JP2920574B2 - A radio that can be detachably connected to a pluggable antenna - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radio device to which a pluggable antenna can be detachably connected.

[0002]

2. Description of the Related Art In a radio device to be used while moving, an antenna is rarely kept connected to the radio at all times, and an antenna is connected only during operation in many cases. A plurality of antennas are often used depending on the frequency band and the antenna gain depending on the situation of the destination. For this reason, a plurality of antenna plugs are provided in the radio, and these are switched and used.

FIG. 3 shows an example of an antenna switching circuit in a conventional radio, in which 1 is a transmission output line for outputting a high-frequency signal from the radio to the antenna, and 2 is provided with two fixed contacts a and b. Antenna changeover switches, 3, 4 are antenna connection connection plugs, 5, 6 are antennae, 7 is antenna changeover switch 2.
Is a control line for outputting a switching signal for controlling the antenna. In FIG. 3, since the movable contact of the antenna changeover switch 2 is on the contact a side, the antenna A is connected to the plug 3 and the antenna A is selected. Therefore, a high-frequency signal from the radio is output from the antenna A. A switching signal for controlling the antenna changeover switch 2 is output to the control line 7 by operating a manual selection switch generally provided in the antenna changeover device.

[0004]

By the way, as shown in FIG. 3, when only the antenna A is connected to the radio, an erroneous operation of the selection switch causes the movable contact of the antenna changeover switch 2 to move to the fixed contact b side. Assuming that the switching is made to the above, since the antenna 4 is not connected to the plug 4 on the side of the fixed contact b, the wireless device performs transmission without load, and the transmission unit may be damaged. is there. A similar problem occurs when no antenna is connected to any of the plugs 3 and 4. However, when the antenna is switched manually, the above-described malfunction cannot be prevented, and no protection against unconnected antenna has been taken.

SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a wireless device which prevents the above-mentioned malfunction and protects the wireless device when the antenna is not connected.

[0006]

According to the present invention, an antenna, such as a high-frequency coil or a resistor, for generating a DC conduction between the antenna and the ground is connected to the antenna connected to the antenna plug. Current detection means for applying a DC voltage to each of the antenna plugs to detect whether or not a DC current flows, and, based on the current detection, judging the presence or absence of connection of the antenna to a plurality of antenna plugs, and switching the antenna. The above object is achieved by providing a transmission control circuit including a signal output unit that outputs a control signal to a switch and outputs a transmission prohibition signal that prohibits transmission when an antenna is not connected.

[0007]

As described above, if an element having a high impedance to a high-frequency signal and capable of passing only direct current is connected between the antenna and the ground, only the plug to which the antenna is connected has direct current. Since the current flows, it is possible to determine whether or not the antenna is connected.

[0008]

FIG. 1 shows an antenna switching circuit of a radio apparatus according to an embodiment of the present invention, and the same reference numerals are given to the same parts as in FIG. In FIG. 1, a high-frequency coil 8 is connected to the antenna 5.
Is connected to the ground, and the antenna 6 is shown in a state in which the resistor 9 is connected to the ground. However, the antenna is generally provided with a matching circuit for performing impedance matching with the radio. In such a case, there is no need to connect an additional element, as in the case of the antenna 5, which is short-circuited to the ground by the high-frequency coil 8. However, without such a matching circuit,
If the antenna is not conducted to the ground, an appropriate resistor 9 or a high-frequency choke which does not affect the characteristics of the antenna may be connected like the antenna 6.

On the other hand, a transmission control circuit 10 having a current detection circuit 11 and a signal output circuit 12 is provided on the side of the radio, and the current detection circuit 11 includes the antenna plug 3,
4 is applied with a DC voltage to detect whether a DC current flows. In this case, a direct current flows since the antenna 5 is connected to the plug 3, but no current flows because the antenna 6 is not connected to the plug 4. Therefore, the transmission control circuit 10 determines that the antenna is connected only to the plug 3 and automatically switches the antenna changeover switch 2 to the fixed contact a from the signal output circuit 12 to the switch control line 7. A signal is output and the antenna A is selected. The capacitors 13 and 14 shown in FIG. 1 are provided to prevent a DC voltage applied from the current detection circuit 11 to the plugs 3 and 4 from flowing to the wireless device. In other words, a capacitance value that can ignore the impedance is selected. The DC current output from the current detection circuit 11 is a weak current, and is used as the antenna plug 3,
4 so as not to affect the members connected thereto.

Next, when no current flows through any of the plugs 3 and 4, the transmission control circuit 10 determines that the antenna is not connected and prohibits transmission from the signal output circuit 12 to the transmission unit. Output a signal to prohibit transmission. Conversely, when a current flows through both of the plugs 3 and 4, the antenna is switched in accordance with a predetermined priority.

In this way, in this embodiment, an automatic antenna switching circuit can be realized, and a malfunction of the antenna switching caused by manual operation in the past can be prevented. The current detection circuit 11 can be easily configured using transistors.

In the embodiment shown in FIG. 1, a radio device having two antenna plugs 3 and 4 has been described. However, the same applies to a case where three or more antenna plugs are provided to perform antenna switching. is there. Further, as shown in FIG.
In the case where the antenna A is connected to this plug 3 or a plurality of antennas A and B are connected to one plug 3, the antenna changeover switch 2 is omitted and the transmission control circuit 10 Is configured so that only the transmission prohibition signal is output to the transmission unit when the antenna is not connected to the plug 3.

[0013]

According to the present invention, antenna switching or transmission inhibition can be automatically performed according to the presence or absence of an antenna connection.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing a main part of an embodiment of the present invention.

FIG. 2 is a circuit diagram showing a main part of another embodiment of the present invention.

FIG. 3 is a circuit diagram of an antenna switching circuit in a conventional wireless device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Transmission output line 2 Antenna switching circuit 3, 4 Antenna plug 5, 6 Antenna 7 Switch control line 8 High frequency coil 9 Resistance 10 Transmission control circuit 11 Current detection circuit 12 Signal output circuit

Continuation of the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) H04B 1/04 H01Q 1/24

Claims (2)

(57) [Claims] 1. A radio comprising a plurality of plug-in antennas, a plurality of antenna plugs to which these antennas are detachably connected, and an antenna change-over switch for selecting one of the plurality of antenna plugs. In the machine, to the plurality of antennas, an element that causes direct current conduction to ground is connected respectively, and a DC voltage is applied to each of the plurality of antenna plugs to determine whether a DC current flows. The current detection means for detecting the current and the current detection determine whether or not an antenna is connected to the plurality of antenna plugs, output a switching signal to the antenna switch, and prohibit transmission when the antenna is not connected. A wireless device to which a pluggable antenna can be detachably connected, comprising a transmission control circuit provided with signal output means for outputting a transmission prohibition signal. 2. A radio having one or a plurality of plug-in antennas and a single antenna plug to which said antenna is detachably connected, wherein a direct current is connected between said antenna and ground. An element for causing electrical conduction is connected, a DC voltage is applied to the antenna plug, and current detection means for detecting whether or not a DC current flows, and by detecting the current, the antenna connection to the antenna plug is performed. Characterized in that a transmission control circuit having signal output means for outputting a transmission prohibition signal for prohibiting transmission when the antenna is not connected is provided to determine the presence / absence of the antenna, making the pluggable antenna detachable. A radio that can be connected.