WO2013089553A1

WO2013089553A1 - A system and method to detect and switch between internal and external antennas

Info

Publication number: WO2013089553A1
Application number: PCT/MY2012/000169
Authority: WO
Inventors: Keat Loon Hin; A/L Kanagaratnam Pannirselvam; Syahadat Husni Bin Husin Afdzal; Azhar Bin Long Sulaiman Tengku; Vijayan Sarojini Biju
Original assignee: Mimos Bhd
Current assignee: Mimos Bhd
Priority date: 2011-12-16
Filing date: 2012-06-29
Publication date: 2013-06-20
Anticipated expiration: 2014-06-16
Also published as: MY181663A

Abstract

The present invention relates to a system (100) to detect and switch between internal and external antennas. The system (100) checks the connection of the antennas by generating a single tone RF signal and detecting its reflected power. Thereon, the system (100) is able to determine the presence of the antennas and switch between the internal and external antennas in the absence of either one of them. The system (100) comprises of at least one first antenna (110), at least one second antenna (120), at least two RF coupling circuits (130), at least two RF detectors (140), at least two comparators (150), a latching circuit (160), a RF switch circuit (170), a transceiver circuit (180), and a controller (190).

Description

A SYSTEM AND METHOD TO DETECT AND SWITCH BETWEEN INTERNAL

AND EXTERNAL ANTENNAS

FIELD OF INVENTION

The present invention relates to a system and method for detecting the presence of internal and external antennas and switching between the internal and external antennas in the absence or failure of either one of them.

BACKGROUND OF THE INVENTION

Wireless communication devices are often equipped with more than one antenna to improve the quality and reliability of a wireless link. More specifically, the wireless communication devices are equipped with an internal antenna and a connector port for an external antenna. The external antenna may provide a better RF signal receptivity than the internal antenna as it can be flexibly positioned in a less interference environment. Thus, when the external antenna is connected to the connector, RF path is switched from the internal antenna to the external antenna.

A mechanical switch is normally provided to switch between the internal and external antenna. An example of such mechanical switch is disclosed in US Patent No. 5,138,329 which relates to an antenna switch for radio telephones, which are provided with an extendible external antenna and a built-in internal antenna. The antenna switch comprises a microswitch having a switch arm and a press switch. The antenna switch accomplishes the switching-on of the microswitch, whereupon the signal route is connected with the internal antenna. Respectively, when the external antenna is moved in the reverse direction, the signal route is connected with the external antenna. The switch arm is in direct contact with the external antenna so that the contact accomplishes the switching- on of the microswitch, when the external antenna is in a partly pushed in position. The switch arm is situated in close vicinity to the lowest part of the external antenna when the external antenna is in its extended extreme position.

However, the repeated use of the mechanical switch causes reliability and corrosion problems from inserting the external antenna and thus, the mechanical switch may not operate correctly. In order to address the drawbacks of the mechanical switch, electronic based antenna detection and switching system is used. An example of such system is disclosed in PCT Patent Publication No. WO 2005/094154 which relates to a method of external antenna detection and an antenna detector for detecting if an external RF antenna is connected to a transmitter via an external antenna connector. A first low frequency electrical signal is applied to a first conductor of the antenna via the connector, sensing a second low frequency electrical signal on a second conductor of the antenna via the connector, and detecting if the external antenna is connected to the transmitter by comparing the first and second low frequency electrical signals. Preferably, the first low frequency electrical signal is a DC voltage. Preferably, an external antenna is detected to be connected to the transmitter if a magnitude of the second low frequency electrical signal exceeds a predetermined value. In addition, the invention relates to a consumption meter, such as a gas, heat, liquid, such as water, or electricity meter, with an antenna detector according to the described principle.

Another example of the electronic based detection and switching system is disclosed in PCT Patent Publication No. WO 95/13668 which relates to an electronic antenna switching system switches between an internal and an external antenna on a portable radiotelephone. Here, the external antenna contains a coil cord connector. In the coil cord connector an electrical ground or a predetermined voltage is applied to a centre conductor of a coax cable. Internal to the radiotelephone, an antenna detector circuit detects when the second antenna is attached to the electronic antenna switching system and generates a control signal in response thereto. A switch switches the active transmission path between the internal and the external antenna's transmission path in response to the control signal.

