Signal Transfer Function Research Articles

A 4th-Order Wideband Sigma Delta Modulator Using Linear System Theory Technique

A 4th-Order Wideband Sigma Delta modulator structure is proposed in this paper, which uses linear system theory technique. There are many implementation techniques to improve the performance of Sigma Delta ADCs, such as noise coupling, differential sampling and dynamic elements matching. An extra loop delay is needed to be added in the system. This paper explains how to make the modulator stable with the addition of feed-forward and feed-back branches which are used to compensate the extra loop delay. Next, we restore the signal and noise transfer functions. A 4th-Order Wideband deltasigma modulator have been designed and simulated to verify the method.

Modeling and Simulation of Controller for Single Phase and Three Phase PWM Rectifiers

This paper presents the modeling of single phase, three phase rectifiers and suitable controller design for the modeled rectifier circuit the primary application of rectifiers is to derive DC power from an AC supply. Virtually all electronic devices require DC, so rectifiers are used inside the power supplies of all electronic equipment. PWM rectifier is now becoming popular due to its low distortion input current, unity power factor operation, bi-directional power flow ability and can offer excellent dynamic response of the dc output voltage. A three-phase PWM rectifier used together with closed-loop dc–dc converters for converting DC power from one voltage to another is much more complicated. In order to perform the above operation rectifier switches should be controlled properly. Hence it is much needed to design a suitable controller for single phase and three phase rectifier. From the small signal transfer function model, the controller scan be designed and the simulated results are presented.

Improved unity‐STF sturdy MASH ΣΔ modulator for low‐power wideband applications

A novel sturdy multi-stage noise-shaping sigma–delta modulator that cancels the first-stage quantisation error at the output of the modulator is presented. Since any stage of the modulator has unity signal transfer function, the modulator would be very robust to circuit non-idealities such as finite op-amp gain. Furthermore, the signal processing timing issue in the critical paths of the proposed topology has been relaxed due to shifting the delay of the last integrator to the feedback path of the modulator. Moreover, this topology can be implemented in the circuit level by a fewer active blocks. Therefore, it practically would be suitable for low-voltage and low-oversampling applications. Simulation results show the usefulness of the proposed modulator.

Analysis of Jitter-Induced Voltage Noise in Clock Channels

Effects of transmit jitter on lossy clock channel are analyzed analytically by treating the 1010 input clock signal as a sinusoidal wave with a phase modulation that represents jitter. Jitter-to-amplitude-modulation transfer functions are derived for sinusoidal jitter, duty-cycle distortion (DCD), and random jitter (RJ) in terms of the signal transfer function or S-parameters. Input jitter is shown to induce amplitude modulation in the output signal as a result of channel dispersion, leading to voltage noise at the channel output. DCD- and RJ-induced voltage noises are found to scale uniquely with channel loss. To verify the theory, numerical simulations are performed on channels with different losses and at various data rates. The input clock signal is represented with a square wave, and the output signal is calculated by linear superposition of the channel step response. Theoretical and simulation results are found to be in excellent agreement.

An improved two-dimensional multiple signal classification approach for impact localization on a composite structure

Efficient impact monitoring techniques are important to be researched to ensure the safety of in-service composite structures. Multiple signal classification–based method is a new promising method. This method uses small aperture sensor array arrangement instead of sparse sensor arrangement. It has the advantage of easy sensor array arrangement. By processing the whole sensor array outputs using the multiple signal classification algorithm, transfer function and material property of the structure are not needed. Although some researches have shown the potential of this new method, most of the current researches have been performed based on the far-field assumption on aluminum structures. In engineering applications, composite structures are the main structures which need impact monitoring. Deep research needs to be addressed. Aiming at these problems, an improved two-dimensional near-field multiple signal classification processing algorithm is presented for impact localization on composite structure in this article. The proposed method can simultaneously estimate the impact occurring direction and distance. A uniform carbon fiber composite plate and a real aircraft oil tank made of carbon composite structure with varied thickness are adopted to evaluate the presented method. To deal with the anisotropy performance of the complex composite, the two-dimensional multiple signal classification processing algorithm is also improved by taking into account the existing anisotropy performance.

