JPS61134113A - Band switching circuit - Google Patents

Abstract

PURPOSE:To simplify constitution by connecting plural coils of a high frequency amplifying section and transmitting section to a high frequency amplifying section and an oscillating section through a one-way element. CONSTITUTION:Coils L11, L12 of a high frequency amplifying section 21 and coils L13, L14 of an oscillating section 23 are provided with diodes D11-D14. When a band changing switch S4 is on a contact S42 side, the coil L11 is connected to the high frequency amplifying section 21 by the action of the diode D11, and a resonance circuit is constituted together with a variable capacitor C11. The same applies to the oscillating section 22, and thereby the first band is received. When the switch S4 is on a contact 43 side, the second band is received similarly. Thus, it becomes unnecessary to provide a high frequency amplifying section, a mixing section and an oscillating section corresponding to receiving band respectively. Further, duplex type variable capacitors C11, C12 are enough for the purpose, and one band changing switch S4 will do.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a band switching circuit, and particularly to one capable of performing multi-band switching with a simple configuration.

[Technical Background of the Invention] As is well known, a band switching circuit for VHF and UHF bands in a conventional tuner device is configured as shown in FIG. That is, in the figure, S1 to S3 are band changeover switches, and each of the movable pieces 811 to 331 interlocks with the first and second fixed contacts S12 to 332 and 81.
3 to 833 are selectively connected. and,
Now, the movable piece 811 of each band changeover switch 81-S3
831 is switch-connected to the first fixed contacts 812 to 332, via the band changeover switch S3,
High frequency amplification section 11. DC voltage +8 is now applied to the mixing section 12 and the oscillating section 13, and the high frequency amplifying section 11.
The mixing section 12 and the oscillating section 13 are brought into a driving state. Then, the received signal supplied to the input terminal 14 is transferred to the band selection switch S1. Via a high frequency amplification section 11 having a resonant circuit 15 consisting of a variable capacitor C1 and a coil L1,
It is supplied to the mixing section 12. This mixing section 12 mixes the signal output from the high frequency amplification section 11 and the local oscillation signal output from the oscillation section 13 whose oscillation frequency is determined by the variable capacitor C2 and the coil 2 to generate an intermediate frequency signal. Then, the intermediate frequency signal is outputted from the output terminal 16 via the band changeover switch S2, and the first band is received here.

Moreover, the movable piece 811 of each band changeover switch 81 to S3
331 are switch-connected to the second fixed contacts 513-333, the high-frequency amplifying section 17. DC voltage element B is now applied to the mixing section 18 and the oscillating section 19, and the cough high frequency amplifying section 17
．． The mixing section 18 and the oscillating section 19 are brought into a driving state. Then, the received signal supplied to the input terminal 14 is transferred to the band selection switch S1. The signal is supplied to the mixing section 18 via the high frequency amplifying section 11 having a resonant circuit 20 consisting of a variable capacitor C3 and a coil L3. This mixing section 18 mixes the signal output from the high frequency amplification section 17 and the variable capacitor C4.
and a local oscillation signal output from the oscillation unit 19 whose oscillation frequency is determined by the coil L4 to obtain an intermediate frequency signal, and output the intermediate frequency signal from the output terminal 16 via the band selection switch S2. At this point, the second band is received.

[Problems in the Background Art] However, in the conventional band switching circuit as described above, the high frequency amplifying section 11.17, the mixing section 12.18, the oscillating section 13, 19, etc. are provided for each of the first and second receiving bands. However, the structure is complicated and economically disadvantageous. In addition, in particular, each of the variable capacitors 01 to C4 uses a 4-channel variable capacitor, so they are large in size, and the band selection switch 8
The number of units 1 to S3 is also large, which also makes the configuration complicated and disadvantageous in terms of economy.

[Object of the Invention] The present invention has been made in consideration of the above circumstances, and an object of the present invention is to provide an extremely good band switching circuit that is simple in structure and economically advantageous.

[Summary of the Invention] That is, the band switching circuit according to the present invention includes a high frequency amplifying section having a first variable capacitor and to which a received signal is supplied, and a first variable capacitor interlocked with the first variable capacitor of the high frequency amplifying section. an oscillation section having a second variable capacitor and generating a reference frequency signal for local oscillation; a mixing section generating an intermediate frequency signal by mixing each signal output from the high frequency amplification section and the oscillation section; and a changeover switch for band changeover having a second position, and this changeover switch having a first position.
a first unidirectional element in which a first inductance element is electrically connected to the high frequency amplification section in a state where the first variable capacitor and the first inductance element are in a position of a second unidirectionality in which the second inductance element is electrically connected to the oscillation section with the changeover switch in the first position, and the oscillation frequency is determined by the second variable capacitor and the second inductance element; element, and a third inductance element is electrically connected to the high frequency amplifier with the changeover switch in the second position, and the first variable capacitor and the third inductance element constitute a resonant circuit. With the changeover switch in the second position, the fourth inductance element is electrically connected to the oscillation section, and the second variable capacitor and fourth inductance element adjust the oscillation frequency. By including a fourth unidirectional element that determines the value, the configuration is simplified and economically advantageous.

