Phase Shifter Structure Research Articles

Frequency down-conversion system with image rejection using thin film lithium niobate parallel modulation phase-shifting structure

The frequency down-conversion system based on microwave photonics has been widely employed in radar, electronic warfare, and satellite communication systems. In this paper, we propose an image rejection frequency down-conversion system, wherein the phase modulator and phase shifter are integrated on thin film lithium niobate platform. The working principle is elucidated through the establishment of a theoretical model. Subsequently, the system successfully down-converts a 40 GHz radio frequency (RF) signal to a 5 GHz intermediate frequency signal, achieving an image rejection ratio of approximately 30 dB. Simultaneously, varying degrees of image rejection are observed for different RF signals. The system maintains robust image rejection performance across varying RF and image signal power, as well as different levels of input optical power.

Evaluating the Polarimetric Radio Occultation Technique Using NEXRAD Weather Radars

Currently, it remains a challenge to effectively monitor areas experiencing intense precipitation and the associated atmospheric conditions on a global scale. This challenge arises due to the limitations on both active and passive remote sensing methods. Apart from the lack of observations in remote areas, the quality of some observations deteriorates when heavy precipitation is present, making it difficult to obtain highly accurate measurements of the thermodynamic parameters driving these weather events. However, there is a promising solution in the form of the Global Navigation Satellite System (GNSS) Polarimetric Radio Occultation (PRO) technique. This approach provides a way to assess the large-scale bulk-hydrometeor characteristics of regions with heavy precipitation and the meteorological conditions associated with them. PRO offers vertical profiles of atmospheric variables, including temperature, pressure, water vapor pressure, and information about hydrometeors, all in a single fine-vertical resolution observation. To continue validating the PRO technique, we make use of polarimetric weather data from Next Generation Weather Radars (NEXRAD), focusing on comparing specific differential phase shift (Kdp) structures to PRO observable differential phase shift (ΔΦ). We have seen that PAZ and NEXRAD exhibit a good agreement on the vertical structure of the observable ΔΦ and that their combination could be useful for enhancing our understanding of the microphysics underlying heavy precipitation events.

Ultra-compact quasi-true time delay for boosting wireless channel capacity.

Massive-data connectivity has driven the need for efficient, directed communications through beamforming arrays1-10. Delay elements are critical in any beamforming signal chain. However, these elements impose fundamental limits on size, channel capacity, power efficiency and effective isotropic radiated power11. Although passive phase shifters do not consume DC power, they suffer from narrow bandwidth, poor phase resolution and low power-handling capacity. They introduce a beam squint, in which different frequency components experience different time delays, blurring signals so that they cannot be resolved. This severely limits the data rate of the wireless link, that is, its channel capacity. Although true time delay (TTD) elements12 solve this problem and service a broad bandwidth, they comprise wavelength-scale transmission lines, making them prohibitively area-inefficient for modern semiconductor processes. Here we address this long-standing problem by introducing a quasi-true time delay (Q-TTD) that miniaturizes TTD elements and breaks fundamental channel-capacity limits of these wireless links. We demonstrate this mechanism for a microwave device implemented in a complementary metal-oxide-semiconductor (CMOS) technology. Key to shrinking the footprint is a reflective-type phase-shifting structure with 3D variable TTD reflectors within a sub-wavelength footprint. This achieves ultra-broadband phase tuning by using them to vary the length of the waveguide's path to ground. They produce a delay-to-area ratio that yields a substantially higher on-chip channel capacity compared with existing state-of-the-art methods. This component, when integrated in arrays, enables high-resolution imaging and low-squint beamforming for wideband communication, on-chip radar and other applications.

