JP2001111342A - Two band oscillator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain stable oscillation signals in two frequency bands whose frequencies greatly differ, and to obtain the satisfactory C/N and a large power. SOLUTION: A voltage control oscillator circuit 1 is provided with feedback capacitors 4 and 5 connected between the base/emitter and emitter/collector of an oscillation transistor 2, a resonance circuit 12 equipped with at least a varactor diode 13 and an inductance element 14 and connected in harmonics between the collector and base, and an impedance 8 connecting the emitter and ground in DC. A buffer circuit 30 is constituted of a tuning amplifier circuit capable of turning with two frequency bands, and the impedance circuit 8 is constituted so that a large impedance can be obtained with the two frequency bands, and the feedback capacitors 4 and 5 and the inductance element 14 are constituted so as to be switchable, and at the time of performing oscillation in the high frequency band, the capacitance of the feedback capacitors 4 and 5 and the inductance of the inductance element 14 are decreased, and at the time of performing oscillation in a low frequency band, the capacitance and the inductance are increased.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is to stably oscillate in two frequency bands whose frequencies are separated by about twice and to obtain an oscillation signal having a good C / N in each frequency band. It relates to a band oscillator.

[0002]

2. Description of the Related Art FIG. 2 shows a circuit configuration of a conventional two-band oscillator. The voltage controlled oscillation circuit 41 is configured as a Colpitts oscillation circuit of a common collector type, and includes an oscillation transistor 42
Is grounded at a high frequency by a DC cut capacitor 43. Feedback capacitors 44 and 45 are provided between the base and emitter and between the emitter and collector, respectively.
Is connected to the base, a bias voltage is applied to the base by bias resistors 46 and 47, and the emitter is connected to the ground by a resistor 48.

The base is a DC cut capacitor 49.
Is connected to one end of the inductance element 50.
The inductance element 50 is composed of two inductance elements 5
0a and 50b are connected in series with each other, and the other end is grounded. Then, the inductance element 50a,
The connection point 50b is connected to the anode of the switch diode 52 via the DC cut capacitor 51, and the cathode is grounded. The varactor diode 53 is connected to the inductance element 50 via the DC cut capacitor 54.
Are connected in parallel.

A control voltage Vc is applied to the cathode of the varactor diode 53 via a power supply resistor 55, and a switching voltage for making the switch diode 52 conductive or non-conductive to the anode of the switch diode 52 via a power supply resistor 56. Vs is applied.

With the above configuration, when the switching diode 52 is turned on by the switching voltage Vs, both ends of the inductance element 50b are short-circuited, and the oscillation frequency is increased. When the switching diode 52 is turned off, the oscillation frequency is decreased. The oscillation frequency can be changed by the control voltage Vc applied to the varactor diode 53.

The oscillation signal is output from the emitter of the oscillation transistor 42 and input to the buffer circuit 58 via the coupling capacitor 57. The buffer circuit 58 is configured as a broadband amplifier, amplifies the oscillation signal, and outputs the amplified signal to a circuit (not shown).

[0007]

In the conventional two-band oscillator, since the feedback capacitors 44 and 45 of the voltage-controlled oscillation circuit 41 are constant, the frequency band where the negative resistance value of the oscillation transistor 42 is high and low is determined. Therefore, it was not possible to optimize each of them, and it was not possible to stably oscillate in both frequency bands.

Also, since the resistor 48 connected between the emitter of the oscillation transistor 42 and the ground is connected in parallel with the feedback capacitor 45, the oscillation power flows because an oscillation current flows in addition to the DC bias current. As a result, the C / N of the oscillation signal deteriorated.

Further, since the buffer circuit 58 is configured as a wide band amplifier to amplify the oscillation signals of the two frequency bands, the oscillation signal cannot be amplified to a sufficient level.

It is therefore an object of the present invention to provide a two-band oscillator capable of obtaining stable oscillation signals in two frequency bands having different frequencies, and having a good C / N and a large power. And

[0011]

In order to solve the above-mentioned problems, a two-band oscillator according to the present invention comprises a voltage-controlled oscillator oscillating in two high and low frequency bands, and an oscillation signal output from the voltage-controlled oscillator. A buffer circuit for amplifying, wherein the voltage-controlled oscillation circuit includes an oscillation transistor having a collector grounded at a high frequency, a feedback capacitor connected between a base-emitter and an emitter-collector of the oscillation transistor, and at least a varactor. A resonance circuit having a diode and an inductance element and connected between the collector and the base of the oscillation transistor at a high frequency; and an impedance circuit that connects the emitter of the oscillation transistor and the ground in a DC manner. Wherein the buffer circuit has a tuned amplification circuit tunable to the two frequency bands. The impedance circuit is configured to have a large impedance in the two frequency bands, the feedback capacitor and the inductance element are configured to be switchable, and the voltage controlled oscillation circuit oscillates in a high frequency band. In this case, the capacitance value of the feedback capacitor and the inductance value of the inductance element are reduced, and when the oscillation is performed in a low frequency band, the capacitance value and the inductance value are increased.

Further, in the two-band oscillator of the present invention, the feedback capacitors are connected in series with each other, the connection point of each is connected to the emitter, and both ends are connected to the base and the collector at high frequency. A second feedback capacitor, connected in series with each other and connected to each other by a first switch diode to the emitter of the oscillation transistor, and both ends of which are connected to a base and a collector at high frequencies. A fourth feedback capacitor, when the voltage-controlled oscillation circuit oscillates in the low frequency band, conducts the first switch diode to connect the first feedback capacitor and the third feedback capacitor. Connect in parallel, connect the second feedback capacitor and the fourth capacitor in parallel, the high frequency band In the case where the oscillated were the first switching diode non-conductive.

In a two-band oscillator according to the present invention, the impedance circuit has at least a first parallel resonance circuit and a second parallel resonance circuit connected in series to the first parallel resonance circuit. The resonance frequency of one parallel resonance circuit was set to be substantially the same as the frequency of the low frequency band, and the resonance frequency of the second parallel resonance circuit was set to be almost the same as the frequency of the high frequency band.

Further, in the two-band oscillator according to the present invention, the inductance element includes a first inductance element and a second inductance element connected in series to the first inductance element. A second switch diode that short-circuits both ends of the second switch diode is provided.When the voltage-controlled oscillation circuit oscillates in the low frequency band, the second switch diode is turned off, and when oscillating in the high frequency band, Turned on the second switch diode.

Further, in the two-band oscillator of the present invention, the buffer circuit includes an amplifying transistor, and a parallel tuning circuit having one end connected to the collector of the amplifying transistor and the other end grounded at a high frequency. And a capacitor and a third switch diode connected in series with each other between the ground and the ground.The tuning frequency of the parallel tuning circuit is set to be substantially the same as the frequency of the high frequency band. When oscillating in the low frequency band, the third switching diode is turned on and the capacitor is connected in parallel to the parallel tuning circuit so that the tuning frequency is substantially the same as the frequency in the low frequency band.

[0016]

FIG. 1 shows a circuit configuration of a two-band oscillator according to the present invention. The voltage-controlled oscillation circuit 1 is configured as a Colpitts oscillation circuit of a grounded collector type, and oscillates in two high and low frequency bands of a 0.9 GHz band and a 1.9 GHz band. The collector of the oscillating transistor 2 is applied with the power supply voltage Vb and grounded at high frequency by the DC cut capacitor 3. A first feedback capacitor 4a serving as an input-side feedback capacitor 4 is connected between the base and the emitter, and a second feedback capacitor 5a serving as an output-side feedback capacitor 5 is connected between the emitter and the collector (ground). You. A bias voltage is applied to the base by bias resistors 6 and 7.

The emitter is DC-connected to the ground by an impedance circuit 8 comprising a bias resistor 8a, a first parallel resonance circuit 8b, and a second parallel resonance circuit 8c connected in series to each other. Here, the resonance frequency of the first parallel resonance circuit 8b is made to substantially match the frequency of the low frequency band, and the resonance frequency of the second parallel resonance circuit 8c is made to almost match the frequency of the high frequency band.

Further, a third feedback capacitor 4b and a fourth feedback capacitor 5b, which are connected in series, are connected between the base and the ground.
The connection point between the first switching diode 11 and the fourth feedback capacitor 5b is connected to the emitter of the oscillation transistor 2 via the first switching diode 11. The third feedback capacitor 4b forms the input side feedback capacitor 4, and the fourth feedback capacitor 5b forms the output side feedback capacitor 5.

Therefore, the input side feedback capacitor 4 becomes only the first feedback capacitor 4a due to the non-conduction or conduction of the first switch diode 11, or both the first feedback capacitor 4a and the third feedback capacitor 4b. Can be switched to Similarly, the output side feedback capacitor 5 becomes only the second feedback capacitor 5a due to non-conduction or conduction of the first switch diode 11, or is connected to both the second feedback capacitor 5a and the fourth feedback capacitor 5b. Can be switched.

A resonance circuit 12 is connected between the base of the oscillation transistor 2 and the ground, that is, between the base and the collector in terms of high frequency. The resonance circuit 12
It has at least a varactor diode 13 and an inductance element 14 connected in series with each other. One end of the inductance element 14 is connected to the anode of the varactor diode 14 and the other end is grounded. Then, the cathode of the varactor diode 13 is connected to the base of the oscillation transistor 2 by the coupling capacitor 15. Further, a control voltage Vc is applied to the cathode of the varactor diode 13 via the power supply resistor 16.

The connection point between the first inductance element 14a and the second inductance element 14b is connected to the anode of the second switch diode 18 via the low impedance DC cut capacitor 17, and the cathode thereof is connected to the DC cut capacitor 19 And a DC ground by the bias resistor 20. A bias voltage is applied to the anode of the second switch diode 18 by bias resistors 21 and 22, and these switch diodes are electrically connected or disconnected to the anode of the first switch diode 11 and the cathode of the second switch diode 18. A switching voltage Vs for conducting is applied.

In the above configuration, the voltage controlled oscillation circuit 1
In order to oscillate in a high frequency band, the switching voltage Vs
To a low level, the first switch diode 11 is turned off. Then, only the first feedback capacitor 4a becomes effective as the input-side feedback capacitor 4, and only the second feedback capacitor 5a becomes effective as the output-side feedback capacitor 5, and the optimum negative resistance for a high frequency band is obtained. Is obtained. Further, the second switch diode 18 becomes conductive, and the second inductance element 1
Since both ends of 4b are short-circuited, only the first inductance element 14a is effective as the inductance element 14.
Therefore, the voltage controlled oscillation circuit 1 oscillates in a high frequency band. At this time, since the second parallel resonance circuit 8c has a high impedance in a high frequency band, the oscillation current does not flow through the bias resistor 8a, so that power is not consumed and the C / N of the oscillation signal is improved.

On the other hand, in order to oscillate in a low frequency band, the first switching diode 11 is turned on by setting the switching voltage Vs to a high level. Then, the first feedback capacitor 4a and the third feedback capacitor 4b are connected in parallel, the capacitance value of the input side feedback capacitor 4 increases, and the second feedback capacitor 5a and the fourth feedback capacitor 5b are connected in parallel. , The capacitance value of the output side feedback capacitor 5 increases, and an optimum negative resistance for a low frequency band can be obtained. Further, the second switch diode 18 is turned off, and the first and second inductance elements 14a and 14a are turned off.
b becomes effective. Therefore, the voltage controlled oscillation circuit 1 oscillates in a low frequency band. At this time, since the first parallel resonance circuit 8b has a high impedance in a low frequency band, the oscillation current does not flow through the bias resistor 8a, so that the C / N of the oscillation signal is improved.

The oscillation frequency can be changed by a control voltage Vc applied to the varactor diode 13. Then, an oscillation signal is output from the emitter of the oscillation transistor 2 and input to the buffer circuit 30 via the coupling capacitor 23.

The buffer circuit 30 is configured as a tuned amplifier circuit of a common-emitter type, and an oscillation signal is input to the base of the amplifier transistor 31. The power supply voltage Vb is applied to the collector via the inductance element 32. A first tuning capacitor 33 is connected in parallel to the inductance element 32 to form a parallel tuning circuit. This tuning frequency is set to be a frequency in a high frequency band.

A third switch diode 34 having a cathode connected to the ground, and a second tuning capacitor 35 connected between the anode of the third switch diode 34 and the collector of the amplification transistor 31 are provided. The switching voltage Vs is applied to the anode of the third switching diode 34.

If the switching voltage Vs is at a low level, the third switching diode 34 becomes non-conductive,
A tuning circuit is formed by the inductance element 32 and the first tuning capacitor 33. If the switching voltage Vs is at a high level, the third switching diode 34 conducts, and the first tuning capacitor 33 is connected to the second tuning capacitor. 35 are connected in parallel and the tuning frequency is lowered. The capacitance value of the second tuning capacitor 35 is set so that this frequency substantially matches the frequency of the low frequency band.

Therefore, since the buffer circuit 30 tunes to the frequencies of the two frequency bands, it is possible to obtain a large-level oscillation signal.

[0029]

As described above, the two-band oscillator of the present invention has a feedback capacitor connected between the base and emitter and between the emitter and collector of an oscillation transistor, and at least a varactor diode and an inductance element. It has a resonant circuit connected between the collector and base of the oscillating transistor at high frequency, and an impedance circuit connecting dc between the emitter and ground, and the buffer circuit can be tuned to two frequency bands. When a tunable amplifier is used, the impedance circuit is configured to have a large impedance in two frequency bands, the feedback capacitor and the inductance element are switched, and the voltage controlled oscillation circuit oscillates in a high frequency band. Is the capacitance of the feedback capacitor and the inductance of the inductance element. Reducing the inductance value, since the larger the capacitance value and the inductance value when the oscillating at a low frequency band can be an oscillator circuit having an optimal negative resistance at any frequency band,
The oscillation signal can be transmitted stably, and the C / N of any oscillation signal is improved by the impedance circuit. Further, an oscillation signal having a large level can be obtained.

Further, the two-band oscillator of the present invention has first and second feedback capacitors and third and fourth feedback capacitors, and when the voltage controlled oscillation circuit oscillates in a low frequency band. When connecting the first feedback capacitor and the third feedback capacitor in parallel by the first switch diode, and connecting the second feedback capacitor and the fourth capacitor in parallel to oscillate in a high frequency band Since the first switch diode is turned off, the feedback capacitance by the feedback capacitor can be easily switched.

Further, in the two-band oscillator of the present invention, the impedance circuit has at least a first parallel resonance circuit and a second parallel resonance circuit connected in series, and lowers the resonance frequency of the first parallel resonance circuit. Since the resonance frequency of the second parallel resonance circuit was set to be substantially the same as the frequency of the high frequency band, the oscillation current did not flow through the bias resistor of the emitter in any frequency band. , The C / N of the oscillation signal is improved.

In the two-band oscillator of the present invention, the inductance element is constituted by a first inductance element and a second inductance element, and a second switch diode for short-circuiting both ends of the second inductance element is provided. Since the switching diode is turned on or off depending on the frequency band, the oscillation frequency can be easily changed.

In the two-band oscillator of the present invention, the buffer circuit has a parallel tuning circuit connected to the collector of the amplification transistor, and a capacitor and a third switch connected in series between the collector and the ground. Provide a diode and set the tuning frequency of the parallel tuning circuit to be almost the same as the frequency in the high frequency band.When oscillating the voltage controlled oscillator in the low frequency band, conduct the third switch diode and connect the capacitor in parallel. Since the tuning circuit is connected in parallel to the tuning circuit so that the tuning frequency is substantially the same as the frequency in the lower frequency band, the oscillation signals in the two frequency bands can both be greatly amplified.

[Brief description of the drawings]

FIG. 1 is a circuit configuration diagram of a two-band oscillator of the present invention.

FIG. 2 is a circuit diagram of a conventional two-band oscillator.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Voltage control oscillation circuit 2 Oscillation transistor 3 DC cut capacitor 4 Input side feedback capacitor 4a First feedback capacitor 4b Third feedback capacitor 5 Output side feedback capacitor 5a Second feedback capacitor 5b Fourth feedback capacitor 6,7 Bias Resistance 8 Impedance circuit 8a Bias resistor 8b First parallel resonance circuit 8c First parallel resonance circuit 11 First switch diode 12 Resonance circuit 13 Varactor diode 14 Inductance element 14a First inductance element 14b Second inductance element 15 Coupling Capacitor 16 Feeding resistor 17 DC cut capacitor 18 Second switch diode 19 DC cut capacitor 20, 21, 22 Bias resistor 23 Coupling capacitor 30 Buffer circuit 31 Amplification transistor 32 Inductance element 33 First tuning capacitor 34 Third switching diode 35 Second tuning capacitor

Claims (5)

[Claims] 1. A voltage-controlled oscillation circuit that oscillates in two high and low frequency bands, and a buffer circuit that amplifies an oscillation signal output by the voltage-controlled oscillation circuit, wherein the voltage-controlled oscillation circuit has a collector grounded in high frequency. Oscillation transistor, a feedback capacitor connected between the base-emitter and between the emitter-collector of the oscillation transistor, and at least a varactor diode and an inductance element, between the collector and the base of the oscillation transistor. A resonant circuit connected at a high frequency, and an impedance circuit connecting the emitter of the oscillating transistor and the ground in a DC manner, wherein the buffer circuit is a tuning amplifier circuit tunable to the two frequency bands. And the impedance circuit has a large impedance in the two frequency bands. Impedance
The feedback capacitor and the inductance element are configured to be switched in two ways, and when oscillating the voltage controlled oscillation circuit in a high frequency band, the capacitance value of the feedback capacitor and the inductance value of the inductance element are reduced. When oscillating in a low frequency band, the capacitance value and the inductance value are increased. 2. The first and second feedback capacitors are connected in series with each other, have a connection point connected to an emitter, and have both ends connected to a base and a collector at a high frequency. The third and fourth feedback capacitors are connected in series and connected to each other at the emitter of the oscillation transistor by a first switch diode, and both ends of the base and the collector are connected at a high frequency. When the voltage controlled oscillation circuit oscillates in the low frequency band, the first switch diode is turned on to connect the first feedback capacitor and the third feedback capacitor in parallel, and When connecting a second feedback capacitor and the fourth capacitor in parallel and oscillating in the high frequency band, the first switch is used. 2. The two-band oscillator according to claim 1, wherein the switch diode is turned off. 3. The impedance circuit has at least a first parallel resonance circuit and a second parallel resonance circuit connected in series to the first parallel resonance circuit, and has a resonance frequency of the first parallel resonance circuit. 3. The method according to claim 1, wherein the frequency is set to be substantially the same as the frequency of the low frequency band, and the resonance frequency of the second parallel resonance circuit is set to be substantially the same as the frequency of the high frequency band. Band oscillator. 4. The second inductance element comprising a first inductance element and a second inductance element connected in series to the first inductance element, wherein both ends of the second inductance element are short-circuited to each other. When the voltage controlled oscillation circuit is oscillated in the low frequency band, the second switch diode is turned off, and when oscillated in the high frequency band, the second switch diode is provided. 4. The device according to claim 1, wherein the device is electrically connected.
A two-band oscillator according to claim 1. 5. The buffer circuit includes an amplifying transistor, and a parallel tuning circuit having one end connected to the collector of the amplifying transistor and the other end grounded at a high frequency, and has a series connection between the collector and the ground. Providing a connected capacitor and a third switch diode, setting the tuning frequency of the parallel tuning circuit to be substantially the same as the frequency of the high frequency band, and oscillating the voltage controlled oscillation circuit in the low frequency band. Wherein said third switch diode is turned on to connect said capacitor in parallel with said parallel tuning circuit so that its tuning frequency is substantially the same as the frequency of said lower frequency band. 5. The two-band oscillator according to any one of 4.