Kamran Entesari

Tuning in to RF MEMS

RF MEMS technology was initially developed as a replacement for GaAs HEMT switches and p-i-n diodes for low-loss switching networks and X-band to mm-wave phase shifters. However, we have found that its very low loss properties (high device Q), its simple microwave circuit model and zero power consumption, its high power (voltage/current) handling capabilities, and its very low distortion properties, all make it the ideal tuning device for reconfigurable filters, antennas and impedance matching networks. In fact, reconfigurable networks are currently being funded at the same level-if not higher-than RF MEMS phase shifters, and in our opinion, are much more challenging for high-Q designs.

A differential 4-bit 6.5-10-GHz RF MEMS tunable filter

This paper presents a state-of-the-art RF microelectromechanical systems wide-band miniature tunable filter designed for 6.5-10-GHz frequency range. The differential filter, fabricated on a glass substrate using digital capacitor banks and microstrip lines, results in a tuning range of 44% with very fine resolution, and return loss better than 16 dB for the whole tuning range. The relative bandwidth of the filter is 5.1 /spl plusmn/ 0.4% over the tuning range and the size of the filter is 5 mm /spl times/ 4 mm. The insertion loss is 4.1 and 5.6 dB at 9.8 and 6.5 GHz, respectively, for a 1-k/spl Omega//sq fabricated bias line. The simulations show that, for a bias line with 10-k/spl Omega//sq resistance or more, the insertion loss improves to 3 dB at 9.8 GHz and 4 dB at 6.5 GHz. The measured IIP/sub 3/ level is > 45 dBm for /spl Delta/f > 500 kHz, and the filter can handle 250 mW of RF power for hot and cold switching.

A 12-18-GHz three-pole RF MEMS tunable filter

This paper presents a state-of-the-art RF microelectromechanical systems (MEMS) wide-band tunable filter designed for the 12-18-GHz frequency range. The coplanar-waveguide filter, fabricated on a glass substrate using loaded resonators with RF MEMS capacitive switches, results in a tuning range of 40% with very fine resolution, and return loss better than 10 dB for the whole tuning range. The relative bandwidth of the filter is 5.7/spl plusmn/0.4% over the tuning range and the size of the filter is 8 mm/spl times/4 mm. The insertion loss is 5.5 and 8.2 dB at 17.8 and 12.2 GHz, respectively, for a 2-k/spl Omega//sq bias line. The loss improves to 4.5 and 6.8 dB at 17.8 and 12.2 GHz, respectively, if the bias line resistance is increased to 20 k/spl Omega//sq. The measured IIP/sub 3/ level is >37 dBm for /spl Delta/f>200 kHz. To our knowledge, this is the widest band planar tunable filter to date.

High PSR Low Drop-Out Regulator With Feed-Forward Ripple Cancellation Technique

A low drop-out (LDO) regulator with a feed-forward ripple cancellation (FFRC) technique is proposed in this paper. The FFRC-LDO achieves a high power-supply rejection (PSR) over a wide frequency range. Complete analysis and design steps of the FFRC-LDO are presented in this paper. Kelvin connection is also used to increase the gain-bandwidth of the LDO allowing for faster transient performance. The LDO is implemented in 0.13 ?m CMOS technology and achieves a PSR better than - 56 dB up to 10 MHz for load currents up to 25 mA. Load regulation of 1.2 mV for a 25 mA step is measured, and the whole LDO consumes a quiescent current of 50 ?A with a bandgap reference circuit included. To our knowledge, this is the first LDO that achieves such a high PSR up to 10 MHz.

A 1.2–1.6-GHz Substrate-Integrated-Waveguide RF MEMS Tunable Filter

This paper presents a high-performance substrate-integrated-waveguide RF microelectromechanical systems (MEMS) tunable filter for 1.2-1.6-GHz frequency range. The proposed filter is developed using packaged RF MEMS switches and utilizes a two-layer structure that effectively isolates the cavity filter from the RF MEMS switch circuitry. The two-pole filter implemented on RT/Duroid 6010LM exhibits an insertion loss of 2.2-4.1 dB and a return loss better than 15 dB for all tuning states. The relative bandwidth of the filter is 3.7 ± 0.5% over the tuning range. The measured Qu of the filter is 93-132 over the tuning range, which is the best reported Q in filters using off-the-shelf RF MEMS switches on conventional printed circuit board substrates. In addition, an upper stopband rejection better than 28 dB is obtained up to 4.0 GHz by employing low-pass filters at the bandpass filter terminals at the cost of 0.7-1.0-dB increase in the insertion loss.

