Phase Imbalance Research Articles

Ultracompact isolated multilayer broadside-coupled balun with arbitrary isolation bandwidth

Abstract An isolated low-profile multilayer all-ports-matched broadside-coupled balun (BCB) with arbitrary isolation bandwidth is presented. Analytical relations are derived and provided for the isolation circuit (IC) design in terms of electrical and physical parameters. Accordingly, instructions are given on obtaining optimum bandwidth and isolation responses for the IC. Design procedure for the BCB is presented together with a case study for power amplifier application. The BCB is validated theoretically, analytically, and experimentally, and results are in good agreement. The fabricated balun has insertion loss of 0.27 dB, input and output return losses of 19 dB, isolation of 20 dB at fc, and phase and magnitude imbalance better than 2° and 0.2 dB across the Bandwidth (BW), respectively. The realized isolated balun has dimensions of 0.06λg × 0.03λg.

Digital stabilization of an I/Q modulator in the carrier suppressed single-sideband mode for atom interferometry

We present an all-digital method for stabilizing the phase biases in an electro-optic I/Q modulator for carrier-suppressed single-sideband (CS-SSB) modulation. Using programmable logic on the Red Pitaya STEMlab 125-14 platform, we digitally generate and demodulate an auxiliary radio-frequency tone whose beat with the optical carrier probes the I/Q modulator’s phase imbalances. We implement a multiple-input, multiple-output integral feedback controller that accounts for unavoidable cross-couplings in the phase biases to lock the error signals at exactly zero, where optical power fluctuations have no impact on phase stability. We demonstrate >23dB suppression of the optical carrier relative to the desired sideband at +3.4GHz over a period of 15 h and over temperature variations of 20°C.

Inkjet‐printed capacitively loaded Marchand baluns with enhanced fractional bandwidths

AbstractA comprehensive design methodology for the realization of ultra‐wideband and highly miniaturized capacitively loaded Marchand baluns (MBs), suitable for integration into balanced antenna systems is presented. A design technique to maximize the fractional bandwidth (FBW) for a given manufacturing process is demonstrated for the first time. Furthermore, a novel MB integration scheme using broadside‐coupled lines and 3D vertically integrated capacitors in a two‐material inkjet printing process is uniquely proposed. The concept has been experimentally validated within the S and C bands. It exhibits a footprint of 0.128 × 0.098 λg2, centre frequency of 4.4 GHz, and FBW of 121%. Its power loss, phase imbalance and amplitude imbalance were measured between 0.8 and 2.2 dB, 3 ± 2°, and 0.4 ± 0.4 dB, respectively.

An in‐band full‐duplex antenna for 2.4 GHz WLAN using differential‐feed based neutral coupling for isolation enhancement

AbstractThis article introduces a unique design approach for a compact in‐band full‐duplex (IBFD) antenna with good isolation in a wider bandwidth at the 2.4 GHz WLAN. The meander slot baluns are innovatively constructed in the feeding network, one balun on the top substrate layer and the other on the bottom substrate layer of the ground, to realize double differential feeding and polarization diversity. The metallic vias that connect one of the baluns in the feeding network with the co‐radiating patch further reduce the antenna's overall size. The balun's neutral coupling characteristics of differential potentials, which reduce the leakage currents by creating null potential, and differential filtering, which suppresses the leakage currents by non‐coupling fields, generate high isolation in the antenna. The designed balun offers a stable differential feed with a trivial magnitude and phase imbalances of (0.04–0.06) dB and , respectively. The antenna offers a minimum isolation of 78 dB with a wider bandwidth of 130 MHz. The far‐field measurement shows broadside radiation with low cross‐polar levels of less than −32 dB. A prototype is fabricated on FR‐4 substrate layers with an overall size of (0.8 × 0.8 × 0.012) ( is the free space wavelength of the frequency GHz) to validate the proposed design performance. The measured results of the prototype properly correlate with the simulated results.

