Phase Calibration Technique Research Articles

Photonic Integrated Circuits for an Optical Phased Array

Optical phased arrays (OPAs) are renowned for their exceptional ability to manipulate and direct light beams, positioning them as an ideal choice for solid-state light detection and ranging (LiDAR) technologies. This review provides a comprehensive examination of the current research landscape for photonic integrated circuit (PIC)-based OPAs. It begins by addressing the critical design elements at the component level necessary for optimal functionality. This review then delves into phase calibration techniques and the overarching architecture of OPAs. It concludes by emphasizing the innovative 3-D OPA design, which stands out for its enhanced optical efficiency.

ALMA High-frequency Long-baseline Campaign in 2017: An Investigation of Phase-referencing Cycle Times and Effective Baseline Lengths Using Band-to-band and In-band Phase Calibration Techniques

Abstract The Atacama Large Millimeter/submillimeter Array can achieve unprecedented spatial resolutions of 15 to 5 mas with the longest baselines of 16 km and observing at the highest frequencies of 275–950 GHz (1.09–0.30 mm). Two conditions are paramount for successful observations at these frequencies: a phase calibrator in close proximity to the science target and a stable-enough atmosphere to provide a low residual phase rms post-phase-referencing. We investigate the effect of phase-referencing cycle times, for in-band and band-to-band (B2B) observing techniques, using close and distant phase calibrators, at bands 7, 8, and 9 for baselines >2000 m. We find that (1) the phase rms estimated from baselines longer than the effective baseline increases as a function of time . (2) The expected coherence estimated using the expected phase rms corresponds well to the achieved image coherence. (3) Faster phase-referencing cycle times (<1 minute) improve phase calibration accuracy and image coherence when close phase calibrators (<2°) are used. (4) For cycle times <2 minutes the negative impact of distant phase calibrators dominates the phase error budget. We also explore whether a theoretical parameterization of the effective baseline used to estimate the phase rms and a phase stability measurement, combined with an empirical parameterization of coherence degradation as a function of calibrator separation, is suitable in estimating the expected coherence of target images. The latter proves to be more accurate. Finally, we illustrate a pragmatic approach in establishing an optimal observing strategy via dynamic cycle times and on-calibrator scan lengths.

ALMA High-frequency Long-baseline Campaign in 2017: A Comparison of the Band-to-band and In-band Phase Calibration Techniques and Phase-calibrator Separation Angles

The Atacama Large millimeter/submillimeter Array (ALMA) obtains spatial resolutions of 15 to 5 milli-arcsecond (mas) at 275-950GHz (0.87-0.32mm) with 16km baselines. Calibration at higher-frequencies is challenging as ALMA sensitivity and quasar density decrease. The Band-to-Band (B2B) technique observes a detectable quasar at lower frequency that is closer to the target, compared to one at the target high-frequency. Calibration involves a nearly constant instrumental phase offset between the frequencies and the conversion of the temporal phases to the target frequency. The instrumental offsets are solved with a differential-gain-calibration (DGC) sequence, consisting of alternating low and high frequency scans of strong quasar. Here we compare B2B and in-band phase referencing for high-frequencies ($>$289GHz) using 2-15km baselines and calibrator separation angles between $\sim$0.68 and $\sim$11.65$^{\circ}$. The analysis shows that: (1) DGC for B2B produces a coherence loss $<$7% for DGC phase RMS residuals $<$30$^{\circ}$. (2) B2B images using close calibrators ( $<$1.67$^{\circ}$ ) are superior to in-band images using distant ones ( $>$2.42$^{\circ}$ ). (3) For more distant calibrators, B2B is preferred if it provides a calibrator $\sim$2$^{\circ}$ closer than the best in-band calibrator. (4) Decreasing image coherence and poorer image quality occur with increasing phase calibrator separation angle because of uncertainties in the antenna positions and sub-optimal phase referencing. (5) To achieve $>$70% coherence for long-baseline (16 km) band 7 (289GHz) observations, calibrators should be within $\sim$4$^{\circ}$ of the target.

