Group Delay Research Articles

Enhancement of quantum entanglement between twin beams via a four-wave mixing process with double feedback

Abstract Two port feedback has been theoretically studied and proved to be effective in enhancing the degree of entanglement of the output beams for an optical four-wave mixing process, but the loss effects and phase delays need to be further concerned. Here, we use a model that is closer to practical implementation. By reasonably tuning the coefficients, we find that higher degree of entanglement and higher power of the output beams can be obtained, and the requirement for phase locking accuracy could be looser, which means this model is more promising for practical applications in quantum computation and quantum communication.

Chirped Integrated Bragg Grating Design

We analyze the two classic methods for chirped Integrated Bragg Gratings (IBGs) in Silicon-on-Insulator technology using the transfer matrix method based on the effective refractive index (neff) technique, which translates the geometry of an IBG into a matrix of neff depending on the wavelength. We also implement a procedure that allows engineering of the chirped IBG parameters, given a required bandwidth (BW) and group delay (GD). Finally, a complementary method for designing chirped IBG is proposed, showing a significant improvement in the bandwidth of the device or a moderation in the variation of the geometrical parameters of the grating.

Non-uniformity of fluctuation characteristics inside an edge magnetic island in Heliotron J

Non-uniform fluctuation characteristics are observed within an edge magnetic island in Heliotron J. The island possesses a long connection length comparable to the confined region. These fluctuations are measured using a Langmuir probe. The island’s presence is confirmed through the plasma response, observed in the modulation amplitude of electron temperature and its phase delay relative to the heat source in a heat modulation experiment. Within the island, the electron density is notably high, accompanied by distinct profiles of electron temperature and electric field, likely attributable to the magnetic island. Contrary to expectations, density fluctuations within the edge magnetic island are not locally minimized, despite the reduced gradient of the profile within the island. Statistical analysis shows a suppression of intermittent transport inside the island, while intermittent fluctuations increase towards the exterior. A further analysis to segregate turbulence-driving and spreading factors reveals that both turbulence-driven and spreading contributions are comparably significant inside the island. Additionally, the non-uniform turbulence results in a spatially structured fluctuation-driven particle flux. Overall, the experimental findings indicate that fluctuation characteristics exhibit notable non-uniformity both inside and near the island. This non-uniformity potentially complicates heat transport and may lead to three-dimensional, asymmetric transport within and at the periphery of the islands.

Phase delays between mouse globus pallidus neurons entrained by common oscillatory drive arise from their intrinsic properties, not their coupling.

A hallmark of Parkinson's disease is the appearance of correlated oscillatory discharge throughout the cortico-basal ganglia (BG) circuits. In the primate globus pallidus (GP), where the discharge of GP neurons is normally uncorrelated, pairs of GP neurons exhibit oscillatory spike correlations with a broad distribution of pairwise phase delays in experimental parkinsonism. The transition to oscillatory correlations is thought to indicate the collapse of the normally segregated information channels traversing the BG. The large phase delays are thought to reflect pathological changes in synaptic connectivity in the BG. Here we study the structure and phase delays of spike correlations measured from neurons in the mouse external GP (GPe) subjected to identical 1-100 Hz sinusoidal drive but recorded in separate experiments. First, we find that spectral modes of a GPe neuron's empirical instantaneous phase response curve (iPRC), elucidate at what phases of the oscillatory drive the GPe neuron locks when it is entrained, and the distribution of phases at which it spikes when it is not. Then, we show that in this case the pairwise spike cross-correlation equals the cross-correlation function of these spike phase distributions. Finally, we show that the distribution of GPe phase delays arises from the diversity of iPRCs, and is broadened when the neurons become entrained. Modeling GPe networks with realistic intranuclear connectivity demonstrates that the connectivity decorrelates GPe neurons without affecting phase delays. Thus, common oscillatory input gives rise to GPe correlations whose structure and pairwise phase delays reflect their intrinsic properties captured by their iPRCs.Significance Statement The external globus pallidus (GPe) is a hub in the basal ganglia, whose neurons impose a barrage of inhibitory synaptic currents on neurons of the subthalamic nucleus, substantia nigra and internal globus pallidus. GPe neurons normally fire independently, but in experimental parkinsonism, they become correlated in the frequency range associated with the pathological rhythms seen in human Parkinson's disease, raising the possibility that they may be generators of the pathological oscillation. We drove individual pallidal neurons with an oscillatory input over a wide range of frequencies. Cross-correlations of these neurons reproduced many of the features seen in parkinsonism, suggesting that their correlated oscillations might derive from a shared input rather than internal interconnections.

