Abstract:
An apparatus and method for converting a frequency of a high frequency signal received from an antenna in an ultra wide band communication system transmitting and receiving using at least two reference frequencies. The method includes generating generation frequencies having frequencies set to convert the frequency of the high frequency signal and mixing the frequency of the high frequency signal and the generation frequencies in at least two stages.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]     This application claims the benefit under 35 U.S.C. § 119 (a) from Korean Patent Application No. 2004-37336 filed on May 25, 2004 in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference.  
       BACKGROUND OF THE INVENTION  
       [0002]     1. Field of the Invention  
         [0003]     Embodiments of the present invention generally relate to ultra wide band (UWB) communication systems. More particularly, embodiments of the present invention generally relate to apparatuses and methods generating radio frequency (RF) signals used in a multi-band of a UWB communication system.  
         [0004]     2. Description of the Related Art  
         [0005]     In general, communication systems use frequencies within a predetermined band to transmit and receive data. The data used in the communication systems can be classified into circuit data and packet data. The circuit data must be transmitted and received in real time, such as voice signals. The packet data has a predetermined bandwidth, or a greater bandwidth, and is not necessarily transmitted in real time, unlike the circuit data. The frequency band used to transmit the circuit data is generally narrow while the frequency band used to transmit the packet data may be wider.  
         [0006]     As described above, when the amount of data to be transmitted increases, an increased frequency band may be used. Hereinafter, the wider frequency band can be referred to as an ultra wide band (UWB). The UWB can be divided into a plurality of sub-bands, each having a predetermined bandwidth. A UWB communication system can transmit data using the plurality of sub-bands to transmit and receive a large amount of data per unit time. The UWB communication system selects one of the plurality of sub-bands and transmits data using the selected sub-band so as to increase security for data. In other words, the UWB communication system sequentially uses the plurality of sub-bands so as to increase the security for the transmitted data.  
         [0007]      FIG. 1  illustrates frequency band(s) used in a conventional UWB communication system. As shown in  FIG. 1 , the frequency band used in the UWB communication system can be 3432 MHz to 10032 Mhz, for example. In this example, the frequency band can be divided into four sub-band groups A, B, C and D. The group A may include three sub-bands, group B may include two sub-bands, group C may include four sub-bands, and group D may include four sub-bands  
         [0008]     In this example, reference frequencies of the three sub-bands of the group A can be 3432 MHz, 3960 MHz, and 4488 MHz, respectively, the reference frequencies of the two sub-bands of the group B can be 5016 MHz and 5808 Mhz, respectively, reference frequencies of the four sub-bands of the group C can be 6336 MHz, 6864 MHz, 7392 MHz, and 7920 MHz, respectively, and the reference frequencies of the four sub-bands of the group D can be 8448 MHz, 8976 MHz, 9504 MHz, and 10032 Mhz, respectively. The two sub-bands of the group B may overlap with frequency bands used in a currently used wireless local area network (WLAN), and in this example, the four sub-bands of the group D may not be currently used in the current level of technology.  
         [0009]     As described above, a UWB communication system necessarily requires an appropriate structure to generate signals having reference frequencies used therein. Hereinafter, the structure of such a UWB communication system will be described, along with the corresponding method of generating the signals having the reference frequencies used in such a UWB communication system.  
         [0010]      FIG. 2  illustrates the structure of a receiver in a UWB communication system. The corresponding structure of a transmitter of such a UWB communication system can be derived based on the same.  
         [0011]     The receiver of the UWB communication system includes an antenna  200 , a band pass filter (BPF)  202 , a mixing stage including mixers  204  and  206 , low pass filters (LPFs)  208  and  210 , variable gain amplifiers (VGAs)  212  and  214 , analog-to-digital converters (ADCs)  216  and  218 , and a sub-band generator (SBG)  220 . In addition to these components, the UWB communication system may include additional and/or alternate components.  