RoArray: Towards More Robust Indoor Localization Using Sparse Recovery with Commodity WiFi

With the multi-antenna design of WiFi interfaces, phased array has become a promising mechanism for accurate WiFi localization. State-of-the-art WiFi-based solutions using Angle-of-Arrival (AoA), however, face a number of critical challenges. First, their localization accuracy degrades dramatically due to low Signal-to-Noise Ratio (SNR) and incoherent processing. Second, they tend to produce outliers when the available number of packets is low. Moreover, the prior phase calibration schemes are not multipath robust and accurate enough. All of the above degrade the robustness of localization systems. In this paper, we present ROArray, a RObust Array based system that accurately localizes a target even with low SNRs. The key insight of ROArray is to use sparse recovery and coherent processing across all available domains, including time, frequency, and spatial domains. Specifically, in the spatial domain, ROArray can produce sharp AoA spectrums by parameterizing the steering vector based on a sparse grid. Then, to expand into the frequency domain, it jointly estimates the Time-of-Arrival (ToAs) and AoAs of all the paths using multi-subcarrier OFDM measurements. Furthermore, through a novel multi-packet fusion scheme, ROArray is enabled to perform coherent estimation over multiple packets. Such coherent processing not only increases the virtual aperture size, which enlarges the number of maximum resolvable paths but also improves the system robustness to noise. In addition, ROArray includes an online phase calibration technique that can eliminate random phase offsets while keeping communication uninterrupted. Our implementation using off-the-shelf WiFi cards demonstrates that, with low SNRs, ROArray significantly outperforms state-of-the-art solutions in terms of localization accuracy; when medium or high SNRs are present, it achieves comparable accuracy.

A free-standing wire scattering technique to monitor calibration variations of the DIII-D density profile reflectometer.

Real-time phase calibration of the ITER profile reflectometer is essential due to the long plasma duration and expected waveguide path length changes during a discharge. Progress has been recently made in addressing this issue by employing a phase calibration technique on DIII-D that monitors calibration variations that occur during each plasma discharge. By installing a thin free-standing metallic wire (1 mm diameter) near the end of the overmoded waveguide transmission system (oriented perpendicular to the waveguide axis), the round-trip phase shift from the wire is detected simultaneously with the plasma phase shifts. Variations in the reflectometer round trip path length (∼26 m) are then calculated after each DIII-D plasma discharge, allowing the calibration phase to be accurately monitored and updated. The round-trip reflectometer path length is observed to vary by ∼3 mm (root mean square value) during a typical DIII-D discharge. Using the variations in calibration phase, the density profile measurement accuracy can be improved. Since the wire retro-reflected power is ∼0.01 of the plasma signal, minimal effect is observed on the reflected signal from the plasma. Importantly, through a suitable choice in wire diameter, the calibration signal can be made approximately independent of the V-band reflectometer launch polarization. This is particularly important on DIII-D since orthogonal X- and O-mode polarized beams are coupled into the same transmission waveguide and launch antenna.

A 76–84 GHz CMOS &lt;inline-formula&gt; &lt;tex-math notation="LaTeX"&gt;$4\times$ &lt;/tex-math&gt; &lt;/inline-formula&gt; Subharmonic Mixer With Internal Phase Correction

A CMOS $4\times $ subharmonic mixer (SHM) with an internal phase error correction mechanism operating at mm-wave frequencies is proposed in this paper. The SHM operates with a 81-GHz RF input signal and a 20-GHz local oscillator (LO) signal to produce a 1-GHz output. The single ended input is converted into octet-phase, through an active input balun, an active polyphase filter, and certain phase adders. A phase calibration technique is employed, to compensate the phase deviations due to the circuit mismatches, offering a ±5° phase adjustment between the generated phase shifts. By this technique, a close to optimal performance can be obtained, especially in terms of conversion gain and LO-IF isolation, which can be improved by 1.5 to 7.5 dB and by 5 to 17 dB, respectively. Fabricated in a 65-nm CMOS low-power technology, the prototype exhibits a conversion gain of −8 dB (without using an IF amplifier), a 1 dB compression point ( $\text{P}_{\mathrm {1dB}}$ ) of −10 dBm, a third-order intercept point (IIP3) of 1 dBm, and a noise figure of 15 dB. The power consumption is 213 mW, and port-to-port isolation is >70 dB. The achieved performance compares well with the state of the art at these high frequencies despite the use of a slower CMOS process.

