Feedback Transformation Research Articles

A 7.3–14.2 GHz 6.3 mW LNA with 9.4±0.6 dB gain using transformer feedback and peak-gain distribution

This article presents a wideband low-noise amplifier (LNA) with low power consumption and flat gain, implemented in a 180 nm CMOS technology. This LNA uses low voltage operation and current-reuse technology to reduce power consumption, and its cascaded structure is composed of a common-source (CS) stage with gate-source transformer feedback and a cascode stage. The T-coil structure is employed for inter-stage and output matching to expand bandwidth and adjust peak gain, while achieving in-band flat gain through the peak gain distribution technology. Measured results show that the LNA achieves a flat gain of 9.4 ± 0.6 dB over the 7.3–14.2 GHz frequency band, with a 3 dB bandwidth of 6.3–14.6 GHz and an in-band noise figure (NF) of lower than 4.2 dB. The core chip area is 0.29 mm2, and the power consumption is only 6.3 mW.

An Improved Predictive Controller for PMSM based on Dual-Channel Feedback

Abstract High-performance and high-power-density DC servo drives of permanent magnet synchronous motors (PMSM) are applied to the military, especially in airborne optoelectronic pods, light mines, and launch turntables in the aerospace field. The above application scenarios require the volume of drivers to be smaller and have large power outputs. In the field of pods and light mines, high bandwidth and good tracking performance are required, especially in terms of steady-state accuracy. Since light mines are used for target tracking scanning, the errors at the end of the optical rotating mechanism are amplified tens or even hundreds of times after transmission through the line of sight to the target end. Therefore, the requirements for steady-state accuracy are extremely high. In this article, a predictive control method is proposed, using a sliding mode variable structure controller to make up for the error arising from system parameter changes in predictive control. Finally, a dual-channel rotary transformer feedback position coarse-fine combination algorithm method is studied to reduce the angular measurement error and further improve steady-state accuracy.

Ultra-Wideband Transformer Feedback Monolithic Microwave Integrated Circuit Power Amplifier Design on 0.25 μm GaN Process.

This paper presents an ultra-wideband transformer feedback (TFB) monolithic microwave integrated circuit (MMIC) power amplifier (PA) developed using a 0.25 μm gallium nitride (GaN) process. To broaden the bandwidth, a drain-to-gate TFB technique is employed in this PA design, achieving a 117% relative -3 dB bandwidth, extending from 5.4 GHz to 20.3 GHz. At a 28 V supply, the designed PA circuit achieves an output power of 25.5 dBm and a 14 dB small-signal gain in the frequency range of 6 to 19 GHz. Within the 6 to 19 GHz frequency range, the small-signal gain exhibits a flatness of less than 0.78 dB. The PA chip occupies an area of 1.571 mm2. This work is the first to design a power amplifier with on-chip transformer feedback in a compound semiconductor MMIC process, and it enables the use of the widest bandwidth power amplifier on-chip transformer matching network.

A metal object detection system for electric vehicle wireless charging based on LC oscillating circuit and reverse-winding-incorporated detection coils

In magnetically coupled wireless charging systems for electric vehicles, it is common for metal objects to enter the charging system. In this case, the strong magnetic field of wireless charging causes an eddy current effect in the metal object, which generates a large amount of heat. This heat accumulation poses a risk of fire. In this paper, a novel metal object detection system designed for wireless charging of electric vehicles is proposed. The system utilizes the principle that the coil impedance and coupling coefficient change with the presence of metal objects, and a set of composite coils is designed to improve the sensitivity of detection. The detection coil and feedback coil in the composite coil are decoupled by reverse series connection. An LC oscillating circuit based on transformer feedback is used to detect metal objects, and the circuit can make good use of the parameter changes of the composite coil. Finally, an experimental platform for wireless charging metal detection in electric vehicles has been built to validate the proposed system. Through testing, it has been demonstrated that the system can detect the presence of metal objects in a timely and accurate manner.