However, the electronic based antenna detection and switching system does not check the presence and connection of the internal antenna of the wireless communication device. Continuously transmitting wireless signal to an antenna port without a proper connection to an antenna over a long period of time may result in damaging the transmission circuitry which includes transceiver and power amplifier components. Therefore, there is a need to provide a system for detecting and switching between internal and external antennas that addresses the aforementioned drawbacks. SUMMARY OF INVENTION

The present invention relates to a system and method to detect and switch between internal and external antennas. In one aspect of the present invention, a system to detect and switch between internal and external antennas is provided. The system comprises of at least one first antenna (110), wherein the at least one first antenna (110) is connected to the switch circuit (170), at least one second antenna (120), wherein the at least one second antenna (120) is connected to the switch circuit (170), a switch circuit (170), wherein the switch circuit (170) is connected to the at least one first antenna (110), the at least one second antenna (120) and a transceiver circuit (180), and the transceiver circuit (180). Moreover, the system (100) further includes a controller (190); at least two RF coupling circuits (130), wherein a first RF coupling circuit (130a) is connected to the first antenna transmission path and to a first RF detector (140a), and wherein a second RF coupling circuit (130b) is connected to the second antenna transmission path and to a second RF detector (140b); at least two RF detectors (140), wherein the first RF detector (140a) is connected to the a first RF coupling circuit (130a) and to a first comparator (150a), and wherein the second RF detector ( 40b) is connected to the second RF coupling circuit (130b) and to a second comparator (150b); at least two comparators (150), wherein the first comparator is connected to the first RF detector (140a), a reference voltage and the controller (190), and wherein the second comparator (150b) is connected to the second RF detector (140b), a reference voltage, the controller (190) and a latching circuit (160); and the latching circuit (160), wherein the latching circuit (160) is connected to the RF switch circuit (170), the second comparator (150b) and the controller (190). Preferably, the first antenna (110) is an internal antenna and the second antenna (120) is an external antenna detachable through an antenna connector port.

Preferably, each RF coupling circuit (130) comprises of a bidirectional coupler (131), a resistor (132), and an attenuator (133). Preferably, each RF detector (140) is a diode.

Preferably, the latching circuit (160) is a D-flip-flop circuit. Preferably, the controller (190) is connected to a remote computer (200) through an Ethernet cable.

In another aspect of the present invention, a method for detecting and switching between internal and external antennas (110, 120) is provided. The method is characterised by the steps of a) switching to the second antenna (120); b) generating and transmitting a single tone RF signal to the second antenna (120) by the transceiver circuit (180); c) coupling a reflected RF signal by using the second RF coupling circuit (130b); d) converting the coupled RF signal to a DC voltage by the second RF detector (140b); e) comparing the DC voltage of the reflected RF signal with a reference voltage by the second comparator (150b); f) sending the comparison result to the controller (190); g) transmitting a message to the transceiver circuit (180) by the controller (190) to initiate a wireless connection through the second antenna (120) if the DC voltage of the reflected RF signal is less than the reference voltage; h) transmitting a signal to the latching circuit (160) by the controller (190) to switch to the first antenna (110) if the DC voltage of the reflected RF signal is equal or higher than the reference voltage; i) switching from the first antenna (110) to the second antenna (120) by the RF switch circuit (170); j) generating and transmitting a single tone RF signal to the first antenna (110) by the transceiver circuit (180); k) coupling a reflected RF signal by using the first RF coupling circuit (130a); I) converting the coupled RF signal to a DC voltage by the first RF detector (140a); m) comparing the DC voltage of the reflected RF signal with a reference voltage by the first comparator (150a); n) sending the comparison result to the controller (190); o) transmitting a message to the transceiver circuit (180) by the controller (190) to initiate a wireless connection through the first antenna (120) if the DC voltage of the reflected RF signal is less than the reference voltage; and p) transmitting a message to the remote computer (200) by the controller (190) to initiate a wireless connection through the first antenna (120) if the DC voltage of the reflected RF signal is less than the reference voltage. Preferably, step (a) includes resetting the latching circuit (160) to switch to the second antenna (120) and connecting the second antenna (120) to the transceiver circuit (180) by using the RF switch circuit (170). Preferably, steps (g) and (o) further include repeating steps (b) to (f) after a predetermined duration during the wireless connection.

