Improved Ferroelectric Phase Shifter by Inserting Spiral Inductors into Ground

In this paper we developed a ferroelectric CPW phase shifters which will be integrated with wideband CTS antenna array. For fabrication of the ferroelectric CPW, the vacuum sputter has been used with a optimized sputtering parameters. The experimental RF performances of the developed phase shifters were compared with those from simulations using WIPL-D software. The results showed that while the approach of using thin Ferroelectric films may be successful in designing low cost tunable coplanar waveguide phase shifters, the amount of achievable phase shifts are small (less that 10°) unless Ferroelectric compatable substrates such as STO are used (phase shifts are 27°). Good agreement was also observed between simulations and measured results and this provides high confidence in the developed fabrication process‥ While our group has been successful in fabricating thin film ferroelectric phase shifter, work is still underway to help develop multilayer ferroelectric phase shifters as well as on the development of an integrated CTS and ferroelectric phased antenna array. As a next step, our group is now pursuing fabrication of a ferroelectric multilayer CPW integrated with the CTS antenna array.

Recent advances in the development of Barium Strontium Titanate ferroelectric composition has made possible reasonable performance of ferroeletric phase shifters to frequencies up to 10 GHz. These material improvements, coupled with phase shifter circuit design changes have resulted in phase shifts greater than 360 degrees with less than 6 dB insertion loss. In particular additives to the BaxSr1-xTiO3 composition have been shown to exhibit a consistent electrical phase shift verses DC potential over parameters of temperature and humidity. These ferroelectric material improvements and circuit design changes, included with the development of multiple ferroelectric phase shifters makes possible the fabrication of a low cost electronic scanning antenna. A single four element phase shifter was used with a one dimensional linear antenna array which was constructed on three layers and used an aperture coupled distribution technique. Individual elements of this multiple four element phase shifter were evaluated with respect to uniformity phase shift and insertion loss. The four element antenna was fed by four ferroelectric phase shifters and the phase shifters are corporately fed by the microwave source. The ferroelectric phase shifters are controlled via a dedicated microcontroller which calibrates out element phase variations and provides a real time scan capability for the antenna assembly.

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.

Today's phased-array antennas use hundreds of radiating elements that use relatively high-loss phase shifters that operate over a limited bandwidth. The number of elements and the phase shifter losses affect the overall cost of the antenna system. Ferroelectric RF phase shifters have the potential to meet the low-loss, low-cost requirements driving many phased-array applications. Some of the issues affecting the development of ferroelectric phase shifters include ferroelectric tunability, dielectric losses, conductor losses, and impedance mismatch. We used the measured tunability (250 kHz, room temperature), dielectric constant, and loss tangent (10 GHz, room temperature) of Ba1-xSrx/TiO3 (0.4x 0.6) with various amounts of MgO additive, 0 to 60 wt.%, to estimate the device performance of microstrip phase shifters. The electromagnetic model of the microstrip (which uses a standard 3-mil-wide 1-oz. copper line, 3-mil-thick BST/MgO composite and the bias criteria of 2 V/μm) has produced performance benchmarks for a number of composites providing 360° of phase shift. While the accuracy of the electromagnetic model used to evaluate these materials has limitations, the results do provide some insight as to which materials may be better suited for 10-GHz phase shift devices.

A reflection type phase shifter based on a tunable ferroelectric capacitor is under consideration. A design and characteristics of the one-bit ferroelectric phase shifter is proposed and discussed. The minimal insertion loss of the phase shifter is limited by the commutation quality factor of the capacitor and can be achieved in the case when the losses of the phase shifter in both states have the same value. The layout of the phase shifter based on a coplanar waveguide structure is shown. Measured characteristics of the phase shifter are compared with the predicted ones.

