Phase Shift Range Research Articles

A reconfigurable transmitarray unit cell employing liquid metal

AbstractIn this paper, a reconfigurable transmitarray unit cell using liquid metal is presented. It consists of three conducting layers where the geometries of the resonators, on the different layers, differ and consist of an arrow shape together with rotated split rings. The arrow‐shaped conducting layer has the capability to convert the polarization of the incoming waves by 90°. The split ring resonators, on the upper and lower conducting layers, have the same dimensions but different orientations (horizontal and vertical polarization). Several fluidic channels are placed beneath/above the conducting layers. The transmission behaviour of the unit cell can be changed by altering the geometrical parameters which is achieved by injecting the liquid metal into the channels. More than 300° phase shift range with a maximum S21 of ∼ −1.5 dB at 3.3 GHz is obtained. It exhibits 3 dB of insertion loss over a bandwidth ranging from 3.2 to 3.43 GHz. It is the first time that a transmitarray unit cell, reconfigured employing liquid metal, provides a combination of low insertion loss and large phase shift range. The proposed prototype was fabricated and measured within an open‐ended waveguide and the measured results agree well with the simulations and verify the effectiveness of the design. The reconfigurable transmitarray unit cell can be used to design beam‐scanning arrays, as well as for applications in wireless communications.

Ku-band 300 kW high power ferrite phase shifter.

Phase shifter (PS) is a key component of a phased array antenna (PAA) system, which controls the microwave phase and realizes the antenna beam forming and scanning. A ferrite PS (FPS) is a current-controlled PS that uses the ferrite's gyromagnetic properties to realize phase shifting. It has the advantages of short phase switching time, low microwave loss, and high reliability and, therefore, has been widely used in low-power PAA systems. However, the power handling capability of the traditional Ku-band FPS is only a few kW, prohibiting FPS from being used in high-power microwave (HPM) PAA systems. Spurred by this concern, this paper proposes a new dual-toroid FPS structure with an external magnetic excitation. By optimizing the PS configuration, improving the integration process, and enhancing the performance of ferrite materials, a single FPS in the Ku band has reached the power handling capability of more than 300 kW with an insertion loss of less than -1.2 dB, the phase shift range of 0°-360°, the width less than 11.5mm, and the ability of a one-dimensional array. The FPS has the potential to be used in the PAA of an HPM system, laying a foundation for the research of the HPM PAA system.

Optofluidic phase modulator based on electrowetting liquid lens

In this paper, a liquid optical phase modulator modified from a cylindrical two-liquid electrowetting liquid lens is presented. A movable optical plane is constructed by fixing a transparent sheet between two immiscible liquids. By using the electrowetting effect to flatten the optical plane along the through-light direction, the length ratio of the two liquids in the through-light direction can be fine-tuned to modify the optical path to realize phase modulation. To validate this concept, we experimentally fabricated a prototype phase modulator and tested its phase modulation capability. Experiments show that the phase shift range can be up to 5.82 π and the phase shift accuracy can be up to λ/60, a drive time of 72 ms and a relaxation time of 34 ms within the range of applied voltage 40–80 V DC voltage.

Low‐cost and easy‐to‐embed 7‐bit 360° phase shifter with transitions for large‐scale phased arrays

AbstractIn this letter, a low‐cost and easy‐to‐embed 7‐bit 360° phase shifter with transitions is presented for applications to beamforming in the large‐scale phased array. In the proposed 360° phase shifter, the topology of the reflection‐type phase shifter (RTPS) is employed, composed of a 3‐dB branchline coupler terminated with two tunable parallel L–C loads. First, a two‐step phase extraction process for RTPS is applied to design the RTPS rapidly with competitive performance, including 360° phase range and low insertion loss. A huge amount of parameter sweep is reduced in the design and test. Meanwhile, the parameter of inductors in the tunable loads is investigated effectively, to achieve the minimal phase step. Second, aiming at the enhanced performance of beamforming and improved flexibility of integration, the stripline is adopted in the design of the phase shifter, avoiding the interference on antenna radiation effectively. To facilitate the integration with antenna and radio frequency connectors of the input and output signals, a stripline‐to‐microstrip line transition with electromagnetic bandgap structures is adopted. By this means, the complexity and cost of fabrication are decreased. Finally, fabricated in the low‐cost printed circuit board technology, our proof‐of‐concept design operated from 2.4 to 2.5 GHz is measured and achieves a 386.8° phase shift range with an insertion loss of 2.21 ± 0.82 dB at 2.45 GHz.

