JPH0555828A - Oscillator - Google Patents

Abstract

PURPOSE:To expand the oscillation frequency band of this oscillator and to reduce its power consumption and the number of circuit parts without varying electric characteristics due to load variation and limiting oscillation outputs. CONSTITUTION:An oscillator is constituted so that an oscillation signal oscillated from an oscillation circuit OS is outputted from a buffer circuit BC the base of a transistor TR1 in the circuit OS and that of a transistor TR2 in the circuit BC are grounded and these transistors TR1, TR2 are mutually connected through an impedance converter L2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an oscillator suitable for being applied to a communication system using high frequency signals such as mobile phones and satellite communications.

[0002]

2. Description of the Related Art FIG. 5 is a circuit diagram of a main part of a conventional oscillator of this type. This oscillator includes a Colpitts oscillator circuit OS and a buffer circuit BC that amplifies an oscillation signal output from the Colpitts oscillator circuit OS.

In the oscillator circuit OS, the power supply terminal V _CC is grounded via the capacitor C ₃ and is also connected to the collector of the oscillation transistor TR ₁ . Transistor
The base of TR ₁ is grounded via a series circuit of capacitors C ₁ and C _2, and a coil L ₁ is connected in parallel to this series circuit. The emitter of the transistor TR ₁ is grounded via the resistor R ₁ and is also connected to the connection between the capacitors C ₁ and C ₂ . The emitter of the transistor TR ₁ also has a buffer circuit BC via a coupling capacitor C ₄ .
Connected to the base of the buffer transistor TR ₂ .

In the buffer circuit BC, the power supply terminal V _CC is grounded via the capacitor C ₆ and the coil L
It is connected to the collector of the buffer transistor TR ₂ through _2. The emitter of the transistor TR ₂ is a resistor R ₂
And a capacitor C ₅ are connected to ground via a parallel circuit. The collector of the transistor TR ₂ is connected to the output terminal t ₀ via the capacitor C ₇ .

Next, the operation of this oscillator will be described. When the resonance voltage generated by the coil L ₁ and the capacitors C ₁ and C ₂ that form the tank circuit of the oscillator circuit OS is applied to the base of the transistor TR ₁ , and the base current flows, the transistor TR ₁
Collector current flows through TR ₁ . The emitter current is positively fed back to the connection of the capacitor C ₁ and C _2, whereby oscillation of the tank circuit consisting of a coil L ₁ and the capacitor C ₁ and C ₂ Metropolitan continues. Also, the output current of the transistor TR ₁ that changes according to the resonance current is the coupling capacitor C
It flows to the base of the transistor TR ₂ of the buffer circuit BC via ₄ . Transistor TR ₂ amplifies its input current,
The amplified current is output to the output terminal t ₀ via the capacitor C ₇ .

FIG. 6 is a circuit diagram of a main portion of an oscillator disclosed in Japanese Patent Laid-Open No. 63-209306. The base of the transistor TR ₁ of the oscillation circuit OS is grounded via a coil L _1, a series circuit of the capacitor C ₁ and C ₂ is connected in parallel to the coil L _1. The emitter of the transistor TR ₁ is grounded via the resistor R ₁ and the capacitor C 1
_It is connected to the connection between ₁ and C ₂ . Transistor TR
The collector of ₁ is grounded via a capacitor C ₃ .

The collector of the transistor TR ₁ is connected to the emitter of the transistor TR ₂ of the buffer circuit BC,
The emitter of the transistor TR ₁ is connected to the base of the transistor TR ₂ via the coupling capacitor C ₄ , and the transistors TR ₁ and TR ₂ are cascade-connected.

The emitter of the transistor TR ₂ of the buffer circuit BC is grounded via the capacitor C ₅ . The collector is connected to the power supply terminal V _CC via the coil L ₂ and to the output terminal t ₀ via the capacitor C ₇ . The power supply terminal V _CC is grounded via the capacitor C ₆ . This oscillator also oscillates similarly to the former oscillator, and also amplifies the output current of the oscillation circuit. However, in this oscillator, the current flowing from the power supply terminal V _CC through the transistor TR ₂ commonly flows to the transistor TR ₁ .

[0009]

In the above-mentioned conventional oscillator, due to the influence of the collector capacitance of the transistor of the buffer circuit, the higher the oscillating frequency, the more the electrical characteristics such as the oscillating frequency greatly fluctuate with respect to the load fluctuation. Further, when the gain of the buffer circuit is increased, the above-mentioned tendency becomes larger due to the mirror effect. Therefore, in order to reduce fluctuations in electrical characteristics due to load fluctuations and to increase gain, another transistor may be connected in cascade on the collector side of the buffer transistor, but then the added transistor and the circuit components related to that transistor are connected. Must be added, which increases the number of parts and increases the cost and size of the oscillator. Also, the Q of the oscillator
In order not to reduce the load fluctuation and the load variation, the capacity of the coupling capacitor that couples the oscillation circuit and the buffer circuit cannot be increased, which limits the oscillation output of the oscillator in relation to the power consumption.

Further, in the former oscillator described above, there is a problem that current consumption increases because currents are separately supplied from the power supply terminal to the transistors of the oscillation circuit and the buffer circuit. The present invention has been made in view of such problems,
It is an object of the present invention to provide an oscillator in which electric characteristics do not change due to load fluctuation, an oscillation output is not limited, an oscillation frequency band is wide, power consumption is low, and a number of circuit components can be reduced. To aim.

[0011]

The oscillator of the first invention is an oscillator for outputting an oscillation signal generated in an oscillation circuit through a buffer circuit, wherein both the transistor of the oscillation circuit and the base of the transistor of the buffer circuit are provided. It is grounded, and both transistors are connected in cascade via an impedance converter.

The oscillator of the second invention is an oscillator for outputting an oscillation signal generated in an oscillation circuit via a buffer circuit, wherein the transistor of the oscillation circuit has a base grounded in an alternating current and a collector as an output section. The base of the transistor of the buffer circuit is AC-grounded, the emitter is the input part, the collector is the output part, and the transistor of the oscillator circuit and the transistor of the buffer circuit are cascade-connected via an impedance converter. It is characterized by

[0013]

When the resonance current generated by the tank circuit is input to the transistor of the oscillation circuit whose base is grounded, the output current flows, the output current is positively fed back to the tank circuit, and the oscillation of the tank circuit continues. The output current flowing through the transistor of the oscillator circuit flows through the transistor of the buffer circuit, and the transistor of the buffer circuit amplifies the output signal of the transistor of the oscillator circuit. Further, since the base of the transistor of the buffer circuit is grounded, the internal impedance of the transistor when viewed from the input side to the output side becomes high impedance.

Focusing on the transistors of the buffer circuit, since the base is grounded, the input impedance seen from the emitter is low, but the input impedance of the buffer circuit is increased due to the presence of the impedance converter, and the emitter is also Since the collector has a high impedance as seen from the above, there is no fear of oscillation stoppage, and the electrical characteristics are unlikely to change even if the load of the buffer circuit changes. Moreover, since both transistors are not capacitor-coupled, the oscillation output is not limited. Further, the currents of the transistors are common and the current consumption is reduced.

[0015]

The present invention will be described in detail below with reference to the drawings showing the embodiments thereof. FIG. 1 is a circuit diagram of a main part of an oscillator according to the present invention. This oscillator includes, for example, a Colpitts oscillator circuit OS and a buffer circuit BC. The oscillating transistor TR ₁ of the oscillating circuit OS is grounded via the capacitor C ₃ , and the emitter is grounded via the parallel circuit of the capacitor C ₁ and the resistor R ₁ . A capacitor C ₂ is interposed between the emitter and the collector.

The collector is grounded via the coil L ₁ and is connected to the emitter of the buffer transistor TR ₂ of the buffer circuit BC via the coil L ₂ which is an impedance converter. The buffer transistor TR ₂ is grounded via the capacitor C ₄ , and the collector is connected to the power supply terminal V _CC via the coil L ₃ and also connected to the output terminal t ₀ via the capacitor C ₅ . .. The power supply terminal V _CC is grounded via the capacitor C ₆ .

Next, the oscillation operation of this oscillator will be described. Resonance voltage of the tank circuit by the coil L ₁ and the capacitor C _1, C ₂ in the oscillation circuit OS (resonant circuit) is provided to the emitter of the transistor TR _1, the base current flows through the transistor TR _1, the collector current coil changing the current flowing in L _1, the counter electromotive voltage generated in the coil L _1. The counter electromotive voltage causes a charging current to flow in the tank circuit, charges are accumulated in the capacitor C ₁ and become an emitter voltage, and the above-described operation continues. As a result, the coil L ₁ and the capacitor C ₁ ,
The oscillating operation of the tank circuit composed of C ₂ continues.

The collector voltage of the transistor TR ₁ becomes the input voltage of the buffer circuit BC and is input between the emitter and base of the transistor TR ₂ , and the base current flows and the collector current flows according to the change of the emitter voltage. Since both transistors TR ₁ and TR ₂ are connected in cascade, the collector current of transistor TR ₂ is almost the same as the collector current of transistor TR ₁ . The collector voltage changes according to the collector current of the transistor TR ₂ , which changes the voltage at the output terminal t ₀ . That is, the amplitude of the voltage obtained at the output terminal t ₀ depends on the collector voltage of the transistor TR ₂ , and the amplitude of the current depends on the collector current of the transistor TR ₁ , which determines the oscillation output.

Here, the coil L ₂ inserted between the transistors TR ₁ and TR ₂ converts a low input impedance seen from the emitter of the transistor TR ₂ into a high input impedance so as not to adversely affect the oscillation state. The function of the coil L ₂ which is the impedance converter will be described below. The oscillator circuit OS can be roughly divided into a coil L ₁ which is a resonance element and other circuits. The coil L ₁ is a load having an impedance zl, and the other circuits are a power generation source including a positive feedback circuit, that is, a negative resistance having an impedance zd. Can be regarded as Oscillation continues when the negative resistance power generated by the negative resistance zd is consumed by the load zl, that is, when −zd ≧ zl is maintained.

When a low impedance buffer circuit is connected to the output side of such an oscillator circuit OS, the negative resistance power is reduced and the oscillation is stopped. In the present invention, however, the coil L ₂ is provided at the buffer circuit BC input stage. The total negative resistance zd ′ including the buffer circuit BC
The state of zd ′ ≧ zl is maintained.

FIG. 2 shows the input impedance of the buffer circuit BC.
In the Smith chart that shows the normalization of the S conversion state with 50Ω
is there. From the buffer circuit BC shown in FIG. 1 to the coil L₂Except
The input impedance in the closed state is represented by point A.
It Coil L₂By setting, the phase will rotate depending on the value
And reach point B. According to the experiment by the inventor of the present application, the buffer times
Area C where input impedance of path BC is hatched
Coil L as in ₂Resistance, inductance value
It was found that stable oscillation can be continued by selecting
did.

On the other hand, in this oscillator, current consumption is reduced because a current common to the transistors TR ₁ and TR ₂ flows. Further, since no coupling capacitor is interposed between the transistors TR ₁ and TR ₂ , a large oscillation output can be obtained without suppressing the emitter current of the transistor TR ₂ .

Further, since the base of the transistor TR ₂ is grounded, the influence of the collector capacitance of the transistor TR ₂ does not occur, and the impedance seen from the emitter of the transistor TR ₂ is made higher by the coil L ₂ as described above. The impedance between the collectors is high, and even if the load of the buffer circuit BC changes, the fluctuations in the electrical characteristics such as the oscillation frequency are small.

[0024] from being further or base transistor TR _1, TR ₂ are both ground, transistor TR ₁ of each,
The influence of the collector capacitance of TR ₂ does not occur and the oscillation frequency band in which a predetermined gain is obtained is expanded. In other words, in the case of normal grounded emitter, the phase of the base and the phase of the collector are
The output is attenuated due to the influence of collector capacitance due to the 180 ° shift, but according to the present invention, both transistors TR ₁ and TR of the oscillator circuit and the buffer circuit BC are attenuated.
_Since the influence of the collector capacitance of ₂ does not occur, the oscillation frequency band for obtaining a predetermined gain is expanded.

Further, since no other transistor is cascade-connected to the collector side of the transistor TR ₂ of the buffer circuit BC, the number of circuit components does not increase, and the oscillator can be made smaller and lighter.

FIG. 3 is an actual circuit diagram showing an example of a voltage controlled oscillator using the oscillator described above. A tuning voltage terminal V _T that gives a tuning voltage as a voltage for controlling the oscillation frequency is grounded via a capacitor C ₆ .
It is also grounded via a series circuit of a coil L ₄ and a variable capacitance diode VD. The connecting portion between the coil L ₄ and the variable capacitance diode VD is connected to the collector of the oscillation transistor TR ₁ via the series circuit of the capacitors C ₅ and C ₃ .

The connection between the capacitors C ₅ and C ₃ is grounded via the coil L ₁ . Transistor
The base of TR ₁ is grounded via a parallel circuit of a resistor R ₂ and a capacitor C _4, and a buffer circuit is connected via a resistor R _3.
It is connected to the base of the transistor TR ₂ of BC.

The emitter of the transistor TR ₁ is grounded through a parallel circuit of a resistor R ₁ and a capacitor C ₁ .
A capacitor C ₂ is interposed between the collector and the emitter. The collector of the transistor TR ₁ is connected to the emitter of the transistor TR ₂ via the coil L ₂ . The base of the transistor TR ₂ is grounded via the capacitor C ₇ , and its collector is connected via the capacitor C ₉ to the output terminal t.
Connected with ₀ . The collector of transistor TR ₂ is
Through coil L ₃ is connected to the power supply terminal V _CC, the power supply terminal V _CC is connected to the base of the transistor TR ₂ via a resistor R _4, and is also grounded via a capacitor C _8.

[0029] The voltage controlled oscillator, the transistor TR ₂ of the transistor TR ₁ and the buffer circuit BC of the oscillation circuit OS are both grounded base, both transistors are cascade-connected. The oscillator circuit OS is a transistor TR ₁ ,
A Clap oscillator circuit using capacitors C ₁ , C ₂ and C ₃ and a coil L ₁ is used.

When a 5 V power supply was connected to the power supply terminal V _CC and this oscillator was operated, the oscillation frequency was 1500 MHz.
When set to z, the current consumption of this oscillator was 6 mA when the oscillation output was adjusted to 0 dBm. The conventional oscillator shown in FIG. 5 consumes a power supply voltage of 7 V and an output current of 20 V.
It is mA, and it can be confirmed that it is significantly reduced compared to that, and under the condition of “50Ω reference, VSWR (voltage standing wave ratio) = 2.0 all phases”, the frequency load fluctuation Δf is Δf = 2MH
It has been confirmed by experiments that z becomes Δf = 350 kHz.

FIG. 4 shows another embodiment of the voltage controlled oscillator according to the present invention. In this embodiment, both transistors TR ₁ and TR
_The method of applying the base voltage ₂ is different from that of the embodiment shown in FIG. I.e. the power supply voltage to the transistor TR ₁ resistor R ₃₀ and R
_The voltage is divided by ₂₀ and applied, and the power supply voltage is divided by the resistors R ₄₀ and R ₅₀ and applied to the transistor TR ₂ . Since other configurations and operations are similar to those in FIG. 3, the same reference numerals are given and description thereof is omitted. Although the Colpitts oscillator circuit and the Clapp oscillator circuit are used as the oscillator in this embodiment, a Hartley oscillator circuit, a Lampkin oscillator circuit, or an inductively coupled oscillator circuit may be used. Further, in the present specification and drawings, the coils L ₁ , L ₂ ,
Although L ₃ is used for the expression, a distributed constant type inductive element such as a microstrip line may be used.

[0032]

As described above, according to the present invention, it is possible to suppress load fluctuations, stabilize electric characteristics, obtain a large oscillation output, and suppress current consumption (power). Further, the oscillation frequency band can be widened. Further, the present invention has excellent effects such as reduction in the number of parts and size reduction.

[Brief description of drawings]

FIG. 1 is a circuit diagram of an oscillator of the present invention.

FIG. 2 is a Smith chart for selecting an impedance converter of the present invention.

FIG. 3 is a circuit diagram of an oscillator of the present invention.

FIG. 4 is a circuit diagram of an oscillator of the present invention.

FIG. 5 is a circuit diagram of a conventional oscillator.

FIG. 6 is a circuit diagram of a conventional oscillator.

[Explanation of symbols]

TR ₁ , TR ₂ Transistor L ₁ , L ₂ , L ₃ Coil C ₁ , C ₂ , C ₃ Capacitor OS Oscillation circuit BC Buffer circuit

Claims (2)

[Claims] 1. An oscillator for outputting an oscillation signal generated in an oscillation circuit via a buffer circuit, wherein a transistor of the oscillation circuit and a base of a transistor of the buffer circuit are both grounded, and both transistors are impedance converters. An oscillator characterized by being connected in cascade via. 2. In an oscillator for outputting an oscillation signal generated in an oscillation circuit via a buffer circuit, a transistor of the oscillation circuit has a base AC grounded,
The collector serves as an output unit, the transistor of the buffer circuit grounds the base in an alternating current, the emitter serves as an input unit, the collector serves as an output unit, and the transistor of the oscillation circuit and the transistor of the buffer circuit are connected via an impedance converter. An oscillator characterized by being cascaded together.