Abstract:
A WLAN transceiving system, which comprises: a plurality of antennas; a plurality of receiving circuits, wherein each one of receiving circuits is coupled to one of the antenna to receive a input signal from the antennas; and a plurality of transmitting circuits, for outputting one of an output signal and an amplified output signal, wherein at least one of the transmitting circuit includes a power amplifier and utilizes at least one of the power amplifier to amplify an output signal to generate the amplified output signal, where a number of the power amplifiers is less than a number of the antennas.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of U.S. Provisional Application No. 61/101,143, filed on 2008 Sep. 29 and entitled “Unequal Multiple-Antenna Transceiver”, the contents of which are incorporated herein by reference. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present invention relates to a WLAN (wireless Local Area Network) transceiving system, and particularly relates to a WLAN transceiving system utilizing an unequal mechanism. 
         [0004]    2. Description of the Prior Art 
         [0005]    In the field of WLAN communication, a WLAN transceiving system generally includes single antenna or multiple antennas for data transmission. A single-antenna system with one transmitter and one receiver (i.e. 1T1R system) has the lowest cost. However, the throughput performance thereof is lower than that of the multiple antenna systems in the near range. The stability is also unsatisfactory in the middle range due to no MRC (Maximum Ratio Combining) gain, as shown in  FIG. 1 . 
         [0006]    Besides, for a multiple-antenna system (MIMO) with one transmitter and two receivers (i.e. 1T2R system), the throughput performance is better than that of above 1T1R system in middle/long range. However, the throughput is lower than that of a multiple transmitter system in near range, since only one transmitter exists. It is a disadvantage for peer-to-peer communication, especially for high speed file sharing. 
         [0007]    Please refer to  FIG. 1  again, for a multiple antenna system with two transmitters and two receivers (i.e. 2T2R system), the throughput performance is the best among 1T1R, 1T2R and 2T2R systems in near/middle/long ranges. However, the 2T2R system is the most expensive one. Additionally, it is also difficult to integrate two CMOS PAs (power amplifier) into a SoC chip, because of the higher power consumption and heat dissipation in the smaller IC package. Additionally, power amplifiers occupy a large region (20%˜25% of a transceiving circuit) and consumes a large amount of current (ex. consumes current of 50 mA˜60 mA, when gain of the power amplifiers is 0 dBM). 
       SUMMARY OF THE INVENTION 
       [0008]    One embodiment of the present invention is to provide a WLAN transceiving system with an unequal mechanism achieved by hardware or software, to decrease cost or meet different requirement. 
         [0009]    One embodiment of the present invention discloses a WLAN transceiving system, which comprises: a plurality of antennas; a plurality of receiving circuits, wherein each one of receiving circuits is coupled to one of the antenna to receive a input signal from the antennas; and a plurality of transmitting circuits, for outputting one of an output signal and an amplified output signal, wherein at least one of the transmitting circuit includes a power amplifier and utilizes at least one of the power amplifier to amplify an output signal to generate the amplified output signal, where a number of the power amplifiers is less than a number of the antennas. 
         [0010]    Another embodiment of the present invention discloses a WLAN transceiving system, which comprises: a plurality of antennas; a transceiving circuit, and at least one power amplifier. The transceiving circuit comprises: at least one receiver, for receiving at least one input signal from the antennas; and at least one transmitter, for outputting at least one output signal. The power amplifier is coupled between one of the transmitters and one of the antennas, for amplifying the output signal, where a number of the power amplifiers is less than a number of the antennas. 
         [0011]    Still another embodiment of the present invention discloses a WLAN transceiving system, which comprises: a plurality of antennas; a plurality of receiving circuits, wherein each one of receiving circuits is coupled to one of the antenna to receive an input signal from the antennas; and a plurality of transmitting circuits, for outputting an amplified output signal, wherein each of the transmitting circuits includes a power amplifier and utilizes part of the power amplifiers as operating power amplifiers to amplify an output signal to generate the amplified output signal. 
         [0012]    Another embodiment of the present invention discloses a WLAN transceiving system, which comprises: a plurality of antennas; a transceiving circuit, and at least one power amplifier. The transceiving circuit comprises: at least one receiver, for receiving at least one input signal from the antennas; and at least one transmitter, for outputting at least one output signal. The power amplifier is coupled between one of the transmitters and one of the antennas, wherein part of the power amplifiers are utilized operating power amplifiers for amplifying the output signal. 
