Abstract:
A method for controlling power levels of radio signals output by a wireless communications device is disclosed. The wireless communications device includes an RF transceiver. The method includes utilizing the RF transceiver of the wireless communications device to receive RF signals output by a wireless transmission device, and adjusting the power of RF signals output by the wireless communications device according to the power of the RF signals received by the wireless communications device.

Description:
BACKGROUND OF INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The present invention relates to a method for controlling the power of radio frequency (RF) signals emitted by wireless communications device, and more particularly, to a method for adjusting the power of the RF signals emitted by the wireless communications device according the power of the RF signals emitted by a wireless transmission device and received by the wireless communications device.  
           [0003]    2. Description of the Prior Art  
           [0004]    During the past decade, the dramatic development of wireless communications technologies has brought out many kinds of wireless communications devices. Please refer to FIG. 1, which is a block diagram of a wireless communications system  10  according to the prior art. The wireless communications system  10  comprises an access point (AP)  12  and a plurality of wireless communications devices  14 ,  16 , and  18 . The wireless communications device  14  exchanges data with the wireless communications devices  16  and  18  through the AP  12 . Each communications device  14 ,  16 , or  18  has an RF transceiver  80  for emitting and for receiving the RF signals.  
           [0005]    Please refer to FIG. 2, which is a function block diagram of the RF transceiver  80 . The RF transceiver  80  comprises an antenna  20 , a directional coupler  24  electrically connected to the antenna  20 , an RF power detector  26  electrically connected to the directional coupler  24 , a demodulator  28  electrically connected to the RF power detector  26 , and a modulator  30  electrically connected to the directional coupler  24 .  
           [0006]    The antenna  20  of the transceiver  80  receives RF signals emitted by the AP  12  and emits RF signals generated by the wireless communications devices  14 ,  16 , and  18 . The directional coupler  24  comprises a control end  22  for receiving a control signal to switch the antenna  20  to electrically connect with the RF power detector  26  or with the modulator  30 . The RF power detector  26  detects the power of the RF signals received by the antenna  20  and transmitted from the directional coupler  24 . The RF power detector  26  then adjusts the power of the RF signals according to the power of the RF signals such that the RF signals the demodulator  28  receives has a moderate power. The demodulator  28  of the RF transceiver  80  transforms the RF signals, having a moderate power, into intermediate frequency (IF) signals with a demodulating and a band-pass filtering processes.  
           [0007]    For example, when the power of the RF signals received by the antenna  20  is lower than a threshold (the wireless communications devices  14 ,  16 , and  18  are far from the AP  12 ), after detecting that the power of the RF signals is lower than the threshold, the RF power detector  26  increases the power of the RF signals and then transmits the RF signals whose power has been raised to the demodulator  28 . On the other hand, when the power of the RF signals received by the antenna  20  is higher than the threshold (the wireless communications devices  14 ,  16  and  18  are close to the AP  12 ), after detecting that the power of the RF signals is higher than the threshold, the RF power detector  26  decreases the power of the RF signals and then transmits the RF signals whose power has been reduced to the demodulator  28 , preventing the demodulator  28  from receiving the unmodified high-powered RF signals. Too high of powered RF signals may damage the demodulator  28 .  
           [0008]    The modulator  30  of the RF transceiver  80  transforms IF signals into RF signals. The RF signals have a predetermined power. Then the wireless communications devices  14 ,  16 , and  18  emit the RF signals with the antenna  20 . Of course, at this moment, the directional coupler  24  is switched to electrically connect the antenna  20  to the modulator  30 .  
           [0009]    In the prior art wireless communications system  10 , the RF signals emitted by the wireless communications devices  14 ,  16 , or  18  still have the predetermined power, no matter what the distance between the wireless communications devices  14 ,  16 , or  18  and the AP  12  is and how strong the RF signals emitted to the AP  12  need to be.  
         SUMMARY OF INVENTION  
         [0010]    It is therefore a primary objective of the claimed invention to provide a method for a wireless communications device to emit RF signals having a variable power level by determining the power of RF signals emitted by a wireless transmission device and received by the wireless communications device.  
           [0011]    According to the claimed invention, the wireless communications device has an RF transceiver for emitting and for receiving the RF signals. The method includes using the transceiver of the wireless communications device to receive the RF signals emitted by a wireless transmission device, and adjusting the power of the RF signals emitted by the transceiver of the wireless communications device according to the power of the RF signals received by the wireless communications device.  