[Embodiment of the Invention] Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. In FIG. 1, reference numerals 21, 22 and 23 denote a high frequency amplifying section, a mixing section, and an oscillating section, respectively, which are driven by a DC voltage element B constantly applied thereto. this house,
The high frequency amplification section 21 and the oscillation section 23 are provided with variable capacitors C11 and C12, respectively. This variable capacitor C11,012 is of a double type.

In addition, 84 in Fig. 1 is a band changeover switch, and the movable piece 3
41 is selectively connected to first and second fixed contacts 842 and 843. Now, if the movable piece S41 of the band changeover switch S4 is switched and connected to the first fixed contact 342, the coil L11 will be electrically connected to the high frequency amplification section 21 due to the action of the diode Q11. , variable capacitor C11 and coil Ll
1 constitutes a resonant circuit, and the diode 01
3, the coil L13 is electrically connected to the oscillation section 22, and the variable capacitor C12 and the coil L
13, the oscillation frequency of the oscillation section 23 is determined.

Therefore, the received signal supplied to the input terminal 24 is supplied to the mixing section 22 via the high frequency amplification section 21 having a resonant circuit including a variable capacitor C1l and a coil L11. This mixing section 22 mixes the signal output from the high frequency amplification section 21 and the local oscillation signal output from the oscillation section 23 whose oscillation frequency is determined by the variable capacitor C12 and the coil 113 to obtain an intermediate frequency signal. , the intermediate frequency signal is outputted from the output terminal 25, and the first band is received here.

Further, if the movable piece S41 of the band changeover switch S4 is switched and connected to the second fixed contact 343, the coil L12 is connected to the high frequency amplification section 2 by the action of the diode D12.
1, and the variable capacitor C
11 and the coil L12 constitute a resonant circuit, and the recoil L14 is electrically connected to the oscillating section 22 by the action of the diode [ ) 14, and the variable capacitor C12 and the coil 114 The oscillation frequency of will be determined.

Therefore, the received signal supplied to the input terminal 24 is supplied to the mixing section 22 via the high frequency layer width section 21 having a resonant circuit made up of a variable capacitor C11 and a coil L12. This mixing section 22 mixes the signal output from the high frequency amplification section 21 and the local oscillation signal output from the oscillation section 23 whose oscillation frequency is determined by the variable capacitor CI2 and the coil L14 to obtain an intermediate frequency signal. , the intermediate frequency signal is outputted from the output terminal 25, and the second band is received there.

Therefore, according to the configuration of the above embodiment, the coils L11 . L12 is selectively electrically connected to the high frequency amplification section 21, and the coil [1
3. Since L14 is selectively electrically connected to the oscillation section 23, there is no need to provide a high frequency amplification section, a mixing section, and an oscillation section for each reception band as in the conventional case, and the variable Since the capacitors C11 and C12 only need to be of the two-way type, and only one band changeover switch S4 is required, the configuration is extremely simple, which can effectively promote downsizing and is economically advantageous.

It should be noted that the present invention is not limited to the above-mentioned embodiments, and can be implemented with various modifications without departing from the gist thereof.

[Effects of the Invention] Therefore, as described in detail above, according to the present invention, it is possible to provide an excellent band switching circuit that has a simple configuration and is economically advantageous.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing an embodiment of a band switching circuit according to the present invention, and FIG. 2 is a circuit diagram showing a conventional band switching circuit. 11... High frequency amplification section, 12... Mixing section, 13...
- Oscillation section, 14... input terminal, 15... resonant circuit,
16... Output terminal, 17... High frequency amplification section, 18.
...Mixing section, 19... Oscillation section, 20... Resonance circuit,
21... High frequency amplification section, 22... Mixing section, 23...
- Oscillation section, 24...input terminal, 25...output terminal.

Claims (1)

[Claims] A high-frequency amplification section that has a first variable capacitor and is supplied with a received signal, and a second variable capacitor that is linked to the first variable capacitor of the high-frequency amplification section that generates a reference frequency signal for local oscillation. an oscillation section that mixes each signal output from the high frequency amplification section and the oscillation section to generate an intermediate frequency signal; a changeover switch for band switching having first and second positions; A first one-way direction in which a first inductance element is electrically connected to the high frequency amplification section with the changeover switch in a first position, and a resonant circuit is configured by the first variable capacitor and the first inductance element. a second inductance element is electrically connected to the oscillation section with the changeover switch in the first position;
a second unidirectional element that determines an oscillation frequency using a variable capacitor and a second inductance element, and a third inductance element that is electrically connected to the high frequency amplification section with the changeover switch in a second position. a third unidirectional element in which the first variable capacitor and the third inductance element form a resonant circuit, and a fourth inductance element in the oscillation section with the changeover switch in the second position. and a fourth unidirectional element that is electrically connected to the second variable capacitor and the fourth inductance element to determine the oscillation frequency.