JP2007184811A - Oscillator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve a problem of a conventional oscillator wherein an oscillated frequency of a generated oscillation signal is fluctuated because a combined capacitance associated with a transistor in an oscillation circuit is fluctuated. <P>SOLUTION: The oscillator includes: a Colpitts oscillation circuit including a bipolar transistor and a crystal resonator and an oscillation capacitor connected in parallel with each other between the base of the bipolar transistor and a ground level and for generating an oscillation signal with an oscillation frequency specified by crystal resonator; and a multiple circuit including a coil and a capacitor connected in parallel with each other between the collector of the bipolar transistor and a power supply level, filtering a multiple signal with a multiple frequency being a multiple of the oscillation frequency, attached to the oscillation signal, and including a resistor connected in parallel or series with the coil. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

The present invention relates to an oscillating device used in an optical communication system, a wireless communication system, and the like, and more particularly to an oscillating device that generates a multiplied signal having a multiplied frequency that is a multiplied frequency of an oscillated signal.

As shown in FIG. 5, in the conventional oscillation device OSC100, the bipolar transistor Q
An oscillation signal S100 having an oscillation frequency f (for example, several hundred MHz) generated by an oscillation circuit (Colpitts oscillation circuit) 110 having 110 is amplified by an amplification circuit (base-ground amplification circuit) 120 having a bipolar transistor Q120, A multiplication signal S200 having a multiplication frequency 2f, for example, a double of the oscillation frequency f, which is associated with the oscillation signal S100, is filtered by a multiplication circuit (LC filter) 130 including a coil L110 and a capacitor C140. For this reason, it is filtered again by the first tuning circuit (LC filter) 140 and the second tuning circuit (LC filter) 150.

However, although the coil L110 constituting the multiplier circuit 130 should not have an internal resistance in nature, it actually has an internal resistance r as shown in FIG.
Due to the presence of the internal resistance r, the collector voltage of the bipolar transistor Q120 constituting the amplifier circuit 120 varies. Thus, the bipolar transistor Q12
0 base-collector parasitic capacitance C120bc, base-emitter parasitic capacitance C12
0be, parasitic capacitance C110bc between the base and collector of the bipolar transistor Q110 constituting the oscillation circuit 110, and a capacitor C11 constituting the oscillation circuit 110
There is a problem that the combined capacitance of the four capacitors, that is, the capacitance of 0, varies, and as a result, the oscillation frequency f of the oscillation signal S100 generated by the oscillation circuit 110 varies.

In order to solve the above-described problems, a first oscillation device according to the present invention includes: (1) a bipolar transistor, a crystal resonator provided in parallel with each other between a base and a ground potential of the bipolar transistor; A Colpitts oscillation circuit having an oscillation capacitor, the Colpitts oscillation circuit generating an oscillation signal having an oscillation frequency defined by the crystal resonator, and (2) between a collector of the bipolar transistor and a power supply potential A multiplication circuit having a coil and a capacitor connected in parallel to each other, the multiplication circuit for filtering a multiplication signal accompanying the oscillation signal and having a multiplication frequency that is a multiplication of the oscillation frequency And (3) a resistor connected in parallel to the coil or connected in series.

The second oscillation device according to the present invention includes (1) a bipolar transistor, and a crystal resonator and an oscillation capacitor provided in parallel with each other between the base of the bipolar transistor and the ground potential. A Colpitts-type oscillation circuit that generates an oscillation signal having an oscillation frequency defined by the crystal resonator;
) A multiplier circuit provided in series with each other between the collector of the bipolar transistor and the power supply potential, and a resistor having a coil and a capacitor provided in parallel with each other, and the oscillation signal The multiplication circuit for filtering a multiplication signal having a multiplication frequency which is a multiplication of the oscillation frequency, and the resistor.

According to the first and second oscillation devices according to the present invention, the resistor is connected in parallel or in series to the coil of the multiplier circuit, or the collector of the bipolar transistor and the power supply potential Are connected in series with the multiplier circuit, and thereby the collector voltage of the bipolar transistor is defined by the resistor regardless of the presence of the internal resistance of the coil. As a result, the combined capacitance of the two capacitances, the parasitic capacitance between the base and the collector of the bipolar transistor and the capacitance of the oscillation capacitor, is fixed. It is possible to avoid fluctuations in the oscillation frequency defined by the oscillation vibrator.