           [0012]    According to the claimed invention, the transceiver includes an antenna for emitting and for receiving the RF signals, a directional coupler, a power detector for generating a power correction factor according to the power of the RF signals, a modulator for generating the RF signals, and a multiplier electrically connected between the power detector and the modulator for multiplying the RF signals generated by the modulator and the power correction factor generator by the power detector. When the transceiver is receiving the RF signals, the directional coupler is switched to connect the antenna to the power detector and the power detector generates a power correction factor according to the power of the RF signals received by the transceiver. When the transceiver is emitting the RF signals, the directional coupler is switched to connect the antenna to the multiplier, the multiplier multiplies the power correction factor and the RF signals generated by the modulator to generate RF signals of a corrected power, and the antenna emits the RF signals of the corrected power.  
           [0013]    It is an advantage of the claimed invention that a method for the wireless communications device to emit RF signals can reduce the power consumption of the mobile phones  44 ,  46 , and  48 .  
           [0014]    These and other objectives of the claimed invention will no doubt become obvious to those of ordinary skill in the art after reading the following detailed description of the preferred embodiment that is illustrated in the various figures and drawings. 
       
    
    
     BRIEF DESCRIPTION OF DRAWINGS  
       [0015]    [0015]FIG. 1 is a block diagram of a wireless communications system according to the prior art.  
         [0016]    [0016]FIG. 2 is a function block diagram of an RF transceiver of a wireless communications device in the wireless communications system shown in FIG. 1.  
         [0017]    [0017]FIG. 3 is a block diagram of a wireless communications system according to the present invention.  
         [0018]    [0018]FIG. 4 is a function block diagram of an RF transceiver of a wireless communications device in the wireless communications system shown in FIG. 3.  
         [0019]    [0019]FIG. 5 is a flow chart illustrating a method for the communications devices shown in FIG. 3 to emit RF signals. 
     
    
     DETAILED DESCRIPTION  
       [0020]    Because the method of the present invention is applied to a wireless communications device, a preferred embodiment of the wireless communications device is hereby disclosed.  
         [0021]    Please refer to FIG. 3 and FIG. 4. FIG. 3 is a block diagram of a wireless communications system  40  according to the present invention. The wireless communications system  40  comprises an AP  42  and a plurality of wireless communications devices  44 ,  46 , and  48 . Each wireless communications device  44 ,  46 , and  48  comprises an RF transceiver  82 . Each wireless communications devices  44 ,  46 , or  48  can be a mobile phone or a personal data assistant (PDA).  
         [0022]    [0022]FIG. 4 is a function block diagram of the RF transceiver  82  according to the present invention. The RF transceiver  82  comprises an antenna  50 , a directional coupler  54  electrically connected to the antenna  50 , an RF power detector  56  electrically connected to the directional coupler  54 , a demodulator  58  electrically connected to the RF power detector  56 , a multiplier  62  electrically connected to the RF power detector  56  and to the directional coupler  54 , and a modulator  60  electrically connected to the multiplier  62 . The directional coupler  54  has a control end  52 .  
         [0023]    Because the majority of the components in the RF transceiver  82  and corresponding components in the prior art RF transceiver  80  have the same characteristics and functionalities, detailed descriptions of the components of the RF transceiver  82  are omitted. Please note that the RF transceiver  82  further comprises the multiplier  62  and the multiplier  62  is connected between the directional coupler  54 , the RF power detector  56  and the modulator  60 , so the characteristics and the functionalities of the multiplier  62  will be described in the following paragraphs.  
         [0024]    When the mobile phone  44  (the mobile phone  46  or  48 ) is receiving RF signals emitted by the AP  42 , a control signal received by the control end  52  of the directional coupler  54  of the mobile phone  44  switches the directional coupler  54  to electrically connect the antenna  50  with the RF power detector  56 . After receiving the RF signals transmitted from the antenna  50 , the RF power detector  56  detects the power of the RF signals and compares the power with a predetermined power to calculate a power correction factor. The RF power detector  56  then transmits the power correction factor to the multiplier  62 . When the mobile phone  44  is about to emit RF signals, the multiplier  62  multiplies the RF signals generated by the modulator  60  and the power correction factor transmitted from the RF power detector  56  to generate corrected-powered RF signals and transmits the corrected-powered RF signals to the antenna  50  to emit the corrected-powered RF signals. Of course, at this moment, the directional coupler  54  is switched to electrically connect the antenna  50  with the multiplier  62 . Both the RF signals generated by the modulator  60  and the corrected RF signals conform to IEEE 802.11a and 802.11b standards.  
