J. Varis

A 20-50 GHz RF MEMS single-stub impedance tuner

A novel radio-frequency (RF) microelectromechanical system (MEMS) single-stub impedance tuner has been developed. The design is based on combining the loaded line technique with the single-stub topology to obtain wide impedance coverage with high |/spl Gamma//sub MAX/|. The tuner consist of ten switched MEMS capacitors producing 1024(2/sup 10/) different impedances. The design has been optimized for noise parameter and load-pull measurements of active devices and shows excellent measured impedance coverage over the 20-50 GHz frequency range.

A reconfigurable 6-20 GHz RF MEMS impedance tuner

A 6-20 GHz reconfigurable triple-stub impedance tuner has been developed. It is based on a 11-switched MEMS capacitor network producing 2/sup 11/ different impedances. The measured and simulated impedance coverage is the widest ever measured to-date from any RF MEMS tuner. This network is most suitable for noise parameters and load-pull measurements of transistors at 6-20 GHz.

Switched Beam Antenna Based on RF MEMS SPDT Switch on Quartz Substrate

This letter demonstrates a 20-GHz radio frequency microelectromechanical system (RF MEMS)-based electrically switchable antenna on a quartz substrate. Two quasi-Yagi antenna elements are monolithically integrated with a single-pole double-throw (SPDT) MEMS switch router network on a 21 mm times 8 mm chip. Electrical beam steering between two opposite directions is achieved using capacitive MEMS SPDT switches in the router. Port impedance and radiation patterns are studied numerically and experimentally. Measured results show that the switched beam antenna features a 27% impedance bandwidth (S11 = -10 dB), a gain of 4.6 dBi, and a front-to-back ratio of 14 dB at 20 GHz when the control voltage is applied to one of the switch pairs of the SPDT switch.

W-band RF MEMS double and triple-stub impedance tuners

Reconfigurable integrated impedance tuners have been developed for W-band on-wafer noise parameter and load-pull measurement applications. The impedance tuners are based on double and triple-stub topologies and employ 11 switched MEMS capacitors producing 2048 (2/sup 11/) different impedances. Measured |/spl Gamma//sub MAX/| for the double-stub tuner is 0.92 and 0.82 at 75 and 100 GHz from 110 measurements out of 2048 possible impedances, and 0.92 and 0.83 for the triple-stub tuner. To our knowledge, this represents the first W-band integrated impedance tuner to date.

RF MEMS based impedance matching networks for tunable multi-band microwave low noise amplifiers

In this paper, we present different types of reconfigurable RF MEMS based matching networks intended for frequency-agile (multi-band) LNAs. Measured results of 2-bits matching networks show a centre frequency tuning range of 2–3 GHz (10–13%) around 20 GHz and 1.5–2.0 dB of minimum losses. Simulated tunable LNA results based on measured data of the RF MEMS matching networks show the possibilities of achieving similar high gain, good matching and low NF over the whole tuning range. The results demonstrate the potential of using RF MEMS switches for the realization of tunable LNAs at microwave and millimetre-wave frequencies.

Ka-band RF MEMS phase shifters for energy starved millimetre-wave radar sensors

Low-loss millimetre-wave RF MEMS phase shifters made on quartz are assessed with respect to a Ka-band low-power multifunctional radar sensor application. A loaded line type of phase shifter circuit presents a phase shift of 22.3° and a loss of 0.4 dB at 35 GHz. A switched line phase shifter gives 187° of phase shift and 1.5 dB of loss at 30 GHz (i.e. a FoM=122°/dB). We estimate that a 5-bit loaded line/switched line MEMS phase shifter circuit can achieve a loss of 4 dB at 35 GHz which could reduce by a factor 2 the required transmit DC power level in a Ka-Band energy starved phased array radar system.

Technology for millimetre wave radiometers

Technology for millimetre wave radiometers is discussed. Distinction between coherent and incoherent detection is also addressed. As an example, details of the 70 GHz ultra low noise and high stability receivers for the European Space Agency (ESA) Planck Mission is given. These receivers are part of the Low Frequency Instrument (LFI). The LFI receivers will make use of Monolithic Microwave Integrated Circuits (MMIC) and the key components are the Low-Noise Amplifiers (LNA). Indium Phosphide (InP) technology has been used for manufacturing the HEMT and PIN diode MMICs. Recently complete Elegant Breadboard Model (EBB) of LFI 70 GHz receivers have demonstrated a 30 K noise temperature with 16 GHz bandwidth and a 1/f knee frequency of 30 mHz. Described radiometer modules form flexible basis for constructing radiometers with many pixels for millimetre wave imaging and remote sensing applications.

Self-actuation tests of ohmic contact and capacitive RFMEMS switches for wideband RF power limiter circuits

This paper presents an experimental study on the high power handling capabilities of some ohmic contact based and capacitive RF-MEMS switches (incl. self-actuation tests made up to 18 GHz). Such tests carried out on a series and shunt connected ohmic contact COTS MEMS switch show that self-actuation occurred at 29-37 dBm of RF input power (Pin) given a DC bias (Vbias) of 42-47 V. Corresponding high power tests of a capacitive MEMS switch made on quartz (at 4 GHz) show that self-actuation occurred at Pin = 24-31 dBm with Vbias = 0-19 V. The experimental results further indicate a potential usefulness of employing ohmic contact and capacitive MEMS switches to realize optimised low-loss wideband power limiter circuits.

RF MEMS impedance tuners for 6–24 GHz applications: Research Articles

The new generation of System-on-Chip (SoC) incorporates digital, analogue, RF/microwave and mixed-signal components. Such circuits impose to reconsider the traditional design methods. Mixed-signal designers need novel design methodologies which will have to include accurate behavioral libraries of devices and processes into hierarchical design flows. Thus, this paper describes a behavioral modeling approach which generates neuro-fuzzy-based models for RF/microwave devices. The models, so obtained, can be easily integrated into a VHDL-AMS simulator. This modeling approach is applied to a microwave tunable phase shifter and it is illustrated by the development of a VHDL-AMS model library for RF/microwave applications.

Wideband cryogenic on-wafer measurements at 20-295 K and 50-110 GHz

A measurement system has been developed for cryogenic on-wafer characterization at 50-110 GHz. The measurement system allows onwafer S-parameter measurements of active and passive devices at this frequency range. The S-parameters of active devices can be measured as function of frequency, temperature, and bias conditions. As an example of cryogenic on-wafer measurements, measured S-parameters of InP HEMTs are presented at temperatures of 20, 80, 160, and 295 K and in the frequency range of 50 -110 GHz.