JP2002135049A - Voltage controlled oscillator and communication machine using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a voltage controlled oscillator whose deterioration of a characteristic can be prevented and which can be miniaturized and to provide a communication machine. SOLUTION: The voltage controlled oscillator 10 is provided with a resonance circuit 11, an oscillation circuit 12 oscillating by the resonance frequency of the resonance circuit 11, an amplification circuit 13 amplifying the oscillation signal of the oscillation circuit 12, a control terminal 14 applying control voltage to the resonance circuit 11, the power terminal 15 of the oscillation circuit 12, the power terminal of the amplification circuit 13 and an output terminal 17 outputting a high frequency signal. The resonance circuit 11 and the oscillation circuit 12 are connected through a coupling capacitor C1 and the oscillation circuit 12 and the amplification circuit 13 through a coupling capacitor C2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a voltage controlled oscillator and a communication device using the same, and more particularly, to a voltage controlled oscillator for generating high frequency signals in a plurality of different frequency bands and a communication device using the same.

[0002]

2. Description of the Related Art In recent years, a plurality of communication systems using different frequency bands, for example, GS using a 900 MHz band
M (Global System for Mobile communications), 1.
DCS (Digital Cellular System) using 8 GHz band
m) PCS (Personal Commun) using 1.9 GHz band
ication Services) are widely used. Along with this,
It is becoming possible to cope with these plural communication systems with one communication device. In this case, a high-frequency oscillation circuit such as a voltage controlled oscillator constituting a local oscillation circuit of the communication device needs to generate signals in a plurality of different frequency bands according to the communication system.

FIG. 6 is a circuit diagram of a conventional voltage controlled oscillator for generating high frequency signals in two discrete different frequency bands. The voltage controlled oscillator 50 is disclosed in Japanese Unexamined Patent Application Publication No. 10-1637.
No. 50, which discloses first and second resonance circuits 51a and 51b, and first and second oscillation circuits 52a and 52a which oscillate at the resonance frequency of the first and second resonance circuits 51a and 51b. 52b, the first and second oscillation circuits 52
a, an amplifier circuit 53 for amplifying the oscillation signals of the first and second resonance circuits 51a, 51b, a control terminal 54 for applying a control voltage to the first and second resonance circuits 51a, 51b, A power supply terminal 56 of the amplifier circuit 53,
An output terminal 57 for outputting a high-frequency signal is provided.

The first and second resonance circuits 51a, 51b are:
Variable capacitance diodes D51a and D51b, inductors L51a and L51b constituting a resonator, frequency adjusting capacitors C51a and C51b, and inductors L52a and L5.
2b and capacitors C52a and C52b. The first and second oscillation circuits 52a and 52b include a transistor Q51.
a, Q51b, capacitors C53a to C55a, C53
b to C55b, resistors R51a to R53a, R51b to R
53b. The first and second resonance circuits 51a, 51a,
51b and the first and second oscillation circuits 52a and 52b are coupling capacitors C56a and C56b, and the first and second oscillation circuits 52a and 52b and the amplification circuit 53 are coupling capacitors C5.
7a and C57b.

Next, the operation of the voltage controlled oscillator 50 shown in FIG. 6 will be described. When power is supplied to the power supply terminal 55a of the first oscillation circuit 52a and power is not supplied to the power supply terminal 55b of the second oscillation circuit 52b, only the first oscillation circuit 52a operates and the second oscillation circuit 52b does not operate. . Further, by supplying power to the amplifier circuit 53 from the power supply terminal 56, the amplifier circuit 53 operates. In this case, the first oscillation circuit 52a
A high frequency signal having a frequency corresponding to the DC voltage applied from the control terminal
7 is output. Conversely, when power is supplied to the power supply terminal 55b of the second oscillation circuit 52b and power is not supplied to the power supply terminal 55a of the first oscillation circuit 52a, A high-frequency signal having a frequency corresponding to the DC voltage applied from the control terminal 54 is output from the output terminal 57.

