JPH0250656B2 - - Google Patents

Description

TECHNICAL FIELD The present invention relates to a wireless communication device, and more particularly to a circuit configuration that reliably and quickly switches between transmission and reception.

BACKGROUND ART A radio communication device is generally switched between reception and transmission by turning on and off a press talk switch, and this switching is usually performed by switching the power supply. However, if the receiver and transmitter start up at the same time, problems such as noise will occur, so in order to prevent them from being supplied with power at the same time, a predetermined condition is set in which power is not supplied to both when switching the power supply. It is necessary to set aside time.

Problems to be Solved by the Invention However, if this time is long, a problem arises in that the first part of the call is not transmitted, especially when switching from the receiving state to the transmitting state.

Means for Solving the Problem The present invention provides a wireless communication device that energizes either a receiver or a transmitter depending on whether a pre-talk switch is turned on or off, in which control signals with different output voltages are generated depending on whether the pre-talk switch is turned on or off. a changeover switch for selectively supplying a power supply voltage to the receiver and the transmitter; a first control switch that controls the changeover switch from a state in which power supply voltage is supplied to both switches to a state in which power supply voltage is not supplied to both switches;
and a third discrimination means; and a fourth level discrimination means for controlling the changeover switch so that the power supply voltage is supplied to the receiver when the supply voltage to the transmitter falls below a predetermined level; The wireless communication device includes a diode connected in a forward direction between a switch and the receiver.

Effect According to the present invention, power supply to the receiver is started when the supply voltage to the transmitter decreases, and power supply to the transmitter is started when the supply voltage to the receiver decreases. Fast switching because the receiver and transmitter are never activated at the same time, and the diode allows detection of a drop in the supply voltage to the receiver without being affected by the equivalent capacitance of the receiver power circuit. will be held.

Embodiment FIG. 1 is a block diagram of one embodiment of the present invention. This wireless communication device basically consists of a receiver 1.
, a transmitter 2 , and a power supply circuit 3 . The antenna 4 is selectively connected to the receiver 1 or the transmitter 2 by a changeover switch 5. A high frequency signal from the antenna 4 via the switch 5 is amplified by the high frequency amplification circuit 6 in the receiver 1.
The first mixing circuit 7 mixes the signal with the local oscillation signal from the first local oscillation circuit 8 . The intermediate frequency signal from the first mixing circuit 7 is amplified in the intermediate frequency amplifying circuit 9 and provided to the second mixing circuit 10. A local oscillation signal from a second local oscillation circuit 11 is applied to the second mixing circuit 10 . The output from this second mixing circuit 10 is amplified in a second intermediate frequency amplification circuit 12. In this way, reception is performed using the double superheterodyne system. The output from the second intermediate frequency amplification circuit 12 is applied to a frequency discrimination circuit 14 via a limiter 13 and demodulated. From the frequency discrimination circuit 14, the received acoustic signal is led out to a line 15. The signal from this line 15 is amplified in a low frequency amplification circuit 16, and a speaker 17 is driven.

In this receiver 1, a squelch circuit 18 is provided. This squelch circuit 18
Noise amplification circuit 1 that amplifies only signals in a relatively high range of about 25kHz to 30kHz among the signals from
9, rectifying diodes 20 and 21, and a smoothing capacitor 22 for smoothing the signal rectified by the rectifying diodes 20 and 21, and the output voltage of this smoothing capacitor 22 is transmitted from a line 23 to a noise control circuit 24. Given. When the voltage on line 23 is below a predetermined discrimination level l, noise control circuit 24 activates low frequency amplification circuit 16;
As a result, the speaker 17 is given an audio signal. When the voltage on the line 23 is above the discrimination level 1, the noise control circuit 24 disables the low frequency amplification circuit 16 and stops the low frequency amplification function.

In the transmitter 2, the audio signal from the microphone 25 is amplified by the amplifier circuit 26, and the audio signal is amplified by the modulation circuit 2.
7 is given. The modulation circuit 27 includes an oscillation circuit 28
A high frequency signal is given from The modulation circuit 27 frequency-modulates the high-frequency signal using the audio signal from the amplifier circuit 26, and supplies it to the multiplier circuit 29 to be multiplied. The output from the multiplier circuit 29 is amplified by a power amplification circuit 30 and applied to the antenna 4 from the changeover switch 5.

