Masahiro Toki

Analysis of start-up characteristics of CMOS crystal oscillators

A method for analysis of the start-up characteristics of CMOS crystal oscillators is described. The cause of oscillation just after DC power supply switched on is described and confirmed by experiment. The analytical method is outlined for calculation of the overall start-up characteristics of the amplitude of oscillation. Experimental results are given to verify the usefulness of this method.<<ETX>>

A flat energy density antenna system

A novel flat antenna system for energy density reception for mobile telephony is presented, and the configuration of the model antenna is demonstrated. The system is based on the assembly of a notch array cut into the circular disk of a ring patch antenna. The measured input impedance characteristics and radiation pattern of the antenna are presented. The experimental results indicate that this antenna system is appropriate as a mobile telephony antenna.<<ETX>>

Low DC-driving-voltage crystal oscillator

Low power requirements in electronic equipment needs low dc-driving-voltage crystal oscillators. This paper presents a low dc-voltage design of the crystal oscillator by using depletion+enhancement MOSFET (D+E MOSFET). D+E MOSFET is a device in which an electric-field is embedded, so that it requires no gate bias voltage for the amplification act. Thus low dc-driving-voltage is expected when the D+E MOSFET is used as an active element of the oscillator circuit. According to this idea, a low-dc-voltage Colpitts crystal oscillator has been devised. The oscillator actually produced 10 MHz output voltage for dc-driving-voltage as low as 0.45 V. The peak value of the output signal voltage of oscillation is close to a half of the dc-driving voltage. Thus it has been concluded that the proposed low dc driving-voltage crystal oscillator will be useful for achieving low power electronic equipment.

High effective Q CMOS crystal oscillator design

According to a narrowing of frequency bandwidth in communication systems, high C/N crystal oscillators are required. In this report, a design method of high effective Q CMOS crystal oscillators is proposed to achieve high C/N characteristics. The method is achieved by inserting a series capacitance between the output terminal of CMOS and the /spl pi/-shaped feedback circuit. An example of design shows that the dissipation of the active circuit facing the crystal resonator can he reduced by a factor 1/25 and the effective Q can be increased by a factor 7. Thus the effectiveness of the design method has been shown. It is concluded that the present method is useful for achieving high C/N CMOS crystal oscillators.