A Mach–Zehnder Fabry–Perot Hybrid Fibre-Optic Interferometer for a Large Measurement Range Based on the Kalman Filter

To solve the short working distance and small measurement range of an all-fibre interferometer, we proposed a Mach–Zehnder Fabry–Perot hybrid fibre-optic interferometry system based on sinusoidal phase modulation. In this paper, a low-finesse fibre interferometer with a larger linear operating range for displacement measurement is realised using a self-collimating probe and incorporating a Kalman filter-based phase demodulation algorithm. Through experimental comparisons, it is demonstrated that the interferometer proposed in this paper can effectively reduce the phase delay, compensate for the depth of modulation drift, and correct the error due to parasitic interference introduced by the optical path structure through the algorithm. A linear large measurement working range of 20 cm is realised.

A Novel FSS Loaded Circular Slot Monopole Antenna for Microwave Breast Imaging Application

Breast cancer continues to be a major contributor to women's global mortality rates, emphasizing the need to explore alternative and supplementary early-stage detection techniques. This study delves into a circular slot monopole ultra-wideband (UWB) antenna equipped with a frequency-selective surface (CSMA-FSS) for early detection microwave imaging applications. To expand the impedance bandwidth of the traditional circular monopole antenna, a circular slit is introduced on a monopole structure. Additionally, a 10 × 10 unit cell FSS structure is integrated into the antenna as a far-field reflecting plane to enhance gain characteristics. The antenna, crafted with dimensions of 50 × 50 × 1.6 mm³ and a 1.6 mm thick FR4 substrate, operates across the ultra-wideband frequency spectrum, spanning from 3.1 GHz to 12 GHz, while consistently maintaining a reflection coefficient (S 11) value of – 10 dB or lower. Notably, the antenna showcases a gain of over 5 dBi across the entire 3.1 GHz to 12 GHz frequency range. The suggested antenna is ideal for microwave imaging applications due to its broad impedance bandwidth, impressive gain, and excellent directivity. Furthermore, it maintains a relatively uniform group delay, with a deviation of ±0.5 ns throughout the UWB band. In the time domain characteristics, the antenna exhibits excellent pulse handling capabilities and strong signal correlation, featuring an S 21 value of less than – 25 dB. The characteristics, observed in both the time and frequency domains, suggest that the proposed antenna holds significant potential for substantially enhancing breast cancer imaging system.

Polarization-engineered photon statistics and its tomography via optomagnonic interaction.

Cavity optomagnonics has received considerable research interest in recent years, due to the coherent magnetic Brillioun light scattering in the ferromagnetic material. Here, we theoretically propose and numerically verify a feasible scheme for the full polarization tomography on photon statistics in an optomagnonic whispering-gallery-mode microresonator system in the weak-coupling regime. By performing the polarization pre- and post-selections to manipulate the polarization states of the input and output photons, we find that the rich sub- and super-Poissonian photon statistics can be selectively generated, thanks to quantum interferences. In the parameter space of phase delay, the evolution from photon bunching to antibunching indicates the change from phase to amplitude squeezing. Our obtained result has potential applications in tunable quantum polarized light sources based on the cavity optomagnonic platform in micro-nano scale. It also offers a deeper understanding for full quantum cavity optomagnonics.

