JPH0568143U - Radio transmission / reception switching circuit - Google Patents

Abstract

(57) [Abstract] [Purpose] An object of the present invention is to provide a mobile transceiver having a transceiver, and particularly to provide a transceiver that prevents the transmitter from continuing to output in an unloaded state when switching between transmission and reception. To do. In a wireless device having a transmission / reception function, a level detection circuit 5 that compares an output level from a transmission circuit 2 with a predetermined threshold value and outputs a detection signal when the output level is higher than the predetermined threshold value, and the detection An OR circuit 6 for controlling to connect the transmission / reception changeover switch 7 to the transmission side when any of the transmission changeover signals from the transmission switch 4 for inputting a signal and the transmission / reception changeover switch 7 of the antenna 8 is inputted. Composed of.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a mobile wireless device having a transmitter / receiver, and more particularly to a wireless transmitter / receiver which prevents the transmitting side from continuing output in an unloaded state when switching between transmitting and receiving.

[0002]

[Prior Art]

 FIG. 4 is a schematic block diagram of a conventional wireless transceiver. In the figure, 11 is a control circuit generally composed of a microcomputer, which controls the turning on and off of power to the transmitting circuit 12 and the receiving circuit 13. The transmission circuit 12 modulates the carrier frequency signal with the transmission signal (for example, AM, FM, etc.), power-amplifies the signal, and outputs the signal to the antenna 18. The receiving circuit 13 frequency-converts the signal received by the antenna 18 using an internal local oscillation signal and then performs predetermined demodulation. The transmission / reception switching switch 17 is for switching and connecting either the transmission circuit 12 or the reception circuit 13 to the antenna 18, and the low-pass filter 25 is for removing harmonic components of the transmission signal. is there.

When the transmission switch 14 is pushed down, the transmission switch 14 side of the resistor 18 to which the ground level (low level) has been applied becomes the power supply voltage (Vcc), that is, the high level, and the level becomes the input port of the microcomputer 11 and It is supplied to the current buffer circuit 22 of the inverter. The microcomputer 11 detects pressing of the transmission switch 14 through the input port and starts supplying power to the transmission circuit 12. As a result, the transmission circuit 12 becomes the active state and thereafter the transmission output state. At the same time, the buffer circuit 22 inverts the input level to turn on the PNP output transistor 23, and supplies a relay drive current to the transmission / reception changeover switch 17. The transmission / reception changeover switch 17 composed of an electromagnetic relay is switched to the transmission side (Tx) by causing the relay drive current to flow through the relay drive coil 24, and the output signal from the transmission circuit 12 in which the transmission is started is switched to the low pass filter 25. It is radiated from the antenna 18 via the.

When the transmission switch 14 is released after the above-described transmission is started, the microcomputer 11 detects it and stops the power supply to the transmission circuit 12, which is contrary to the above, and thereby the power supply from the transmission circuit 12 is stopped. Transmission output is stopped. Further, the buffer circuit 22 becomes high level and the transistor 23 is turned off to stop the relay drive current, whereby the transmission / reception changeover switch 17 is switched to the reception side (Rx) and the radio is in the reception state.

[0005]

[Problems to be solved by the device]

 However, in the conventional transmission / reception switching operation shown in FIG. 4, when switching from the transmission state to the reception / reception state, that is, when the transmission switch 14 is released from the pressed state, the microcomputer 11 detects it as described above. Thus, the power supply to the transmission circuit 12 is stopped, but at the same time, the transmission / reception changeover switch 17 is also switched to the reception side. In this case, the output from the transmission circuit 12 is still in the decaying process, that is, is being output, and the load of the transmission output consisting of a large amount of electric power is momentarily in a no-load state at the time of the switching, and the abrupt voltage change causes the transmission / reception. There was a problem that spark discharge was generated at the relay contact of the switching switch 17. This causes deterioration of the contacts, and at that time, there is a problem that the transmission output leaks to the receiving side and destroys or deteriorates the receiving circuit.

In view of the above problems, an object of the present invention is to add a simple transmission output level detection circuit to a conventional radio so that the transmission output is sufficiently attenuated when switching from transmission to reception as described above. It is intended to provide a wireless device in which the transmission / reception changeover switch 17 is switched to the receiving side after confirming the above.

