MEMS variable‐capacitor phase shifters part I: Loaded‐line phase shifter

This article describes the design and characterization of a continuously variable loaded‐line phase shifter using micro‐electro‐mechanical system (MEMS) variable capacitors as phase shifting components. The design and characterization of micro‐electro‐mechanical system (MEMS) variable capacitors for operation at 26.5 GHz is described. A lumped‐element model is obtained from measurements and physical consideration. Experimental results show a capacitance‐tuning ratio of 3.7:1. The capacitor's characterization results are used for designing the phase shifter. A phase shift of 40.5° at 26.5 GHz for a loaded‐line type has been measured. There is good agreement between simulated and measured results. A companion article (Part II) describes the application of these variable capacitors to the design of reflection‐type phase shifters. © 2003 Wiley Periodicals, Inc. Int J RF and Microwave CAE 13: 321–337, 2003.     

A W‐band RF‐MEMS switched LNA in a 70 nm mHEMT process

This work presents a monolithic integrated reconfigurable active circuit consisting of a W‐band RF micro‐electro‐mechanical‐systems (MEMS) Dicke switch network and a wideband low‐noise amplifier (LNA) realized in a 70 nm gallium arsenide (GaAs) metamorphic high electron mobility transistor process technology. The RF‐MEMS LNA has a measured gain of 10.2–15.6 dB and 1.3–8.2 dB at 79–96 GHz when the Dicke switch is switched ON and OFF, respectively. Compared with the three‐stage LNA used in this design the measured in‐band noise figure (NF) of MEMS switched LNA is minimum 1.6 dB higher. To the authors’ knowledge, the experimental results represent a first time demonstration of a W‐band MEMS switched LNA monolithic microwave integrated circuit (MMIC) in a GaAs foundry process with a minimum NF of 5 dB. The proposed novel integration of such MEMS switched MMICs can enable more cost‐effective ways to realize high‐performance single‐chip mm‐wave reconfigurable radiometer front‐ends for space and security applications, for example. © 2015 Wiley Periodicals, Inc. Int J RF and Microwave CAE 25:639–646, 2015.     

RF MEMS,BST, and GaAs varactor system‐level response in complex modulation systems

This article presents the response of RF microelectromechanical systems (RF MEMS), barium strontium titanate (BST), and gallium arsenide (GaAs)‐based tunable filters and reconfigurable matching networks to a wideband code‐division‐multiple‐access signal centered at 1.95 GHz. The RF MEMS tunable filter and impedance tuner result in very low intermodulation distortion and spectral regrowth compared to their BST and GaAs counterparts. The linearity of the BST and GaAs tunable networks improves considerably by using a series combination of BST and GaAs varactors, but the RF MEMS‐based networks still show the best linearity of all three technologies. Also, it is shown that the reconfigurable networks, tuned with capacitive RF MEMS can handle up to 1 W of RF power with no self‐actuation. © 2007 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2008.     

MEMS capacitive series switch fabricated using PCB technology

In this article, an RF MEMS capacitive series switch fabricated using printed circuit processing techniques is discussed. Design, modeling, fabrication, and characterization of the CPW series switch are presented. An example CPW series capacitive switch with insertion loss less than 0.5 dB in the frequency range of 13–18 GHz and isolation better than 10 dB up to 18 GHz is discussed. The switch provides a minimum insertion loss of about 0.1 dB at the self‐resonance frequency of 16 GHz and a maximum isolation of about 42 dB at 1 GHz. © 2007 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2007.     

2–6 GHz GaN distributed power amplifier MMIC with tapered gate‐series/drain‐shunt capacitors

In this article, using a 0.25 μm GaN HEMT process, we present a 2–6 GHz GaN two‐stage distributed power amplifier MMIC that utilizes tapered gate series capacitors and nonuniform drain transmission lines with tapered shunt capacitors to simultaneously obtain a linear gain enhancement and optimum load line for each transistor. By using well‐derived equations to provide each transistor with the optimum load impedance and to tune the phase delay between the input and output transmission lines, the nonuniform distributed power amplifier is designed for second‐stage amplification, and satisfactory performance is demonstrated. The phase balance and tapering of the gate series capacitors have a role in improving the linear gain of the two‐stage amplifier. The measured data show a linear gain of 22 ± 1 dB, an input/output return loss of more than 15 dB, saturated output power of 41.2–43.1 dBm under a continuous‐wave mode, and a power‐added efficiency of 18–22% from 2 to 6 GHz which are very competitive values compared with previous works. © 2016 Wiley Periodicals, Inc. Int J RF and Microwave CAE 26:456–465, 2016.     