The above operation is performed by the voltage controlled oscillator 50
A low-capacitance coupling capacitor C57a, between the first and second oscillating circuits 52a, 52b constituting the voltage controlled oscillator 50 and the amplifying circuit 53 so as not to cause a frequency fluctuation with respect to an impedance fluctuation at the output terminal 57 of the voltage controlled oscillator 50. C57
This is made possible by the rough coupling in b. For example, the first
When the oscillation circuit 52a operates and the second oscillation circuit 52b does not operate, most of the signals oscillated by the first oscillation circuit 52a and passing through the coupling capacitor C57a flow into the amplification circuit 53, The second oscillation circuit 52b that is not operating hardly flows through the coupling capacitor C57b. That is, since the coupling capacitors C57a and C57b are capacitors set for coarse coupling, when compared with the input terminal of the amplifier circuit 53,
Since the impedance is very high, most of the oscillation signal from the first oscillation circuit 52a flows into the amplifier circuit 53 having a low impedance. This is the same when the second oscillation circuit 52b oscillates and the first oscillation circuit 52a is stopped. As a result, the first and second oscillation circuits 52a and 52b do not affect each other and the two first and second oscillation circuits 52a and 52b do not affect each other.
52b can be connected to the amplifier circuit 53.

[0007]

However, according to the above-mentioned conventional voltage controlled oscillator, a plurality of oscillation circuits corresponding to different frequency bands are required, so that the voltage controlled oscillator tends to be large.

If the coupling capacitor connecting the plurality of oscillation circuits and the amplifier circuit deteriorates in characteristics, the oscillation signal of the operating oscillation circuit flows into the non-operating oscillation circuit. There is also a problem that characteristics are deteriorated.

SUMMARY OF THE INVENTION The present invention has been made to solve such a problem, and it is possible to prevent deterioration of characteristics and
It is an object of the present invention to provide a voltage-controlled oscillator that can be miniaturized and a communication device using the same.

[0010]

In order to solve the above-mentioned problems, a voltage-controlled oscillator according to the present invention comprises one resonance circuit resonating in a plurality of frequency bands and one oscillation circuit oscillating at the resonance frequency of the resonance circuit. A voltage controlled oscillator comprising a circuit and one amplifier circuit for amplifying an oscillation signal from the oscillation circuit, wherein the resonance circuit reduces a reactance component of the resonance circuit to a plurality of frequency bands. It is characterized by having a function of changing by.

In the voltage controlled oscillator according to the present invention, the resonance circuit includes a first variable capacitance diode and a resonator, and a second variable capacitance diode is connected between one end of the resonator and ground. It is characterized by having done.

Further, in the voltage controlled oscillator according to the present invention, a second variable capacitance diode is connected between the other end of the resonator and the oscillation circuit.

A communication device according to the present invention uses the above-described voltage controlled oscillator.

According to the voltage controlled oscillator of the present invention, since the resonance circuit has a function of changing the reactance component of the resonance circuit within a range corresponding to a plurality of frequency bands, one resonance circuit can be used without using a switching element or the like. The circuit can support a plurality of frequency bands.

According to the communication device of the present invention, since a small voltage-controlled oscillator capable of preventing characteristic deterioration in a plurality of frequency bands is used, a small communication device having good communication characteristics in a plurality of frequency bands is provided. Can be configured.

[0016]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a circuit diagram of a first embodiment of the voltage controlled oscillator according to the present invention. The voltage controlled oscillator 10 includes a resonance circuit 11, an oscillation circuit 12 that oscillates at a resonance frequency of the resonance circuit 11, an amplification circuit 13 that amplifies an oscillation signal of the oscillation circuit 12, and a control terminal 14 that applies a control voltage to the resonance circuit 11. Power supply terminal 1 of the oscillation circuit 12 and the amplification circuit 13
5. It has an output terminal 16 for outputting a high-frequency signal.

The resonance circuit 11 and the oscillation circuit 12 are connected via a coupling capacitor C1, and the oscillation circuit 12 and the amplification circuit 13 are connected via a coupling capacitor C2.

The resonance circuit 11 includes a first variable capacitance diode D11, a second variable capacitance diode D12, an inductor L11 forming a resonator, a capacitor C11, and a resistor R.
11, R12.

The control terminal 14 and the coupling capacitor C
1, a resistor R11 and a parallel circuit including a first variable capacitance diode D11 and an inductor L11 are connected in series. A second variable capacitance diode D12 is provided between one end of the inductor L11, that is, between the control terminal 14 and the ground, and a resistor R1 is provided between the other end of the inductor L11, that is, the coupling capacitor C1 and the ground.
2 are respectively connected.

At this time, the resonance circuit 11 is connected to the first variable capacitance diode D11 and the inductor L11 connected in parallel.
Of the second variable capacitance diode D1
2 controls the reactance component of the resonance circuit 11.

The oscillation circuit 12 has a transistor Q1, an inductor L1, capacitors C3 to C5, and resistors R1 to R3. At this time, the base of the transistor Q1 is connected to the resonance circuit 11 via the coupling capacitor C1, the emitter is connected to the amplifier circuit 13 via the coupling capacitor C2, and the collector is connected to the power supply terminal 15 via the inductor L1.

The amplifier circuit 13 has a transistor Q2, an inductor L2, capacitors C6 and C7, and resistors R4 to R6. At this time, the base of the transistor Q2 is connected to the oscillation circuit 12 via the coupling capacitor C2, and the collector is connected to the output terminal 16 via the capacitor C7.

Next, the operation of the voltage controlled oscillator 10 will be described. The voltage Vc is supplied from the control terminal 14 to change the capacitance of the second variable capacitance diode D12. At this time, the reactance component X of the resonance circuit 11 is represented by X = X ₁ −X ₂ X ₂ = 1 / 2π · f · C _d2 .

It should be noted, X ₁ is a reactance component which is determined by the inductor L11 and the first variable capacitance diode D11, X ₂ is the reactance component of the second variable capacitance diode D12, f is the frequency, C _d12 is the second This is the capacitance of the variable capacitance diode D12.

That is, the reactance component X of the voltage controlled oscillator 10 includes a reactance component X ₁ determined by the inductor L11 and the first variable capacitance diode D11,
Reactance component X of second variable capacitance diode D12
Expressed as the difference from ₂ .

Therefore, by increasing the change of the reactance component X2 of the _second variable capacitance diode D12 with respect to the voltage Vc supplied to the control terminal 14, the voltage-controlled oscillator 10 responds to the voltage Vc supplied to the control terminal 14. The reactance component X can be greatly changed.

FIG. 2 is a diagram showing the relationship between the frequency f and the reactance component X of the resonance circuit 11 in the voltage controlled oscillator of FIG. The solid line indicates the voltage controlled oscillator 1 of the first embodiment.
In the case of 0 (FIG. 1), a broken line
(FIG. 6).

From this figure, in the case of the voltage controlled oscillator 10 of the first embodiment, the voltage Vc supplied to the power supply terminal 15
It can be seen that the reactance component X of the resonance circuit 11 can be largely changed, and as a result, the frequency f at which the resonance circuit 11 resonates can be discretely set to f1 and f2. In this case, the two discrete frequency bands f1 and f2 are 900 MHz corresponding to GSM, respectively.
z, which corresponds to 1.8 GHz corresponding to DCS.

FIG. 3 is a circuit diagram of a voltage controlled oscillator according to a second embodiment of the present invention. The voltage controlled oscillator 20 is different from the voltage controlled oscillator 10 (FIG. 1) of the first embodiment in that the resonance circuit 21 includes two second variable capacitance diodes D12a and D12b.

That is, the second variable capacitance diode D12a is provided between the control terminal 14 which is one end of the inductor L11 and the ground, and the second variable capacitance diode D12b is provided between the other end of the inductor L11 and the coupling capacitor C1. Connected respectively.

In addition, a capacitor C12 is connected between the first variable capacitance diode D11 and the second variable capacitance diode D12b, and a connection point between the first variable capacitance diode D11 and the capacitor C12 is connected to the ground. The resistor R13 is connected therebetween.

At this time, the resonance circuit 21 is formed by the first variable capacitance diode D11 and the inductor L11 connected in parallel.
Of the second variable capacitance diode D1
The reactance components of the resonance circuit 21 are controlled by 2a and D12b.

In the case of the voltage controlled oscillator 20 according to the second embodiment, since there are two second variable capacitance diodes connected in series to the inductor L11, the reactance component X of the resonance circuit 21 is expressed as follows: X ₁ −X _2a −X _2b X _2a = 1 / 2π · f · C _d12a X _2b = 1 / 2π · f · C _d12b

X _2a and X _2b are the reactance components of the second variable capacitance diodes D12a and D12b, f is the frequency, and C _d12a and C _d12b are the second variable capacitance diodes D12.
a, D12b are the capacities.

