Low-pass Negative Group Delay Research Articles

Transient Characterization of New Low-Pass Negative Group Delay RC-Network

Transient Characterization of New Low-Pass Negative Group Delay RC-Network

COVID-19 cases prediction with negative group delays digital function

The negative group delay (NGD) is an uncommon function enabling to propagate arbitrary waveform signals with time-advance behavior. The counterintuitive NGD function was initially experimented for anticipating typically fast and short duration electronic signals in micro- and milli-second time scale. The application of NGD function to large time scale signal attracts more and more the attention of data processing engineer. This paper aims to investigate on the ability of NGD function to predict time- dependent social data with someday time-advances. As practical case of study, an innovative application of NGD function for predicting disease cases is treated. The digital circuit theory enabling to understand the low-pass (LP) NGD canonical TF and the characterization approach is established. It is shown in which condition the first order difference equation represents a LP-NGD circuit. Then, the design method of typical LP-NGD predictor as numerical circuit is introduced in function of the expected time-advance. The NGD predictor time-variation property is theoretically initiated. The NGD time-advance varied from -7 days to -1/2 days is investigated with deterministic data prediction processing from 5-months bi- exponential waveform data. The predicted data with time-advance of about -4 days was confirmed by analytical computation and simulation. The LP-NGD digital predictor feasibility is validated with monthly COVID-19 randomly arbitrary data by computed and virtually tested results. It was investigated with sensitivity analysis that the prediction performance is better when the input signal is smoothed enough. As expected, prediction result showing very good correlation with input data is demonstrated.

Design and Experimentation of Inductorless Low-Pass NGD Integrated Circuit in 180-nm CMOS Technology

This article introduces an innovative design of a low-pass (LP) negative group delay (NGD) integrated circuit (IC) in the 180-nm CMOS technology. The LP-NGD circuit is an inductorless topology constituted by RC-network with CMOS metal-insulator-metal (MIM) capacitor and polygate resistor. The design methodology is illustrated by considering the chip layout process. Then, the first run simulation is performed with the design rule check (DRC) and 2.5 mm <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${\times }$ </tex-math></inline-formula> 2.2 mm layout versus schematic (LVS) approaches. The feasibility of the CMOS LP-NGD IC circuit implementation is validated with chip-onboard (CoB). The proof of concept (PoC) of the LP-NGD miniaturized circuit was tested in both S-parameter and time domain (TD). As expected, the calculated, simulated, and experimented results of CoB showing NGD of about −10 ns over 12 MHz and −10 dB attenuation are confirmed. The active CMOS LP-NGD technology compensates the insertion loss to 2.4 dB, the GD reaches −11 ns, and the reflection loss reaches −20 dB. Moreover, TD investigations were also performed to show the feasibility of generating pulse and arbitrary waveform signal time advance through the designed and fabricated LP-NGD CoB prototypes.

Low-Pass NGD Numerical Function and STM32 MCU Emulation Test

This article introduces an original microcontroller unit (MCU) design of numerical low-pass (LP) negative group delay (NGD) function. The innovative theory of the numerical LP-NGD function is developed based on the first-order analog transfer function discretization. The infinite impulse response (IIR) LP-NGD is fundamentally formulated in function of the desired NGD value, cutoff frequency, gain, and the MCU sampling frequency. A STM32 MCU proof-of-concept (POC) is tested to implement the IIR LP-NGD function. Different real-time tests with visualization of input and output analog signals from the MCU LP-NGD POC were performed. As expected, time-advance demonstration tests with milli-second short- and several hour long-duration time-scale with arbitrary waveform signals from temperature and humidity sensors. The signal time-advance is not in contradiction with the causality. The proposed digital MCU function opens a potential future industrial application of LP-NGD function via sensored signal anticipation.