Quasi-bound states in the continuum for electromagnetic induced transparency and strong excitonic coupling

Advancing on previous reports, we utilize quasi-bound states in the continuum (q-BICs) supported by a metasurface of TiO2 meta-atoms with broken inversion symmetry on an SiO2 substrate, for two possible applications. Firstly, we demonstrate that by tuning the metasurface's asymmetric parameter, a spectral overlap between a broad q-BIC and a narrow magnetic dipole resonance is achieved, yielding an electromagnetic induced transparency analogue with a 50 μs group delay. Secondly, we have found that, due to the strong coupling between the q-BIC and WS2 exciton at room temperature and normal incidence, by integrating a single layer of WS2 to the metasurface, a 37.9 meV Rabi splitting in the absorptance spectrum with 50% absorption efficiency is obtained. These findings promise feasible two-port devices for visible range slow-light characteristics or nanoscale excitonic coupling.

Design and fabrication of a microstrip triplexer with wide flat channels for multi-band 5G applications.

In this paper, a new microstrip triplexer is designed to work at 2.5 GHz, 4.4 GHz and 6 GHz for mid-band 5G applications. All channels are flat with three low group delays (GDs) of 0.84 ns, 0.75 ns and 0.49 ns, respectively. Compared to the previously reported works, the proposed triplexer has the minimum group delay. The designed triplexer has 18.2%, 13.7%, 23.6% fractional bandwidths (FBW%) at 2.5 GHz, 4.4 GHz and 6 GHz, respectively. The obtained insertion losses (ILs) are low at all channels. These features are obtained without a noticeable increase in the overall size. A novel and simple resonator is used to design the proposed triplexer, which includes two pairs of coupled lines combined with a shunt stub. A perfect mathematical analysis is performed to find the resonator behavior and the layout optimization. The type of shunt stub is determined mathematically. Also, the smallness or largeness of some important physical dimensions is determined using the proposed mathematical analysis. Finally, the designed triplexer is fabricated and measured, where the measurement results verify the simulations.

All-optical subcycle microscopy on atomic length scales.

Bringing optical microscopy to the shortest possible length and time scales has been a long-soughtgoal, connecting nanoscopic elementary dynamics with the macroscopic functionalities of condensed matter. Super-resolution microscopy has circumvented the far-field diffraction limit by harnessing optical nonlinearities1. By exploiting linear interaction with tip-confined evanescent light fields2, near-field microscopy3,4 has reached even higher resolution, prompting a vibrant research field by exploring the nanocosm in motion5-19. Yet the finite radius of the nanometre-sized tip apex has prevented access to atomic resolution20. Here we leverage extreme atomic nonlinearities within tip-confined evanescent fields to push all-optical microscopy to picometric spatial and femtosecond temporal resolution. On these scales, we discover an unprecedented and efficient non-classical near-field response, in phase with the vector potential of light and strictly confined to atomic dimensions. This ultrafast signal is characterized by an optical phase delay of approximately π/2 and facilitates direct monitoring of tunnelling dynamics. We showcase the power of our optical concept by imaging nanometre-sized defects hidden to atomic force microscopy and by subcycle sampling of current transients on a semiconducting van der Waals material. Our results facilitate access to quantum light-matter interaction and electronic dynamics at ultimately short spatio-temporal scales in both conductive and insulating quantum materials.

Real-Time Estimation of BDS-3 Satellite Clock Offset with Ambiguity Resolution Using B1C/B2a Signals

