Design, modeling, and hardware correlation of a 3.2Gb/s/pair memory channel

With the rapid advance of silicon process technology, it is now possible to design input/output (I/O) circuits that operate at multigigabit data rates. As a result, accurate modeling and analysis of high-speed interconnect systems is essential to optimize the performance of the overall system. This paper describes the interconnect design, modeling, simulation, and characterization methodologies that are essential to achieve multigigabit data rates. It focuses on the physical layer verification and hardware correlation of functional systems and silicon to ensure robust system operation over 3.2Gb/s data rate using conventional low-cost packaging and printed circuit board (PCB) technologies. In order to capture conductor and dielectric losses, as well as other high-frequency effects of three-dimensional structures, accurate measurement-based simulation techniques that directly incorporate frequency-domain parameters from measurement or electromagnetic solver parameters into circuit simulation tools using fast Fourier transform (FFT) and bandlimiting windowing techniques are developed. Finally, simulation waveforms are correlated with prototypes at both component and system levels in both time and frequency domains.     

Efficient zero-phase constrained frequency-domain block LMSadaptive algorithm

An efficient zero-phase constrained frequency-domain block LMS adaptive algorithm, that has reduced computational complexity and fast convergence speed for highly correlated input signals is proposed. The algorithm is applied to narrowband interference rejection in direct-sequence spread spectrum systems and a simulation results is presented     

Multifrequency Small-Signal Model for Buck and Multiphase Buck Converters

To investigate the high-frequency behaviors of buck and multiphase buck converters, this paper develops a modeling method based on the harmonic-balance approach. Because the nonlinear pulse-width modulator generates sideband components, the sideband effect occurs in a closed-loop converter. Taking this effect into account, the multifrequency small-signal model is proposed, which is applicable beyond half of the switching frequency. In a voltage-mode-controlled buck converter, the introduced model predicts the measured phase delay of the loop gain, while the conventional average model fails to explain this phenomenon. Furthermore, this model is extended to the case of the multiphase buck converter. The influence from the interleaving technique is discussed and the frequency-domain characteristics are clearly explained. Simulation and experimental results are provided to verify the achievements of the proposed model.     

A series resonant AC-to-DC rectifier with high-frequency isolation

In this paper, a new series resonant AC-to-DC rectifier with high-frequency isolation is introduced. The proposed approach employs a PWM controlled AC controller, a series resonant tank and a high-frequency isolation transformer. With this approach, the single phase input AC is directly processed via the AC-to-AC converter eliminating the AC-to-DC rectification stage present in the conventional system. The output of the HF transformer is rectified and processed via a filtering stage to obtain a DC output. With the addition of an input filter, the input current is near sinusoidal at unity power factor. Simulation and experiment results are presented to verify the basic concept     

Differential modulation techniques for a 34 MBit/s radio channel using orthogonal frequency division multiplexing

The orthogonal frequency division multiplexing (OFDM) technique has been proposed for terrestrial digital transmission systems due to its high spectral efficiency, its robustness in different multipath propagation environments and the ability of avoiding intersymbol interference (ISI). Our studies consider a radio channel bandwidth of 8 MHz and a data rate of 34 Mbit/s.In the case of the OFDM transmission system a coherent 64-QAM requires a channel estimation process and a channel equalization in frequency-selective interference situations [4]. The equalization process can be realized by a multiplier bank at the FFT output in the receiver, a so-called frequency-domain equalizer. Alternatively, a multilevel differential modulation technique, the so-called differential amplitude and phase shift keying (64-DAPSK) considering the phase and simultaneously the amplitude for differential modulation, is proposed and presented in this paper. Differential modulation/demodulation techniques do not require any explicit knowledge about the radio channel properties in the differential channel equalization. It is therefore not necessary to implement a frequency-domain equalizer in an OFDM/64-DAPSK receiver, which reduces the computation complexity. The performance of both modulation techniques has been analysed in the uncoded and coded case referring to Gaussian and frequency-selective Rayleigh fading channels. Simulation results are presented in this paper.The OFDM signal has a non-constant envelope with large instantaneous power spikes possible primarily resulting in an overdriving of the high power amplifier (HPA) at the transmitter. This leads to nonlinear distortion causing intermodulation noise and spectral spreading. Both effects can be limited by introducing an appropriate input backoff (IBO). In this paper the performance of OFDM signals in the presence of nonlinearities is analysed quantitatively.     

