JPS6338589Y2 - - Google Patents

Description

[Detailed description of the invention] The present invention relates to an antenna circuit that provides signals from an antenna to a receiver, and more specifically, selectively receives signals in two different frequency bands such as long waves and medium waves. The present invention relates to an antenna circuit for a receiver capable of receiving data.

FIG. 1 is a prior art electrical circuit diagram. The signal from the antenna 1 is fed from the antenna circuit 60 to the high frequency amplification circuit 51 of the superheterodyne receiver including the integrated circuit 54 and amplified, and this high frequency signal is given a local oscillation signal from the local oscillation circuit 52. The intermediate frequency signals obtained thereby are amplified by an intermediate frequency amplification circuit 53. The intermediate frequency amplified signal is demodulated by a detection circuit included in the integrated circuit 54, amplified by an amplifier circuit 56, and then sent to the speaker 5.
A tunable frequency signal is heard from 7. This receiver can receive signals in the long wave frequency band and the medium wave frequency band.

When receiving a signal in the long wave frequency band, the common contact 62 of the changeover switch 61 is electrically connected to the individual contact 63, and the changeover switch 6
5 common contacts 66 are electrically connected to individual contacts 67.
In addition, the common contact 70 of the switch 69 linked to these changeover switches 61 and 65 is the individual contact 71.
It is electrically conductive. Therefore, in the antenna circuit 60, the coils 3, 4, 5 and the capacitors 8, 9,
Tuning is performed by 10 and 12.

When receiving a medium wave frequency band, the common contact 62 of the changeover switch 61 is connected to the individual contact 64, the common contact 66 of the changeover switch 65 is connected to the individual contact 68, and at this time, the common contact 70 of the switch 69 is connected to the individual contact. 72 is conductive. As a result, in the antenna circuit 60, tuning is performed by the coil 3 and the capacitors 8, 9, and 10. During this medium wave reception, both terminals of the coil 4 are connected to the cut-off individual contacts 63 and 67 and are floating, so to speak, and are not connected to the rest of the circuit. Common contact 6
6 and an individual contact 68 and are short-circuited. Therefore, the coils 4 and 5 do not adversely affect medium wave reception characteristics.

The coil 21 included in the high frequency amplification circuit 51 and the coil 33 included in the local oscillation circuit 52 are
The inductance is changed in conjunction with the coils 3 and 4. By the switching operation of the switch 69, the switching diodes 13, 14, 1
7, 18, 24, 25, 26, 37, 38, 4
4 and 45 are changed, and the constants of the inductance element and capacitance element in the antenna circuit 60, high frequency amplification circuit 51, and local oscillation circuit 52 are changed.

In such prior art, the switches 61, 6
Since the switches 5 and 69 are operated in conjunction with each other, the installation space for such switches 61, 65, and 69 is large. Therefore, further miniaturization is desired.

An object of the present invention is to provide a receiver antenna circuit that can be miniaturized.

FIG. 2 shows an electric circuit of an embodiment of the present invention, and parts corresponding to those of the prior art shown in FIG. 1 are given the same reference numerals. Antenna circuit 90 according to the invention
is interposed between the antenna 1 and the high frequency amplification circuit 51. The high frequency signal amplified by the high frequency amplifier circuit 51 is mixed with the local oscillation signal from the oscillation circuit 52. The intermediate frequency signal thus obtained is amplified by an intermediate frequency amplification circuit 53. The high frequency amplification circuit 51, the local oscillation circuit 52, the intermediate frequency amplification circuit 53, and the detection circuit are integrated into the integrated circuit 5.
Contains 4. The signal from the intermediate frequency amplification circuit 53 is
The signal is demodulated by a detection circuit included in the integrated circuit 54, the demodulated signal is amplified by the amplifier circuit 56, and a tunable frequency signal is heard from the speaker 57. In this way, reception is performed in a superheterodyne manner.

When receiving in the long wave frequency band, the common contact 82 of the changeover switch 81 is electrically connected to the individual contact 83, and at this time, the common contact 70 of the switch 69 linked to the changeover switch 81 is connected to the individual contact 71.
It is electrically conductive. When receiving a medium wave frequency band, the common contact 82 of the changeover switch 81 is switched to the individual contact 84 and conductive, and at this time, the common contact 70 of the switch 69 is conductive to the individual contact 72.