Design and Implementation of Different Unit Cells for Reconfigurable Intelligent Surface

Recently, great attention has been given to the idea of a smart environment. It often involves the use of reconfigurable intelligent surfaces (RIS) for the management of electromagnetic wave reflections as the world awaits the emergence of 6G. Changeable intelligent surfaces may enhance the creation of wireless communication. The design and analysis of several unit cell reflections are presented in this work. The first design relies on the Switching Technique which involves switching on and off to acquire the phase as well as the coefficient of reflection to accommodate 6G standards. The unit cells design is configured to operate in the millimeter band and X band. In the second design, the radius of the circular patch was changed to adjustment of the phase and reflection coefficient. The use of Floquet technique is employed in investigating the scattering characteristics of a unit cell's constituent elements based on the assumption that every element consists of an extremely iterating periodic structure. To determine the optimal force reflection and the transformation phase, the return loss alongside reflection phase graphs of each resonant component were examined. The simulation results indicate that the first design exhibits a reflection phase shift range of -180 to 90 and a reflection magnitude over 0.93 at a frequency of 11GHz. In contrast, the second design demonstrates a reflection phase shift range of -135 to 135 and a reflection magnitude surpassing 0.9 at a frequency of 28GHz. The analysis and simulation of the design models were carried out using the CST model.

Design of an ultra wideband THz reflectarray antenna based on orbital angular momentum

A Reflectarray antenna (RA) that can generate orbital angular momentum vortex waves in the THz band was proposed. First of all, a reflective phase-shifting element composed of a notched double-shaped ring and a single Matal structure was designed to form a radiation patch. The reflective phase-shifting element has the advantages of good linearity, high smoothness, and a large phase shift range, which is suitable for the subsequent production of reflective array antennas. Then, the phase distribution of the reflected wave of the OAM vortex wave carrying mode l=+1、+2、+3、+4 is given, and the size of each element is determined based on the reflected phase of each element. Using the proposed element, an OAM reflectarray antenna operating within the waveguide standard WR-5 (120GHz–220GHz) is designed. The optimal frequency band for antenna operation in mode l=+1 is 150GHz–190 GHz, and the maximum gain of the reflector array antenna is 19.4 dBi, and the minimum divergence angle of the antenna array is 5.2°, which has good directivity and beam radiation ability. The spiral structure of the OAM beam space generated by the RA in this paper is clearly visible, proving that the implementation of OAM vortex waves in the THz frequency band is feasible. This design also provides a new method for generating OAM vortex waves in wireless and microwave wireless communications. The proposed RA is suitable for 6G wireless communication systems.

A Broadband Transmitarray Antenna Using a Metasurface-Based Element for Millimeter-Wave Applications.

In this manuscript, a broadband transmitarray antenna (TA) using a metasurface-based element is presented for millimeter-wave communication applications. The metasurface-based TA element adopts a receiver-transmitter configuration: metasurfaces are applied as the receiver and transmitter, and slot-coupled differentially fed striplines are used as the phase compensation. The designed TA element achieves good transmission performance with a more than 360° transmission phase shift range and less than 1-dB transmission insertion loss within a wide frequency range. To verify the proposed TA, a prototype is fabricated based on the conventional printed circuit board (PCB) process, and a pyramid horn is designed as the source. The measured results show that the proposed TA with the differential feed network presents a 1-dB gain bandwidth of 26.2% from 23.5 to 30.5 GHz and a peak gain of 24.5 dBi. The designed TA is a promising alternative for millimeter-wave communications applications because of its high gain, broad bandwidth, low costs, and convenient integration with other circuits.

