Widening of Operational Temperature Range of Microwave Ferroelectric Tunable Devices

The ways to solve a problem of providing stable operation of microwave ferroelectric phase shifters for steerable antennas in a wide temperature range are briefly considered. A ferroelectric phase shifter based on cascaded tunable ferroelectric planar capacitors is properly described. The connection of the tunable capacitors in series with transmission line sections allows obtaining a voltage tunable phase shift, which practically does not depend on temperature in the range 250–350 K. Such phase shifters can find a wide application in phased-array antennas.     

A Tunable Active Phase Shifter Using a Thin Film Ferroelectric Capacitor

This paper describes an active phase shifter with a large amount of variable phase. We propose a design that has second-order all-pass network characteristics and that uses a tunable ferroelectric capacitor. The transmitted phase is changed by varying the capacitance of a ferroelectric capacitor. A computer simulation is presented that shows that the network, even with markedly non-ideal transistors, can provide a true all-pass response over the frequency band of interest (100 MHz–400 MHz). These simulated results demonstrate an analog tunability of about 200° with a gain variation of about 3 dB at 300 MHz—when using a Ba_0.96Ca_0.04Ti_0.84Zr_0.16O₃ (BCTZ) capacitor with a tunability of 2:1. The simulation performed at 300 MHz because the physical layout of the real life circuit will be done mostly with the discrete components. As the self resonance frequency of most of the discrete components lies in the few hundreds of MHz range, our preferred frequency is a practical one to deal with. The simulation also predicts a flat band gain of approximately 10 dB with ± 2 dB of gain ripple.     

DESIGN,FABRICATION AND MATERIAL PROPERTIES OF TEMPERATURE STABLE PERFORMANCE CONSISTENT TUNABLE DEVICES

ABSTRACT

The premier candidate active material for tunable microwave phase shifter devices is single composition, paraelectric BaSrTiO₃ (BST). However, there is concern that in practical applications the device performance will be compromised due to the temperature dependence of the BST based device capacitance. We report a device design which controls the magnitude and the sign of the temperature coefficient of capacitance (TCC) via a multilayer paraelectric BST/buffer layer/ferroelectric BST coplanar device structure. To realize this multilayer device structure we have designed, fabricated, and optimized a 10 mol% Al doped Ta₂O₅ barrier layer with low loss (tan δ = 0.004), moderate permittivity (?_r = 42.8), low TCC (?20 ppm/°C), and a low bias stability of capacitance (0.4%). The thin film integration of the barrier layer with the BST layers was optimized for structure, microstructure, interfacial/surface morphology, and dielectric properties as a function of Al doping concentration, annealing temperature, material growth and integration process parameters.     

Optimum Reflection-Type Phase Shifter Using (Ba,Sr)TiO3 Thin Film

In this paper, in order to obtain a large differential phase shift with a little change in applied voltage, a ferroelectric reflective load circuit has been designed on top of barium strontium titanate (Ba,Sr)TiO₃ [BST] thin film. The design of the ferroelectric reflection-type phase shifter is based on a reflection theory of terminating circuit, which has a reflection-type analogue phase shifter with two ports terminated in symmetric phase-controllable reflective networks. To achieve large amounts of phase shift in low bias-voltage range, the effects of change of capacitance and transmission line connected with two coupled ports of a 3-dB 90° branch-line hybrid coupler have been investigated. A large phase shift with a small capacitance change in the parallel terminating circuit has been demonstrated in the paper.     

Epitaxial Ba0.5Sr0.5TiO3 thin films for microwave phase shifters

Abstract

A tunable phase shifter was fabricated with epitaxial Ba_0.5Sr_0.5TiO₃ (BST) thin film and gold coplanar waveguide. BST thin film of the thickness ～0.5 μm was deposited by laser ablation on the MgO(OOl) single crystalline substrate. Gold electrode of the thickness ～2 μm was prepared by the sequence of thermal evaporation, electroplating, and wet etching. Epitaxial quality of the BST thin film was confirmed by X-ray diffraction. The microwave performance of phase shifter was measured at room temperature in the frequency range of 8–12 GHz, and with applied bias voltage of up to 30 V. Effect of Mn dopant in the epitaxial films was also considered.     