Multiplexed terahertz multifocal metalens based on stretchable single-, dual-, and quad-axis synthetic rectangular optical sparse aperture

As ultrathin optical elements with subwavelength structures densely arranged, planar lens or called metalens can effectively focus incident wave. Due to the compact design and wide operating frequency of metalens, it becomes promising in applications like information encryption, imaging, and wireless communication fields. However, the fabrication of large-aperture metalens is still time-consuming and costly while the focusing performances are commonly tuned by introducing active materials requiring extra stimuli, such as laser and electrical pulses. In this study, five designs of metalenses with synthetic rectangular aperture are proposed and demonstrated with excellent focusing performances. By reconfiguring the synthetic aperture, focusing properties like focusing lengths, full width at half maximum values, and modulation transfer function can be tuned with great flexibility. With a polarization-dependent phase-shifting structure, the proposed metalens shows different focusing performances with incident wave under transverse magnetic field and transverse electric field modes. By utilizing spatial multiplexing, terahertz variable foci metalenses based on a stretchable single-, dual- and quad-axis synthetic rectangular optical sparse aperture are investigated to achieve tunable multifocal performances. These designs provide a novel strategy that can reconfigure the synthetic aperture with stretchable substrate to make metalens with multifunction and active tunability, which show promising applications in imaging, information encryption, and space telescope areas.

Development of seven MOS transistors, one capacitor based efficient and compact novel structure of phase-shifter

In this paper, a novel electronically tunable first-order voltage-mode phase-shifter is introduced, which employs seven metal-oxide semiconductor transistors and one capacitor. The attractive features of the proposed electronically tunable first-order voltage-mode phase-shifter are the low number of metal-oxide semiconductor transistors, free from additional current sources, electronic tunable, free from passive component matching conditions, high input impedance, low operating voltage, and availability of both inverting all-pass and non-inverting all-pass responses within the same structure. The theoretical analysis of the proposed circuit is tested by Cadence PSPICE Simulation software with ±0.9 V supply voltages. Pre- and post-layout verification are also explored using the Cadence VIRTUOSO simulation tool and 0.18 µm Generic Process Design Kit (gpdk) technology to confirm the real-time performance of the proposed design.

Aperture-Coupled Beam-Scanning Patch Array With Parasitic Elements Using a Reconfigurable Series-Fed Phase-Shifting Structure

In this letter, we propose a reconfigurable series-fed phase-shifting structure with movable metal plate for active millimeter wave beam-scanning application. The proposed phase-shifting structure can be equivalent to a certain number of phase shifters in the series-fed network. It can be easily controlled with only one metal plate, which further simplify the design of control system for phase shifters and reduce the cost. A prototype of 1-D aperture-coupled patch array with parasitic elements at 28GHz is designed, fabricated and measured for verifying the performance of the proposed phase-shifting structure. The measurement results at 28 GHz show 1-D beam-steering capability with maximum steering angle of ∼22 deg at H-plane can be achieved, revealing great potentials for developing the simple control and cost-effective active phased array for millimeter wave wireless power transmission application.

Asymptotic analysis of the time-periodic Kuramoto system on general symmetric coupling and phase shift structures

We consider the asymptotic behavior of the solution to the time-periodic Kuramoto system with general symmetric coupling and phase shifts. To cover all symmetric couplings, we employ a new framework that consists of the maximal diameter of phase difference estimates and the ℓ2-upper bound of mean-centered variables. Using this framework, we show the existence of a time-periodic solution to the corresponding mean-centered model for time-periodic coefficients. We also provide a sufficient condition for stability: the phase differences of the two solutions to the time-periodic Kuramoto system converge to the same state despite phase shifts and lack of all-to-all coupling. Combining these properties, we prove that the phase difference of the time-periodic Kuramoto model with general symmetric coupling and phase shifts converges exponentially to the time-periodic state. We present some numerical simulations to validate our theoretical results.

Application of Phase-Shifting Transformer with Longitudinal and Transverse Voltage Regulation

This article was written to present a new solution for a phase-shifting transformer and to show that, in many aspects, the proposed device is more functional and improved when compared to the other currently available phase-shifting structures. The article shows the construction of the new phase-shifting transformer, with longitudinal and transverse voltage regulation. The proposed device’s functionality and available operation states are compared to other existing solutions. Selected steady-state variants of the operation of the proposed transformer were checked based on computer simulations and the laboratory model presented in detail in the article. Convergence between measurements and simulations was achieved. Power flow calculations were also performed in the five-node electrical power system model. In these calculations, two variants of the proposed device’s work were considered and compared with the asymmetric phase shifter. The tests confirmed in the proposed structure, both angle and voltage regulation, enabled maintaining a constant active power flow. The authors show that the proposed solution combines the advantages and functionality of various types of phase shifters while, at the same time, being characterized by a much simpler structure, which results in a two-times-lower cost of the device.

