JPH06350336A - Oscillator - Google Patents

Abstract

PURPOSE:To obtain a oscillator used for a quasi-microwave band with a small size, low power consumption, a high output whose phase noise characteristic is excellent. CONSTITUTION:The oscillator in which a resonance circuit 1 is connected to a base of a bipolar transistor(TR) Q1 whose emitter connects to ground via a parallel circuit comprising a resistor R7 and a capacitor C2, whose collector connects to ground via a capacitor C6 and a capacitor C1 is connected between the base and emitter is provided with a field-effect TR Q3 extracting an output of the oscillator. A source of the field-effect TR Q3 is connected to the collector of the bipolar TR Q1, its drain connects to a power supply for supplying a voltage Vcc and a bias supply means 2 controlling a voltage applied to its gate so that the voltage applied to the source from the power supply is always constant is connected between the source and the gate of the TR Q3.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an oscillator used in the quasi-microwave band, for example. Oscillators used in mobile communications using the quasi-microwave band (1 GHz or more) are required to have small phase, low power consumption, high output, and good phase noise characteristics.

[0002]

2. Description of the Related Art FIG. 3 is a block diagram of a conventional example. In the figure, the transistor whose collector is grounded by the capacitor C ₄
The Q ₁ , the resonance circuit 1, and the capacitors C ₁ , C ₂ form a Colpitts type oscillation circuit section, and the oscillation output (
For example, about 1.5GHz) is a capacitor C ₃ , transistor
It is taken out through the buffer amplifier composed of Q ₃ .

In order to reduce power consumption, the transistors Q ₂ and Q ₁ are vertically connected as shown in the figure. The base voltage of each transistor is V _CC and resistors R _{1 to} R ₃
Depends on.

Here, in the quasi-microwave band, the transistor Q ₁ has a significant gain reduction due to feedback due to the capacitance C _CB between the collector and the base and the performance degradation of the transistor itself.
A method of increasing the value of the coupling capacitor C ₃ is used to obtain a predetermined oscillation output.

In this method, a considerably low impedance (impedance viewed from the Q ₂ side) is connected between the connection point of the capacitors C ₁ and C ₂ and the ground, so that the load Q of the oscillation circuit part is lowered. The phase noise characteristic (phase noise per 1 Hz at the point of center frequency f ₀ ± ΔfKHz) deteriorates.

[0006]

As described above, in the quasi-microwave band above 1 GHz, there is a problem that the load Q of the oscillating circuit portion decreases and the phase noise characteristic deteriorates.

If the coupling capacitor C ₃ is made small and the buffer amplifier has two stages, an oscillation output of a required level can be obtained, but this method cannot be taken because the power consumption increases. It is an object of the present invention to provide an oscillator that is small in size, low in power consumption, high in output, and has good phase noise characteristics.

[0008]

FIG. 1 is a block diagram showing the principle of the first aspect of the present invention. In the figure, Q ₁ is a bipolar transistor in which the emitter is grounded through a parallel element of a resistor and a capacitor, the collector is grounded through the capacitor, a resonant circuit is connected to the base, and a capacitor is connected between the base and emitter. ₃ is a field effect transistor.

According to the first aspect of the present invention, the source of the field effect transistor is connected to the collector of the bipolar transistor and the drain thereof is connected to a power source for supplying the voltage V _CC, and the voltage applied to the source is always constant by using the power source. Therefore, the bias supply means for controlling the voltage applied to the gate is connected to the source and the gate.

In the second aspect of the present invention, the bias supply means is a PN
To the power supply via the NPN bipolar transistor in which the emitter of the P bipolar transistor is diode-connected,
The base is connected to the source of the field effect transistor, and the collector is connected to the gate of the field effect transistor and a resistor whose one end is grounded.

[0011]

In FIG. 1, the oscillation circuit portion is an NPN bipolar transistor Q ₁ (hereinafter abbreviated as transistor Q ₁ ),
A field effect transistor Q ₃ (hereinafter, abbreviated as FET Q ₃ ) is used for a buffer amplifier, which is composed of a bias circuit formed of resistors R _{5 to} R ₇ and a resonance circuit 1.

Since the FET Q ₃ and the transistor Q ₁ are vertically connected as shown in the figure, a common current (which is called a common current) flows through the FET Q ₃ and the transistor Q _1. . Further, the bias means 2 uses a feedback bias,
The gate voltage is controlled so that the source voltage of FET Q ₃ is constant.

The common current flowing through the FET Q ₃ and the transistor Q ₁ is the base voltage and the resistance determined by the resistances R ₆ and R _5.
It flows so as to become a constant current by R _7, and the source voltage of FET Q ₃ and the collector voltage of transistor Q ₁ are set by bias means 2, so the common current and the voltage of each part are fixed and oscillate in transistor Q _1. , FET Q ₃ Amplifies and the oscillation output is taken out.