  Embodiments of an oscillation device according to the present invention will be described with reference to the drawings.

Example 1
FIG. 1 is a circuit diagram of the oscillation device according to the first embodiment. As shown in FIG. 1, the oscillation device OSC1 according to the first embodiment includes an oscillation circuit 1, an amplification circuit 2, a multiplication circuit 3, a first tuning circuit 4, and a second tuning circuit 5. The oscillation device OSC1 includes a capacitor C1 for removing noise.
The power supply potential Vcc is applied through 0 (bypass capacitor), and is connected to the ground potential GND through a casing (not shown), for example.

The oscillation circuit 1 is a Colpitts type oscillation circuit, and is connected in parallel to an NPN transistor Q1, a crystal resonator Y1 provided between the base of the transistor Q1 and the ground potential GND, and the crystal resonator Y1 in series. Capacitors C1 (oscillation capacitors) and C2 connected to each other and connected to the emitter of the transistor Q1, and a resistor R4 provided between the emitter of the transistor Q1 and the ground potential GND. The resistor R4 determines a current I1 that also defines the operating characteristic (amplification factor) of the amplifier circuit 2 in addition to the operating characteristic (negative resistance) of the oscillation circuit 1. The oscillation circuit 1 generates an oscillation signal S1 having an oscillation frequency f unique to the crystal resonator Y1, and outputs the oscillation signal S1 from the collector of the transistor Q1 to the subsequent amplification circuit 2. The generated oscillation signal S1 is accompanied by a multiplication signal S2 having a multiplication frequency 2f that is a multiplication of the oscillation frequency f, for example, a multiplication by two.

The amplifier circuit 2 is a grounded emitter amplifier circuit, and includes an NPN transistor Q2 and a capacitor C3 provided between the base of the transistor Q2 and the ground potential GND. The collector of the transistor Q2 has a collector voltage of the power supply potential Vcc and the transistor Q2.
Is preferentially defined by a collector voltage resistor RC1 provided between the collectors of the two.
The emitter of the transistor Q2 of the amplification circuit 2 and the collector of the transistor Q1 of the oscillation circuit 1 are connected, that is, the transistor Q2 and the transistor Q1 are cascode-connected, in other words, the amplification circuit 2 and the oscillation circuit. 1 is a power supply potential Vcc and a ground potential G
Cascade connection (series connection) between NDs. A resistor R1 provided between the power supply potential Vcc and the base of the transistor Q2, a resistor R2 provided between the base of the transistor Q2 and the base of the transistor Q1, and a base between the base of the transistor Q1 and the ground potential GND. Resistor R3 defines the base voltage of transistor Q2 and the base voltage of transistor Q1. The amplifier circuit 2 configured as described above amplifies the oscillation signal S1 generated by the oscillation circuit 1 and outputs the amplified signal S1 from the collector of the transistor Q2 to the subsequent multiplication circuit 3.

The multiplier circuit 3 is an LC filter and includes a coil L1 and a capacitor C4 connected in parallel to each other. The coil L1 is provided between the power supply potential Vcc and the collector of the transistor Q2, and the coil L1 does not inherently have an internal resistance r (shown in FIG. 5).
Therefore, the collector voltage of the transistor Q2 may vary depending on the magnitude of the internal resistance r of the coil L1. However, since the collector voltage resistor RC1 (the resistance value of the collector voltage resistor RC1 is one digit or more larger than the resistance value of the internal resistor r) is connected in parallel to the coil L1, the transistor The collector voltage of Q2 is substantially determined only by the collector voltage resistor RC1 while avoiding the influence of the internal resistance r, despite the presence of the internal resistance r of the coil L1. The multiplication circuit 3 having such a configuration includes a multiplication signal S2 having the multiplication frequency 2f defined by the coil L1 and the capacitor C4 among the oscillation signals S1 accompanied by the multiplication signal S2 amplified by the amplification circuit 2. Is filtered, that is, passed, while the oscillation signal S1 is cut off. As a result, the multiplied signal S2 is output to the first tuning circuit 4 in the subsequent stage.

