FR2714776A1 - Current adaptor for car radio telephones - Google Patents

Abstract

The adaptor (10) includes the current connector (11) that plugs into the cigar lighter to provide electric current. The adaptor has the radio frequency input (16) for signals from the external antenna of the radio telephone. The current and RF signals both pass down a wire (12) to the radio telephone input connector (14). A switch formed with the current connector allows selection of the antenna. The connector includes a resistance between a connector and ground which drives the node towards a predetermined value required to activate the switch.

Description

TITLE
CURRENT ADAPTER INCLUDING A RADIO FREQUENCY PORT
INCORPORATED.

Field of the invention
The present invention relates to a current adapter for a portable device, and more particularly to a current adapter comprising a built-in radio frequency port for telecommunications equipment.

Invention background
In a portable battery-powered device, such as a cell phone or other telecommunication device, an external power supply is generally provided so that the user can operate the device from household or vehicle current in order to keep the battery charged. To operate the telecommunication device in a vehicle, current adapters are usually designed to fit on the cigarette lighter base fitted to the vehicle.

The other end of the power adapter - plugs into an external power input connector on the device, or includes what is commonly called in the industry "battery eliminator, which replaces a removable battery coupled to the phone or the telecommunications device.

When using a cell phone or other telecommunication device in a vehicle, it is generally desirable to use an antenna mounted outside the vehicle to improve the performance of the phone. Some phones include a radio frequency (RF) input / output port in addition to the external current input port so that you can use an external antenna. However, such a device requires two separate connectors. On other phones, the external current input port and the input / output port
RF are combined into a single connector on the device. However, such a device typically assumes that an external power supply or an external antenna is connected.

 Therefore, it is necessary to make a single wire single vehicle power adapter also providing an RF input / output allowing connection to the antenna outside the vehicle.

Brief description of the drawings
Figure 1 is a perspective view of a power adapter including an incorporated RF port according to the present invention.

 Figure 2 is a block diagram of the power adapter of Figure 1.

 Figure 3 is a block diagram of a power adapter coupled between an external antenna and a telecommunication device comprising an internal antenna and a circuit for selecting either the internal antenna or the external antenna.

 FIG. 4 is a block diagram of another possible embodiment of a current adapter according to the present invention comprising an external switch selectable by the user making it possible to choose which antenna is coupled to the transmitter. telecommunications device receiver.

 FIG. 5 is a block diagram of a connector 16 of a current adapter allowing the automatic selection of an external antenna according to the present invention.

 FIG. 6 is a block diagram of another embodiment of a connector 16 of a current adapter allowing automatic selection of an external antenna according to the present invention.

 Figure 7 is a block diagram of an antenna designed to be coupled to the power adapter of Figure 2.

 Figure 8 is a block diagram of an antenna designed to be coupled to the power adapter of Figure 2.

Description of preferred embodiments
The present invention provides a current adapter intended to couple an external antenna to a telecommunication device by means of a wire generally plugged into a cigarette lighter of a vehicle or into any other source of current at one end, and into a telecommunication device input connector at the other end. The present invention provides in particular a single wire single-ended car power adapter comprising a radio frequency (RF) input-output port allowing connection to an external antenna. According to certain aspects of the invention, the adapter can be configured to include a number of antenna selection mechanisms. For example, the external antenna could be selected when the power adapter is secured to the telecommunications device. Alternatively, the adapter could include an external switch allowing the user to select the desired antenna. Finally, the adapter could include a switch associated with the RF port which can cause the telecommunication device to select the external antenna when the external antenna is connected to the adapter.

 Referring first to Figure 1, a perspective view of a power adapter according to the present invention is shown. The current adapter 10 comprises a cigarette lighter adapter 11 generally plugged into a cigarette lighter of a vehicle in order to receive current from the vehicle's electrical system. However, a power source could also come from a connector other than the cigarette lighter. A wire 12 is coupled between the cigarette lighter adapter 11 and a connector 14.

The connector 14 is preferably inserted into a base of the telecommunication device designed to receive the connector. According to another possibility, the connector 14 could be associated with a "battery eliminator" to replace a removable battery coupled to the telecommunication device to power the device. Finally, an external RF port 16, preferably associated with the cigarette lighter adapter 11, is designed to receive an antenna wire in order to transmit signals between the device and an antenna outside the vehicle. An RF transmission means is provided by the external RF port 16, and reaches the telecommunication device via the wire 12 and the connector 14.