Pre-Detection Sensing With Multistage Low-Pass Type Negative Group Delay Circuit

This paper reveals a fascinating pre-detection technique of sensor signals by means of counterintuitive negative group delay (NGD) electronic function. The sensor signal pre-detection technique is unconventionally developed thanks to the engineering of low-pass (LP) type NGD circuit. The NGD pre-detection basic principle is introduced. After topological description, the LP-NGD cell design method in function of negative time delay specification is formulated. An innovative analysis of time-advance property related to multi-stage LP-NGD cell is elaborated. To demonstrate the LP-NGD pre-detection technique feasibility, a proof of concept (POC) is designed with fabricated 3-stage LP-NGD printed circuit board (PCB) prototype integrating 4 LED detectors. The NGD pre-detection experimental setup is described. Extraordinary pre-detection with −0.5 s negative time propagation visible with LED on-lightning is demonstrated by considering a sinc pulse input signal. The developed NGD pre-detection technique can be useful in the future for the anticipation of industrial equipment damages and failure pre-detection sensor system in real-time.

Thermal Wave Variation Anticipation Under Minute Scale Time-Advance With Low-Pass NGD Digital Circuit

Over the emerging industry 4.0 era, the building control system performance depends on the development of smart sensor technology. Nowadays, the building control engineers challenge on the design of high-capacity smart sensor susceptible to operate with high speed of data processing. In this context, this paper introduces a pioneer research work on the negative group delay (NGD) circuit original application for room temperature anticipation useful for smart-building control. The real-time anticipation of sensor data by using a low-pass (LP) NGD digital circuit is studied. This approach enables minimizing the latency time for optimizing control action. The unfamiliar LP-NGD digital circuit design method and theoretical formulation are described for anticipating thermal wave experimentation in real-time. The digital circuit equation coefficients are computed regarding the time-advance of anticipated thermal completely arbitrary waveform signal. The main interest of using the NGD method-based for thermal wave anticipation regarding temperature variation from heater and freezer control is demonstrated. The anticipation feasibility is illustrated from the minute scale time-advance LP-NGD digital circuit implemented on the STM32® microcontroller unit. The NGD characterization is performed from frequency domain analysis and cosine waveform pulse transient test. Then, the -30 seconds to -10 seconds real-time-advance of temperature variation is verified by calculation and experimentation. The present study result opens a promising NGD method application for the advanced fault control of a future industrial system by anticipating system failures.

A Novel Band-Stop Filter with Band-Pass, High-Pass, and Low-Pass Negative Group Delay Characteristics

A band-stop filter with three different negative group delay functions in the passband, namely, band pass, high pass and low pass, is proposed, which has small insertion loss. The capacitance, inductance, and resistance meet different conditions, and the circuit can realize three different negative group delay characteristics. The theoretical calculation and equation derivation are given. A band-stop filter with negative group delay function is fabricated, and the measured results are basically consistent with the simulation results. The correctness of the design is verified.

Study and experimentation of a 6-dB attenuation low-pass NGD circuit

Because of its counterintuitive nature, the Negative Group Delay (NGD) remains as an uncommon and unfamiliar electronic function. For this reason, the design and analysis of NGD circuits are not well-known for most of electronic designers. This paper initiates a basic and easy to understand theory, in addition to a design methodology for the low-pass NGD function. The circuit theory on the low-pass NGD function is described using an NGD passive topology which is constituted by a RC-parallel network with a resistive load. The NGD analysis and synthesis equations in function of NGD specifications are provided and a proof-of-concept of 6-dB low-pass NGD circuits has been designed, simulated, fabricated and tested. Frequency and time domain analyses have been performed to validate the low-pass NGD function. Theoretical and simulated results are in very good agreement and an NGD has been obtained in measurement for the proposed structure.

Design and Synthesis of Inductorless Passive Cell Operating as Stop-Band Negative Group Delay Function

This paper develops an original circuit theory of unfamiliar stop-band (SB) negative group delay (NGD) topology. The proposed NGD topology is implemented without inductor component. The developed theory is established with passive cell constituted by RC-network based high-pass (HP) and low-pass (LP) NGD composite circuits. The analytical investigation of the SB-NGD circuit is introduced from the elaboration of voltage transfer function (VTF). The canonical form enabling to identify SB-NGD circuit is analytically expressed. The different SB-NGD characteristics as GD value, and, center and cut-off frequencies are innovatively formulated in function of the circuit resistor and capacitor components. The existence condition of SB-NGD function is also established. The inductorless SB-NGD topology is validated by a proof-of-concept (POC) circuit implemented by surface-mounted-device (SMD) component based printed circuit board (PCB). The measured VTF magnitude and group delay (GD) are extracted from the experimented S-parameters. A good agreement between the calculated, simulated and measured results is obtained. The SB-NGD behavior has measured center frequency of about 32 MHz. The lower- and upper-NGD cut-off frequencies are about 9.15 MHz and 98.3 MHz. The optimal NGD values at low and higher frequencies are −3.25 ns and −56 ps.

