Ferroelectric Phase Shifter Research Articles

Giant dielectric tunability in ferroelectric ceramics with ultralow loss by ion substitution design

Due to their responsiveness to modulation by external direct current fields, dielectric tunable materials are extensively utilized in integrated components, such as ferroelectric phase shifters. Barium strontium titanate ceramics have been considered the most potential tunable materials for a long time. However, the significant dielectric loss and high voltage drive have limited their further applications. Recently, Bi6Ti5WO22 ceramic has regained attention for its high dielectric tunability with low loss. In this study, we judiciously introduce Nb5+ with a larger ionic radius, replacing Ti4+ and W6+. This successful substitution enables the modulation of the phase transition temperature of Bi6Ti5WO22 ceramics to room temperature, resulting in superior tunable properties. Specifically, the 0.7Bi6Ti5WO22−0.3Bi6Ti4Nb2O22 ceramics exhibit giant tunability (~75.6%) with ultralow loss (<0.002) under a low electric field (1.5 kV/mm). This tunability is twice that of barium strontium titanate ceramics with a similar dielectric constant and only one-tenth of the loss. Neutron powder diffraction and transmission-electron-microscopy illustrate the nanodomains and micro-strains influenced by ion substitution. Density functional theory simulation calculations reveal the contribution of ion substitution to polarization. The research provides an ideal substitute for tunable material and a general strategy for adjusting phase transition temperature to improve dielectric properties.

Effect of the Polarization of Nanosized Barium Strontium Titanate Films on the Characteristics of Ferroelectric Microwave Phase Shifters

Effect of the Polarization of Nanosized Barium Strontium Titanate Films on the Characteristics of Ferroelectric Microwave Phase Shifters

30 GHz ferroelectric phase shifter on silicon carbide

Thin ferroelectric barium-strontium titanate (BST) films of high structure quality have been grown on semi-insulating silicon carbide substrates. The crystal structure and elemental composition of the obtained films were studied by the X-ray diffraction and Medium Energy Ions Scattering. Planar capacitors based on these BST films reveal the combination of high tunability and low losses at microwaves. 30 GHz ferroelectric phase shifter demonstrating a figure of merit of 22 deg/dB with a phase shift of Δϕ = 220 deg is implemented based on BST films on silicon carbide substrate.

Efficient multi-step coupling between Si3N4 waveguides and CMOS plasmonic ferroelectric phase shifters in the O-band.

In this paper we present a thorough simulation-based analysis for the design of multi-step couplers bridging seamlessly plasmonic barium titanate oxide (BTO) ferroelectric phase shifters and thick silicon nitride (Si3N4) waveguides for the O-band. The targeted plasmonic waveguides are a hybrid plasmonic waveguide (HPW) providing low propagation losses and a plasmonic metal-insulator-metal (MIM) slot waveguide offering a high confinement factor for high modulation efficiency. The proposed plasmonic platforms are formed by Copper (Cu) providing CMOS compatibility. The analysis is based on 2D-FD eigenvalue and 3D-FDTD numerical simulations targeting to identify the optimum geometries ensuring the lowest coupling losses, calculated as 1.75dB for the HPW geometry and 1.29dB for the MIM configuration. The corresponding confinement factors are 31.39% and 56.2% for the HPW and MIM waveguides, respectively.

Author Correction: A ferroelectric multilevel non-volatile photonic phase shifter

Author Correction: A ferroelectric multilevel non-volatile photonic phase shifter

Crystal Structure and Ferroelectric Evidence of BaZnSi3 O8 , a Low-Permittivity Microwave Dielectric Ceramic.