Modeling resistive strips with finite elements for TE polarization

A formulation for modeling RF scattering from infinitely thin resistive strips is developed for TE_z polarization (H-polarisation). finite-element frequency-domain approach using the Galerkin weak form and special gap elements is employed. The resistive strips can be tapered, and immersed in an arbitrary inhomogeneous dielectric/magnetic medium. This formulation has been integrated into an existing finite-element code, and results are given. These results compare well to moment-method solutions     

Macromodeling of nonlinear transistor-level receiver circuits

In this paper, a modeling methodology for macromodeling transistor-level receiver circuits has been presented. A few receiver modeling techniques have been proposed in the past, but these modeling techniques only address the loading effect of the receiver circuits, i.e., the input characteristics of the receivers. In this paper, a modeling methodology that addresses both the loading effect as well as the output characteristics of the receiver has been proposed. This modeling technique is simple, accurate, and has huge computational speed-up over transistor-level receiver circuits. To model the input characteristics of the receiver, spline function with finite time difference (SFWFTD) and recurrent neural network (RNN) modeling methods have been used. The output characteristics of the receiver are modeled using a combination of receiver static characteristics and a delay element that takes into account the timing delay of the receiver. The accuracy of the modeling approach has been tested on some test cases and results show good accuracy and substantial speed-up compare to transistor-level receiver circuits. The proposed modeling technique has been extended to multiple ports to estimate sensitive effects like simultaneous switching noise (SSN) when multiple receivers are switching.     

A frequency-domain approach to interconnect crosstalk simulation and minimization

A frequency-domain approach to efficiently simulate and minimize the crosstalk between high speed interconnects is proposed in this paper. Several methods for modeling coupled microstrip transmission lines are discussed. Several possible simulation strategies are also considered. A straightforward yet rigorous frequency-domain approach is followed. This approach can be used for linearly and non-linearly terminated microstrip coupled lines, since it exploits the harmonic balance technique. A typical example of microstrip interconnects is simulated and the results are compared with those obtained in previous work by other authors using time-domain methods. The simulation method proposed in this work yields good accuracy. A crosstalk minimization problem is formulated and solved following the method proposed.     

Analysis and design of electronic transformers for electric powerdistribution system

A transformer performs many functions such as voltage transformation, isolation and noise decoupling, and it is an indispensable component in electric power distribution systems. However, at low frequencies (60/50 Hz), it is a bulky and expensive component. In this paper, the concept of electronic transformers is further extended and explored for its suitability in power distribution systems. It should be noted that from the input/output behavior, the electronic transformer and the conventional transformer are identical. Possible topologies employing static converters connected on the primary and secondary sides are explored to realize high-frequency operation of the magnetic core. To assist the commutation process, a four-step switching has been developed which does not require the use of snubbers. Reduced size, losses, higher efficiency, and better voltage regulation are some of the advantages of this approach. A 10 kVA design example along with experiment results are discussed. It is shown that a transformer designed with a conventional grain-oriented silicon-steel core can process three times the power at 1 kHz operating frequency as compared to 60 Hz. The proposed method is scalable in voltage/current with the currently available insulated gate bipolar transistor (IGBT) devices connected in series without special snubbers     

Experimental development and evaluations of VF-input high-frequency AC-AC converter supporting distributed power generation

Presented is a novel variable-frequency input ac-ac converter that accepts a wide frequency variation of input raw power. The new converter and control offers a high-frequency control capability, at both input and output sides, that is a magnitude higher than the operating range reported so far in literature. The new converter is designed and experimentally implemented by novel three-in-one integrated bidirectional power modules. High performance at high frequencies of fundamental power control at both input and load sides are verified extensively by experimental evaluations. Voltage-source characteristics are obtained at both input and outsides, thus improving system robustness when subjects to line imbalance and voltage distortion, which is important for distributed-power generation (DPG). The high-frequency excitation can reduce the size and weight of the generating and (or) motoring apparatus. The proposed system benefits the efficiency and power density of future DPG systems driven by variable-speed wind, water, and microturbines.     

