JPS60160225A - Fm radio set with transmission function - Google Patents

Abstract

PURPOSE:To decrease number of components and to attain miniaturization by having only to switch a power supply so as to switch transmission and reception and also use components for transmission/reception in common. CONSTITUTION:In throwing a switch 7 to the position T, the position T, the transmission state is obtained. A voltage is applied to a base of a transistor (TR) 13 for an output buffer amplifier and an oscillating circuit 12 and a battery voltage is applied to a collector of the TR13 via a filter 8. Then an output oscillated and amplified appears the collector of the TR13 and a high frequency signal is transmitted from an antenna 1. Moreover, a diode 11 is interrupted completely and it is possible to disconnect an antenna 1 from a reception circuit 5. In throwing the switch 7 to the R position, the reception state is obtained. A voltage is applied to the reception circuit in this case and the power supply of the transmission circuit is disconnected. Then the diode 11 is conducted and the antenna 1 is connected to the reception circuit 5 via the filter 8. Furthermore, the power supply of the transmission circuit 4 is interrupted, and the TR13 is cut off and reaches the high impedance state, which does not give any effect onto the reception circuit.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a circuit for a compact and inexpensive IFM radio with wireless microphone.

Conventionally, as shown in FIG. 1, the transmission and reception of a 7M radio with a wireless microphone was switched by switching the antenna 1 shared by the transmitting circuit 4 and the receiving circuit 5 with the switch 2, and at the same time switching the power supply with the switch 8.

In this way, multiple interlocking circuit changeover switches were required. However, multi-circuit changeover switches have the disadvantage of being large in size and driving force, making them difficult to implement in small devices. In addition, the high frequency signal must be routed to the changeover switch, which tends to cause performance deterioration.

° In order to eliminate the above-mentioned drawbacks, the present invention provides a circuit for an FM receiver with a transmitting function, which can switch between transmitting and receiving simply by switching the power supply, and is ideal for downsizing with a small number of parts by using parts that can be used for both transmitting and receiving. The purpose is to realize the following.

Hereinafter, the present invention will be explained in detail based on the drawings.

FIG. 2 is a diagram showing the principle of the present invention, in which 1 is an antenna;
4 is a transmitting circuit, 5 is a receiving circuit, 6 is an antenna switching circuit controlled by a switch 7, and 7 is a transmitting/receiving switching switch for switching the power sources of the transmitter and the receiver. 8 is a filter. Figure 2 shows the simplest circuit example, but if the input or output terminal 1 and the common terminal (ground terminal) 2 are DC-conducting, another circuit can be used. I can do it. In order to obtain excellent effects, a filter with bandpass characteristics between terminals 1 and 8 is preferable.

At least during reception, the bias circuit 9 has a voltage lower than that of the battery IO and a forward voltage drop of 0.7 V of the diode 11.
Higher voltage.

When the switch 7 is set as shown, the transmitting state is entered.

At this time, a voltage is applied to the oscillation circuit 12 and the output buffer amplifier transistor 13, and a voltage of 4 is applied to the collector of the transistor 13 via the filter 8. Then, the amplified oscillation output appears at the collector of the transistor 13, and a high frequency wave is transmitted from the antenna 1 via the filter 8. The cathode potential of the diode 11 is the voltage of the battery 10 plus a high frequency voltage (1 to 2 V in PP value), and when transmitting the voltage of the bias circuit 9, the voltage of the bias circuit 9 is set lower than that of the battery 10 (-f) I7 or more. So,
Diode 11 is completely cut off, and antenna 1
It is possible to disconnect it from the t-receiver circuit 5.

When the switch 7 is placed in a state opposite to that shown in the figure, it becomes a receiving state. At this time, a voltage is applied to the receiving circuit, and the power to the transmitting circuit is turned off. Then, the cathode voltage of the diode 110 is connected to the ground via the filter 8 and the impedance of the transmitting circuit, and therefore becomes a low voltage. On the other hand, the anode of the diode 11 is supplied with a voltage higher than the forward drop voltage (approximately 0.71) of the diode from the bias circuit 9 via a resistor. Therefore, the diode 11 becomes conductive and the antenna 1 is connected to the receiving circuit 5 via the filter 8.

Also, the power to the transmitting circuit 4 is turned off, and the transistor 13 is turned off.
is in the cut-off state, so it becomes an impedance and has no effect on the receiving circuit. As described above, it is possible to switch the transmitting and receiving antennas simply by switching the power supply.