A Folded Cascode CMOS Low Noise Amplifier with Transformer Feedback

This study proposes a folded cascode CMOS low noise amplifier (LNA) with transformer feedback, implemented using a 0.13-μm CMOS process for wireless local area network front-end module applications. Compared to a conventional cascode inductive source degeneration LNA (ISDLNA), the folded cascode ISDLNA significantly improved the input-referred third-order intercept point (IIP3) as well as the 1-dB compression point (P1dB) by ensuring a large voltage headroom. Furthermore, the designed LNA also achieved a low noise figure (NF), while also saving the silicon area by magnetically coupling the source and folding inductors. When tested experimentally, the proposed LNA showed an S21 of 11.0 dB and an NF of 2.6 dB, while achieving an <i>S</i><sub>11</sub> of -7 dB at the operating frequency of 2.4 GHz. The measured input P1dB and IIP3 were -5.6 dBm and +2.5 dBm, respectively. The power dissipation was 9.6 mW from a 1.2-V supply voltage.

Analysis and Design of a Gain-Enhanced 1–20-GHz LNA With Output-Stage Transformer Feedback

A gain-enhanced technique with output-stage transformer feedback (OSTF) for the low-noise amplifiers is proposed in this brief. The transformer is realized by a pair of magnetically coupled microstrip lines between the drain and source stages, one of which acts as a series-peaking inductor and the other as a source degenerate inductor. By adjusting the length and gap of the magnetically coupled microstrip lines, the tuning of the gain in high frequency is realized. To verify the proposed OSTF gain-enhanced scheme, two LNAs with the same structure are designed, with one having OSTF and the other not. The gainenhanced wideband LNA with OSTF is fabricated in 0.15-GaAs pseudomorphic high-electron mobility transistor process. The total chip area, including input and output testing pads, is 1.24 mm2. The simulated results show excellent performance with a maximum gain improvement of 3-dB at 20 GHz. The measured results show that the gain-enhanced LNA has an average gain of 22.6 dB and a noise figure below 2 dB from 1 to 20 GHz, which are in good agreement with simulated ones.

Nonlinear rotor kinetic energy control strategy of DFIG-based wind turbine participating in grid frequency regulation

Large-scale wind power integration reduces the level of inertia in power systems, significantly deteriorating their frequency stability. To address this issue, a nonlinear rotor kinetic release control strategy is designed for wind power grid-connected systems based on an extended state observer (ESO) and nonlinear feedforward state feedback transformation (NFSFT) theories. First, the affine nonlinear system of a DFIG-based wind turbine participating in grid frequency regulation is established. The system is transformed into a basic equivalent linear system based on the NFSFT theory, and a nonlinear control law is obtained. Second, the ESO is used to observe the generalized disturbance composed of the complex parameter operation required by the nonlinear control law, which circumvents the huge computational burden of the nonlinear control law and the unknown uncertainty of the system. Finally, a limiting link and speed control link are added to prevent excessive release of the kinetic energy of the wind turbine rotor and complete the wind turbine speed recovery. A wind power grid-connected system is built using MATLAB / SIMULINK for simulation verification. The results show that the proposed strategy exhibits a better frequency regulation effect than other strategies.

Efficient Long-Term Dependencies Learning for Passenger Flow Prediction With Selective Feedback Mechanism

With the rapid growth of worldwide urbanization, the increasing demand for public transportation is indispensable. To improve the service quality, predicting the flow of passengers is important for the transport operators. Information on density of passengers can be used as early warnings of overcrowding and to determine if additional fleet is required. However, passenger flow forecasting is a challenging task, as it is affected by many complex factors such as spatial dependencies, temporal dependencies, and external influences. Furthermore, the ability to learn the long-term dependency of the data is also crucial, as the distant past flow information contributes to the flow over time. Most of the existing studies struggle to solve this issue, especially to learn the long-term dependency of the data, as they rely heavily on the raw handcrafted features and require high memory bandwidth to compute. To address these issues, we propose a Selective Feedback Transformer (SFT) capable of learning long-term dependency efficiently, where the selective feedback mechanism only computes the important feedback from the dominant query-key pairs in the memory. Experimental results demonstrate that the proposed model outperforms all the benchmarked methods by 27% - 37% in terms of RMSE and 36% - 50% in terms of MAE. Additionally, when the proposed model is tested with shallowed model (less number of decoding layer), it exhibits a substantial improvement of 14% - 57% in the training time and 15% - 46% in the inference time, with minimal impact on the accuracies.