The first tuning circuit 4 is an LC filter similarly to the multiplication circuit 3, and includes a coil L2 and a capacitor C6 connected in parallel to each other. A coupling capacitor C5 is provided between the first tuning circuit 4 and the multiplication circuit 3 so as to cut off the direct current component included in the multiplication signal S2. The first tuning circuit 4 performs waveform shaping on the multiplied signal S2 by filtering the multiplied signal S2 filtered by the multiplier circuit 3 at a multiplied frequency 2f defined by the coil L2 and the capacitor C6.

The second tuning circuit 5 is basically an LC filter similarly to the multiplier circuit 3 and the first tuning circuit 4, and includes a coil L3 and capacitors C8 and C9. The coil L3 is a capacitor C
8 and C9, and capacitors C8 and C9 are connected in series with each other. Between the first tuning circuit 4 and the second tuning circuit 5, a coupling capacitor C7 having a function similar to that of the capacitor C5 is provided. The second tuning circuit 5 shapes the waveform of the multiplied signal S2 by filtering the multiplied signal S2 filtered by the first tuned circuit 4 with a multiplied frequency 2f defined by the coil L3 and the capacitors C8 and C9. The multiplied signal S2 is output from the terminal OUT connected to the connection point of the capacitors C8 and C9.

As described above, in the oscillation device OSC1 of the first embodiment, the collector voltage resistor RC1 is
Since it is connected in parallel to the coil L1 of the multiplier circuit 3 connected to the collector of the transistor Q2 of the amplifier circuit 2, the collector voltage of the transistor Q2 is the internal resistance r of the coil L1.
And is substantially determined only by the collector voltage resistor RC1. As a result, the four combined capacitances of the parasitic capacitance between the collector and base of the transistor Q2, the parasitic capacitance between the base and emitter of the transistor Q2, the parasitic capacitance between the collector and base of the transistor Q1, and the capacitance of the capacitor C1 are fixed. Therefore, it is possible to avoid a situation in which the oscillation frequency f of the oscillation signal S1 generated by the oscillation circuit 1 varies, such as the conventional oscillation device OSC100 (shown in FIG. 5).

Example 2
FIG. 2 is a circuit diagram of the oscillation device according to the second embodiment. The oscillation device OSC2 of the second embodiment is similar to the oscillation device OSC1 of the first embodiment illustrated in FIG.
A first tuning circuit 4, a second tuning circuit 5, resistors R1, R2, R3, a capacitor C
5, on the other hand, unlike the oscillation device OSC1 of the first embodiment, instead of the collector voltage resistor RC1 connected in parallel to the coil L1, it is more precisely connected in series to the coil L1. , A collector voltage resistor RC2 connected in series with the coil L1 between the power supply potential Vcc and the collector of the transistor Q2 (the resistance value is 1 from the resistance value of the internal resistance r of the coil L1).
More than an order of magnitude larger. ).

Similarly to the collector voltage of the transistor Q2 in the first embodiment, the collector voltage of the transistor Q2 in the amplifier circuit 2 is determined by the collector voltage resistor RC2 while avoiding the influence of the internal resistance r of the coil L1. As a result, in the oscillation device OSC2 of the second embodiment, the first embodiment
As in the case of the oscillation device OSC1, the situation in which the oscillation frequency f of the oscillation signal S1 fluctuates can be avoided.

Example 3
FIG. 3 is a circuit diagram of the oscillation device according to the third embodiment. As shown in FIG. 3, the oscillation device OSC3 according to the third embodiment is similar to the oscillation device OSC1 according to the first embodiment and the oscillation device OSC2 according to the second embodiment, and includes the oscillation circuit 1, the amplification circuit 2, and the multiplication circuit 3. , First tuning circuit 4 and second tuning circuit 5
On the other hand, unlike both the oscillators OSC1 and OSC2, the coil L of the multiplier circuit 3
1 instead of the collector voltage resistor RC1 connected in parallel to the coil 1 and the collector voltage resistor RC2 connected in series to the coil L1, the collector voltage resistor RC3 (between the amplifier circuit 2 and the multiplier circuit 3) The resistance value is one digit or more larger than the resistance value of the internal resistance r of the coil L1.
).