Low-Pass NGD Voice Signal Sensoring With Passive Circuit

Nowadays, the speech signal processing is still challenging with the multimedia ubiquity. Classical signal processing techniques as filtering were developed for the speech enhancement to overcome unintentional effects as the propagation channel. However, the delay effect remains an open challenge for audio signal processing engineers. A voice/song signal (VSS) prediction is investigated theoretically and experimentally in this paper. This VSS engineering allows to predict an arbitrary waveform signal by using a lowpass negative group delay (NGD) function. This outstanding function presents the VSS advance properties when its parameters are matched with the operated signals. This NGD engineering analytical approach is described with the audio signal processing. The low-pass NGD analysis and property are deeply investigated with two NGD RC-and RL-passive cells. NGD transient study is performed with parametric analytical signals presenting raised cosine waveform. The introduced VSS NGD sensoring is verified with experimental real-time tests of microphone VSS generator. VSS time-advance of approximately 50 μs was observed with a good agreement between simulations and measurements.

Anticipating Actuator Arbitrary Action With a Low-Pass Negative Group Delay Function

This article investigates the feasibility of anticipating arbitrary signals from mechanical actuators. The anticipator originally operates with a low-pass negative group delay (NGD) function. The properties that enable NGD active topology to realize signal anticipation are analytically described. The NGD design and synthesis method as a function of the operating signal bandwidth is established. A real-time demonstration of the motion anticipation is originally performed with a rotating tunable resistor. Second-order motion angle anticipations are realized by completely considering the arbitrary waveform signals. The relevance of the motion anticipation is confirmed with more than a correlation coefficient between the NGD input and output signals that is more than 90%. Innovative real-time predictions of approximately −0.3 s are demonstrated. The present study indicates potential industrial applications of the NGD function in anomaly detections, future smart engines, and smart factories.

Innovative Theory of Low-Pass NGD via-Hole-Ground Circuit

The via ground (GND) structure constitutes one of the most useful elements for designing high performance printed circuit boards (PCBs). The electrical interconnections with vias become key regular solutions for the implementation of various electronic functions. However, so far, the vias are never being used for designing negative group delay (NGD) circuit. To answer this curious question, an original study on the design feasibility of low-pass NGD function with via ground is introduced in the present paper. After the topological description, the NGD analysis in function of the via parameters is established. The design equations allowing to synthesize the via in function of NGD function specifications are formulated. The developed NGD theory is verified with comparisons between calculations and simulations with a commercial tool. As expected, NGD value in order of hundred-picoseconds over hundred-megahertz cut-off frequencies is obtained with good agreement between the theoretical model and simulation. Furthermore, time domain analyses confirm that the via NGD structure enables to generate output signals in time-advance of arbitrary waveform input signals presenting limited bandwidth.

Reconstruction Technique of Distorted Sensor Signals with Low-Pass NGD Function

This paper develops a new reconstruction technique of undesirable signal distortion generated by sensor electronic circuits. The introduced reconstruction technique is originally realized with unfamiliar low-pass negative group delay (NGD) function. The feasibility condition of the proposed reconstruction technique in function of the sensor signal spectrum bandwidth under consideration is elaborated. The reconstruction technique principle is theoretically introduced by means of identification of low-pass NGD function parameters and the appropriated circuit topology. The unfamiliar low-pass NGD function analysis and synthesis equations are established. As an example, for the feasibility study, an RC-network based low-pass active cell is considered to implement the low-pass NGD function. A design method of NGD circuit in function of the sensor distortion transfer function is described in different successive steps. The developed NGD reconstruction technique is validated by different proofs of concept. First, transient simulations are carried out with Gaussian and sinc analytical signals. Then, experimental feasibility study is also performed with arbitrary waveform signal. As expected, the NGD reconstruction technique efficiency is confirmed with improvement of distorted signal integrity parameters and cross correlation better than 97%.

