Antenna system and wireless communication device employing the same

An antenna system in a wireless communication device includes a first antenna, a second antenna, a baseband microchip, a signal sensing unit, a logical circuit, and a switch unit. The first antenna receives and transmits wireless signals; the second antenna transmits wireless signals. The baseband microchip processes the wireless signals and provides a voltage logic signal. The logical circuit logically processes the voltage logic signal and the command signal to generate different switch signals, and the switch unit is controlled by the switch signals from the logical circuit to connect to the first antenna or to the second antenna to transmit the wireless signals.

BACKGROUND

1. Technical Field

The disclosure generally relates to signal transmission, particularly to an antenna system used in a wireless communication device.

2. Description of the Related Art

With wireless communication devices such as mobile phones, it is desirable to keep as low as possible the dose of electromagnetic radiation imposed on the body tissue of a user. The rate at which energy is absorbed by the body when exposed to a radio frequency (RF) electromagnetic field is measured by specific absorption rate (SAR).

As a result, it is necessary to improve antenna design to reduce the SAR value of antennas without compromising the communication quality of the wireless communication device.

Therefore, there is room for improvement within the art.

DETAILED DESCRIPTION

FIG. 1shows a wireless communication device200including an antenna system100, according to an exemplary embodiment of the disclosure. The wireless communication device200can be a mobile phone and includes a main body201, and the antenna system100is positioned within the main body201. In this exemplary embodiment, the antenna system100can work in either of two communication modes, such as global system for mobile communications (GSM) mode and wideband code division multiple access (WCDMA) mode.

Also referring toFIG. 2, the antenna system100includes a first antenna10, a second antenna20, a baseband microchip30, a signal sensing unit50, a logical circuit40, and a switch unit90. The logical circuit40includes an OR gate60, a signal comparison unit70, and a NAND gate80.

The first antenna10is capable of receiving and transmitting wireless signals, such as GSM signals or WCDMA signals. The second antenna20is capable of transmitting the GSM signals or the WCDMA signals. The SAR value of the first antenna10is greater than that of the second antenna20when the first antenna10and the second antenna20transmit wireless signals, due to the differences of structures and installation positions between the first antenna10and the second antenna20. In this exemplary embodiment, the first antenna10is located adjacent to the signal sensing unit50.

The baseband microchip30is electrically connected to the first antenna10and the switch unit90, and is capable of converting (e.g., decoding) the wireless signals received from the first antenna10into corresponding audio signals. The baseband microchip30is further capable of converting (e.g., encoding) the audio signals into corresponding wireless signals, and selectively transmitting the converted wireless signals to the first antenna10or the second antenna20through the switch unit90.

Additionally, the baseband microchip30is electrically connected to the OR gate60. Thus, when the wireless communication device200provides and transmits the WCDMA or GSM signals, the baseband microchip30provides and triggers a high voltage logic signal (e.g., logical 1).

The signal sensing unit50can be a capacitive type transducer, and is electrically connected to the signal comparison unit70. The signal sensing unit50is for detecting and measuring any user-induced pressure. For example, when the user holds the wireless communication device200, the signal sensing unit50senses the user-induced pressure, and then causes capacitance changes therein to generate a corresponding command signal.

The signal comparison unit70prestores a predetermined operating frequency of GSM mode and WCDMA mode, such as GSM1900 or CDMA2000, which have a wide range of SAR values. The signal comparison unit70compares the predetermined operating frequency with a current operating frequency, and generates an electrical signal. The two frequencies may be different for any number of known reasons, such as power fluctuations or interference. In this exemplary embodiment, when user holds or nears the wireless communication device200, the signal sensing unit50generates and outputs the command signal to the signal comparison unit70due to changes in capacitance. The signal comparison unit70is activated by the command signal from the signal sensing unit50, and compares the current operating frequency with the predetermined operating frequency of the wireless communication device200to generate an electrical signal.

In detail, when the current operating frequency is substantially equal to the predetermined operating frequency of the wireless communication device200, the signal comparison unit70generates a high voltage logic signal, such as logical 1. When the current operating frequency is unequal to the predetermined operating frequency, the signal comparison unit70generates and outputs a low voltage logic signal, such as logical 0.