A wideband accurate compact 6‐bit phase shifter in 0.15‐μm GaAs technology

AbstractA Ku wideband accurate compact 6‐bit digital phase shifter is designed in this letter using three different switched phase shift structures: the switched L/C structure, T‐type structure, and high‐pass/low‐pass network. To improve the bandwidth and the gain flatness, an improved switched L/C structure is used and the systematic cascade sequence of the phase shifter is optimized. The improved switched L/C structure solves the problem that conventional L/C networks are hypersensitive to the coupling capacitance at high‐frequency input. As a result, the improved L/C structure can achieve wideband and better s‐parameters. The proposed 6‐bit switched phase shifter is implemented in 0.15‐μm GaAs pHEMT process. The measured root‐mean‐square (rms) phase error is less than 2.8° at 12–18 GHz, and the average insertion loss (IL) is 6.5–6.9 dB. The chip size of the proposed 6‐bit digital phase shifter is 3.1 × 1 mm2, including all RF and dc pads, which is very suitable for radar systems.

The Design of a Low-Loss, Fast-Response, Metal Thermo-Optic Phase Shifter Based on Coupled-Mode Theory

A thermo-optic phase shifter is of great importance in silicon photonics. However, it is difficult to simultaneously achieve a good performance in insertion loss and in response speed by using traditional thermal tuning through a metallic heater. In this paper, based on coupled-mode theory, we propose a method to place high-loss materials close to the optical waveguide while maintaining the low loss of the optical device, which ensures the low insertion loss (~0.78 dB) of the phase shifter. Additionally, thanks to the very short distance between the rib waveguide and the chromium (Cr) heater, the phase shifter exhibits a high response speed (1.15 μs in rise time and 2.18 μs in decay time) with a measured bandwidth (BW) of 186 kHz. Moreover, we further optimize the structure of phase shifters, leading to the reduction of π-shift power consumption from 25.1 mW to 13.6 mW. Our proposed phase shifters have great potential in large-scale silicon photonic integrated circuits.

A Millimeter-Wave Substrate Integrated Waveguide H-Plane Horn Antenna With Enhanced Gain and Efficiency

A modified substrate integrated waveguide (SIW) H-plane horn antenna with enhanced gain and efficiency is proposed. The design features a multilayer hollow-core printed circuit board with integrated power-dividing and phase-shifting structures that simultaneously achieves low dielectric loss within the antenna and a refined field distribution over the radiating aperture. The antenna gain is further improved by loading a dipole array at the opening aperture of the SIW horn. Within an impedance bandwidth of 15.5%, the proposed antenna achieves a gain of up to 12.5 dBi, a radiation efficiency of 90%, and an aperture efficiency of 510%. Attractive merits including enhanced gain, high efficiency, and broad bandwidth make the proposed design a promising candidate for millimeter-wave (mmW) applications.

Microring Optical Phase-Shifters With Low Driving-Voltage, Low Insertion Loss, and Small Residual Amplitude Modulation

Novel microring based optical phase-shifters on Si-photonic platforms for microwave photonic applications are demonstrated. By using an add-drop microring structure in combination with an additional multimode interferometer (MMI), pure phase modulation with an ultrahigh modulation efficiency can be realized. Comparison is made to the reference all-pass ring design with both the same radius (5 μm) and coupling coefficient (κ: ∼0.2). The demonstrated structure minimizes the residual amplitude modulation (0.9 vs. 1.8 dB) for nearly 2π phase shifting over a wide optical window (1520 to 1570 nm) at the expense of a larger insertion loss (0.06 dB) due to the additional MMI. The demonstrated phase shifter structure is implemented in a Mach-Zehnder interferometer (MZI) for further study of its dynamic and linearity performance. Under forward bias, it exhibits a low V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">π</sub> /I <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">π</sub> (0.4 V/12.7 mA), fast rise-time (3 ns), low insertion loss (0.2 dB), low residue-amplitude-modulations (<0.9 dB), and can cover wide optical windows (1560–1568 nm) with a small footprint (37 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$ \times $</tex-math></inline-formula> 37 μm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> ). The measured spurious-free dynamic range (SFDR: 70–75 dB) of our novel phase shifter-based MZI is comparable to that of the traditional traveling-wave MZI (∼75 dB) under reverse bias and tested using the same setup.