In yet another aspect of the invention, a method for detecting antenna presence is provided. The method is characterised by the steps of generating and transmitting a single tone RF signal to an antenna (110, 120) by a transceiver circuit (180); coupling a reflected RF signal by using a RF coupling circuit (130); converting the coupled RF signal to a DC voltage by a RF detector (140); comparing the DC voltage of the reflected RF signal with a reference voltage by a comparator (150); sending the comparison result to a controller (190); transmitting a signal indicating the presence of the antenna by the controller (190) if the DC voltage of the reflected RF signal is less than the reference voltage; and transmitting a signal indicating no proper antenna connection by the controller (190) if the DC voltage of the reflected RF signal is equal or higher than the reference voltage. BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention. FIG. 1 shows a block diagram of a system to detect and switch between internal and external antennas (100) according to an embodiment of the present invention.

FIG. 2 shows an exemplary schematic diagram of the system (100) of FIG. 1. FIGS. 3(a-b) show exemplary schematic diagrams of RF coupling circuits (130) of FIG. 1.

FIG. 4 shows a flowchart of a method to detect and switch between internal and external antennas by using the system (100) of FIG. 1. DESCRIPTION OF THE PREFFERED EMBODIMENT

A preferred embodiment of the present invention will be described herein below with reference to the accompanying drawings. In the following description, well known functions or constructions are not described in detail since they would obscure the description with unnecessary detail.

Referring to FIG. 1 , there is shown a block diagram of a system (100) to detect and switch between internal and external antennas according to an embodiment of the present invention. The system (100) checks the connection of the antennas by generating a RF signal and detecting its reflected power. Thereon, the system (100) is able to determine the presence of the antennas and switch between the internal and external antennas in the absence of either one of them. The system (100) comprises of a first antenna (110), a second antenna (120), two RF coupling circuits (130), two RF detectors (140), two comparators (150), latching circuit (160), a RF switch circuit (170), a transceiver circuit (180), and a controller (190). FIG. 2 shows an exemplary schematic diagram for the system (100).

The first antenna (110) is an internal antenna while the second antenna (120) is an external antenna which is detachable through an antenna connector port. Both antennas (110, 120) are connected to the RF switch circuit (170).

The RF coupling circuits (130) are provided to couple a reflected RF signal from each antenna path. FIG. 3a shows a schematic diagram of a first RF coupling circuit (130a). An input of the first RF coupling circuit (130a) is connected to the first antenna transmission path which is in between the first antenna (110) and the RF switch circuit (170). An output of the first RF coupling circuit (130a) is connected to a first RF detector (140a). The first RF coupling circuit (130a) comprises of a first bidirectional coupler (131a), a first resistor (132a), and a first attenuator (133a). The first bidirectional coupler (131a) is connected to the first antenna transmission path. A connection of the first resistor (132a) is connected to the first bidirectional coupler (131a) and another connection of the first resistor (132a) is connected to a common ground. Preferably, the first resistor (132a) provided has a value of 50 ohm. An output of the first bidirectional coupler (131a) is connected to an input of the first attenuator (133a). The output of the first attenuator (133a) is connected to the first RF detector (140a). By coupling the reflected RF signal using the first bidirectional coupler (131a), the power magnitude of a reflected RF signal from the first antenna (110) can be scaled down for detection. Moreover, the power of the reflected RF signal is further scaled down by using the first attenuator (133a). Thereon, the reflected RF signal having power loss due to the first RF coupling circuit (130a) is transmitted to the first RF detector (140a).

Referring now to FIG. 3b, there is shown a schematic diagram of a second RF coupling circuit (130b). An input of the second RF coupling circuit (130b) is connected to the second antenna transmission path which is in between the second antenna and the RF switch circuit (170). An output of the second RF coupling circuit (130b) is connected to a second RF detector (140b). The second RF coupling circuit (130b) comprises of a second bidirectional coupler (131b), a second resistor (132b), and a second attenuator (133b). The second bidirectional coupler (131 b) is connected to the second antenna transmission path. A connection of the second resistor (132b) is connected to the second bidirectional coupler (131 b) and another connection of the second resistor (132b) is connected to a common ground. Preferably, the second resistor (132b) provided has a value of 50 ohm. An output of the second bidirectional coupler (131 b) is connected to an input of the second attenuator (133b). The output of the second attenuator (133b) is connected to the second RF detector (140b). By coupling the reflected RF signal using the second bidirectional coupler (131 b), the power magnitude of a reflected RF signal from the second antenna (110) can be scaled down for detection. Moreover, the power of the reflected RF signal is further scaled down by using the second attenuator (133b). Thereon, the reflected RF signal having power loss due to the second RF coupling circuit (130b) is transmitted to the second RF detector (140b).