 Referring now to Figure 2, a detailed block diagram of the power adapter is shown. The current adapter is in particular connected to the external antenna 17 by means of a transmission line 18 (preferably a coaxial cable) at a coaxial connector comprising an external conductor 19 and an internal conductor 20. L the cigarette lighter adapter 11 preferably comprises a connector 16 which is also a coaxial connector.

The connector 16 comprises an external conductor 21 and an internal conductor 22 which are coupled to a transmission line 23 (preferably a coaxial cable) contained in the wire 12. The transmission line 23 comprises an external conductor 24 and an internal conductor 25 which are coupled to a coaxial connector 26 comprising an external conductor 27 and an internal conductor 28. The power adapter 10 is coupled to a telecommunication device, such as a cell phone, by means of the connector 26. Finally, the wire 12 could include other lines 29, such as power transmission lines connecting the cigarette lighter 11 to a telecommunications device or data signals from an electronic control module located in the vehicle.

 Referring now to Figure 3, a detailed block diagram shows the power adapter 10 connected between an external antenna and a telecommunication device 30. The power adapter is identical to the power adapter of the figure 2, except that a direct current (DC) link capacitor 35 and a resistor 37 have been added.

Although only a significant part of the circuits of the telecommunication device used to make this current adapter is shown, it is obvious that other circuits are necessary for the telecommunication device to function. In order to couple the RF signals to the external antenna connector 14 located on the power adapter, the telecommunication device must include an RF switching means to selectively route the RF signals to the internal antenna of the telephone or the port external antenna. In particular, the telecommunication device 30 generally comprises an incorporated antenna 32 coupled to an RF switch 34 by a capacitor 36. The RF switch is coupled to the transceiver part of the telecommunication device and chooses which antenna is used. is connected to the transceiver. The switch could preferably couple the transceiver to an external antenna when the power adapter is used. An example of a reliable RF electronic switch which could be used in the circuit is described in American patent application number 08 / 149,443 entitled "ELECTRONIC ANTENNA SWITCHING
SYSTEM "(electronic antenna switching system") filed November 9, 1993 by Mark
Pennock and assigned to the assignees of the present invention and incorporated therein for reference.

In order for the RF switch to couple the RF signals to the external antenna, the power adapter preferably sends a signal to the telecommunication device 30 indicating that the power adapter is connected and that the external antenna is to be used. The current adapter contains the resistor 37 (preferably 10kQ) coupled to ground so as to emit this signal. Although capacitor 35 and resistor 37 are shown near the inner conductor 28 of the coaxial connector 26, the link capacitor could be placed anywhere along the inner conductor 25 of the transmission line 23, and the resistor could be placed anywhere to allow a path to ground as long as it is on the side of the capacitor closest to the coaxial connector 26. For example, the resistor and the capacitor could be placed inside the cigarette lighter adapter 11. As will be described in detail later, when the path to earth is made possible by the resistance of the current adapter, the circuits of the telecommunication device couple the transceiver of the telecommunications device to its external RF port 40 (and therefore to the external antenna). The telecommunication device comprises bipolar transistors (BJT) 44 and 46 for controlling the RF switch 34. According to the present invention, the transistor 44 is preferably an NPN transistor and the transistor 46 is preferably a PNP transistor. The circuit further comprises a resistor 48, one of which
4s first end is coupled to connector 40 and a second end is coupled, to a node 49, to a capacitor 50 coupled to ground. Resistor 48 and capacitor 50 are also coupled, at node 49, to a resistor 52 which is coupled to the base of transistor 44. A resistor 54 is coupled between base and the emitter of transistor 44 which is coupled to a voltage negative, preferably minus 3.9 volts.

A resistor 56 is also coupled between the collector of transistor 44 (at the control port by switch A) and the base of transistor 46. A resistor 58 is coupled between the base and the emitter of transistor 46, which is coupled to a voltage positive, preferably 4.75 volts. Finally, a resistor 60 is coupled between the collector of transistor 46 (at the control port by switch B) and a negative voltage, preferably minus 3.9 volts.