Bioaugmentation with targeted recombinant functional consortia to improve lignocellulosic biowaste co-anaerobic digestion performance

Hydrolysis rate limitation and acid-methanogenesis phase imbalance are critical challenges in the anaerobic digestion (AD) of lignocellulosic substrates, hindering substrate utilization and methane conversion. Bioaugmentation is widely employed to promote biochemical and metabolic reactions at all stages of AD to enhance methanogenic efficiency. However, synergistic reinforcement for simultaneous enhancement of the hydrolysis and methanogenesis phases requires further elucidation. This study investigated the effect of lignocellulolytic mutualistic methanogenic culture (LMMC) obtained by targeted domestication on the AD system. The results showed that the bioaugmented reactor enhanced the methane production by 21.03%-239.12% and the peak daily methanogenesis by 6.54%-127.85%. Introducing LMMC was directly related to improving methanogenic performance and significantly affected the AD key indicator, which facilitated the timely consumption of volatile fatty acid (VFA) for utilization. Microbial analysis results showed that the enriched hydrolytic acidifying bacteria, anaerobic fungi, and acetoclastic methanogens formed a microbial synergistic reinforcement alliance, which jointly stimulated methane production, alleviated the potential risk of instability, and promoted the stable operation of the AD system. Collectively, the role of synergistic reinforcement in the microbial consortium was highlighted to improve the stability and efficiency of AD process of lignocellulosic biomass.

Two CMOS Wilkinson Power Dividers Using High Slow-Wave and Low-Loss Transmission Lines.

This work presents two Wilkinson power dividers (WPDs) using multi-layer pseudo coplanar waveguide (PCPW) structures. The PCPW-based WPDs were designed, implemented, and verified in a standard 180 nm CMOS process. The proposed PCPW features high slow-wave and low-loss performances compared to other common transmission lines. The two WPDs are based on the same PCPW structure parameters in terms of line width, spacing, and used metal layers. One WPD was realized in a straight PCPW-based layout, and the other WPD was realized in a meandered PCPW-based layout. Both the two WPDs worked up to V-band frequencies, as expected, which also demonstrates that the PCPW guiding structure is less susceptible to the effects of meanderings on the propagation constant and characteristic impedance. The meandered design shows that the measured insertion losses were about 5.1 dB, and its return losses were better than 17.5 dB at 60 GHz. In addition, its isolation, amplitude imbalance, and phase imbalance were 18.5 dB, 0.03 dB, and 0.4°, respectively. The core area was merely 0.2 mm × 0.23 mm, or 1.8 × 10-3λo2.

Implementation of a high-resolution micro-grating accelerometer using a subdivision interpolation technique

This paper proposes a subdivision interpolation technique for an optical accelerometer based on diffraction grating interferometry. The diffraction light intensity curve presents a sine shape with the increase of the acceleration. To address the issues of linearization signal processing across the entire range, a subdivision interpolation circuit is employed, in conjunction with a 90° phase shift and high-precision DC bias-voltage techniques, converting an analog signal with sinusoidal characteristics from the photodetector into standard incremental digital signals that vary linearly over the full range. The novel methodology, to the best of our knowledge, ensures that its performance is least affected by the phase imbalance, offset error, and amplitude mismatch induced by fabrication and alignment errors of the grating, achieving high-resolution digital signal output. The experiment results reveal that the optical accelerometer based on grating interferometry achieved a sensitivity of 85.2 V/g, a resolution of 137.6 µg, as well as a subdivision interpolation factor of 45. This work provides a significant guide for the development of high-resolution MOEMS accelerometers in practical applications.

Phase Noise Compensation Algorithm for Space-Borne Azimuth Multi-Channel SAR.

Azimuth multi-channel synthetic aperture radar (SAR) has always been an important technical means to achieve high-resolution wide-swath (HRWS) SAR imaging. However, in the space-borne azimuth multi-channel SAR system, random phase noise will be produced during the operation of each channel receiver. The phase noise of each channel is superimposed on the SAR echo signal of the corresponding channel, which will cause the phase imbalance between the channels and lead to the generation of false targets. In view of the above problems, this paper proposes a random phase noise compensation method for space-borne azimuth multi-channel SAR. This method performs feature decomposition by calculating the covariance matrix of the echo signal and converts the random phase noise estimation into the optimal solution of the cost function. Considering that the phase noise in the receiver has frequency-dependent and time-varying characteristics, this method calculates the phase noise estimation value corresponding to each range-frequency point in the range direction and obtains the phase noise estimation value by expectation in the azimuth direction. The proposed random phase noise compensation method can suppress false targets well and make the radar present a well-focused SAR image. Finally, the usefulness of the suggested method is verified by simulation experiments.