The third generation of the BeiDou navigation satellite system (BDS-3) can transmit five-frequency signals. The real-time satellite clock offset of BDS-3 is typically generated utilizing the B1I/B3I combination with the ambiguity-float solutions. By conducting the ambiguity resolution (AR), the reliability of the satellite clock offset can be improved. However, the performance of BDS-3 ambiguity-fixed real-time satellite clock offset with B1C/B2a signals remains unknown and unrevealed. In this contribution, the performance of the BDS-3 ambiguity-fixed satellite clock offset with the new B1C/B2a signals is investigated. One week of observation data from 85 stations was used to perform ambiguity-fixed satellite clock offset estimation. For B1I/B3I and B1C/B2a signals, the wide-lane (WL) uncalibrated phase delay (UPD) on the satellite end is fairly stable for one day, while the narrow-lane (NL) UPD standard deviation (STD) amounts to 0.122 and 0.081 cycles, respectively. The mean ambiguity fixing rate is 80.7% and 78.0% for these two signal combinations, and the time to first fix (TTFF) for the B1C/B2a signals is remarkably shorter than that of the B1I/B3I signals. The STDs of the ambiguity-float and -fixed satellite clock offsets are 0.033 and 0.026 ns, respectively, for the B1I/B3I combination, and it is reduced to 0.024 and 0.023 ns for B1C/B2a signals, respectively. Using the estimated UPD and clock offset products, the positioning performance of the kinematic Precise Point Positioning (PPP)-AR results amounts to 1.56, 1.23, and 4.46 cm in the east, north, and up directions for B1I/B3I signals, respectively. It is improved to 1.36, 1.16, and 4.25 cm using the products estimated with the B1C/B2a signals, with improvements of 12.8%, 5.7%, and 4.7% in three directions, respectively. The experiments showed that the performances of the ambiguity-fixed satellite clock offsets and the PPP-AR results using B1C/B2a signals are better than those of B1I/B3I.

Circumferential slots based decoupled wideband MIMO antenna for 5G and sub-6 GHz applications

This paper investigates a small size 2 × 2 wideband multiple input multiple output (MIMO) antenna covering frequency band of 2.61 to 5.52 GHz. The antenna structure consists of elliptical ring patch with multiple circumferential slots. The edge-to-edge separation between the patches are kept 3.6 mm with volumetric dimensions of 30 × 46 × 1.6 mm3. The narrow slits are etched in the tapered ground plane to obtain the wideband characteristics. The electromagnetic coupling is improved more than 16 dB by employing the neutralization technique. The measured average gain and radiation efficiency of the proposed antenna are above 2.61dBi and 83.54%, respectively across the operating band. In addition to that, the important MIMO diversity parameters are investigated. The group delay and signal analysis in different orientations are also studied to ensure the quality performance of the antenna. The proposed MIMO antenna is simulated using CST microwave studio and further validated with the measurements. In addition to that, the parallel and orthogonal configuration of 4 × 4 MIMO antennas are analyzed by extending the proposed 2 × 2 MIMO design. The 4-port MIMO antennas exhibit the operating frequency bands varying from 2.80 to 5.58 GHz and 3.4 to 5.52 GHz, respectively for parallel and orthogonal MIMO configurations. The diversity parameters of 4-port MIMO antennas are calculated and compared with the measured results to verify its practical applications. Finaly, the SAR analysis of the antenna is presented at 3.08 and 5.20 GHz for 1/10 g tissues and are found 0.111/0.106 and 0.079/0.063 W K−1g−1, respectively. The proposed MIMO antenna designs are suitable for modern high-speed communication for 5G and sub-6 GHz frequency bands.

Determine Multilayers Coating Dispersive Properties Using Statistical Parameters

Abstract Many studies about the multilayer coating have indicated the effects of reflection phase, reflection group delay (GD), and reflection group delay dispersion (GDD) characteristics. Some overlook the importance of studying complex statistical coefficients and their role in comparing the results of optical designs and realize how important information is in analyzing data. In statistics, one can learn various techniques for working with data. This paper goes into a detailed study of multilayer stacks’ dispersive properties for two mirror designs depending on MATLAB programs based on statistical parameters to evaluate the reflectance for the ZnS/MgF$${}_{2}$$ mirror. Two samples with a quarter wavelength optical thickness were prepared, specially designed for 632.8 nm He-Ne laser mirrors. For the designed mirror, the value of the reflectivity of the thirteen-layer ZnS/MgF$${}_{2}$$ mirror is 99.34$$\%$$, while for the seven-layer ZnS/MgF$${}_{2}$$ mirror is 96.57$$\%$$. This study presents greater detail on statistics and realized data topics when designing multilayer coating, including mean, median, mode, and standard deviation (STD). The reliability and accuracy of the data can be verified by calculating the standard deviation.