Although the switching arrangement of the specific transistor of FIG. 3 is an example of a circuit that can be used to switch between an internal antenna and an external antenna, other circuits falling within the scope of the present invention could be used. For example, metal-oxide-semiconductor (MOS) transistors or different reference potentials could be used.

Having described the preferred structure of the switch control circuit, the operation of the circuit will now be described. The resistor 37 of the current adapter activates the RF switch 34 when the current adapter is plugged into the external RF port of the transceiver at the connector 40. In particular, the resistor 37 brings the signal to high. base of transistor 44 up
r approximately O volts which energizes the transistor 44, thus applying a negative voltage to the control port by switch A. Similarly, the base of the transistor 46 is brought to the low state by the collector of the transistor 44, thereby energizing the transistor 46 in order to apply a positive voltage to the control port by switch B.

When a negative voltage is applied to the RF switch control port A and a positive voltage is applied to the RF switch control port B, the RF signals are routed from the transceiver to the external RF port 40 telecommunications device 30.

 If the male connector is removed from the external RF port 40 of the telecommunication device, the base of the transistor 44 is brought to the emitter of the transistor 44, effectively turning off the transistor 44 in order to produce a high voltage at the control port. A of the RF switch 34. The transistor 46 is turned off by the high voltage present at its base, thus applying a negative voltage to the control port by switch B of the RF switch.

When a positive voltage is applied to the switch control port A and a negative voltage is applied to the control port B, RF current is routed from the transceiver to the built-in antenna of the transmitter -receiver.

 According to another aspect of the present invention, it is possible to modify the design of the power adapter to include a user selectable switch for determining whether or not the RF signals should be coupled to the external connector. In particular, Figure 4 shows the current adapter with the resistor 37, as well as a user-selectable switch 70 allowing the RF current to be coupled either to the built-in antenna of the portable device or to the antenna external according to what the user chooses. By disabling the switch 70, the circuits of the telecommunication device 30 is actuated, as described above, to route the RF signals from the transceiver 38 to the external RF port 40 of the telecommunication device. If the switch 70 is left open, the same effect of removing the connector (from the external port 40 of the telecommunication device 30) is obtained as described above, and the RF signals are coupled from the transceiver 38 to the antenna. incorporated 32. The adapter of FIG. 4 can be used with a communication device comprising a circuit like that represented in FIG. 3.

 According to another aspect of the present invention, a connector in which the RF signals are automatically coupled to the external antenna when the external antenna is connected to the power adapter of the external RF port, could be used. FIG. 5 represents the preferred connector 16 of the current adapter 10 allowing the automatic selection of the RF port. In particular, the female mini-UHF antenna connector 22 is expressly designed with a divided central conductor base, the two halves of which are normally electrically insulated.

Half of the base is normally connected to the internal conductor 25 of the transmission line 23.

The other half of the base is connected to resistor 37 which is coupled to ground. When the user connects to a standard external antenna, the two halves of the central conductor base are connected by male end 20 of the external antenna plug.

Thus, a connection to ground is established by a resistor 37 which actuates the switch control circuit of the telecommunication device to couple the RF signals to the external antenna as described above. Therefore, RF signals are automatically coupled to the external antenna when the external antenna is connected.

 Referring now to Figure 6, another possible embodiment of the connector 16 of the power adapter 10 for allowing automatic selection of the RF port is shown. In the other possible embodiment, an additional contact 80 is integrally associated with the connector 16. The additional contact 80 is normally electrically isolated from the external conductor 21 of the connector 16. The additional contact 80 is coupled to a resistor 37, the the other end is coupled to the internal conductor 25 of the transmission line 23. Between this coupling point and the internal conductor 22 of the connector 16, there is also a DC link capacitor 35. When a standard coaxial antenna is connected, the external conductor 19 of the connector connecting the external antenna couples the additional contact 80 to the external conductor 21 of the connector 16, completing the path to ground through the resistor 37, in which the RF signals are automatically coupled to the external antenna. The connectors of Figures 5 and 6 allow the user to operate the power adapter and use the antenna incorporated in the telecommunications device if desired, simply by not connecting an external antenna.

 Referring now to Figure 7, a preferred external antenna 90 which could be coupled to the power adapter of Figure 2 is shown.

