Continuous Phase Shift Research Articles

Electronically Steerable and Fixed-Beam Frequency-Tunable Planar Traveling-Wave Antenna

The design of an electronically steerable wideband planar traveling-wave antenna is presented. The proposed antenna has a very simple structure based on a microstrip line loaded with several radiating elements and phase shifters between them. The phase shifters are based on tunable capacitances, in order to perform a continuous phase shift between the radiating elements and control the main beam direction. The radiating elements are complementary strip slots that have a very broad impedance bandwidth, thus allowing the antenna to have two different modes of operation: maintaining the main lobe direction over a significant bandwidth, 1.71–2.17 GHz, and performing a main beam scanning over this bandwidth with a maximum angle range of $-45^{\circ}$ to 45° at 2 GHz.

Reconfigurable Phase Shifted Fiber Bragg Grating Using Localized Micro-Strain

A simple and precise method for tuning of localized phase shift in fiber Bragg grating (FBG) using mechanical micro-strain is proposed and experimentally verified. Positive and negative continuous phase shifts tuning between 0 and +π/-π in a uniform FBG is experimentally demonstrated using confined micro-strain in a beam bending configuration. The magnitudes of the temporary phase shifts can be linearly controlled by changing the load displacement, with set-and-forget capability.

SIMULATION OF CO-PLANAR WAVEGUIDE LIQUID CRYSTAL BASED PHASE SHIFTER

This paper discussed the design and performances of a liquid crystal phase shifter that can be used in tuning devices. Tuning devices growth with the demand in the emerging in telecommunication system. Tuning devices with smooth continuous phase shifting at low cost and compact size would be an advantage. This paper proposed a phase shifter using 5CB liquid crystal material. The advantages of using the material is the smoothness and continuity of the transitions in the phase shift. It is done by having a structure with cavity filled with the liquid crystal and applied with certain voltage that can be changed. The changes in voltage would change the applied electric field, and thus would change the permittivity of the material. The changes would affect the wave propagation and thus contribute to the phase shifting. The performance of the phase shifter was tested by means of simulation using CST Suite 2014 software. The results show that the higher the frequency, the higher the phase shift would occur. The highest FoM achieved is 68 (deg/dB) at 8 GHz. A phase shifter with smooth and continuous phase shift can be used as the feeding network in an array scanning antennas systems.

Technical Note: MR‐visualization of interventional devices using transient field alterations and balanced steady‐state free precession imaging

In interventional magnetic resonance imaging, instruments can be equipped with conducting wires for visualization by current application. The potential of sequence triggered application of transient direct currents in balanced steady-state free precession (bSSFP) imaging is demonstrated. A conductor and a modified catheter were examined in water phantoms and in an ex vivo porcine liver. The current was switched by a trigger pulse in the bSSFP sequence in an interval between radiofrequency pulse and signal acquisition. Magnitude and phase images were recorded. Regions with transient field alterations were evaluated by a postprocessing algorithm. A phase mask was computed and overlaid with the magnitude image. Transient field alterations caused continuous phase shifts, which were separated by the postprocessing algorithm from phase jumps due to persistent field alterations. The overlaid images revealed the position of the conductor. The modified catheter generated visible phase offset in all orientations toward the static magnetic field and could be unambiguously localized in the ex vivo porcine liver. The application of a sequence triggered, direct current in combination with phase imaging allows conspicuous localization of interventional devices with a bSSFP sequence.

Generation of Optical Vortices by an Ideal Liquid Crystal Spiral Phase Plate

An ideal spiral phase plate based on liquid crystals and two high resistivity layers is proposed and theoretically analyzed. The proposed structure generates a spiral-like voltage with simple voltage control. The liquid crystal layer produces an optical phase shift that depends on the voltage distribution. These two effects cause light passing through the device to be twisted like a corkscrew around its travel axis. Because of the continuous phase shift, the proposed device is expected to exhibit a conversion efficiency of ~100%. In addition, this device is more efficient and simpler than previously reported optical vortex generators. Moreover, the device is completely reconfigurable, i.e., the operating wavelengths and topological charges are tunable. The device can be used to reduce the fabrication costs of current devices and generate different orbital angular momentum modes with improved light efficiency, simplicity, and possibility of reconfiguration.