Analysis and design of a 55–74 GHz ultra‐compact low‐noise amplifier using highly asymmetric transformers

This letter presents a low-noise amplifier with a 3 dB-bandwidth, from 55 to 74 GHz, excellent noise performance and low power consumption based on a three-stage common-source topology. For the first time to the authors' best knowledge, an analytical equation that also considers the gate–drain capacitance is derived for the employed shunt–series transformer feedback input matching network. To enable shunt–series transformer feedback matching without significant gain reduction a highly asymmetric transformer is designed. Furthermore, a compact transformer-implemented T-shaped output matching network is investigated to minimize the required area. To prove these concepts, the circuit has been fabricated in a 22 nm fully depleted silicon-on-insulator technology. Thanks to the transformer-based matching, an ultra-compact active footprint of 0.039 mm2 is achieved. At a power consumption of 8.4 mW from a 0.41 V supply an average noise figure of 4.8 dB and a peak gain of 14.2 dB has been measured. In- and output matching better than −10 dB over the 19 GHz wide 3 dB-bandwidth are demonstrated.

Feedback equivalence and uniform ensemble reachability

This paper considers feedback methods for ensemble reachability of parameter-dependent linear systems (A(θ),B(θ)), where the parameter θ is varying over a compact Jordan arc in the complex plane. Recently, pointwise testable sufficient conditions for uniform ensemble reachability have been developed. Beside the necessity of pointwise reachability these conditions put restrictions on the spectra of the matrices A(θ) and the Hermite indices of the pair (A(θ),B(θ)). In this paper we show that these conditions can be ensured by applying a suitable feedback transformation if the pair (A(θ),B(θ)) is pointwise reachable and its Kronecker indices are independent of the parameter.

Low-Voltage Dual-Band CMOS Voltage-Controlled Oscillator for Ka-Band and V-Band Applications

A low-voltage dual-band CMOS voltage-controlled oscillator (VCO) is fabricated in a 90-nm CMOS process. The performance of the proposed VCO is improved by winding a multifunction inductor with transformer feedback and parasitic capacitance-splitting techniques. The proposed VCO adopts a push–push node to obtain a second-harmonic signal strengthened by using the injection amplifier and the bandpass filter. The measured tuning ranges of the fundamental signal and second-harmonic signal are from 27.5 to 30.04 and 55 to 60.08 GHz, respectively. The measured phase noise of the fundamental signal of 28.26 GHz is −95.62 and −111.5 dBc/Hz at 1- and 10-MHz offsets, respectively. The measured phase noise of the second-harmonic signal of 56.52 GHz is −87.83 and −107.9 dBc/Hz at 1- and 10-MHz offsets, respectively. The core power dissipation is 7.08 mW from a 0.6-V supply. The figure-of-merits (FOMs) and FOMs with tuning range (FOM <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">T</sub> s) at 1- and 10-MHz offsets are −176.1, −172, −175, and −170.9 dBc/Hz, respectively, from the fundamental signal of 28.26 GHz. The FOMs and FOM <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">T</sub> s at 1- and 10-MHz offsets are −174.3, −174.4, −173.2, and −173.3 dBc/Hz, respectively, from the second-harmonic signal of 56.52 GHz.

Self-oscillations that cause the destruction of intermolecular bonds in the water coolant of a nuclear power plant

The digital acoustic model of a nuclear reactor (DAMNR) is presented as an auto-oscillatory system belonging to a special class of nonlinear dissipative systems capable of generating undamped oscillations. It is established that a water-water power reactor with a turbulent flow of a coolant is an open system of high complexity with a large number of elements, the connections between which are not predetermined, but probabilistic. Elements of the coolant circuit with negative dissipation (negative friction) are identified. It is shown that they self-organize chaotic turbulent pulsations and vortices into ordered wave oscillations, the frequency of which is determined by the Thomson (Kelvin) formula. In radio engineering circuits, an electronic self-oscillating generator with transformer feedback has similar properties. The presence of negative resistance in nonlinear dynamical systems leads to self-organization of chaotic turbulent perturbations and generation of self-oscillations in the form of acoustic standing waves (ASW). On the basis of theoretical and experimental data, the reliability of a previously unknown property of a reactor with connected pipelines - the ability to generate several ASW simultaneously-was confirmed. The use of DAMNR in the design and operation of nuclear power plants allows to identify the sources of ASW occurring in the coolant, the conditions for their occurrence and frequency.