In the antenna circuit 90, the high frequency signal from the antenna 1 is applied to the common contact 82 of the changeover switch 81 from the terminal of the first coil 3 on the side opposite to the antenna 1. One terminal of the coils 4 and 5 as the second coils is connected to the first individual contact 83.
A second individual contact 84 is connected to the capacitor 10 . A switching transistor 87 is connected between the other terminal of the coils 4 and 5 as the second coils and the capacitor 10. The base of switching transistor 87 connects via resistor 86 and diode 85 to individual contact 71 of switch 69.
connected to.

For long wave reception, when the common contact 82 of the changeover switch 81 conducts to the first individual contact 83, the common contact 70 of the switch 69 linked to the changeover switch 81 conducts to the individual contact 71, and therefore the antenna circuit In 60, diodes 85, 13,
14 and transistor 87 become conductive. Therefore, in the antenna circuit 90, tuning is performed by the first coil 3, the coils 4, 5 as the second coil, and the capacitors 8, 9, 10, 12.

In addition, for medium wave reception, selector switch 81
The common contact 82 of the switch 69 is electrically connected to the second individual contact 84, and at this time, the common contact 70 of the switch 69 is connected to the individual contact 7.
Conducts to 2. Therefore, diode 85 and switching transistor 87 are cut off. At this time, tuning is obtained by the coil 3 and capacitors 8, 9, and 10.

Depending on the switching operation of the switch 69, the switching diodes 13, 14, 17, 18, 24,
25, 26, 37, 38, 44, and 45 change, thereby changing the constant of at least one of the inductance element and the capacitance element included in the resonance circuit of the high frequency amplifier circuit 51 and the local oscillation circuit 52. is changed.

The switching transistor 87 has a collector
It is desirable that the saturation voltage between the emitters be low, thereby preventing the characteristics from deteriorating during broadcast reception.

A high frequency amplifier circuit 51 as another embodiment of the present invention
may be omitted. Furthermore, the present invention can be implemented in connection with a so-called double superheterodyne receiver, and can also be implemented in connection with other receivers.

As described above, according to the present invention, the unnecessary second coil during reception of the second frequency band is separated from the rest of the circuit by using a switching transistor. Compared to the prior art, the number of changeover switches has been reduced, which makes it possible to achieve a compact size.

[Brief explanation of the drawing]

FIG. 1 is an electrical circuit diagram of the prior art, and FIG. 2 is an electrical circuit diagram of an embodiment of the present invention. 1... Antenna, 3... First coil, 4, 5...
...Second coil, 8, 9, 10, 12...Capacitor, 13, 14, 17, 18, 24, 25, 2
6, 37, 38, 44, 45...Switching diode, 51...High frequency amplifier circuit, 52...Local oscillation circuit, 53...Intermediate frequency amplifier circuit, 81...
...Changing switch, 82...Common contact, 83...
First individual contact, 84... Second individual contact, 87...
Switching transistor, 69...Switch,
70... Common contact, 71, 72... Individual contact.

Claims (1)

[Claims for Utility Model Registration] (1) A method in which a signal in a first frequency band from an antenna is tuned by a first coil, a second coil connected in series with the first coil, and a capacitor. the first signal from that antenna.
In an antenna circuit of a receiver configured to receive a signal in a second frequency band higher than the frequency band in tune with a first coil and the capacitor, a common contact and first and second individual contacts are provided. a common contact is connected to a terminal of the first coil opposite to the antenna, a first individual contact is connected to one terminal of the second coil, and a second individual contact is connected to the capacitor. , a switching transistor is connected between the other terminal of the second coil and the capacitor,
An antenna circuit for a receiver, characterized in that a transistor is turned on when a common contact of a changeover switch conducts to a first individual contact, and the transistor is cut off when the common contact conducts to a second individual contact. (2) The receiver is of a superheterodyne type, and at least one of an inductance element and a capacitance element included in the resonant circuit of the local oscillation circuit is operated by a switching diode connected to a switch that operates in conjunction with the changeover switch. 2. The antenna circuit for a receiver according to claim 1, wherein a constant of is changed, and a base of said switching transistor is connected to said interlocking switch.