A novel DMTL capacitive switch with electrostatic actuation MAM capacitors

A novel DMTL capacitive switch with electrostatic actuation metal–air–metal (MAM) capacitors is presented. The top board of MAM capacitors will be pulled down together with the switch bridge. It has higher isolation in down-state than DMTL capacitive switch and has lower insert loss and higher self-actuation RF power comparing with MEMS shunt capacitive switch. Two of the novel DMTL capacitive switches are designed for high isolation and high self-actuation RF power, respectively. The calculated result shows that both of the two novel switches have lower insert loss than the MEMS shunt capacitive switch. The self-actuation RF power of them are 4 and 2.4 times that of MEMS shunt capacitive switch, respectively, at the cost of ?6.23 and ?3.54?dB reduction in isolation (30?GHz).     

A broadband quasi‐Yagi array of rectangular loops on LTCC

In this article, a broadband quasi‐Yagi array of rectangular loops using low‐temperature co‐fired ceramic technology is proposed. The antenna is fed by a simple and compact microstrip‐to‐coplanar strip transition, which serves as balun and impedance transformer simultaneously. Four rectangular loops are used to direct the antenna propagation toward the end‐fire direction. Compared with the planar directors in traditional quasi‐Yagi antenna, they can provide better director effect to improve the radiation performance. Furthermore, they act as good impedance matching elements to broaden the bandwidth. The measured results show that the proposed antenna achieves a wide bandwidth of 42% for S₁₁ < ?10 dB (from 26.1 to 40 GHz), better than 12 dB front‐to‐back ratio, smaller than 14 dB cross polarization and an average gain over 6.5 dBi across the operating bandwidth. The antenna occupies a compact size of 8 × 8 × 1 mm³. © 2013 Wiley Periodicals, Inc. Int J RF and Microwave CAE 24:196–203, 2014.     

A compact asymmetric slot dual band antenna fed by CPW for PCS and UWB applications

A compact slot antenna with an overall dimension of 30 × 30 × 1.6 mm³ is proposed for dual band applications. The radiating element is a hexagonal shape patch which protrudes from a Co‐Planar Waveguide (CPW) feed into a step shape slot. The slot is basically rectangular in shape and is extended by inserting rectangular cuts of different sizes on the ground plane around it. The ultrawide impedance bandwidth is achieved using asymmetric feed line along with extended rectangular cuts around the slot. For realizing the second band for personal communication system applications (near 1.9 GHz), a metallic stub of quarter wave length is attached at the top of the slot. The measured impedance bandwidth (for S₁₁ < ?10 dB) is 110 MHz (1.86–1.97 GHz) for the first band and 9 GHz (3.0–12.0 GHz) for the second band. The antenna is further characterized by omnidirectional radiation patterns in the H‐plane, dumb‐bell shape radiation patterns in the E‐plane and a peak gain of 3–5 dBi over the ultrawideband. All the measured results are found to be in good agreement with the simulated results. © 2014 Wiley Periodicals, Inc. Int J RF and Microwave CAE 25:243–254, 2015.     

Design and optimization of RF ICs with embedded linear macromodels of multiport MEMS devices

In this paper, we demonstrate efficient modeling approach for simulation, analysis, design, and optimization of multiport radio frequency microelectromechanical systems (RF MEMS) resonating structures embedded in RF circuits. An in‐house finite element method (FEM) solver is utilized to develop accurate and efficient macromodels that capture all the essential characteristics of the device. Using the datasets generated from the FEM simulations, the artificial neural network models are trained for two‐way mapping between the physical input and electrical output parameters. Realized model is implemented in a circuit simulator, enabling a simple yet accurate circuit simulator compatible modeling and optimization procedure instead of memory and time demanding FEM analysis. The derivation of dynamic macromodels with preserved electromechanical behavior of the multiport resonating structures is also presented. Capabilities of the proposed approach are demonstrated with several examples featuring capacitively actuated MEMS resonating structures: a clamped–clamped beam, a free–free beam, and a coupled clamped–clamped beam. © 2007 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2007.     

