Yoshimasa Oomura

A low phase-noise oscillator design for high stability OCXOS

An oscillator design for high-stability SC-cut OCXOs is described that has high spectral purity. It uses an AT-cut resonator-filter to improve the oscillator phase noise and to suppress spurious-mode oscillations. The circuit details and phase noise performance are given, and we show the effect of the quartz driving current on long-term frequency aging.

Precise Determination of the Optimum Supporting Position of a Stress Compensated (SC) Cut Quartz Crystal Resonator Using a Semiconductor Pulsed-Laser System

This paper describes a precise method of determining the supporting position of a stress compensated (SC) cut crystal wafer using a semiconductor pulsed laser. Because the supporting position greatly influences the frequency stability against acceleration and/or external stress, an accurate determination method is required. The experimental results for circular SC-cut quartz resonators with various supporting positions demonstrate the validity of this technique.

An Improved Method for Determination of Surface Charge Distribution of Weak Spurious Modes in Quartz Plates.

The method described here accurately determines the two-dimensional surface charge pattern of a weak mode existing in the vicinity of a strong mode in quartz crystal plate using an equivalent model that suitably approximates the surface charge frequency characteristics in the target modes measured at each measurement coordinate. The surface charge frequency characteristics are measured by an automated measurement system based on the electrical probe method. The temperature characteristics of the measured surface charge pattern of a weak mode near the fundamental thickness-shear mode in a rectangular AT-cut plate demonstrated that even for a weak mode, the present procedure provides patterns clearer than those obtained with a previous technique.

The electrical behavior of the fundamental high frequency (150 MHz) quartz crystal unit in the plasmatic environment

Both photolithography technique and chemical etching process were experimentally employed for producing 150 MHz rectangular AT-cut crystal resonators. A plasma treatment was employed for a frequency adjustment process by etching gold (Au) electrode films. A large frequency shift from a designed frequency was observed. In this paper, the reasons are electrically and chemically explained why the large frequency shifts occurred after a plasma treatment.

The Resonating Properties of a Crystal Unit of Fundamental Frequency 150 MHz

150 MHz rectangular AT-cut quartz crystal units were prepared by means of photolithography. For the elimination of the effect on a frequency response by the mechanically damaged layer, chemical etching on both sides was employed. Gold evaporated films were used as the electrodes for frequency stability during long-term driving. As a result, crystal units which had excellent frequency stability during long-term driving and low crystal impedance were obtained. Furthermore, a Colpitts crystal oscillator was constructed, and some experimental data are presented.

The electrical behavior of crystal unit resonating at the fundamental frequency 150 MHz

In this paper, the 150 MHz rectangular AT-cut quartz crystal units were prepared by photolithography technique. The crystal units were measured precisely by the center line method. In addition, the oscillators equipped with the 150 MHz crystal unit were constructed on trial, and experimental results are shown.

Laser-Diode-Based Mode-Shape Measurement System for Very-High-Frequency Quartz Resonators

A laser-diode-based system for measuring the patterns of in-plane vibrational displacement in quartz resonators is described. This system utilizes the force-frequency effect in detecting the displacement. Its employment of a semiconductor laser-diode module makes the measurement fixture very simple and compact. The experimental results for a very-high-frequency AT-cut quartz resonator demonstrate the validity of this system.

Frequency Temperature Behavior of Miniaturized Circular Disk AT-Cut Crystal Resonator

Summary The requirement for the practical application of miniaturized AT-cut crystal resonator, of which frequency temperature behavior is cubic curve, has increased in accordance with the development of miniaturization of electronic components. The ratio of diameter to thickness of the conventional circular disk AT-cut plate is usually more than 15, but the ratio of miniaturized one described in this paper is ranged from 4.338 to 4.683; (diameter:from 6.329 mm to 6.832 mm, thickness:1.457 or 1.459 mm, resonance frequency: about 1.2 MHz). coupling modulus g, which is the ratio of the thickness shear modulus to the plate flexure modulus. The frequency temperature behavior of different cut angle was measured. With changing the diameter of specimen, the same measurment was also carried on. The inflection temperature and a very little change in resonance frequency within wide temperature range are discussed by the experimental results. The cut angle of specimen is decided by the

Measurement of temperature characteristics of two-dimensional surface charge patterns of spurious modes in rectangular quartz plates

Temperature characteristics of surface charge patterns of spurious vibrations near the fundamental modes in rectangular quartz plates have been measured. The technique is based on the electrical probe method that uses piezoelectrically induced surface charge. To measure the temperature characteristics of surface charge patterns, a measurement fixture with a DUT mover is set in a computer-controlled temperature chamber and these instruments are incorporated with a network analyzer based measurement system. The measurement results using 1 and 4 MHz rectangular AT-cut quartz resonators clearly indicate that the charge distributions of a spurious vibration and a fundamental one interchange their patterns according to temperature changes.<<ETX>>

Results of the quartz crystal measurement data obtained at the leadless resonator measurement workshop held in Japan

The authors present the results of a workshop held at Tokyo Metropolitan University for the purpose of investigating the measurement method and specifications for surface-mounted leadless crystal units, and obtaining actual data. It has been shown that unifying the basic specifications (PI circuit method) and the measurement software algorithm (proposed IEC specification) allows high-accuracy measurement to be conducted, even if different fixtures and measurement instruments are used.<<ETX>>