The RF detectors (140) are provided to convert the coupled RF signal from the RF coupling circuits (130) into a DC voltage. The converted DC voltage is transmitted to the comparators (150) for comparison with a reference voltage. Preferably, the RF detector (140) used is a diode. A first RF detector (140a) has an input connected to the first RF coupling circuit (130a) and an output connected to a first comparator (150a). A second RF detector (140b) has a similar connection as the first RF detector (140a), wherein an input of the second RF detector (140b) is connected to the second RF coupling circuit (130b) and an output of the second RF detector (140b) is connected to a second comparator (150b). The comparators (150) are provided to compare the DC voltage converted from the coupled RF reflected signal with a reference voltage. The comparison is to check whether the first and second antennas (110, 120) are properly connected and thus, determine the presence of the first and second antennas (110, 120). A first comparator (150a) has an input connected to the first RF detector (140a) and another input connected to a reference voltage. An output of the first comparator (150a) is connected to the controller (190). A second comparator (150b) has an input connected to the second RF detector (140b) and another input connected to a reference voltage. An output of the second comparator (150b) is connected to the controller (190) and to an input of the latching circuit (160).

The latching circuit (160) is used to latch an output signal to the RF switch circuit (170). Preferably, the latching circuit (160) is a D-flip-flop circuit. An output of the latching circuit (160) is connected to the RF switch circuit (170). The output of the latching circuit (160) is based on the outputs of the controller (190) and second comparator (150b).

The RF switch circuit (170) is used to connect the connection from the transceiver circuit (180) to either the first antenna (110) or the second antenna (120).

The transceiver circuit (180) is used to transmit and receive RF signals to/from either the first antenna (110) or the second antenna (120). Moreover, the transceiver circuit (180) is used to generate a single tone RF signal to check the connection of the first and second antennas (110, 120).

The controller (190) is configured to monitor the output from both comparators (150) and control the latching circuit (160) accordingly. The controller (190) has an input connected to the first comparator (150a) and another input connected to the second comparator (150b). Moreover, the controller (190) has an output connected to the latching circuit (160). Preferably, the controller (190) is also connected to a remote computer (200) through an Ethernet cable. This is to provide a maintenance notification in the event that neither the first antenna ( 0) nor the second antenna (120) is present. Referring now to FIG. 4, there is shown a flowchart for detecting and switching between internal and external antennas (110, 120) by using the system (100) of FIG. 1. Initially, the system (100) is turned on and initialized as in step 401. The controller (190) then resets the latching circuit (160) to switch to the second antenna (120) and thus, the RF switch circuit (170) connects the second antenna (120) to the transceiver circuit (180) as in step 402. Thereon, as in step 403, the transceiver circuit (180) generates and transmits a single tone RF signal to the second antenna (120) through the antenna connector port. When the single tone RF signal is transmitted to the second antenna, a RF signal will be reflected from the second antenna (120) to the transceiver circuit due to the mismatch in the characteristic impedance of the load.

