Suneat Pranonsatit

Novel RF MEMS Switches

This paper reviews three novel RF MEMS ohmic contact switches, each being designed for specific applications. All three were developed at Imperial College London. The first is a packaged single-pole double throw (SPDT) version intended for space applications, operating from DC to 6 GHz; the second is a single-pole single throw (SPST) switch for high power applications in the 40 to 60 GHz band; and the third is a single- pole eight throw (SP8T) switch for signal routing applications, operating from DC to 20 GHz. The design, and measurements for all three unique solutions will be briefly summarized.

Rotary RF MEMS Switch Based on the Wobble Motor Principle

A novel, truly rotary, single-pole eight-throw (SP8T) RF MEMS switch is reported. The concept is an adaptation of the axial-gap electrostatic wobble motor. Details of the switch design and fabrication process are presented, together with initial test results for prototype devices. DC contact resistance measurements have been made over half a million rotations, yielding an average contact resistance of 2.5 Ω. The switch shows promising RF performance, with insertion loss varying smoothly from 0.6 dB at 2 GHz to 4 dB at 20 GHz, and isolation better than 31 dB across the frequency range 0.5 to 20 GHz.

Affordable Ink-Jet Printed Antennas for RFID Applications

With the increasing demands of radio-frequency identification (RFID) applications, an alternative ink-jet printing technique for RFID tag antenna is demonstrated. Commercially available ink-jet printers are adapted for conductive printing, in order to minimize manufacturing cost. Paper-based dipole antenna and dipole with a tuning stub antenna were designed. The antennas were ink-jet printed and assembled with RFID chips. The performances of the fabricated tags were measured through the reading range. With reference to equivalent isotropically radiated power of 4 W at 923 MHz, the reading range of tag with dipole antenna is around 9 m and of tag with dipole with a tuning stub is nearly 13 m. These performances are comparable to those of commercial tags. The advantages of the proposed printing technique are simplicity, flexibility and, more importantly, affordability. The technique can, in addition, contribute to further development and enhance extension of RFID applications.

Micromachined screen printing (MaSPrint) technology for RF MEMS applications

Traditional screen-printing technologies have long been used for manufacturing large volume RF circuits. While being an extremely low cost manufacturing solution, there have been relatively few major advancements. For this reason, the resulting thick-film components are generally restricted to microwave frequencies of operation, due to limitations in manufacturing tolerances. At the same time, surface micromachining technologies have undergone rapid developments, enabling high performance and innovative RF MEMS components to be realized. However, when compared to screen printing, this manufacturing technology is very expensive, even for mass production. This paper will introduce, for the first time, a revolutionary technology for implementing true RF MEMS components using screen printing. The basic concepts will be described, including the use of sacrificial layers and photoimageable pastes. This will be followed by results of the first experimental surface micromachined suspension bridges. Detailed discussions will be given on how the authors propose to overcome limitations with this technology. For example, techniques for compensating shrinkage and large grain boundary sizes with the pastes. Finally, a vision of where MaSPrint technology could lead will be given, in the form of design concepts for low loss transmission lines, RF MEMS switches and variable capacitors, for use in cheap high performance filters and phase shifters for both microwave and millimetre-wave applications.

The applications of fill until full (FuF) for multiresonator-based chipless RFID system

Chipless RFID multiresonators, fabricated by Fill until Full (FuF) technique are demonstrated. In FuF, conductive material is filled into a mould with predefined dimensions. The thickness can be controlled by controlling volume of the ink, so that waste is minimized. A chipless RFID transponder consists of a multiresontor connected between 2 tranceiving antennas. A multiresonator is designed to be functioned as a stopband filter at 1.94, 2.58 and 3.49 GHz. The 3-bit signal can be encoded at these frequencies to represent 000 to 111 IDs. Chipless RFID multiresonator prototypes are designed, fabricated and measured. The measured insertion loss exhibited accurate attenuation at the defined frequencies. In conclusions, the FuF technique is proved to be appropriate for fabricating components in chipless RFID technology and for expanding the applications.

Laser diode sensors for measuring mechanical properties of recycled plastics

Uncertainty of mechanical properties is one of obstacles in the use of recycled plastic as raw materials. This paper presents a method for measuring mechanical properties of plastic products that are partially made of recycled plastic. Specifically, the plastic type of interest in this project is Polypropylene. The proposed method employs an analysis through a relationship between optical transmittance and tensile strength, which varies with recycled compositions. Adopted from spectroscopy technique, laser diode sensor was used to measure optical transmittance. The sensor is composed of a 1550 nm laser diode as a light source and a photodiode as a detector. Experimental results from laser sensing method are equivalent to results from spectrometry. Optical transmittance, as well as tensile strength, linearly increases with the ratio of recycled plastic. Statistically, every linear function has the coefficient of determination (R2) over 0.95. Thus, the mathematical relationships between optical transmittance and tensile strength were generated. In conclusions, the tensile strength of plastic with different percentages of recycled mixture can be measured by the use of the demonstrated laser diode sensor.