L. Pradell

FET noise-parameter determination using a novel technique based on 50-/spl Omega/ noise-figure measurements

A novel method for measuring the four noise parameters of a field-effect transistor (FET) is presented. It is based on the determination of its intrinsic noise matrix elements [C/sub 11//sup INT/, C/sub 22//sup INT/, Re(C/sub 12//sup INT/), Im(C/sub 12//sup INT/)] by fitting the measured device noise figure for a matched source reflection coefficient (F/sub 50/) at a number of frequency points, thus, a tuner is not required. In contrast to previous works, no restrictive assumptions are made on the intrinsic noise sources. The receiver full-noise calibration is easily performed by using a set of coaxial and on-wafer standards that are commonly available in a microwave laboratory, thus, an expensive broad-band tuner is not required for calibration either. On-wafer experimental verification up to 26 GHz is presented and a comparison with other F/sub 50/-based and tuner-based methods is given. As an application, the dependence of the FET intrinsic noise sources as a function of the bias drain-current and gate-length is obtained.

Electrothermally Actuated RF MEMS Switches Suspended on a Low-Resistivity Substrate

This paper presents an electrothermally actuated lateral resistive-contact switch for application to low-gigahertz-band communication systems. It was manufactured on a standard low-resistivity substrate, and its RF performance was improved by suspending the structures 25 ¿m from the substrate, which is a strategy for future integration with active devices in the system-on-chip concept. Measured insertion losses are -0.26 dB at 1 GHz and -0.65 dB at 6 GHz, return losses are -29 dB at 1 GHz and -25 dB at 6 GHz, and isolations are -52 dB at 1 GHz and -26 dB at 6 GHz. The device is driven by a metal electrothermal actuator, which achieves large displacements and contact forces at much lower temperatures than traditional polysilicon electrothermal actuators. The RF power handling characteristics are also addressed and measured.

Extended tuning range RF MEMS variable capacitors using electrostatic and electrothermal actuators

In recent years, much efforts have been dedicated to the development of variable RF capacitors, a device which can take a clear benefit of MEMS technology. The most widely designed variable MEMS capacitors have an electrostatic force as actuation principle. This implies a limitation in the controlled tuning range due to the pull-in effect. In this paper we study and design three solutions in order to improve the controlled tuning range of RF MEMS variable capacitors, based both on electrostatic and electrothermal actuation principles and manufactured with the PolyMUMPSTM process. Measurements of a conventional electrostatically-actuated variable capacitor are compared to measurements of three variable capacitors with extended tuning range, based on the two above mentioned actuation principles, with the main purpose of improving the pull-in limitation and assessing and comparing their behaviour and, especially, their tuning ranges. The most important advantages and disadvantages of extendended tuning range capacitors are identified and are here reported and empirically characterized, focusing in device repeatability, understood as capacity deviation due to large capacity sensitivity to tuning voltage, for small gaps between electrodes, which arises from the strongly non-linear behaviour of the capacity vs the gap between electrodes.

RF MEMS switches based on the buckle-beam thermal actuator

In this paper, we propose series and parallel RF MEMS-switch configurations based on the buckle-beam thermal actuator. We demonstrate the feasibility of using this actuator in RF applications with processes and materials of standard microelectronics technology. The designed switches achieve simulated on-state insertion loss of 0.09 dB and off-state isolation of -19 dB @ 2 GHz. To ease the computation of the actuator displacement, we present a simple analytical model which is validated through the results obtained from simulations in CoventorWare¿ and Sugar softwares.

Characterization of dynamics and power handling of RF MEMS using vector measurement techniques

This paper proposes a new method to measure dynamics and power handling of RF microelectromechanical systems (MEMS) devices based on a mobile membrane. The method uses in-phase/quadrature demodulation of an RF signal proportional to the reflection coefficient of the measured device, which contains information of its mechanical properties, such as actuation and release times and instantaneous position of the mobile membrane. Both one-port (capacitors) and two-port devices (switches and extended tuning-range capacitors) can be measured. Its main advantage is the capability of obtaining information from both magnitude and phase variations of the device reflection coefficient to characterize its dynamics and power handling. It is shown that detecting phase is advantageous in high quality factor capacitors, where the magnitude of the reflection coefficient is nearly constant for any position of the mobile membrane. Open-short-load calibration of the system is provided in order to obtain absolute measurements, which are necessary for power-handling characterization. The performances of the proposed method are demonstrated by comparison to systems based on detection of the magnitude of the reflection coefficient. A MEMS capacitor is characterized in terms of dynamics-actuation and release times, and mechanical resonance frequency and in terms of power handling-membrane instantaneous position and phase and tuning range variation.

