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.     

Effect of filter parameters on the phase noise of RF MEMS tunable filters employing shunt capacitive switches

The effect of filter parameters on the phase noise of RF MEMS tunable filters employing shunt capacitive switches is investigated in this article. It is shown that the phase noise of a tunable filter is dependent on the input power, fractional bandwidth, filter order, resonator quality factor, and tuning state. Phase noise is higher for filters with smaller fractional bandwidth. In filters with high fractional bandwidth (>3%), phase noise increases as the input power approaches the power‐handling capability of the filter. In filters with smaller bandwidths, phase noise increases with input power upto a threshold level of input power, but begins to decrease thereafter. The unloaded quality factor of the filter has a noticeable effect on the phase noise of filters with narrow bandwidths. The phase noise changes with the filter tuning state and is maximum when all the switches are in the up‐state position. It is also shown that the phase noise increases with the filter order, due to increase in the number of noisy elements in the filter structure. This article provides a methodology to evaluate the phase noise of a tunable filter and proves that RF MEMS filters are suitable for high performance applications without considerable phase‐noise penalty. © 2009 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2010.     

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).     

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.     

A Millimeter-Wave (23–32 GHz) Wideband BiCMOS Low-Noise Amplifier

This paper presents a 23–32 GHz wideband BiCMOS low-noise amplifier (LNA). The LNA utilizes coupled-resonators to provide a wideband load. To our knowledge, the proposed LNA achieves the widest bandwidth with minimum power consumption using 0.18 $mu$m BiCMOS technology in K-band. Analytical expressions for the wideband input matching, gain, noise figure and linearity are presented. The LNA is implemented using 0.18 $mu$m BiCMOS technology and occupies an area of 0.25 mm$^2$ . It achieves a voltage gain of 12 dB, 3-dB bandwidth of 9 GHz, noise figure between 4.5–6.3 dB, linearity higher than ${-}$6.4 dBm with a power consumption of 13 mW from a 1.5 V supply.      

Power-Aware Multiband–Multistandard CMOS Receiver System-Level Budgeting

A systematic system-level design methodology for multiband-multistandard (MB-MS) wideband/reconfigurable CMOS receivers is presented. The methodology determines the specifications (noise figure (NF) and linearity) for each building block to minimize the overall power consumption. System-level simulations show that the gain variation of the LNA for various bands/standards is an important factor in minimizing the power consumption for any MB-MS receiver. Analytical expressions for the optimum gain variation of the LNA, NF, and input-referred third-order intercept point of each building block are presented. The design methodology is applied to a wideband receiver covering Global Systems for Mobile Communications (GSM) 900- and 1900-MHz bands, Global Positioning Systems (GPS), and wideband code-division multiple-access (WCDMA) standards. As an example, the estimated power consumption is reduced by 40% when compared with the approach where the gain of the LNA is constant.     

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.