Tuning device and radio-wave corrected timepiece

• US 20060176777A1
• Filed: 05/20/2004
• Published: 08/10/2006
• Est. Priority Date: 05/20/2003
• Status: Active Grant

• Current Assignee: Citizen Watch Co Limited (Citizen Electronics Company Limited)
• Original Assignee: Citizen Holdings Co., Ltd. (Citizen Electronics Company Limited)
• Inventors: Ihara, Takashi
• Granted Patent: US 7,583,942 B2
• Time in Patent Office: Days
• US Class Current: 368/47
• CPC Class Codes: G04R 20/10 Tuning or receiving; Circuits therefor
• CPC Class Codes: G04R 60/12 inside metal cases
• CPC Class Codes: H03J 2200/10 Tuning of a resonator by means of digitally controlled capacitor bank
• CPC Class Codes: H04B 1/18 Input circuits, e.g. for coupling to an antenna or a transmission line coupling networks between antennas or lines and receivers independent of the nature of the receiver H03H

Abstract

A tuning apparatus is provided, wherein the on and off resistances of semiconductor switches within an tuning IC are optimized, so as to provide high sensitivity and superior stability, a wide range of tuned frequency variation, compactness and high performance. The tuning apparatus has a tuning circuit, which has N-channel MOS transistors (N transistors) 5a through 5f, serving as a plurality of semiconductor switches, and a counter circuit 6, which controls the opening and closing of the N transistors, a plurality of capacitors 4a through 4f, which are each connected in series with the plurality of N transistors, and a receiving antenna 2 wherein the total electrostatic capacitance of the plurality of capacitors is varied by the opening and closing of the plurality of N transistors, thereby varying the frequency tuned by the plurality of capacitors and the receiving antenna.

Claims

1. A tuning circuit comprising:

a semiconductor substrate, which comprises a plurality of semiconductor switches, a plurality of first capacitors, connected each in series with said plurality of semiconductor switches, and switch controlling means for controlling opening and closing of the semiconductor switches; and

a coil connected in parallel to said plurality of first capacitors,

wherein the total electrostatic capacitance of said plurality of first capacitors is varied by said switching controlling means individually controlling said opening and closing said plurality of semiconductor switches connected to said plurality of first capacitors, in accordance with a received station selection signal of a standard radio wave that includes time information, so as to vary a tuned frequency of a tuning circuit formed by said plurality of first capacitors and said coil.

2. A tuning circuit according to claim 1, further comprising, either on said semiconductor substrate or outside said semiconductor substrate, a second capacitor, which has either a fixed capacitance or a variable capacitance, and which is connected to said coil in parallel with said group of first capacitors.

3. A tuning circuit according to claim 2, wherein said second capacitor is subjected to control that differs from the control to which said first capacitors are subjected.

4. A tuning circuit according to either claim 2 or claim 3, wherein at least one of said second capacitances is controlled by said switch controlling means via said semiconductor switch provided on said semiconductor substrate.

5. A tuning circuit according to any one of claim 1 through claim 3, which is used, including an antenna, within a metal exterior part made of a metallic material.

6. A tuning circuit according to any one of claim 1 through claim 3, wherein an on resistance of each of said semiconductor switches is smaller than an impedance of each of said first capacitors connected in series with each said semiconductor switch.

7. A tuning circuit according to any one of claim 1 through claim 3, wherein an off resistance of each of said semiconductor switches is larger than an impedance of each of said first capacitors connected in series with each said semiconductor switch.

8. A tuning circuit according to any one of claim 1 through claim 3, wherein a resistance value of a resistance part used in an amplifier circuit connected to a receiving circuit is set so as to be larger than an impedance of a tuning capacitor provided in said tuning circuit.

9. A tuning circuit according to any one of claim 1 through claim 3, wherein a resistance value of a resistance part used in an amplifier circuit connected to a receiving circuit is set so as to be larger than an impedance of a capacitor connected in series with said resistance part used in said amplifier circuit.

10. A tuning circuit according to any one of claim 1 through claim 3, wherein the total value of individual electrostatic capacitances of each of said plurality of first capacitors is 9600 pF or lower.

11. A tuning circuit according to any one of claim 1 through claim 3, wherein an inductance value of said coil is 0.44 mH or greater.

12. A tuning circuit according to any one of claim 1 through claim 3, wherein an inductance value of said coil is 4000 mH or smaller.

13. A tuning circuit according to any one of claim 2 through claim 3, wherein a tuned frequency in said tuning circuit is determined by a first electrostatic capacitance set by a group of said first capacitors and a second electrostatic capacitance of said second capacitor.

14. A tuning circuit according to any one of claim 2 through claim 3, wherein said electrostatic capacitance of said second capacitor is larger than that of said first capacitor.

15. A radio-controlled timepiece comprising:

a tuning circuit according to any one of claim 1 through claim 3;

a control means, which controls said tuning circuit, and which has a receiving circuit, which inputs a standard radio wave received by said tuning circuit and performs time correction; and

a display means, which displays time information from said control means.

16. A radio-controlled timepiece according to claim 15, further comprising a metal exterior part made of a metallic material, which covers said tuning circuit, said control means, and said display means so as to protect them mechanically.

17. A radio-controlled timepiece according to claim 14, wherein an inductance of said coil of said tuning circuit covered by said metal exterior part is 20 mH or greater.

18. A radio-controlled timepiece according to claim 15, wherein, by controlling the opening and closing of said plurality of semiconductor switches of said tuning circuit so as to vary said tuned frequency, it is possible to selectively receive any of a plurality of standard radio waves.

19. A radio-controlled timepiece according to claim 15, further comprising a tuning control information storage means for storing tuning control information for the purpose of varying said tuned frequency of said tuning circuit.

20. A radio-controlled timepiece according to claim 19, wherein said tuning control information storage means is provided within said tuning circuit.

21. A radio-controlled timepiece according to claim 19, wherein said tuning control information storage means is formed by one selected from the group consisting of a pattern-cutting means, a fuse ROM, and a non-volatile memory.

22. A radio-controlled timepiece according to claim 15, comprising a test mode, whereby it is possible to change a tuned frequency by an external operating means provided outside said radio-controlled timepiece.

23. A radio-controlled timepiece according to claim 22, wherein said external operating means includes a non-contact operating method.

24. A according to claim 23, wherein said non-contact operating method uses radio or infrared.