Temperature phase shift circuit and coordinate input apparatus

Details Temperature phase shift circuit and coordinate input apparatus Temperature phase shift circuit and coordinate input apparatus

1994-12-30

1999-11-23

Wells, Kenneth B.

Miscellaneous active electrical nonlinear devices, circuits, and

Signal converting, shaping, or generating

Phase shift by less than period of input

327513, H03H 1116

Patent

active

059907207

ABSTRACT:
An object of the invention is to provide a coordinate input apparatus which phase-shifts an input signal in accordance with temperature and corrects a phase shift due to a change in temperature, thereby performing coordinate input. A phase shift unit of a temperature phase shift circuit is constituted by connecting two thermistors having the same temperature characteristics and two capacitors having the same capacitance to constitute a bridge circuit. An output (Eout) has a gain of 1 with respect to an input (Ein) and is phase-shifted by tan.sup.-1 [(-2.omega.CR)/.+-.(1-.omega.CR).sup.2)], where R represents a value which exponentially varies in accordance with temperature. For this reason, the output signal can be phase-shifted in accordance with a change in temperature. When this circuit is applied to a coordinate input apparatus using an ultrasonic wave vibration, the phase shift of a vibration due to variations in temperature is corrected, thereby enabling coordinate input stable with respect to changes in temperature.

REFERENCES:
patent: 3947751 (1976-03-01), Bray
patent: 3997818 (1976-12-01), Bodkin
patent: 4414837 (1983-11-01), Bice et al.
patent: 4472669 (1984-09-01), Denham et al.
patent: 5253187 (1993-10-01), Kaneko et al.
patent: 5491305 (1996-02-01), Kawakami et al.
patent: 5537049 (1996-07-01), Oita et al.
patent: 5539160 (1996-07-01), Tokioka et al.
A Temperature-Compensated Bridge Circuit, by Masaru Matsuno, et al., published May 18, 1993, pp. 737-740.
IBM Technical Disclosure Bulletin, vol. 13, No. 1, Jun. 1970.

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