JP2002171130A - Voltage control oscillator circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a voltage control oscillator circuit which can obtain a stable oscillation output even if frequencies are increased and an area of oscillation frequencies is widened. SOLUTION: A voltage control oscillator circuit comprises a resonance circuit X which contains resonance means, a variable capacitance diode which is connected in parallel to the resonance means, a negative resistor circuit part Y which contains an oscillating transistor Q1 which adjusts oscillation conditions depending on resonance frequencies of the resonance circuit, an amplifying transistor Q2 for amplifying an oscillation signal, and an amplifier circuit part Z which contains a power source voltage terminal for supplying a DC bias current to the amplifying transistor and the oscillating transistor. In the oscillating transistor Q1, its emitter is connected to a bias resistor R3 which prescribes a DC bias current, and an impedance control circuit 23 which comprises a capacitance component C7 and inductor components L2, L3 is disposed between the bias resistor R3 and a ground.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a voltage controlled oscillation circuit capable of stably outputting an oscillation frequency in a high frequency range.

[0002]

2. Description of the Related Art Conventionally, transmission oscillators and reception local oscillators are frequently used in mobile communication devices and other communication devices. Such an oscillator is constituted by a voltage-controlled oscillation circuit capable of linearly varying the oscillation frequency range by a control voltage supplied from the outside.

[0003] In recent years, the frequency variable region (oscillation frequency) of the oscillation output of the voltage controlled oscillation circuit has been increasing in frequency. For example, the frequency variable range is from about 2.2 GHz to about 2.2 GHz.
4 GHz: Higher frequency and wider band, such as a variable range of 0.2 GHz.

Conventionally, as shown in FIG. 2, a voltage controlled oscillation circuit has been constituted by a resonance circuit section, a negative resistance circuit section, and an amplification circuit section. The resonance circuit portion X mainly includes a strip line SL serving as resonance means, a variable capacitance diode DV, and various capacitors C1, C3, and C4.

Here, the LC resonance circuit 11 for determining the resonance frequency of the resonance circuit section is composed of a strip line L1, a variable capacitance diode DV, and capacitors C1 and C2.

The negative resistance circuit section 12 includes an oscillation transistor Q1, various capacitors C4 to C7, various resistances R1 to R7.
And 3.

[0007] The amplifying circuit section is composed of amplifying means centered on an amplifying transistor, a capacitor and a resistor, and output circuit means centered on a capacitor and an inductance element. The DC bias current is supplied from the collector of the transistor for amplification via an inductor element, and further supplied to the transistor Q1 for oscillation.

In such an oscillating circuit, if the collector of the oscillating transistor Q1 is AC grounded via the capacitor C6, the impedance seen from the base becomes negative, and resonance occurs at the base of the oscillating transistor Q1. If the circuit section is connected via a coupling capacitor C3 and the other end is grounded, this circuit has an amplitude characteristic of the resonance circuit section, a negative gain of the transistor of 1 or more, and a negative phase angle between the resonance circuit and the transistor. It oscillates at a frequency that satisfies the condition that the sum is 2nπ (n is an integer).

The oscillation output amplified by the amplifying transistor is output from the output terminal of the collector.

In order to improve the C / N characteristics of the voltage controlled oscillation circuit, a bias resistor R3 is connected to the emitter of the transistor Q1, and a capacitor C7 and an inductance L2 are connected to one end of the bias resistor R3.
Are connected, and each is connected to the ground potential. The circuit constant of the parallel resonance circuit 13 including the inductance L2 and the capacitor C7 is controlled so that the impedance in the oscillation frequency band (high frequency) of the voltage controlled oscillation circuit is increased. That is, the frequency of the oscillation output of the voltage controlled oscillation circuit is approximated to the resonance frequency of the parallel resonance circuit 13.

[0011]

However, the above-mentioned conventional voltage controlled oscillator has the following problems.

The inductance L2 and the capacitor C7
In the parallel resonance circuit 13 composed of the above, the impedance on the ground side of the bias resistor R3 of the oscillation circuit can be increased at the resonance frequency of the parallel resonance circuit 13, and the C / N characteristic is improved at that frequency. Although it can be performed, usually, the voltage controlled oscillation circuit needs a good oscillation state within a predetermined frequency range, and it is difficult for the parallel resonance circuit 13 to uniformly increase the impedance in the oscillation frequency band. .

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and has as its object to provide a voltage-controlled oscillator capable of obtaining an oscillation output excellent in C / N characteristics even at a higher frequency and a wider oscillation frequency. Circuit.

[0014]

According to the present invention, there is provided a resonance circuit section including resonance means, a variable capacitance diode connected in parallel with the resonance means, and a resonance circuit connected to the resonance circuit section, the resonance circuit section comprising: A negative resistance circuit section including an oscillation transistor for adjusting an oscillation condition based on a frequency and outputting an oscillation signal; an amplification transistor connected to the negative resistance circuit section for amplifying the oscillation signal; A voltage-controlled oscillator circuit comprising a transistor for power supply and a power supply voltage terminal for supplying a DC bias current to the transistor for oscillation, wherein the transistor for oscillation has a bias resistor for defining a DC bias current at its emitter. And a series resonance circuit section of a capacitance component and a first inductance component between the bias resistor and the ground potential. The impedance control circuit comprising a second inductance component connected in parallel to the road section is arranged.