[0007]

[Means for Solving the Problems]

 According to the present invention, as shown in FIG. 1, a transmission circuit 2 for modulating a carrier signal with a transmission signal and outputting it to an antenna 8 and a reception signal from an antenna 8 for demodulating with a local oscillation signal are used. A receiver circuit 3, a transmission / reception switch 7 for switching the connection between the antenna 8 and the transmitter circuit 2 or the receiver circuit 3, a transmission switch 4 for switching the transmission / reception switch 7 to the transmission side, and In a wireless transceiver comprising a control circuit 1 for controlling power supply to the transmission circuit 2 and the reception circuit 3 in response to a transmission switching signal from the transmission switch 4, the output level from the transmission circuit 2 is compared with a predetermined threshold value. A level detection circuit 5 that outputs a detection signal when the output level is higher than the predetermined threshold, and the detection signal and the transmission switch. Either transmitting switching signals from the 4 radio transceiver for chromatic an OR circuit 6 which controls to switch to the transmitting side the transmission-reception changeover switch 7 is provided as it is being entered.

[0008]

[Action]

 When the transmission switch 4 switches from transmission to reception, that is, when the transmission switch 4 is released from the pressed state, the control circuit 1 detects it and stops the power supply to the transmission circuit 2, Output disappears after a certain output decay time. The level detection circuit 5 rectifies the output signal from the transmission circuit 2 and compares it with a predetermined threshold level to output a signal corresponding to the presence or absence of the output of the transmission circuit 2. In the next OR circuit 6, the OR logic of the signal from the level detection circuit 5 and the signal from the transmission switch 4 is taken. When the transmission switch outputs an ON state (transmission state) or the level detection circuit determines that there is a transmission output, the OR circuit 6 outputs a signal for connecting the transmission / reception changeover switch 7 to the transmission side. ..

Therefore, even if the transmission switch 4 is released and the control circuit 1 detects it and stops the power supply to the transmission circuit 2, the transmission / reception changeover switch 7 is switched to the reception side at the same time. When the output from the transmission circuit 2 is sufficiently attenuated by the level detection circuit 5, that is, when the output reaches the threshold value or less, the output of the OR circuit 6 is switched to the reception side. This prevents the transmission output in the above-mentioned unloaded state.

[0010]

【Example】

 FIG. 2 illustrates an embodiment having the structure of a wireless device according to the present invention. 1, the microcomputer 11 includes the control circuit 1 of FIG. 1, the transmission circuit 12, the reception circuit 13, the transmission / reception changeover switch 17 and the antenna 18 of the transmission circuit 2, the reception circuit 3 and the transmission / reception changeover switch of FIG. 7 and antenna 8 respectively. Further, the buffer amplifier 19, the rectifier circuit 20, and the comparator 21 are the level detection circuit 5 of FIG. 1, the OR gate circuit 16, the current buffer circuit 22, and the current switch transistor 23 are the OR circuit 6 of FIG. The switches 14 correspond to the transmission switches 4 of FIG. 1, respectively. Also, in the figure, the same parts as those in FIG. 4 described in the conventional example are denoted by the same reference numerals, and those already described in the conventional example in FIG. 4 will not be described again here.

Next, the part of the present invention in FIG. 2 will be described in detail with reference to the operation waveform diagram of FIG. In FIG. 2, the output of the transmission circuit 12 is input to the buffer amplifier 19, and the output thereof is input to the rectification circuit 20 of the next stage. The rectifier circuit 20 rectifies the input signal by half-wave or full-wave and outputs a DC voltage corresponding to the transmission output level from the transmission circuit 12. The rectified output is compared with a predetermined threshold voltage (Vth) by the comparator 21 in the next stage, and when it is larger than the threshold voltage, the comparator 21 outputs a high level, and when it is smaller, it outputs a low level. To do. It should be noted that the threshold voltage is set to a value at which the output signal level is sufficiently low, that is, a small voltage corresponding to a no-signal state. Therefore, the high-level output indicates a state with a transmission signal, and the low-level signal indicates a transmission state. Shows no signal. The output of the comparator 21 is connected to one input terminal of the OR gate circuit 16, and the transmission ON / OFF signal of the transmission switch 14 is input to the other input terminal of the OR gate circuit 16. Therefore, when the transmission switch 14 is on or the output of the comparator 21 is high level (there is a transmission signal), the output of the OR gate circuit 16 becomes high level. The circuit after the output of the OR gate circuit 16 has been described in the conventional example (FIG. 4) and will not be described again here.