         [0013]    The above-mentioned embodiments can be utilized for a WLAN communication system following the spec: giga bit WLAN, 802.11 AC, AD, but not limited. Via above-mentioned embodiments, the numbers of power amplifiers can be saved, such that the occupied region and cost of power amplifiers can decrease. Besides, different communication specification can be utilized to meet various requirements. 
         [0014]    These and other objectives of the present 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 THE DRAWINGS 
         [0015]      FIG. 1  is a schematic diagram illustrating the relation between throughput and attenuation of WLAN communication systems for different types. 
           [0016]      FIG. 2  is a block diagram illustrating a WLAN transceiving system according to an embodiment of the present application. 
           [0017]      FIG. 3  is a schematic diagram illustrating the comparing result of the relation of throughput and attenuation, between the WLAN communication system of the embodiment shown in  FIG. 2  and prior art WLAN communication systems. 
           [0018]      FIG. 4(   a ) and  FIG. 4(   b ) are block diagrams illustrating WLAN transceiving systems according to embodiments of the present application. 
       
    
    
     DETAILED DESCRIPTION 
       [0019]    Certain terms are used throughout the description and following claims to refer to particular components. As one skilled in the art will appreciate, electronic equipment manufacturers may refer to a component by different names. This document does not intend to distinguish between components that differ in name but not function. In the following description and in the claims, the terms “include” and “comprise” are used in an open-ended fashion, and thus should be interpreted to mean “include, but not limited to . . . ”. Also, the term “couple” is intended to mean either an indirect or direct electrical connection. Accordingly, if one device is coupled to another device, that connection may be through a direct electrical connection, or through an indirect electrical connection via other devices and connections. 
         [0020]      FIG. 2  is a block diagram illustrating a WLAN transceiving system  200  according to an embodiment of the present application. As shown in  FIG. 2 , the WLAN transceiving system  200  includes antennas  201 ,  203 , transmitting circuits  205 ,  207 , receiving circuits  209 ,  211  and a baseband circuit  213 . In this embodiment, the receiving circuits  209 ,  211  not only include RF receivers  225  and  227  but also include low noise amplifiers  221  and  223  to amplify input signals IN. However, the low noise amplifiers  221  and  223  can be removed if the input signals IN are strong enough or due to other considerations. The transmitting circuits  205 ,  207  respectively include RF transmitters  224  and  226  to output the output signals OS, but only the transmitting circuit  205  includes the power amplifier  229  for amplifying the output signal OS to generate the amplified output signal AOS. Such structure is named an unsymmetrical mechanism, which can be achieved via software or hardware. The embodiment shown in  FIG. 2  discloses an unsymmetrical mechanism achieved via hardware. Besides, a PA driver can (not shown) be provided in the transmitter (ex. in a mixer of the transmitter) to provide driving current to the power amplifier. 
         [0021]    Accordingly, the transmitting circuit  207  can be utilized when a strong output signal OS is not necessary (ex. for a short distance communication), and the transmitting circuit  205  can be utilized when a stronger output signal AOS is needed (ex. for a long distance communication). In this case, the WLAN transceiving system  200  can further include a controller (not shown) to control which transmitting circuit should operate. By this way, the number of power amplifiers can be saved. Thus the circuit area and power consumption due to power amplifiers can decrease as well. Besides, the transmitting circuits  205  and  207  can utilize different signal communication specifications. For example, the transmitting circuit  205  can follow OFDMA specification, and the transmitting circuit  207  can follow MIMO specification. By this way, loose signal communication specification can be utilized and different end user requirements can be met. 
         [0022]    Moreover, the WLAN transceiving system  200  can further include T/R switches  215  and  217  to perform a switch operation between the transmitting circuit  205  and the receiving circuit  209 , and a switch operation between the transmitting circuit  207  and the receiving circuit  211 . Additionally, the WLAN transceiving system  200  can further include an antenna switch  219  to switch the receiving circuits  209 ,  211  to different antennas. However, the T/R switches  215 ,  217  and the antenna switch  219  can also be removed from the WLAN transceiving system. 
         [0023]    The main concept that the embodiment shown in  FIG. 2  represents is: the number of the power amplifiers for transmitters is less than the number of antennas, such that the transmitters can be controlled to utilize the power amplifiers to amplify the signals to be output or not, depending whether a stronger output signal is needed. In other words, the power consumption of transmitting circuit  205  and the power consumption of transmitting circuit  207  are designed to be different when data transmission so that the whole system  200  has more flexibility in power control. Please note the structure of the WLAN transceiving system  200  is only for example and does not mean to limit the scope of the present application. Moreover, the numbers of antennas, transmitting circuits and receiving circuits are not limited to two, and the number of the power amplifier is not limited to one. Additionally, the transmitting circuit  207 , the receiving circuits  209 ,  211 , the baseband circuit  213 , and the RF transmitter  224  can be integrated a chip  231  (or regarded as an transceiving circuit). In this case, the power amplifier  229  can be regarded as an external power amplifier. 
