JPS6384308A - Tuning circuit - Google Patents

Abstract

PURPOSE:To ensure the control of Q of a tuning circuit by connecting a series connected matter of a 2nd controllable coil and a resistor in parallel to a 1st controllable coil to form a tuning inductance. CONSTITUTION:A turning inductance of a tuning circuit is formed by connecting a series connected matter of the 2nd controllable coil 11 and a resistor 12 in parallel to the 1st controllable coil 10. Then the inductance of the coil 10 is roughly controlled; while the inductance of the coil 11 is finely controlled. As a result, the damping effect produced by the resistance 12 is reduced and Q of the tuning circuit is increased. If said control of inductance is reversed between both coils 10 and 11, the damping effect of the resistor 12 is increased with the Q reduced respectively. Thus the Q of the tuning circuit can be controlled.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a tuning circuit that allows Q to be adjusted.

(Prior Art) FIG. 2 shows a circuit diagram of an example of a double tuning circuit using a conventional tuning circuit. In Fig. 2, input terminal 2 and local oscillator 3 are connected to the drain of FET 1, and the signal applied to input terminal 2 and the oscillation signal output from local oscillator 3 are mixed and output from the source of FET 1. . The source of this FET 1 is an adjustable independent coil 4.
and a pattern coil 5 formed on a printed circuit board, which are connected in parallel to each other. Furthermore, the independent coil 4
Another self-supporting coil 6 is provided electromagnetically coupled to the self-supporting coil 6, one end of this self-supporting coil 6 is grounded, and the other end is connected to one end of a capacitor 7. The other end of this tuning capacitor 7 is grounded via another tuning capacitor 8 and connected to an output terminal 9.

In such a configuration, the freestanding coil 4 and the patterned coil 5
A primary side tuned circuit is formed by the combined inductance Ll and a capacitance CI between the source and gate of FETI, and a secondary side tuned circuit is formed by the self-supporting coil 6 and the tuning capacitor 7.8. A signal with an appropriate tuning frequency is output to the output terminal 9 due to the resonance characteristics of the primary and secondary tuning circuits.

By the way, when the tuning frequency is, for example, 600 MHz, the tuning inductance Ll of the primary side tuning circuit has a very small value. Therefore, if we try to form the primary-side tuning inductance Ll using a single independent coil 4, the inductance value will vary widely, making it unsuitable for mass production, and the rate of change in the inductance value due to adjustment will be too large, making adjustment difficult. It's complicated.

Therefore, the independent coil 4 and the pattern coil 5 are connected in parallel to reduce the influence of the independent coil 4 on the inductance value L1, thereby facilitating production and adjustment.

(Problems to be Solved by the Invention) In the conventional tuning circuit described above, the tuning frequency can be adjusted by adjusting the independent coil 4 in response to variations in the capacitance CI between the source and gate of the FETI. Variations in the Q of the tuned circuit due to variations in the resistance component between the source and gate cannot be adjusted. For this,
There was a problem in that it was not possible to adjust variations in the characteristics of the resonance curve of the double-tuned circuit.

SUMMARY OF THE INVENTION An object of the present invention was to solve the problems of the conventional tuning circuit described above, and to provide a tuning circuit in which Q can be adjusted.

(Means for Solving the Problems) In order to achieve the above object, the tuning circuit of the present invention has a tuning inductance that is composed of an adjustable first coil, an adjustable second coil, and a resistor. It is configured by connecting a series connection body and a parallel connection body.

(Function) If the inductance value of the first coil is adjusted to a large value and the inductance value of the second coil is adjusted to a small value, the damping effect due to the resistance will be reduced and the Q of the tuned circuit will be reduced.
becomes larger. Conversely, if the first coil is made smaller and the second coil is adjusted larger, the damping effect due to the resistance becomes stronger and the Q of the tuned circuit becomes smaller.

(Description of Examples) Hereinafter, examples of the present invention will be described with reference to FIG. FIG. 1 is a circuit diagram of an embodiment of a double tuning circuit using the tuning circuit of the present invention. In FIG. 1, circuit elements that are the same as those in FIG. 2 are given the same reference numerals and redundant explanations will be omitted.

In Fig. 1, the difference from Fig. 2 is that FET1
a first independent coil 10 whose source is adjustable; a series connection body of a second adjustable independent coil 11 and a resistor 12;
are grounded in parallel.

In such a configuration, the first and second independent coils 1
．． 0. The tuning frequency can be adjusted by adjusting the tuning inductance L1 as appropriate by adjusting II. Further, it is possible to adjust the Q variation of the tuning circuit due to the variation in the resistance component between the source and gate of the FETI as follows. That is, the first self-supporting coil 10
If the inductance value of the second independent coil 11 is increased and the inductance value of the second self-supporting coil 11 is adjusted to be small, the damping effect of the resistor 12 can be reduced and the Q of the tuned circuit can be increased. Conversely, if the inductance value of the first self-supporting coil 10 is made small and the inductance value of the second self-supporting coil 11 is adjusted to a large value, the resistance 1
The damping effect of step 2 becomes stronger and the tuning circuit Q can be made smaller. In these adjustments of Q, the value of the tuning inductance L1 obtained by combining the first and second independent coils 10.11 is adjusted to be constant.

In addition, in the said Example, although the tuning circuit was demonstrated using a double tuning circuit, it is needless to say that it is not limited to this.

(Effects of the Invention) As explained above, according to the tuning circuit of the present invention, Q can be adjusted without affecting the tuning frequency. If the tuning circuit of the present invention is used in a double tuning circuit, an excellent effect can be obtained in that the characteristics of the resonance curve can be adjusted.

[Brief Description of the Drawings] Fig. 1 is a circuit diagram of an embodiment of a double-tuned circuit in which the tuning circuit of the present invention is used, and Fig. 2 is a circuit diagram of an embodiment of a double-tuned circuit in which a conventional tuning circuit is used in the double-tuned circuit. FIG. 2 is an example circuit diagram. 10: First self-supporting coil, 11: Second self-supporting coil, J2: Resistor.

Claims (1)

[Claims] a first coil whose tuning inductance is adjustable;
1. A tuning circuit comprising a series connection body of an adjustable second coil and a resistor connected in parallel.