In FIG. 3, the operation according to the present invention described above is illustrated as a waveform diagram. In the figure, (a) shows the on / off state of the transmission switch 14, and the high level indicates on. This signal is detected by the input port of the microcomputer 11, which causes the microcomputer 11 to start supplying power to the transmission circuit 12. (B) of the figure shows the state, and the high level shows the power-on state. Note that the rise of the power supply on is slightly delayed with respect to (a) of the figure due to software processing of the microcomputer 11 ((b) of the figure).

In FIG. 3C, a state in which the transmission output rises to a predetermined level by supplying power to the transmission circuit 12 is illustrated. Further, it is also shown that the transmission output that has reached the predetermined level is attenuated after a predetermined time due to the power supply being turned off. This transmission signal is input to the rectifier circuit 20 via the buffer amplifier 19. In the diagram (d), the rectified output from the rectifier circuit 20 shown by the solid line and the threshold voltage (Vth) given to the comparator 21 at the next stage shown by the alternate long and short dash line are drawn. Therefore, the output of the comparator 21 becomes high level only while the rectified output is larger than the threshold voltage as shown in (e) of the figure, and the high level output of the comparator 21 is shown in (c) of the figure. It covers almost the entire signal waveform (with a transmission signal).

Therefore, the OR logic output of the OR gate circuit 16 which receives the signal of (a) in the figure and the signal of (e) in the figure is pushed by the transmission switch 14 as shown in (f) in the figure. The transmission / reception changeover switch 17 is immediately switched to the transmission side by the lower side, and thereafter, when the transmission switch 14 is released, the transmission / reception switching switch 17 is switched to the reception side after the transmission output becomes substantially zero. Therefore, there is no unloaded transmission condition, which has been a problem in the past.

[0015]

[Effect of the device]

 As described above, according to the present invention, when the transmission is started, the transmission / reception switching switch is immediately switched to the transmission side, and the transmission signal rises from a substantially no signal state. Deterioration of the relay contact of can be prevented. Further, according to the present invention, the transmission / reception changeover switch is switched to the reception side after the transmission signal is sufficiently attenuated even when the transmission state is switched to the reception state. Output of the load state is prevented, which prevents deterioration of the relay contacts due to spark discharge or the like. This extends the device life as a radio. Further, according to the present invention, transmission power is prevented from leaking to the receiving side at the same time by the simple circuit configuration, and it is possible to protect the receiving circuit or the like that receives weak power from the leakage signal.

[Brief description of drawings]

FIG. 1 is a block diagram showing a basic configuration of a wireless device according to the present invention.

FIG. 2 is a block diagram schematically showing an embodiment of a wireless device according to the present invention.

FIG. 3 is a diagram schematically showing operation waveforms according to the present invention of FIG.

FIG. 4 is a block diagram schematically showing a configuration example of a conventional wireless device.

[Explanation of symbols]

 1 ... Control circuit 2, 12 ... Transmission circuit 3, 13 ... Reception circuit 4, 14 ... Transmission switch 5 ... Level detection circuit 6 ... OR circuit 7, 17 ... Transmission / reception changeover switch 8, 18 ... Antenna 11 ... Microcomputer 16 ... OR Gate circuit 19 ... Amplifier 20 ... Rectifier circuit 21 ... Comparator 22 ... Buffer circuit 25 ... Low-pass filter

Claims (1)

[Scope of utility model registration request] 1. A transmission circuit (2) for modulating a carrier signal with a transmission signal and outputting it to an antenna (8), and a reception circuit for demodulating a reception signal from the antenna (8) using a local oscillation signal. (3), a transmission / reception changeover switch (7) for changing over the connection between the antenna (8) and the transmission circuit (2) or the reception circuit (3), and the transmission / reception changeover switch (7) to the transmission side. A transmission switch (4) for switching, and a control circuit (1) for controlling power supply to the transmission circuit (2) and the reception circuit (3) by a transmission switching signal from the transmission switch (4). In a wireless transceiver, a level detection circuit that compares the output level from the transmission circuit (2) with a predetermined threshold value and outputs a detection signal when the output level is higher than the predetermined threshold value. (5), and controls to switch the transmission-reception changeover switch (7) when any of the transmission switching signal from the detection signal and the transmit switch (4) is inputted to the transmitting side O
A wireless transceiver comprising an R circuit (6).