That is, the reactance component X of the voltage controlled oscillator 20 is a reactance component X ₁ determined by the inductor L11 and the first variable capacitance diode D11,
It is represented by the difference between the reactance components X _2a , X _{2b of} the second variable capacitance diodes D12a, D12b, and changes more greatly.

Therefore, the reactance component X of the voltage controlled oscillator 20 with respect to the voltage Vc supplied to the control terminal 14 can be changed more greatly than the voltage controlled oscillator 10 (FIG. 1) of the first embodiment. Thus, it is possible to set a large number of discrete frequencies at which the resonance circuit 21 resonates.

FIG. 4 is a circuit diagram of a voltage controlled oscillator according to a third embodiment of the present invention. The voltage controlled oscillator 30 is different from the voltage controlled oscillator 20 (FIG. 3) of the second embodiment in that a first variable capacitance diode D11 for determining a resonance frequency is connected in series with an inductor L11. .

That is, the first variable capacitance diode D11 is connected between the coupling capacitor C1, which is the other end of the inductor L11, and the ground.

In the case of the voltage controlled oscillator 30 of the third embodiment, the first variable capacitance diode D11 and the inductor L11 are connected in series. It not only determines the resonance frequency but also controls the reactance component of the resonance circuit 31.

Therefore, the reactance component X of the voltage controlled oscillator 30 with respect to the voltage Vc supplied to the control terminal 14 can be changed more greatly than the voltage controlled oscillator 20 (FIG. 3) of the second embodiment. In addition, it is possible to set many discrete frequencies at which the resonance circuit 31 resonates.

According to the voltage controlled oscillator of the above embodiment,
Since the resonance circuit has a function to change the reactance component of the resonance circuit in a range corresponding to a plurality of discrete frequency bands, one resonance circuit can support a plurality of frequency bands without using a switching element. Becomes possible. Therefore, a small-sized voltage controlled oscillator that can be used for a plurality of different frequency bands can be provided. Incidentally, the mounting area of the voltage controlled oscillator (FIG. 1) of the first embodiment is reduced by about 50% compared to the voltage controlled oscillator 50 (FIG. 6) of the conventional example.

Also, since one resonance circuit resonates in a plurality of discrete frequency bands, it is possible to prevent a signal from flowing from the oscillation circuit to the resonance circuit in each frequency band. Therefore, it is possible to prevent the characteristic deterioration of the voltage controlled oscillator in a plurality of frequency bands.

Further, since there is only one resonance circuit, it is possible to cope with a plurality of different frequency bands and to suppress current consumption. Incidentally, the total current consumption is about 6 mA in the voltage controlled oscillator (FIG. 1) of the first embodiment, and is about 25 (%) compared to about 8 mA in the voltage controlled oscillator 50 (FIG. 6) of the conventional example. It was reduced.

In addition, since it is not necessary to design a resonance circuit in accordance with a plurality of different frequency bands, the design time can be shortened, components can be shared, and the manufacturing cost can be reduced.

FIG. 5 is a block diagram of one embodiment according to the communication device of the present invention. The communication device 40 includes an antenna 41, a duplexer 42, amplification units 43a and 43b, a mixing unit 44a,
44b, a voltage controlled oscillator 45, a PLL control circuit 46,
It includes a low-pass filter 47, a temperature-compensated crystal oscillation circuit 48, a transmitting unit Tx, and a receiving unit Rx.

The PLL control circuit 46 receives the output signal of the voltage controlled oscillator 45, compares the phase with the oscillation signal of the temperature compensated crystal oscillation circuit 48, and outputs a control voltage so as to have a predetermined frequency and phase. .

The voltage-controlled oscillator 45 receives the control voltage via a low-pass filter 47 at a control terminal, and outputs a high-frequency signal corresponding to the control voltage. This high-frequency signal is supplied to the mixing units 44a and 44b as local oscillation signals.

The mixing section 44a mixes the intermediate frequency signal output from the transmission section Tx and the local oscillation signal and converts the mixed signal into a transmission signal. This transmission signal is amplified by the amplifier 43a,
The light is radiated from the antenna 41 via the duplexer 42.

The received signal from the antenna 41 is amplified by the amplifier 43b via the duplexer 42. Mixing section 44
b mixes the received signal amplified by the amplifier 43b with the local oscillation signal from the voltage controlled oscillator 45 and converts it into an intermediate frequency signal. This intermediate frequency signal is subjected to signal processing in the receiving unit Rx.