The collector voltage of the transistor Q2 of the amplifier circuit 2 is dominant by the collector voltage resistor RC3 while avoiding the influence of the internal resistance r of the coil L1, similarly to the collector voltage of the transistor Q2 in the first and second embodiments. To be determined. As a result, the oscillation device OS of the third embodiment
In C3, similarly to the oscillation device OSC1 of the first embodiment and the oscillation device OSC2 of the second embodiment, a situation in which the oscillation frequency f of the oscillation signal S1 fluctuates can be avoided.

Example 4
FIG. 4 is a circuit diagram of the oscillation device according to the fourth embodiment. As shown in FIG. 4, the oscillation device OSC4 according to the fourth embodiment includes an oscillation circuit 10 corresponding to the oscillation circuit 1 according to the first to third embodiments, and an amplification circuit 20 corresponding to the amplification circuit 2 according to the first to third embodiments. The multiplier circuit 3 corresponding to the multiplier circuit 3 of the first to third embodiments.
0 and the first tuning circuit 4 corresponding to the first tuning circuit 4 and the second tuning circuit 5 of the first to third embodiments.
0, the second tuning circuit 50, the resistors R1, R2, R3 of the first to third embodiments, the capacitor C5,
Resistors R11 and R12 corresponding to C7 and C10, and capacitors C14, C17, and C20 are included. Further, more precisely, between the oscillation circuit 10 and the multiplication circuit 30, the collector of the transistor Q11 of the oscillation circuit 10 and one end of the coil L11 of the multiplication circuit 30 (the end on the side not connected to the power supply potential Vcc). In the meantime, the collector voltage resistor RC4 (resistance value is coil L1
More than one digit larger than the resistance value of the internal resistance r. ).

The collector voltage of the transistor Q11 of the oscillation circuit 10 is similar to the collector voltage of the transistor Q2 of the amplifier circuit 2 of the first to third embodiments, while avoiding the influence from the internal resistance r of the coil L11, and the collector voltage resistor RC4. Determined. Thus, transistor Q11
Because the collector-base capacitance and the combined capacitance of the capacitor C11 are fixedly determined,
Similar to the oscillators OSC1 to OSC3 of the first to third embodiments, it is possible to avoid a situation in which the oscillation frequency f of the oscillation signal S10 varies.

1 is a circuit diagram of an oscillation device according to Embodiment 1. FIG. FIG. 6 is a circuit diagram of the oscillation device according to the second embodiment. FIG. 6 is a circuit diagram of an oscillation device according to a third embodiment. 6 is a circuit diagram of an oscillation device according to Embodiment 4. FIG. The circuit diagram of the conventional oscillation apparatus.

Explanation of symbols

OSC1 ... oscillator, 1 ... oscillator circuit, 2 ... amplifier circuit, 3 ... multiplier circuit, 4 ... first tuning circuit, second tuning circuit ..., RC1 ... collector voltage resistor RC1.

Claims (2)

Between the bipolar transistor and the base and ground potential of the bipolar transistor,
A Colpitts oscillation circuit having a crystal resonator and an oscillation capacitor provided in parallel with each other, the Colpitts oscillation circuit generating an oscillation signal having an oscillation frequency defined by the crystal resonator; ,
A multiplication circuit having a coil and a capacitor provided in parallel with each other between a collector and a power supply potential of the bipolar transistor, the multiplication circuit having a multiplication frequency which is a multiplication of the oscillation frequency and is associated with the oscillation signal The multiplier for filtering the signal;
An oscillation device comprising: a resistor connected in parallel to or in series with the coil. Between the bipolar transistor and the base and ground potential of the bipolar transistor,
A Colpitts oscillation circuit having a crystal resonator and an oscillation capacitor provided in parallel with each other, the Colpitts oscillation circuit generating an oscillation signal having an oscillation frequency defined by the crystal resonator; ,
A multiplier circuit provided in series with each other between a collector of the bipolar transistor and a power supply potential, and a resistor, and a coil and a capacitor provided in parallel with each other. An oscillating apparatus comprising: the multiplication circuit for filtering a multiplication signal having a multiplication frequency which is a multiplication of the oscillation frequency, and the resistor.

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