JPH0611645Y2 - High frequency tuning circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application] The present invention relates to a high frequency tuning circuit having a wide variable range of a tuning frequency.

[Prior art]

Electronic tuning systems are used in currently marketed automotive receivers. In this tuning method, a voltage-controlled oscillator whose oscillation frequency changes according to the capacitance value of a variable capacitance diode is used as a local oscillator, and the oscillation frequency is changed according to the desired reception frequency so that a constant intermediate frequency is obtained from the mixer. There is. By the way, in such a receiver, since the distance from the antenna to the main body of the receiver is long, the stray capacitance of the antenna is large as compared with a typical portable receiver. Even if a high-frequency tuning circuit is configured using variable capacitance diodes, stray capacitance cannot be ignored for the capacitance value of the variable capacitance diode with a narrow variable range, so the variable range of the tuning frequency becomes narrow.

Therefore, it is difficult to provide a high frequency tuning circuit, and the high frequency input from the antenna is directly added to the mixer under the present circumstances.

Such a circuit configuration is not desirable because it reduces the selectivity of the receiver.

〔Task〕

An object of the present invention is to provide a high frequency tuning circuit having a wide tuning frequency variable range mainly depending on a reception frequency from a long wave band to a short wave band.

[Technical means for solving the problem]

The high-frequency tuning circuit of the present invention is connected to the output side of a transistor that amplifies a high-frequency input from an antenna. The current-controlled variable inductor that adjusts the inductance of the tuning coil by the current of the control coil and the voltage variable capacitance diode. It is characterized by connecting and.

〔Example〕

An embodiment of the high frequency tuning circuit of the present invention will be described below with reference to the circuit diagram of FIG. 1, which is shown merely as a tuning circuit.

In FIG. 1, the tuning circuit 1 is shown surrounded by a dotted line, and 2 is a DC power supply for supplying electric power for controlling the tuning circuit 1.

The tuning circuit 1 includes a tuning coil 3A of a current control type variable inductor (hereinafter referred to as a variable inductor) 3 and two voltage variable capacitance diodes (hereinafter referred to as a diode) 4, 5
Are connected in parallel. Reference numeral 3B is a control coil of the variable inductor 3 that changes the magnetic flux density inside the tuning coil 3A to adjust its inductance value.

A DC voltage is applied to the terminal 6 from the output terminal 7 of the power supply 2, and the capacitance values of the diodes 4 and 5 are adjusted. Terminal 8
, A DC voltage is applied from another terminal 9 of the power supply 2, and the current flowing through the control coil 3B is adjusted. Reference numeral 10 is a ground terminal connected to one end of the control coil 3B, and 11 is a ground terminal connected to one end of the tuning coil 3A and the diodes 4 and 5. 12 to 14 are variable resistors for biasing (including semi-fixed resistors), and 15 and 16 are capacitors for removing high frequency current.

As the variable inductor 3, for example, the one shown in the vertical sectional view of FIG. 2 may be used.

This variable inductor is disclosed in Japanese Patent Laid-Open No. 59-14822 and is composed of three cores.

The second core 19 is housed in the hollow portion 18 of the first core 17, and the first core 17 is housed in the pot-shaped third core 20. The magnetic path 22 of the control coil 21 wound around the first core 17 and the magnetic path 24 of the tuning coil 23 wound around the second core 19 overlap in the second core 19, and The effective magnetic permeability of the second core 19 can be controlled by changing the magnetic flux density, and the inductance value of the tuning core 23 can be adjusted.

The control coil 21 and the tuning coil 23 are respectively the control coil 3
Obviously, this corresponds to B and the tuning coil 3A.

FIG. 3 is a circuit diagram of a high frequency circuit portion of the receiver when the tuning circuit 1 is used as a high frequency tuning circuit.

In FIG. 3, 25 is an antenna and 26 is an antenna 25.
Field-effect transistor that amplifies high-frequency input from
Reference numeral 27 is a bipolar transistor that controls the drain current of the transistor 26 according to the output of the AGC circuit applied to the base. The tuning circuit 1 is connected to the output side of the transistor 26. Tuning coil 3A of tuning circuit 1
Is coupled to the coupling coil 28, and its tuning circuit 1
The circuit portion for controlling is not shown.

In such a tuning circuit of the present invention, the variable range of the inductance of the variable inductor 3 is 10.5 μH to 800 μH.
The variable range of the capacitance value of H and the diodes 4 and 5 is 25PF to 440P.
It can be easily set to F level.