Singularities of holonomic and non-holonomic robotic systems: A normal form approach

This paper is intended to make a contribution to methodology of robotics research with a focus on the analysis of robot singularities. It is well known that the presence of singular configurations impairs the robot’s manipulability/mobility, and invalidates a majority of robot control algorithms. For this reason, the understanding of singularities has been a challenging problem of robotics for decades. The objective of this paper consists in fostering the normal form approach as a tool for analysis of singularities of both holonomic and non-holonomic robots. In order to justify the normal form approach, we have invoked a collection of our existing, earlier and newest results. Intuitively, a normal form of an object is an equivalent object of the same kind as the original, of the simplest possible form. Specifically, for the kinematics of serial manipulators normal forms are defined by means of the LR-equivalence of smooth maps. For mobile robots represented as control systems normal forms are obtained by feedback transformations. A rationale for studying singularities by normal forms stems from the fact that both equivalence relations mentioned above preserve singular configurations. In the paper we shall show that normal forms may facilitate detection and description of singular configurations, as well as explain the robot’s behavior at singularities. This will be illustrated by an application of the normal form approach to example earth and space robots.

Normal form approach in the motion planning of space robots: a case study

We examine applicability of normal forms of non-holonomic robotic systems to the problem of motion planning. A case study is analyzed of a planar, free-floating space robot consisting of a mobile base equipped with an on-board manipulator. It is assumed that during the robot’s motion its conserved angular momentum is zero. The motion planning problem is first solved at velocity level, and then torques at the joints are found as a solution of an inverse dynamics problem. A novelty of this paper lies in using the chained normal form of the robot’s dynamics and corresponding feedback transformations for motion planning at the velocity level. Two basic cases are studied, depending on the position of mounting point of the on-board manipulator. Comprehensive computational results are presented, and compared with the results provided by the Endogenous Configuration Space Approach. Advantages and limitations of applying normal forms for robot motion planning are discussed.

Abnormal center of mass feedback responses during balance: A potential biomarker of falls in Parkinson's disease.

Although Parkinson disease (PD) causes profound balance impairments, we know very little about how PD impacts the sensorimotor networks we rely on for automatically maintaining balance control. In young healthy people and animals, muscles are activated in a precise temporal and spatial organization when the center of body mass (CoM) is unexpectedly moved that is largely automatic and determined by feedback of CoM motion. Here, we show that PD alters the sensitivity of the sensorimotor feedback transformation. Importantly, sensorimotor feedback transformations for balance in PD remain temporally precise, but become spatially diffuse by recruiting additional muscle activity in antagonist muscles during balance responses. The abnormal antagonist muscle activity remains precisely time-locked to sensorimotor feedback signals encoding undesirable motion of the body in space. Further, among people with PD, the sensitivity of abnormal antagonist muscle activity to CoM motion varies directly with the number of recent falls. Our work shows that in people with PD, sensorimotor feedback transformations for balance are intact but disinhibited in antagonist muscles, likely contributing to balance deficits and falls.

Geometric Analysis of Differential-Algebraic Equations via Linear Control Theory

We consider linear differential-algebraic equations DAEs and the Kronecker canonical form KCF of the corresponding matrix pencils. We also consider linear control systems and their Morse canonical form MCF. For a linear DAE, a procedure named explicitation is proposed, which attaches to any linear DAE a linear control system defined up to a coordinates change, a feedback transformation and an output injection. Then we compare subspaces associated to a DAE in a geometric way with those associated (also in a geometric way) to a control system, namely, we compare the Wong sequences of DAEs and invariant subspaces of control systems. We prove that the KCF of linear DAEs and the MCF of control systems have a perfect correspondence and that their invariants are related. In this way, we connect the geometric analysis of linear DAEs with the classical geometric linear control theory. Finally, we propose a concept named internal equivalence for DAEs and discuss its relation with internal regularity, i.e., the existence and uniqueness of solutions.