A theoretical model for the cantilever motion in contact-resonance atomic force microscopy and its application to phase calibration in piezoresponse force and electrochemical strain microscopy

Contact-resonance scanning probe techniques are frequently used for characterizing the mechanical sample properties via atomic force acoustic/ultrasonic microscopy as well as for detecting sample displacement via piezoresponse force microscopy (PFM) and via electrochemical strain microscopy (ESM). For a better understanding of the measurement principle and for a quantification of the signals, a theoretical description of the cantilever motion is necessary. Here, we present a comprehensive model from which the cantilever motion can be calculated numerically. Compared to previous models, our model takes into account a sample tilt and a position-dependent electrostatic load acting on the cantilever. We demonstrate a phase calibration technique for PFM and ESM measurements, which allows us to determine the absolute excitation phase of the signal with an uncertainty of only 2° for an amplification factor of 100.

Characterization for Multiharmonic Intermodulation Nonlinearity of RF Power Amplifiers Using a Calibrated Nonlinear Vector Network Analyzer

This paper presents a novel realization of nonlinear vector network analyzer (NVNA) test-bed with a new phase calibration technique, in order to characterize the multiharmonic intermodulation nonlinearity of a radio frequency (RF) power amplifier (PA) under a large-signal modulated input. The NVNA test-bed uses a step recovery diode comb generator as the phase reference, which is driven by a pulsed-RF signal with a high duty cycle of over 99%. Hence all the multiharmonic intermodulation tones of interest can be measured at once. A multisine phase standard provided by a vector signal analyzer is used to calibrate the intermodulation tones at each harmonic on a dense spectral grid. Two harmonic phase standards with different fundamental frequencies are used to synchronize the phase calibration results at different harmonics. The validity of this paper is verified by comparing NVNA measurements with oscilloscope measurements of the same PA under test. This paper can be used to inspect the nonlinearity of RF amplifiers under large-signal modulated excitations in both the frequency and time domains.

A 7 Gb/s Embedded Clock Transceiver for Energy Proportional Links

A rapid-on/off transceiver for embedded clock architecture that enables energy proportional communication over the serial link is presented. In an energy proportional link, energy consumed by serial link is proportional to the amount of data communicated. Energy proportionality can be achieved by scaling the serial link power linearly with the link utilization, and fine grained rapid power state transition (rapid-on/off) is one such technique which can achieve this objective. In this paper, architecture and circuit techniques to achieve rapid-on/off in PLL, transmitter and receiver are discussed. Background phase calibration technique in PLL and CDR phase calibration logic in receiver enable instantaneous lock on power-on. The proposed transceiver demonstrates power scalability with a wide range of link utilization and, therefore, helps in improving overall system efficiency. Fabricated in 65 nm CMOS technology, the 7 Gb/s transceiver achieves power-on-lock in less than 20 ns. Proposed PLL achieves power-on-lock in 1 ns. The transceiver achieves power scaling by 44 $\times$ (63.7 mW-to-1.43 mW) and energy efficiency degradation by only 2.2 $\times$ (9.1 pJ/bit-to-20.5 pJ/bit), when the effective data rate (link utilization) changes by 100 $\times$ (7 Gb/s-to-70 Mb/s). The proposed transceiver occupies an active die area of 0.39 mm $^{2}$ .

A Low Noise Micro-gyroscope Interface Circuit on Chip with Demodulation Signal Phase Calibration Technique

该文针对设计了一款基于解调信号相位矫正技术的低噪声微陀螺接口电路芯片。读出电路采用全差分跨阻放大器结构优化噪声性能，获得了0.63 aF/\sqrt{Hz}的等效输入电容噪声。检测通路中采用双通道正交解调技术和解调信号相位矫正技术，完全消除了机械正交信号的干扰。芯片在0.35m CMOS工艺下实现，与电容式微陀螺的联合测试表明，微陀螺系统的输入等效噪声为0.01/s/\sqrt{Hz}，在8.5 mV//s标度因子和5 V供电电压条件下，陀螺量程达到了200/s，线性度为2 。

