power efficient signal processing architectures are proposed that efficiently channelize the large bandwidth for low power. Signal processing algorithms are finally presented that investigate low power operation in the system by providing dynamic beamwidth support, peak-to-average power ratio reduction, bandwidth adaptation for control and data transmissions and low power channel decoding.

Sonographic Evaluation of Mobile Echogenicities Within the Epididymis

Current ultrasound systems have significantly improved spatial and temporal resolution secondary to increased transducer frequencies, increased bandwidth, and complex signal processing such as harmonics and compound scanning. The case presented describes the differential diagnoses of small, linear, mobile echogenic foci visualized by sonography in the left epididymal tail. Differentiation of moving parasites associated with filariasis versus mobile sperm may become more difficult as the resolution of ultrasound equipment continues to improve.

MULTI BAND, MULTI MODE DIGITAL RF RECEIVER FRONT-END MODULE FOR M-WIMAX

A digital RF receiver front-end employing a DT filter is proposed for application to m-WiMAX & The SAW-less receiver architecture, where the large out-of-band interferer can be rejected selectively by using a scalable frequency response property of FIR filter. In addition to the flexibility of the DT filter, the new non-decimation finite impulse response (NDF) filter can be cascaded to a conventional FIR filter without the decimation effect. Thus, we can easily increase the order of the function-type filtering response and the signal processing bandwidth and the designed receiver front-end is implemented using an IBM 130- nm RF CMOS process. The fabricated chip satisfies the m-WiMAX specification of an 8.75 MHz channel bandwidth and the total system power consumption is 26.63 mA from a 1.5-V supply voltage. The chip shows unwanted blocker rejection over 80 dB, with good linearity of +3.94 dB IIP3.

A Wideband Digital RF Receiver Front-End Employing a New Discrete-Time Filter for m-WiMAX

A wideband digital RF receiver front-end employing a discrete-time (DT) filter is presented for application to m-WiMAX (WiBro). By employing a sampling mixer and a DT filter, the receiver operates in the charge domain. In addition to the flexibility of the DT filter, the new non-decimation finite impulse response (NDF) filter can be cascaded to a conventional finite impulse response (FIR) filter without the decimation effect. Thus, we can easily increase the order of the <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">sincn</i> function-type filtering response and the signal processing bandwidth. The FIR filter is also modified to reduce the noise and the number of required clock signal. Because of the new filter configuration, clock signals can be shared by the FIR filter and NDF filter and the clock generator circuit can be simplified. The designed receiver front-end is implemented using an IBM 0.13-μm RF CMOS process. The fabricated chip satisfies the m-WiMAX specification of an 8.75 MHz channel bandwidth and the total system current dissipation is 26.63 mA from a 1.5-V supply voltage.

Optical decoherence and energy level structure of 0.1%Tm3+:LiNbO3

We report the energy level structure of the ${}^{3}$H${}_{6}$ and ${}^{3}$H${}_{4}$ multiplets for Tm${}^{3+}$ doped congruent LiNbO${}_{3}$, as well as the decoherence properties and their temperature dependencies for the ${}^{3}$H${}_{6}(1){\ensuremath{\leftrightarrow}}^{3}$H${}_{4}(1a)$ transition at 794 nm. It is shown that this material provides very significant improvements in bandwidth, time-bandwidth product, and sensitivity for spatial-spectral holographic signal processing devices and quantum memories based on spectral hole burning. The available signal processing bandwidth for 0.1$%$Tm${}^{3+}$:LiNbO${}_{3}$ is 300 GHz versus 20 GHz for Tm${}^{3+}$YAG. The peak absorption coefficient for 0.1$%$Tm${}^{3+}$:LiNbO${}_{3}$ is 15 cm${}^{\ensuremath{-}1}$ at 794.5 nm compared with 1.7 cm${}^{\ensuremath{-}1}$ for 0.1$%$Tm:YAG at 793 nm, and the total absorption strength is eighty times stronger. The oscillator strength for Tm${}^{3+}$:LiNbO${}_{3}$ is about twenty-five times larger than that for Tm${}^{3+}$:YAG, making the material five times more sensitive for processing high-bandwidth analog signals. The homogeneous linewidth, which determines processing time or spectrum analyzer resolution, is 30 kHz at 1.6 K and 350 kHz at 6 K, as measured by photon echoes. Those values establish potential time-bandwidth products of 10${}^{7}$ and 7 $\ifmmode\times\else\texttimes\fi{}$10${}^{5}$, respectively. The temperature dependence of the homogeneous linewidth was explained by observation of a 7.8 cm${}^{\ensuremath{-}1}$ crystal field level in the ground multiplet and direct phonon coupling. The excited state ${}^{3}$H${}_{4}$ lifetime ${T}_{1}$ is 152 $\ensuremath{\mu}$s and the bottleneck lifetime of the lowest ${}^{3}$F${}_{4}$ level is 7 ms from photon echo measurements. These factors combine to provide a surprisingly large increase in key parameters that determine material performance for spatial-spectral holography, quantum information, and other spectral hole burning applications.

Terahertz Information and Signal Processing by RF-Photonics

This paper discusses THz bandwidth information and signal processing based on RF-photonic technologies. In particular, we will emphasize integrated circuit approaches to RF-photonics where highly stable THz bandwidth information and signal processing can take place. We will demonstrate THz signal generation by optical arbitrary waveform generation (OAWG), and will describe its inverse process, optical arbitrary waveform measurement (OAWM). Further, we will discuss an RF-photonic lattice filter useful for optical equalization and other THz signal processing replacing traditional electronic digital signal processing which cannot currently scale to THz. The paper will also cover future prospects for the THz information and signal processing by integrated RF-photonic methods.