Two-axis beamsteering using a wideband Butler matrix and series-fed arrays for millimeter wave frequencies fabricated on metallic-nanowire-membrane platform

This work presents a two-axis beamsteering system designed for WLAN millimeter-wave frequencies. The system comprises a wideband Butler matrix and series-fed arrays. The Butler matrix, implemented with microstrip lines, features a wideband crossover with low phase imbalance, enabling four discrete beamsteering directions on the radiation H-plane. The series-fed arrays enable frequency-dependent beamsteering on the E-plane. The entire system was fabricated on a nanoporous alumina substrate using metallic-nanowire-membrane technology. Measurement results indicate an impedance bandwidth of 17.71%, which accommodates typical requirements for 60 GHz WLAN applications. Additionally, beamsteering in the desired directions was achieved. The presented Butler matrix structure stands out as one of the most compact found in the reviewed literature. The produced device successfully balances wideband behavior, compactness, and fabrication simplicity.

Three phase microcontroller based automatic change-over selection switch

The significance of electricity in a developed country cannot be underestimated because power instability problem affects the economy growth, productivity and infrastructure development. The issues of phase failure, losses and phase imbalance earth fault are main causes that lead to unstable and erratic power supply. Most homes and office complexes where single-phase supply is needed are supplied with three phases of power supply to allow change from one phase to another when there is fluctuation or complete outage of power supply on a particular phase. This operation is normally done manually and has caused a setback in terms of time wastage, strenuous operation, susceptibility to fire outbreak, electric shock and high maintenance frequency. When voltage supply on a phase is below 220V or above 415V, this system automatically disconnects the load from the phase and connects to another where the required condition is met. Therefore, this paper presents a Microcontroller Based Automatic Transfer Switching System which is made up of voltage sensing circuit, Hall Effect current sensor, relays, LEDs and LCD of PIC16F877A microcontroller. A system flow chart was developed, programmed with MikroC software and simulated using Proteus electrical software design. A 10KVA single phase generator was used as alternate power source. The load capacity of the design was determined by decoupling Maxwell’s Equations of 8KW and power loss using pointing vector equation as 0.25% of the peak load. The switch is tested to have function optimally within ±5% nominal voltage of 220 - 415V supply and produced approximately 20 seconds elapses during the entire process of power supply changeover. Hence this device is suitable for Industrial and Domestic use where 3-phase power supply is available with a stand-by power source.

Error analysis of OFDM‐IM systems for beyond 5G: The effect of IQI at transceiver

SummaryIt is well known that hardware impairments (HWIs) can worthy reduce the wireless system performance at high carrier frequencies by showing random effects. Most current researches for 5 GB systems assume that transmitters and receivers (transceivers) are perfectly equipped. But wireless transceivers ( ) are affected by HWIs in practice. Considering the previous studies in the literature, it is reported that HWIs have devastating effects on the performance of OFDM and OFDM‐index modulation (IM) systems with fading channels. In this paper, in‐phase and quadrature phase imbalance (IQI), which is the one of most HWIs between transmitter and receiver in wireless communication systems, is examined on OFDM‐IM system over Rayleigh and Nakagami‐ fading channels. Two well‐known detectors, the maximum likelihood (ML) detector and the log‐likelihood ratio (LLR) detector are used under the effect of the IQI at . Error performance analyzes over fading channels of the IQI effect on OFDM‐IM system are realized first theoretically and then by computer simulations. Results obtained for the presence of IQI at show that a performance evaluation based only on the presence of IQI in the receiver would be optimistic and misleading in terms of the performance of real‐life OFDM‐IM systems.

