Oscillators – Solid state active element oscillator – Transistors
Reexamination Certificate
1999-04-02
2001-01-09
Mis, David (Department: 2817)
Oscillators
Solid state active element oscillator
Transistors
C331S03600C, C331S10800D, C331S1160FE, C331S158000, C331S17700V, C331S179000
Reexamination Certificate
active
06172576
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of Invention
The present invention relates to a capacitor array unit, a capacitor array unit controller, an oscillation circuit, a voltage-controlled oscillator, an oscillation frequency adjusting system, and an oscillation frequency adjusting method. In particular, the present invention pertains to a capacitor array unit, a capacitor array unit controller, an oscillation circuit, a voltage-controlled oscillator, an oscillation frequency adjusting system, and an oscillation frequency adjusting method that are used in and for a voltage-controlled piezoelectric oscillation circuit.
2. Description of Related Art
[1] First Conventional Configuration
FIG. 31
is a circuit diagram showing the configuration of a first type of conventional voltage-controlled piezoelectric oscillation circuit. The voltage-controlled piezoelectric oscillation circuit, generally denoted by
100
, has the following parts or components: an output terminal OUT through which an oscillation signal SOSC of an oscillation frequency fOSC is output; a frequency-control terminal VC which receives a control voltage VC for varying the oscillation frequency fOSC; an input resistor Ri having one end connected to the frequency control terminal VC and intended to coarsely couple an oscillation frequency control circuit (not shown) that is connected by a user to the frequency control terminal VC while eliminating undesirable effect of the oscillation frequency control circuit on the oscillating stage; a piezoelectric resonator X connected to the other end of the input resistor Ri; a variable-capacitance diode (referred to as “varicap”, hereinafter) Cv having a cathode connected to a node between the input resistor Ri and the piezoelectric resonator X; and a trimmer capacitor (referred to also as a “trimmer”, hereinafter) CT having one end connected to the anode of the varicap Cv and the other end connected to a lower-potential power supply GND.
The voltage-controlled piezoelectric oscillation circuit
100
also has the following parts or components: a bias resistor RX having one end connected to a node between the varicap Cv and the trimmer CT and the other end connected to the lower-potential power supply GND; a first bias resistor R
1
having one end connected to a higher-potential power supply VCC and the other end connected to the other end of the piezoelectric resonator X; a second bias resistor R
2
having one end connected to a node between the piezoelectric resonator X and the first bias resistor R
1
and the other end connected to the lower-potential power supply GND; an NPN transistor Q
1
having a base connected to a node between the piezoelectric resonator X and the bias resistor R
1
; and a collector resistor Rc having one end connected to the higher-potential power supply VCC and the other end connected to the collector of the NPN transistor Q
1
.
The voltage-controlled piezoelectric oscillation circuit
100
further has the following parts or components: a DC cut-off capacitor CCO having one end connected to a node between the collector resistor Rc and the NPN transistor Q
1
and the other end connected to the output terminal OUT, intended to remove DC component of the oscillation signal SOSC; an emitter resistor Re having one end connected to the emitter of the NPN transistor Q
1
and the other end connected to the lower-potential power supply GND; a first oscillation capacitor CO
1
having one end connected to a node between the base of the NPN transistor Q
1
and the piezoelectric resonator X and the other end connected to a node between the emitter of the NPN transistor Q
1
and the emitter resistor Re; and a second oscillation capacitor CO
2
having one end connected to a node between the emitter of the NPN transistor Q
1
and the emitter resistor Re and the other end connected to the lower-potential power supply GND.
[2] Second Conventional Configuration
FIG. 32
shows a second type of conventional voltage-controlled piezoelectric oscillation circuit. In this Figure, reference numerals that are the same as those appearing in
FIG. 1
denote the same parts or components as those of the first type of known arrangement shown in FIG.
31
.
The second type of conventional voltage-controlled piezoelectric oscillation circuit
200
differs from the voltage-controlled piezoelectric oscillation circuit
100
of he first type in that the bias resistor RX is omitted, that the anode of the varicap Cv is connected to the lower-potential power supply GND and that the trimmer CT is connected to the varicap Cv in parallel therewith.
[3] Role of the Trimmer CT in the First and Second Conventional Arrangements
Actual oscillation center frequency f0′ that appears when a calibrated control voltage is supplied deviates from the target center frequency f0 due to, for example, variation in the characteristics of the components such as the piezoelectric resonator X and the varicap CV. The trimmer CT is intended to compensate for such a deviation, thereby controlling the actual frequency f0′ in conformity with the target center frequency f0.
Thus, the actual frequency f0′ is regulated to the target center frequency f0, provided that the capacitance value of the trimmer CT is adequately controlled.
In other words, the role of the trimmer CT is to correct deviation of the center frequency that appears due to variation of characteristics of components of the voltage-controlled piezoelectric oscillation circuit, such that the oscillation frequency coincides with the target oscillation frequency when a calibrated control voltage is applied to the oscillation circuit. In general, therefore, an adjustment of the trimmer CT is executed as the final step of the process for fabricating the voltage-controlled piezoelectric oscillation circuit, prior to the shipping of the same.
In an example, the capacitance value of the trimmer CT is adjusted such that a center frequency f0 of 13.0 (MHz) is obtained when a control voltage Vc of 2.5 (V) is applied.
The trimmer CT inherently is not intended to encourage the user to trim the oscillation frequency through adjustment thereof. However, when the voltage-controlled oscillation circuit is actually mounted on, for example, a printed circuit board, the oscillation center frequency f0′ may deviate from the target center frequency f0 due to, for example, a thermal stress. In such a case, the trimmer (CT can effectively be used to permit adjustment for the purpose of eliminating the deviation of the actual oscillation frequency f0 from the target oscillation center frequency f0.
[4] Role of the Varicap Cv in the First and Second Conventional Arrangements
The oscillation frequency fOSC is controllable by varying the capacitance CCv of the varicap Cv. The capacitance CCv in turn is controlled by varying the level of the control voltage Vc supplied to the frequency control terminal VC. For instance, in the aforesaid example, the oscillation frequency fOSC is controlled in the range of:
fOSC=13.0 (MHz)±100 (ppm)
when the frequency control terminal VC is supplied with a control voltage Vc as follows.
Vc=2.5±2.0 (V)
[5] Principle of Operation of the Voltage-controlled Piezoelectric Oscillation Circuit
A description will now be given of the principle of operation of the voltage-controlled piezoelectric oscillation circuit.
FIG. 33
shows an equivalent circuit which is equivalent to the voltage-controlled piezoelectric oscillation circuit during oscillation.
The voltage-controlled piezoelectric oscillation circuit is broadly divided into two portions: the piezoelectric resonator X and the remainder circuitry.
The piezoelectric resonator X can be expressed in terms of a series connection of an equivalent reactance L and an equivalent resistance R, while the remainder circuitry is expressed by a series connection of a load capacitance CL and a negative resistance −R.
FIG. 34
shows an equivalent circuit of the piezoelectric resonator.
The piezoelectric resonator X
Endo Takashi
Oka Manabu
Mis David
Oliff & Berridg,e PLC
Seiko Epson Corporation
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