FIG. 8 shows another embodiment for realizing the filter 8 of FIG. 2, in which terminals (1) and (2) are replaced and connected, respectively. Filter 8 will work if there is direct current continuity between terminals ■ and terminal ■, but it removes unnecessary high frequencies during reception, improves selectivity and variation 1la1%, and suppresses spurious during transmission. Therefore, it is preferable to use a bandpass filter as the filter. SR8 diagram OA, B, C, D
, E and the 5% line side both have good characteristics.

The present invention also includes the use of a filter that combines a choke coil that passes direct current and a bandpass filter other than that shown in FIG. 8.

FIG. 4 shows a practical circuit of a 7M radio with a transmission function to which the present invention is applied. 6 is a receiving circuit which amplifies, frequency converts, intermediate frequency amplifies, and detects the high frequency signal input to A to obtain a demodulated signal.

The demodulated signal is amplified at 7:15, and the earphone 16 is sounded. Since it is connected to the jack of the earphone 16 via two yoke coils, it is in a floating state in terms of high frequency. High frequencies picked up by the cord of the earphone 16 are input to the filter 8 via the jack. The filter 8 is a bidirectional type in which the terminals ■ and ■ can be used for input and output, and has bandpass characteristics. During reception, the switch 7 is connected in a direction different from that shown. At this time, the terminal (2) of the filter 8 is connected to the ground potential via an impedance. The cathode side of the diode 11 has a low voltage. On the other hand, the divided voltage of the bias circuit 9 is applied to the anode side of the diode, and a forward current flows through the diode 11, making it conductive.

On the other hand, the base voltage of the transistor 13 is the ground potential, and the transistor 13 is in a cut-off state. As a result, the signal picked up by the antenna or the cord of the earphone 16 is input to the receiving circuit 6. When transmitting, switch 7 is set as shown.

At this time, the terminal (2) of the filter 8 becomes the battery voltage, and the voltage is supplied to the collector of the transistor 13. On the other hand, the output of the bias circuit 9 becomes the ground potential. As a result, the diode 11 becomes reverse biased and becomes an L or OFF state.

The transistor 14 oscillates as a Colpitts oscillation circuit, and the output is cascade amplified by the transistor 13, harmonics are removed by the filter 8, and transmitted from the code of the Iophone 16, which is an antenna.

The 17#'i condenser microphone is used for frequency modulation.

In the manner described above, switching between transmission and reception is performed simply by switching the power supply.

FIG. 5 shows another embodiment of the transmitting circuit 4, and "
AJIrB" can be replaced by connecting them to each other.

As described above, the present invention has the following effects.

(1) Since the number of switch circuits can be reduced, the size can be reduced.

(2) Since harmonic signals are not routed to the switch, loss due to wiring and performance deterioration due to coupling with other signals can be prevented.

(8) The antenna, antenna coupling circuit, and bandpass filter can be used for both transmission and reception.

[Brief explanation of the drawing]

FIG. 1 shows a transmission/reception switching system of a conventional radio with a transmission function, FIG. 2 shows an embodiment for explaining the present invention in detail, and FIGS. 8A to 8E show other embodiments of the filter 8. For example,
FIG. 4 shows a practical circuit of an FM radio with a transmitting function to which the present invention is applied, and FIG. 5 shows another embodiment of the transmitting circuit 4. 1. Battle antenna 2, 8... Switch 4. Fist transmitting circuit 5.6. Spring receiving circuit 7... Switch 8 (for switching between transmitting and receiving). Fist filter 9. 1 Bias circuit 11... Diode 16... Earphone 17 Day condenser microphone Fig. 1 Fig. 2 Fig. 3 A Fig. 3 B

Claims (1)

[Claims] In an FM radio receiver with a transmission function, which includes a 7M radio reception circuit, a transmission circuit for a wireless microphone, and an antenna used for both transmission and reception, the FM radio receiver is inserted between the front end of the 7M radio reception circuit and the antenna, and A filter in which at least one of the input/output terminals and a common ground terminal are electrically connected, an oscillation circuit for a wireless microphone, an output of the oscillation circuit is buffered and amplified, and an output terminal of a transistor is directly connected to the filter. The antenna switching circuit includes an output transistor, a diode inserted between the filter and the front end, and a bias circuit that applies voltage to the diode. When the output transistor of the transmitter circuit is in a cut-off state,
And the diode becomes conductive, connecting the antenna to the receiving circuit, and at the time of transmission, the diode becomes reverse biased, disconnecting the antenna from the receiving circuit, and at the same time, the output transistor of the transmitting circuit operates to connect the antenna to the transmitting circuit. 7 with a transmitting function that has an antenna switching circuit characterized by
M radio.