Electron waveguide interferometers for spin‐dependent transport experiments

Semiconductor nanostructures are of interest in the field of spintronics, because they allow us to employ special features of low‐dimensional transport for spin polarization, manipulation, and detection. Proposals for spintronic devices are based on coherent transport and interference effects in extended electron waveguide (EWG) structures. We present the state‐of‐the‐art of low‐dimensional EWGs and Aharonov–Bohm (AB) interferometers, fabricated in GaAs/AlGaAs heterostructures. Low‐temperature measurements in etched quantum point contacts (QPCs) show large subband spacing and, in the presence of a source–drain DC bias, the differential conductance is resonantly enhanced due to a many‐body modification of the barrier potential because of spin fluctuations. Multiterminal asymmetric quantum wire rings (QRs) have been fabricated and AB conductance oscillations are used to detect electrostatically induced continuous phase shifts and ‐phase jumps, due to resonances and reflections at cross‐junctions. The effects of measurement configuration and non‐equilibrium in QR structures are also studied. By embedding a QPC into the leads of a QR, coherent mode‐filtered injection of electrons into a few‐mode AB interferometer is demonstrated. Single‐ and few‐mode spin transport in EWG interferometers is discussed and the opportunities offered by embedding quantum dots for studying interaction and spin effects are presented. The results encourage the investigation of spin‐dependent quantum transport in extended EWG interferometers.

Colloidal Quantum Dots-PMMA Waveguides as Integrable Microwave Photonic Phase Shifters

A novel scheme for the control of microwave signals carried at optical wavelengths by use of PbS colloidal quantum dots embedded in PMMA waveguides is presented. When these structures are pumped at wavelengths where PbS has efficient absorption (980 or 1310 nm), a phase shift in a signal carried at 1550 nm is induced. Optimal conditions have been analyzed by studying the influence of the microwave signal and the waveguide structure. In a proof-of-concept experiment, a continuous phase shift up to 35 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">°</sup> at 25 GHz has been demonstrated, with good thermal stability ( at 25 GHz) when the samples are heated 20 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">°</sup> C above room temperature. The potential benefits of the use of this active-waveguide technology in microwave photonics are due to the continuous scan of the phase delay, its high tuning speed, and its small size, which leads to the possibility of integration.

Apply current exponential de Finetti theorem to realistic quantum key distribution

In the realistic quantum key distribution (QKD), Alice and Bob respectively get a quantum state from an unknown channel, whose dimension may be unknown. However, while discussing the security, sometime we need to know exact dimension, since current exponential de Finetti theorem, crucial to the information-theoretical security proof, is deeply related with the dimension and can only be applied to finite dimensional case. Here we address this problem in detail. We show that if POVM elements corresponding to Alice and Bob's measured results can be well described in a finite dimensional subspace with sufficiently small error, then dimensions of Alice and Bob's states can be almost regarded as finite. Since the security is well defined by the smooth entropy, which is continuous with the density matrix, the small error of state actually means small change of security. Then the security of unknown-dimensional system can be solved. Finally we prove that for heterodyne detection continuous variable QKD and differential phase shift QKD, the collective attack is optimal under the infinite key size case.

Laser-phased-array beam steering controlled by lithium niobate waveguides

A laser steering system based on the Ti-diffusion lithium niobate (LiNbO3) waveguides is presented. A phase shifter based on the LiNbO3 waveguide is designed. This waveguide can provide a continuous phase shift for laser-phased-array (LPA) by changing the voltage loaded on it. The theory of irregular LPA based on the Ti-diffusion LiNbO3 waveguide phase shifter is studied numerically and experimentally. Beam steering with an angle of 1.37 deg is gained by a 1 × 3 array setup that agrees

Linear and stable photonic radio frequency phase shifter based on a dual-parallel Mach–Zehnder modulator using a two-drive scheme

We theoretically and experimentally demonstrate a linear and stable photonic RF phase shifter based on a dual-parallel Mach-Zehnder modulator (DPMZM) using a two-drive scheme. To avoid the effect of the residual optical carrier and overcome the lowest frequency limit from the optical filter, a local microwave signal and a signal up-converted from the under-phase-shifted RF signal are applied to the two RF inputs of the DPMZM, respectively. A phase-shifted RF signal is generated by beating the two first-order upper sidebands located in the passband of the optical filter. A continuous and linear phase shift of more than 360° and power variation of less than ±0.15 dB at 1GHz are achieved by simply tuning the bias voltage of the modulator. A phase tuning bandwidth of more than 17MHz and phase drift of less than 0.5° within 2000s are also observed.