Microwave Properties of Mn Doped (Ba1 - x,Srx)TiO3Thin Films for Tunable Phase Shifter

Ferroelectric Mn doped Ba_0.5Sr_0.5TiO₃ (Mn-BST) films with/without BaTiO₃ (BT) buffer layer have been grown on (001) MgO substrates by a pulsed laser deposition to investigate electrical tunability at microwave frequencies. Structural properties and surface morphologies of the films were investigated using an X-ray diffractometer and a scanning electron microscope, respectively. Microwave dielectric properties of Mn-BST thin films with BT buffer were studied for reduction of dielectric loss and improvement of electrical tunability. Distributed analog phase shifters have been designed and fabricated on Mn-BST films with/without BT buffer layer to understand microwave dielectric properties. The differential phase shift of the phase shifter fabricated on Mn-BST film was 22° at 10 GHz with 80 V of applied dc bias voltage. In comparison, phase shifter fabricated on Mn-BST/BT multilayers exhibit 41° of differential phase shift at the same condition. This suggests that a BT buffer layer is for microwave tunable device applications. The phase shifter fabricated on Mn-BST/BT multilayers exhibit a low insertion loss (S₂₁) of ?1.1 dB, and a low return loss (S₁₁) of ?14 dB with a bias voltage of 80 V.     

一款高精度90°移相器实用电路的设计

用RC元件及相应电路设计低频固定频率90°±Δφ移相器是人们常用的方案,然而RC移相器元件的老化、环境(尤其是温度)的变化严重地影响了移相器的稳定性。本文采用了一系列措施:(1)选用低温度系数的精密阻容元件;(2)对阻容元件进行老化处理;(3)分别测量元件的温度系数;(4)用相反温度系数的阻容元件按一定的比例进行补偿等,使RC元件温度系数达到±1ppm/℃以内。对90°±Δφ移相器的温度试验表明,电路的温度系数达到2.88ppm/℃。文中还给出所选用的部分国内外RC元件实测的温度系数,对读者利用RC元件设计某些高稳定性电路(如HPF、BPF、LPF等)有重要的参考价值。     

Theoretical Estimation of Achievable Figure of Merit of Microwave Ferroelectric Phase Shifters

The goal of this paper is estimation of an achievable figure of merit of microwave phase shifters. The microwave dissipation in ferroelectric material, conducting electrodes of ferroelectric components and the loss in an external circuitry are taken into account. Equations for a theoretical estimation of an achievable value of the phase shifter figure of merit have been derived and used for simulations. It has been shown that the achievable figure of merit is at least three times as high as the figure of merit of practically realized microwave phase shifters described in literature.     

Microwave Tunable Components and Subsystems Based on Ferroelectrics: Physics and Principles of Design

The most promising microwave ferroelecric device is a ferroelectric phase shifter, aimed to be an element of a phased-array antenna. The following characteristics of the phase shifter are important: microwave insertion loss, range of operational temperatures, life time. Designing microwave tunable components is based on carefully developed models of ferroelectrics and appropriate software of the circuit design. The quality of a phase shifter is determined by the figure of merit ( F ) defined as a ratio phase shift/insertion loss and measured in deg/dB. For competitive applications one needs F = 200-300 deg/dB. An extended temperature range of operation is urgently required. There are the following ways of improvement of the ferroelectric phase shifters: i) utilizing an appropriate chemical compound of ferroelectric material, ii) developing the structure of the device, for example, the film with a variable composition factor, iii) application of the digital mode of operation.     