Rare-earth-doped materials for applications in quantum information storage and signal processing

Realization of practical quantum memory and optical signal processing systems critically depends on suitable materials that offer specific combinations of properties. Solid-state materials such as rare-earth ions doped into dielectric crystals are one of the most promising candidates for several quantum information storage protocols, including quantum storage of single photons. This article provides an overview of rare-earth-doped material properties and summarizes some of the most promising materials studied in our laboratory and by other groups for applications in quantum information storage and for ultra-wide bandwidth signal processing. Understanding and controlling spectral diffusion in these materials, which ultimately limits the achievable performance of any quantum memory system, is also briefly reviewed. Applications in quantum information impose stringent requirements on laser phase and frequency stability, and employing a narrow spectral hole in the inhomogeneous absorption profile in these materials as a frequency reference can dramatically improve laser stability. We review our work on laser frequency and phase stabilization and report our recent results on using a narrow spectral hole as a passive dynamic spectral filter for laser phase noise suppression, which can dramatically narrow the laser linewidth with or without the requirement of active feedback.

A Middle Ear Microphone Design Based on the Physiology of the Human Ear

A capacitive displacement sensor matching the physiological characteristic of the human middle ear is presented. The transducer measures tiny deflections of the umbo, a part of the middle ear bone chain, to evaluate sound events stimulating the eardrum. Compared to other approaches, our sensor delivers a lower susceptibility to gravity due to a higher resonant frequency. Furthermore, measurement results in the lower frequency range are competitive to other research groups. Within the frequency range of 200Hz to 10kHz, a resolution of 4 pm is achieved using a signal processing bandwidth of 100Hz. This resolution is equivalent to the lower threshold of speech or to a loudness level of 40 phon.

Measurement and characterization of army impulsive noise sources.

Peak pressure levels in army noise environments range from 140- to 195-dB near soldiers firing energetic weapons and are all dangerous to unprotected ears. Blast reverberation in confined spaces and steady noise in armored vehicles is also hazardous, so complete assessment requires the widest possible measurement range. To accurately measure pressures in the free-field or under hearing protectors, microphone considerations include type, location, orientation, mounting, shape, and shielding from flash or mechanical shock. Blast-waves rise instantaneously and return to free-field ambient within 0.3–15 ms, while in enclosures this can increase to 100 ms, requiring wide bandwidth signal processing. In addition to hazard, acoustic detection and annoyance at greater distances from weapons involve propagation effects in the atmosphere and at the ground which alter the wave-shape.

Single Crystal CVD Diamond Detectors: Position and Temporal Response Measurements using a Synchrotron Microbeam Probe

AbstractUltrapure, homoeptaxially grown CVD single crystal diamond is a material with great potential for the fabrication of ionizing radiation detectors for high energy, heavy ion physics, and realtime dosimetry for radiotherapy. Only diamond has suitable transmission properties and can offer the required radiation hardness for synchrotron X-ray beam monitoring applications. We report on experiments made using a synchrotron X-ray microbeam probe to investigate the performance of single crystal diamonds operated as position sensitive, solid state ‘ionization chambers’. We show that for a wide range of electric fields &gt;0.3Vµm−1, suitably prepared devices give excellent spatial response uniformity and time stability. With an applied field of 2Vµm−1 complete charge collection times are ∼1nsec for a diamond plate thickness of 100µm. Position sensitivity was obtained for an X-ray beam incident on the isolation gap between adjacent electrodes of a quadrant device: here, a crossover response region that results from charge carrier diffusion extends over ∼20µm. Using GHz bandwidth signal processing electronics, the signal charge collection process was measured with spatial and temporal resolutions of 1µm and &lt;50ps.

Distinguishing between optical coherent states with imperfect detection

Several proposed techniques for distinguishing between optical coherent states are analyzed under a physically realistic model of photodetection. Quantum error probabilities are derived for the Kennedy receiver, the Dolinar receiver, and the unitary rotation scheme proposed by Sasaki and Hirota for subunity detector efficiency. Monte Carlo simulations are performed to assess the effects of detector dark counts, dead time, signal processing bandwidth, and phase noise in the communication channel. The feedback strategy employed by the Dolinar receiver is found to achieve the Helstrom bound for subunity detection efficiency and to provide robustness to these other detector imperfections making it more attractive for laboratory implementation than previously believed.

Synchroscalar

We present Synchroscalar, a tile-based architecture forembedded processing that is designed to provide the flexibilityof DSPs while approaching the power efficiency ofASICs. We achieve this goal by providing high parallelismand voltage scaling while minimizing control and communicationcosts. Specifically, Synchroscalar uses columnsof processor tiles organized into statically-assignedfrequency-voltage domains to minimize power consumption.Furthermore, while columns use SIMD control to minimizeoverhead, data-dependent computations can besupported by extremely flexible statically-scheduled communicationbetween columns.We provide a detailed evaluation of Synchroscalar includingSPICE simulation, wire and device models, synthesisof key components, cycle-level simulation, andcompiler- and hand-optimized signal processing applications.We find that the goal of meeting, not exceeding, performancetargets with data-parallel applications leads todesigns that depart significantly from our intuitions derivedfrom general-purpose microprocessor design. Inparticular, synchronous design and substantial global interconnectare desirable in the low-frequency, low-powerdomain. This global interconnect supports parallelizationand reduces processor idle time, which are critical to energyefficient implementations of high bandwidth signalprocessing. Overall, Synchroscalar provides programmabilitywhile achieving power efficiencies within 8-30X ofknown ASIC implementations, which is 10-60X better thanconventional DSPs. In addition, frequency-voltage scalingin Synchroscalar provides between 3-32% power savingsin our application suite.