Xiaoyu Mi

MEMS tunable bandpass filters on high-k LTCC

This paper describes a novel MEMS tunable bandpass filter, which operates at the Ku band and features an extremely low insertion loss of −1.23–2 dB, a small size of 3.3 mm by 1.7 mm and a wide continuous tuning range of 36%. The tunable filter is based on MEMS-varactors-loaded microstrip resonators and has been directly constructed on a high-k low-temperature-co-fired-ceramics (LTCC) wiring wafer using newly developed MEMS-on-LTCC technology, which allows use of high-k materials as the filter substrate enabling a small size and low insertion loss, and greatly simplifies the fabrication and packaging processes. MEMS-on-LTCC technology combines the advantages of LTCC and MEMS and is promising for future reconfigurable radio front-end modules.

A full-time accelerated vertical comb-driven micromirror for high speed 30-degree scanning

This paper presents a new structure and driving method for a vertical comb-driven micromirror which enables full-time acceleration and mechanical 30-degree scanning with a 4-mm long mirror. Its optimal application is as a scanning mirror for laser beam printers, replacing polygon mirrors which have technical limits in relation to scanning speed.

Integrated Passives for High-Frequency Applications

1.1 Definitions of Integrated Passives Passive elements are indispensable in RF systems and are used for matching networks, LC tank circuits, attenuators, filtering, decoupling purposes and so on (Tilmans H. A C et al., 2003). Passive elements can be simply classified into distributed elements including transmission lines and waveguides, and lumped elements including inductors, capacitors and resistors. The distributed circuits take into account the phase shift occurring when the signal wave propagates along the circuits. As the operating frequency moves into the microwave spectrum, the distributed circuits have a higher Q factor, and thus they are usually used for high-frequency applications. Lumped elements are zero-dimensional by definition. In other words, the lumped elements have no physical dimensions which are significant with respect to the wavelength at the operating frequency, so that the phase shift that arises can be ignored. Discrete lumped elements are conventionally used in electronic circuits that work at a lower frequency. This is because the sizes of the discrete lumped elements become comparable to the wavelength at microwave frequencies. With the advent of new photolithography and passive integration technologies, the three basic building blocks for circuit design-inductors, capacitors, and resistors can be made small enough to be available in lumped form (Tummala R. R. et al., 2000). Lumped passive components may be discrete, integrated or embedded. The discrete is a singular device in a leaded or surface mount technology (SMT) case. This includes screen-printed resistors, capacitors, and inductors. Passive integration technologies allow several passive components to be integrated, either into a substrate (embedded) or onto a substrate (integrated). Integrated passive devices usually come in a compact SMT package or chipscale package (CSP) as a stand-alone component with input, output and ground terminations, which is much smaller than the operating wavelength providing some complete circuit functions, such as impedance-matching, filtering and so on, for highfrequency applications up to several tens of GHz (Tilmans H. A C et al., 2003). The lumped element circuits have the advantage of a smaller size, lower cost, and wide-band characteristics, though the Q factor is generally lower than distributed circuits. Integrated lumped passive circuits with a small form factor are especially suitable for some RF and microwave applications where real estate or wide-band requirements are of prime importance, for example mobile phones or other handheld wireless products. The choice 13

A multi-chip directly mounted 512-MEMS-mirror array module with a hermetically sealed package for large optical cross-connects

A 512 MEMS mirror array module with a hermetically sealed package for large optical cross-connects is constructed by using newly developed multi-chip direct mounting (MCDM) technology and is demonstrated to enable a plusmn5 degree rotation of the two-axis stationary operation under a drive voltage of 160 V, while having a high resonance frequency of 2 kHz

A multi-step DRIE process for a 128 /spl times/ 128 micromirror array

A multi-step DRIE process for fabricating a vertical comb-driven micromirror array with five different heights was developed. This process was used to fabricate a dual-axis 128 /spl times/ 128 micromirror array with a high resonance frequency.

Miniaturized microwave tunable bandpass filters on high-k LTCC with integrated resistive vias as bias-T

This paper describes a MEMS tunable bandpass filter operating in the S band region and featuring a low insertion loss of −2.3 dB and small size of 3.7 mm by 4.1 mm. The tunable filter is based on MEMS-varactors-loaded microstrip resonators and has been directly constructed on a high-k low-temperature-co-fired-ceramics (LTCC) wiring wafer whose dielectric constant is 50, using MEMS-on-LTCC technology. The RF signal paths are isolated from the MEMS driving paths by built-in high-resistivity-vias, leading to low insertion loss. RF power-proof performance was evaluated by applying OFDM signals to the device. The results confirm that MEMS tunable filters are sufficiently linear at cell phone power level.

Integrated Passives on LTCC for Achieving Chip-Sized-Modules

This paper describes the design, fabrication and performance of integrated passives devices (IPDs) on LTCC wiring substrates developed for RF-module applications, which have a high quality factor and high self-resonance frequency. A two-layered aerial spiral coil structure and 3D interconnection in the air are used to increase the quality factor of inductors and to reduce the parasitic capacitance in the coils and capacitors. This configuration enables Q-factor of 40 to 60 at 2 GHz for spiral inductors smaller than iquest 0.6 mm, while providing a self-resonance frequency higher than 8 GHz. A Q-factor of 180 at 2 GHz has been achieved for capacitors. The high-Q IPD has been directly fabricated on an LTCC wiring wafer using newly developed multistage plating technology based on a sacrifice layer, which allowed the easy formation of 3D coils and interconnections. The LTCC wiring substrate can offer dense interconnects between the integrated passive circuits and the functional devices mounted above the IPD. This technology combines the advantages of LTCC and IPD and is promising for the miniaturization of future RF-modules.

A multipoint thin film polymer pressure/force sensor to visualize traditional medicine palpations

This paper describes a novel multipoint thin film polymer pressure/force sensor enabling detection of pressure/force pulse wave. The sensor features a high sensibility of 11mv/mmHg along with an extremely thin thickness of 100 μm and a high flexibility to adapt to the radial artery portion. The sensor uses charged cellular polymer as sensing layer, which contains 25 separated sensing dots to avoid signal interaction among these sensing points. The sensor attaches to a persons wrist to detect the radial artery vibration, while a physician palpates the artery vibration with his fingertips on it. The sensor is thin and flexible enough to let the artery vibration transmit through it without spoiling the physicians tactile feeling. That makes it possible to correlate the measured pressure/force pulse wave and the physicians pulse diagnosis in real time. That is useful for objectification and quantification of pulse palpation in traditional medicine.

Tongue's substance and coating recognition analysis using HSV color threshold in tongue diagnosis

In ISO TC249 conference, tongue diagnosis has been one of the most active research and their objectifications has become significant with the help of numerous statistical and machine learning algorithm. Color information of substance or tongue body has kept valuable information regarding the state of disease and its correlation with the internal organs. In order to produce high reproducibility of color measurement analysis, tongue images have to undergo several procedures such as color correction, segmentation and tongue’s substance-coating separation. This paper presents a novel method to recognize substance and coating from tongue images and eliminate the tongue coating for accurate substance color measurement for diagnosis. By utilizing Hue, Saturation, Value (HSV) color space, new color-brightness threshold parameters have been devised to improve the efficiency of tongue’s substance and coating separation procedures and eliminate shadows. The algorithm offers fast processing time around 0.98 seconds for 60,000 pixels tongue image. The successful tongue’s substance and coating separation rate reported is 90% compared to the labelled data verified by the practitioners. Using 300 tongue images, the substance Lab color measurement with small standard deviation had revealed the effectiveness of this proposed method in computerized tongue diagnosis system.

A 3D heterogeneous integration method using LTCC wafer for RF applications

This paper describes the concept, fabrication process technologies and performance of a novel 3D heterogeneous integration method developed for RF applications. This method combines the advantages of LTCC, passive integration and MEMS technologies and is promising for the miniaturization and multifunction of future RF-modules. The basic concept is to form a large-size LTCC wiring wafer, and then to form high-Q passives or MEMS directly on the wafer surface. Other functional devices such as the ICs, SAWs are mounted above the surface-formed devices. LTCC wafer can provide dense interconnects and backside pads to provide input and output paths. All of the fabrication processes are carried out at wafer level, which leads to high productivity. A miniaturized duplexer and a MEMS tunable filter were constructed to demonstrate its feasibility and effectiveness.