A tunable capacitor based on a ferroelectric thin film grown on a dielectric substrate is a promising component for reconfigurable and tunable devices for numerous RF and microwave applications such as phase shifters, tunable filters, and tunable matching networks. The goal of this paper is characterization of the insertion loss in a reflection-type microwave phase shifter based on the ferroelectric tunable capacitor. The reflection-type phase shifter based on ferroelectric planar tunable capacitor was designed, manufactured, and tested. Its simulated and measured insertion loss and phase shift are compared. Two loss mechanisms in the phase shifter were distinguished: the loss in the tunable capacitor and the loss in the associated circuitry (metallization and substrate). The properly organized investigations of the dissipation of energy in metallization and dielectric substrate can result in a sufficient improvement of the quality of the devices. As a final result, one may anticipate that the figure-of-merit of a ferroelectric tunable or switchable phase shifter can reach 200 deg/dB

A novel distributed digital MEMS (micro-electro-mechanical system) microwave phase shifter, fabricated with bulk Si micromachining techniques, is presented. Using a distributed nonlinear transmission line technique, with single crystal silicon based multilayer microbridge structures as loading varactors, this phase shifter delivers true time delay and wideband performance. A micromachining process flow, combining anodic bonding and single crystal silicon etching with heavy boron doping, was developed to fabricate the movable Si-based microbridges over a coplanar waveguide (CPW). An electrostatic voltage, applied between the Si layer of the microbridges (varactors) and CPW ground plane, pulls down the microbridges, effecting a phase shift varying linearly with. frequency. The principle, process and RF performance characterization are described. The actuated phase shifter has achieved 90.2/spl deg/ phase shift at 20.5 GHz, with good reflection loss (-12 dB) in the frequency range of 5-20.5 GHz. The insertion loss is a little high, 3.87 dB, however, due to the lossy substrate of Pyrex 7740 glass and the thin metalization of the CPW.

The analysis, construction, and performance of compact surface wave ferroelectric phase shifters suitable for operation in the100-to1000-MC frequency range are described. Although this ferroelectric loaded parallel-plane structure is a very low impedance structure, a satisfactory terminal impedance matching technique has been devised. Kilovolt level voltages are needed; but since the current required to maintain or rapidly shift phase is low, the over-all control power requirements are at least an order of magnitude less than those for comparable ferrite phase shifters. One of these room temperature operable phase shifters provided 348/spl deg/ of phase shift at 207 Mc. It had an insertion loss which varied from 3.7 to 2.2 db over a zero- to 4000-volt range of applied dc control voltage.

This paper presents a two-phase interleaved critical conduction mode (CRM) power factor correction boost converter with a variation-tolerant phase shifter (VTPS), which ensures accurate 180° phase shift between the two interleaved converters. A feedback loop similar to a phase-locked loop controls the amount of the phase shifting of the VTPS. The proposed VTPS has better immunity of process, supply, and temperature variations than the conventional phase shifter. A 320-W two-phase interleaved CRM boost converter prototype has been implemented, while the proposed VTPS and conventional interleaving phase shifter can be selectively applied to compare the performance of the proposed technique with the conventional one. Experimental results show that the two-phase interleaved CRM boost converter has better performance with the proposed VTPS. The proposed VTPS circuit can be applied to any type of interleaved switching power converter.

The fifth generation (5G) network communication systems operate in the millimeter waves and are expected to provide a much higher data rate in the multi-gigabit range, which is impossible to achieve using current wireless services, including the sub-6 GHz band. In this work, we briefly review several existing designs of millimeter-wave phased arrays for 5G applications, beginning with the low-profile antenna array designs that either are fixed beam or scan the beam only in one plane. We then move on to array systems that offer two-dimensional (2D) scan capability, which is highly desirable for a majority of 5G applications. Next, in the main body of the paper, we discuss two different strategies for designing scanning arrays, both of which circumvent the use of conventional phase shifters to achieve beam scanning. We note that it is highly desirable to search for alternatives to conventional phase shifters in the millimeter-wave range because legacy phase shifters are both lossy and costly; furthermore, alternatives such as active phase shifters, which include radio frequency amplifiers, are both expensive and power-hungry. Given this backdrop, we propose two different antenna systems with potential for the desired 2D scan performance in the millimeter-wave range. The first of these is a Luneburg lens, which is excited either by a 2D waveguide array or by a microstrip patch antenna array to realize 2D scan capability. Next, for second design, we turn to phased-array designs in which the conventional phase shifter is replaced by switchable PIN diodes or varactor diodes, inserted between radiating slots in a waveguide to provide the desired phase shifts for scanning. Finally, we discuss several approaches to enhance the gain of the array by modifying the conventional array configurations. We describe novel techniques for realizing both one-dimensional (1D) and 2D scans by using a reconfigurable metasurface type of panels.