Design of Multi-Scale Negative Group Delay Circuit for Sensors Signal Time-Delay Cancellation

This paper develops an innovative method of sensors’ time-delay suppression. The proposed delay cancellation technique is highlighted with a theoretical concept and time-domain experimental demonstrations by using the negative group delay (NGD) function. The analytical investigation is elaborated with an NGD topology constituted by a simple active $RC$ network. It is established theoretically that this active cell behaves like a low-pass NGD topology. The synthesis equations enabling to calculate the NGD cell parameters as a function of the desired NGD and gain are formulated. Frequency- and time-domain analyses showing the NGD function in multi-time scale are discussed. The NGD function verification is fulfilled with the design and fabrication of a proof-of-concept prototype. Nano-, micro-, and milli-second NGD effects are numerically and experimentally proved. As expected, time-domain experimental demonstrations showing arbitrary waveform signal in outstanding time-advance are realized. Moreover, the feasibility of the signal delay cancellation with 1- and 8-m length cables is experimented. The developed NGD time-delay cancellation demonstrations open the potential applications for the sensor performance improvement.

Time-Domain Experimentation of NGD ActiveRC-Network Cell

A theoretical and experimental investigation of low-pass negative group delay (NGD) topology is introduced. The NGD topology is composed of a low noise amplifier (LNA) and RC-parallel series mounted lumped network. The NGD cell theoretical characterization is elaborated. The NGD properties as NGD level, cut-off frequencies and central frequency are established. The synthesis formulas as function of the expected NGD level and gain are established. The NGD proof of concept using monolithic LNA LEE-9+ manufactured by mini-circuits are designed, simulated, fabricated, and measured. The simulated and measured frequency domain results are in good agreement with the circuit theory. As expected, low-pass NGD behavior is observed with −5 ns-NGD level over 32-MHz bandwidth. The low-pass NGD function meaning is illustrated by the advance of the output pulse signal leading and trailing edges compared to the input ones.

Negative Group Delay Theory of a Four-Port RC-Network Feedback Operational Amplifier

An innovative negative group delay (NGD) theory based on a unity direct chain feedback (UDCF) circuit topology is developed in this paper. This NGD circuit is an active cell constituted by an operational amplifier in feedback with a four-port RC-network. This NGD circuit theory is developed based on the S-parameter model analytically established from the equivalent impedance matrix. The UDCF group delay frequency response is expressed as a function of the feedback RC-cell and the operational amplifier parameters. The NGD analysis of the developed UDCF cell is introduced. According to theoretical analysis, under a certain condition, the UDCF topology is susceptible to behave as a low-pass NGD function. The UDCF cell NGD characteristics are defined theoretically. The theoretical prediction is verified numerically and experimentally in both the frequency- and time-domain by designing and fabricating an active PCB prototype. The simulations and experimentations show that the UDCF circuit exhibits an NGD of approximately -38 ns with NGD cut-off frequency of about 5.5 MHz. More importantly, it is demonstrated in the time-domain that the low-pass NGD effect enables the UDCF cell to generate advanced output with sinc waveform input voltages.

Unity direct chain with feedback series impedance based innovative negative group delay circuit

An innovative negative group delay (NGD) circuit theory on unity direct chain (UDC) topology is developed in this paper. The NGD UDC cells are based on the operational amplifier adder with feedback series impedance. Innovative topologies of high-pass NGD UDC cell composed of RL-series network, all-pass RC-parallel network and low-pass RC-series network are identified. It is a first time that all-pass NGD original topologies are defined. NGD analyses and synthesis methods of each NGD UDC cells are provided. The UDC cell based NGD functions are validated with SPICE simulations. The proofs-of-concept (POC) of UDCs behave as all-pass and low-pass NGD functions with group delay equal to −1 ms at very low frequencies. The low-pass NGD cut-off frequency is 424 Hz. The high pass NGD circuit generates −1 µs at the optimal NGD frequency of about 5.15 kHz. Further analysis of the operational amplifier gain and bandwidth effects is performed. The operational amplifier gain affects significantly the NGD level and bandwidth for the all considered UDC cells. Nevertheless, only the RC-parallel feedback based UDC cell is particularly sensitive to the operational bandwidth.