Multiple-output MEMS DC/DC converter: a system modeling study

DC/DC converters are widely used in consumer electronic devices where usually a single power source is available while the electronic board of the device requires different voltage levels in order to power-up different block functions. In this paper we present the design of a MEMS single-input multi-output voltage level shifter. The low-voltage to high-voltage conversion is based on the electrostatic transduction of variable capacitors built using interdigitated comb fingers. A 1?mm² MEMS prototype has been designed and fabricated using the SOIMUMPs process. In this study we present the co-design and co-simulation of the whole system (the MEMS device and its dedicated charge-pump-circuit) in a single EDA environment through MEMS+ (a Coventorware^? tool that allows the co-simulation of MEMS and electronics in the Cadence Analog Design Environment). We present analytical, FEM and MEMS+ models of the multi-output DC–DC converter and show that all our models converge towards the experimental results.     

MEMS variable‐capacitor phase shifters part II: Reflection‐type phase shifters

A novel design procedure for reflection‐type phase shifters using capacitive devices is developed. Using this approach, a phase shifter for operation at 26.5 GHz is developed using MEMS variable capacitors reported in Part I of this article. A design optimization procedure is discussed. Design of a CPW hybrid at 26.5 GHz (as needed for this phase shifter) is also discussed. Experimental results validate the design procedure and yield a phase shift of 179.30° at 26.5 GHz. © 2003 Wiley Periodicals, Inc. Int J RF and Microwave CAE 13: 415–425, 2003.     

Inductively‐loaded RF MEMS reconfigurable filters

This article presents an inductively loaded radio frequency (RF) microelectromechanical systems (MEMS) reconfigurable filter with spurious suppression implemented using packaged metal‐contact switches. Both simulation and measurement results show a two‐state, two‐pole 5% filter with a tuning range of 17% from 1.06 GHz to 1.23 GHz, an insertion loss of 1.56–2.28 dB and return loss better than 13 dB over the tuning range. The spurious passband response in both states is suppressed below ?20 dB. The unloaded Q of the filter changes from 127 to 75 as the filter is tuned from 1.06 GHz to 1.23 GHz. The design and full‐wave simulation of a two‐bit RF MEMS tunable filter with inductively loaded resonators and monolithic metal‐contact MEMS switches is also presented to prove the capability of applying the inductive‐loading technique to multibit reconfigurable filters. The simulation results for a two‐bit reconfigurable filter show 2.5 times improvement in the tuning range compared with the two‐state reconfigurable filter due to lower parasitics associated with monolithic metal‐contact MEMS switches in the filter structure. © 2009 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2009.     

Modeling of gold microbeams as strain and pressure sensors for characterizing MEMS packages

This work presents the modeling of gold microbeams for characterizing Micro-electro-mechanical systems (MEMS) packages in terms of both strains induced to the MEMS devices and hermetic sealing capability. The proposed test structures are based on arrays of rectangular-shaped clamped-free and clamped–clamped beams, to be realized with a film of electroplated gold by surface micromachining technology. The resonant frequency of the microbeams is modeled by FEM simulations as a function of substrate deformations, which could be induced by the package. Clamped–clamped bridges show a linear change of the square of the resonant frequency in case of in-plane deformations, in fairly good agreement with an approximate analytical model. Cantilever beams are modeled as variable capacitors to detect out-of-plane deformations. Finally, an analytical model to study cantilever beams as resonators for detecting pressure changes is discussed and compared with preliminary experimental results, showing an impact on the quality factor in a range from 10^?2 mbar to 1?bar.     

MEMS based humidity sensor using Si cantilever beam for harsh environmental conditions

The RF applications like voltage controlled oscillators, tunable filters, resonators etc., requires tunable capacitors in their designs. This paper presents the design of wide range MEMS tunable capacitors for RF applications. This design consists of an air suspended bottom plate and a fixed top plate. The top fixed plate and the suspended bottom plate form the tunable capacitor. The capacitance range of this tunable capacitor is from 69.172 to 138.344 nF. This range is wider compared with the conventional MEMS tunable capacitors of tuning ranges in pico Farads. The fabrication process is similar to that of the existing standard integrated circuit fabrication processes, which makes this design suitable for integrated RF applications.     