A Square-Root Domain Differentiator Circuit

Companding circuits are very useful blocks for realizing low-voltage, high-frequency analog systems. They are implemented using the translinear principle and the quadratic/exponential I-V characteristic of MOS/BJT transistor. In this paper, a Square-Root Domain differentiator is proposed. It is constructed from an appropriate input stage that converts the input current into a compressed voltage at a capacitor's node, and simultaneously senses the capacitor's current. The overall configuration of the differentiator also includes a current geometric-mean circuit and a multiplier, both based on a translinear loop. An attractive characteristic of the proposed circuits is their immunity to body effect. HSPICE simulation results were used for evaluating the behaviour of the differentiator.     

Rapid identification of a sparse impulse response using an adaptive algorithm in the Haar domain

This paper proposes a fast convergence adaptive algorithm for identifying a sparse impulse response that is rich in spectral content. A sparse impulse response is referred here as a discrete time impulse response that has a large number of zero or near zero coefficients. The basic idea for rapid identification is to automatically determine the locations of the nonzero impulse response coefficients for their adaptation and eliminate the unnecessary adaptation of zero coefficients. The proposed method, which is called the Haar-Basis algorithm, employs a transform approach by modeling the sparse impulse response in the Haar domain. The Haar transform has many basis sets and each of them contains basis vectors that span the entire time domain range. This special nature of the Haar transform allows for the selection of one small subset of adaptive filter coefficients whose basis vectors span the entire range of the impulse response. These coefficients are adapted at the beginning and are then used subsequently to identify, from the hierarchical structure of the Haar transform, the rest of the filter coefficients that must be adapted to correctly model the unknown sparse impulse response. The consequence is avoiding adaptation of many zero coefficients, leading to a dramatic improvement in either convergence speed or steady state excess mean-square error (EASE), while requiring no a priori knowledge such as the number of nonzero coefficients in the unknown sparse impulse response. The proposed algorithm has been tested with a variety of unknown sparse systems using both white noise input and colored input whose spectrum closely resembles that of speech. Simulation results show that the new approach provides promising results.     

Generalized Frequency-Domain SAR Processing

The range-Doppler algorithm and the chirp-scaling algorithm (CSA) process synthetic aperture radar (SAR) data with approximations to ideal SAR processing. These approximations are invalid for data from systems with wide beamwidths, large bandwidths, and/or low center frequencies. While simple and efficient, these frequency-domain methods are thus limited by the SAR parameters. This paper explores these limits and proposes a generalized chirp-scaling approach for extending the utility of frequency-domain processing. We demonstrate how different order approximations of the SAR signal in the 2-D frequency domain affect image focusing for varying SAR parameters. From these results, a guideline is set forth, which suggests the required order of approximation terms for proper focusing. A proposed generalized frequency-domain processing approach is derived. This method is an efficient arbitrary-order CSA that processes the data using the appropriate number of approximation terms. The new method is demonstrated using simulated data.      

Detection of Low-Rate Cloud DDoS Attacks in Frequency Domain Using Fast Hartley Transform

Distributed Denial-of-Service (DDoS) attack has been a serious threat to the availability feature of cloud computing. As traditional DDoS attacks are implemented using a huge volume of malicious traffic, the detection of such attacks becomes a naive task. To evade this detection, attackers are moving towards the Low-Rate DDoS (LRDDoS) attacks. The stealthy behavior of LRDDoS attack makes it difficult to get detected due to its low volume traffic. The existing frequency-domain approaches for LRDDoS detection are not feasible in terms of computational and storage requirements. This paper aims to propose a lightweight, accurate, and adaptive approach for the detection of LRDDoS attacks in frequency-domain. In this paper, the LRDDoS attack is detected by analyzing the power spectral distribution. The novelty of the proposed approach is to calculate the power spectral density using Fast Hartley Transform (FHT). The FHT processes real-valued input data, and has low computational and storage complexities. The approach is implemented on OpenStack cloud platform, and the aggregate network traffic (external and internal) is captured and analyzed. Experimental results show that the computational and storage complexities involved in FHT are lower than other transformation algorithms’ complexities. Thus, the approach provides faster response with an average detection time of 60.16 s. The average true negative and true positive rates obtained by the proposed approach are 99.83% and 99.46% respectively, which are competitive.