Abstract RF01-08: A randomized, open-label phase III trial Evaluating Low-Dose Vs standard-dose Olanzapine with triple Antiemetic therapy for Prevention of highly emetogenic chemotherapy- induced Nausea and vomiting in solid tumors (OLAnzaPiNE)

Abstract Background Chemotherapy induced nausea and vomiting (CINV) is a major adverse event for cancer patients. Olanzapine (OLZ) in standard 10 mg dose along with triple antiemetics (TAE), has shown effectiveness in treating CINV with highly emetogenic chemotherapy (HEC), however, significant day time somnolence (DTS) precludes its widespread use. Steroids related side effects are another major concern. Hence, a lower dose of OLZ, with single dose (SD) steroid use is worth exploring in a randomized fashion. Methods Solid tumors planned for anthracycline-cyclophosphamide & high-dose cisplatin chemotherapy was randomized (1:1) to receive either 10mg OLZ (standard arm) or 2.5mg (experimental arm) till day 4 with TAE regimen [5-hydroxytryptamine type 3 (5-HT3) receptor antagonists, dexamethasone (SD, without delayed doses), and neurokinin-1 (NK1) receptor antagonists] in both arms. Primary objective was to evaluate Complete control rate (CCR) defined as proportion of subjects with no emetic episodes (EE), no use of rescue medications (RM), no or mild nausea assessed in overall phase (OP) =0-120 hours(h) in both groups. Secondary objectives were to compare two groups for the CCR in acute(AP) and delayed phase(DP);Complete response rate (CRR)=no EE and no use of RM in AP(0- 24h), DP(25-120h) and OP; Total control rate(TCR)= no EE, no use of RM, and no nausea) in AP, DP, OP; Time to treatment failure(TTF), defined as mean duration from chemotherapy initiation to first episode of nausea, EE, use of RM; Incidence of significant daytime somnolence(DTS).Tertiary objectives were effect on appetite loss. Subjects maintained a daily record of nausea, EE, RM use with the severity graded on a four-category scale. Statistical analysis CCR, CRR, TCR are given in counts and proportions. Occurrence of nausea, EE, DTS and their grades were compared using Chi-square test. Results A total of 275 subjects were enrolled, among them 267 were analyzable, inclusive of 132 subjects in 2.5mg and135 in 10mg arms with well-balanced baseline characteristics (Table 1) Proportion of patients with CCR in OP (Primary end point) in 2.5mg vs. 10mg arms were, 44.7 % vs. 43.7 % (P = 0.87) respectively. CCR in 2.5mg vs. 10mg arms in AP, DP were 50% vs. 48.9%(p=0.856) and 50.8% vs. 58.5% (P=0.203) respectively. CRR in 2.5mg vs. 10mg in AP, DP and OP were 56.1% vs. 57 % (P=0.872), 55.3% vs. 63% (P = 0.203), and 50.8 % vs. 51.1% (P=0.954), respectively. TCR in2.5mg vs. 10mg in AP, DP, and OP were25% vs. 23 % (P=0.697), 20.5% vs. 22% (P = 0.725), and 13.6 % vs. 15.6% (P=0.657), respectively. Subjects receiving 2.5 mg as compared with those receiving 10 mg, had statistically significant decreased DTS on overall grades 65.2%vs 89.6% vs. (p < 0.001); severe grade DTS was more on day1 i.e., 4.5%vs. 40% (p < 0.001) and although successively reduced from day 2-5 in both the arms, however, 2.5 mg fared better on all the days (table 1). No statistically significant effect of reduced appetite noted in 2.5mg vs. 10mg i.e., 17.4% vs. 24.4 %(p=0.208) Conclusion Low dose olanzapine (2.5mg) is non inferior to 10mg olanzapine in controlling CINV without requirement of delayed steroids, and is superior with respect to DTS (all days, all grades, severe grades) in subjects receiving HEC. This merits wide recognition as a new steroid sparing antiemetic regimen of choice with HEC. Demographic data, Clinical characteristics and Outcomes Citation Format: Jyoti Bajpai, Venkatesh Kapu, Sushmita Rath, Sravan Kumar, Anbarasan Sekar, Srikanth Anne, Akash Pawar, Sujay Srinivas, Prabhat Bhargava, Seema Gulia, Rajiv Sarin, Rajendra Badwe, Sudeep Gupta. A randomized, open-label phase III trial Evaluating Low-Dose Vs standard-dose Olanzapine with triple Antiemetic therapy for Prevention of highly emetogenic chemotherapy- induced Nausea and vomiting in solid tumors (OLAnzaPiNE) [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr RF01-08.