A high gain tree‐shaped array antenna designed by competitive algorithm of simulating natural tree growth

This article presents a novel 16‐element array antenna designed by Competitive Algorithm of Simulating Natural Tree Growth. The array antenna has an impedance bandwidth ranging from 5.5 to 6.2 GHz for S₁₁ 相似文献   

Improved planar Marchand balun using a patterned ground plane

In this article, a novel planar Marchand balun using a patterned ground plane is presented. This new design has a slot under the coupled lines cut on the ground plane so that the even‐mode impedance can be increased substantially. Meanwhile, we propose that two additional separated rectangular conductors be placed under the coupled lines in order to act as two capacitors, so that the odd‐mode impedance will be decreased. The design theory and procedure for optimizing the Marchand balun are presented. As an example, one Marchand balun on a double‐sided PCB is designed, simulated, fabricated, and measured. The measured return loss is found to be better than ?10 dB over the frequency band from 1.2 to 3.3 GHz, or around 100% bandwidth. The measured amplitude and phase imbalance between the two balanced output ports are within 1 dB and 4°, respectively, over the operating frequency band. © 2005 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2005.     

Design of active inductors in SiGe/SiGe:C processes for RF applications

Applicability of silicon‐based heterojunction bipolar processes is investigated for designing active inductors with high quality factors (Q). Results for grounded type one‐port active inductor incorporating frequency‐dependent as well as frequency‐independent negative resistances are examined. Later, the negative resistance aspect is extended from one‐port to two‐port active inductor circuit to ensure its use as a series element. The enhanced Q‐values of all the inductive circuits are observed in accordance with the theory. Moderately high‐Q values (～100) with considerable inductances (～0.2–1 nH) are obtained in the RF frequency ranges (～5–9 GHz). © 2007 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2007.     

Theoretical facet and experimental results of harmonic tuned PAs

High‐efficiency power amplifier design criteria imply a synthesis of input and output networks with particular emphasis on their harmonic behavior. In this article, a simplified approach to clarify the relevance of such terminations is presented. Starting from the implications of power balance for stage performance, design criteria to improve the efficiency of high‐frequency applications are presented. In order to validate the approach, comparisons among the performances of single‐stage amplifiers, all operated at 5 GHz under a sinusoidal driving signal and synthesized by utilizing different design methodologies, are presented. Drain efficiencies at 1‐dB compression of 44.5%, 53.3%, and 61.56% have been measured respectively for the tuned load and harmonically manipulated (2^nd and 2^nd & 3^rd) realized amplifiers, compared with a simulated drain efficiency of 55% using the Class E approach. © 2003 Wiley Periodicals, Inc. Int J RF and Microwave CAE 13: 459–472, 2003.     

Design of wide range MEMS tunable capacitor for RF applications

The RF applications like voltage controlled oscillators, tunable filters, resonators etc., requires tunable capacitors in their designs. This paper presents the design of wide range MEMS tunable capacitors for RF applications. This design consists of an air suspended bottom plate and a fixed top plate. The top fixed plate and the suspended bottom plate form the tunable capacitor. The capacitance range of this tunable capacitor is from 69.172 to 138.344?nF. This range is wider compared with the conventional MEMS tunable capacitors of tuning ranges in pico Farads. The fabrication process is similar to that of the existing standard integrated circuit fabrication processes, which makes this design suitable for integrated RF applications.     

An eclectic approach to design tunable amplifiers

Broadband amplifiers that can accommodate commercial communication standards such as GSM, UMTS, Wi‐Fi, and Wi‐Max are extremely important for radio equipment manufacturers. To achieve this coverage, the amplifier should provide high gain and efficiency over a band from 800 to 5200 MHz. Although there are transistor devices that have cut‐off frequencies well over these frequencies, amplifiers covering such a broad‐bandwidth are difficult to design due to the requirement of broadband matching networks. In this work, design of broadband tunable matching networks is investigated using Real Frequency Direct Computational Technique (RF‐DCT). In order to be able to work on sample structures, impedance transforming filters are chosen and a broadband tunable matching network has been designed. Implementation of tunable inductors is investigated and the performance of a tunable matching network using tunable inductors and capacitors is demonstrated. Eventually a broadband frequency tunable amplifier has been designed using the tunable inductor concept. © 2013 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2013.