JPS6115609B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a piezoelectric oscillator that can boost unnecessary waves other than the required oscillation frequency.

Conventionally, in a Colpitts type piezoelectric oscillator, in order to boost frequencies other than the required frequency, an inductance element whose combined reactance becomes inductive below the required frequency is connected in parallel to one of the phase rotation capacitive elements. However, such a circuit has the disadvantage that a fifth-order overtone is oscillated even though a third-order overtone is desired at a frequency higher than the required frequency, for example.

The object of the invention is to provide a piezoelectric oscillator which eliminates the above-mentioned drawbacks.

The piezoelectric oscillator of the present invention is characterized in that an inductance is connected in series with one of the connected phase rotation capacitors and an inductance is connected in parallel with the other capacitor in order to satisfy the phase condition.

Next, the present invention will be explained in detail with reference to the drawings.
FIGS. 1a and 1b are a circuit diagram showing a conventional Overton oscillator and a reactance characteristic diagram of a parallel circuit of an inductance 11 and a capacitor 12. In the figure, reference numeral 16 is an amplification section having a phase rotation of about 180 degrees, reference numeral 15 is a feedback resistor,
Reference numeral 14 is a piezoelectric vibrator, and reference numeral 13 is a capacitor that provides phase rotation. Note that ω ₁ , ω ₃ and ω ₅ shown in FIG. 1b represent the fundamental frequency, the third Overton frequency, and the fifth Overton frequency of the piezoelectric vibrator, respectively.

Reference numerals 11 and 12 represent a parallel circuit of an inductance and a capacitor that exhibit capacitance above a frequency near the center between ω ₁ and ω ₃ . The circuit of FIG. 1a becomes capacitive at frequencies of ω ₃ or more and satisfies the oscillation phase condition. Therefore, the circuit shown in FIG. 1a may oscillate even at frequencies of ω ₃ or more, for example, ω ₅ or sub-resonance.

FIGS. 2a and 2b are circuit diagrams for explaining the present invention, and an inductance 23 and a capacitor 27.
It is a reactance characteristic diagram of a series circuit with. In the figure, reference numeral 26 is an amplifier having a phase rotation of approximately 180 degrees, reference numeral 25 is a feedback resistor, reference numeral 24 is a piezoelectric vibrator, reference numeral 22 is a capacitor that provides phase rotation, and reference numerals 23 and 27 are ω. ₃ and ω ₅
This is a series circuit of an inductance and a capacitor that exhibits inductive properties above the frequency near the center between.

As shown by the curve XS, the circuit shown in FIG. 2a exhibits capacitance at frequencies below ω ₃ and satisfies the oscillation phase condition.

FIGS. 3a and 3b are circuit diagrams showing an embodiment of the present invention and diagrams showing reactance characteristics of the parallel circuit 1 and the series circuit 2. FIG. In the figure, reference numeral 36 is an amplifier having a phase rotation of about 180 degrees, reference numeral 35 is a feedback resistor, reference numeral 34 is a piezoelectric vibrator, and reference numerals 31 and 32 are at frequencies above the center of ω ₁ ω _3. Parallel ^circuit _of inductance and capacitance _exhibiting capacitance ( _{characteristic} ).

In a circuit with such a configuration, the curve X in Figure 3b
The oscillation condition is satisfied only in the vicinity of the frequency between _P and X _S , that is, ω ₃ . Therefore, at frequencies other than the vicinity of this frequency, even if the amplitude condition is satisfied, the phase condition is not satisfied and oscillation does not occur.

As described above, in the present invention, by appropriately setting the resonance points of the parallel circuit 1 and the series circuit 2, it is possible to easily and completely obtain the required values without worrying about the sub-resonance/overton of the piezoelectric vibrator or the frequency characteristics of the amplifying section. It becomes possible to select the oscillation frequency.

Furthermore, since other unnecessary modes are boosted, it is possible to select a large loop gain at a required frequency, and the reliability of oscillation (probability that oscillation does not stop) can be improved.

It goes without saying that the same effect can be obtained even if the series circuit 1 and the parallel circuit 2 in the embodiment shown in FIG. 3 are replaced.

[Brief explanation of the drawing]

Figures 1a and b are a circuit diagram and its reactance curve diagram showing a conventional Overton piezoelectric oscillator, Figures 2a and b are an oscillation circuit diagram and its reactance curve diagram for explaining the present invention, and Figure 3a and b are a circuit diagram and a reactance curve diagram showing one embodiment of the present invention. In FIG. 3, 36...an amplifier section having a phase rotation of about 180 degrees, 35...a feedback resistor, 32, 33...a phase rotation capacitor, and 34...a piezoelectric vibrator.

Claims (1)

[Claims] 1. A piezoelectric vibrator, a phase rotation capacitive element connected to the input terminal and output terminal of the piezoelectric vibrator, and the vibration energy of the piezoelectric vibrator is coupled to each other, and a phase rotation of about 180 degrees occurs between the input and output. A piezoelectric oscillator comprising an amplifier circuit and a feedback resistor that feeds back an output of the amplifier circuit to the piezoelectric vibrator, wherein a first inductance element is connected in series with one of the phase rotation capacitance elements. A piezoelectric oscillator characterized in that a second inductance element is connected in parallel to the other phase rotation capacitance element, and an oscillation phase condition is satisfied only within an arbitrary frequency range.