JP2002026653A - Oscillator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an oscillator that can obtain oscillated signals with nearly a constant level over the entire band of oscillated frequencies. SOLUTION: The oscillator is provided with an oscillation circuit section 10 that has an oscillation transistor (TR) 11 and whose oscillated frequency is variable and with a common base amplifier circuit section 20 that has an amplification TR 21 whose emitter is directly connected to the collector of the oscillation TR 11 and amplifies the oscillated signal outputted from the oscillation circuit section 10. The collector of the oscillation TR 11 is directly connected to the emitter of the amplification TR 21, a common bias current is supplied to the oscillation TR 11 and the amplification TR 21, a connecting point between the collector of the oscillation TR 11 and the emitter of the amplification TR 21 is connected to ground via a series resonance circuit 13 consisting of an inductive element 13a and a capacitor 13b so as to lower the resonance frequency of the series resonance circuit more than the minimum frequency of a changing range of the oscillated frequency.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to an oscillation circuit section,
The present invention relates to an oscillator having an amplification circuit for amplifying an oscillation signal output from an oscillation circuit.

[0002]

2. Description of the Related Art FIG. 2 shows the configuration of a conventional oscillator. An oscillation circuit section 40 has an oscillation transistor 41 and a resonance circuit 42, and the collector of the oscillation transistor 41 is a capacitor 4
3, and the emitter is grounded via an emitter bias resistor 44. Feedback capacitors 45 and 46 are connected between the base and the emitter and between the emitter and the ground, respectively. The capacitor 43 has a capacitance value that enables the oscillation circuit section 40 to oscillate with a collector-grounded type and has a reactance enough to output an oscillation signal from the collector. Therefore, the collector is not grounded almost completely in terms of high frequency, but is made to float to some extent from the ground.

The resonance circuit 42 includes a resonance line (constituted by a microstrip line) 42a and a varactor diode 42b.
And one end of the resonance line 42a and the cathode of the varactor diode 42b are grounded,
The other end of the resonance line 42a is connected to the base of the oscillation transistor 41 by the coupling capacitor 42c, and is connected to the cathode of the varactor diode 42b via the DC cut capacitor 42d.

The varactor diode 42b has a cathode connected to a control terminal 48 via a choke inductor 47. The control terminal 48 is grounded at a high frequency by a DC cut capacitor 49. Then, a voltage for changing the capacitance of the varactor diode 42b is applied to the terminal 48.

The amplification circuit section 50 has an amplification transistor 51, the emitter of which is directly connected to the collector of the oscillation transistor 41, the collector of which is connected to a power supply terminal 53 via a choke inductor 52, and the voltage V
b is applied. The power supply terminal 53 is grounded at a high frequency by a DC cut capacitor 54. The collector is grounded by a capacitor 55, and the coupling capacitor 56
Is connected to the output terminal 57 via the. Further, the base of the amplification transistor 51 is grounded at a high frequency by a DC cut capacitor 58. As a result, the amplification circuit unit 50
Constitutes a grounded-base amplification circuit.

Then, a bias voltage is applied to each base of the oscillation transistor 41 and the amplification transistor 51 by base bias resistors 61, 62 and 63 connected in series between the power supply terminal 53 and the ground. As a result, a common bias current flows through the oscillation transistor 41 and the amplification transistor 51.

The oscillation frequency changes by changing the voltage applied to the control terminal 48, and the oscillation signal is input to the emitter of the amplification transistor 51 output from the collector of the oscillation transistor 41. The amplified oscillation signal is output from the collector of the amplification transistor 51.

[0008]

In the above-mentioned conventional oscillator, the signal is output from the emitter of the oscillation transistor 41 and input to the emitter of the amplification transistor 51.
Since the capacitor 43 has a capacitance value that is a reactance enough to output an oscillation signal from the collector of the oscillation transistor 41, the collector is not completely grounded at high frequency, but is floated to some extent from the ground. . Therefore, the level of the oscillation signal bypassed to the ground via the capacitor 43 increases as the frequency increases. Therefore, the level of the oscillation signal input to the emitter of the amplification transistor 51 is high when the oscillation frequency is low, but decreases when the fractional number increases, and the frequency characteristic of the oscillation signal output from the amplification transistor 51 decreases to the right. Will have.

Therefore, an object of the oscillator of the present invention is to obtain an oscillation signal of a substantially constant level over the entire oscillation frequency range.

[0010]

Means for Solving the Problems To solve the above problems,
The oscillator of the present invention has an oscillation circuit portion having an oscillation transistor and an oscillation frequency variable, and a base is grounded at a high frequency,
An emitter has an amplification transistor directly connected to the collector of the oscillation transistor, and further includes a grounded-base amplification circuit for amplifying an oscillation signal output from the oscillation circuit, wherein the collector of the oscillation transistor and the amplification transistor are provided. And a common bias current is applied to the oscillation transistor and the amplification transistor, and a connection point between the collector of the oscillation transistor and the emitter of the amplification transistor is connected to a series resonance circuit including an inductance element and a capacitor. And the resonance frequency of the series resonance circuit is set lower than the lowest frequency in the change range of the oscillation frequency.

The resonance frequency is set to 6/10 to 7/10 of the lowest frequency.

[0012]

FIG. 1 shows the configuration of an oscillator according to the present invention. An oscillation circuit section 10 has an oscillation transistor 11 and a resonance circuit 12, and the resonance circuit 12 is connected between the base of the oscillation transistor 11 and the ground. Connected to. The collector of the oscillation transistor 11 is grounded by a series resonance circuit 13 including an inductance element 13a and a capacitor 13b. The emitter is grounded via an emitter bias resistor 14. Further, feedback capacitors 15 and 16 are provided between the base and the emitter and between the emitter and the ground, respectively.
Is connected.

