Packaged RF MEMS Switches Research Articles

RF MEMS packaged switch evaluation tests up to 25 GHz

This article presents the results of the series of experimental tests of a packaged RF MEMS switch manufactured as a chip on a silicon substrate in the Center for Materials and Microsystems of Fondazione Bruno Kessler. Experiments have been performed up to 25 GHz and included S-parameters check in different operation and environmental conditions, including variation of input power, ambient temperature and number of switching cycles. Presented RF MEMS SPST switch is a basic element of more complex reconfigurable networks such as SPxT switches, phase shifters, power attenuators etc.

Wafer-Level Packaging Method for RF MEMS Applications Using Pre-Patterned BCB Polymer.

A radio-frequency micro-electro-mechanical system (RF MEMS) wafer-level packaging (WLP) method using pre-patterned benzo-cyclo-butene (BCB) polymers with a high-resistivity silicon cap is proposed to achieve high bonding quality and excellent RF performance. In this process, the BCB polymer was pre-defined to form the sealing ring and bonding layer by the spin-coating and patterning of photosensitive BCB before the cavity formation. During anisotropic wet etching of the silicon wafer to generate the housing cavity, the BCB sealing ring was protected by a sputtered Cr/Au (chromium/gold) layer. The average measured thickness of the BCB layer was 5.9 μm. In contrast to the conventional methods of spin-coating BCB after fabricating cavities, the pre-patterned BCB method presented BCB bonding layers with better quality on severe topography surfaces in terms of increased uniformity of thickness and better surface flatness. The observation of the bonded layer showed that no void or gap formed on the protruding coplanar waveguide (CPW) lines. A shear strength test was experimentally implemented as a function of the BCB widths in the range of 100–400 μm. The average shear strength of the packaged device was higher than 21.58 MPa. A RF MEMS switch was successfully packaged using this process with a negligible impact on the microwave characteristics and a significant improvement in the lifetime from below 10 million to over 1 billion. The measured insertion loss of the packaged RF MEMS switch was 0.779 dB and the insertion loss deterioration caused by the package structure was less than 0.2 dB at 30 GHz.

K-band MEMS-based frequency adjustable waveguide filters for mobile back-hauling

This paper presents the first experimental results of a novel MEMS-based waveguide filter for mobile back-hauling at K-band with adjustable center frequency. The tuning concept employs commercial packaged RF MEMS switches, wire-bonded within a rectangular cavity. The switches are used to perturb the current distribution of the TE101 mode so as to tune the resonant frequency of the cavity. A tuning range up to 2% with unloaded Qs of the order of 1000 in K-band can be obtained. A second-order filter prototype employing commercially available MEMS on silicon substrate has been tested. Measurements show a 160 MHz frequency shift (0.7%) and Qs up to 1000 using only one MEMS per resonator. New higher-order prototypes using low-loss substrate MEMS (e.g. quartz) will be fabricated in order to get higher Qs. The concept here present leads to a very simple structure. The number of MEMS per resonator is, in fact, minimized (we use only one MEMS) and the design is simple. On the other hand, the achievable tuning range is lower (<2%) than the other concepts. Higher tuning ranges are achievable using more MEMS, but at the expense of lower Qs of the resonators.

A 1.7–2.7-GHz 4-bit Phase shifter based on packaged RF MEMS switches

This study presents a 4-bit phase shifter with a maximum phase shift degree of 75° based on packaged metal-contact single-pole double-throw (SPDT) radio frequency microelectromechanical system (RF MEMS) switches mounted on a 20 mil RO4350 substrate and assembled with its driver module on a 4-layer printed circuit board (PCB) board. Electric length of 10° and characteristic impedance of 61.7 Ω are selected for T-stub matching. Standard PCB processing makes it easy to develop and suitable for taking place of mechanical tilt employed in recent base station. Measurements indicate a maximum insertion loss of 1.37 dB at 2.7 GHz and a minimum return loss of 11.71 dB. The phase accuracy is within 1.75° at 2.7 GHz.

RF MEMS BASED HALF MODE BOWTIE SHAPED SUBSTRATE INTEGRATED WAVEGUIDE TUNABLE BANDPASS FILTER

A tunable planar bandpass filter based on a technique that utilizes a half mode substrate integrated waveguide (HMSIW) and novel inter-resonator coupling is presented. The tunable HMSIW based bandpass filter is implemented using two half triangle shaped cavities coupled together through inter-resonator coupling forming half mode bowtie shaped structure. The bowtie-shaped filter exhibits similar performance as found in rectangle- and circle-shaped SIW based bandpass filters. This concept reduces the circuit foot print, and miniaturization high quality factor is maintained by the structure. The tunable filter utilizes packaged RF MEMS switches; switching between different configurations of switches achieves four distinctive frequency states between 4.8-5.3 GHz. The filter maintains a constant absolute 1 dB bandwidth of 100 ± 10 MHz for all frequency states.

A fully wafer-level packaged RF MEMS switch with low actuation voltage using a piezoelectric actuator

In this paper, a fully wafer-level packaged RF MEMS switch has been demonstrated, which has low operation voltage, using a piezoelectric actuator. The piezoelectric actuator was designed to operate at low actuation voltage for application to advanced mobile handsets. The dc contact type RF switch was packaged using the wafer-level bonding process. The CPW transmission lines and piezoelectric actuators have been fabricated on separate wafers and assembled together by the wafer-level eutectic bonding process. A gold and tin composite was used for eutectic bonding at a low temperature of 300 °C. Via holes interconnecting the electrical contact pads through the wafer were filled completely with electroplated copper. The fully wafer-level packaged RF MEMS switch showed an insertion loss of 0.63 dB and an isolation of 26.4 dB at 5 GHz. The actuation voltage of the switch was 5 V. The resonant frequency of the piezoelectric actuator was 38.4 kHz and the spring constant of the actuator was calculated to be 9.6 N m−1. The size of the packaged SPST (single-pole single-through) switch was 1.2 mm × 1.2 mm including the packaging sealing rim. The effect of the proposed package structure on the RF performance was characterized with a device having CPW through lines and vertical feed lines excluding the RF switches. The measured packaging loss was 0.2 dB and the return loss was 33.6 dB at 5 GHz.