JPS6264103A - Oscillation circuit - Google Patents

Abstract

PURPOSE:To obtain an oscillation circuit suppressing the fluctuation of an oscillation frequency due to the variation in the inductance element value by connecting an inductance expanding the oscillating frequency region in series with a crystal oscillator and connecting a capacitor in parallel with the series connection. CONSTITUTION:When a data fed to a terminal In is at a low level, a potential at a terminal P1 is higher and the capacitance of a varactor diode D is small. A transistor (TR) 2, capacitors C20, C30, C40, a diode D and a crystal oscillator X form a Colpitz osillation circuit and the oscillation frequency is controlled in response to the level at the terminal IN. In inserting an inductance L10 to the crystal oscillator, the oscillating frequency is set widely and if the inductance L10 itself is fluctuated, the oscillating frequency is changed. Thus, a temperature compensation capacitor C10 having a proper temperature coefficient is connected in parallel with the inserted inductance L10. Thus, the fluctuation of the oscillated frequency is prevented independently of the selection of a type of material of a core used for the inserted inductance L10.

Description

[Detailed description of the invention] [Technical field of invention] This invention relates to an oscillation circuit using a crystal resonator.

In particular, the present invention relates to an oscillation circuit that can suppress fluctuations in oscillation frequency caused by temperature changes.

[Summary of the invention]

In an oscillation circuit having a crystal resonator in the feedback path, an inductance is connected in series to the crystal resonator in order to expand the wave number range between one oscillation.

In this case, while the oscillation frequency range is expanded,
When the insertion inductance changes, the oscillation frequency of the single oscillation circuit becomes unstable. To deal with this, in the present invention, a capacitor is connected in parallel to the insertion inductance, so that the oscillation frequency range can be expanded by one without floating the oscillation frequency.

[Technical drawbacks of the invention and its problems]

Generally, frequency shift keying modulation (Frequency 5hift Keyirxf) in data transmission is commonly used.
: FSK) has the advantage of improving the signal-to-noise ratio depending on the degree of modulation, and is used as a data communication means such as bidirectional CATV.

In the vicinity of the resonance point, the crystal camera is represented by an equal number of circuits as shown in FIG. The impedance 2 of this equal circuit is expressed by a linear equation.

Z-R+jX・・・・・・・・・
・ (1) Here 1'pa. =1//ear I
...... (4) The absolute value 1z1° and phase ψ of impedance 2 shown in the above formula are +z+ =/FtsuK” ・−−−−−−(5)
ψ=jan−'(X/B) −−−−−−(6
), where the frequency at which X=o is the resonant frequency (ωr)9 anti-resonant frequency u7p, and considering the above equation (3).

Lur “F LIJo =21 ・・・・・・
(7) W, L9ω. f ``four ζ ...... (
8) Figure 3 is a characteristic diagram showing the actance characteristics of a crystal resonator, and as can be seen from the figure, the resonance frequency I) Jf
The beam actance exhibits inductance between and the anti-resonance frequency, and exhibits capacitance at other frequencies.

On the other hand, the equivalent circuit of an oscillation circuit using a crystal resonator is shown in FIG. 4, and in this case, the oscillation conditions for one oscillation circuit are expressed by the following equation.

IRI=l几L1・・・・・・(
9) jX= −jXL ・・・・・・
Normally, in an oscillator using a crystal oscillator, the reaction actance on the first circuit side is capacitive, so the crystal I reaction element is in the inductive frequency region between the resonant frequency CJ/,) and the anti-resonant frequency uJp. It will work.

When the circuit performs an oscillation operation, the actance on the circuit side is +jXt = 1/ jwcL, and the operating frequency is calculated using the above equations (3) and Ql.

obtain a relationship.

However, ==C/e.

Here, if a series coil L is inserted in the crystal resonator in order to obtain a wide range of frequency variation, the impedance Z' on the crystal resonator side including the series-connected coils will be z'=几'+jX'・・・・・・ （
1BR=B...
αjx'-x+田L ・・・・・・ I
Therefore, near the resonance frequency, the added inductance L
can be considered to be equivalent to inserting a negative capacitor Ca of the following formula.

Therefore, considering the single oscillation condition, a relationship is obtained that corresponds to the operating frequency when an inductance is added.

In this way, by adding an inductance in series to the crystal resonator as described above, the anti-resonant frequency (uJp) does not change, but the resonant frequency (uJp) becomes lower and the frequency interval between the anti-resonant frequency and the resonant frequency becomes substantially lower. expands and the oscillation range widens.

Figure 5 is a characteristic diagram showing that the oscillation frequency range is expanded depending on the inductance value inserted in the crystal resonator.
As can be seen from the figure, the oscillation frequency range can be expanded by inserting inductance.

However, while the oscillation frequency range is thus expanded by the insertion of the inductance.

When the inductance value changes, the oscillation wave number changes. For this reason, when F8 is used for data transmission, data errors occur and noise is also generated.

[Purpose of the invention]

In view of the above points, it is an object of the present invention to provide an oscillation circuit using a crystal resonator in which fluctuations in oscillation frequency are suppressed.

[Embodiments of the invention]

FIG. 1 is a circuit diagram showing an embodiment of an oscillation circuit according to the present invention, and shows an example of an oscillation circuit used for FSK transmission.

In FIG. 1, transmission data is applied to the data input terminal, and the switching transistor Trx performs switching according to the level value of the transmission data. now,
When the level of data applied to the terminal IN is at a high level, the transistor Tr becomes conductive, and a voltage obtained by dividing the power supply voltage B by the resistor and the resistor is generated at the connection point P1 between the resistor and the resistor.