In the power supply circuit 3, a power supply 31 such as a battery
The output voltage is stabilized by a stabilizing circuit 32 and is applied to a protection circuit 34 from a line 33. The protection circuit 34 includes a changeover switch 35
has. The changeover switch 35 has a common contact 36 connected to the line 33 and individual contacts 37 and 38.
has. A control signal from line 39 is provided to a first level discrimination circuit 40. This first discrimination circuit 40 conducts the common contact 36 of the changeover switch 35 to the individual contact 37 when the control signal on the line 39 is higher than the first discrimination level l1, and when the control signal 39 is lower than the discrimination level l1. At this time, the common contact 36 is cut off from the individual contacts 37 and 38. Second
The discrimination level 41 switches the common contact 36 to the individual contact 38 and makes it conductive when the voltage of the individual contact 37 decreases and becomes less than the second discrimination level l2.
A control signal from line 39 is also provided to third level discrimination circuit 42. Third level discrimination circuit 4
2, the control signal on line 39 is at the third discrimination level l
When the number is 3 or more, the common contact 36 is changed to the individual contact 3.
8 and 37, and when the control signal 39 is lower than the discrimination level l3, the common contact 36 is disconnected from the individual contact 3.
8 remains conductive. 4th level discrimination circuit 4
3, the voltage of the individual contact 38 is at the fourth discrimination level L4
When it becomes less than
Make it conductive.

Individual contact 37 connects line 44 to diode 4
5 to the receiver 1, thereby energizing the receiver 1. The equivalent capacitance on the input side of the receiver 1 seen from the diode 45 side is indicated by reference numeral 46. Individual contact 38 is connected to line 4
7 to the transmitter 2.

Line 39 connects to press talk switch 48,
It is connected to a connection point 50 with the resistor 49. The press talk switch 48 is not pressed during reception;
Therefore, line 3 is blocked.
The control signal 9 is at high level. When transmitting, the press talk switch 48 is pressed, thereby causing the control signal on the line 39 to go low. The changeover switch 5 performs a switching operation by operating the pre-talk switch 48 so that the signal from the antenna 4 is applied to the receiver 1 during reception, and the signal from the transmitter 2 is applied to the antenna 4 during transmission.

Line 47 connects line 51 to diode 52
is connected to line 23 via.

During reception, the pre-talk switch 48 is not pressed, so the pre-talk switch 48 is cut off. The control signal on line 39 is as shown in FIG. 2 and remains high before time t1. Therefore, by the action of the first level discrimination circuit 40, the common contact 36 of the changeover switch 35 is electrically connected to the individual contact 37, and the receiver 1 is energized to perform reception.

When switching from reception to transmission and performing transmission using the simplex system, the pre-talk switch 48 is pressed at time t1 to make it conductive. As a result, the control signal on line 39 becomes less than the first discrimination level l1 at time t2. Therefore, the common contact 36 of the changeover switch 35 separates from the individual contact 37 after time t2. The change in voltage on the line 53 on the cathode side of the diode 45 decreases over time after time t2 due to the action of the equivalent capacitance 46, as shown in FIG. 2. The voltage of the individual contacts 37 and therefore of the line 44 drops sharply after time t2, as shown in FIG. At time t3 when the voltage of this line 44 becomes less than the second discrimination level l2, the second level discrimination circuit 41 connects the common contact 36 of the changeover switch 35 to the individual contact 38. Therefore, after time t3, the voltage shown in FIG. 2 and 4 is applied to line 47 in an increased manner. After time t4, normal voltage is applied to the transmitting circuit 2 and transmission becomes possible. In this way, the time W1 between times t1 and t4 is shortened by the action of the diode 45, and actually becomes, for example, 2 to 5 mmsec. Therefore, the switching operation from reception to transmission can be performed quickly, and communication can be performed smoothly.

When switching from transmission to reception, time t
At step 5, release the press talk switch 48 to shut it off. As a result, the control signal on line 39 increases after time t5. When the control signal becomes equal to or higher than the third discrimination level l3 at time t5a, the third level discrimination circuit 42 disconnects the common contact 36 of the changeover switch 35 from the individual contacts 38. Therefore, the voltage on line 47 decreases.
When the voltage on the line 47 decreases and reaches the fourth discrimination level l4 at time t6 and becomes lower than it, the fourth level discrimination circuit 43 conducts the common contact 36 to the individual contact 37 at time t6. This allows power to be supplied to the receiver 1 from line 53 via line 44 and diode 45. The functions of the second level discrimination circuit 41 and the fourth level discrimination circuit 43 reliably prevent the receiver 1 and the transmitter 2 from being energized at the same time.