Continuous Active Phase Shifter Design and Analysis for Millimeter-Wave Circuits

This brief presents a continuous active phase shifter for millimeter-wave phased-array transceivers. Having an all-pass network frequency response, the proposed phase shifter provides continuous insertion phase control and nearly constant insertion loss regardless of the insertion phase variation. A complete analysis for the phase shifter is provided along with circuit measurement results. The phase shifter is fabricated in a 0.13-μm commercial CMOS technology. A phase tuning range larger than 90 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">°</sup> and -7 dB of insertion loss are achieved for the phase shifter.

Transport control of dust particles via the electrical asymmetry effect: experiment, simulation and modelling

The control of the spatial distribution of micrometre-sized dust particles in capacitively coupled radio frequency discharges is relevant for research and applications. Typically, dust particles in plasmas form a layer located at the sheath edge adjacent to the bottom electrode. Here, a method of manipulating this distribution by the application of a specific excitation waveform, i.e. two consecutive harmonics, is discussed. Tuning the phase angle θ between the two harmonics allows one to adjust the discharge symmetry via the electrical asymmetry effect (EAE). An adiabatic (continuous) phase shift leaves the dust particles at an equilibrium position close to the lower sheath edge. Their levitation can be correlated with the electric field profile. By applying an abrupt phase shift the dust particles are transported between both sheaths through the plasma bulk and partially reside at an equilibrium position close to the upper sheath edge. Hence, the potential profile in the bulk region is probed by the dust particles providing indirect information on plasma properties. The respective motion is understood by an analytical model, showing both the limitations and possible ways of optimizing this sheath-to-sheath transport. A classification of the transport depending on the change in the dc self-bias is provided, and the pressure dependence is discussed.

Propagation of femtosecond terawatt laser pulses in N2 gas including higher-order Kerr effects

Propagation characteristic of femtosecond terawatt laser pulses in N2 gas with higher-order Kerr effect (HOKE) is investigated. Theoretical analysis shows that HOKE acting as Hamiltonian perturbation can destroy the coherent structure of a laser field and result in the appearance of incoherent patterns. Numerical simulations show that in this case two different types of complex structures can appear. It is found that the high-order focusing terms in HOKE can cause continuous phase shift and off-axis evolution of the laser fields when irregular homoclinic orbit crossings of the field in phase space take place. As the laser propagates, small-scale spatial structures rapidly appear and the evolution of the laser field becomes chaotic. The two complex patterns can switch between each other quasi-periodically. Numerical results show that the two complex patterns are associated with the stochastic evolution of the energy contained in the higher-order shorter-wavelength Fourier modes. Such complex patterns, associated with small-scale filaments, may be typical for laser propagation in a HOKE medium.

Modeling the dynamic flow–fiber interaction for microscopic biofluid systems

Microscopic flow–fiber interaction is frequently encountered in biofluid systems. In this paper, we propose a three-dimensional numerical model for such systems, including a spring network model for the elastic fiber, the lattice Boltzmann method for the fluid flow, and the immersed boundary method for the flow–structure interaction. Simulations are also conducted to examine the fiber deformation under constant and sinusoidal shear conditions. While an equilibrium state can be reached under a constant shear, periodic oscillation in fiber shape is observed in a sinusoidal shear flow, at a frequency identical to that of the imposed shear flow. A continuous phase shift of the fiber oscillation is also noticed along the fiber. These simulations demonstrate the potential usefulness of this model in microscopic biofluid and other systems, and further studies are necessary to investigate the dynamic flow–fiber interaction in various flow situations.

Design and development of a surface micro-machined push–pull-type true-time-delay phase shifter on an alumina substrate for Ka-band T/R module application

A radio frequency micro-electro-mechanical system (RF-MEMS) phase shifter based on the distributed MEMS transmission line (DMTL) concept towards maximum achievable phase shift with low actuation voltage with good figure of merit (FOM) is presented in this paper. This surface micro-machined analog DMTL phase shifter demonstrates low power consumption for implementation in a Ka-band transmit/receive (T/R) module. The push–pull-type switch has been designed and optimized with an analytical method and validated with simulation, which is the fundamental building block of the design of a true-time-delay phase shifter. Change in phase has been designed and optimized in push and pull states with reference to the up-state performance of the phase shifter. The working principle of this push–pull-type DMTL phase shifter has been comprehensively worked out. A thorough detail of the design and performance analysis of the phase shifter has been carried out with various structural parameters using commercially available simulation tools with reference to a change in phase shift and has been verified using a system level simulation. The phase shifter is fabricated on the alumina substrate, using a suspended gold bridge membrane with a surface micromachining process. Asymmetric behaviour of push–pull bridge configuration has been noted and a corresponding effect on mechanical, electrical and RF performances has been extensively investigated. It is demonstrated 114° dB−1 FOM over 0–40 GHz band, which is the highest achievable FOM from a unit cell on an alumina substrate reported so far. A complete phase shifter contributes to a continuous differential phase shift of 0°–360° over 0–40 GHz band with a minimum actuation voltage of 8.1 V which is the highest achievable phase shift with the lowest actuation voltage as per till date on the alumina substrate with good repeatability and return loss better than 11.5 dB over 0–40 GHz band.