         [0012]     The antenna  200  transmits a wireless signal to and/or receives a wireless signal from the transmitter of the UWB communication system. The BPF  202  extracts only a signal having a frequency used in the UWB communication system from the wireless signal. The frequency used in the UWB communication system is generally 3 GHz to 5 GHz. The signal having passed through the BPF  202  is transmitted to the mixers  204  and  206 . The mixer  204  receives a signal generated by the SBG  220 . The SBG  220  will be described in detail later with reference to  FIGS. 3 and 4 . The SBG  220  generates both a signal that is not phase shifted and a signal that is 90° phase shifted and transmits the signal that is not phase shifted to the mixer  204  and the signal that is 90° phase shifted to the mixer  206 .  
         [0013]     The mixer  204  mixes the received signals and transmits the mixed signal to the LPF  208 . The LPF  208  removes a noise component from a low frequency of the mixed signal generated in the mixing process. The LPF  208  extracts only one of a plurality of reference frequencies (which have been converted into low frequency signals through the mixing process) used in the UWB communication system. The VGA  212  corrects a magnitude of a received signal to be more constant. The ADC  216  converts a received analog signal into a digital signal. The operations of the mixer  206 , the LPF  210 , the VGA  214 , and the ADC  218  can be the same as those of the mixer  204 , the LPF  208 , the VGA  212 , and the ADC  216  and thus will not be described herein.  
         [0014]      FIG. 3  illustrates the structure of the SBG  220  shown in  FIG. 2 . The SBG  220  includes a local oscillator  300 , a phase-locked loop (PLL)  302 , divide by 8 and divide by 2 dividers  304  and  306 , single side bands (SSBs)  308  and  312 , and a selector  310 . The SBG  220  generating the three reference frequencies of the illustrated group A will now be described with reference to  FIG. 3 .  
         [0015]     The local oscillator  300  generates a signal having a frequency of 4224 MHz. The PLL  302  stabilizes the frequency of the signal generated by the local oscillator  300 . The signal generated by the local oscillator  300  is then transmitted to the divide by 8 divider  304  and the SSB  312 . The divide by 8 divider  304  divides the frequency of the signal by 8. A frequency of a signal output from the divide by 8 divider  304  is 528 MHz. The signal divided by the divide by 8 divider  304  is transmitted to the divide by 2 divider  306  and the SSB  308 . The divide by 2 divider  306  divides a frequency of the received signal by 2. Thus, a frequency of a signal output from the divide by 2 divider  306  is 264 MHz. The signal divided by the divide by 2 divider  306  is then transmitted to the SSB  308  and the selector  310 . The SSB  308  mixes the signal having the frequency of 528 MHz and the signal having the frequency of 264 MHz to generate a signal having a frequency of 792 MHz. The signal generated by the SSB  308  is transmitted to the selector  310 . The selector  310  selects one of the signals having the frequencies of 264 MHz or 792 MHz and transmits the selected signal to the SSB  312 .  
         [0016]     The SSB  312  mixes and outputs the signal having the frequency of 4224 MHz transmitted from the local oscillator  300  and one of the signals having the frequencies 264 MHz and 792 MHz selected by the selector  310 . In more detail, when the SSB  312  receives the signal having the frequency of 264 MHz from the selector  310 , the SSB  312  generates and outputs signals having frequencies of 3960 MHz and 4488 MHz. When the SSB  312  receives the signal having the frequency of 792 MHz from the selector  310 , the SSB  312  generates and outputs a signal having a frequency of 3432 MHz. The SGB  220  thus selects and generates one of the signals having the frequencies of 3960 MHz, 4488 MHz, and 3432 Mhz, for example, using the above-described structures.  
         [0017]      FIG. 4  illustrates another example of an SBG. Elements in  FIG. 4  similar to those of  FIG. 3  will not be further described herein. Rather, hereinafter, the structure of the SBG will be described based on phase shifters  410  and  420  and SSBs  308  and  312 . The phase shifters  410  and  420  generate and output signals that are phase shifted and signals that are not phase shifted. In general, the two signals output from the phase shifter  410  or  420  have a phase difference of 90°.  
