JPH0813009B2 - Antenna switching circuit for portable radio - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a portable radio device,
In particular, the present invention relates to an antenna switching circuit that switches and connects a fixed antenna mounted on a radio device and an external antenna or the like.

[0002]

2. Description of the Related Art Generally, a portable radio telephone such as an automobile telephone is provided with a switching circuit for switching and connecting a fixed antenna, which is previously installed in a radio, to an external antenna or the like. As a method of switching from a fixed antenna to an external antenna in a conventional antenna switching circuit, a mechanical operation is performed by a switching device such as a high frequency relay or a switching contact of a connector.

FIG. 3 is a diagram showing an example of the configuration of a conventional mobile phone, and shows only an antenna switching circuit portion relating to the present invention. As shown in the figure, due to the structure of the mobile phone, the high frequency unit 31 is arranged on the upper part of the main body 33 near the fixed antenna 32, and the external input / output terminal 34 (connector part) is arranged on the lower part of the main body 33. The unit 31 is connected to the fixed antenna 32 through the external input / output terminal 34 by a transmission line 35 such as a high frequency cable.

[0004]

In the conventional antenna switching circuit as shown in FIG. 3, since the high frequency unit 31 to the antenna 32 are connected via the switching unit 36 of the connector section 34, the length of the transmission line 35 is increased. However, there is a disadvantage that the insertion loss is inevitably increased due to the long length. In addition, the switch 36
As a high-frequency relay is used as this, there is a problem in that the price including the main body and the weight are increased. An object of the present invention is to solve the above problems and provide an inexpensive antenna switching circuit with a small transmission loss.

[0005]

The antenna switching circuit for a portable radio device according to the present invention connects the external antenna to the radio frequency unit of the portable radio device for switching connection between a fixed antenna and an external antenna. A first switch connected between the external input / output terminal and the first internal terminal, and the external antenna and the DC voltage supply source connected between the external voltage supply terminal and the second internal terminal. A connector provided with a second switch that is turned on / off in conjunction with the first switch by inserting / removing the connected external connector, and one end is connected to the high frequency unit and the other end is connected to the fixed antenna. 1 of the wavelength of the connected working frequency
A first transmission line having a length of an odd multiple of / 4, a pin diode connected between the other end of the first transmission line and the ground, and one end of the high frequency unit connected to the connector. A second transmission line having a length that is an odd multiple of ¼ of the wavelength of the operating frequency, the other end of which is connected to the first internal terminal;
The other end of the second transmission line and the second end of the connector
And a series circuit of a high frequency current blocking coil and a resistor for setting the pin diode current, the series circuit being connected between the external terminal and the first terminal when the external connector is inserted into the connector. Switch and the second switch are turned on, a direct current flows through the pin diode to cause a short circuit, the external antenna is connected to the high frequency unit by the second transmission line, and the external connector is removed. When the second switch is turned off, the first switch is turned off, the first internal terminal is connected to the ground, and the fixed antenna is connected to the high frequency unit by the first transmission line. It is characterized by being configured in.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a block diagram showing an embodiment of the present invention, and FIG. 2 is a connection diagram of a switching circuit forming the essential part of the present invention. However, FIG. 1 shows only the portion related to the present invention. In the figure, 1 is a transmission line having a line length of λ / 4, and 2 is a transmission line having a line length of 3λ / 4. Here, λ indicates the wavelength of the frequency used by the wireless telephone. For example, in the case of 900 MHz band, the length of the transmission line 1 of λ / 4 is about 8 cm, which is 3λ / 4.
The transmission line 2 has a length of about 24 cm. The lengths of the transmission line 1 and the transmission line 2 are such that when one end is short-circuited, the impedance at the other end increases due to phase rotation, that is, an odd multiple of the wavelength λ of the operating frequency, that is, 1
/ 4 times, 3/4 times, 5/4 times ..., the size of the portable wireless device, that is, the distance between the high frequency unit 11 and the fixed antenna 12, and the connector for connecting the high frequency unit 11 and the external antenna. Determined by the distance from 9. In the above-described embodiment, the length of the transmission line 1 is set to λ / 4 and the length of the transmission line 2 is 3 due to such conditions.
It is set to λ / 4. The transmission line 1 is realized by, for example, a strip line formed in the middle layer of the multilayer printed wiring board, and is actually provided on the printed wiring board of the high frequency unit 11 together with the high frequency circuit. Further, for the transmission line 2, for example, a coaxial cable or the like is used. 3, 4 and 5 are DC blocking capacitors, 6 is a pin (PIN) diode, 7 is a high frequency current blocking coil, 8 is a pin diode 6 ON / OFF control current setting resistor, and 9 is an external connector insertion / removal It is a connector with mechanical contacts that operate in conjunction with. Reference numeral 10 is an antenna connection circuit, 11 is a high frequency unit, 12 is a fixed antenna, and 13 is a main body of a mobile phone. Reference numeral 14 denotes an external connector, which is connected to a test signal generator when an antenna mounted on a vehicle is connected as an external antenna or when a control test of the portable wireless device is confirmed. There are cases.

