JPH1197929A - Oscillator and up/down tuner system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an oscillator in which the number of transistors and resistance can be reduced, satisfactory phase noise characteristics can be realized, and a circuit scale can be miniaturized by providing a resonance circuit, one transistor, feedback capacity, and first-third bias resistance. SOLUTION: A resonating part 20 is provided with one NPN transistor 21 for amplifying the output of a resonating part 10. An output node 22 of the resonating part 10 is connected with the base of the transistor 21, and a power source node 23 is connected with the collector. A DC voltage impressed to the power source node 23 is impressed to the base of the transistor 21 by bias resistance 25 and 26, and the emitter voltage of the transistor 21 is decided by a bias resistance 27 and emitter currents. An oscillation signal is returned from the base of the transistor 21 through a feedback capacity 24 to the collector. Oscillation is maintained by this feedback, and the oscillation signal is outputted from an output terminal 30 connected with the emitter as an oscillation output.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an oscillator used for a frequency conversion operation of an up-converter or a down-converter in, for example, a heterodyne transmission / reception system, and an up / down tuner system using the oscillator.

[0002]

2. Description of the Related Art Conventionally, as a technique in this kind of field, for example, there has been a technique shown in FIG. FIG. 8 is a circuit diagram showing a configuration example of a conventional oscillator.

This oscillator has a resonance section 200 having a unique frequency and two NPN transistors 101 and 102.
And an oscillating unit 300 constituted by a multivibrator comprising a differential pair of

The bases and collectors of the transistors 101 and 102 are connected to a resonance section (tank circuit) 200. Further, the emitters of the transistors 101 and 102 are commonly connected and connected to a current source 103. DC
The voltage is applied from the terminal 104 to the collector load resistors 105 and 10.
6 is supplied to transistors 101 and 102.
The base voltage of the transistors 101 and 102 is
7 from the bias circuit 108 to the resistors 109, 1
10 is applied. And the transistor 10
The bases 1 and 102 are connected to output terminals 111 and 112, respectively, and an oscillation output Po is taken out from the output terminals 111 and 112.

In the resonance section 200, a resonance action occurs when a certain frequency matches the natural frequency of the circuit. That is, a particularly large voltage or current is generated for the variable voltage VT of a certain frequency. The frequency of the variable voltage VT at this time is called a resonance frequency fosc.

FIG. 9 is a circuit diagram showing the internal configuration of the resonance section 200.

In the figure, reference numerals 201 to 204 denote the oscillation unit 300
Reference numeral 210 denotes an input terminal for inputting a variable voltage VT. 211 is a resistor, and 212 is an inductor. Incidentally, a high resistance is generally used for the resistor 211 in order to make the power supply impedance of the variable voltage VT invisible.

Reference numerals 213 and 214 denote variable capacitance diodes, 2
Reference numerals 15 and 216 denote high resistances, and reference numerals 217 and 218 denote DC-capacity cutting capacitors. Further, 219 and 220 are feedback capacitors.

According to the oscillator configured as described above, when the variable voltage VT applied from the input terminal 210 is applied to the variable capacitance diodes 213 and 214, the capacitance of the variable capacitance diodes 213 and 214 changes. Change the oscillation frequency. The oscillation frequency mainly depends on the resonance section 20.
0 inductor 212 and variable capacitance diodes 213 and 2
14 resonance effects. The oscillation signal is output in parallel from the output terminals 111 and 112 as the oscillation output Po, and at the same time, is returned from the base of one transistor to the collectors of the transistors 101 and 102 via the feedback capacitors 219 and 220, respectively.

[0010]

However, in the conventional oscillator, the thermal noise of the base and emitter resistances of the transistors 101 and 102 and the resistances of the resistors 105, 106, 1
There is a problem that phase noise characteristics are deteriorated due to thermal noise of the components 09 and 110 and the like.

When this point is actually tested with an oscillator in the 1 GHz band, as shown in FIG. 10, about -75 dBc /
Hz (10 KHz offset), and the deterioration of the phase noise characteristic became clear.

Further, there is another problem that the oscillation section 300 is not suitable for miniaturization because it is a differential pair.

The present invention has been made to solve the above-mentioned conventional problems, and an object of the present invention is to provide an oscillator which can realize a good phase noise characteristic and can reduce the circuit scale. is there. Still another object is to provide an up / down tuner system using the oscillator of the above object.

[0014]

In order to achieve the above object, a first aspect of an oscillator is characterized by a resonance circuit having a unique frequency and determining an oscillation frequency by a resonance action;
A transistor having a base connected to an output node of the resonance circuit and a collector connected to a power supply node to which a DC voltage is applied; a feedback capacitor connected between a base and an emitter of the transistor; A first bias resistor connected between the output node and ground; a second bias resistor connected between the output node and ground; and a third bias resistor connected between the emitter of the transistor and ground. A bias resistor and an oscillation output from the emitter of the transistor.

According to the first aspect, the resonance circuit determines the oscillation frequency by the resonance action, and the transistor amplifies the output of the resonance circuit. The oscillation output from the transistor is fed back from the base of the transistor to the collector via the feedback capacitor, and the oscillation continues. As a result, the number of transistors and resistors can be reduced as compared with the conventional circuit, and the thermal noise of the base and emitter resistors of the transistor and the thermal noise of the resistors can be reduced as compared with the conventional circuit.

The oscillator according to the second aspect of the invention is characterized in that a resonance circuit having a unique frequency and determining an oscillation frequency by a resonance action, a base is connected to an output node of the resonance circuit, and a DC voltage is applied A transistor having a collector connected to the power supply node, a feedback capacitor connected between a base and an emitter of the transistor, a first bias resistor connected between the power supply node and the output node, The second connected between the node and ground
A bias resistor, a third bias resistor connected between the emitter of the transistor and ground, a collector grounding capacitor connected between the power supply node and ground, and a And a common emitter capacitor connected between the transistors, and an oscillation output is taken out from the emitter of the transistor.

According to the second aspect, the resonance circuit determines the oscillation frequency by the resonance action, and the transistor amplifies the output of the resonance circuit. The oscillation output from the transistor is fed back from the base of the transistor to the collector via the feedback capacitor, and the oscillation continues. At this time, the oscillation operation is accurately performed in the oscillatable band determined by the common collector capacitance and the common emitter capacitance.
As a result, the number of transistors and resistors can be reduced as compared with the conventional circuit, and the thermal noise of the base and emitter resistors of the transistor and the thermal noise of the resistors can be reduced as compared with the conventional circuit.

A third aspect of the present invention is the oscillator according to the second aspect, wherein first and second resistors are connected in series between the emitter of the transistor and ground, and the first and second resistors are connected in series. And the output divided by the resistor is taken out as the oscillation output.

According to the third aspect, the oscillation output is set to the first level.
Further, since the voltage is divided and output by the second resistor, the oscillation output level can be easily controlled.

A fourth aspect of the present invention is the oscillator according to the third aspect, wherein the first and second resistors are connected to the third resistor.
Is divided into two and substituted.

According to the fourth aspect, the same operation as that of the third aspect can be obtained with a small number of parts.

A fifth aspect of the present invention is the oscillator according to the second aspect, wherein first and second capacitors are connected in series between the emitter of the transistor and ground, and the first and second capacitors are connected in series. The output divided by the capacitor of the above is taken out as the oscillation output, and the first and second capacitors are obtained by dividing the common emitter capacitor into two parts.

According to the fifth aspect, an operation equivalent to that of the third aspect is achieved with a small number of parts.

The up / down tuner system according to the sixth invention is characterized by a first noise filter for cutting a predetermined noise region of a received radio wave, and a first frequency for increasing an output frequency of the first noise filter. A conversion unit; a second noise filter that cuts a predetermined noise region of an output signal of the first frequency conversion unit; a second frequency conversion unit that lowers an output frequency of the second noise filter; 6. An up / down tuner system comprising: a third noise filter that cuts a predetermined noise region of an output signal of the frequency converter of claim 1; It is to perform each frequency conversion operation using the oscillation output of the above-described oscillator.

According to the sixth aspect, the frequency conversion function of the first and second frequency conversion units is improved.

[0026]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a circuit diagram of the oscillator according to the first embodiment of the present invention.

This oscillator comprises a resonance section 10 having a unique frequency and an oscillation section 20.

The resonance section 10 is composed of a so-called tank circuit having an inductor and a capacitance. When a certain frequency (resonance frequency) coincides with the natural frequency of the circuit, a resonance action occurs. Specifically, as shown in FIG. 2, a resistor 12 and a capacitor 13 are connected in series between an input terminal 11 to which a variable voltage VT having a predetermined frequency is applied and an output node 22. Here, a high resistance is generally used for the resistor 12 in order to make the power supply impedance of the variable voltage VT invisible. The capacity 13 is a capacity for cutting DC components.
A series resonance circuit including a variable capacitance diode 14 and an inductor 15 is connected between a node N, which is a connection point between the resistor 12 and the capacitor 13, and the ground.

In the resonance section 10, the input terminal 11
Is applied to the variable capacitance diode 14
Is applied to the variable capacitance diode 14
Changes the oscillation frequency.

The oscillation section 20 has one NPN transistor 21 for amplifying the output of the resonance section 10. The output node 22 of the resonance unit 10 is
, And a power supply node 23 to which a DC voltage is applied is connected to the collector.

A feedback capacitor 24 is connected between the base and the emitter of the transistor 21. Further, a bias resistor 25 is connected between the power supply node 23 and the output node 22.
A bias resistor 26 is connected between the output node 22 and the ground GND, and a bias resistor 27 is connected between the emitter of the transistor 21 and the ground GND. That is, the D applied to the power supply node 23
The C voltage is applied to the base of the transistor 21 by the bias resistors 25 and 26, and the emitter voltage of the transistor 21 is determined by the bias resistor 27 and the emitter current.

The collector of the transistor 21 is grounded at a high frequency by a grounded collector capacitance 28, and the emitter of the transistor 21 and the ground GND are connected to a grounded emitter capacitance 29 which functions to lower the emitter impedance. Here, the collector ground capacitance 28
And the common emitter capacitance 29 determine the oscillatable band of the oscillator of the present embodiment. And the transistor 21
The oscillation output Po is output from the output terminal 30 connected to the
Is to be taken out.

According to the oscillator of this embodiment, the oscillation frequency is determined mainly by the resonance between the variable capacitance diode 14 and the inductor 15 of the resonance unit 10. The oscillation signal is returned from the base of the transistor 21 to the collector via the feedback capacitor 24. Oscillation continues due to this feedback, and an oscillation signal is output from the output terminal 30 as an oscillation output Po.

In the oscillator according to the present embodiment, only one transistor is required and the number of resistors is smaller than that of the conventional circuit. Therefore, the thermal noise of the base and emitter resistors of the transistor and the thermal noise of the resistor are smaller than those of the conventional circuit. Can be reduced, and good phase noise characteristics can be obtained. Furthermore, since the configuration of the resonance section as well as the oscillation section can be simplified,
The circuit scale can be reduced.

Actually, when actually measured in the 1 GHz band, the feedback capacitance 24 is set to 2 [PF], and the collector ground capacitance 28 is set to 10 [PF].
When it is set to 00 [PF], as shown in FIG. 3 showing a phase noise characteristic diagram of the present embodiment, −85 to 90 dBc / Hz.
(10 KHz offset) and good phase noise characteristics can be obtained. Note that the solid line Z1 in FIG. 3 shows the characteristics of the present embodiment, and the broken line Z2 shows the characteristics of the conventional circuit shown in FIG.

Further, in the present embodiment, the chip area can be reduced to about 1/4 or less of the conventional circuit even when the capacitors 24 and 29 are built-in.

Next, a second embodiment of the present invention will be described.

FIG. 4 is a circuit diagram of an oscillator according to a second embodiment of the present invention, and the same reference numerals are given to the same elements as those in FIG.

In the present embodiment, the voltage dividing resistors 41 and 42 are connected in series between the emitter of the transistor 21 and the ground GND in the circuit configuration of FIG. The output terminal 30 is drawn out.

According to this circuit configuration, the signal divided by the voltage dividing resistors 41 and 42 from the output terminal 30 is applied to the oscillation output P.
Retrieved as o. By arbitrarily setting the resistance values of the voltage dividing resistors 41 and 42, the level of the oscillation output Po can be easily reduced to a desired level.

In an oscillator used for a frequency converter or the like, it is necessary to control the level of the oscillation output Po within a certain range in order to correct the distortion of the oscillation output Po and to obtain a gain. It is difficult to design well. In consideration of this point, in the present embodiment, the voltage dividing resistors 41 and 42 are provided, and the oscillation output Po is divided by the voltage dividing resistors 41 and 42.
Since the voltage is divided before output, the level of the oscillation output Po can be easily controlled, and the isolation is improved, so that the leakage of the high-frequency signal can be suppressed.

According to the actual measurement in the 1 GHz band, the voltage dividing resistor 4
The level of the oscillation output Po in the case where the voltage is output without performing the voltage division by the reference numerals 1 and 42 (the first embodiment) is about +2 dBm.
−7 when the voltage dividing resistor 42 is 300 [Ω].
It is about dBm. The isolation is about 10d
B improves.

Next, a third embodiment of the present invention will be described.

FIG. 5 is a circuit diagram of an oscillator according to a third embodiment of the present invention. Elements common to those in FIG. 4 are denoted by the same reference numerals.

In the present embodiment, the functions of the voltage dividing resistors 41 and 42 are substituted for the emitter resistor 27 in the circuit configuration of FIG. That is, the emitter resistance 27 is set to 2
By dividing the voltage dividing resistors 27a and 27b, the same effect as in the second embodiment can be obtained with a small number of components.

Next, a fourth embodiment of the present invention will be described.

FIG. 6 is a circuit diagram of an oscillator according to a fourth embodiment of the present invention, and the same reference numerals are given to the same elements as in FIG.

This embodiment is different from the circuit configuration of FIG.
a, 29b, and by connecting the output terminal 30 to the connection point, an effect equivalent to that of the second embodiment can be obtained with a small number of components.

The two partial pressure capacities 29a, 29b
It is also possible to take one of them out of the IC as an external component and control the level of the oscillation output Po from outside.

Next, an application example of the oscillator according to the present invention will be described.

FIG. 7 is a block diagram of a main part of an up / down tuner system showing an application example of the oscillator of the present invention.

The up / down tuner system is provided, for example, in a heterodyne (homo-super, diving-super, etc.) receiving system, in which an antenna 61, a noise filter 62, and an up-converter 63 are sequentially connected. . Further, a noise filter 64, a down converter 65, a noise filter 66, and a tuner 67 are sequentially connected to the output side of the up converter 63.

The up-converter 63 and the down-converter 65 are connected to oscillators 63A and 65A, respectively.
Up / down frequency conversion is performed by the oscillation output of A. The oscillators 63A and 65A correspond to the first to fourth oscillators.
It is composed of the oscillator of the present invention described in the embodiment.

According to the up / down tuner system, the radio wave received by the antenna 61 is input to the up-converter 63 after a predetermined noise area is cut by the noise filter 62.

The up-converter 63 up-converts the frequency of the received signal using the oscillation output Po of the oscillator 63A of the present invention. The up-converted signal further passes through a noise filter 64, in which a predetermined noise region corresponding to the conversion frequency of the up-converter 63 is cut, and is input to the down-converter 65.

In the down converter 65, the output of the noise filter 64 is reduced to the frequency required for the tuner 67 using the oscillation output Po of the oscillator 65A of the present invention. After that, the output of the down converter 65 is further input to the tuner 67 via the noise filter 66.

Since the oscillator according to the present invention is used in such an up / down tuner system, the frequency conversion function of the up converter 63 and the down converter 65 is improved, and the tuning operation can be performed with high accuracy.

[0058]

As described above in detail, according to the oscillator of the first aspect, the oscillator includes the resonance circuit, one transistor, the feedback capacitance, and the first to third bias resistors. The number of transistors and resistors is smaller than that of the conventional circuit, and the thermal noise of the base and emitter resistance of the transistor and the thermal noise of the resistor can be made smaller than that of the conventional circuit, so that good phase noise characteristics can be obtained. Will be possible. Further, since the configuration of the resonance section as well as the oscillation section can be simplified, the circuit scale can be reduced. This makes it possible to realize an oscillator suitable for an integrated circuit.

According to the oscillator according to the second aspect of the invention, the same effect as that of the first aspect of the invention can be obtained, and the oscillation operation can be accurately performed in the oscillatable band determined by the common collector capacitance and the common emitter capacitance. It is possible to do.

According to the oscillator of the third aspect, the oscillation output is output after being divided by the first and second resistors.
The oscillation output level can be easily controlled,
A desired oscillation output level can be obtained. Further, since the isolation is improved, the leakage of the high frequency signal can be suppressed.

According to the oscillator of the fourth aspect, the same effect as that of the third aspect can be obtained with a small number of components.

According to the oscillator of the fifth aspect, the same effect as that of the third aspect can be obtained with a small number of parts.

According to the up / down tuner system of the sixth invention, since the oscillator of the present invention is used in the first and second frequency converters, the frequency conversion in the first and second frequency converters is performed. The function is improved, and the tuning operation can be performed with high accuracy.

[Brief description of the drawings]

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

FIG. 2 is a circuit diagram of a resonance unit shown in FIG.

FIG. 3 is a phase noise characteristic diagram in the first embodiment.

FIG. 4 is a circuit diagram of an oscillator according to a second embodiment of the present invention.

FIG. 5 is a circuit diagram of an oscillator according to a third embodiment of the present invention.

FIG. 6 is a circuit diagram of an oscillator according to a fourth embodiment of the present invention.

FIG. 7 is a block diagram of a main part configuration of an up / down tuner system showing an application example according to the oscillator of the present invention.

FIG. 8 is a circuit diagram illustrating a configuration example of a conventional oscillator.

FIG. 9 is a circuit diagram of a conventional resonance unit.

FIG. 10 is a phase noise characteristic diagram of a conventional oscillator.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Resonant part 12 Resistance 13 Capacitance 14 Variable capacitance diode 15 Inductor 20 Oscillator 21 NPN transistor 24 Feedback capacitance 25, 26, 27 Bias resistance 28 Collector ground capacitance 29 Emitter ground capacitance Po Oscillation output VT Variable voltage

Claims (6)

[Claims] 1. A resonance circuit having a unique frequency and determining an oscillation frequency by a resonance action, a base connected to an output node of the resonance circuit, and a collector connected to a power supply node to which a DC voltage is applied. Transistor, a feedback capacitor connected between the base and the emitter of the transistor, a first bias resistor connected between the power supply node and the output node, and between the output node and ground. An oscillator comprising: a second bias resistor connected thereto; and a third bias resistor connected between an emitter of the transistor and ground, wherein an oscillation output is taken out from the emitter of the transistor. . 2. A resonance circuit having a unique frequency and determining an oscillation frequency by a resonance action, a base connected to an output node of the resonance circuit, and a collector connected to a power supply node to which a DC voltage is applied. A transistor; a feedback capacitor connected between the base and the emitter of the transistor; a first bias resistor connected between the power supply node and the output node; and a transistor connected between the output node and ground A second bias resistor, a third bias resistor connected between the emitter of the transistor and ground, a collector ground capacitance connected between the power supply node and ground, an emitter of the transistor A grounded emitter capacitor connected to the ground, and an oscillation output taken out from the emitter of the transistor. Oscillator and said. 3. A configuration in which first and second resistors are connected in series between the emitter of the transistor and ground, and an output divided by the first and second resistors is taken out as the oscillation output. 3. The oscillator according to claim 2, wherein: 4. The oscillator according to claim 3, wherein said first and second resistors are substituted by dividing said third bias resistor into two. 5. A configuration in which first and second capacitors are connected in series between the emitter of the transistor and ground, and an output divided by the first and second capacitors is taken out as the oscillation output. 3. The oscillator according to claim 2, wherein said first and second capacitors are obtained by dividing said common emitter capacitor into two parts. 6. A first noise filter for cutting a predetermined noise region of a received radio wave, a first frequency converter for increasing an output frequency of the first noise filter, and an output signal of the first frequency converter. A second noise filter that cuts a predetermined noise region, a second frequency converter that lowers an output frequency of the second noise filter, and a predetermined noise region of an output signal of the second frequency converter. In an up / down tuner system including a third noise filter, the first and second frequency conversion units use the oscillation output of the oscillator according to claim 1 to perform respective frequency conversion. An up / down tuner system for performing an operation.