Microwave Performance of Distributed Analog Phase Shifter Using Ferroelectric (Ba,Sr)TiO3 Thin Films

This work presents the design, fabrication and microwave performance of distributed analog phase shifter (DAPS) fabricated on (Ba,Sr)TiO₃ (BST) thin films for X-band applications. Ferroelectric BST thin films were deposited on MgO substrates by pulsed laser deposition. The DAPS consists of high impedance coplanar waveguide (CPW) and periodically loaded tunable BST interdigitated capacitors (IDC). In order to reduce the insertion loss of DAPS and to remove the alteration of unloaded CPW properties according to an applied dc bias voltage, BST layer under transmission lines were removed by photolithography and RF-ion milling. The measured results are in good agreement with the simulated results at the frequencies of interest. The measured differential phase shift based on BST thin films was 24° and the insertion loss decreased from ?1.1 dB to ?0.7 dB with increasing the bias voltage from 0 to 40 V at 10 GHz.     

Microwave slot transmission lines based on ferroelectric films tunable through low bias voltage

The modifications of microwave slot transmission lines formed on the (Ba,Sr)TiO₃ ferroelectric films were investigated to realize high quality factor millimeter-wavelength devices tunable by low bias voltages. The narrow inner electrodes inserted to a slot line form the novel type of the transmission lines, which was called multislot line (MSL). The MSL short-circuited and tunable resonators were tested at frequency ∼30 GHz. The MSL phase shifter merit factor was evaluated higher than 100 degree/dB at bias voltage lower 100 V. The comparatively high quality factors of tunable MSL resonators and phase shifters evidence on real prospects of novel topology approach to the development of such microwave devices as tunable band-pass filters and electronically steerable antennas.     

Coplanar Waveguide Using Ferroelectric Thin Oxide Film: Dielectric Constant

Coplanar waveguide (CPW) transmission lines were fabricated on thin ferroelectric Ba_{1 – x}Sr_xTiO₃ films for tunable microwave applications. The growth of the ferroelectric oxide films was accomplished by a pulsed laser deposition with a partial oxygen background. Microwave properties of the CPW phase shifter were measured using a HP 8510C vector network analyzer from 0.045–20 GHz with –40–40 V of dc bias. A large phase shift angle of 120 at 10 GHz was observed from the CPW (gap = 4m, length = 3 mm) with a 40 V of dc bias change. The dielectric constant of the thin ferroelectric film was extracted from the dimension of the CPW (gap, width, length) and the measured S-parameter by a modified conformal mapping. However, the dielectric constant of the ferroelectric thin film exhibits a gap dependency; dielectric constant (990–830) decreases with increasing gap size (4–19 m, respectively). By adjusting the filling factors of the film, a constant dielectric constant of BST film is found to be 810 ± 5.     

A series‐coupled LC quadrature oscillator using phase/amplitude calibration

In this paper, an analytic approach for the estimation of the phase and amplitude error in series coupled LC quadrature oscillator (SC‐QO) is proposed. The analysis results show that imbalances in source voltage of coupling transistor because of mismatches between LC tanks are the main source of the phase and amplitude error in this oscillator. For compensation of the phase and amplitude error, a phase and amplitude‐tunable series coupled quadrature oscillator is designed in this paper. A phase shift generation circuit, designed using an added coupling transistor, can control the coupling transistor source voltage. The phase and amplitude error can simply be controlled and removed by tuning the phase shifter, while this correction does not have undesirable impact on phase noise. In fact, the proposed SC‐QO generates a phase shift in the output current, which reduces the resonator phase shift (RPS) and improves phase noise. The phase and amplitude tunable SC‐QO is able to correct the phase error up to ±12°, while amplitude imbalances are reduced as well. To evaluate the proposed analysis, a 4.5‐GHz CMOS SC‐QO is simulated using the practical 0.18‐μm TSMC CMOS technology with a current consumption of 2 mA at 1.8‐V supply voltage. Copyright © 2016 John Wiley & Sons, Ltd.     

