JP2940053B2 - Oscillator - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an oscillator used for a frequency converter of a cable television receiver.

2. Description of the Related Art In recent years, cable television (CATV) has become widespread, and a high-frequency oscillation device is used for the receiver.

FIG. 5 shows a conventional general oscillation device. As shown in the figure, the transistor 1 is grounded to the base and the capacitor 4
And a feedback from the capacitor 3 to form a Colpitts-type oscillation circuit. The collector is supplied with current from the terminal 16 through a series circuit of the resistor 11 and the choke coil 14, and is tuned through the capacitor 8 as a high-frequency load. Capacitance 5, tuning line 15, coupling capacitor 6, and variable capacitor 7
Are connected. The anode of the variable capacitor 7 is connected to the ground, the cathode is connected to the capacitor 6, and the resistor 13 is connected to a terminal 17. An external voltage is applied between the terminal 17 and the ground to change the capacitance of the variable capacitor 7 and change the oscillation frequency.

The line 22 provided close to the tuning line 15 is connected to the ground at both ends to form a short-circuit line, and is connected to the tuning line 15. The line 22 has a role of a trimmer for finely adjusting the oscillation frequency according to the degree of coupling to the tuning line 15.

Problems to be Solved by the Invention In such a conventional oscillating device, it is desired that a high-frequency load is high as a preferable oscillating condition. To this end, the impedance of the resistor 11 and the choke coil 14 parallel to the high-frequency load is reduced by Therefore, it is necessary to make the load sufficiently large as compared with the high-frequency load. However, the resistor 11 has a low resistance value in order to increase the power supply voltage supplied to the transistor 1, and therefore, a choke coil 14 having a large inductance is necessarily used. This is a major obstacle in integrating the oscillation circuit into small blocks. The same applies to the trimmer for fine adjustment of the frequency.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and has as its object to provide an oscillation device which uses a choke coil having a small inductance and does not require a trimmer for fine frequency adjustment.

Means for Solving the Problems In order to achieve the above object, the present invention provides a Colpitts-type oscillation circuit with a base connected to the ground at high frequency, wherein the collector of the transistor is grounded by a first tuning capacitor. Connected to one end of a tuning line formed in a pattern, and the other end of the tuning line is connected to ground by a second capacitor, and connected to a power supply by a series circuit of a resistor and a choke coil. The oscillation frequency is adjusted by setting the choke coil as an inductor whose inductance can be adjusted.

Operation According to the above configuration, the current of the transistor is supplied through the tuning line, the choke coil, and the resistor, and the first tuning capacitor, the tuning line, and the second capacitor form a high-frequency load and oscillate. The inductance adjustment can change the oscillation frequency slightly.

Embodiment Hereinafter, an oscillator according to an embodiment of the present invention will be described with reference to FIG.

As shown in the figure, the base of an oscillating transistor 1 is connected to ground at a high frequency by a capacitor 2, and a collector
A capacitor 4 is connected between the emitters, a capacitor 3 is connected between the emitter and the base,
And the capacitor 3 provides feedback for oscillation. The emitter is connected to ground via a resistor 12, the capacitor 3 and the base are connected to ground via a resistor 10,
The collector is connected to ground by a tuning capacitor 5 and to a series circuit of a coupling capacitor 6 and a resistor 11 and a choke coil 18 by a tuning line 15. The other end of the coupling capacitor 6 is connected to ground via a variable capacitance diode 7, and the other end of the series circuit of the resistor 11 and the choke coil 18 is connected to a power terminal 16. The anode of the variable capacitance diode 7 is connected to the ground, the cathode is connected to the coupling capacitor 6, and the resistor 13 is connected to a terminal 17. The choke coil 18 has an inductance smaller than that used in a conventional circuit by about several tenths, and the inductance is adjustable.

The operation of the above configuration will be described.
Is grounded at a high frequency by a capacitor 2 and grounded, and a capacitor 3 and a capacitor 4 provide feedback of oscillation. A high-frequency load comprising a tuning capacitor 5, a tuning line 15, a coupling capacitor 6 and a variable capacitance diode 7 is connected to the collector, and a current is supplied from a terminal 16 via a resistor 11 and a choke coil 18. The variable capacitance diode 7 is supplied with a reverse voltage from the terminal 17 via the resistor 13 and becomes a part of the tuning capacitance as an electric capacitance. A coupling capacitor 6 connects the variable capacitance diode 7 to the tuning line at a high frequency. The tuning line 15 not only operates as a tuning inductance but also serves as a current path for the transistor 1. The choke coil 18 differs from that of the conventional circuit array in that the inductance is small, so that it does not simply function as a high-frequency stopper for supplying DC current.
It functions as a coil having the resistor 11 for the loss.

Therefore, oscillation occurs at a frequency substantially determined by the inductance of the tuning line 15, the capacitance of the capacitors 5 and 7, and the inductance of the choke coil 18.
And the high frequency loss caused by the resistor 13 is reflected on the collector (normally, the capacitance value of the capacitor 6 is sufficiently larger than that of the variable capacitance diode 7 and operates as a DC stopper).