BaZnSi3 O8 ceramic was prepared by the conventional solid-state method and sintered at 1100 °C. XRD and synchrotron Rietveld refinement analyses revealed the BaZnSi3 O8 ceramic presented a monoclinic structure with a space group of P21 /a (No.14), which is reported for the first time. The BaZnSi3 O8 ceramic presented a weak ferroelectricity, which was confirmed by the P-E loop and the 90° nanoscale ferroelectric domain. Although ϵr -T displayed two ϵr abnormal peaks at 400 °C and 460 °C, the Curie temperature (Tc ) was located at 460 °C according to the dielectric loss and Curie-Weiss law. Moreover, the BaZnSi3 O8 ceramic exhibited optimized microwave dielectric properties with ϵr =6.55, Q×f=52400 GHz, and τf =-24.5 ppm/°C. Hence, the BaZnSi3 O8 ceramic in the ternary BaO-ZnO-SiO2 system possessed both weak ferroelectricity and microwave dielectric properties. These results are expected to break the technical barrier of ferroelectric phase shifter applications in microwave and even millimeter-wave frequency bands.

Silicon‐based on‐chip four‐channel phased‐array radar transmitter with ferroelectric thin film at 100 GHz

A silicon-based phased-array transmitter working at 100 GHz is proposed in this study. Planar array ferroelectric film phase shifters (FPSs) are realised with patch antennas, DC bias lines, microstrip lines and power dividers on a monolithic silicon substrate. The system enables full process compatibility and avoids loss caused by multichip interconnection. The isolation layer uses benzocyclobutene polymer film with low permittivity and low loss tangent, providing large thickness physical isolation. The FPS has a compact length of 0.45 mm, and simulation results show that its phase shift degree at 100 GHz is 125.7° with 3.95 dB insertion loss and 11.4 dB reflection loss. The patch antenna shows that the maximum simulated radiation gain of the single antenna is 4 dBi and the four-element antenna array is 9.7 dBi at 100 GHz. The beam can be steered to ±10°. The proposed system lays an important foundation for the realisation of silicon-based system-on-chip radar RF front-end system.

Loaded-line ferroelectric phase shifter based on Mn-doped (Ba,Sr)TiO3 thin films for Ka-band systems

This paper presents on the microwave properties of a loaded-line ferroelectric phase shifter based on (Ba, Sr)TiO3 (BST) thin films for Ka-band applications. In order to reduce the dielectric loss of the BST thin film and its enhance a dielectric tunability, we optimized the deposition of Mn-doped (Ba0.5, Sr0.5)TiO3 (Mn-BST) thin films on MgO substrates by using pulsed laser deposition (PLD). The crystallinity, microstructure and thickness of the thin films were investigated by using an X-ray diffractometer and a scanning electron microscope, respectively. We designed and fabricated a tunable ferroelectric capacitor loaded coplanar waveguide (CPW) type phase shifter to enhance the tuning and the loss characteristics of a conventional CPW ferroelectric phase shifter. The fabricated loaded-line phase shifter showed a low return loss of −15 dB in the frequency band from 25 GHz to 35 GHz. The differential phase shift was 293°, and the insertion loss decreased from −11.3 dB to −1.4 dB with increasing dc bias voltage from 0 to 80 V at 35 GHz.

Coupled microstrip line microwave phase shifter using ferroelectric thin film varactors

This article presents a coupled microstrip line microwave phase shifter using ferroelectric thin film varactors with parallel plate electrodes integrated on high-resistivity silicon substrate. This design is proposed as a component in low-cost beam scanning phased array antennas. The phase shifter structure consists of coupled microstrip line periodically loaded with eight BaxSr1-xTiO3 (BST) varactors and two planar Marchand baluns. The planar Marchand baluns work as the transformers of odd mode excitation and a transmission stop circuit for even mode excitation as well as the impedance matching networks. A differential phase shift of 45° was obtained with a low dc bias of 20 V at frequency of 9 GHz, which corresponds to a figure of merit of ∼23°/dB. These results represent significant progress toward compact size, low loss, and ferroelectric thin film-based phase shifters at room temperature.