         [0024]    On the other hand, low noise amplifiers  221  and  223  can also be designed as an unsymmetrical architecture or mechanism. For example, low noise amplifier  223  has lower power consumption than low noise amplifier  221 , the WLAN transceiving system  200  can select antenna  203  to receive data when the transmission signal is strong (ex. for a short distance communication). Contrarily, the WLAN transceiving system  200  can select antenna  201  to receive data when the transmission signal is weak (ex. for a long distance communication). The architecture of unsymmetrical low noise amplifiers  221  and  223  can get the advantage of power controlling flexibility as the unsymmetrical the transmitting circuits  205  and  207  mentioned above. 
         [0025]      FIG. 3  is a schematic diagram illustrating the comparing result of the relation for throughput and attenuation, between the WLAN communication system of the embodiment shown in  FIG. 2  and prior art WLAN communication systems. As shown in  FIG. 3 , in near range for the wireless PAN (WPAN) application, the throughput is higher with multiple antennas. In middle range, the stability is good with MRC gain. The transmission range is also longer by using switched antenna diversity. 
         [0026]      FIGS. 4(   a ) and  4 ( b ) are block diagrams illustrating WLAN transceiving systems  400  and  450  according to another embodiment of the present application. For brevity, some reference numerals in  FIGS. 4(   a ) and  4 ( b ) are omitted for sake of brevity. 
         [0027]    Please refer to  FIG. 4(   a ), comparing with the WLAN transceiving system  200 , the unsymmetrical mechanism of the WLAN transceiving system  400  is achieved via hardware and the unsymmetrical mechanism of the WLAN transceiving system  400  can be achieved via software. The WLAN transceiving system  400  includes transmitting circuits  401 ,  403 , receiving circuits  405 ,  407 , a baseband circuit  409  and antennas  411 ,  413 . In this embodiment, both the transmitting circuits  401 ,  403  include power amplifiers  415 ,  417 . However, power amplifiers  415 ,  417  can be controlled by control signals CS, which can be generated from a controller (not illustrated), to be enabled or disabled. In this case, the power amplifier is named an operating power amplifier when it is enabled. Accordingly, when anyone of the transmitting circuits  401 ,  403  does not need the power amplifier to amplify the output signal, the power amplifier can be disabled, if both the power amplifiers are initially enabled. Alternatively, when anyone of the transmitting circuits  401 ,  403  needs the power amplifier to amplify the output signal, the power amplifier can be enabled, if both the power amplifiers are initially disabled. In other words, the WLAN transceiving system  400  achieves the unsymmetrical mechanism via software. Other characteristics are disclosed in above mentioned description, thus it is omitted for brevity here. 
         [0028]    The WLAN transceiving system  450  has similar elements and structure with which of the WLAN transceiving system  400 . One of the differences is that the WLAN transceiving system  450  further includes switches  451 ,  453 , and passing by paths  455 ,  457 . If anyone of the output signals OS from the RF transmitters  459 ,  461  is needed to be amplified, the switches  451 ,  453  will switch the path to the power amplifier  463   465 , such that the output signal OS can be amplified to an amplified output signal AOS. Alternatively, if the output signal OS from the RF transmitters  459 ,  461  need no amplifying, the switches will switch the path to paths  455 ,  457 , such that the output signal OS can be directly output. In other words, the WLAN transceiving system  450  also achieves the unsymmetrical mechanism via software. The embodiment disclosed in  FIG. 2  can also utilize the unsymmetrical mechanism disclosed in  FIG. 4 . That is, it is not limited that the embodiment disclosed in  FIG. 2  must utilize all the power amplifiers. The embodiment disclosed in  FIG. 2  can utilize only part of the power amplifiers, the same as the embodiment shown in  FIG. 4 . Similarly, other characteristics are disclosed in above mentioned description, thus it is omitted for brevity here. 
         [0029]    The above-mentioned embodiments can be utilized for a WLAN communication system following the spec: giga bit WLAN, 802.11 AC, AD, but not limited. Via above-mentioned embodiments, the numbers of PA or LNA can be saved, such that the occupied region and cost of power amplifiers can decrease. Besides, different communication specification can be utilized to meet various requirements. 
         [0030]    Those skilled in the art will readily observe that numerous modifications and alterations of the device and method 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.