Circulating power flow restricted operation of the isolated bi-directional dual-active bridge DC-DC converter for battery charging applications

This paper presents the Non-Circulating Power Flow (NCPF) enabled Dual Active Bridge (DAB) converter controller strategy. The proposed DAB controller eliminates the non-circulating power flow for all the four conventional modulation algorithms, i.e., Single Phase Shift (SPS), Extended Phase Shift (EPS), Dual Phase Shift (DPS) and Triple Phase Shift (TPS) modulation schemes. This leads to lesser current stress and power loss across the DAB converter switches due to reduced peak inverse current. The proposed controller strategy finds various applications, such as in a Solid-State Transformer (SST) enabled microgrid, or for Electric Vehicle (EV) Energy Storage Unit (ESU: battery, supercapacitor) integrations, etc. The proposed NCPF operation reduces battery (and supercapacitor) current stress by upto 71.8 %, and improves operative environment, thus fostering its health and lifecycle. In NCPF mode, if the rating of installed switches (current and voltage ratings) remains unchanged, its power transfer capability is marginally reduced by mere 10.0 %. In addition to this, the operating range (i.e., controlling range of phase shift (Φ) and modulation index (m)) remains unaffected. This paper summarizes the DAB NCPF operation in restricted power flow mode as a function of Φ and m through 3-D and 4-D graphs. Finally, working of NCPF DAB is tested via both simulation and hardware platforms. Comparative results are shown for conventional and proposed modulation schemes on hardware platform, to showcase the elimination of circulating current in both forward and reverse DAB operating modes. It is inferred that proposed controller is worthy of real-world implementations.

A 340-GHz THz Amplifier-Frequency-Multiplier Chain With 360° Phase-Shifting Range and its Phase Characterization

A 340-GHz THz Amplifier-Frequency-Multiplier Chain With 360° Phase-Shifting Range and its Phase Characterization

Direct synthesis method of wideband tunable filtering phase shifter based on complex matched transversal multiple resonances

In this article, a wideband filtering phase shifter (FPS) based on transversal multiple resonances is proposed. By utilizing transversal resonances with complex impedance, a wide operation band is achieved with compact circuit size. By doubly loading the tunable external coupling networks (ECNs) with complex impedance, the FPS obtains continuous phase tuning with stable filtering performance. In addition to the structural construction, a set of analytical formulas and guidelines for the direct synthesis of the FPS are provided, rather than tedious optimization. Finally, an FPS using transversal three resonances with complex impedance is designed, fabricated, and measured to validate the concept. The example showcases a wide 10-dB RL bandwidth of 32.5% with high selectivity, a compact size of 0.068 λg2, a phase shift range (PSR) of 105°, and a low phase error of ±5.4∘.

Inverted-E Type Phase Shifter Using Fixed Stub-Loaded Main Line: Enhanced Bandwidth and Phase Shift Range

Inverted-E Type Phase Shifter Using Fixed Stub-Loaded Main Line: Enhanced Bandwidth and Phase Shift Range

Two-frame random phase shifting interferometry based on constrained Kalman filter without pre-filtering

This paper discusses a phase estimation algorithm in two-frame phase-shifting interferometry using a constrained Kalman filter without the need of pre-filtering operation for the background intensity removal. A state-space model is developed and state estimation is performed based on the extended Kalman filter. The Kalman smoother algorithm is utilized to improve the accuracy of state estimation. A comparative study is presented between the proposed and four state-of-art phase estimation methods. Both simulation and experimental results show good accuracy and noise robustness of the proposed method over a wide range of phase shifts.