The feedback invariant measures of distance to uncontrollability and unobservability

ABSTRACT The selection of systems of inputs and outputs forms part of the early system design that is important since it preconditions the potential for control design. Existing methodologies for input, output structure selection rely on criteria expressing distance to uncontrollability, unobservability. Although controllability is invariant under state feedback, its corresponding degrees expressing distance to uncontrollability is not. The paper introduces new criteria for distance to uncontrollability (dually for unobservability) which is invariant under feedback transformations. The approach uses the restricted matrix pencils developed for the characterisation of invariant spaces of the geometric theory and then deploys exterior algebra to define the invariant input and output decoupling polynomials. This reduces the overall problem of distance to uncontrollability (unobservability) to two optimisation problems: the distance from the Grassmann variety and distance of a set of polynomials from non-coprimeness. Results on the distance of Sylvester Resultants from singularity provide the new measures.

On the fixed-time stabilization of input delay systems using act-and-wait control

Abstract We address the state feedback stabilization of linear systems with input delay using the so-called act-and-wait control strategy. The latter approach induces an analysis of the closed-loop stability based on a finite-dimensional monodromy operator, and rendering this matrix nilpotent results in fixed-time stability. We show that any controllable planar system can be stabilized in a fixed time, and the constructive proof reveals that always two isolated solutions for the corresponding controller gain co-exist. Next, for the fixed-time stabilization of general linear systems, we present both a novel numerical approach for the computation of the controller gain, and an analytic approach relying on incorporating a predictor and an appropriately defined feedback transformation in the control scheme. Several illustrations complete the presentation.

Аdaptive broadband low-noise RF amplifier

Adaptive broadband low-noise radio frequency amplifiers (ABLNRFA) are widely used in the construction of systems for protecting radio receiving paths from nonlinear damage in a non-stationary electromagnetic environment (EME). One of the promising focus areas on the creation of ABLNRFA is the development of devices in the class of circuits with switched networks. The creation of such devices has certain features, since, along with the need to ensure a low noise figure and digital control of the regulation characteristic, it is required to provide high linearity and a large dynamic range (DR) of the device. This paper presents the results of the logical-heuristic synthesis of ABLNRFA with an adaptively adjustable transducer gain, which changes due to switching of transformer feedback circuits. In order to check the functional and technical characteristics of the synthesized ABLNRFA and optimize its parameters, a model was developed and studied in the ADS environment. The proposed ABLNRFA technical solution provides a discrete (23, 14, 10 and 5 dB) wideband change in the transmission coefficient, while the DR for third-order intermodulation in terms of a 1 MHz band is 83, 92, 98 and 104 dB, respectively. A step change in the transducer gain in the circuit of the lossless feedback circuit developed by ABLNRFA avoids the accumulation of additional noise in the structure and provides a low-noise figure that does not exceed 1 dB. The technical characteristics of ABLNRFA allow one to adaptively increase the overload capacity of the radio receiving path with a proportional expansion of its DR in the conditions of non-stationary EME, and thus increase the efficiency of the level protection system against nonlinear damage to the receiving paths of radio communication, radar and radio navigation.

Analysis of a 28-nm CMOS Fast-Lock Bang-Bang Digital PLL With 220-fs RMS Jitter for Millimeter-Wave Communication

This article analyses and demonstrates a 22.5–27.7-GHz fast-lock low-phase-noise bang-bang digital phase-locked loop (PLL) for millimeter-wave (mm-wave) communication. A discrete-time PLL model, together with theoretical transfer functions, gives insight on the functionality of the automatic bandwidth control, on the effect of the gear-shift algorithm for fast lock and on the different noise contributions. The proposed gear-shift algorithm scales up the PLL bandwidth for faster acquisition and orderly reduces it for jitter performance. The PLL contains a digitally controlled oscillator (DCO) based on transformer feedback with a tunable source-bridged capacitor, which allows for a low phase noise (PN) over a wide tuning range (FoM of −184 dBc/Hz and FoM $_{T}$ of −191 dBc/Hz) and for a fine frequency resolution. The PLL occupies 0.09-mm2 core area and exhibits 220 fs rms jitter while consuming 25 mW, giving FoMRMS of −239 dB. Its frequency acquisition time improves from 780 to 45 $\mu \text{s}$ with the gear-shift algorithm. For 60-GHz communication, with a frequency multiplication factor of 2.5, this PLL covers all six channels’ frequencies of IEEE-802.11ad, allows a transmitter (TX) error vector magnitude (EVM) down to −35.9 dB assuming a TX signal to the noise-plus-distortion ratio (SNDR) of 40 dB, and, thus, is capable of supporting 256 quadrature amplitude modulation (QAM).