New antenna layout for a SuperDARN HF radar

A new antenna layout for a Super Dual Auroral Radar Network (SuperDARN) HF radar has been developed. The new layout utilizes two auxiliary arrays; one behind and one in front of the main array, rather than the single auxiliary array that existing radars use. The rear auxiliary array consists of three antennas providing beam‐steering capability while the front auxiliary array consists of a single antenna. This layout is expected to greatly improve the calculation of elevation angle of arrival. Simulations presented show the advantages and disadvantages of using twin‐terminated folded dipole (TTFD) antennas and log‐periodic dipole arrays in standard and modified SuperDARN array configurations. TTFD antennas are shown to have superior front‐to‐back ratio and beam‐steering capability but suffer from shadowing effects due to the presence of corner reflectors. Impedance‐matching techniques used in SuperDARN radars are discussed, and the results of a new matching method, exhibiting a superior voltage standing‐wave ratio over the SuperDARN frequency band, are presented. Shadowing of the main array by the front auxiliary array is investigated, and it is shown that the impact of the front array on the main array gain pattern is significantly less for the case of a single front antenna than for a four‐antenna front array. Radar phase calibration techniques are discussed, and it is proposed that the additional single‐antenna front array be used for system‐wide radar phase calibration. An algorithm for the determination of elevation angle of arrival using the new layout is also given.

Three-Dimensional Reconstruction of Man-Made Objects Using Polarimetric Tomographic SAR

The growing interest in 3-D reconstruction of targets, particularly man-made objects, has made synthetic aperture radar (SAR) tomography a hot topic in recent years. It obtains a 3-D reflectivity map by coherently processing multiple images acquired from slightly different views. This paper investigates the use of polarimetric tomographic SAR to reconstruct 3-D images of man-made objects and proposes a polarimetric 3-D reconstruction technique, based on the multiple-measurement vector compressive sensing (CS) (MMV-CS) model and Tikhonov regularization theory. The main feature of the technique is that of allowing joint reconstruction of polarimetric 3-D reflectivity maps with high resolution. For X-band tomographic SAR, we demonstrate that the phase error induced by an array element error is severe enough to prevent data focusing and propose a phase calibration technique employing prominent scatterers to adapt the proposed technique to practice. To check the plausibility of our algorithms, a ground-based SAR system is introduced, and high-resolution 3-D images obtained by processing the real collected data are presented. As special cases of the new proposed technique, both the Tikhonov regularization and the MMV-CS method reconstruct the targets successfully and give an accurate estimate for the vehicle size. Compared to the Tikhonov regularization method, the MMV-CS technique exhibits much better superresolution power and lower sidelobe level. The advantage of the MMV-CS technique over the single-measurement vector CS technique is also demonstrated, and the phase calibration algorithm is verified.

Comparative study of sorption and permeation techniques for the determination of heptane and toluene transport in polyethylene membranes

A comprehensive study of the mass transport of two volatile organic compounds (VOCs) heptane and toluene and their binary mixtures through dense semicrystalline low density polyethylene membranes (LDPE) at 25 °C is presented. The use of the widest possible concentration range (VOCs activity of 0.001–1 at given temperature) and a set of four different experimental techniques enabled to reveal differences between permeation and sorption of studied vapours and to clarify the effect of feed and instantaneous VOCs concentration inside the LDPE membrane. The differential flow permeation method and fixed-volume pressure increase method were used for pure and binary vapour permeation while sorption measurements (from liquid and vapour phases) were performed gravimetrically and by the Vapour Phase Calibration technique (VPC). This work is the first and unique comparative study on a so wide range of vapour activities and a so vast number of different techniques, giving important insight into the transport phenomena themselves and on how results are affected by the specific technique used. Results are demonstrated and discussed in detail on the basis of a pair of penetrants with different physico-chemical properties and molecular shape (toluene vs. heptane). Information about differences between concentration dependent permeation and sorption, coupling effect, molecular clustering and polymer–solvent interactions is reported as well. The establishment of specific concentration profiles inside the LDPE membrane during permeation and sorption experiments evoke time-dependent structure changes of the LDPE matrix and such chain reorganisations consequently influence the transport parameters and they are also related to a certain form of high concentration-evoked molecular aggregation (clustering). X-Ray diffraction measurements excluded that the observed phenomena could be due to significant irreversible changes in the crystallinity of the material. Toluene and heptane favourably influence one another's transport and consequently both sorption and permeation experiments reveal a distinct coupling effect. Permeation experiments show a gradual increase of the integral diffusion with increasing vapour activity whereas VPC and gravimetric sorption analysis find a maximum around activity a = 0.7. This difference is due to the deviation from Fickian behaviour at high activity and to fundamental differences in the measurement principle.