A Singly Curved Conformal Phased Array with Integrated Particles-Based CRLH Phase Shifters

In this paper, a four unit cell micron-sized magnetic particles embedded composite right/left-handed (CRLH) transmission line metamaterial phase shifter is proposed. The variable phases are achieved by activating the micron-sized magnetic particles along the length of stub transmission lines of the CRLH transmission line structure. This causes to effectively change the inductance of stub transmission lines, which changes the phase of the RF signal. These structures can be activated in a symmetric or asymmetrical manner to obtain wide range of phase shifts. A prototype of cascaded four unit cell CRLH transmission line phase shifter with embedded silver-coated ferrites (magnetic particles) is designed, fabricated and tested for phase shifters applications. The measured phase response of the proposed phase shifter is in close agreement with the simulated phase response. Next, for the performance analysis of proposed phase shifter, a 1 × 4 conformal curved-shaped phased array operating at 5.8 GHz is fed with the four unit cell cascaded phase shifter in CST full-wave simulator. The conformal phased array with proposed integrated phase shifters was simulated for broadside pattern correction and main beam scanning at 20 degree on curved-shaped surface with different bend angles. The radiation pattern results obtained with the proposed integrated phase shifters are in close agreement with those obtained with direct excitation of the array.

Wavelength switching technique for phase interrogation of Mach Zehnder interferometer-based optical sensors.

A method for determining the phase shift of a Mach Zehnder interferometer (MZI) is presented. It is based on switching the wavelength of continuous wave (CW) laser light illuminating the MZI and measuring the interferometer output amplitudes at DC and switching frequency. The method can measure the MZI phase shift unambiguously over the entire phase shift range of 2π. A practical proof of concept demonstration shows that the method can perform real-time measurement with high repeatability and accuracy limited by the optical frequency drift and power fluctuation of the lasers. The method does not require modifications of the sensor or accessing to the laser electronics and also uses simple detection. It is, therefore, suitable for bio and medical sensing applications.

Design of a 0.15-2GHz high-resolution vector-sum broadband phase shifter with controlled programmable attenuators for stochastic cooling system.

In this paper, a new 0.15-2GHz broadband phase shifter with 9-bit phase resolution is presented. This broadband digital adjustable phase shifter is implemented by utilizing the signal vector summation technology. The phase shifter consists of one 90° hybrid coupler, two digital attenuators, two 180° hybrid couplers, two microwave switches, and one combiner. By adjusting the attenuation value of the two digital attenuators, the device creates a minimum 0.7° stepped phase shift. In addition, by switching the two microwave switches, a 360° range of phase shift is achieved while almost keeping the amplitude of the phase shifter constant. The measurement results show that the proposed phase shifter achieves a phase resolution of 0.7° while exhibiting an average insertion loss of 9 ± 2 dB and phase unbalance within ±10°. The calculated RMS phase error of the broadband phase shifter is below 5° from 0.15 to 2GHz.

Demonstrating more than 2π phase modulation in non-Hermitian asymmetric multilayers

Phase modulation has come to be recognized as a fundamental paradigm for optical device design in applications involving the spatiotemporal control of optical wavefronts. Here, the cavities use a combination of absorptive and lossless layers with ideal conductive metal to control reflection and phase shift, similar to the Fabry–Pérot system, which has zero reflection and perfect transmission. Multilayers with different sequences and composed of several stack layers were examined for reflectivity when activated in a prism-coupled layout. The layer’s different arrangements, resulting in open and closed asymmetric multilayers, display reflectance spectra with distinct features as well as phase and shifts. In the open configuration, there is a strong coupling between the hybridized resonance mode and the exciton from the red dye. As a result, energy-based topological considerations identify a correlation between exciton/polariton strong coupling, topological darkness, and phase tuning, and they motivate the phase shift range.

Low terahertz frequency on-chip multi-functional modulator with amplitude and phase modulation

Terahertz amplitude and phase modulation technologies are crucial for terahertz communication, radar, and imaging. However, most current approaches can only achieve either amplitude or phase modulation. In this paper, we present a low terahertz frequency on-chip multi-functional modulator that consists of a hybrid coupler and reflection meta-structure. High-performance amplitude modulation is achieved by combining series resonant absorption of series coupling branch with resonance enhancement of parallel coupling branch in the reflection meta-structure. Meanwhile, the enhanced resonance provides a larger range of phase shifts, enabling effective amplitude and phase modulation in two different frequency regions. Therefore, we realize an amplitude modulation in the range of 115–135 GHz with a minimum transmission loss of 4 dB and a modulation depth of over 10 dB. At the same time, we achieved a continuous phase shift in the 103–113 GHz region, as well as a 180° two-bit phase shift in the 107–109 GHz range with only 5.7 dB transmission loss. Our simple method for terahertz amplitude and phase multi-functional modulation offers the potential to construe terahertz multifunctional integrated systems.