     

New hybrid controller for systems with deterministic uncertainties

In this paper, a new hybrid controller for systems with deterministic uncertainties is developed. The proposed controller identifies and compensates deterministic uncertainties simultaneously. It is the combination of a time-domain feedback controller and a frequency-domain iterative learning controller. The feedback controller decreases system variability and reduces the effect of random disturbances. The iterative learning controller shapes the system input to suppress the error caused by deterministic uncertainties such as friction and backlash. The control scheme use only local input and output information, no system model is required. The uncertainties can be structured or unstructured. The effectiveness of the proposed controller is experimentally verified on a servo system with gearbox     

基于深度学习的单载波频域均衡算法研究

单载波频域均衡(Single-Carrier Frequency-Domain Equalization,SC-FDE)是一种有效的抗码间干扰的算法,在无线通信系统中得到了广泛的应用.传统线性SC-FDE算法主要包括信道估计、噪声功率估计和信道均衡三个模块,其中每个模块都是单独优化的.为了联合优化这三个模块,本文提出了...     

Timing circuits for RSFQ digital systems

A low-skew frequency divider and clock controller have been designed for high-frequency timing of superconductor rapid single-flux-quantum (RSFQ) digital systems. The circuits have only about 10-ps skew between input and output signals and are applicable for multirate digital systems (e,g., oversampling analog-to-digital converter and bit-serial digital systems). Several circuits have been fabricated in conventional Nb-trilayer technology with a critical current density of 1 kA/cm². The most complex clock controller generates trains of 2²⁴ single-flux-quantum pulses with a period of less than 70 ps. The long-term relative stability of these intervals has been measured to be better than 6×10^-5 . The basic component of the controller, a frequency divider, operates at input frequencies above 85 GHz     

Dynamic resource allocation with beamforming for MIMO OFDM systems: performance and effects of imperfect CSI

We propose three different dynamic resource allocation algorithms using adaptive beamforming for multiple-input multiple-output (MIMO) OFDM systems, and investigate their performance over multipath fading channels under perfect and imperfect channel state information (CSI). These approaches involve the use of adaptive modulation, adaptive frequency-domain power allocation, and/or adaptive sub-channel allocation. By employing the proposed approaches in MIMO/OFDM systems, significant performance improvement can be achieved compared to the conventional adaptive antenna array based OFDM. The investigation of the effects of imperfect CSI reveals that the adaptive-modulation based approach is too sensitive to channel estimation errors, and that its performance is worse than the adaptive frequency-domain power allocation and/or adaptive sub-channel allocation approaches. The performance analysis also shows that combining adaptive power allocation with sub-channel allocation yields the best performance under imperfect CSI while being robust to channel estimation errors.     

Measuring and modeling the effects of substrate noise on the LNAfor a CMOS GPS receiver

The influence of substrate noise coupling on the performance of a low-noise amplifier (LNA) for a CMOS GPS receiver has been investigated both analytically and experimentally. A frequency-domain approach has been used to model both noise injection into the substrate from digital circuitry integrated on the same chip and the mechanisms by which that noise can affect analog circuit behavior. The results of this study reveal that substrate noise can modulate the LNA input signal as well as couple directly to the amplifier's output     

A simple and analytical parameter-extraction method of a microwaveMOSFET

A simple and accurate parameter-extraction method of a high-frequency small-signal MOSFET model including the substrate-related parameters and nonreciprocal capacitors is proposed. Direct extraction of each parameter using a linear regression approach is performed by Y-parameter analysis on the proposed equivalent circuit of the MOSFET for high-frequency operation. The extracted results are physically meaningful and good agreement has been obtained between the simulation results of the equivalent circuit and measured data without any optimization. Also, the extracted parameters, such as g_m and g_ds, match very well with those obtained by DC measurement