Implementing a Piezoelectric Transformer for a Ferroelectric Phase Shifter Circuit

This paper describes the successful development of a piezoelectric transformer-based driver circuit used to bias a ferroelectric phase shifter. The proof-of-concept circuit achieves voltages in excess of 400 VDC and accomplishes 0 to 180 degrees of phase shift at Ka-band. The ferroelectric phase shifter is the fundamental component in a new type of scanning phased array, the ferroelectric reflectarray. The coplanar ferroelectric phase shifter requires only one control signal, currently generated by magnetic circuit components. However magnetic devices suffer from resistive and magnetic losses, and dimensional and economic costs. New phased array architecture, not reliant on magnetics, can be realized because the piezoelectric transformer allows a low level signal to be routed to each phase shifter and converted to the proper bias voltage levels at each phase shifter. This research explores the use of a piezoelectric transformer (PT) as the alternative enabling component in the voltage supply for a ferroelectric phase shifter utilizing piezoelectrics in an AC-DC converter.

Effect of the microwave signal power on the controllability of a ferroelectric phase shifter

We consider a microwave phase shifter based on thin-film ferroelectric parallel-plate capacitors operating as a part of a phased array at an elevated microwave power level and for a limited power in the control circuits. To eliminate capacitance modulation in parallel-plate capacitors by an ac field, we propose the separation of the effects of the dc control voltage and the ac voltage based on the symmetry of the capacitance-voltage characteristic of the unit including two capacitors parallel-connected in the ac voltage U ac and series-connected in dc voltage U dc. The experiment shows that for U dc > U ac, the phase of the wave passing through the phase shifter weakly depends on the microwave signal power. The reflection phase shifter is tested for a pulsed power of the microwave signal up to 6 W and a power in the control circuit on the order of 10 μW.

Microstructure and dielectric properties of Ba0.6Sr0.4TiO3–MgAl2O4 composite ceramics

(1−x)Ba0.6Sr0.4TiO3–xMgAl2O4(x=25, 30, 35 and 40wt%) composite ceramics were prepared by conventional solid-state reaction method. The microstructures, dielectric properties and tunability of the composites have been investigated. The XRD patterns analysis reveals two crystalline phases, a cubic perovskite structure Ba0.6Sr0.4TiO3 (BST) and a spinel structure MgAl2O4 (MA). SEM observations show that the BST grains slightly dwindle and agglomerate with increasing amounts of MA. A dielectric peak with very strong frequency dispersion is observed at higher MA content, and the Curie temperature shifts to a higher temperature with increasing MA content. The ceramic sample with 30wt% MA has the optimized properties: the dielectric constant is 1503, the dielectric loss is 0.003 at 10kHz and 25°C, the tunability is 23.63% under a dc electric field of 1.0kV/mm, which is suitable for ferroelectric phase shifter.

Improved Ferroelectric Phase Shifter by Inserting Spiral Inductors into Ground

In this paper, a method is introduced to improve the performance of ferroelectric phase shifter. The influences of periodically inserting spiral inductor into ground of coplanar waveguide (CPW) are investigated. Three dimensional electro-magnetic simulation shows that at frequency of 25 GHz, the maximal phase differential will be 449°, which is 97° more than the conventional one with no spiral inductor loaded. The novel ferroelectric phase shifter is also fabricated. Comparing with the conventional phase shifter, additional 49° phase shift is obtained at 18 GHz.

A Phased Array Antenna Using Ferroelectric CPW Phase Shifter Active Modules

A phased array antenna using ferroelectric coplanar waveguide (CPW) phase shifter active modules is presented based on a Ba0.6Sr0.4TiO3 (BST) thin film. The ferroelectric BST thin film was deposited on an MgO substrate by using pulsed laser deposition. The active module amplifies an RF signal with low noise and changes the phase of a received RF signal to control the main beam of the array antenna. It is composed of low noise amplifier (LNA), dc block, and ferroelectric CPW phase shifter. The prototype of 6×12 phased array patch antenna with the active modules using a ferroelectric phase shifter is proposed. The proposed array antenna continuously scanned its main beam in elevation plane to 32° from its broadside direction at 11.85 GHz by applying the continuous dc voltage to the ferroelectric phase shifter.