If diode 45 is omitted and lines 44 and 53 are connected directly,
As shown in FIG. 4, from time t2 onwards when the control signal on line 39 becomes less than the first discrimination level l1 as shown in FIG. The time W1a at the time t3 when the discrimination level decreases and becomes less than the discrimination level l2 becomes extremely long. Figure 4 2 is line 4
4.3 shows the voltage waveform of line 4.
7 is shown. When the diode 45 is omitted, the time W1a is long, and the time W2 required for switching from reception to transmission is correspondingly long. This time W2 is, for example, about 50 mmsec, and communication cannot be performed smoothly. Diode 45 helps solve this problem.

In order to explain the operation of the squelch circuit 18, the third
Referring to the figure, the press talk switch 48 is pressed at time t11 as shown in FIG. 31. This causes a switching operation from reception to transmission. Due to the pressing operation of the press talk switch 48, the voltage of the line 53 decreases after time t11 as shown in FIG. 3. The low frequency amplification circuit 16 of this receiver 1 achieves a low frequency amplification function when the voltage on the line 53 is equal to or greater than the value l11, and cannot perform the low frequency amplification function when the voltage on the line 53 is less than the value l11. Time t12 before the voltage on line 53 drops to value l11
, the voltage on line 47 increases. When the voltage on the line 53 is equal to or higher than the value l11, the receiver 1 can perform the receiving operation as shown in FIG. Transmission operation becomes possible after t14.

As shown in FIG. 3, the voltage of the line 23 decreases after time t11, and
2, the smoothing capacitor 22 is charged by the voltage from the line 51 via the diode 52 after time t12 when the common contact 36 of the changeover switch 35 becomes conductive to the individual contact 38. In this way, the voltage V1 on line 23 of smoothing capacitor 22 is greater than or equal to a value that allows noise control circuit 24 to keep low frequency amplifier circuit 16 disabled. Therefore, no noise is generated from the low frequency amplifier circuit 16 to the speaker 17 as shown in FIG. 36.

If line 51 and diode 52 are omitted, press talk switch 48
is pressed at time t11 as shown in FIG. 51, the voltage of line 23 decreases as shown in FIG. 53, and the voltage of line 47 decreases as shown in FIG. 54 at time t12. It increases thereafter. As shown in FIG. 5, the voltage on the line 23 drops immediately after time t11, and therefore, before time t13 when the low frequency amplification circuit 16 can achieve the low frequency amplification function, the noise control circuit 24 The operation of the low frequency amplifier circuit 16 is allowed. Therefore, as shown in FIG.
Noise will be generated. Figure 5 2
The operating states of receiver 1 and transmitter 2 are shown in FIG. When line 51 and diode 52 are omitted in this manner, noise will be generated when switching from receive to transmit due to operation of pre-talk switch 48. The present invention solves this problem.

By connecting a capacitor 54 in parallel to the line 44, the time t2 to t shown in FIG.
3 times can be changed.

Effects As described above, according to the present invention, switching from reception to transmission can be performed reliably and quickly.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of one embodiment of the present invention, and FIG.
The figure is a waveform diagram for explaining the operation of the power supply circuit 3.
3 is a waveform diagram for explaining the operation of the squelch circuit 18, FIG. 4 is a waveform diagram for explaining the operation when the diode 45 is not provided in the power supply circuit 3, and FIG. 5 is a waveform diagram for explaining the operation of the squelch circuit 18. FIG. 4 is a waveform diagram for explaining the operation when the line 51 and the diode 52 are not provided. 1... Receiver, 2... Transmitter, 3... Power supply circuit, 5... Changeover switch, 14... Frequency discrimination circuit, 16... Low frequency amplification circuit, 17... Speaker, 19... Noise amplification circuit , 20, 21, 52
... Diode, 22 ... Smoothing capacitor, 24
... Noise control circuit, 32 ... Stability circuit, 34 ...
...switch circuit, 35...changeover switch.

Claims (1)

[Scope of Claims] 1. A wireless communication device that energizes one of a receiver and a transmitter according to whether a pre-talk switch is turned on or off, comprising: means for generating a control signal having a different output voltage depending on whether the pre-talk switch is turned on or off; , a changeover switch that selectively supplies a power supply voltage to the receiver and the transmitter; and a state in which the power supply voltage is supplied to one of the receiver and the transmitter according to the voltage of the control signal; A first control switch that controls the changeover switch so that power supply voltage is not supplied to both switches.
and third discriminating means; second level discriminating means for controlling the changeover switch so that power supply voltage is supplied to the transmitter when the voltage supplied to the receiver falls below a predetermined level; and the transmitter. a fourth level discriminator for controlling the changeover switch so that power supply voltage is supplied to the receiver when the supply voltage to the receiver falls below a predetermined level; and between the changeover switch and the receiver; A wireless communication device comprising: a forward-connected diode.