         [0018]     The operation of the SSB  308  will now be described. Here, the Q component of an intermediate frequency (IF) signal (transmitted to the phase shifter  410 ) is input to a mixer  412  and an I component of the IF signal is input to a mixer  414 . The Q component of the IF signal input to the mixer  412  is sin(w  IF t), and the I component of the IF signal input to the mixer  414  is cos(w  IF t). An I component of a local oscillator (LO) signal (transmitted from the phase shifter  408 ) is input to the mixer  412 , and a Q component of the LO signal is input to the mixer  414 . The operations of the mixers  412  and  414  are set forth using Equations 1 and 2 below, respectively:  
                 sin   ⁡     (       w   LO     ⁢   t     )       ⁢     cos   ⁡     (       w   IF     ⁢   t     )         =       1   2     ⁡     [       sin   ⁡     (       (       w   LO     +     w   IF       )     ⁢   t     )       +     sin   ⁡     (       (       w   LO     -     w   IF       )     ⁢   t     )         ]               Equation   ⁢           ⁢   1                   cos   ⁡     (       w   LO     ⁢   t     )       ⁢     sin   ⁡     (       w   IF     ⁢   t     )         =       1   2     ⁡     [       sin   ⁡     (       (       w   LO     +     w   IF       )     ⁢   t     )       -     sin   ⁡     (       (       w   LO     -     w   IF       )     ⁢   t     )         ]               Equation   ⁢           ⁢   2             
 
         [0019]     Equation 1 identifies the operation of the mixer  412 , and Equation 2 identifies the operation of the mixer  414 . The signals mixed by the mixers  412  and  414  are transmitted to an adder  416 . The adder  416  adds the signals received from the mixers  412  and  414 . The operation of the adder  412  is set forth below, using Equation 3:  
                   1   2     ⁡     [       sin   ⁡     (       (       w   LO     +     w   IF       )     ⁢   t     )       +     sin   ⁡     (       (       w   LO     -     w   IF       )     ⁢   t     )         ]       +       1   2     ⁡     [       sin   ⁡     (       (       w   LO     +     w   IF       )     ⁢   t     )       -     sin   ⁡     (       (       w   LO     -     w   IF       )     ⁢   t     )         ]         =     sin   ⁡     (       (       w   LO     +     w   IF       )     ⁢   t     )               Equation   ⁢           ⁢   3             
 
         [0020]     As shown in Equation 3, the adder  416  outputs an upper side band signal having a frequency obtained by adding the frequency of the LO signal and the frequency of the IF signal. In other words, when the SSB  308  receives a signal having a frequency of 528 MHz from the phase shifter  410  and a signal having a frequency of 264 MHz from the phase shifter  408 , the SSB  308  outputs a signal having a frequency of 792 MHz.  
         [0021]     The SSB  312  performs the same operation as the SSB  308 . In other words, when the SSB  312  receives a signal having a frequency of 4224 Mhz from phase shifter  420  and a signal having a frequency of 264 MHz from a selector  418 , a subtracter  430  outputs a signal having a frequency of 3960 MHz. When the SSB  312  receives a signal having a frequency of 4224 MHz from phase shifter  420  and a signal having a frequency of 264 MHz from the selector  418 , an adder  432  outputs a signal having a frequency of 4488 MHz. When the SSB  312  receives a signal having a frequency of 4224 MHz from the phase shifter  420  and a signal having a frequency of 792 MHz from the selector  418 , the subtracter  430  outputs a signal having a frequency of 3432 MHz, and the adder  432  outputs a signal having a frequency of 5016 MHz.  
         [0022]     As described above, the conventional SBG includes a plurality of SSBs, a plurality of dividers, a plurality of switches, and a plurality of phase shifters. Thus, this SBG consumes a large amount of power. Also, since the SBG uses a high frequency band, several parasitic components are generated in a mixing process. Thus, an I signal cannot exactly match with a Q signal. Also, isolation performance of the switches becomes deteriorated. Moreover, harmonics components are generated by the plurality of dividers and a plurality of mixers. As a result, signals having undesired frequencies are generated.  
       SUMMARY OF THE INVENTION  
       [0023]     Accordingly, embodiments of the present invention may solve the above-mentioned and problems. Embodiments of the present invention include an apparatus and a method for reducing a number of components of an SBG, decreasing power consumption of the SBG.  
         [0024]     Another embodiment of the present invention includes an apparatus and a method allowing an operation of a UWB communication system using a high frequency band to be performed in an intermediate frequency band.  