Rethinking Figure-of-Merits of Liquid Crystals Shielded Coplanar Waveguide Phase Shifters at 60 GHz

The demand for reconfigurable millimetre-wave (mm-Wave) components based on highly anisotropic liquid crystals (LC) is higher than ever before for the UK and worldwide. In this work, 60 GHz investigation on a bespoke shielded coplanar waveguide (SCPW) phase shifter structure filled with 16 types of microwave-enabled nematic LCs respectively indicates that the patterns of the device’s figure-of-merit (FoM, defined as the ratio of maximum differential phase shift to maximum insertion loss) reshuffle from those of the characterised LC materials’ FoM (defined as the ratio of tunability to maximum dissipation factor). To be more specific, GT7-29001- and MDA-03-2838-based phase shifters exhibit the highest FoM for devices, outperforming phase shifters based on GT5-28004 and TUD-566 with the highest FoM for materials. Such a mismatch between the device’s FoM and LC’s FoM implies a nonlinearly perturbed wave-occupied volume ratio effect. Furthermore, the relationship between insertion loss and the effective delay line length is nonlinear, as evidenced by measurement results of two phase shifters (0–π and 0–2π, respectively). Such nonlinearities complicate the established FoM metrics and potentially lead to a renewed interest in the selection and material synthesis of LCs to optimise reconfigurable mmWave devices, and promote their technological exploitation in phased array systems targeting demanding applications such as inter-satellite links and satellite internet.

Wideband 1 bit Reconfigurable Transmitarray Antenna Based on Polarization Rotation Element

In this letter, a broadband 1 bit reconfigurable transmitarray antenna (RTA) based on polarization rotation element is proposed. The transmitarray element is composed of two split circular rings connected by two narrow strips and sandwiched by two orthogonal polarizers. As phase shift and polarization conversion structure, the two patches are separated by the air layer, and the p-i-n diodes are soldered in the center of the narrow strips. The polarizer grids are used as dc bias lines to conduct p-i-n diodes. By controlling the p-i-n diodes in the <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">on</small> and <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">off</small> states, the polarization orientation of the wave emitted by the RTA element is changed. Then, the outgoing waves in the two states physically form a broadband 180° phase difference, which broadens the operating bandwidth of the RTA effectively. By utilizing the novel unit cell, a 16 × 16 elements RTA is designed, fabricated, and measured. The measured results show that the 3 dB and 1 dB gain bandwidths are 45% and 17%, respectively. The peak gain is 16.8 dBi with aperture efficiency of 18.4%. Furthermore, the proposed RTA has good beam scanning performance with 2-D scanning range of ±40°.

High Bandwidth Capacitance Efficient Silicon MOS Modulator

This article analysed and optimised horizontal Silicon insulator Silicon capacitor (H-SISCAP) phase shifter structures with insulator thickness tox up to 40 nm. The phase shifter has an effective capacitance ( C eff) around 0.5 fF/μm and a phase change efficiency 1.8 V ·cm, of which the balance between capacitance and phase efficiency is comparable with silicon rib waveguide based depletion type phase shifters. Silicon Mach–Zehnder interferometer (MZI) modulators with 200 μm long H-SISCAP phase shifters optimised for TM polarised light have been fabricated and demonstrated with a 3 dB EO bandwidth above 35 GHz and intrinsic H-SISCAP RC bandwidth around 150 GHz. The modulator displays open eye-diagrams for data rates up to 60 Gbit/s without detection equalization and 72 Gbit/s with 2 taps equalization in NRZ-OOK operation. The demonstrated H-SISCAP phase shifter paves the way to build high bandwidth segmented, travelling wave and compact ring resonators modulators for applications of optical transmitters, microwave generations, and LIDAR applications, etc.