Interference rejection in quadrature band-pass $$\varSigma \varDelta $$ Σ Δ modulators

Interference is a major concern in surface acoustic wave-less receiver architectures. This paper presents an architectural solution to design a quadrature band-pass $$\varSigma \varDelta $$ΣΔ modulator in presence of interference signals. These interferences are rejected by using the built-in signal transfer function (STF) filtering action inside the quadrature modulator. The implementation of the STF filtering is achieved by means of feed-forward paths and does not require any additional active blocks. Simulations at the behavioral level on different design examples verify the architecture implementation and the effectiveness of the approach.

High-accuracy infrared simulation model based on establishing the linear relationship between the outputs of different infrared imaging systems

Accurately simulating the output of an infrared imaging system is increasingly important for predicting the operational performance of the system under different conditions. Traditional infrared simulation models need to obtain the actual temperature of the simulated scene, which is quite complex and will introduce various error sources. To solve this problem and improve the accuracy of the simulation results, a novel infrared simulation model is proposed by studying the linear relationship between the outputs of different infrared imaging systems in this paper. This work is accomplished mainly by conducting variables separation and linear approximation on the signal transfer function of infrared imaging system and converting geometric resolution between the outputs of different infrared imaging systems. To verify the simulation model, the output of the mid-wave/long-wave thermal imager is simulated by the proposed model based on the measured output of the long-wave/mid-wave thermal imager, and the simulated results are compared with the measured results. Experimental results show that the simulated results have high accuracy.

A Novel ANN Based UPFC for Voltage Stability and Reactive Power Management in a Remote Hybrid System

Abstract This paper gives a novel idea of application of ANN based UPFC controller for Reactive Power compensation in a standalone hybrid power system and thereby enhances the stability of the system .For the Isolated WECS a linear small signal transfer function model of the hybrid wind Diesel model is considered with different loading conditions. The reactive power compensation and stability analysis have been carried out with UPFC Controller with an IEEE exciter I. A feed forward neural network with back propagation technique is designed to tune the parameters of UPFC controller. From the matlab Simulation it is clear that the system parameters attend steady state value with lesser time and complexities.

Construction of the Lentiviral and Electric Transfection Vectors Encoding Anti-Human CD30 or CD33 Chimeric Antigen Receptor (CAR) Gene and Respective Expression Injurkat Leukemia Cell Line