Variable inductor 3 is 10.5μH and diodes 4 and 5 are respectively
The tuning frequency at 25 PF is 7 MHz, the tuning frequency at variable inductor 3 is 800 μH, and diodes 4 and 5 are 440 PF, respectively, the tuning frequency is 175 KHz.

Therefore, when used as a high frequency tuning circuit as shown in FIG. 3, this high frequency tuning circuit can be tuned to a wide range of high frequency inputs from the long wave band to the short wave band. Then, since only the high frequency input that has passed through the tuning circuit 1 can be added to the mixer, the selectivity of the receiver can be dramatically improved.

FIG. 4 is a circuit diagram showing another embodiment of the high-frequency tuning circuit of the present invention, but shows the configuration as a tuning circuit as in the first embodiment.

The tuning circuit 40 is shown surrounded by a dotted line, and the circuit portion for controlling the tuning circuit 40 has the same configuration as that of FIG.

The tuning circuit 40 has diodes 41 and 42 connected in parallel and a tuning coil 43A of a variable inductor 43 connected in series. 43B is a control coil of the variable inductor 43. The terminals 44 are connected to the diodes 41, 4 and 4 from the DC power supply 2.
A DC voltage for adjusting the capacitance value of 2 is applied, and a DC voltage for adjusting the current of the control coil 43B is applied to the terminal 45. 46 and 47 are ground terminals.

The tuning circuit 1 of FIG. 1 is a parallel tuning circuit, whereas the tuning circuit 40 of FIG. 4 is a series tuning circuit.

FIG. 5 is a circuit diagram showing still another embodiment of the high frequency tuning circuit of the present invention.

In FIG. 5, the tuning circuit 50 and the tuning circuit 51 surrounded by a dotted line are shown.
Are combined to form a double-tuned circuit.

The tuning circuit 50 includes a tuning coil 52 of a variable inductor 52.
A and the diodes 66 and 53 are connected in parallel. In the tuning circuit 51, the tuning coil 54A of the variable inductor 54 and the diodes 55 and 56 are connected in parallel. Tuning coil 5
A portion 54C of 4A is coupled to the tuning coil 52A.

52B is a control coil of the variable inductor 52, and 54B is a control coil of the variable inductor 54. DC voltages for adjusting the capacitance values of the diodes 66 and 53 and the diodes 55 and 56 are applied to the terminals 57 and 58, respectively, and currents are applied to the control coils 52B and 54B to the terminals 59 and 60, respectively. A DC voltage for 6
Reference numeral 1 is a DC power source, and 62 to 65 are ground terminals.
A variable resistor (including a semi-fixed resistor) for bias and a capacitor for removing high frequency current are connected between the terminals 57-60 and the DC power supply 61.

The high frequency tuning circuit of the present invention can thus be configured as a single tuning circuit or a double tuning circuit. It is also possible to provide a tap on the tuning coil or to combine three tuning circuits.
A trimmer capacitor may be additionally connected to the tuning circuit. The configuration of the high frequency circuit part of the receiver when used as a high frequency tuning circuit is not limited to that shown in FIG.

〔effect〕

As described above, the high frequency tuning circuit of the present invention is configured by connecting the variable inductor and the diode as a circuit element that determines the tuning frequency. Since the inductance value of the variable inductor can be adjusted in a wide range, by combining with the variable range of the capacitance value of the diode, the variable range of the tuning frequency is 1.5 to 7 compared to the conventional case where only the capacitance value of the diode is changed. It can be doubled. The selectivity of the receiver can be dramatically improved by mainly using it as a high frequency tuning circuit in an electronic tuning type receiver having a large stray capacity and a long distance between the antenna and the receiver main body.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing an embodiment of a high frequency tuning circuit of the present invention, FIG. 2 is a sectional view of a variable inductor, and FIG. 3 is a high frequency circuit part of a receiver when the high frequency tuning circuit of the present invention is used. FIG. 4 is a circuit diagram showing another embodiment of the high-frequency tuning circuit of the present invention, and FIG. 5 is a circuit diagram showing another embodiment. 1 ... Tuning circuit, 2 ... DC power supply, 3 ... Variable inductor, 4, 5 ... Diode

Claims (1)

[Scope of utility model registration request] 1. A current control type variable inductor which is connected to an output side of a transistor for amplifying a high frequency input from an antenna and which adjusts an inductance of a tuning coil by a current of a control coil, and a voltage variable capacitance diode. A high-frequency tuning circuit characterized in that