Furthermore, when the level of the terminal Δ is low, the transistor 'I'rt is in a cutoff state, and the connection point P1
A voltage obtained by dividing B in the power supply voltage by (Kameko Rs + R4) is applied to .

That is, the potential of the terminal P1 is higher when the transmission data is at a low level than when it is at a high level.

The capacitance value of varactor diode D becomes smaller.

Transistor Tr2. Capacitor C, , C e C4
1> forms a Colpitts oscillation circuit together with the varactor diode D and the crystal resonator X, and the oscillation frequency is controlled according to the level of the terminal IN. In addition.

The capacitor C blocks the DC component and one oscillation output is output from the output terminal OUT. Further, for the transistor Trz, a resistor R6, a resistor 1. R6 functions as a bias resistor.

In the above oscillation circuit, the inductance L1. teeth,
As previously mentioned. This element was inserted to expand the single oscillation frequency range of an oscillation circuit using a crystal resonator, but the oscillation frequency fluctuates significantly with changes in the inductance value of this inductance L16, especially temperature-dependent changes. becomes.

In this way, there is an inductance L in the crystal oscillator. Although the same wave number of the oscillation frequency can be set over a wide range by inserting the oscillation frequency, FIG. 6 shows how the frequency changes depending on the value of the insertion inductance L1°. In the same figure, the value of the insertion inductance L0 is shown as a parameter for the change characteristic of the amount of change frequency with respect to the center frequency of one oscillation circuit. As can be seen from the characteristic diagram, as the value of the insertion inductance increases, the variable frequency range is expanded. As the insertion inductance value L1° increases, the oscillation frequency range becomes wider, but if this inductance itself changes, the oscillation frequency changes. Therefore, it is a technical issue to prevent the oscillation frequency of the oscillation circuit from changing due to temperature changes.

In this implementation, the oscillation frequency is kept constant regardless of temperature changes by connecting a capacitor C1° in parallel to the insertion inductance Ll11 shown in FIG. 1, which serves to expand the oscillation frequency.

The temperature compensation operation using the insertion inductance will be explained below. In FIG. 1, the impedance 2 formed by the insertion inductance L0 and the capacitor C1° connected in parallel with it is.

(x>ulLc) The temperature coefficient α2 of this impedance 2 is determined.

When the above impedance 2 is totally differentiated with respect to the variable T indicating temperature.

obtain a relationship.

Also, we obtain the relationship from the above equation. Here, the insertion inductance L1° itself is 1. The coefficient of variation is αL1°, the temperature compensation capacitor C1
Assuming that the temperature coefficient of ° is αc1°, each coefficient is calculated using the following formula % Formula % The temperature coefficient α2 of the impedance 2 described above is determined using the above α$2 to qth equations.

get.

When the connected capacitor C8.degree. satisfies the temperature coefficient having the relationship expressed by equation (c), the oscillation frequency due to the degree change of the insertion inductance is moderated.

That is, the insertion inductance L. Regardless of the selection of the material of the core used for the oscillation circuit, fluctuations in the oscillation frequency of the oscillation circuit can be prevented by connecting the capacitor C1° in parallel with the inductance L. For this reason.

When the oscillation circuit shown in FIG. 1 is applied to an FM modulator, FSK data transmission, etc. that require center-to-center wave number stability, malfunctions can be prevented.

FIG. 7 shows a temperature compensation capacitor CI inserted into the inductance L1° for expanding the oscillation frequency range in the embodiment of the invention shown in FIG. This shows the temperature compensation characteristics when connected. In the figure, 4. The line shows the temperature characteristics when a temperature compensation capacitor C1° is inserted. As can be seen from this characteristic diagram, the oscillation frequency is lower when temperature compensation is performed using capacitor CIG, compared to the temperature characteristics when temperature compensation is not performed, as shown by the broken line, when temperature compensation capacitor C1° is not connected. Temperature changes become gentler, and the temperature dependence of the oscillation frequency is improved.

〔Effect of the invention〕

As described above, according to the present invention, in an oscillation circuit using a crystal resonator, fluctuations in the oscillation local wave number can be suppressed even if the element value changes due to temperature changes in the inserted inductance that expands the oscillation frequency range. Oscillation 1c that can be done!
].

Note that this invention is widely and generally applied to oscillation circuits in which an inductance is inserted to expand the oscillation frequency range of an oscillation circuit using a crystal resonator, and the single oscillation circuit form is limited to Colpitts oscillation circuits. First, it can be widely applied to oscillation circuits using crystal resonators.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing one embodiment of an oscillation circuit according to the present invention, FIGS. 2 and 4 are equalization circuit diagrams of a crystal resonator,
3, 5, and 6 are characteristic diagrams showing the characteristics of a crystal resonator, and FIG. 7 is a characteristic diagram of an oscillation circuit according to an embodiment of the present invention. ×1...Iceberg J Arrow J 'J, L+o...I〉Taftan, Li ・ °Bakukuku Wolf (Do, D+o...
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Claims (1)

[Scope of Claims] In an oscillation circuit having a crystal resonator in a feedback path, an inductance for expanding the oscillation frequency range is connected in series with the crystal resonator, a capacitor is connected in parallel to this inductance, and the inductance An oscillation circuit characterized in that fluctuations in oscillation frequency due to fluctuations in element values are suppressed.