The circuit of the voltage controlled oscillator according to the present invention will be described with reference to the circuit diagram of FIG. According to the above invention, the impedance control circuit section formed by the inductances L2 and L3 and the capacitor C7 is connected between the bias resistor R3 and the ground potential. Specifically, a series resonance circuit section is formed by the capacitance component of the capacitor C7 and the inductance L3, and the inductance L2 is connected in parallel to the series resonance circuit section. For this reason, it is possible to uniformly increase the impedance on the ground potential side of the bias resistor R3 of the oscillation circuit in the oscillation frequency band of the voltage controlled oscillation circuit. This is the traditional LC
The impedance characteristics can be improved and made uniform in a predetermined frequency band as compared with the case where the parallel resonance circuit is constituted alone. That is, the reflection coefficient can be increased over the entire frequency band of the oscillation output of the voltage controlled oscillation circuit, and the C / N characteristics can be uniformly and generally improved over the entire oscillation frequency range.

Further, since the impedance control circuit uniformly improves the impedance in a predetermined oscillation frequency band, the amount of positive feedback of the oscillation circuit can be uniformly increased in the oscillation frequency band.

As a result, a voltage controlled oscillation circuit that can obtain an oscillation output with excellent C / N characteristics even when the frequency is increased and the oscillation frequency is widened.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a voltage controlled oscillator according to the present invention will be described with reference to the drawings.

FIG. 1 is an equivalent circuit diagram of the voltage controlled oscillation circuit of the present invention. Note that the overall operation of each circuit section of the resonance circuit section, the negative resistance circuit section, and the amplifier circuit section Z is substantially the same as that shown in FIG.
As described above.

The resonance circuit X mainly includes a strip line L1, a variable capacitance diode DV, an inductance element L4, and capacitors C1 to C2 and C8, which are resonance means. The resonance circuit 21 is configured by the strip line L1, the variable capacitance diode DV, and the capacitors C1 and C2.

The negative resistance circuit section Y includes an oscillation transistor Q1, capacitors C4 to C7 and C9, various resistors R1.
To R3, and inductance elements L2 and L3. In particular, the impedance control circuit section 23 is connected to the emitter of the oscillation transistor Q1 between the emitter and the ground potential via the bias resistor R3. This impedance control circuit section 23 is composed of two inductance elements L2 and L3 and a capacitor C7.

Further, the amplifying circuit section Z comprises an amplifying transistor Q2 serving as amplifying means, capacitors C9 to C12, various resistors R4 and an inductance element L5.

In such a voltage controlled oscillation circuit, the collector of the oscillation transistor Q1 of the negative resistance circuit section Y is AC grounded via the capacitor C6. This capacitor C6 also serves as a capacitor for the emitter input of the amplifying transistor Q2.

The impedance seen from the base of the oscillation transistor Q1 becomes negative. If the resonance circuit X is connected to this base via the coupling capacitor C3 and the other end is grounded, the resonance circuit X Oscillation occurs at a frequency that satisfies the condition that the amplitude characteristic and the negative gain of the transistor are 1 or more and the sum of the negative phase angles of the resonance circuit portion X and the oscillation transistor Q1 is 2nπ (n is an integer).

This oscillation signal is supplied to the amplification transistor Q2, where it is amplified and oscillated and output from the output terminal.

Here, the DC bias current supplied to the power supply voltage terminal is supplied to the collector of the amplification transistor Q2 and supplied to the oscillation transistor Q1. Specifically, the current flows to the ground potential via the power supply terminal, the inductance element L5, the amplification transistor Q2, the oscillation transistor Q1, the bias resistor R3, and the impedance control circuit unit 23.

In the present invention, the impedance control circuit section 23 is disposed between the bias resistor R3 and the ground potential, and includes a series circuit section in which the inductance element L3 and the capacitor C7 are connected, And an inductance element L2 in a parallel relationship. Therefore, in this impedance control circuit 23, L
In the parallel circuit of L2 and the series resonance circuit composed of 3 and C7, by adjusting the respective resonance frequencies,
FIG. 3 shows the impedance characteristic of the impedance control circuit 23. That is, in the variable frequency range of the oscillation frequency of the voltage controlled oscillation circuit (the minimum frequency is f1, the center frequency f2, and the maximum frequency f3), high impedance and uniformity are achieved in all frequency regions. That is, in order to make the impedance uniform in the variable frequency region of the voltage controlled oscillation circuit, the reflection coefficient of the high frequency signal in the impedance control circuit 23 is made uniform in the variable frequency band. For this reason, C of the voltage controlled oscillator directly related to the reflection coefficient
The / N characteristic is extremely stabilized in the entire frequency band of the voltage controlled oscillation circuit.