In step 404, the reflected RF signal is coupled by using the second RF coupling circuit (130b). For instance, the reflected RF signal has a power magnitude of approximately 1W and by coupling the reflected RF signal with a signal line of approximately 19.6dB at 2.35GHz using the second bidirectional coupler (131 b), the reflected RF signal is scaled down to approximately 11 mW. The reflected RF signal is further scaled down by using the second attenuator (133b) to provide a loss of approximately 10dB. Thus, the second RF coupling circuit (130b) outputs the reflected RF signal having a power of approximately 1.1 mW. Thereon, as in step 405, the reflected RF signal from the second RF coupling circuit (130b) is converted to a DC voltage by the second RF detector (140b). For example, the reflected RF signal with a power of approximately 1.1 mW from the second RF coupling circuit (140b) is converted to a DC voltage of 1.25V. The DC voltage of the reflected RF signal is then compared to a reference voltage by the second comparator (150b) to determine the presence of the second antenna (120) as in step 406. The comparison result is sent by the second comparator (150b) to the controller (190). If the DC voltage of the reflected RF signal is less than the reference voltage, this indicates that the second antenna (120) is present or properly connected and therefore, the controller (190) transmits a message to the transceiver circuit (180) to initiate a wireless connection (decision 407, steps 408 and 409). In steps 410 and 411 , after a predetermined duration during the wireless connection, the controller (190) checks the connection or presence of the second antenna by repeating steps 404 to 406 and decision 407.

However, if the DC voltage of the reflected RF signal is equal or higher than the reference voltage, then this indicates that there is no proper connection to the second antenna (120) and therefore, the controller (190) transmits a signal to the latching circuit (160) to switch to the first antenna (110) as in decision 407, steps 412 and 413. Thereon, as in step 414, the RF switch circuit (170) connects the first antenna (110) to the transceiver circuit (180).

In step 415, the transceiver circuit (180) generates and transmits a single tone RF signal to the first antenna (110). When the single tone RF signal is transmitted to the first antenna (110), a RF signal will be reflected from the second antenna to the transceiver circuit due to the mismatch in the characteristic impedance of the load.

Thereon, as in step 416, the reflected RF signal is coupled using the first RF coupling circuit (130a). For instance, the reflected RF signal has a power magnitude of approximately 1W and by coupling the reflected RF signal with a signal line of approximately 19.6dB at 2.35Ghz using the first bidirectional coupler (131a), the reflected RF signal is scaled down to approximately 11 mW. The reflected RF signal is further scaled down by using the first attenuator (133a) to provide a loss of approximately 10dB. Thus, the first RF coupling circuit (130a) outputs the reflected RF signal having a power of approximately 1.1 mW. The reflected RF signal from the first coupling circuit (130a) is then converted to a DC voltage by the first RF detector (140a). For example, the reflected RF signal with a power of approximately 1.1mW from the first RF coupling circuit (130a) is converted to a DC voltage which results in 1.25V.

The DC voltage of the reflected RF signal is compared to a reference voltage by the first comparator (150a) to determine the presence of the first antenna (110). The comparison result is sent by the first comparator (150a) to the controller (190). If the DC voltage of the reflected RF signal is less than the reference voltage, this indicates that the first antenna (110) is present or properly connected and therefore, the controller (190) transmits a message to the transceiver circuit (180) to initiate a wireless connection (decision 417, steps 418 and 409). After a predetermined duration during the wireless connection, as in steps 410 and 411 , the controller (190) checks the connection or presence of the first antenna (110) by repeating steps 404 to 406 and decision 407.

However, if the DC voltage of the reflected RF signal is equal or higher than the reference voltage, then this indicates that there is no proper connection to the first antenna (110) as in decision 417 and step 419. Therefore, the controller (190) transmits a notification message to the remote computer (200) to notify that neither the first antenna (110) nor the second antenna (120) is present or properly connected and thus, maintenance is required (step 420). Although described in the aforementioned description that the system (100) detects and switches between an internal antenna (110) and an external antenna (120), it is apparent to a person skilled in the art that the system (100) can be modified and implemented for multiple internal antennas and/or multiple external antennas.

While embodiments of the invention have been illustrated and described, it is not intended that these embodiments illustrated and describe all possible forms of the invention. Rather, the words used in the specifications are words of description rather than limitation and various changes may be made without departing from the scope of the invention.

