JPH0110025Y2 - - Google Patents

Description

[Detailed description of the invention] (a) Industrial application field The present invention relates to a radio receiver capable of receiving not only FM broadcast signals but also television broadcast signals.

(B) Prior Art Recently, some radio receivers with tape recorders have been designed to be able to receive television broadcast signals as well as FM broadcast signals. Figure 1 is a block diagram of a radio receiver that is most commonly used these days. Reference numerals 1 and 2 are first and second tuner circuits. The first tuner circuit 1 receives a television broadcast signal and converts the frequency. The circuit 2 receives the FM broadcast signal and converts the frequency. The intermediate frequency signal frequency-converted by the first tuner circuit 1 or the second tuner circuit 2 is sent to the intermediate frequency amplifier circuit 5 via switching diodes 3 and 4. After being applied to the audio circuit 6, the signal is converted into an audio signal, which is further amplified and used to drive a speaker or the like. By the way, it is necessary to selectively supply the power supply voltage to the first and second tuner circuits 1 and 2 and the intermediate frequency amplification circuit 5 to bring them into operation. Therefore, the power supply voltage is selectively supplied to the first tuner circuit 1 or the second tuner circuit 2 by the changeover switch 7,
The first tuner circuit 1 or the second tuner circuit 2
While putting one of them into operation, the first
When the tuner circuit 1 or the second tuner circuit 2 is in the operating state, the intermediate frequency amplifier circuit 5 must also be in the operating state, so the power supply voltage is also applied to the intermediate frequency amplifier circuit 5 via a changeover switch 8 different from the above. supplying. In this way, in addition to the switch 7 for supplying the power supply voltage to the first tuner circuit 1 or the second tuner circuit 2, the changeover switch 8 for supplying the power supply voltage to the intermediate frequency amplification circuit 5 is also required. By using the switching diodes 3 and 4 to apply the intermediate frequency signal from the first tuner circuit 1 or the second tuner circuit 2 to the intermediate frequency amplifier circuit 5, the effect is halved even if a changeover switch is not required.

(c) Purpose of the invention The present invention uses a switching diode used to selectively add an intermediate frequency signal from the first tuner circuit or the second tuner circuit.
The present invention provides a radio receiver that eliminates the need for a changeover switch for applying power supply voltage to the intermediate frequency amplification circuit by supplying the power supply voltage to the intermediate frequency amplification circuit.

(d) Structure of the invention The invention provides first and second tuner circuits that receive broadcast signals in different frequency ranges and perform frequency conversion, and switches intermediate frequency signals obtained from the first and second tuner circuits. Supplying the power supply voltage to the intermediate frequency amplification circuit through the diode, and also applying the power supply voltage applied to the first tuner circuit or the second tuner circuit by the switching diode to the intermediate frequency amplification circuit through the switching diode. The present invention relates to a radio receiver characterized by:

(E) Example Figures 2 and 3 about the radio receiver of the present invention.
This will be explained according to the diagram. Reference numeral 10 denotes a first tuner circuit for receiving a television broadcast signal, which includes an antenna 11, a high frequency amplifier for amplifying the broadcast signal received by the antenna 11, and a local oscillation generated by the broadcast signal amplified by the high frequency amplifier and a local oscillator. It has a mixer that mixes the signals and forms an intermediate frequency signal. 12
is the second tuner circuit that receives the FM broadcast signal,
Although the frequency range to be processed is different from that of the first tuner circuit 10, the circuit configuration is the same, and the antenna 13,
It has a high frequency amplifier that amplifies the broadcast signal from the antenna 13, and a mixer that mixes the broadcast signal amplified by the high frequency amplifier and a local oscillation signal from a local oscillator to form an intermediate frequency signal. Said first
The frequency of the intermediate frequency signal taken out from the tuner circuit 10 is made to be the same as the frequency of the intermediate frequency signal taken out from the second tuner circuit 12. 14 is an intermediate frequency amplifier circuit, which includes switching diodes 15 and 16, and a coupling capacitor 1.
7, the first and second tuner circuits 10, 1
Connected to 2. 18 is a resistor for supplying a power supply voltage to the intermediate frequency amplification circuit 14 via the switching diodes 15 and 16.
19 is a decoupling capacitor, and 20 is an audio circuit, which includes a detector that detects the intermediate frequency signal amplified by the intermediate frequency amplifier circuit 14 and converts it into an audio signal, and an amplifier that amplifies the detected audio signal.
The amplifier of the audio circuit 20 is also used when receiving AM broadcast signals. Reference numeral 21 denotes a changeover switch for selectively supplying power supply voltage to the first tuner circuit 10 or the second tuner circuit 12. FIG. 3 shows some specific circuits of the first and second tuner circuits 10 and 12 and the intermediate frequency amplification circuit 14. Transformers 22 and 23 are connected, and the primary winding 2 of the intermediate frequency transformers 22 and 23
In order to supply the power supply voltage applied to the intermediate frequency transformers 22, 23 to the secondary windings 26, 27 of the intermediate frequency transformers 22, 23, the lead wires 28, 29 connect the primary windings 24, 25 and the secondary windings 24, 25. The side windings 26 and 27 are DC-coupled. 30 is an amplification transistor, 31
is a ceramic filter.