Torque Ripple Suppression in the 6/4 Variable Flux Reluctance Machine with Open Winding Configuration by Using Harmonic Injection

High torque ripple can be observed with a 6/4 variable flux reluctance machine (VFRM). In order to minimize the torque ripple in VFRMs, this paper presents a harmonic injection method for 6/4 VFRMs with an open-winding configuration. By analyzing the impact of harmonics on VFRMs, the method involves detecting the third harmonic using a first-order low-pass filter (FLPF). Subsequently, the extracted harmonics are controlled and shifted to counteract the voltage harmonics in both inverters without inducing phase imbalance or overvoltage. With the proposed method, the torque ripple can be significantly reduced by about 50% under load conditions. The effectiveness of the harmonic injection method is validated through a prototype VFRM.

Long term follow-up of heart rate variability in healthcare workers with mild COVID-19.

Prior investigations into post-COVID dysautonomia often lacked control groups or compared affected individuals solely to healthy volunteers. In addition, no data on the follow-up of patients with SARS-CoV-2-related autonomic imbalance are available. In this study, we conducted a comprehensive clinical and functional follow-up on healthcare workers (HCWs) with former mild COVID-19 (group 1, n = 67), to delineate the trajectory of post-acute autonomic imbalance, we previously detected in a case-control study. Additionally, we assessed HCWs for which a test before SARS-CoV-2 infection was available (group 2, n = 29), who later contracted SARS-CoV-2, aiming to validate findings from our prior case-control investigation. We evaluated autonomic nervous system heart modulation by means of time and frequency domain heart rate variability analysis (HRV) in HCWs during health surveillance visits. Short-term electrocardiogram (ECG) recordings, were obtained at about 6, 13 months and both at 6 and 13 months from the negative SARS-CoV-2 naso-pharyngeal swab (NPS) for group 1 and at about 1-month from the negative NPS for group 2. HCWs who used drugs, had comorbidities that affected HRV, or were hospitalized with severe COVID-19 were excluded. Group 1 was split into three subgroups clinically and functionally followed at, about 6 months (subgroup-A, n = 17), 13 months (subgroup-B, n = 37) and both at 6 and 13 months (subgroup-C, n = 13) from the negative SARS-CoV-2 NPS. In subgroup-A, at 6-month follow-up compared with baseline, the spectral components in the frequency domain HRV parameters, showed an increase in normalized high frequency power (nHF) (t = 2.99, p = 0.009), a decrease in the normalized low frequency power (nLF) (t = 2.98, p = 0.009) and in the LF/HF ratio (t = 3.13, p = 0.006). In subgroup B, the comparison of the spectral components in the frequency domain HRV parameters, at 13-month follow-up compared with baseline, showed an increase in nHF (t = 2.54, p = 0.02); a decrease in nLF (t = 2.62, p = 0.01) and in the LF/HF ratio (t = 4.00, p = 0.0003). In subgroup-C, at both 6 and 13-month follow-ups, the spectral components in the frequency domain HRV parameters were higher than baseline in nHF (t = 2.64, p = 0.02 and (t = 2.13, p = 0.05, respectively); lower in nLF (t = 2.64, p = 0.02 and (t = 2.13, p = 0.05, respectively), and in LF/HF (t = 1.92, p = 0.08 and (t = 2.43, p = 0.03, respectively). A significant proportion of HCWs reported persistent COVID-19 symptoms at both the 6 and 13-month follow-ups, seemingly unrelated to cardiac autonomic balance. In group 2 HCWs, at 1-month follow-up compared with baseline, the spectral components in the frequency domain HRV parameters, showed a decrease in nHF (t = 2.19, p = 0.04); an increase in nLF (t = 2.15, p = 0.04) and in LF/HF (t = 3.49, p = 0.002). These results are consistent with epidemiological data suggesting a higher risk of acute cardiovascular complications during the first 30 days after COVID-19. The SARS-CoV-2 associated autonomic imbalance in the post-acute phase after recovery of mild COVID-19 resolved 6 months after the first negative SARS-CoV-2 NPS. However, a significant proportion of HCWs reported long-term COVID-19 symptoms, which dot not seems to be related to cardiac autonomic balance. Future research should certainly further test whether autonomic imbalance has a role in the mechanisms of long-COVID syndrome.