The NAND gate80includes two inputs82and an output84. The two inputs82of the NAND gate80are electrically connected to the signal comparison unit70and the OR gate60respectively. The output84is electrically connected to the switch unit90. The OR gate60is a digital logic gate that implements logical disjunction, and a high output (e.g., logical 1) results if one or both the input signals to the OR gate60are high. On the contrary, the NAND gate80behaves in a manner that is the opposite of the AND gate, such that a low output (e.g., logical 0) results only if both the input signals to the NAND gate80are high. In this exemplary embodiment, the inputs82of the NAND gate80receive electrical signals from both the OR gate60and the signal comparison unit70, and the output84outputs a corresponding switch signal to the switch unit90.

The switch unit90can be an analog switch, controlled by the switch signal from the output84of the NAND gate80to connect to the first antenna10or to the second antenna20. In this exemplary embodiment, when the switch signal from the output84is high, such as logical 1, the switch unit90is will electrically connect to the antenna10. When the switch signal from the output84is low, such as logical 0, the switch unit90is will electrically connect to the second antenna20.

Further referring toFIGS. 1 and 2, when the signal sensing unit50fails to detect any user-induced pressure, and the wireless communication device200works at any frequency band of GSM mode or WCDMA mode, the signal comparison unit70outputs a low voltage logic signal (0) to one of the inputs82, the baseband microchip30triggers and outputs a high voltage logic signal (1) to the other input82. Thus, the output84of the OR gate80outputs a high switch signal (1) to control the switch unit90to connect the first antenna10, forming a first transmission path, and the first antenna10receives and transmits wireless signals along the first transmission path. In such case, since the user lacks physical contact with the wireless communication device200(i.e., using a headset or bluetooth), the user is not fully exposed to the RF electromagnetic field.

When the signal sensing unit50does detects any user-induced pressure, and the wireless communication device200works at any non-predetermined operating frequencies (e.g., adjacent to the predetermined operating frequencies or out of the predetermined operating frequencies) of GSM mode or WCDMA mode, the baseband microchip30outputs a high voltage logic signal (1) to one of the inputs82, the signal comparison unit70compares the predetermined operating frequency with the current operating frequency and outputs a low voltage logic signal (0) to the other input82. Thus, the output84of the OR gate80outputs a high switch signal (1) that controls the switch unit90to connect the first antenna10, and the first antenna10receives and transmits wireless signals along the first transmission path. In such case, the wireless communication device200works at the non-predetermined operating frequencies, this can reduce the SAR value of the first antenna10.

When the signal sensing unit50generates and outputs a command signal to the signal comparison unit70due to any user-induced pressure, and the wireless communication device200works at the predetermined operating frequencies of GSM mode or WCDMA mode such as GSM 1900, CDMA2000, the baseband microchip30outputs a high voltage logic signal (1) to one of the inputs82, the signal comparison unit70outputs a high voltage logic signal (1) to the other input82. Thus, the output84of the OR gate80outputs a low switch signal (0) to control the switch unit90to connect the second antenna20, forming a second transmission path, and the first antenna10receives the wireless signals and transmits the wireless signals to the baseband microchip30. The baseband microchip30processes the wireless signals and transmits the processed wireless signal to the second antenna20through the switch unit90along the second transmission path. In such case, the wireless signals are transmitted by the second antenna20, which can reduce the SAR value due to the structure and installation position of the second antenna20.

Additionally, the antenna system100can also be employed in the wireless communication device200with WCDMA mode or TD-SCDMA mode. Moreover, the OR gate60can be omitted, therefore, the baseband microchip30is directly electrically connected to one of the inputs82to transmit wireless signals and high or low voltage logic signals.

In the antenna system100of this exemplary embodiment, the antenna system100can receive different kinds of wireless signals, so the wireless communication device200can work at different frequency bands, which can selectively minimize the SAR value of the wireless communication device200. In addition, the signal sensing unit50and the signal comparison unit70can output different voltage logic signals (e.g., logical 1 or 0) to control the switch unit90to electrically connect the first antenna10or the second antenna20, resulting in selectively transmitting wireless signals through different transmission paths.

In the present specification and claims the word “a” or “an” preceding an element does not exclude the presence of a plurality of such elements. Further, the word “comprising” does not exclude the presence of other elements or steps than those listed.