The radio receiver of the present invention has the configuration described above. If one wishes to listen to a television broadcast signal now, the contact piece of the changeover switch 21 is positioned at the uppermost contact point. Then, the power supply voltage becomes the audio circuit 20
is supplied to the first tuner circuit 10 via the changeover switch 21, and is supplied to the first tuner circuit 10 via the changeover switch 21.
The power supply voltage supplied to the tuner circuit 10 is further supplied to the intermediate frequency amplifier circuit 14 through the lead wire 28, the secondary winding 26 of the intermediate frequency transformer 22, the diode 15, and the resistor 18. Therefore, the first
Since the tuner circuit 10, the intermediate frequency amplification circuit 14, and the audio amplification circuit 20 are activated, the broadcast signal tuned to the tuning frequency of the high frequency amplifier among the television broadcast signals received by the antenna 11 is received and amplified. After that, it is mixed with a local oscillation signal in a mixer and converted into an intermediate frequency signal. The intermediate frequency signal is supplied to an intermediate frequency amplification circuit 14 through a switching diode 15. A smoothing circuit 32 consisting of a resistor 18 and a capacitor 19 is connected to the collector of the amplification transistor 30 of the intermediate frequency amplification circuit 4.
Since the power supply voltage is supplied through the switching diode 15, the intermediate frequency signal applied to the base is amplified, filtered by the ceramic filter 31, and then applied to the audio circuit 20. After being detected and amplified by 20,
is supplied to the speakers 32 and 33, and the speaker 3
2 and 33, the received broadcast signal can be listened to. If you want to listen to a different broadcast signal than the one you are currently receiving, change the tuning frequency of the high-frequency amplifier circuit of the first tuner circuit 10 by operating the channel selection button, etc., and a different TV broadcast signal will be received. be done. By the way, the power supply voltage supplied to the first tuner circuit 10 is connected to the intermediate frequency amplifier circuit 1 via the switching diode 15.
However, since the switching diode 16 is in the opposite direction in the second tuner circuit 12,
Since the power supply voltage is not applied and the switching diode 15 is forward biased, the intermediate frequency signal output from the first tuner circuit 10 is applied to the intermediate frequency amplifier circuit 14 with little loss.

Next, when you want to listen to the FM broadcast signal, switch the contact of the changeover switch 21 to the middle contact, and the power supply voltage is transferred from the second tuner circuit 12 to the intermediate frequency amplification circuit 14 via the switching diode 16. This year, the second tuner circuit 12, intermediate frequency amplification circuit 14, and audio circuit 20 will be activated, so the FM broadcast signal received by the antenna 13 will be amplified and frequency-converted by the second tuner circuit 12. The obtained intermediate frequency signal is applied to the intermediate frequency amplifier circuit 14 via the switching diode 16 and amplified, and then applied to the audio circuit 20 where it is detected and further amplified to drive the speakers 32 and 33, so that the FM broadcasting is performed. Signals can be heard.

(f) Effects of the invention As mentioned above, the radio receiver of the invention receives broadcast signals in different frequency ranges, converts each intermediate frequency signal obtained from the first and second tuner circuits that perform frequency conversion into a common intermediate frequency To add it to the amplifier circuit,
A switching diode is used to eliminate mutual influence, and since the switching diode is used to apply the power supply voltage applied to the first and second tuner circuits to the intermediate frequency amplification circuit, it is difficult to use the conventional intermediate frequency amplification circuit. The transfer switch required to apply selective power supply voltages to the circuit can be eliminated.

[Brief explanation of drawings]

Fig. 1 is a block diagram of a conventional radio receiver, Fig. 2 is a block diagram of a radio receiver of the present invention, and Fig. 3 is a block diagram of a conventional radio receiver.
The figure is a circuit diagram of the main parts of the radio receiver of the present invention. 10...First tuner circuit, 12...Second tuner circuit, 14...Intermediate frequency amplification circuit, 15,1
6...Switching diode, 20...Audio circuit.

Claims (1)

[Scope of utility model registration request] a first tuner circuit that receives a broadcast signal in a first frequency range and performs frequency conversion; a second tuner circuit that receives a broadcast signal in a second frequency range and performs frequency conversion; A primary winding connected to the output side of the tuner circuit, a secondary winding electromagnetically coupled to the primary winding, and a lead wire for DC coupling the primary winding and the secondary winding. a switching diode having one electrode connected to the secondary winding of the first and second intermediate frequency transformers and the other electrode coupled to each other; an intermediate frequency amplifier circuit connected to the other coupled electrode of the switching diode via a coupling capacitor, and having a power terminal connected to the other electrode of the switching diode via a resistor; and a first tuner circuit or a second tuner circuit. The intermediate frequency signal obtained by frequency conversion in the first tuner circuit or the second tuner circuit is transmitted to the intermediate frequency amplifier circuit via an intermediate frequency transformer and a coupling capacitor. A radio receiver characterized in that the power supply voltage supplied to the first tuner circuit or the second tuner circuit is further supplied to the intermediate frequency amplification circuit via the lead wire, the switching diode, and the resistor.