Active Cancellation Research Articles

An Accurate Non-contact Photoplethysmography via Active Cancellation of Reflective Interference.

Imaging Photoplethysmography (IPPG) is an emerging and efficient optical method for non-contact measurement of pulse waves using an image sensor. While the contactless way brings convenience, the inevitable distance between the sensor and the subject results in massive specular reflection interference on the skin surface, which leads to a low Signal to Interference plus Noise Ratio (SINR) of IPPG. To ease this challenge, this work proposes a novel modulation illumination approach to measure the accurate arterial pulse wave via surface reflection interference isolation from IPPG. Based on the proposed skin reflection model, a specific modulation illumination is designed to separate the surface reflections and obtain the subcutaneous diffuse reflections containing the pulse wave information. Compared with the results under ambient illumination and constant supplemental illumination, the SINR of the proposed method is improved by 4.56 and 3.74 dB, respectively.

Differential Active Self-Interference Cancellation for Asynchronous In-Band Full-Duplex GFSK

Differential Active Self-Interference Cancellation for Asynchronous In-Band Full-Duplex GFSK

Performance of a Highly Integrated Micro Linear Stirling Cooler with Active Vibration Cancellation

In order to meet the requirements of weight, vibration, and size in the field of infrared imaging, Lihan Cryogenics has developed a lightweight and compact free-piston Stirling cooler. The cooler weighs 265g and includes a built-in electronic controller and active balancer. The system comprises a gas-bearing moving magnet compressor and a low-temperature rod-less displacer, are arranged in-line to have axial symmetry (SymCoolTM). This is also designed to be IDCA (integrated dewar cooler assembly) optional to meet industry-standard. Furthermore, an active vibration controller is developed to reduce vibration, utilizing an active motor on the same axis as the compressor piston to offset vibrations. The refrigeration performance is experimentally tested under different heat dissipation and cold head working temperatures. The test results show that the cooler acquires 0.5W cooling capacity at 77K with 12.6W power consumption, and the power consumption of the active vibration controller is less than 3W.

Active quasi circulator: Comprehensive review and performance comparison

AbstractDesigning circulator as an antenna interface device becomes a daunting task, particularly active‐quasi circulator. This article focuses on demonstrating the basic operation principle, design methods, technical parameters, and performance metrics of active quasi‐circulator. In addition, the study provides an analogy of the circuits and structures proposed by the researchers to enhance certain performance metrics. Active signal cancellation and passive signal cancellation are identified as the major design approaches. Tunable, wideband, and wideband‐tunable are the major types of circulators found in existing literature. Moreover, this article provides a performance comparison of the active‐quasi circulators available in existing literature. Several active quasi‐circulators were able to operate in high frequencies such as 60 GHz with acceptable isolation levels. On the other hand, several designs have over 30 dB isolation, which is a highly desired parameter. At last, the future design challenges associated with active‐quasi circulators have been discussed to provide insight into future research.

Evaluation of Active Occlusion Effect Cancellation in Earphones by Subjective, Real-Ear and Coupler Measurements

Evaluation of Active Occlusion Effect Cancellation in Earphones by Subjective, Real-Ear and Coupler Measurements

An active cancellation method for the common mode current of the three-phase PWM motor drives

An active cancellation method for the common mode current of the three-phase PWM motor drives

Active RIS-Empowered Signal Cancellation Attacks

Active RIS-Empowered Signal Cancellation Attacks

Active cancellation of oblique noise entering a window

Environmental noise propagating through an open window may be cancelled by a sparse array of transducers placed in the window frame. This approach towards global noise cancellation mitigates noise pollution at its source while retaining the light and ventilation received from an open window. Heretofore the array’s performance has been studied with a normally incident noise source; however, oblique noise sources must be considered to fully illustrate the array’s viability as a commercial product. Analytical and finite element models were used to perdict the array’s global noise cancellation capabilities with regards to oblique noise sources, and these results were verified via experimental implementation. Flaws inherent to the current array, including cross bar vibrations and nonoptimal transducer placement, will be discussed along with how they will be circumvented in a future array iteration.