Analysis of language and influencing factors of children with speech disorder in Beijing

Objective: To investigate the features and influencing factors of language in children with various types of speech disorders. Methods: A case-control study was carried out, 262 children with speech disorder had been diagnosed at the language-speech clinic of the Center of Children's Healthcare, Children's Hospital, Capital Institute of Pediatrics from January 2021 to November 2023, the children with speech sound disorder as the speech sound disorder group, the children with developmental stuttering as the stuttering group. There were 100 typically-developed children who underwent physical checkups at the Center of Healthcare during the same period as the healthy group. All children experienced a standardized evaluation of language with diagnostic receptive and expressive assessment of mandarin-comprehensive(DREAM-C) and questionnaire, One-way ANOVA and LSD test were conducted to compare the differences in overall language, receptive language, expressive language, semantics, and syntax scores among 3 groups of children. According to the results of DREAM-C, the children with speech disorder were divided into language normal group and language delay group. Chi-square test and multivariate Logistic regression were implemented to analyze the association between the linguistic development of children with speech disorder and potential influential factors. Results: There were 145 children in the speech sound disorder group, including 110 males and 35 females respectively, with an age of (5.9±1.0) years; 117 children in the stuttering group, including 91 males and 26 females, with an age of (5.8±1.0) years; 100 children in the healthy group, including 75 males and 25 females, with an age of (5.7±1.2) years. The variations in overall language, expressive language, and syntax scores among 3 groups of children were statistically significant (92±18 vs.96±11 vs. 98±11, 81±18 vs. 84±14 vs. 88±13, 87±16 vs. 89±11 vs. 91±10, F=5.46, 4.69, 3.68, all P<0.05). Pairwise comparison revealed that the speech sound disorder group had lower scores in overall language, expressive language, and syntactic compared to the healthy group, and the differences were statistically significant (all P<0.01) and the overall language score was lower than that of children with stuttering (P<0.05). In terms of overall language and expressive language, there was a statistically significant difference in the incidence of language delay among the three groups of children (15.9% (23/145) vs. 20.5% (24/117) vs. 7.0% (7/100), 46.2% (67/145) vs. 39.3% (46/117) vs. 26.0% (26/100); χ2=7.93, 10.28; both P<0.05). In terms of overall language, the stuttering group took up the highest proportion. In terms of expressive language, the speech sound disorder group accounted for the highest amount. The incidence of language delay in children with speech disorder was 44.3% (116/262). Non-parent-child reading, daily screen time ≥1 hour and screen exposure before 1.5 years of age are risk factors for the development of language in children with speech disorder (OR=1.87, 2.18, 2.01; 95%CI 1.07-3.27, 1.23-3.86, 1.17-3.45; all P<0.01). Negative family history are protective factors for the progress of language ability (OR=0.37, 95%CI 0.17-0.81, P<0.05). Conclusions: Children with speech disorder tend to have easy access to language delay, especially in expressive language and syntax. The occurrence of language delay in children with speech disorder is tightly connected with factors such as the family medical history, parent-child reading, screen time, etc. Attention should be paid to the development of language in children who suffer from speech disorder.