As shown in FIG. 2, in a conventional parallel resonance circuit including an inductance element L2 and a capacitor C7, a bias resistor R3 is used, as in the prior art shown in FIG. Is the largest. That is, in the frequency band of the voltage controlled oscillation circuit, for example, the impedance differs between the center frequency F2 and the minimum frequency f1 and the maximum frequency f3, so that uniformity cannot be obtained. Therefore, the reflection coefficient of the high-frequency signal in the parallel resonance circuit 13 varies depending on the oscillation frequency.
The / N characteristic becomes unstable and the oscillation output becomes unstable depending on the oscillation frequency.

[0028]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The inventor of the present invention has an impedance control circuit 23 of the present invention connected to a bias resistor R3 and a ground potential;
The configuration with the conventional parallel resonance circuit 13 was set as follows. For example, in the conventional parallel resonance circuit 13, an inductance L2 having a certain electrical length and a capacitor C7
Is set to 1.5 pF, and the resonance frequency is set to 3600 MHz.
z. At this time, as the impedance characteristics of the implementation,
In the variable frequency range of the oscillation frequency of the voltage controlled oscillation circuit, the minimum frequency f1 is 3300 MHz and the impedance is 150
Ω, the center frequency f2 was 3600 MHz, the impedance was 1400 Ω, the maximum frequency f3 was 3900 MHz, and the impedance was 140 Ω. On the other hand, for example, in the impedance control circuit 23 according to the present invention, the value of the capacitor C7 is set to 0.5 pF for the strip lines L2 and L3 having different electric lengths, and the resonance frequency is set to 3600 MHz. At this time, as the implemented impedance characteristics, the minimum frequency f1 is 3300 MHz, the impedance is 370Ω, and the center frequency f2 is 3600 MHz in the variable frequency range of the oscillation frequency of the voltage controlled oscillation circuit.
z, the impedance is 520Ω, and the maximum frequency f3 is 39.
At 00 MHz, the impedance was 360Ω. That is, in the present invention, a stable characteristic impedance can be obtained in the variable frequency band of the oscillation frequency of the voltage controlled oscillation circuit.

The circuit constant of the impedance control circuit 23 may be changed according to the bandwidth of the variable frequency band of the voltage controlled oscillation circuit so that a stable impedance can be obtained in the oscillation frequency band. For example, to shift the entire stable impedance of the impedance control circuit 23 to the lower frequency side, for example, the electrical length of the inductance L2 may be increased. Further, in order to shift the whole to a higher frequency side, for example, the electrical length of the inductance L2 may be shortened. Further, in order to widen the band of the uniformized impedance, for example, C7 may be reduced and the electrical length of the inductance L3 may be increased.

The present invention is applicable to all oscillators using Colpitts circuits.

In the present invention, the inductance L
For 2, L3, an element having an inductor component can be used. For example, a strip line, a microstrip line, a chip inductor element, or the like can be actually used. Further, the above-described voltage-controlled oscillation circuit relates to the configuration of the amplifier circuit portion Z. However, as another resonance portion of the voltage-controlled oscillation circuit, that is, as a resonance means of the resonance circuit portion X, a capacitor and a strip line are used. Or a microstrip, or a dielectric resonator may be used as resonance means. Further, the configuration of the negative resistance circuit section Y may be changed according to various purposes.

[0032]

According to the voltage controlled oscillation circuit of the present invention, the bias resistor for defining the DC bias of the oscillation transistor includes:
Set the impedance to the desired oscillation frequency band (between f1 and f3)
Is connected to an impedance control circuit that can make the impedance uniform. Therefore, the impedance can be increased in a stable state in the entire frequency band of the oscillation output, and the positive feedback amount of the oscillation circuit can be uniformly increased.
The C / N characteristics are improved.

[Brief description of the drawings]

FIG. 1 is a circuit diagram of a voltage controlled oscillation circuit according to the present invention.

FIG. 2 is a circuit diagram of a conventional voltage controlled oscillation circuit.

FIG. 3 is a characteristic diagram showing impedance characteristics in an impedance control circuit unit according to the present invention.

FIG. 4 is a characteristic diagram showing characteristics of impedance characteristics in a conventional parallel resonance circuit unit.

[Explanation of symbols]

 X: Resonant circuit section Y: Negative resistance circuit section Z: Amplifying circuit section Q1: Oscillating transistor Q2: Amplifying transistor L2: Inductance element L3: Inductance element C7: Capacitor

Claims (1)

[Claims] 1. A resonance circuit unit including a resonance unit, a variable capacitance diode connected in parallel to the resonance unit, and a resonance circuit unit connected to the resonance circuit unit, wherein an oscillation condition is adjusted based on a resonance frequency of the resonance circuit unit. And a negative resistance circuit portion including an oscillation transistor that outputs an oscillation signal, an amplification transistor connected to the negative resistance circuit portion, and amplifying the oscillation signal, an amplification transistor, and the oscillation transistor. A voltage-controlled oscillation circuit comprising a power supply voltage terminal for supplying a DC bias current, and an amplification circuit including a power supply voltage terminal. Between the capacitor and the first inductance component, and a second resonance circuit connected in parallel to the series resonance circuit. A voltage-controlled oscillation circuit, comprising an impedance control circuit section comprising: