A disk composite-array structure has been demonstrated that places its constituent disks in a triangular pattern around a “ mechanical output” disk, while coupling them with half-wavelength links, in order to accentuate a desired resonant mode while suppressing unwanted modes. Using this mechanical circuit structure, disk array-composite filters with less than 0.2% bandwidth and centered in the 150-600 MHz UHF range have been demonstrated with no spurious modes in a ± 200 MHz range around their radial-mode center frequencies. In addition to resonator arraying, these filters utilize lateral solid dielectric capacitive transducers to further reduce dc-bias voltages to as low as 4V. By replacing transverse resonators with higher frequency, higher Q lateral disks, this work provides a path to better performing communication oscillators and filters based on MEMS technology.

Disk-Array Design for Suppression of Unwanted Modes in Micromechanical Composite-Array Filters

In this study, the dual modulated quartz crystal microbalance (QCM) with heating and cooling control has been developed for the quantitative determination of biological molecules, as a biosensor. On the other hand, since, the Sauerbrey formula is misprinted in some publications, the correct form of formula is also discussed. The proposed QCM biosensor has three main parts, which are the oscillator circuit, temperature control circuit, and the differential frequency measurement unit. Colpitts oscillators with the buffer amplifier, microcontroller (PIC16F877) for the temperature control circuit and a peltier element were used for heating and cooling inside the developed system. Differential frequency measurement is a known technique to compensate environmental effects causing instability of crystals. For this reason, one of the crystals is implemented with oscillatory circuits, i.e., the detector; the other one is used as the reference. The designed system was tested between 8°C and 50°C and frequency shift...

Design of temperature controlled quartz crystal microbalance system

Abstrort - Temperature-compensated or ovenlzed crystal oscillators (TCXO or OCXO) are widely used In self-contained equipment, especially in cases when a highly-stabillzed frequency IS needed In these oscillators, AT-cut crystal resonators are generally employed because of the ease of resonator deslgn and frequency controllabillty Varlation of osclllatlon frequency with tlme IS called "aglng", and is caused by the aglng of the resonator Itself When the variation is smooth, regular callbratlon is effective There are. however, many cases when the varlatlon evidences a "~ump " While many causes may be considered for this, the aglng of a nearby mode is regarded as the leadlng cause when the frequency Jumps suddenly. To avold this nearby mode influence, whlch decreases the long term frequency stablllty, detectlon and avoidance of the mode must precede oscillator assembly If a cause of aglng In the spurious modes IS also relaxation of lattlce defects In a quartz plate or electrodes, then the phenomenon IS related to integratlon of the provlded electrlcal power Based upon thls background the relation between the mtegratmg drive level and the drlve level-frequency dependence (DLD) of the nearby mode was examined for AT-cut quartz resonators used In hlgh stability OCXOs. The authors had previously developed a preclse measurement system for DLD characteristics We have also pomted out that the frequency jump appears to depend on the resonator drive level. We used some quartz resonators which exhibited DLD frequency jumps. These are caused by the nearby mode. The experimental investlgation Included; (I) the resonator was vlbrated by a constant drlvlng current at regular intervals. (2) after one interval, the frequency-Jump (current) was searched by DLD characterlstlc measurements By contlnuing thls sequence. we specified a relation between the drive level integration (or elapsed tlme) vs the "frequency jump current" The results clearly indlcated that the "frequency jump current" level Increases as a functlon of drlve current integration We concluded that the drlve level characterlstlcs of nearby modes vaned wlth the total (Integrated) power provided to the resonator The oscillation frequency then jumps suddenly

1995 IEEE INTERNATIONAL FREQUENCY CONTROL SYMPOSIUM An Experimental Study of Long Term Aging of Quartz Oscillators

The frequency stability of a crystal sensor in liquid is influenced by a decrease in Q value. Also, the frequency stability is influenced by the water pressure, liquid temperature, and etc. this paper shows a new method of realizing a highly precise crystal sensor by using two crystal sensors for the purpose of solving the above mentioned problem. In conclusion, it has been verified that a crystal resonator having two pairs of electrodes on one AT-cut crystal blank can be used for sensors in liquid for various applications.

Examination for realization of a high precision crystal sensor

This paper describes oscillation frequency stability of a crystal sensor for biosensors used for detection of dioxins, PCB, environmental-stressors, and marker proteins for infections. Present frequency stability is about 0.1 ppm in 9 MHz. Design technology for communication is applied to the crystal unit and oscillator circuit as a sensor. We prepared a crystal unit for filters in an oscillator circuit, and adopted a method that engenders oscillation frequency stability. That method demonstrates performance of 5 ppb at 9 MHz and 14 ppb at 155 MHz.

M. Okazaki

Papers

Frequency stability of a crystal resonator for biosensors