Research on Step-Down Aviation Three-Phase Power Factor Correction based on Machine Learning and Optimization Algorithm

Objectives: The study looks at power quality issues, such as phase imbalance, voltage sags, and power factor issues, in aircraft systems. It highlights how immediate power factor correction steps are required to avoid equipment longevity problems and boost system efficiency, which will ultimately improve the performance of the entire aviation system. Methodology: Using a variety of data sources, real-time data gathering, and machine learning approaches, this study focuses on data collecting and real-time monitoring in aviation systems. Predictive modeling, testing methods for data preparation and analysis, and optimization algorithms for capacitor bank size and placement are all included. Considerations for privacy and security are covered. Result: Salp Swarm Optimization and the Dragonfly Algorithm are used in the study to assess the ideal capacitor sizes and positions, which results in better voltage profiles and lower active power losses. Aviation systems benefit from improved power factor correction through the application of integrated machine learning and optimization, which promotes sustainability and energy efficiency. Conclusion: The study demonstrated the significance of power factor correction in aviation by successfully addressing power quality issues in aircraft electrical systems through the use of optimization algorithms for capacitor sizing and location.

Millimeter‐wave end‐fire dual‐polarized frequency scanning antenna using LTCC technology

AbstractThis letter proposes a millimeter‐wave dual‐polarized (DP) end‐fire frequency scanning antenna utilizing low temperature co‐fired ceramic (LTCC) technology. The antenna features DP radiating elements, each comprising a quasi‐Yagi antenna for horizontal polarization (H‐pol) and a pyramidal horn antenna for vertical polarization (V‐pol). These elements are excited via a mode‐composited transmission line (MCTL), integrating substrate integrated coaxial line (TEM mode) with substrate integrated waveguide (TE10 mode). To mitigate phase imbalances between polarizations during beam scanning, a delay line is embedded in each quasi‐Yagi element, ensuring consistent scanning ranges for the two polarizations. Furthermore, the implementation of amplitude weighting in the feeding networks contributes to the enhancement of antenna efficiency. A 1 × 8‐element prototype was fabricated and its performance is assessed. The results show closely matched beam scanning ranges for the two polarizations (±28° for H‐pol and −30° to +34° for V‐pol) across the 26–29 GHz frequency band, with a measured maximum peak gain exceeding 9.2 dBi for both polarizations. The proposed design emerges as a promising candidate for compact mmW frequency scanning front‐end antenna systems.

Analysis of pole pair number impact on single-sided linear induction machine performances

This paper presents a parametric study of linear induction motor for design purpose. The chosen mathematical model uses a 2D formulation with magnetic vector potential A. The implementation of the model is carried out with the finite element method on the free platform Gmsh-GetDP. Circuit model is coupled to FE model so that constant voltage supply mode can be considered. This work aims to highlight the effect of the pole pair number on the characteristics and the performances of the linear induction machine through two numerical models associated to an analytical one. Furthermore, the study shows the effect of the pole pair number on the phase imbalance and the spatial harmonic spectrum of the machine. Reducing this imbalance and higher order harmonics presence will increase machine performances.

Analysis and Simulation of Current Balancer Circuit for Phase-Gain Correction of Unbalanced Differential Signals

The phase and gain imbalance of a balun output can be adjusted by a differential current balancer (DCB) circuit. The performance of DCB circuit, for correcting the phase (gain) imbalance, is analyzed for a wide range of input signal level, and the accuracy is verified with circuit simulation. To illustrate the phase-error/gain-error (PE/GE) correction, a 30–40[Formula: see text]GHz DCB circuit is designed and simulated in a 180-nm CMOS process. The DCB is examined for input PE, [Formula: see text], of [Formula: see text] and input GE, GA, of [Formula: see text][Formula: see text]dB. Analysis and simulation illustrate an output phase error [Formula: see text] of [Formula: see text] and output gain error [Formula: see text] of [Formula: see text][Formula: see text]dB, over frequency range of 20–50[Formula: see text]GHz. The results of DCB circuit for PE (GE) compensation are compared to that of phase-correction technique (PCT) circuit, illustrating the superior phase (gain) imbalance correction of the DCB circuit with lower NF and DC power consumption.