When the external connector 14 is connected to the connector 9 in the mobile phone equipped with the above antenna switching circuit, the two switch contacts inside the connector 9 are in a dotted line state as shown in FIG. The DC voltage (+ B) from the resistor 8, the coil 7, the transmission line 2,
It is applied to the pin diode 6 through the transmission line 1. 6 uses a PIN diode having a small ON resistance, and when a direct current flows, point b is electrically short-circuited to the ground.
When the point b has a low impedance, the point a at the other end of the λ / 4 transmission line 1 has a high impedance because the phase is rotated by λ / 4 by the λ / 4 transmission line 1 and the high frequency unit 11
Is connected to the external connector 14 by the external input / output terminal of the connector 9 via the transmission line 2 and the capacitor 5.

Next, when the external connector 14 is removed from the mobile phone, the two switch contacts inside the connector 9 return to the solid line state, the DC voltage (+ B) to the pin diode 6 is cut off, and the point b becomes high. It becomes impedance. At the same time, the contact on the external input / output terminal side inside the connector 9 is connected to the ground, and the high frequency unit 11 is connected to the fixed antenna 12 via the capacitor 3, the transmission line 1 and the capacitor 4. Therefore, the insertion loss of the antenna switching circuit between the fixed antenna 12 and the high frequency unit 11 is only the transmission line 1, and the insertion loss is reduced as compared with the conventional case. Such a switching operation between the fixed antenna 12 and the external input / output terminal is performed in one operation only by inserting / removing the external connector 14 into / from the connector 9 of the mobile phone. Further, the DC voltage required to switch the circuit is the external connector 14
Since it is supplied from the mobile phone, the current from the battery power source of the mobile phone is not required, so there is no concern that the current consumption will increase. .

[0009]

By implementing the present invention, the high-frequency unit and the fixed antenna are connected by one short transmission line 1 as compared with the conventional two transmission lines that are reciprocated. Insertion loss is reduced. Further, since the high frequency relay is not required, the mobile phone body can be made lightweight and inexpensive. Furthermore, the switching operation can be performed with one touch, and the current required for the switching circuit does not consume the battery current that is supplied from the outside and is mounted on the mobile phone. Does not adversely affect the operation of.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an embodiment of the present invention.

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

FIG. 3 is a diagram showing a conventional configuration example.

[Explanation of symbols]

 1 λ / 4 Transmission Line 2 3 λ / 4 Transmission Line 3, 4, 5 DC Current Blocking Capacitor 6 PIN Diode 7 High Frequency Current Blocking Coil 8 Resistor 9 Connector 10 Antenna Connection Circuit 11, 31 High Frequency Unit 12, 32 Antenna 13 , 33 Main body 14, 34 External connector 35 Transmission line 36 Switch

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-54-77507 (JP, A) JP-A-3-18429 (JP, A) Actual opening Sho-50-54916 (JP, U) Actual opening 3- 32843 (JP, U)

Claims (1)

[Claims] 1. A high-frequency unit of a portable radio device is connected between an external input / output terminal for connecting the external antenna and a first internal terminal in order to switch and connect a fixed antenna and an external antenna. And a first switch, and an external connector connected between the external voltage supply terminal and the second internal terminal and connected to the external antenna and the DC voltage supply source interlocks with the first switch by insertion / removal of the external connector. And a second switch that is turned on / off, and a length that is an odd multiple of 1/4 of the wavelength of the operating frequency that has one end connected to the high-frequency unit and the other end connected to the fixed antenna. A first transmission line, a pin diode connected between the other end of the first transmission line and the ground, and one end of the high frequency unit connected to the first internal terminal of the connector. A second transmission line and the other end is 1/4 of an odd multiple of the wavelength of the connected operating frequency in length, the second of said other end and said connector of said second transmission line
And a series circuit of a coil for blocking high frequency current connected between the coil and an internal terminal of the resistor and a resistor for setting the pin diode current, the first circuit when the external connector is inserted into the connector. Switch and the second switch are turned on, a direct current flows through the pin diode to cause a short circuit, the external antenna is connected to the high frequency unit by the second transmission line, and the external connector is removed. When the second switch is turned off, the first switch is turned off, the first internal terminal is connected to the ground, and the fixed antenna is connected to the high frequency unit by the first transmission line. Antenna switching circuit for portable radios configured in.