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.

An electric field controlled ferroelectric phase shifter has been developed which provides a differential phase shift of approximately 100/spl deg/ per centimeter at a frequency of 200 Mc /s. The attenuation varies from 1.1 to 1.5 db per centimeter. The phase shifter, shown in figure1, was constructed in dielectric loaded parallel plane waveguide in which the dominant TE/sub10/ surface wave mode is excited. This transmission line is inherently suited to the construction of devices requiring control by a uniform electric field. As shown in figure 1, the surface wave is launched onto and collected from the ferroelectric loaded line by means of a coaxial line feeding through the upper plate. The center conductor traverses the space between the parallel plates and contacts the lower plate. Prior analysis 2 has shown that this method of surface wave launching is extremely efficient and broadbanded when the dielectric constant (K) of the dielectric slab is very high. In addition it has been found that if the dielectric constant is very high, as it is in the case of ferroelectric materials (K>1000), then the launching efficiency is independent of the dielectric constant. Thus changes in the dielectric constant due to electric field and temperature changes do not affect the launching efficiency. It has been analytically and experimentally determined that the impedance of the ferroelectric loaded parallel plane waveguide is very low compared to the impedance of the unloaded parallel plane regions beyond the extremities of the ferroelectric slab. Hence, very little power radiates from the ends of the slab.

This paper explores the usefulness of RF MEMS and reconfigurable antennas in the context of modern communication systems and other applications. Simulation studies on a fractal antennas with switches and phase shifters provide beam steering and beam scanning characteristics. A brief description of the design aspects of two MEMS based coplanar waveguide (CPW) phase shifters for microwave and millimeter wave antenna applications are also provided here. One phase shifter design consists of a unique bilateral interdigital structure on a silicon substrate deposited with a thin film of electrically tunable barium strontium titanate. The dielectric constant of the thin film, and hence the effective permittivity of the transmission line changes by the application of a bias voltage. The second device is a distributed microelectromechanical system (MEMS) phase shifter fabricated on a high resistivity silicon substrate using microstereolithography technique is presented here. The distributed MEMS phase shifter consists of a high-impedance CPW transmission line and several MEMS bridges of uniform height. By applying a voltage the height of these bridges can be adjusted. This results in a variation in the distributed capacitance of the segment of the transmission line, which manifests in the phase shift at the output terminal. The fabrication procedure described here shows significant promise for the use of microstereolithography techniques for RF MEMS devices.

A new microwave scanning array is described which permits a precision in pointing and pattern shape heretofore unattainable in systems using ferrite phase shifters. The core of this new array is a synchronous reciprocal ferrite device which operates via a synchronously rotating magnetic field, similar to the classical alternator. This provides a continuously increasing phase shift which is linear in time to the same degree that the angular velocity of the magnetic field is constant. The latter is precisely controlled through quadrature currents in identical quadrature coils. The rate of phaseshift change is governed by the frequency of the coil currents. A uniform progressive phase shift is achieved in the array by using frequency multiples in the coils of successive phase shifters. These frequencies are precisely related through master crystals and frequency dividers. All the non-linearity difficulties of conventional ferrite phase shifters are avoided, thus eliminating costly and complex computer compensation. The scan range is adjusted by selection of the percent dead time and interelement spacing. Two-dimensional scanning is possible using a combination of frequency scan in one plane and synchronous ferrite scan in the other.

We present a polarization Linnik interference microscope with a nematic liquid-crystal (NLC) phase shifter for full-field optical coherence tomography of high-quality images. The rotating half-wave plate in conventional achromatic phase shifters was replaced by three liquid-crystal (LC) half-wave plates for implementing three-step phase-shifting interferometry. Thus, the NLC device generates phase shifts quickly and has no vibrations. In addition, the phase shift can be set to an arbitrary value between 0 and 2π by altering the azimuth angles of the LC cells. A tomographic image is retrieved from three sequential phase-shifted interferograms by using a three-step algorithm. The experimental results confirm the feasibility of the proposed technology.