MEMS-Based 180

In this paper, a new uniplanar 180° phase switch suitable for space differential radiometers is proposed. It is based on two dc-contact-microelectromechanical system (MEMS) single-pole-double-throw switches that switch between two different back-to-back coplanar-to-slotline transitions. Since these transitions are multimodal structures, rigorous multimodal models are developed to analyze them and to assess the effects of the unwanted coplanar odd mode. These models are capable of predicting under what conditions the transitions produce a good wideband, 180°-phase-shift and/or matching behavior; they are applied to the design of the 180° phase switch. A compact implementation of the phase switch in the frequency range 14-20 GHz is fabricated using the FBK-irst eight-mask surface micromachining process, featuring a 180° phase-shift bandwidth of 35% for a maximum phase error of 5° and insertion loss better than 2 dB. Experimental results show a very good agreement with the multimodal model predictions. The designed dc-contact MEMS switches fulfill the typical requirements of differential radiometers, featuring measured mechanical switching and release times of 100 and 15 ¿s, respectively.

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The 30 and 44 GHz Back End Modules (BEM) for the Planck Low Frequency Instrument are broadband receivers (20% relative bandwidth) working at room temperature. The signals coming from the Front End Module are amplified, band pass filtered and finally converted to DC by a detector diode. Each receiver has two identical branches following the differential scheme of the Planck radiometers. The BEM design is based on MMIC Low Noise Amplifiers using GaAs P-HEMT devices, microstrip filters and Schottky diode detectors. Their manufacturing development has included elegant breadboard prototypes and finally qualification and flight model units. Electrical, mechanical and environmental tests were carried out for the characterization and verification of the manufactured BEMs. A description of the 30 and 44 GHz Back End Modules of Planck-LFI radiometers is given, with details of the tests done to determine their electrical and environmental performances. The electrical performances of the 30 and 44 GHz Back End Modules: frequency response, effective bandwidth, equivalent noise temperature, 1/f noise and linearity are presented.

Phase Switch for Differential Radiometers

This paper proposes a new vertical electrothermal actuator. It can be considered as a hybrid between the traditional in-plane buckle-beam actuator and the vertical hot-cold actuator. It is here referred to as vertical buckle beam. At identical dimensional and bias conditions, it features a displacement larger than that of other vertical electrothermal actuators proposed so far in the literature. The actuator performance is demonstrated by means of an analytical model along with finite-element analysis. It is applied as a driving element in parallel-plate capacitors, where it is validated and its advantages in terms of power consumption are demonstrated empirically.

LFI 30 and 44 GHz receivers Back-End Modules

In this paper, a new compact broadband uniplanar 180° phase switch, based on an air-bridged coplanar-waveguide (CPW) cross loaded with two capacitive-contact microelectromechancial systems (MEMS) switches in opposed (on/off) states, is presented. The two phase-switch states (0°/180°) are defined by actuating the MEMS switches from on/off to off/on. The asymmetry in the states of the MEMS switches results in a complex multimodal interaction between the two fundamental even and odd CPW modes at the air-bridged cross. Using the multimodal theory, the phase switch is analyzed, its frequency-in dependent 180°-phase-shift properties are proven, and a set of design equations for perfect port matching are derived. A multi modal circuit model for the phase switch is then presented, and design equations and conditions for compact phase switches are derived. Finally, a very compact phase switch is designed and fabricated using an eight-mask surface micromachining process, featuring a measured phase shift of 180° ± 1.8° in a very wide frequency range (1-30 GHz) and an insertion loss better than 2.1 dB in the design band (10-20 GHz). Experimental results are in very good agreement with electromagnetic and multimodal circuit simulations, thus validating the proposed approach and design procedure.

A Low-Power-Consumption Out-of-Plane Electrothermal Actuator

Uniplanar 180deg hybrids are basic building blocks in uniplanar technology. In this paper, a new rigorous analysis of a uniplanar 180deg magic-T hybrid based on an air-bridged coplanar cross is performed. The analysis proposed is multimodal since it takes into account the coplanar even and odd fundamental modes simultaneously. From this analysis, a complete circuit model for the hybrid is extracted, and the conditions for ideal performance are derived. This new multimodal model is necessary for the design of the hybrid, and allows a quantitative analysis of its performance, notably bandwidth, isolation, and return loss under any actual loading condition. It has been used to design and implement a 180deg hybrid on alumina with a working frequency of 15 GHz. A very good agreement between simulation and measurement is obtained. The experimental results prove a frequency-independent phase-shift behavior with a measured phase error less than plusmn 2deg.