         [0025]    For example, when the RF power detector  56  detects that the power of RF signals received by the antenna  50  is less the predetermined power (the mobile phone  44  is far from the AP  42 ), the RF power detector  56  then calculates a power correction factor larger than one and transmits the power correction factor to the multiplier  62 . When the mobile phone  44  is about to emit RF signals, the modulator  60  generates the RF signals and the multiplier  62  multiplies the RF signals and the power correction factor to generate corrected-powered RF signals and transmits the corrected-powered RF signals to the antenna  50  to transmit the corrected-powered RF signals to the AP  42 , guaranteeing that the corrected-powered RF signals received by the AP  42  are clear enough.  
         [0026]    On the other hand, as the RF power detector  56  detects that the power of RF signals received by the antenna  50  is greater the predetermined power (the mobile phone  44  is near the AP  42 ), the RF power detector  56  then calculates a power correction factor smaller than one and transmits the power correction factor to the multiplier  62 . When the mobile phone  44  is about to emit RF signals, the modulator  60  generates the RF signals and the multiplier  62  multiplies the RF signals and the power correction factor to generate corrected-powered RF signals and transmits the corrected-powered RF signals to the antenna  50  to transmit the corrected RF signals to the AP  42 , saving power consumption when emitting the RF signals of the mobile phone  44 .  
         [0027]    The power detector  56  needs not detect the power of the RF signals received by the antenna  50  and to generate a corresponding power correction factor every time the power detector  56  receives the RF signals. The mobile phone  44  usually does not move very fast. The mobile phone  44  in a car traveling at a speed of  60  miles per hour moves only  88  feet in one second. The  88  foot displacement is neglectable compared to the distance between the mobile phone  44  and the AP  42 . Therefore, the RF power detector  56  of the mobile phone  44  only needs to detect the power of the RF signals received by the antenna  50  of the mobile phone  44  for a short period of time and to generate a corresponding power correction factor periodically. The mobile phone  44  can correct the power of the RF signals generated by the modulator  60  with the corresponding power correction factor during the short period of time.  
         [0028]    The above-mentioned transceiver  82  is a preferred embodiment applied to a method  100  for controlling the power of RF signals emitted by a wireless communications device according to the present invention. The following paragraphs illustrate steps of the method  100 . Please refer to FIG. 5, which is a flow chart illustrating the method  100  for the wireless communications devices  44 ,  46 , and  48  to emit RF signals according to the present invention. The method  100  comprises following steps:  
         [0029]    Step  102 :Start;  
         [0030]    Step  104 :  
         [0031]    Utilizing the antenna  50  of the mobile phone  44  to receive RF signals;(The RF signals are transmitted by the AP  42 .)  
         [0032]    Step  106 :  
         [0033]    Utilizing the RF power detector  56  of the mobile phone  44  to detect the power of the RF signals and generating a corresponding power correction factor according to the power of the RF signals and a predetermined power;(if the power of the RF signals is less than the predetermined power, the RF power detector  56  generates a power correction factor larger than one; On the other hand, if the power of the RF signals is greater than the predetermined power, a power correction factor smaller than one will be generated.)  
         [0034]    Step  108 :  
         [0035]    Utilizing the modulator  60  of the mobile phone  44  to generate RF signals when the mobile phone  44  is about to emit the RF signals;  
         [0036]    Step  110 :  
         [0037]    Utilizing the multiplier  62  of the mobile phone  44  to multiply the RF signals and the power correction factor to generate corrected-powered RF signals;  
         [0038]    Step  112 :  
         [0039]    Utilizing the antenna  50  of the mobile phone  44  to emit the corrected-powered RF signals; (At this moment, the directional coupler  54  is switched to electrically connect the antenna  50  with the multiplier  62 .)  
         [0040]    Step  114 :End.  
         [0041]    As mentioned previously, because the distance between the mobile phone  44  and the AP  42  changes slowly, the step  106  of the method  100  can be executed periodically.  
         [0042]    In contrast to the prior art, not only can the method for the mobile phones  44 ,  46 , and  48  to emit RF signals prevent damage to the mobile phones  44 ,  46 , and  48  from high-powered RF signals, the method can guarantee that the RF signals the AP  42  receives are clear enough and can reduce the power consumption of the mobile phones  44 ,  46 , and  48 .  
         [0043]    Following the detailed description of the present invention above, those skilled in the art will readily observe that numerous modifications and alterations of the device may be made while retaining the teachings of the invention. Accordingly, the above disclosure should be construed as limited only by the metes and bounds of the appended claims.