INCREMENTALLY ADJUSTABLE CAPACITOR UNIT FOR TUNING A CRYSTAL-CONTROLLED OSCILLATOR

• US 3,754,152 A
• Filed: 11/03/1971
• Issued: 08/21/1973
• Est. Priority Date: 11/03/1971
• Status: Expired due to Term

• Current Assignee: Dale R. Koehler, William W. Mutter
• Original Assignee: Dale R. Koehler, William W. Mutter
• Inventors: Koehler, Dale R., Mutter, William W.
• Primary Examiner(s): Miller, J. D.
• Assistant Examiner(s): Budd, Mark O.
• Application Number:
  US05/195,348
• Time in Patent Office: 657 Days
• Field of Search: 310/8,8.1 331/116,139,159,158,160 318/116,118 317/249R,261
• US Class Current: 310/318
• CPC Class Codes: G04F 5/066 Trimmer condensators
• CPC Class Codes: H03B 2201/01 Varying the frequency of the oscillations by manual means
• CPC Class Codes: H03J 2200/10 Tuning of a resonator by means of digitally controlled capacitor bank
• CPC Class Codes: H03K 3/283 Stabilisation of output , e.g. using crystal

Abstract

A capacitor unit adapted to adjust the frequency of a crystalcontrolled oscillator in incremental steps, the oscillator serving as a frequency standard for an electronic timepiece. The unit is constituted by a bank of capacitors whose respective values fall into a binary series, each capacitor being associated with a switch arranged to connect the capacitor in parallel relation to the other capacitors in the bank, whereby the reactance presented by the unit may be varied incrementally by selective operation of the switches to create a reactance range whose lowest value is determined by the smallest capacitor alone, whose highest value is determined by the sum of all the capacitors in the bank, and whose intermediate values are determined by the capacitors singly or in shunt combinations thereof.

Claims

1. In combination with a crystal-controlled oscillator, an incrementally adjustable capacitor unit for tuning the crystal oscillator throughout a relatively broad total range to a desired value, in minute steps each of which produces a like incremental change in the frequency of the oscillator said unit comprising:

a. a bank of capacitors having a predetermined number of capacitors whose respective values are in a binary ratio series, the smallest capacitor value in the bank being chosen to satisfy the required frequency adjustment resolution, the sum of all values in the series satisfying the required total range of frequency adjustment, and b. selective switching means for connecting the capacitors in said bank in parallel relation to produce an output capacitance whose lowest value is equal to the value of the smallest capacitor, whose highest value is equal to the sum of the capacitor values and whose intermediate values depend on which switching means are operative, said switching means being constituted by a group of switches equal in number to the number of said capacitors, each switch in the group being connected in series with a corresponding capacitor in the bank to produce a series circuit therewith, the series circuit formed by the bank of capacitors and the group of switches being connected in parallel relation to said crystal oscillator whereby said oscillator is tunable throughout said total range in equi-spaced steps running from the lowest to the highest frequency in the range, the magnitude of each step being equal to the change in frequency produced by the smallest capacitor value in the bank, said capacitors being constituted by a dielectric layer formed on a conductive chip body, the conductive body forming a common rear face electrode, with separated front face electrodes whose dimensions determine the capacitance values in said binary series, said chip being mounted on a Printed circuit board having a conductive base plate, said circuit board having conductive connections leading to said front face electrodes, said group of switches being formed by switching screws extending through the printed board and threadably received in said base plate, said screws, when fully extended, acting to engage said conductive connections to complete a circuit to the base plate.

2. A unit as set forth in claim 1, wherein said series is composed of capacitors having the values of 0.5, 1, 2, 4, 8 and 16 picofarads.

3. A unit as set forth in claim 1, further including an additional front face electrode internally connected to the common electrode to provide a front face connection to the common electrode.

4. A unit as set forth in claim 1, wherein said chip is encapsulated on said board.

5. A crystal-controlled oscillator in combination with a capacitor unit, as set forth in claim 1, wherein said oscillator functions as the frequency standard of an electronic watch, which includes a frequency divider to derive low frequency timing pulses from said oscillator.

6. The combination set forth in claim 1, wherein said pulses are applied to the drive coil of a tuning fork motor for operating time indicators.