         [0025]     To achieve the above and/or other aspects and advantages, embodiments of the present invention sets forth a method of converting a frequency of an ultra wide band (UWB) communication high frequency signal received from an antenna in an ultra wide band (UWB) communication system transmitting and receiving using at least two reference frequencies, including generating generation frequencies having frequencies set to convert the frequency of the high frequency signal, and mixing the frequency of the high frequency signal and the generation frequencies at least once to generate an intermediate frequency signal and mixing the intermediate frequency signal and the generation frequencies to generate low frequency signals used in the UWB communication system.  
         [0026]     The at least two reference frequencies may include 3432 MHz, 3960 MHz, and 4488 MHz. In addition, the reference frequencies may respectively correspond to frequencies of sub-bands of a frequency band for UWB communication.  
         [0027]     The generation frequencies may include at least one of 1320 MHz, 2112 MHz, 2640 MHz and 3168 MHz.  
         [0028]     In addition, the mixing of the frequency of the high frequency signal and the generation frequencies at least once to generate the intermediate frequency signal and mixing the intermediate frequency signal and the generation frequencies to generate low frequency signals used in the UWB communication system may further include mixing the frequency of the high frequency signal with one of the generation frequencies 2112 MHz, 2640 MHz and 3168 MHz to generate the intermediate frequency, mixing the intermediate frequency with the generation frequency of 1320 MHz.  
         [0029]     I and Q components may be extracted from the generation frequency of 1320 MHz and mixed with the intermediate frequency.  
         [0030]     The generation frequencies of 2112 MHz and 3168 MHz may also be generated by dividing the generation frequency of 2640 MHz into frequencies of 528 MHz and mixing the frequencies of 528 MHz with the generation frequency of 2640 MHz.  
         [0031]     To achieve the above and/or other aspects and advantages, embodiments of the present invention sets forth an apparatus for converting a frequency of a ultra wide band (UWB) communication high frequency signal received from an antenna in an ultra wide communication system transmitting and receiving using at least two reference frequencies, including a sub-band generator generating generation frequencies having frequencies set to convert the frequency of the high frequency signal, and at least two mixers respectively mixing the frequency of the high frequency signal with the generation frequencies at least once to generate an intermediate frequency signal and mixing the intermediate frequency signal and the generation frequencies to generate low frequency signals used in the UWB communication system.  
         [0032]     The sub-band generator may generates the generation frequencies to be at least one of 1320 MHz, 2112 MHz, 2640 MHz and 3169 MHz.  
         [0033]     The at least two mixers may include a first mixer mixing the frequency of the high frequency signal with one of the generation frequencies of 2112 MHz, 2640 MHz and 3168 MHz to generate the intermediate frequency, and second mixers mixing the intermediate frequency with the generation frequency of 1320 MHz.  
         [0034]     The second mixers may mix the intermediate frequency with I and Q components extracted from the generation frequency of 1320 MHz transmitted from the sub-band generator. The sub-band generator may further include a divider dividing the generation frequency of 2640 MHz into a frequency of 528 MHz, and a mixer mixing the frequency of 528 MHz and the generation frequency of 2640 MHz to generate the generation frequencies of 2112 MHz and 3168 MHz.  
         [0035]     To achieve the above and/or other aspects and advantages, embodiments of the present invention sets forth an ultra wide band (UWB) communication apparatus, including an attenna receiving a high frequency signal, a band pass filter band pass filtering the high frequency signal, a sub-band generator generating generation frequencies having frequencies set to convert the frequency of the high frequency signal, at least two mixers respectively mixing the frequency of the high frequency signal with the generation frequencies at least once to generate an intermediate frequency signal and mixing the intermediate frequency signal and the generation frequencies to generate low frequency signals used in the UWB communication system, and at least one low pass filter to low pass filter the generated low frequency signals.  
         [0036]     Additional aspects and/or advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0037]     These and/or other aspects and advantages of the invention will become apparent and more readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings of which:  
         [0038]      FIG. 1  illustrates exemplary sub-bands used in a UWB communication system;  
         [0039]      FIG. 2  illustrates a receiver of a UWB communication system;  
         [0040]      FIG. 3  illustrates an SBG generating reference frequencies used in a UWB communication system;  
         [0041]      FIG. 4  illustrates another SBG generating reference frequencies;  
         [0042]      FIG. 5  illustrates a receiver of a UWB communication system, according to an embodiment of the present invention;  
         [0043]      FIG. 6  illustrates frequencies generated by an SBG, according to an embodiment of the present invention; and  
         [0044]      FIG. 7  illustrates an SGB generating reference frequencies, according to an embodiment of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0045]     Reference will now be made in detail to the embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to the like elements throughout. The embodiments are described below to explain the present invention by referring to the figures.  