Laser-cavity locking utilizing beam ellipticity: accessing the 10−7 instability scale relative to cavity linewidth

Frequency-stable lasers form the back bone of precision measurements in science and technology. Such lasers typically attain their stability through frequency locking to reference cavities. State-of-the-art locking performances to date had been achieved using frequency modulation based methods, complemented with active drift cancellation systems. We demonstrate an all passive, modulation-free laser-cavity locking technique (squash locking) that utilizes changes in spatial beam ellipticity for error signal generation, and a coherent polarization post-selection for noise resilience. By comparing two identically built proof-of-principle systems, we show a frequency locking instability of 5×10−7 relative to the cavity linewidth at 10 s averaging. The results surpass the demonstrated performances of methods engineered over the last five decades, potentially enabling an advancement in the precision control of lasers, while creating avenues for bridging the performance gaps between industrial grade lasers with scientific ones due to the afforded simplicity and scalability.

ACTIVE TRANSMITTER SIGNAL CANCELLATION IN RECEIVE SIGNAL PATH FOR SDR

Elimination of receiver (RX) band-pass filters is actual task for construction of next generation New Radio Wireless Transceivers and other modern equipment (Multiple Input Multiple Output systems, radar applications, etc.) based on software-defined radio. Unfortunately, some new problems with electromagnetic compatibility arise. Main problem start up with Frequency Division Duplex mode, were part of high power transmitter (TX) signal came to high sensitivity RX input through duplexer with limited isolation. In presence of high TX signal RX mixer could come into non-linear working area and RX sensitivity is decreases. This problem may be solved by cancellation of TX signal from RX path. This article provides a preliminary approach to the problem of active TX signal cancellation in RX signal path with cancellation is at least 25 dB, and relatively small additional power consumption and noise. After critical parameters identifying, based on mathematical expressions, the requirements for cancellation blocks parameters are determined. Simplest implementations of the proposed structure are simulated.

Active INI Cancellation for Mixed-Numerology OFDM System in Uplink Transmission

Active INI Cancellation for Mixed-Numerology OFDM System in Uplink Transmission

Active Cancelation of Acoustic Noise in Waveguides by Standard Control Task Decision Usage

Active Cancelation of Acoustic Noise in Waveguides by Standard Control Task Decision Usage

Comparative Performance Analysis of Inverse Phase Active Vibration Cancellation Using Macro Fiber Composite (MFC) and Vibration Absorption of Silicone Gel for Vibration Reduction.

This study focuses on addressing the issue of unwanted vibrations commonly encountered in various fields by designing an Active Vibration Cancellation (AVC) structure using a flexible piezoelectric composite material macro fiber composite (MFC). A comparative performance analysis was conducted between the AVC and a traditional passive gel that continuously absorbs vibrations. The results showed that AVC was more effective in mitigating vibrations, making it a promising solution for vibration control. The results of this study from extensive vibration-sensing experiments and comparisons revealed that AVC effectively cancels the vibrations and vibration absorption performance of the passive gel. These findings underline the potential of AVC as an efficient method for eliminating and managing undesired vibrations in practical applications. Specifically, AVC demonstrated a high vibration cancellation ratio of approximately 0.96 at frequencies above 10 Hz. In contrast, passive gel exhibited a relatively consistent vibration absorption ratio, approximately 0.70 to 0.75 at all tested frequencies. These quantitative findings emphasize the superior performance of AVC in reducing vibrations to levels below a certain threshold, demonstrating its efficacy for vibration control in real-world scenarios.

Motor Overvoltage Mitigation by Active Cancellation of Reflections Using Parallel SiC Devices With a Coupled Inductor

Motor Overvoltage Mitigation by Active Cancellation of Reflections Using Parallel SiC Devices With a Coupled Inductor

Resonance reduction for linked train cars moving on multiple simply supported bridges

The dynamic interaction of a moving train over a series of railway bridges with equal spans can result in a coupled vibration problem of wave transmission between two periodic structures. Dual resonance occurs when both systems vibrate in phase and the train travels at a resonant speed. The objectives of this paper are to (1) develop an active pitching resonator (APR) to attenuate resonance waves in a train; (2) study the dispersion relation for pitching motion control of periodically linked train cars; (3) investigate the key parameters that affect the dispersion band gaps of wave attenuation in a train; (4) present an active vibration cancellation method to enhance the control performance of the APR; and (5) demonstrate the effectiveness of using the optimal APRs to reduce resonance of a moving train. Through dispersion analysis, the optimum APR can not only shift the target frequency level away from resonance of a moving train, but also create a wide resonance band gap to reduce wave transmission in the train. Finally, the effectiveness of the optimum APR unit in reducing the resonance and attenuating the waves of a train travelling over multiple-span simple beams is demonstrated by dynamic finite element analysis of the train-bridge interaction.