Adoptive cellular therapy (ACT), as a kind of biological treatment, has played an important role in immunotherapy for malignancies, by which an individual passively acquires the specific immunological rejection to tumor molecular target through cellular infusion, resulting in the suppression or destruction of malignancies. In the early clinical studies, immunotherapies based on tumor-infiltrating lymphocytes (TILs) have demonstrated definitively therapeutic effect on a variety of tumors, especially on melanoma, which underlined feasibility and necessity of ACT in anti-tumor therapies. However, the difficulties on cellular material acquisition, relatively complex cellular constitute, undefined anti-tumor target and unstable efficacy, all of which affected and limited the clinical practice with TILs, in addition to the immune tolerance-inducing behaviors of the tumor itself, such as the immune escape, suppression of the immune effects via peri-tumor microenvironment, down-regulation of MHC to minimize antigen exposure, et al.Chimeric antigen receptor (CAR) has effectively integrated the specific recognition of Ab-Ag and signal transfer function of TCR to form a transmembrane molecule with different functional domains. The expression fragment of CAR could be formed by aligning single chain antibody fragment (scFv) cDNA and costimulatory domain in tandem, which is subsequently transferred via lentiviral vectors to modify autologous T lymphocytes. After gene expression and translation, the CAR has an MHC-independent specific recognition to tumor-associated antigen (TAA), resulting in T cell activation, anti-tumor cytotoxic effort and memory cell differentiation. CAR-modified lymphocytes (CART) are effective ACT tools cells with anti-tumor specificity through gene transfection. Currently, CD19-targeted CART therapy has yielded promising therapeutic effect.Our study selected a lineage-specific CD33 and another tumor-specific CD30 as CAR-associated targets, with which we designed and constructed a series of third generation CAR containing CD28 activation domain and 4-1BB costimulatory domain. The CAR-containing expression vectors were transfected into the Jurkat cell line via lentiviral system and nucleofector electroporation system, respectively.The target gene fragments, anti-CD30-scFv, anti-CD33-scFv, and CD28-4-1BB-CD3ζ sequence encoding T cell activation plus costimulatory signals were amplified from pUC57-CD30-scFv, pUC57-CD33-scFv and pUC57-CD2841BBZ via PCR. The separated scFv and signal sequence were linked into a continuous fragment, CAR-CD30 and CAR-CD33 cDNA, by overlapping PCR, which were subsequently subcloned into a lentiviral expression vector, pCDH-CMV-MCS-EF1-Puro, to construct recombinant lentiviral vector pCDH-CAR30 and pCDH-CAR33; the electric transfection vector pmax-CAR30 and pmax-CAR33 were constructed as well.With virus packaging, the corresponding CARs/GFP/Blank-containing virus were added into Jurkat cell medium, which were immediately centrifuged to facilitate infection; puromycin was used to screen Jurkat strains highly expressing CAR, CAR-modified Jurkat strains were thus harvested one week from antibiotic screening, named as: Jurkat-pCDH-Blank, Jurkat-pCDH-GFP, Jurkat-pCDH-CAR30 and Jurkat-pCDH-CAR33, whose protein samples were then extracted for CAR detection.The Jurkat cells could also be effectively transfected by applying an electrical pulse to momentarily create small pores in cell membranes, with the aid of pmax-CAR30 or pmax-CAR33, moreover, different discharge mode was designed to yield higher cell viability, and otherwise higher transfection efficiency. The fluorescent signal could be observed 24h from electric pulse and protein samples could be extracted at the same time.After one-week screening with puromycin, fluorescence from Jurkat cells infected with GFP-containing virus were detected. Electroporation was used as an alternative procedure to produce CAR-modified Jurkat cell line, and the transfection efficiency was higher than lentiviral system did, approximately 90%, by GFP observation. The expression of CAR-CD30 and CAR-CD33 were also successfully detected by western blot in Jurkat cells, indicating a preliminary and technical basis ahead of in-depth study on ACT and CART agent preparation. DisclosuresNo relevant conflicts of interest to declare.

A Continuous-Time 0–3 MASH ADC Achieving 88 dB DR With 53 MHz BW in 28 nm CMOS

We present design and measurement details for a 0-3 multi-stage noise-shaping (MASH) ADC that achieves a dynamic range of 88 dB over 53 MHz signal bandwidth. The ADC utilizes a zeroth-order front-end, i.e., a 17-level flash ADC, to perform a coarse quantization and a third-order 7-level continuous-time ΔΣ back-end to digitize the residue error of the front-end. The ADC achieves the high thermal noise power efficiency of a continuous-time feedforward ΔΣ modulator and the flat signal transfer function of a flash ADC. The test chip, implemented in a 28 nm CMOS process, clocks at 3.2 GHz. The average noise spectral density with small input signals is -167 dBFS/Hz and the dynamic range is 88 dB. The test chip ADC consumes a total power of 235 mW from triple power supplies of 0.9/1.8/-1.0 V. The thermal-noise figure-of-merit, defined as FOM = DR + 10log 10 (BW/P) is 171.6 dB.

A Second-order Harmonic Current Reduction with a Fast Dynamic Response for a Two-stage Single-phase Grid-connected Inverter

In a single-phase grid-connected power system consisting of a DC/DC converter and a DC/AC converter, the current drawn from renewable energy sources has a tendency to be pulsated and contains second-order frequency ripple components, which results in several drawback such as a power harvesting loss and a shortening of the energy source's life. This paper presents a new second-order harmonic current reduction scheme with a fast dc-link voltage loop for two-stage dc-dc-ac grid connected systems. In the frequency domain, an adequate control design is performed based on the small signal transfer function of a two-stage dc-dc-ac converter. To verify the effectiveness of proposed control algorithm, a 1 kW hardware prototype has been built and experimental results are presented.