         [0046]     Further, matters detailed in the description, such as a detailed construction and elements, are only provided to assist in a comprehensive understanding of the invention. Thus, it is apparent that embodiments of the present invention can be carried out without these detailed matters. Also, well-known functions or constructions are not described herein in detail since they would obscure the invention in unnecessary detail.  
         [0047]     The signals generated by the SBG shown in  FIG. 2  are transmitted to the LPFs  208  and  210  by performing the mixing in one stage. However, in embodiments of the present invention, signals generated by an SBG can be transmitted to LPFs by performing mixing processes in at least two stages. In other words, a two-stage mixing process can be performed to solve problems occurring in the use of a high frequency band.  
         [0048]      FIG. 5  illustrates a receiver of a UWB communication system, according to an embodiment of the present invention. Referring to  FIG. 5 , the receiver of the UWB communication system can include an antenna  500 , a BPF  502 , mixers  504 ,  506  and  508 , LPFs  512  and  514 , VGAs  516  and  518 , and ADCs  520  and  522 . As shown in  FIG. 5 , a received signal can undergo a mixing process in two stages and before being transmitted to the LPFs  512  and  514 . A user may also select whether the received signal undergoes the mixing process in the at least two stages, or in a single stage, for example. In this case, a number of stages a mixing process is performed can be proportional to the number of mixers.  
         [0049]     The antenna  500  transmits a wireless signal to and/or receives a wireless signal from a transmitter of the UWB communication system. The BPF  502  can extract only a signal having a frequency used in the UWB communication system from the wireless signal. The signal having passed through the BPF  502  is then transmitted to the mixer  504 . The mixer  504  receives a signal generated by the SBG  510 . The SBG  510  will be described in detail later with reference to  FIGS. 6 and 7 . The mixer  504  mixes the signals received from the BPF  502  and the SBG  510  and transmits the mixed signal to the mixers  506  and  508 . The mixer  506  mixes the signal received from the mixer  504  with a signal received from the SBG  510  and transmits the mixed signal to the LPF  512 . The LPF  512  removes a noise component from a low frequency of the mixed signal generated in the mixing process. The LPF  512  also extracts only one of a plurality of reference frequencies (which have been converted into low frequency signals through a substantial mixing process) used in the UWB communication system. The VGA  516  can then correct the magnitude of thereceived signal. The ADC  520  converts the received analog signal to a digital signal. The operations of the mixer  508 , the LPF  514 , the VGA  518 , and the ADC  522  can be the same as those of the mixer  506 , the LPF  512 , the VGA  516 , and the ADC  520  and thus will not be described further herein.  
         [0050]     The transmitter of the UWB communication system can have an inverse structure to the structure of the receiver of the UWB communication system shown in  FIG. 5 . The structure of the SBG  510  will now be described in detail with reference to  FIGS. 6 and 7 .  
         [0051]      FIG. 6  illustrates frequencies of signals generated by the SBG  510 . In particular, frequencies used for generating reference frequencies of group A are shown in  FIG. 6 . Frequencies used for reference frequencies of the other groups, other than group A, may be generated using a corresponding method.  
         [0052]     As shown in  FIG. 6 , in order to generate the reference frequencies of the group A, I and Q signals having frequencies of 1320 MHz, and signals having frequencies of 2640 MHz, 2112 MHz, and 3168 MHz are generated.  
         [0053]     A process of generating the I and Q signals having the frequencies of 1320 MHz and the signals having the frequencies of 2640 MHz, 2112 MHz, and 3168 MHz using the SBG  510  will now be described with reference to  FIG. 7 . Hereinafter, frequencies generated by the SBG  510  will be referred to as generation frequencies.  