Adjustable rotation of multiple vortices produced by diode-pumped Nd:YVO4 lasers using intracavity second harmonic generation.

The criteria for achieving adjustable rotation of optical vortices are analyzed and used to design a diode-pumped solid-state laser that incorporates intracavity second harmonic generation within a concave-flat cavity to produce frequency-doubled Hermite-Gaussian (FDHG) modes. These FDHG modes are subsequently employed to generate various structured lights containing 2, 4, and 6 nested vortices using an external cylindrical mode converter. Through theoretical exploration, we propose that increasing the radius of curvature of the concave mirror and extending the cavity length can enhance the rotational angles of multiple vortices by expanding the adjustable range of phase shift for FDHG modes. Moreover, theoretical analyses assess vortex rotation concerning the positions of a nonlinear medium, successfully validating the experimental observations and elucidating the phase structures of the transformed beams.

Silicon-Organic Hybrid Electro-Optic Modulator and Microwave Photonics Signal Processing Applications.

Electro-optic modulator (EOM) is one of the key devices of high-speed optical fiber communication systems and ultra-wideband microwave photonic systems. Silicon-organic hybrid (SOH) integration platform combines the advantages of silicon photonics and organic materials, providing a high electro-optic effect and compact structure for photonic integrated devices. In this paper, we present an SOH-integrated EOM with comprehensive investigation of EOM structure design, silicon waveguide fabrication with Slot structure, on-chip poling of organic electro-optic material, and characterization of EO modulation response. The SOH-integrated EOM is measured with 3 dB bandwidth of over 50 GHz and half-wave voltage length product of 0.26 V·cm. Furthermore, we demonstrate a microwave photonics phase shifter by using the fabricated SOH-integrated dual parallel Mach-Zehnder modulator. The phase shift range of 410° is completed from 8 GHz to 26 GHz with a power consumption of less than 38 mW.

High-Efficiency Circularly Polarized Phased Array Based on 5 μm-Thick Nematic Liquid Crystals: Design, Over-The-Air Calibration, and Experimental Validation

This paper presents a systematic investigation and demonstration of a K-band circularly polarized liquid-crystal-based phased array (LCPA), including the design, over-the-air (OTA) in-array calibration, and experimental validation. The LCPA contains 16 phase-shifting radiating channels, each consisting of a circularly polarized stacked patch antenna and a liquid-crystal-based phase shifter (LCPS) based on a loaded differential line structure. Thanks to its slow-wave properties, the LCPS exhibits a maximum phase-shifting range of more than 360° with a figure of merit of 78.3(° )·dB−1 based on a liquid crystal layer with a thickness of only 5 μm. Furthermore, an automatic OTA calibration based on a state ergodic method is proposed, which enables the extraction of the phase–voltage curve of every individual LCPA channel. The proposed LCPA is manufactured and characterized with a total profile of only 1.76 mm, experimentally demonstrating a scanned circularly polarized beam from −40° to +40° with a measured peak gain of 12.5 dBic and a scanning loss of less than 2.5 dB. The bandwidth of the LCPA, which satisfies the requirements of port reflection (|S11|) < −15 dB, an axial ratio (AR) < 3 dB, beam squinting < 3°, and a gain variation < 2.2 dB, spans from 25.5 to 26.0 GHz. The total efficiency is about 34%, which represents a new state of the art. The use of the demonstrated low-profile LCPA to support circularly polarized scanning beams, along with the systematic design and calibration methodology, holds potential promise for a variety of millimeter-wave applications.