Low-loss 7-bit S-band CMOS passive phase shifter with digital control

This paper presents the design and implementation of a 7-bit S-band digital passive phase shifter using Complementary Metal-Oxide-Semiconductor (CMOS) 65-nm technology in 2.6- to 3.2-GHz frequency band. New switched delay network topology has been used for 5.625° and 2.8°, and modified switched filter topology has been used for implementation of other phase bits to achieve 7-bit performance with low insertion loss and better isolation. The measured results of the fabricated chip show 7-bit performance with an average insertion loss of 11 dB, average root mean square (RMS) phase error of less than 2.0°, average RMS amplitude error of less than 0.6 dB, input matching (S₁₁) better than −7.5 dB, and output matching (S₂₂) better than −14.5 dB across the target frequency band at 50Ω input/output impedance.     

铁氧体行波移相-馈电一体化网络的设计与分析

提出了在波导铁氧体移相器传输方向上加载定向耦合开槽以实现移相馈电一体化网络的设计思路.网络以铁氧体移相器实现对信号的相位控制,在铁氧体传输方向上加载多个耦合能力不同的定向耦合开槽以实现对信号的幅度控制.分析了该结构的设计原理,利用HFSS仿真软件对该结构进行仿真分析,并依据计算结果设计制作了样品,样品实测性能与理论计算较为吻合.     

移相器自动测试系统

移相器是相控阵雷达中用于实现波束移相功能的基本电路.本文描述移相器自动测试系统的原理和组成,着重介绍了测试夹具、控制电路、驱动和测试软件设计等关键技术.经过实际应用证明,该测试系统通用性好,自动化程度高,很容易实现移相器的自动测试需求,为移相器的研制和验收提供了极好的测试手段.     

一种新型的六位数字移相器的设计

针对传统的数字移相器插入损耗高和相位精度低等性能的不足,提出了一种新型的加匹配线的开关式移相器设计技术。包括固定长λ/2主线以及在主线边缘长λ/8的平行短路和开路短截线,克服了传统数字移相器设计中端口驻波比高,插入损耗大的缺点,而且在相位精度上也有提高。在设计中,用加匹配线的方法对45°,90°和180°移相器进行设计,并将相位为5.625°,11.25°,22.5°,45°,90°及180°6个二态移相器电路组合起来,构成六位数字式移相器,通过二进制代码控制各个PIN二极管,从而得到64个相移状态,实现了输出频率范围为400～450MHz的低插入损耗,高相移精度的六位数字移相器,通过实际测试得到整个六位数字移相器插入损耗低于5.3dB,相移精度小于3°,驻波比小于1.5的较好实验结果,具有比传统设计方法更优良性能。     

360°低插损小型化反射式移相器设计

针对第5代移动通信大规模多输入多输出(massive MIMO)和无线回传系统中移相阵列的应用需求,本文对反射式移相器(RTPS)的模型拓扑进行了对比分析,提出了四元件双可调(FEDA)负载拓扑的设计方法和相位变换的调整方式,研究了移相步进和插入损耗的影响因素,采用数字变容管(DTC)进行RTPS的调谐设计。实验结果表明,在4.4～5.0 GHz全频段范围内实测移相范围大于360°,移相步进小于12°,插入损耗小于1.8 dB,尺寸仅为10 mm×8 mm,兼具低插损、小型化、大带宽、高精度、易控制等优点。     

Commutation Quality Factor as a Working Tool for Optimization of Microwave Ferroelectric Devices

The commutation quality factor (CQF) is suggested as a generalized criterion of the material tunability and its loss factor. The figure of merit of a switchable device is uniquely determined by the CQF. From this point of view the CQF is used as a working tool for optimization of the microwave devices. A comparison between analog and digital ferroelectric phase shifter was performed using the CQF as a criterion. Theoretically was predicted that a digital phase shifter based on lumped tunable ferroelectric capacitors can be designed with minimal achievable insertion loss. As an example, the 180 reflection type phase shifter is discussed.     

基于移相器统一特性和高阶Taylor级数展开技术的暂态稳定计算方法

根据移相器的共同性质,对暂态稳定计算中的移相器作了统一处理,得出了移相器支路对网络节点导纳矩阵 影响的统一形式。将此形式与高阶Taylor级数展开技术相结合,形成了能灵 活统一地处理各种移相器并具 有快速计算能力的暂态稳定计算方法。