Maximum Phase Shift Research Articles

Spectral changes induced by a phase modulator acting as a time lens

We show both numerically and experimentally that a phase modulator, acting as a time lens in the Fourier-lens configuration, can induce spectral broadening, narrowing, or shifts, depending on the phase of the modulator cycle. These spectral effects depend on the maximum phase shift that can be imposed by the modulator. In our numerical simulations, pulse spectrum could be compressed by a factor of 8 for a 30 rad phase shift. Experimentally, spectral shifts over a 1.35 nm range and spectral narrowing and broadening by a factor of 2 were demonstrated using a lithium niobate phase modulator with a maximum phase shift of 16 rad at a 10 GHz modulation frequency. All spectral changes were accomplished without employing optical nonlinear effects such as self- or cross-phase modulation.

An Integrable SIW Phase Shifter in a Partially Magnetized Ferrite LTCC Package

There is a growing need for small size integrable phased antenna arrays for emerging satellite communications on-the-move applications. Traditional ferrite-based phase shifters are generally bulky due to the need of electromagnets for biasing, yielding them unsuitable for this kind of application. In this paper, a novel compact light-weight substrate integrated waveguide (SIW) based phase shifter realized in a multi-layer ferrite low-temperature co-fired ceramic package with embedded bias windings is reported. By using embedded windings and operating the material in a partially magnetized state, the required bias magnetic field could be significantly reduced from typically about 1000 Oe to less than 50 Oe. Moreover, the presented phase shifter has two modes of operations corresponding to two different biasing scenarios of the SIW, namely, symmetric and anti-symmetric bias. Under anti-symmetric bias, the phase shifter can achieve high nonreciprocal phase shift, whereas under symmetric bias, the phase shift is reciprocal, but the available phase shift is less than the anti-symmetric case. The fabricated prototype operates in the 11.5–13.5-GHz range and has a peak figure of merit (phase shift per decibel of loss) of 102 $^{\circ}/{\hbox{dB}} $ and a maximum phase shift per unit length of 153 $^{\circ} /{\hbox{cm}}$ , which are more than five times the previously reported figures for this technology. Due to the use of embedded windings, the presented phase shifter offers a huge size reduction from the order of ${\hbox{cm}}^{3}$ to ${\hbox{mm}}^{3}$ , making it particularly useful for mobile phased-array applications.

Starch Consolidation Casting of Cordierite Precursor Mixtures—Rheological Behavior and Green Body Properties

The rheology of suspensions and mechanical properties of green bodies with cordierite composition (raw materials 37 wt% kaolin, 41 wt% talc, 22 wt% alumina, resulting in 46.6 wt% SiO2, 38.1 wt% Al2O3, 13.6 wt% MgO) and two types of starch (corn or potato) are investigated. Rotational viscometry of suspensions with solids loading 50, 60, and 70 wt% without starch showed that all tend to be shear‐thinning with a small degree of thixotropy. Suspensions with a total solids loading of 60 wt% with 25 wt% replaced by starch exhibited higher viscosity and thixotropy, but the viscometric behavior is almost identical for the two starch types (apparent viscosities 130–50 mPa·s). Oscillatory rheometry shows that for suspensions with potato starch the onset temperature for gelatinization is 61°C–63°C, that is, lower than for corn starch (72°C–73°C). Maximum storage moduli and phase shift values after gelatinization are similar for both systems. The mechanical properties of green disks, measured via diametral compression tests, reveal clear differences between materials prepared with corn and potato starch, with the latter showing higher elastic modulus, higher strength, and higher deformation at fracture, obviously because of incompletely gelatinized starch granules in the green bodies prepared with corn starch.