Reconfigurable Voltage Mode Phase Shifter using Low Voltage Digitally Controlled CMOS CCII

The lo w voltage d igitally controlled current conveyors have been used to realize the d igitally controlled reconfigurable continuous time first order voltage mode phase shifters. Each of the realized phase shifters uses two digitally controlled current conveyers along with three passive elements. The realized phase shifters provide dig ital control to phase angle through an n-bit digital control word. The realized digitally controlled continuous time phase shifters are designed and verified using PSPICE and the results thus obtained justify the theory.

A CMOS Voltage Controlled Continuous Phase Shifter With Active Loss Compensation

A voltage controlled RF linear phase shifter (VPS) on CMOS process is proposed and developed to address insertion loss variation over a control range, linearity of phase control, and the size of implementation. A new compensation method for a transmission line phase shifter is introduced. By compensating loss associated with lumped elements in a transmission line, the measured CMOS VPS achieves minimum 2.8 dB insertion loss and ±0.6 dB insertion loss variation over 120° phase shift at 1.95 GHz, consuming 4 mA from 1.8 V supply. The size of the phase shifter is 850 μm × 440 μm without pads. The measured input P1dB of the design is higher than 4 dBm. To the best of author's knowledge, the demonstrated phase shifter achieves one of the best performances published in a CMOS process without using active inductors.

Reflective terahertz tunable polarization controller

This paper proposes an optical device which can continuously change the polarization state of terahertz (THz) waves. The device consists of metal gate, anti-reflection coatings, liquid crystal and mirror. By changing the refractive index of liquid crystal in the interface between the metal gate and the mirror, the phase difference between two beams with orthogonal polarization is varied and a continuous phase shift is achieved. The phase shift of the device is calculated by using the finite difference time domain (FDTD) method, and the transmittance and reflectance are calculated by using the rigorous coupled wave analysis (RCWA) method. The results reveal that the structure can realize continuously tunable phase shift for THz wave at 1 THz.

NON LINEAR OPTIMIZATION TECHNIQUE FOR THE REDUCTION OF THE FREQUENCY SCANNING EFFECT IN A PHASED ARRAY BASED ON BROADBAND INJECTION-LOCKED THIRD HARMONIC SELF-OSCILLATING MIXERS

In this work, an electronically tunable large range phase shifter based on a broadband Injection-Locked Third Harmonic Self- Oscillating Mixer (IL3HSOM) is designed and analyzed. This multi- functional circuit generates a down-converted Intermediate Frequency (IF) signal and provides a theoretical 540 - continuous phase shift range. The conversion gain and the bandwidth of the circuit are optimized through bifurcation control techniques. The IL3HSOM will be used as the core of a broadband phased antenna array with electronic beam-steering capabilities. The use of a multi-harmonic load based on an arbitrarily width modulated transmission line allows the nonlinear optimization of the circuit phase shift frequency response to compensate the frequency scanning efiect, which negatively in∞uences the performance of broadband antenna arrays.

A modulation scheme for 100 Gb/s modified minimum-shift keying format based on imbalanced bias in IQ components

We propose a modified minimum-shift keying (MSK) modulation scheme by applying the imbalanced bias on the in-phase and quadrature components of a MZM-based MSK modulator. This scheme enables constant envelope and continuous temporal phase shift of 100 Gb/s optical MSK signal by driving the MZMs with traditional sinusoidal signal instead of triangle signal. The principle of generating the optical MSK signal by this imbalanced scheme is presented. Theoretical analysis is given to modulated spectra, BER performance, residual dispersion tolerance and SPM tolerance. It is demonstrated that compared to the existing solutions the proposed scheme is able to decrease 2 dB receiver power penalty and improve SPM tolerance by 2 dB.