Design Techniques for Continuous-Time ΔΣ Modulators With Embedded Active Filtering

Continuous-time ΔΣ modulators (CTDSM) used in wireless systems need to process signals in the presence of interferers. Peaking in the Signal Transfer Function of a conventional design necessitates a higher in-band dynamic range to accommodate interferers. A filter up front solves this problem at the expense of increased power dissipation and degraded linearity of the signal chain. Embedding the filter in the modulator achieves the same objective in a power efficient manner, while improving out-of-band linearity and reducing active area. However, having the filter inside a ΔΣ loop can be problematic with respect to stability. We show that such a system can be stabilized in a robust manner without extra hardware. Measurements of a CTDSM (signal BW = 2 MHz), with a built-in VGA (0 to 18 dB) and a second order Butterworth filter (4 MHz cutoff), show that the in-band/out-of-band IIP 3 improves by about 3/10 dB when compared to the filter-CTDSM cascade, and achieves a similar dynamic range and consumes 25% lower power.

Simplified Analysis and Simulation of the STF, NTF, and Noise in Continuous-Time <inline-formula> <tex-math notation="TeX">$\Delta\Sigma$</tex-math></inline-formula> Modulators

Determining the signal transfer function (STF), noise transfer function, and in-band thermal noise spectral density of a continuous-time delta-sigma modulator (CTDSM) is challenging due to the periodically time-varying nature of the system. This is particularly so when the loop filter is also time-varying, like in the case of a modulator using a switched-capacitor (SC) feedback digital-to-analog converter (DAC). In this brief, we use the adjoint network to greatly simplify the analysis and simulation of the STF and noise in CTDSMs with SC feedback DACs. First- and third-order modulators are used to illustrate the efficacy of our techniques.

A Wideband 400 MHz-to-4 GHz Direct RF-to-Digital Multimode <formula formulatype="inline"><tex Notation="TeX">$\Delta\Sigma$</tex> </formula> Receiver

A wide-tuning-range low-power sigma-delta-based direct-RF-to-digital receiver architecture is implemented in 65 nm CMOS. A flat signal transfer function is chosen to support wide-frequency-range radios. A multilevel (two-bit) nonreturn-to-zero DAC improves jitter immunity to enable a high dynamic range, and, with a class-AB low-noise transconductance amplifier, guarantees a highly linear front end. For a 4 MHz signal, the peak SNDR of the receiver exceeds 68 dB and is better than 60 dB across the 400 MHz to 4 GHz carrier frequency range. By virtue of utilizing a negative feedback digitizer close to the antenna, an IIP3 of +10 dBm is achieved while dissipating only 40 mW from 1.1 V/1.5 V supply voltages.

Notes on “Small Signal Analysis of Energy Factor and Mathematical Modeling for Power DC–DC Converters”

In paper (IEEE Trans. Power Electron., vol. 22, no. 1, pp. 69-79, Jan. 2007), large signal and small signal transfer function models of dc-dc power converters are obtained using concept of energy factor (EF) and its associated parameters. In sections II-D and II-E of the original paper, authors describe that the two key parameters of the transfer function are independent of conduction duty cycle k. This is not true and the correct small signal analysis is also reported.

Harmonic analysis of GaN-HEMTs at different temperatures and frequencies using Volterra power series

In this study, the detailed harmonic analysis of GaN high electron mobility transistor (HEMT) at different temperatures and frequencies is presented. Volterra power series and multi-dimensional Laplace transform are used as a method. The Volterra power series is also solved up to third degree, and the small signal transfer functions of kernels (H1, H2 and H3) are obtained. The relationship between drain inductance (Ld), gate–source voltage (Vgs), impedance (ZL) and the effect of frequency (Fr) to the output gain is identified. Besides, the nonlinear gains of H1, H2 and H3 kernels of the GaN-HEMT are obtained. The inverse relationship between the output gains of H1, H2 and H3 kernels are derived. An unsuitable situation has also been identified for sub-carrier inter-modulation systems. In addition, an asymmetric structure is also obtained between the output gain of H2 and side-band frequencies. The effects of other parameters are carried out for the output gain.