A 25–75-MHz RF MEMS Tunable Filter

This paper presents a state-of-the-art discrete RF microelectromechanical systems (MEMS) tunable filter designed for 25-75-MHz operation. This paper also presents an enhanced model of the RF MEMS switch, which is used for accurate prediction of the tunable filter response. The two-pole lumped-element filter is based on digital capacitor banks with on-chip metal-contact RF MEMS switches and lumped inductors, and results in a tuning range of 3:1 with fine frequency resolution, and a return loss better than 13 dB for the entire tuning range. The relative bandwidth of the filter is 4 plusmn 1% over the tuning range and the insertion loss is 3-5 dB, limited mostly by the inductor Q and the switch loss. The IIP3 measurements prove that tunable filters with metal-contact series RF MEMS switches show extremely linear behavior (IIP3 > 68 dBm).

A CMOS Low-Noise Amplifier With Reconfigurable Input Matching Network

A reconfigurable low-noise amplifier (LNA) with tunable input matching network is proposed. The tunable input matching network provides continuous tuning of the input resonant circuit. The LNA is implemented using 0.13-mum CMOS technology. The amplifier has a tuning range of 1.9-2.4 GHz with an input return loss better than -13 dB. The LNA has a measured voltage gain of 10-14 dB and a noise figure of 3.2-3.7 dB within the band. The LNA consumes 14 mA from a 1.2-V supply. The detailed analysis of the proposed LNA, including the tuning range and additional noise of the proposed reconfigurable input matching network, is presented. To our knowledge, this is the first architecture that provides continuous tuning of the input matching network.

A 2.8-mW Sub-2-dB Noise-Figure Inductorless Wideband CMOS LNA Employing Multiple Feedback

A wideband low-noise amplifier (LNA), which is a key block in the design of broadband receivers for multiband wireless communication standards, is presented in this paper. The LNA is a fully differential common-gate structure. It uses multiple feedback paths, which add degrees of freedom in the choice of the LNA transconductance to reduce the noise figure (NF) and increase the amplification. The proposed LNA avoids the use of bulky inductors that leads to area and cost saving. A prototype is implemented in IBM 90-nm CMOS technology. It covers the frequency range of 100 MHz to 1.77 GHz. The core consumes 2.8 mW from a 2-V supply occupying an area of 0.03 mm2. Measurements show a gain of 23 dB with a 3-dB bandwidth of 1.76 GHz. The minimum NF is 1.85 dB, while the average NF is 2 dB across the whole band. The LNA achieves a return loss greater than 10 dB across the entire band and a third-order input intercept point IIP3 of - 2.85 dBm at the maximum gain frequency.

An Inductor-Less Noise-Cancelling Broadband Low Noise Amplifier With Composite Transistor Pair in 90 nm CMOS Technology

A new broadband low-noise amplifier (LNA) is proposed in this paper. The LNA utilizes a composite NMOS/PMOS cross-coupled transistor pair to increase the amplification while reducing the noise figure. The introduced approach provides partial cancellation of noise generated by the input transistors, hence, lowering the overall noise figure. Theory, simulation and measurement results are shown in the paper. An implemented prototype using IBM 90 nm CMOS technology is evaluated using on-wafer probing and packaging. Measurements show a conversion gain of 21 dB across 2-2300 MHz frequency range, an IIP3 of -1.5 dBm at 100 MHz, and minimum and maximum noise figure of 1.4 dB and 1.7 dB from 100 MHz to 2.3 GHz for the on-wafer prototype. The LNA consumes 18 mW from 1.8 V supply and occupies an area of 0.06 mm2.

A Self-Sustained CMOS Microwave Chemical Sensor Using a Frequency Synthesizer

In this paper, a CMOS on-chip sensor is presented to detect dielectric constant of organic chemicals. The dielectric constant of these chemicals is measured using the oscillation frequency shift of an LC voltage-controlled oscillator (VCO) upon the change of the tank capacitance when exposed to the liquid. To make the system self-sustained, the VCO is embedded inside a frequency synthesizer to convert the frequency shift into voltage that can be digitized using an on-chip analog-to-digital converter. The dielectric constant is then estimated using a detection procedure including the calibration of the sensor. The dielectric constants of different organic liquids have been detected in the frequency range of 7-9 GHz with an accuracy of 3.7% compared with theoretical values for sample volumes of 10-20 μL. The sensor is also applicable for binary mixture detection and estimation of the fractional volume of the constituting materials with an accuracy of 1%-2%.