The Design Method of the Active Negative Group Delay Circuits Based on a Microwave Amplifier and an RL-Series Network

This paper addresses a circuit theory regarding the negative group delay (NGD) principle. The methodology for characterizing this unfamiliar NGD function is described. The basic NGD topology under study is typically an active cell composed of an RF low-noise amplifier (LNA) and an RL-series passive network. It acts as a low-pass NGD topology. The family of the bandpass NGD cell is identified from the low-pass to the bandpass transform. The NGD circuit theory under study is essentially built with the S-parameter approach. The main characteristics of the proposed NGD topology and properties of the NGD level, cut-off frequencies or bandwidth, central frequency, and figure-of-merit are established. The NGD cell is synthesized using the LNA S-parameter model. A method for designing the low- and bandpass NGD cells as a function of the specified NGD values is presented. The NGD cell parameter calculations as functions of the expected NGD level, insertion loss, and reflection coefficient are introduced. Proof-of-concept NGDs are synthesized, designed, simulated, and fabricated to understand and validate the proposed NGD low-pass and bandpass functions. As expected, low-pass and bandpass NGD aspects are obtained. The low-pass NGD circuits present an NGD level of approximately −5 ns over the bandwidth fc = 25 MHz. Next, bandpass NGD circuits were synthesized to operate at approximately 0.5 GHz over the bandwidth $\Delta \text{f}\,\,=50$ MHz with an NGD level of approximately −10 ns. The measured results of the low-pass and bandpass NGD are in good agreement with the theoretical prediction obtained with simple lumped circuits. Different applications of the unfamiliar NGD function are described.

Theory on negative time‐delay looped system

An innovative theory on the looped system generating negative time delay is presented. Both the direct and delayed feedback loop topologies of this system essentially consist of an independent-frequency gain and time-delay block. It is shown theoretically that for suitable parameters the system can generate a negative time delay by virtue of a negative group delay (NGD). Analytical expressions reveal that the system presents an unconditional low-pass NGD behaviour. The NGD properties as a function of the system parameters are derived. To demonstrate the feasibility of the developed NGD system concept, frequency- and time-domain analyses are performed with Matlab, resulting in a very good agreement between the simulations and theory. Furthermore, as illustrated by computational results, negative time-delay signal propagation (signal advance) is obtained. The proposed NGD system can potentially be useful for time-delay compensation in engineering systems.

On low-pass, high-pass, bandpass, and stop-band NGD RF passive circuits

The negative group delay (NGD) function is one of the most intriguing phenomena that can be encountered in area of physics. Since the first experiments in the early 1980s, this abnormal phenomenon remains unfamiliar to conventional engineering. Based on physical, analytical, and experimental investigations, it was found that the NGD phenomenon corresponds to the advanced effect of a pulse signal at baseband frequency. This paper introduces the basic understanding of this extraordinary phenomenon. The RF and microwave-circuit theory dedicated to NGD passive circuits based on the S-parameter modeling is established. Two general types of lumped-element-based RF passive topologies, constituted of simple parallel and series mounted impedances, are explored. Low-pass, high-pass, bandpass, and stop-band elementary topologies of passive cells are treated and characterized. The low-pass NGD cells are first-order passive circuits consisting of RL-series mounted in parallel and RC-parallel networks mounted in series. The different steps of the circuit-parameter calculations as functions of the expected NGD level, insertion loss, and reflection coefficient are explained. To validate the theory, proofs-of-concept (POC) of NGD passive circuits were synthesized, designed, and simulated. As predicted in theory, the simulation results confirmed the feasibility of the low-pass, high-pass, bandpass, and stop-band NGD functions. The NGD circuits respected the basic criteria of RF and microwave circuits with reflection coefficients better than −12 dB. Despite the attenuation, the simulated low-pass NGD cell presented an NGD level of about −1 ns and a cutoff frequency equal to 46 MHz. The high-pass NGD cell presented a group-delay frequency response opposite to the low-pass NGD cell. The bandpass NGD cell exhibited an NGD level of about −2 ns at the center frequency of 0.5 GHz, and a bandwidth of about 92 MHz. Furthermore, the counterintuitive time-advance effect, induced by the NGD phenomenon, proven with various arbitrary-waveform baseband signals, was observed. A pulse advancement of about −1 ns was obtained with the considered low-pass passive cell.