Active Cancellation of the Tonal Component of Sound Using a Discrete Fourier Transform of Variable Length

Active Cancellation of the Tonal Component of Sound Using a Discrete Fourier Transform of Variable Length

Active vibration control for reduction of interior noise caused by R-MDPS of electric power steering in electric vehicle

This paper presents a novel active vibration control (AVC) system for a motor driven power steering (MDPS) system to reduce interior noise in an electric vehicle. The novel control algorithm used for the AVC system is developed based on selection of two reference signals. One is the frequency modulation signal using the rotation speed of motor shaft of MDPS the other one is the band passed signal of acceleration measured on the major path structure identified by the blocked transfer path (BF-TPA). In addition, the piezo stack actuator is used for generation of control force of the AVC system in the frequency over 400 Hz. An MDPS system uses electronic power steering. An MDPS system attached to the rack gear of power steering system is called an R-MDPS. The vibration generated by the R-MDPS is transmitted to the car body through mounts attached onto the car subframe. Panel vibrations of car body are sources of vibroacoustic noise generated inside the car cabin. This vibracoustic noise is a structure-borne noise and causes passenger annoyance. The frequencies of the structure-borne noise measured inside the car cabin are 460 Hz and 920 Hz, which are the rotating frequency of the R-MDPS motor shaft and the second-order harmonic of the rotating speed of the motor shaft. To directly reduce the interior noise inside the car cabin, active noise control (ANC) has been used for the active cancellation of noises with frequencies less than 400 Hz. However, because the frequency of interior noise generated by the operation of the R-MDPS is higher than 400 Hz, AVC was employed in this study for the active cancellation of vibrations transmitted to the car body through the subframe mounts of the car. For application of AVC to the test car, the control force should be known. Therefore, the actuator for generating the control force should be inserted in the mount between the subframe and R-MDPS system. Installing the actuator in the test car is challenging because of the geometry limit of commercial cars. Hence, a test jig composed of an R-MDPS system and the subframe of the test car was developed and set up in the laboratory to study the applicability of AVC to R-MDPS. All investigations of AVC were performed using the test jig in the laboratory. The proposed method was successfully applied to the active cancellation of vibration at a target point on the subframe.

Theory and effectiveness analysis of dual-aircraft formation active cancellation slow synchronous blinking jamming

Theory and effectiveness analysis of dual-aircraft formation active cancellation slow synchronous blinking jamming

Self-Interference Leakage Estimation ‘N’ Cancellation Element: Design of an Active Self-Interference Cancellation Coupler

Monostatic radar systems as well as radars with separated but nearby-placed transmit and receive antennas are beneficial in terms of cost-efficiency and miniaturization, which is necessary for their integration into compact radar systems or mobile devices <xref ref-type="bibr" rid="ref1" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">[1]</xref> , <xref ref-type="bibr" rid="ref2" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">[2]</xref> as well as for radar networks that demand reciprocal transmission channels between the nodes <xref ref-type="bibr" rid="ref3" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">[3]</xref> . However, this lack of separation between the transmit (Tx) and receive (Rx) paths due to miniaturization implies only week isolation between Tx and Rx.

Active Second-Order Pole-Zero Cancellation Control for Speed Servo Systems With Current Sensor Fault Tolerance

This study presents an advanced output-feedback technique for speed regulation tasks in servo systems, which reduces the system model independence and is independent of the current feedback, leading to fault tolerance. Hence, the output position error drives the model-free order reduction filter for speed, and the acceleration feedback (as a replacement for the current loop) is admissible. Furthermore, the proposed control law includes specially structured active damping terms in the feed-forward loop to actively trigger second-order pole-zero cancellation, forming a simple single-loop proportional-integral derivative-type structure with compensation terms. Finally, a 420-W prototype DC servo system experimentally validates the effectiveness of the proposed technique.