The resonance frequency of the series resonance circuit 13 is set to be lower than the lowest frequency in the range of change of the oscillation frequency. At the oscillating frequency, the oscillating circuit section 10 oscillates with the collector grounded, and furthermore, the inductance value of the inductance element 13a and the capacitor 1 so that the reactance is such that an oscillating signal can be output from the collector.
3b is determined. Therefore, at the oscillation frequency, the collector is not almost completely grounded in terms of high frequency, but is floated to some extent from the ground.

The resonance circuit 12 includes a resonance line (constituted by a microstrip line) 12a and a varactor diode 12b.
And one end of the resonance line 12a and the cathode of the varactor diode 12b are grounded.
The other end of the resonance line 12a is connected to the base of the oscillation transistor 11 by a coupling capacitor 12c, and is connected to the cathode of the varactor diode 12b via a DC cut capacitor 12d.

The cathode of the varactor diode 12b is connected to a control terminal 18 via a choke inductor 17. The control terminal 18 is grounded at a high frequency by a DC cut capacitor 19. Then, a voltage for changing the capacitance of the varactor diode 12b is applied to the terminal 18.

The amplification circuit section 20 has an amplification transistor 21 whose emitter is directly connected to the collector of the oscillation transistor 11 and whose collector is connected to a power supply terminal 23 via a choke inductor 22. The power terminal 23 is grounded at a high frequency by a DC cut capacitor 24. Further, a voltage Vb is applied to the power supply terminal 23. The collector is grounded by a capacitor 25 for impedance matching, and the output terminal 27
Connected to. Further, the base is grounded at a high frequency by a DC cut capacitor 28. Therefore, the amplifier circuit section 20 constitutes a grounded-base amplifier circuit.

A bias voltage is applied to each base of the oscillation transistor 11 and the amplification transistor 21 by base bias resistors 31, 32, and 33 connected in series between the power supply terminal 23 and the ground. As a result, a common bias current flows through the oscillation transistor 11 and the amplification transistor 21. The oscillation frequency changes by changing the voltage applied to the control terminal 18.

In the above configuration, the series resonance circuit 13 has an inductive reactance at the oscillation frequency. Therefore, the reactance increases as the frequency increases,
The ratio of the oscillation signal bypassed to the ground via the series resonance circuit 13 decreases, and the amplification transistor 21
Is injected into the emitter. On the other hand, the level of the oscillation signal tends to decrease as the oscillation frequency increases. As a result, the level of the oscillation signal at the emitter of the amplification transistor 21 becomes flat in the oscillation frequency range.

If the series resonance frequency is set to 6/10 to 7/10 of the lowest frequency in the oscillation frequency range, the oscillation circuit section 10 can operate stably and be flat. 6/1
If it is lower than 0, the reactance of the resonance circuit 13 becomes too large at the oscillation frequency and the oscillation circuit unit 10 does not transmit stably, and if it is higher than 7/10, the oscillation signal input to the emitter of the amplification transistor 21 The level becomes too low and an oscillation signal of a sufficient level cannot be obtained.

[0020]

As described above, the oscillator of the present invention has the following features.
Since the connection point between the collector of the oscillation transistor and the emitter of the amplification transistor was grounded via a series resonance circuit composed of an inductance element and a capacitor, and the resonance frequency of the series resonance circuit was lower than the lowest frequency of the change range of the oscillation frequency, The series resonance circuit has an inductive reactance at the oscillation frequency.The higher the frequency is, the larger the reactance is. You. On the other hand, since the level of the oscillation signal tends to decrease as the oscillation frequency increases, the level of the oscillation signal at the emitter of the amplification transistor becomes flat in the oscillation frequency range.

The resonance frequency is set to the lowest frequency of about 6
Since the ratio is set to / 10 to 7/10, the oscillation circuit section can be operated stably and can be made flat.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing a configuration of an oscillator according to the present invention.

FIG. 2 is a circuit diagram showing a configuration of a conventional oscillator.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Oscillation circuit part 11 Oscillation transistor 12 Resonance circuit 12a Resonance line 12b Varactor diode 12c Coupling capacitor 12d DC cut capacitor 13 Series resonance circuit 13a Inductance element 13b Capacitor 14 Emitter bias resistance 15, 16 Feedback capacitor 17 Choke inductor 18 Control terminal 19 DC cut Capacitor 20 Amplification circuit part 21 Amplification transistor 22 Choke inductor 23 Power supply terminal 24 DC cut capacitor 25 Impedance matching capacitor 26 Coupling capacitor 27 Output terminal 28 DC cut capacitor 31, 32, 33 Base bias resistance

Claims (2)

[Claims] 1. An oscillation circuit section having an oscillation transistor and having a variable oscillation frequency, an amplification transistor having a base grounded at a high frequency and an emitter directly connected to a collector of the oscillation transistor, and further comprising: A grounded-base amplification circuit unit for amplifying the output oscillation signal, wherein a collector of the oscillation transistor and an emitter of the amplification transistor are directly connected to each other, and a bias current common to the oscillation transistor and the amplification transistor is supplied. And a connection point between the collector of the oscillation transistor and the emitter of the amplification transistor is grounded via a series resonance circuit including an inductance element and a capacitor, and the resonance frequency of the series resonance circuit is set to the lowest frequency in the variation range of the oscillation frequency. An oscillator characterized by being lower than the above. 2. The method according to claim 1, wherein said resonance frequency is 6 /
2. The oscillator according to claim 1, wherein the ratio is set to 10 to 7/10.