At this time, the high-frequency loss due to the resistor 13 is the same as that of the conventional example, and the description of comparison with the conventional example is omitted.

The amount by which the high-frequency loss due to the resistor 11 is reflected on the collector is related to the capacitance values of the capacitor 5 and the variable capacitance diode 7. When the maximum value of the variable capacitance diode 7 in which the capacitance value changes is set to about the capacitance value of the capacitor 5 and the minimum value is set to about a fraction of the capacitance value of the capacitor 5, The reflected loss is the same at worst as compared with the case where the same amount of loss is directly connected to the collector, and it becomes more advantageous as the capacitance of the variable capacitance diode 7 decreases and the oscillation frequency increases. Also,
The change in the impedance of the connection point of the variable capacitance diode 7 with respect to the oscillation frequency is also advantageous. When the capacitance of the variable capacitance diode 7 decreases and the frequency increases, the impedance of the choke coil 18 follows and increases. It helps to reduce the inductance.

Such a smaller choke coil 18 can be easily incorporated in a block in which the oscillation device is compactly assembled, and FIG. 3 shows an embodiment thereof.

In the figure, the numbers assigned to each component correspond to the numbers in FIG. Small electric components are arranged on the circuit wiring printed on the circuit board 19, and the tuning line 15 and the choke coil
Reference numeral 18 is configured as a part of the printed wiring. Since the choke coil 18 has a small inductance, it is easily realized on a circuit board.

Also, the choke coil 18 is not simply a DC stopper,
As described above, it is involved in the reactance that determines the oscillation frequency. Therefore, this choke coil
The oscillation frequency can be finely adjusted by changing the amount of inductance of 18, and the conventional trimmer can be omitted. For example, as shown in FIG.
Is added to the outside, the choke coils 18 and 20 are combined to constitute one choke coil, and the frequency can be finely adjusted by adjusting the external choke coil 20.

Therefore, it is not necessary to provide the frequency fine adjustment trimmer inside the oscillation device. Further, the inductance of the coil 20 can be easily changed by changing the winding interval of the air-core coil with a driver or the like, for example, as conventionally performed.

FIG. 2 shows a circuit of an oscillating device according to a second embodiment of the present invention. The oscillating device has a fixed frequency obtained by removing the variable capacitance diode 7, the resistor 13, and the terminal 17 from the circuit of the embodiment of FIG. FIG. 4 shows an example of parts.

As described above, according to the oscillating device of the embodiment of the present invention, in the Colpitts type oscillating circuit with the base of the transistor 1 connected to the ground at high frequency, the collector is connected to the ground by the first tuning capacitor 5. The other end of the tuning line 15 is connected to the ground by a second capacitor 6 and to the power supply by a series circuit of a resistor 11 and a choke coil 18.
With the configuration that makes 18 adjustable in inductance,
The inductance of the choke coil 18 can be reduced so that the choke coil 18 can be easily incorporated into the device, and the oscillation frequency can be finely adjusted by adjusting the choke coil 18.

Needless to say, another variable capacitance element may be used instead of the variable capacitance diode 7.

As is apparent from the above embodiments, the present invention relates to a Colpitts-type oscillation circuit having a grounded base connected to the base of a transistor at a high frequency, wherein the collector of the transistor is connected to the ground by a first tuning capacitor. Connected to one end of a tuning line formed in a pattern, the other end of the tuning line is connected to ground by a second capacitor, and connected to a power supply by a series circuit of a resistor and a choke coil. Is configured so that the inductance can be adjusted, so that the oscillation frequency can be adjusted.Therefore, the inductance of the choke coil can be reduced to be easily incorporated into the device, and fine adjustment of the oscillation frequency can be performed by adjusting the choke coil. it can.

[Brief description of the drawings]

FIG. 1 is a circuit diagram of an oscillator according to an embodiment of the present invention, FIG. 2 is a circuit diagram of an oscillator according to a second embodiment of the present invention, and FIG. FIG. 4 is a component arrangement diagram of the oscillator of the second embodiment of the present invention, and FIG. 5 is a circuit diagram of a conventional oscillator. DESCRIPTION OF SYMBOLS 1 ... Transistor, 2 ... Capacitor 5, 5 ... First tuning capacitor, 6 ... Coupling capacitor, 7 ... Variable capacitance diode, 11 ... Resistance, 15 ... Tuning line, 16 ... Power supply terminal (power supply ), 18 ... Choke coil.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) H03B 5/00-5/42 H01P 7/08

Claims (2)

(57) [Claims] In a Colpitts type oscillation circuit having a base connected to a ground in a high frequency manner, a collector of the transistor is connected to a ground by a first tuning capacitor, and a tuning line formed in a pattern is formed. Connected to one end, the other end of the tuning line is connected to ground by a second capacitor, and connected to a power supply by a series circuit of a resistor and a choke coil, and the oscillation frequency is adjusted by making the choke coil adjustable in inductance. Oscillation device. 2. The oscillation device according to claim 1, wherein said second capacitor comprises a coupling capacitor and a variable capacitance element connected in series.