Effects of fringing capacitor on ferroelectric phase shifter

Two different devices topology are proposed to implement parallel-plate capacitors using Ba0.6Sr0.4TiO3 (BST) thin films. At 1 MHz frequency, the maximum tunability 1.3:1 is obtained with 32 V DC bias. The new topology capacitors have much higher tunability compared with conventional capacitors at the same total capacitance. Phase shifters, which are loaded variable structure capacitors have also been implemented. The circuits provide a maximum 190° and 262° phase shift at 18 GHz at room temperature.

ERROR VECTOR MEASUREMENTS OF BST COUPLED MICROSTRIPLINE PHASE SHIFTERS (CMPS) USING DIFFERENT TYPES OF MODULATION

ABSTRACT Error vector measurements (EVM) are used to investigate whether the nonlinear properties of a ferroelectric coupled microstrip phase shifter (CMPS) impact the quality of a radio frequency (RF) signal that is modulated, transmitted through the ferroelectric CMPS, and demodulated. Measurements were performed using a variety of phase shift key (PSK) and quadrature amplitude modulation (QAM) formats. At RF power levels up to +6 dBm and symbol rates up to 7 megasamples per second (Msps), we observed no degradation in EVM that could be associated with the ferroelectric phase shifter. These preliminary results are encouraging for the suitability of these devices to perform in high power, high bandwidth space communication applications.

Distributed ferroelectric phase shifter with slots periodically inserted into ground

A modified structure of a distributed ferroelectric phase shifter is presented, which is obtained by periodically inserting slots into the ground of a conventional distributed phase shifter. The principle is explained and electromagnetic simulation results are reported. It produces higher phase shift and, at the same time, matches port impedance better without reducing the width of the centre strip conductor of the coplanar waveguide, compared with the conventional structure.

Modified principle of distributed ferroelectric phase shifter considering the influence of interconnecting lines

AbstractThe deviation between theoretic values and real data of distributed ferroelectric phase shifter is investigated by simulating an ideal model and analyzing an equivalent circuit. The deviation is shown to come from the parasitic inductance of interconnecting lines between loaded capacitors and center strip of CPW, which reduces the Bragg frequency, increases the insertion loss and phase shift. By introducing an effective capacitance to consider the effect of interconnecting lines, a modified principle is presented, which forecasts performances better. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 748–751, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23212

Advances in Scanning Reflectarray Antennas Based on Ferroelectric Thin-Film Phase Shifters for Deep-Space Communications

Though there are a few examples of scanning phased array antennas that have flown successfully in space, the quest for ldquolow costrdquo high-efficiency large-aperture microwave phased arrays continues. Fixed and mobile applications that may be part of a heterogeneous exploration communication architecture will benefit from the agile (rapid) beam steering and graceful degradation afforded by phased array antennas. The reflectarray promises greater efficiency and economy compared to directly radiating varieties. Implementing a practical scanning version has proven elusive. The ferroelectric reflectarray, under development and described herein, involves phase shifters based on coupled microstrip patterned on films that were laser ablated onto substrates. These devices outperform their semiconductor counterparts from X- through and K-band frequencies. There are special issues associated with the implementation of a scanning reflectarray antenna, especially one realized with thin-film ferroelectric phase shifters. This paper will discuss these issues, which include relevance of phase shifter loss; modulo 2 effects and phase shifter transient effects on bit error rate; scattering from the ground plane; presentation of a novel hybrid ferroelectric-semiconductor phase shifter; and the effect of mild radiation exposure on phase shifter performance.

Integration of microwave phase shifter with BST varactor onto TiO 2 /Si wafer

A BST ferroelectric thin-film microwave phase shifter with interdigital capacitors on TiO 2 /Si substrate is presented. The interdigital capacitors have 230 mum signal width, 100 mum signal to ground gap, and 10 mum finger gap. The device, with phase shifts of 142deg and FoM of 107.3deg/dB applied voltage of 50 V at 16 GHz, has been realised. The TiO 2 buffer layer grown by ALD enables successful integration of BST-based microwave tunable devices with Si wafer.