In the present invention, since the FET Q ₃ is used for buffer amplification, since the input impedance of the buffer amplifier is high and the gain is high even in the quasi-microwave band, the coupling capacitor C ₅ should be selected to have a small value. Therefore, the load Q of the oscillator circuit can be maintained high. As a result, it is possible to provide an oscillator having a good phase noise characteristic of the oscillation output.

[0015]

FIG. 2 is a block diagram of the first and second embodiments of the present invention. Where PNP type bipolar transistor 22, NP
The N-type bipolar transistor 21 and the resistor 23 are components of the bias means 2. In addition, the same reference numerals denote the same objects throughout the drawings.

The operation of FIG. 2 will be described below. The parts described in detail in the conventional example will be briefly described, and the part of the present invention will be described in detail. In FIG. 2, a bipolar transistor Q ₁ having a better phase noise characteristic than the FET Q ₃ is used as an oscillating element, a base voltage is set by resistors R ₅ and R ₆ , and a common current is determined by a resistor R ₇ .

On the other hand, FET Q ₃ is used as a buffer amplifier, the source voltage of FET Q ₃ is determined by the base-emitter voltage of transistors 21 and 22, and 23 is a resistor for controlling the gate voltage of FET Q _3. There is a transistor 21,
The bias circuit composed of 22 and resistor 23 operates as follows.

That is, the voltage V _CC is lowered by, for example, 0.7 V in the transistor 21, and is applied to the emitter of the transistor 22,
Furthermore, V _BE of this transistor is reduced by 0.7 V and applied as the source voltage of FET Q ₃ . Now, if the source voltage changes for some reason, the base current of the transistor 22 changes, so the current flowing through the transistor 21 and the transistor 22 changes and flows through the resistor 23. This causes the gate voltage of FET Q ₃ to change.

On the other hand, since the current of the FET Q ₃ is fixed, the current flows through the resistor 23 so that the gate-source voltage V _GS matches the current at that time. Also, the transistor Q ₁
Is used for collector grounding which is grounded at a high frequency by a capacitor C ₆ , and the capacitors C ₁ , C ₂ and the resonance circuit 1 constitute a Colpitts type or Clap type oscillation circuit portion.

The buffer amplifier is used for source grounding which is grounded in a high frequency manner by the capacitor C _{6, and} amplifies high gain and high output power. This buffer amplifier appears as a load to the oscillator circuit part through the coupling capacitor C ₅ , but the FET
Since Q ₃ has a high gain and high impedance input, a sufficient output voltage can be obtained even if the capacitance of the coupling capacitor C ₅ is small.

Therefore, the load Q of the oscillating circuit portion becomes high, and an oscillator having excellent phase noise characteristics can be constructed. According to this embodiment, the bias transistor
By adding only 21, 22 it is possible to realize an oscillator with good phase noise characteristics and high output power even in the quasi-microwave band.

That is, according to the present invention, even in the quasi-microwave band, it is possible to maintain the load Q of the oscillation circuit portion high without lowering the output power, which contributes to the realization of high-performance communication equipment. To do.

[0023]

As described above in detail, according to the present invention, it is possible to provide an oscillator which is small in size, low in power consumption, high in output and excellent in phase noise characteristics.

[Brief description of drawings]

FIG. 1 is a principle configuration diagram of a first present invention.

FIG. 2 is a configuration diagram of the first and second embodiments of the present invention.

FIG. 3 is a configuration diagram of a conventional example.

[Explanation of symbols]

1 Resonance circuit 2 Bias supply means 21 NPN type bipolar transistor 22 PNP type bipolar transistor Q ₁ bipolar transistor Q ₃ field effect transistor

Claims (2)

[Claims] 1. Resonating with a base of a bipolar transistor (Q ₁ ) whose emitter is grounded via a parallel element of a resistor (R ₇ ) and a capacitor (C ₂ ) and whose collector is grounded via a capacitor (C ₆ ). Connect the circuit (1) with a capacitor between the base and emitter.
In the oscillator connected to (C ₁ ), a field effect transistor (Q ₃ ) for extracting the output of the oscillator is provided, and the field effect transistor has a power source for supplying the source to the collector of the bipolar transistor and the drain to the voltage V _CC. And a bias supply means (2) for controlling the voltage applied to the gate so that the voltage applied to the source is always constant by using the power supply. An oscillator characterized in that 2. The bias supply means supplies the emitter of a PNP type bipolar transistor (22) to the power source via a diode-connected NPN type bipolar transistor (21) and the base of the field effect transistor (Q ₃ ). To the source
2. The oscillator according to claim 1, wherein a collector is connected to a gate of the field effect transistor and a resistor (23) whose one end is grounded.