Cylindrical Liquid Crystal Microlens Array With Rotary Optical Power and Tunable Focal Length

A novel cylindrical liquid crystal microlens array with rotary power and tunable capability is proposed and experimentally demonstrated. This structure is capable of generating tunable cylindrical microlenses in two different axis by low voltage control. For this, complex electrical signals are required (electrical phase shift of 180°). A control over the maximum phase shift from $4\pi $ to $34\pi $ radians has been demonstrated. This effect modifies the effective focal length (from 0.2 to 1.2 mm). Moreover, an OFF-state is also possible (behaving like a transparent medium). The structure is simple and does not require a complex fabrication process. The proposed device has several advantages over the existing microlens arrays and is simple and low cost. The device could contribute to developing new applications and to reducing the fabrication costs of current devices. For example, this device can be used in the next generation of mobile displays with autostereoscopic capability.

Seismic reflection dispersion due to wave-induced fluid flow in heterogeneous reservoir rocks

We have investigated the impact of wave-induced fluid flow, including Biot flow and mesoscopic flow, on the signatures of seismic reflectivity in heterogeneous reservoir rocks. We have incorporated the dynamic poroelastic responses of mesoscopic flow into the classical Biot theory. The resulting effective Biot media could capture the characteristics of velocity dispersion and wave attenuation in heterogeneous poroelastic media. On the basis of this effective Biot media, an approach was developed to compute the poroelastic reflection at arbitrary angles and frequencies from the boundary of two heterogeneous porous media. The computed poroelastic reflections not only depended on the elastic properties’ contrast and incident angle, but also relied on the fluid mobility and observational frequency. For a typical sand-shale reflector, with the given rock and fluid properties, we found that the effect of mesoscopic flow causes P-wave reflection amplitude variations with the frequency being as high as 40% and a maximum phase shift as high as 16° at the seismic exploration frequency band. In addition, it was found that the amplitude variation with offset intercept and the gradient at the poroelastic interface were impacted by the mesoscopic flow and had a decreasing trend with frequency. Therefore, ignoring the impact of mesoscopic flow could possibly lead to uncertainty in seismic imaging as well as quantitative interpretation of reservoir properties. In comparison, the Biot flow-induced seismic dispersion effect, which occured at a very high-frequency range, was almost negligible.

Comparison of Injection-Locked and Coupled Oscillator Arrays for Beamforming

Injection-locked oscillator arrays (ILOAs) and coupled oscillator arrays (COAs) are analyzed using Adler’s equation, and their performance to drive phased arrays for beam-steering is compared. The Monte Carlo simulation results indicate that COAs render smaller beam-pointing error when the locking range of oscillators is narrow (high $Q$ ), while ILOAs render smaller beam-pointing error when the locking range is wide (low $Q$ ). An ILOA with a frequency tripler connected to the oscillators’ output is designed to increase the achievable range of inter-element phase shift, and a chip is fabricated in the TSMC 0.18- $\mu$ m CMOS technology to verify the design concept, with the measured maximum phase shift around 240 $^\circ$ .

An Alternative Method for PM Signal Generation and Detection

ABSTRACTThis paper presents a novel scheme for generating a phase modulated (PM) continuous wave carrier of constant envelope and the corresponding demodulation scheme. The modulator is based on the principle of the quadrature carrier multiplexing (QCM) wherein the sine wave carrier is multiplied by the message signal, m(t), and the cosine wave carrier is multiplied by the modified signal, √ (1–m2(t)), with the constraint that │m(t)│<1. The demodulator includes an amplitude limiter, a bandpass filter, and a coherent detector. The proposed scheme introduces a maximum linear phase shift of about ±20° when the message signal amplitude is 0.9 V. The phase shift introduced into the carrier is linear to the tune of ±360° as the message signal amplitude is reduced. The proposed scheme allows for the use of high-frequency stable quadrature oscillators in the modulator and offers better noise immunity like the conventional PM carrier. Furthermore, this paper presents a view point that the existing analogue modulation schemes can be viewed as special cases of the QCM principle.

Monolithic Microwave Nonlinear Phase Shifter

A microstrip-based microwave phase shifter that includes a thin Fe film as the active element was designed and fabricated. The device is a monolithic microwave structure that is lightweight and can be integrated on a semiconductor chip. At a fixed frequency, a large change in the phase, , was observed as the power was varied. For 1GHz below the resonance frequency, the maximum power-dependent phase shift is δφ = 55°, and for 1GHz above the resonance frequency the maximum phase shift is δφ = 74°. The experimental results show three different regimes: 1) a linear regime for powers up to 6.3 mW, 2) a stable nonlinear regime for power levels from 6.3 mW to about 1W, and above this, 3) an unstable nonlinear regime. The second regime can be used for microwave signal processing.

Low Loss, Wideband, and Compact CPW-Based Phase Shifter for Millimeter-Wave Applications

This paper proposes a compact, low-loss, and low cost phase shifter for millimeter-wave phased array systems. The basic idea is to modify the propagation mode of a coplanar waveguide (CPW) by placing a high dielectric constant (40 <; ε <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">r</sub> <; 170) slab on top of it. The phase shift is varied by changing the air gap between the CPW line and the dielectric slab. A piezoelectric transducer has been used to control this air gap precisely. For fast but accurate modeling of the proposed phase shifter, two methods one based on spectral domain analysis and the other based on the conformal mapping have been developed and verified with full wave simulations and measurements. A prototype structure with the operational frequency range from 20 to 40 GHz is presented. The maximum phase shift obtained for the electrically controlled version at 40 GHz is 103 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">°</sup> with loss variation of 0.2 dB. The total length is 2 mm.

Reflective vertical cavity quantum-well saturable absorber as an all-optical nonlinear phase-shifting element

A scheme of an all-optical nonlinear phase-shifting element is proposed, based on a reflective vertical cavity semiconductor (quantum-well) saturable absorber (R-VCSSA). The nonlinear round-trip phase shift in a low-intensity resonant VCSSA is obtained at an input intensity due to the saturating nonlinearity in index change and optically induced thermal effects. An enhanced large nonlinear positive or negative phase shift incurred in a reflected signal is investigated analytically with the wavelength tuning of the probe signal around the low-intensity resonant wavelength of a Fabry&#x2013;Perot cavity. The device may be useful in compensating the phase of an input signal, either positive or negative, in long-haul fiber communications. A representative InGaAs/InP quantum-well-based VCSSA is considered to demonstrate the phase shift in the pump&#x2013;probe configuration. With a device speed of 10&#xA0;GHz, maximum phase shifts of &#x2212;0.24 and +0.14&#x2009;&#x2009;rad at pump power of 19.2&#xA0;mW are observed for the operations at probe wavelengths of 1555.6 and 1557.8&#xA0;nm, respectively.

Tunable Ultrawideband Phase Shifters With Magnetodielectric Disturber Controlled by a Piezoelectric Transducer

A new tunable ultrawideband phase shifter with magnetodielectric disturber controlled by a piezoelectric transducer has been developed in this paper. With their high relative permeability, magnetodielectric materials show great potential in microwave circuit and device designs. Novel ultrawideband phase shifter designs with conductor-backed coplanar waveguide were compared and investigated. NiCo-ferrite films were adopted to laminate the magnetodielectric material perturber on a dielectric Rogers material substrate. A maximum relative phase shift of 384° at 20 GHz with respect to the unperturbed condition has been achieved for the conductor backed coplanar waveguide structure.

Investigation of the nonlocal nonlinear optical response of copper nanostructured thin films prepared by pulsed laser deposition

Nanostructured copper thin films have been prepared using the pulsed laser deposition method. Optical absorption spectra of these films exhibit plasmonic absorption peaks around , which suggests the formation of copper nanoparticles on their surfaces. Scanning electron micrographs of the films confirm the nanoparticle formation on the films surfaces. After laser beam passing through the thin films, the observed diffraction rings on a far-field screen have been recorded. Despite the smallness of the maximal axial phase shifts of the films, which have been obtained using the nonlocal -scan theory, a series of low-intensity rings can be observed on the far field screen for some specific positions of the thin films from the focal point. It is shown that the best approach to determining the sign and magnitude of the nonlinear refractive index of thin samples is the application of the conventional close-aperture -scan method.

A Fully Integrated Multilayer Power Distribution Network for SAR Dual-Polarized Linear Arrays

The design, manufacturing and testing of a planar technology, fully integrated, multilayer, dual-polarized power distribution network, feeding a six element X-band linear array is presented. The selected technology, not used yet for space applications, is particularly suitable for large scale, low cost manufacturing. The proposed architecture provides an isolation between the two polarizations better than 40 dB, an input ports return loss better than 25 dB, and a 0.6 dB worst case amplitude unbalancing with a maximum phase shift of about 9 degrees between output ports, within a 16.7% bandwidth.

버틀러 매트릭스의 설계 및 구현

주파수 이용효율을 높이는 방법으로 빔포밍 기술을 사용한다. 본 논문에서는 무선랜 주파수 대역에서 RF 빔포머로 사용할 수 있는 버틀러 매트릭스를 설계 및 제작하였다. 구현한 버틀러 매트릭스는 2.4~2.485GHz의 주파수 범위에서 삽입손실은 최대 6.7dB, 최대 위상천이 오차는 <TEX>$-6.51^{\circ}{\sim}7.17^{\circ}$</TEX> 갖는다. Beam forming techniques are used to increase the efficiency of using frequency. In this paper we design and implement Butler matrix to be used for ISM band. The implemented Butler matrix has the insertion loss of maximum 6.7dB and the maximum phase shift error of <TEX>$-6.51^{\circ}{\sim}7.17^{\circ}$</TEX> over 2.4~2.485GHz.

An experimental study of steep solitary wave reflection at a vertical wall

Until now very few experimental investigations have been conducted to study the reflection of steep solitary waves at a vertical wall whereas many theoretical analyses and numerical simulations have been developed in the past. The use of experimental techniques to capture the waveform and associated phenomena during the short-time head-on collision of two solitary waves (or the reflection of a solitary wave by a vertical wall) is not an easy task. Solitary waves with amplitude a/h≤0.556 are experimentally generated by a piston type wavemaker. We have used a high speed camera and our experimental results were compared with previous studies, including both theoretical investigations and numerical simulations.Experimental values of attachment and detachment times, wall residence time, maximum run-up time and phase shift due to reflection at the wall as a function of solitary wave amplitude are new results. In addition, we found that previous theoretical results underestimate wave run-up characteristics (maximal run-up amplitude, attachment and detachment times, wall residence time), except the third-order result of Su and Mirie (1980) who calculated maximal run-up which is in good agreement with experiments. Within the range of solitary wave amplitude considered experimentally, present measurements are in excellent agreement with numerical results of Cooker et al. (1997) and Chambarel et al. (2009).For very steep solitary waves we found numerically the occurrence of a Rayleigh–Taylor instability on the top of the jet due to the head-on collision. A theoretical proof of the existence of this instability is given. Furthermore, the occurrence of this instability is corroborated by numerical computations of the vertical gradient of underwater pressure during the collision of the solitary waves.

Simulation Method for Predicting Tissue Electrical Properties During Colonoscopy1

Simulation Method for Predicting Tissue Electrical Properties During Colonoscopy1

Lock-in thermal imaging for the early-stage detection of cutaneous melanoma: A feasibility study

This paper theoretically evaluates lock-in thermal imaging for the early-stage detection of cutaneous melanoma. Lock-in thermal imaging is based on the periodic thermal excitation of the specimen under test. Resulting surface temperature oscillations are recorded with an infrared camera and allow the detection of variations of the sample׳s thermophysical properties under the surface. In this paper, the steady-state and transient skin surface temperatures are numerically derived for a different stage of development of the melanoma lesion using a two-dimensional axisymmetric multilayer heat-transfer model. The transient skin surface temperature signals are demodulated according to the digital lock-in principle to compute both a phase and an amplitude image of the lesions. The phase image can be advantageously used to accurately detect cutaneous melanoma at an early stage of development while the maximal phase shift can give precious information about the lesion invasion depth. The ability of lock-in thermal imaging to suppress disturbing subcutaneous thermal signals is demonstrated. The method is compared with the previously proposed pulse-based approaches, and the influence of the modulation frequency is further discussed.

Love Wave Ultraviolet Photodetector Fabricated on a TiO2/ST-Cut Quartz Structure

A TiO2thin film deposited on a 90° rotated 42°45′ ST-cut quartz substrate was applied to fabricate a Love wave ultraviolet photodetector. TiO2thin films were grown by radio frequency magnetron sputtering. The crystalline structure and surface morphology of TiO2thin films were examined using X-ray diffraction, scanning electron microscope, and atomic force microscope. The effect of TiO2thin film thickness on the phase velocity, electromechanical coupling coefficient, temperature coefficient of frequency, and sensitivity of ultraviolet of devices was investigated. TiO2thin film increases the electromechanical coupling coefficient but decreases the temperature coefficient of frequency for Love wave propagation on the 90° rotated 42°45′ ST-cut quartz. For Love wave ultraviolet photodetector application, the maximum insertion loss shift and phase shift are 2.81 dB and 3.55 degree at the 1.35-μm-thick TiO2film.

Optical self-phase modulation using a new photonic crystal coupled-cavity waveguide

In this paper, self-phase modulation of an optical pulse using a new photonic crystal coupled-cavity waveguide is simulated and analyzed. The structure of the new coupled-cavity waveguide is introduced and its advantage over the previous type of coupled-cavity waveguide is discussed. In order to obtain a high group index over a large bandwidth and benefit from the slow light phenomenon, the group index and group velocity dispersion parameter curves of the guided mode are calculated. Finally, the transient simulation of the structure is performed using a finite-difference time-domain method. The calculated required length of the coupled-cavity waveguide for a maximum phase shift of π is about 31 μm. Spectral broadening of the optical pulse as a result of self-phase modulation is also presented and discussed.

Design and development of a CPW-based 5-bit switched-line phase shifter using inline metal contact MEMS series switches for 17.25 GHz transmit/receive module application

A radio frequency micro-electro-mechanical system (RF-MEMS) phase shifter based on switchable delay line concept with maximum desirable phase shift and good reliability is presented in this paper. The phase shifter is based on the switchable reference and delay line configurations with inline metal contact series switches that employs MEMS systems based on electrostatic actuation and implemented using coplanar waveguide (CPW) configuration. Electromechanical behaviour of the MEMS switch has been extensively investigated using commercially available simulation tools and validated using system level simulation. A detailed design and performance analysis of the phase shifter has been carried out as a function of various structural parameters with reference to the gold-based surface micromachining process on alumina substrate. The mechanical, electrical, transient, intermodulation distortion (IMD) and loss performance of an MEMS switch have been experimentally investigated. The individual primary phase-bits (11.25°/22.5°/45°/90°/180°) that are fundamental building blocks of a complete 5-bit phase shifter have been designed, fabricated and experimentally characterized. Furthermore, two different 5-bit switched-line phase shifters, that lead to 25% size reduction and result in marked improvement in the reliability of the complete 5-bit phase shifter with 30 V actuation voltage, have been developed. The performance comparison between two different CPW-based switched-line phase shifters have been extensively investigated and validated. The complete 5-bit phase shifter demonstrates an average insertion loss of 5.4 dB with a return loss of better than 14 dB at 17.25 GHz. The maximum phase error of 1.3° has been obtained at 17.25 GHz from these 5-bit phase shifters.