Claims

1. A system (100) to detect and switch between internal and external antennas comprising:

a) at least one first antenna (110), wherein the at least one first antenna (110) is connected to the switch circuit (170),

b) at least one second antenna (120), wherein the at least one second antenna (120) is connected to the switch circuit (170), c) a switch circuit (170), wherein the switch circuit (170) is connected to the at least one first antenna (110), the at least one second antenna (120) and a transceiver circuit (180), and

d) the transceiver circuit (180), characterised in that the system (100) further includes:

e) a controller (190);

f) at least two RF coupling circuits (130), wherein a first RF coupling circuit (130a) is connected to the first antenna transmission path and to a first RF detector (1 0a), and wherein a second RF coupling circuit (130b) is connected to the second antenna transmission path and to a second RF detector (140b);

g) at least two RF detectors (140), wherein the first RF detector (140a) is connected to the first RF coupling circuit (130a) and to a first comparator (150a), and wherein the second RF detector (140b) is connected to the second RF coupling circuit ( 30b) and to a second comparator (150b);

h) at least two comparators (150), wherein the first comparator is connected to the first RF detector (140a), a reference voltage and the controller (190), and wherein the second comparator (150b) is connected to the second RF detector (140b), a reference voltage, the controller (190) and a latching circuit (160); and

i) the latching circuit (160), wherein the latching circuit (160) is connected to the RF switch circuit (170), the second comparator (150b) and the controller (190). The system (100) as claimed in claim 1 , wherein the first antenna (110) is an internal antenna and the second antenna (120) is an external antenna detachable through an antenna connector port.

The system (100) as claimed in claim 1 , wherein each RF coupling circuit (130) comprises of a bidirectional coupler (131), a resistor (132), and an attenuator (133).

The system (100) as claimed in claim 1 , wherein the RF detectors (140) is a diode.

The system (100) as claimed in claim 1 , the latching circuit (160) is a D-flip- flop circuit.

The system (100) as claimed in claim 1 , wherein the controller (190) is connected to a remote computer (200) through an Ethernet cable.

A method for detecting and switching between internal and external antennas (110, 120) by using the system (100) as claimed in claims 1 to 6, is characterised by the steps of:

a) switching to the second antenna (120);

b) generating and transmitting a single tone RF signal to the second antenna (120) by the transceiver circuit (180);

c) coupling a reflected RF signal by using the second RF coupling circuit (130b);

d) converting the coupled RF signal to a DC voltage by the second RF detector (140b);

e) comparing the DC voltage of the reflected RF signal with a reference voltage by the second comparator (150b);

f) sending the comparison result to the controller (190);

g) transmitting a message to the transceiver circuit (180) by the controller (190) to initiate a wireless connection through the second antenna (120) if the DC voltage of the reflected RF signal is less than the reference voltage; h) transmitting a signal to the latching circuit (160) by the controller (190) to switch to the first antenna (110) if the DC voltage of the reflected RF signal is equal or higher than the reference voltage;

i) switching from the first antenna (110) to the second antenna (120) by the RF switch circuit (170);

j) generating and transmitting a single tone RF signal to the first antenna

(110) by the transceiver circuit (180);

k) coupling a reflected RF signal by using the first RF coupling circuit

(130a);

I) converting the coupled RF signal to a DC voltage by the first RF detector (140a);

m) comparing the DC voltage of the reflected RF signal with a reference voltage by the first comparator (150a);

n) sending the comparison result to the controller (190);

o) transmitting a message to the transceiver circuit (180) by the controller

(190) to initiate a wireless connection through the first antenna (120) if the DC voltage of the reflected RF signal is less than the reference voltage; and

p) transmitting a message to the remote computer (200) by the controller (190) to initiate a wireless connection through the first antenna (120) if the DC voltage of the reflected RF signal is less than the reference voltage.

The method as claimed in claim 7, wherein step (a) includes resetting the latching circuit (160) to switch to the second antenna (120) and connecting the second antenna (120) to the transceiver circuit (180) by using the RF switch circuit (170).

The method as claimed in claim 7, wherein steps (g) and (o) further include repeating steps (b) to (f) after a predetermined duration during the wireless connection.

A method for detecting antenna presence is characterised by the steps of: a) generating and transmitting a single tone RF signal to an antenna (110, 120) by a transceiver circuit (180); b) coupling a reflected RF signal by using a RF coupling circuit (130); c) converting the coupled RF signal to a DC voltage by a RF detector (140);

d) comparing the DC voltage of the reflected RF signal with a reference voltage by a comparator (150);

e) sending the comparison result to a controller (190);

f) transmitting a signal indicating the presence of the antenna by the controller (190) if the DC voltage of the reflected RF signal is less than the reference voltage; and

g) transmitting a signal indicating no proper antenna connection by the controller (190) if the DC voltage of the reflected RF signal is equal or higher than the reference voltage.