The voltage controlled oscillator 45 in such a communication device is replaced by the voltage controlled oscillator 1 shown in the first to third embodiments.
0, 20, and 30 are used.

According to the communication device of the above-described embodiment, since a small voltage-controlled oscillator capable of preventing characteristic deterioration in a plurality of frequency bands is used, a small communication device having good communication characteristics in a plurality of frequency bands is used. Machine can be configured.

The configuration of the oscillation circuit and the amplification circuit described in the voltage controlled oscillator of the above-described embodiment is a general circuit configuration, and a circuit of another configuration can realize the voltage controlled oscillator of the present invention. It is possible.

Further, it is also possible to integrate the voltage controlled oscillator of the above-described embodiment into one module.

Further, a combination of a plurality of discrete frequency bands includes a European DCS (Digital Cellular System:
1.8GHz band) and GSM (Global System for Mobile)
communications: 900MHz band) North American PCS (P
Personal Communication Services: 1.9 GHz band and AMPS (Advanced Mobile Phone Services: 800)
MHz), DECT (Digital European Cordless Tele)
phone: 1.9 GHz band) and GSM, Japanese PHS (P
ersonal Handy-phone System: 1.9 GHz) and PD
Combination with a C (Personal Digital Cellular: 800 MHz band) system.

[0056]

According to the voltage controlled oscillator of the present invention, since the resonance circuit has a function of changing the reactance component of the resonance circuit in a range corresponding to a plurality of frequency bands, the resonance circuit can be used without using a switching element. One resonance circuit can handle a plurality of frequency bands. Therefore, a small-sized voltage controlled oscillator that can be used for a plurality of different frequency bands can be provided.

Further, since one resonance circuit resonates in a plurality of frequency bands, it is possible to prevent a signal from flowing from the oscillation circuit to the resonance circuit in each frequency band. Therefore, it is possible to prevent the characteristic deterioration of the voltage controlled oscillator in a plurality of frequency bands.

Further, since there is only one resonance circuit, it is possible to cope with a plurality of different frequency bands and to suppress current consumption.

Further, since it is not necessary to design a resonance circuit in accordance with a plurality of different frequency bands, the design time can be shortened, components can be shared, and the manufacturing cost can be reduced.

According to the communication device of the present invention, since a small-sized voltage-controlled oscillator capable of preventing characteristic deterioration in a plurality of frequency bands is used, a small-sized communication device having good communication characteristics in a plurality of frequency bands is provided. Can be configured.

[Brief description of the drawings]

FIG. 1 is a circuit diagram of a first embodiment according to a voltage controlled oscillator of the present invention.

FIG. 2 is a diagram showing a relationship between a frequency and a reactance component of a resonance circuit in the voltage controlled oscillator of FIG.

FIG. 3 is a circuit diagram of a second embodiment according to the voltage controlled oscillator of the present invention.

FIG. 4 is a circuit diagram of a third embodiment according to the voltage controlled oscillator of the present invention.

FIG. 5 is a block diagram of an embodiment according to the communication device of the present invention.

FIG. 6 is a circuit diagram of a conventional voltage controlled oscillator that generates high frequency signals in two discrete different frequency bands.

[Explanation of symbols]

10, 20, 30 Voltage controlled oscillator 11, 21, 31 Resonant circuit 12 Oscillator circuit 13 Amplifier circuit 40 Communication device D11 First variable capacitance diode D12, D12a, D12b Second variable capacitance diode L11 Resonator (inductor)

Claims (4)

[Claims] 1. One resonance circuit that resonates in a plurality of frequency bands, one oscillation circuit that oscillates at the resonance frequency of the resonance circuit, and one amplification circuit that amplifies an oscillation signal from the oscillation circuit is connected. A voltage-controlled oscillator according to claim 1, wherein said resonance circuit has a function of changing a reactance component of said resonance circuit in a range corresponding to a plurality of frequency bands. 2. The device according to claim 1, wherein said resonance circuit comprises a first variable capacitance diode and a resonator, and a second variable capacitance diode is connected between one end of said resonator and ground. 2. The voltage controlled oscillator according to 1. 3. The voltage controlled oscillator according to claim 2, wherein a second variable capacitance diode is connected between the other end of said resonator and said oscillation circuit. 4. A communication device using the voltage controlled oscillator according to claim 1.