Phase calibration approaches for radar interferometry and imaging configurations: equatorial spread F results

Abstract. In recent years, more and more radar systems with multiple-receiver antennas are being used to study the atmospheric and ionospheric irregularities with either interferometric and/or imaging configurations. In such systems, one of the major challenges is to know the phase offsets between the different receiver channels. Such phases are intrinsic to the system and are due to different cable lengths, filters, attenuators, amplifiers, antenna impedance, etc. Moreover, such phases change as function of time, on different time scales, depending on the specific installation. In this work, we present three approaches using natural targets (radio stars, meteor-head and meteor trail echoes) that allow either an absolute or relative phase calibration. In addition, we present the results of using an artificial source (radio beacon) for a continuous calibration that complements the previous approaches. These approaches are robust and good alternatives to other approaches, e.g. self-calibration techniques using known data features, or for multiple-receiver configurations constantly changing their receiving elements. In order to show the good performance of the proposed phase calibration techniques, we present new radar imaging results of equatorial spread F (ESF) irregularities. Finally we introduce a new way to represent range-time intensity (RTI) maps color coded with the Doppler information. Such modified map allows the identification and interpretation of geophysical phenomena, previously hidden in conventional RTI maps, e.g. the time and altitude of occurrence of ESF irregularities pinching off from the bottomside and their respective Doppler velocity.

A nonlinear propagation model-based phase calibration technique for membrane hydrophones

A technique for the phase calibration of membrane hydrophones in the frequency range up to 80 MHz is described. This is achieved by comparing measurements and numerical simulation of a nonlinearly distorted test field. The field prediction is obtained using a finite-difference model that solves the nonlinear Khokhlov-Zabolotskaya-Kuznetsov (KZK) equation in the frequency domain. The measurements are made in the far field of a 3.5 MHz focusing circular transducer in which it is demonstrated that, for the high drive level used, spatial averaging effects due to the hydrophone's finite-receive area are negligible. The method provides a phase calibration of the hydrophone under test without the need for a device serving as a phase response reference, but it requires prior knowledge of the amplitude sensitivity at the fundamental frequency. The technique is demonstrated using a 50-microm thick bilaminar membrane hydrophone, for which the results obtained show functional agreement with predictions of a hydrophone response model. Further validation of the results is obtained by application of the response to the measurement of the high amplitude waveforms generated by a modern biomedical ultrasonic imaging system. It is demonstrated that full deconvolution of the calculated complex frequency response of a nonideal hydrophone results in physically realistic measurements of the transmitted waveforms.

Phase Calibration Technique for Mismatch Optimization in Image-Reject Receivers

This paper presents phase calibration technique without using any external tone for weaver image-reject receiver. Error signal (phase mismatch information) is generated using a simple algorithm and this signal is used for mismatch elimination. Calibration system has been implemented using simulink which shows an image rejection ratio of 59.5 dB can be achieved for RF signal operating at 1.8 GHz.

Range imaging observations of PMSE using the EISCAT VHF radar: Phase calibration and first results

Abstract. A novel phase calibration technique for use with the multiple-frequency Range IMaging (RIM) technique is introduced based on genetic algorithms. The method is used on data collected with the European Incoherent SCATter (EISCAT) VHF radar during a 2002 experiment with the goal of characterizing the vertical structure of Polar Mesosphere Summer Echoes (PMSE) over northern Norway. For typical Doppler measurements, the initial phases of the transmitter and receiver are not required to be the same. The EISCAT receiver systems exploit this fact, allowing a multi-static configuration. However, the RIM method relies on the small phase differences between closely spaced frequencies. As a result, the high-resolution images produced by the RIM method can be significantly degraded if not properly calibrated. Using an enhanced numerical radar simulator, in which data from multiple sampling volumes are simultaneously generated, the proposed calibration method is validated. Subsequently, the method is applied to preliminary data from the EISCAT radar, providing first results of RIM images of PMSE. Data using conventional analysis techniques, and confirmed by RIM, reveal an often-observed double-layer structure with higher stability in the lower layer. Moreover, vertical velocity oscillations exhibit a clear correlation with the apparent motion of the layers shown in the echo power plots.