Efficient coupling to slow light in a silicon slot waveguide with internal corrugations

We modeled, simulated and experimentally observed efficient slow light coupling to internally corrugated slot Bragg grating (ICSBG) waveguide on a silicon-on-insulator platform. A short step taper is utilized to evanescently couple to the slow light mode near the stopband edge, resulting in minimization of Fabry–Perot reflections due to group index mismatch and a minimum slow light coupling enhancement of ∼1 dB. This is important as it results in a lower insertion loss ICSBG waveguide, which is capable of low loss slow light propagation and therefore is an attractive option as a phase shifter structure for an on-chip slow light enhanced electro-optic modulator or integrated optic sensor applications.

Analogue beamforming solution for beam‐alignment problem

Analogue only beamforming generally refers to a structure of analogue phase shifters that have no control over the amplitude of the signals and are utilised in millimetre-wave massive multi-input multi-output systems to reduce the cost and power consumption. Conventional analogue only beamforming methods are based on beam-training and subspace sampling where the transmitter and receiver select the best beamformer and combiner from a list of predefined beam patterns to maximise the beamforming gain. In this study, first, the beam-alignment problem is formulated as a quadratic optimisation problem with quadratic constraints. Then, a practical solution for analogue only beamforming is proposed to maximise beamforming gain. The proposed method has no assumption on the array structure or isotropic antenna elements in the array. Also, a new method is proposed to design sub-codebooks to reduce the construction time of the codebook. Simulation results also corroborate the analytical results and performance of the proposed method.

Modeling of beam hardening effects in a dual-phase X-ray grating interferometer for quantitative dark-field imaging.

X-ray grating interferometry (XGI) can provide access to unresolved sub-pixel information by utilizing the so-called dark-field or visibility reduction contrast. A recently developed variant of conventional XGI named dual-phase grating interferometer, based only on phase-shifting structures, has allowed for straightforward micro-structural investigations over multiple length scales with conventional X-ray sources. Nonetheless, the theoretical framework of the image formation for the dark-field signal has not been fully developed yet, thus hindering the quantification of unresolved micro-structures. In this work, we expand the current theoretical formulation of dual-phase grating interferometers taking into account polychromatic sources and beam hardening effects. We propose a model that considers the contribution of beam hardening to the visibility reduction and accounts for it. Finally, the method is applied to previously acquired and new experimental data showing that discrimination between actual micro-structures and beam hardening effects can be achieved.

Novel design for differential phase shifter structure by using multi‐section coupled lines

In this Letter, a new wideband differential phase shifter is proposed by using a multi-section coupled line structure. S-parameter circuit equations and design parameters are calculated using even/odd mode and transmission line analysis techniques for a set of phase shifters (from 0 to 90 with a step of 10°) of the proposed device. The proposed form is the first work that adds multi-section structures on the coupled line to provide any desired phase shift to the same reference line. In addition, for specific applications such as hyperthermia, the beamforming is ensured to be at small angle steps (10°) to focus the signal to the correct spot. The device is modelled with full-wave electromagnetic simulator Computer Simulation Technology (CST). Ten prototypes of differential phase shifters are designed, manufactured, and tested for the accuracy of simulation results. The simulated and measured results are in good agreement with the theory and show a bandwidth of 20.4%, 1 dB insertion loss across the 2.2–2.7 GHz frequency range.

Polarization Agile Antenna for Underwater Communication Using Integrated Power Divider and Phase Shifter

This paper presents a polarization agile antenna design that can be helpful for underwater communication, using the integrated structure of power divider and phase shifter to feed a square patch antenna. The purpose of this research is to discover new ways of communication by developing a polarization agile antenna, integrated feeding structure that can generate two equal-amplitude signals with fast phase switching between $$90^{\circ }$$ and $$270^{\circ }$$ , realizing the agility control for the dual circular polarization of the square patch antenna. Compared with the traditional polarization-agile antennas with the individual power divider and phase shifter networks, the proposed design has the advantages of good amplitude, phase and polarization imbalance performances, a simple control circuit, low insertion loss, and compact design which proves it to be best underwater communication.