Measurement of third order coherence by in situ autocorrelation for determining three-photon cross-sections

We show theoretically that the third order coherence at zero delay can be obtained by measuring the second and third order autocorrelation traces of a pulsed laser. Our theory enables the measurement of a fluorophore’s three-photon cross-section without prior knowledge of the temporal profile of the excitation pulse by using the same fluorescent medium for both the measurement of the third order coherence at zero delay as well as the cross-section. Such an in situ measurement needs no assumptions about the pulse shape nor group delay dispersion of the optical system. To verify the theory experimentally, we measure the three-photon action cross-section of Alexa Fluor 350 and show that the measured value of the three-photon cross-section remains approximately constant despite varied amounts of chirp on the excitation pulses.

Design and development of square stub loaded band pass filter with quality factor analysis

In this paper, a compact square stub-loaded band pass filter (BPF) is designed and investigated for quality factor improvement analysis. A detailed analysis has been presented to demonstrate the superior power handling capability of the proposed microstrip bandpass filter without any degradation in its electrical performance parameters. For this purpose, square-type stubs are incorporated in the proposed bandpass filter which reduced the maximum peak voltage and increased the high peak threshold, instead of using sharp edges. Also, an in-depth analysis of peak voltage with a center frequency of 2.1 and 4.2 have been carried out by considering some parameters like pressure and quality. The proposed bandpass filter shows minimum peak voltage of 1.61 V and 1.59 V across the frequency of 2.1 GHz and 4.2 GHz which covers the application of mobile and radio altimeters. The designed BPF shows the minimum heat generation of 0.29 and 0.89 per watt at the resonating frequencies of 2.1 and 4.2 GHz. Furthermore, the proposed bandpass filter presents an in-depth analysis of several characteristic parameters such as return loss, insertion loss, power loss, delay in group and phase, current distribution, H and E field distribution and maximum power loaded and unloaded quality factor.

A Rate Hemispherical Resonator Gyroscope with Bias Stability of 0.0056°/h with Compensation of Phase Delay

A Rate Hemispherical Resonator Gyroscope with Bias Stability of 0.0056°/h with Compensation of Phase Delay

Bias-constrained integer least squares estimation: distributional properties and applications in GNSS ambiguity resolution

To accommodate the presence of bounded biases in mixed-integer models, Khodabandeh (2022) extended integer estimation theory by introducing a new admissible integer estimator. The estimator follows the principle of integer least squares estimation and is computed via the integer search method of BEAT. In this contribution, we present the probability distributions of a class of estimators to which the proposed bias-constrained integer least squares estimation belongs. Some important interferometric measuring systems, whose estimation problems can be covered by BEAT, are identified. To show the proposed estimator at work, we apply BEAT to the problem of GLONASS single-differenced (SD) ambiguity resolution. Numerical results of several short-baseline datasets are presented to illustrate why one can achieve more accurate positioning solutions when considering between-receiver SD ambiguity resolution for the cases where carrier phase data are captured on frequency-varying signals with bounded SD receiver phase delays.

Mitigating the effect of source structure in geodetic VLBI by re-weighting observations using closure delays and baseline-to-jet orientation

An ideal target for geodetic very long baseline interferometry (VLBI) is a strong and point-like radio source. In reality, most celestial sources used in geodetic VLBI have spatial structure. This is as a major source of error in VLBI Global Observing System (VGOS) and also affects legacy S/X observations. Source structure causes a systematic delay, which can affect the geodetic estimates if not modelled or otherwise accounted for. In this work, we aim to mitigate its impact by extending the stochastic model used in the least-squares fitting of the VLBI group delays. We have developed a weighting scheme to re-weight the observations by parameterizing the source structure component in terms of closure delays and jet orientation relative to the observing baseline. It was implemented in the Vienna VLBI Software. To assess the performance of the extended stochastic model, we analysed the CONT17 legacy sessions and generated suitable reference solutions for comparison. The effects of re-weighting were evaluated with respect to the session fit statistics, source-wise residuals, and geodetic parameters. We find that this relatively simple noise model consistently improves the session fit by about 5% with moderate variation from session to session. The geodetic estimates are not affected to a significant level by this new weighting method. Source-wise we see improved post-fit residuals for 63 out of a total of 91 sources observed.