Testing and Analysis of Harmonics at utility Substation

This paper is about auditing electrical quality in substations. A Fluke 1748 Energy Analyze is used for power quality audits. The quality audit will be performed according to IEEE Standard 519 2022. The specific purpose of power quality is the cleanliness of the power supply, including voltage fluctuations and waveform distortion. Harmonics occurs whenever non-sinusoidal currents and/or voltages are generated in a power system. This is commonly referred to as harmonic distortion. The main conditions that cause harmonic problems in power systems are non-linear loading, phase imbalance, high input voltage or current, and resonance. Electrical energy is key to industry, commerce and development, so maintaining the quality of electricity flow is important. Having power quality indicators is very important when identifying hazards and possible defects in electrical installations. Keywords: IEEE 519 2022, Harmonics, Power Quality

Influence of quadrature transformation imbalance on the noise immunity of signal reception with amplitude-phase shift keying

Objectives. At the present time, amplitude-phase shift keyed (APSK) signals are actively used in satellite communication systems. In particular, they are applied in systems which operate in a limited radio frequency spectrum with increased data transmission quality requirements. Such systems use multi-channel type receivers with maximum likelihood decision on the received symbol (correlation receiver) or quadrature type receivers. The noise immunity of these receivers is directly dependent on the quality of the formation of reference oscillations. These oscillations are reference signals for correlation receivers and in-phase and quadrature components for quadrature receivers. The aim of the work is to analyze the influence of the amplitude and phase parameter spread of the in-phase and quadrature channels on the noise immunity of receiving APSK signals with a circular shape of the signal constellation.Methods. Methods of statistical radio engineering, theory of optimal signal reception, and computer simulation are used.Results. The study established the characteristics of noise immunity of the APSK signal reception depending on the spread of parameters of the quadrature converter. The theoretical calculations were confirmed by the results of modeling the transmission of APSK signals in a Gaussian communication channel. A comparison with systems using quadrature amplitude modulation (QAM) was carried out, in order to assess system stability in the presence of spread parameters among other similar systems.Conclusions. The studies enabled us to conclude that an imbalance of the quadrature reference oscillations can lead to a significant decrease in the noise immunity of radio systems using APSK signals. The minimum energy loss due to imbalance of quadrature reference oscillations is achieved when the imbalance value is less than 10% in amplitude and 2°–3° in phase. The amplitude imbalance of quadrature reference oscillations when receiving QAM signals is more pronounced than in the case of APSK signals. The phase imbalance affects approximately the same.

A Compact Broadband Power Combiner for High-Power, Continuous-Wave Applications.

A compact broadband combiner with a high power capacity and a low insertion loss, which is especially useful for solid-state power sources where multi-way power synthesis is needed, was designed and experimentally investigated. The combiner could combine the microwave signals of sixteen terminals into a single one and was based on a radial-line waveguide whose circumferential symmetry benefited the amplitude and phase consistency of the combiner. Simulation and experimental results showed that the prototype device, designed for S-band applications, exhibited a reflection coefficient S1,1 < -20 dB in the range of 2.06-2.93 GHz, which corresponds to a relative bandwidth of approximately 34.6%. At 2.45 GHz, the phase imbalance was ±4.5° and the 16-way transmission coefficient was concentrated around -12.0~-12.3 dB. The insertion loss of the device at ambient and elevated temperatures was simulated and experimentally verified, which is of importance for the design of similar high-power microwave combiners. High-power tests proved that even without enforced wind or liquid cooling, the device can handle continuous power (CW) of at least 3.9 kW, which can be much enhanced by taking regular cooling measures. The combined features of the designed combiner suggest promising applications for power synthesis in high-power, solid-state RF sources.