A Review to AC Modeling and Transfer Function of DC-DC Converters

In this paper, AC modeling and small signal transfer function for DC-DC converters are represented. The fundamentals governing the formulas are also reviewed. In DC-DC converters, the output voltage must be kept constant, regardless of changes in the input voltage or in the effective load resistance. Transfer function is the necessary knowledge to design a proper feedback control such as PID control to regulate the output voltage as linear PID and PI controllers are usually designed for DC-DC converters using standard frequency response techniques based on the small signal model of the converter. DOI: http://dx.doi.org/10.11591/telkomnika.v13i2.7033

A Single Opamp Third-Order Low-Distortion Delta-Sigma Modulator with SAR Quantizer Embedded Passive Adder

A third-order low-distortion delta-sigma modulator (DSM), whose third-order noise-shaping ability is achieved by just a single opamp, is proposed. Since only one amplifier is required in the whole circuit, the designed DSM is very power efficient. To realize the adder in front of quantizer without employing the huge-power opamp, a capacitive passive adder, which is the digital-to-analog converter (DAC) array of a successive-approximation-type quantizer, is used. In addition, the feedback path timing is extended from a nonoverlapping interval for the conventional low-distortion structure to half of the clock period, so that the strict operation timing issue with regard to quantization and the dynamic element matching (DEM) logic operation can be solved. In the proposed DSM structure, the features of the unity-gain signal transfer function (STF) and finite-impulse-response (FIR) noise transfer function (NTF) are still preserved, and thus advantages such as a relaxed opamp slew rate and reduced output swing are also maintained, as with the conventional low-distortion DSM. Moreover, the memory effect in the proposed DSM is analyzed when employing the opamp sharing for integrators. The proposed third-order DSM with a 4-bit SAR ADC as the quantizer is implemented in a 90-nm CMOS process. The post-layout simulations show a 79.8-dB signal-to-noise and distortion ratio (SNDR) in the 1.875-MHz signal bandwidth (OSR=16). The active area of the circuit is 0.35 mm2 and total power consumption is 2.85 mW, resulting in a figure of merit (FOM) of 95 fJ/conversion-step. key words: delta-sigma modulator, DSM, opamp sharing, relaxed dynamic element matching (DEM) timing

3-D Electromagnetic Modeling of EMI Input Filters

In this paper, a novel 3-D electromagnetic modeling approach which enables electromagnetic compatibility (EMC) analysis of power converter systems in an accurate and computationally efficient way is presented. The 3-D electromagnetic modeling approach, implemented in the EMC simulation tool GeckoEMC, is based on two numerical techniques, the partial element equivalent circuit method and the boundary integral method (PEEC-BIM). The developed PEEC-BIM coupled method enables comprehensive EMC analysis taking into account different effects of the PCB layout, self-parasitics, mutual coupling, shielding, etc., which in turn provides a detailed insight into the electromagnetic behavior of power electronic systems in advance to the implementation of hardware prototypes. The modeling features of the GeckoEMC simulation tool for virtual design of electromagnetic interference (EMI) filters and power converters is demonstrated on the examples of a single-phase two-stage EMI filter and a practical EMI filter for a single-phase PFC input stage. Good agreement between the PEEC-BIM simulation and the small signal transfer function measurement results is achieved over a wide frequency range, from dc up to 30 MHz. The EMC simulation environment enables a step-by-step EMC analysis distinguishing the impact of various electromagnetic effects on the EMI filter performance and allowing an optimal EMI filter design.

High‐loop‐delay sixth‐order bandpass continuous‐time sigma–delta modulators

This study focuses on the design of high-loop-delay modulators for parallel sigma-delta conversion. Parallel converters, allowing a global low oversampling ratio, consist of several bandpass modulators with adjacent central frequencies. To ensure the global performance, the noise transfer function (NTF) of each modulator must be adjusted regarding its central frequency. In this thematic a new topology of sixth-order modulators based on weighted-feedforward techniques is developed. This topology offers an adequate control of the NTF at each central frequency by simple means. Additive signal paths are moreover proposed to obtain an auto-filtering signal transfer function. An optimisation method is also developed to calculate the optimised coefficients of the modulators at different central frequencies. The main concerns are improving the stability and reducing the sensitivity of the continuous-time circuit to analogue imperfections. This is essential for parallel conversion since, in each channel, the modulator works at a central frequency which differs from the fourth of the sampling frequency. The performance of the optimised modulator is compared with its discrete-time counterpart with good argument.