In particular, the antenna of Figure 7 includes a DC link capacitor 35 and a resistor 37 which provides a path to ground. Therefore, when the external antenna is connected, the telecommunication device automatically couples the signals
RF through the adapter assembly to the external antenna as described above. The antenna base 92 may include a magnet or a clip to secure the antenna to the vehicle.

 Referring now to Figure 8, another possible embodiment of an external antenna coupled to the power adapter of Figure 2 is shown. The external antenna 90 includes a tuning coil 94 which acts as an autotransformer to provide impedance matching between the antenna 17 and the transmission line 18. The design of the tuning coil provides a direct current path to ground which causes the circuits of the telecommunication device to couple the RF signals via the adapter mounting to the external antenna.

 In summary, the present invention provides a simple device for coupling both current and RF signals from a cigarette lighter adapter to a telecommunications device using a single wire. Consequently, the invention simplifies the connection of an external antenna to a portable cellular telephone using a current adapter of this type. In addition, the power adapter can be configured to allow selection of the external antenna by selectively using a resistor in the adapter, or in the external antenna, to couple the RF signals to the external antenna.

Claims (10)

 1. Current adapter assembly designed to couple current from a current source to a telecommunication device, said assembly being characterized by  a current connector 11 adapted to be coupled to said current source, said current connector comprising a radio frequency (RF) port adapted to couple radio frequency signals from an antenna external to said telecommunication device;  a wire 12 coupled to said current connector for supplying current and RF signals to and from said telecommunication device; and  a user selectable switch 70 associated with being integrated to said current connector making it possible to select an antenna.  2. The current adapter assembly of claim 1, wherein said current connector is characterized by a resistor 37 coupled between a node of said connector and ground, said resistor driving said node of said connector.  r current towards a predetermined value for actuating a switching circuit in said telecommunication device when said current connector is integral with said telecommunication device.  3. The current adapter assembly of claim 4, wherein said antenna is selected from the group characterized by  an antenna 32 completely associated with said telecommunication device; and  an external antenna 17 coupled to said RF port of said current connector.  4. The current adapter assembly of claim 1, wherein said RF port is adapted to automatically couple an external antenna to said telecommunication device when said external antenna is coupled to said RF port.  5. Current adapter assembly designed to couple current and radio frequency signals to a telecommunication device, said telecommunication device being adapted to receive said current adapter assembly and comprising a built-in antenna, said adapter assembly current being characterized by  a first connector 11 designed to be coupled to a current source, said first connector comprising a radio frequency (RF) port designed to couple RF signals to an antenna external to the telecommunications device  a wire 12 including a first end coupled to said current connector for supplying current and RF signals to a telecommunication device;  a second connector 14 coupled to said wire at a second end, said second connector comprising a plurality of contacts for supplying said current and said radio frequency signals to said telecommunication device; and  a resistor 37 placed inside said electric wire and coupled to one of said plurality of contacts, said resistor driving said one of said plurality of contacts of said current connector to a predetermined value in order to couple said external antenna to said device telecommunication.  6. A current adapter assembly of claim 5, further characterized by a switch 70 selectable by the associated user by being integrated with said current connector for selecting an antenna.  7. Portable telecommunication device for transmitting and receiving telecommunication signals, said telecommunication device being characterized by  a transceiver circuit 38 for transmitting and receiving telecommunications signals  an antenna 32 associated by being integrated into said portable telecommunication device;  a switching circuit 34 coupled to said antenna incorporated in said telecommunication device for coupling said incorporated antenna to said transceiver and decoupling said incorporated antenna from said transceiver; and  a current adapter 10 coupled to said switching circuit, said current adapter comprising a wire coupled to a current connector for supplying current and RF signals to said telecommunication device.  8. The portable telecommunication device of claim 7, wherein the current connector is characterized by a user selectable switch 70 associated by being integrated with the current connector to select an antenna.  9. The portable telecommunication device of claim 7, further characterized by an external antenna 17 coupled to a radio frequency port.  10. The portable telecommunication device of claim 9, wherein said external antenna is characterized by a resistor 37 coupled to ground, said resistor driving said node of said current connector to a predetermined value in order to actuate a switch located in said device. telecommunications when said antenna is integral with said current adapter.