1. Field of the Invention
The present invention relates to a radio-frequency (RF) device and wireless communication device, and more particularly, to an RF device and wireless communication device capable of maintaining radiating efficiency, reducing design and manufacturing costs.
2. Description of the Prior Art
A wireless communication device is equipped with an antenna to emit or receive radio waves, so as to exchange radio-frequency (RF) signals and access a wireless communication system. Radio waves are high-frequency sinusoidal signals, such that every country in the world standardizes the power of radio waves, mainly for preventing from affecting users and/or interfering operations of other wireless communication devices. For example, the International Commission on Non-Ionizing Radiation Protection (ICNIRP) suggests the value of Specific Absorption Rate (SAR) shall not exceed 2.0 W/Kg, while the Federal Communications Commission (FCC) suggests the value of SAR shall not exceed 1.6 W/Kg. SAR represents the absorption rate of a living body unit per the power of electromagnetic waves in a normal electromagnetic radiation environment, taking W/Kg as a unit. Additionally, various communication products are applied to various environments, so that distance factor is further taken into consideration. For example, SAR of handset wireless communication device such as mobile device or smart phones needs to be verified when the distance between the handset wireless communication device and a human body is 20 cm.
As well known in the art, antenna efficiency will be affected when reducing interferences caused by the wireless communication device (i.e. reducing SAR value of the wireless communication device). Therefore, to keep the antenna efficiency, the prior art has disclosed many methods. One is using a proximity sensor to detect an event of approach of a human body; that is, reducing RF power when the proximity sensor detects that a human body is approaching, while keeping or appropriately increasing RF power when the proximity sensor does not detect approach of any human body. In such a condition, interference can be reduced, and meanwhile, antenna efficiency is kept. However, the prior art proximity sensor includes a receiver or sensor which contains metal materials to detect capacitance variation when a human body is approaching, so as to determine an event of approach of a human body. In addition, the added receiver or sensor affects the antenna efficiency, such that the operating frequency band becomes narrow. In other words, the operating frequency band of the antenna, which is originally suitable for broadband demand, is narrowed due to the added receiver or sensor of the proximity sensor. In such a condition, multiple antennas must be designed separately for various communication systems of nearing frequency band demands, causing increase of design and manufacturing costs, and disadvantage of component managements.
Therefore, the prior art needs to be improved.