         [0054]     The SBG  510  can include a local oscillator  700 , a PLL  702 , a divide by 5 divider  706 , a mixer  708 , and a selector  710 . The number of components of the SBG  510  shown in  FIG. 7  is smaller than the number of components of the SBG shown in  FIG. 2 . The SBG  510 , according to an embodiment of the present invention, will now be described in greater detail with reference to  FIG. 7 .  
         [0055]     The local oscillator  700  generates signals having frequencies of 1320 MHz and 2640 MHz. The local oscillator  700  generally generates the signals having the frequencies of 1320 MHz and simultaneously a signal having a frequency twice the frequency of 1320 MHz, that is, a frequency of 2640 MHz. The local oscillator  700  can also generate I and Q signals from the signals having the frequencies of 1320 MHz. I and Q signals having the frequencies of 1320 MHz generated by the local oscillator  700  can then be transmitted to the mixers  506  and  508 . The PLL  702  stabilizes the frequencies of the I and Q signals generated by the local oscillator  700 .  
         [0056]     The signal having the frequency of 2640 Mhz, generated by the local oscillator  700 , is transmitted to the selector  710 , the mixer  708 , and the divide by 5 divider  706 . The divide by 5 divider  706  divides the frequency of 2640 MHz of the signal transmitted from the local oscillator  700 . Thus, the divide by 5 divider  706  transmits a signal having a frequency of 528 Mhz, generated by dividing the frequencies of 2640 Mhz, to the mixer  708 . The mixer  708  mixes the signal having the frequency of 2640 MHz received from the local oscillator  700  and the signal having the frequency of 528 MHz received from the divide by 5 divider  706 . The mixer  708  generates a signal having a frequency of 2112 MHz and a signal having a frequency of 3168 MHz by performing the mixing process. The signals generated by the mixer  708  are transmitted to the selector  710 . The selector  710  selects one of the transmitted signals and transmits the selected signal to the mixer  504 . An example of a method of generating reference frequencies in sub-bands of group A is thus shown in  FIG. 7 . However, reference frequencies in sub-bands of the other groups, other than group A, may be generated using a method similar to the method shown in  FIG. 7 .  
         [0057]     Operations of the mixers  504 ,  506  and  508  will be described below with reference to  FIG. 5 .  
         [0058]     The mixer  504  mixes the signal received from the BPF  502  with one of the signals having the frequencies 2112 MHz, 2640 MHz, and 3168 MHz received from the SBG  510 . Due to the mixing process performed by the mixer  504 , the signal having a high frequency component transmitted from the BPF  502  is converted into a signal in an intermediate frequency band. The signal in the intermediate frequency band is transmitted to the mixers  506  and  508 .  
         [0059]     The mixer  506  mixes the signal in the intermediate frequency band received from the mixer  504  with a signal, e.g., the I signal, received from the local oscillator  700 . The mixer  508  also mixes the signal in the intermediate frequency band received from the mixer  504  with a signal, e.g., the Q signal received from the local oscillator  700 . The number of mixers shown in  FIG. 5  is greater than the number of mixers shown in  FIG. 2 . However, the frequencies of the signals transmitted to the mixers  506  and  508  are lower than the frequency of the signal transmitted to the mixer  504 . In general, a mixing process performed in a low frequency band has higher reliability and lower power consumption than a mixing process performed in a high frequency band. Thus, although the number of mixers shown in  FIG. 5  is greater than the number of mixers shown in  FIG. 2 , the mixers shown in  FIG. 5  consume less power than the mixers shown in  FIG. 2 . Since the SBG  510  can have a simple structure, e.g., as shown in  FIG. 7 , the total power consumption of the transmitter and the receiver of the UWB communication system, according to an embodiment of the present invention, is smaller than the total power consumption of the transmitter and the receiver of the UWB communication system shown in  FIG. 2 .  
         [0060]     Table 1 below shows comparisons between frequencies of signals transmitted to the mixers  204  and  208  and frequencies of signals transmitted to the mixers  504 ,  506 , and  508 .  
                                         TABLE 1                             FIG. 2       FIG. 5              Mixer 204   Mixer 208   Mixer 504   Mixer 506   Mixer 508               High frequency   High frequency   High frequency   Low frequency   Low frequency       signal (I signal)   signal (Q signal)   signal (3 GHz to   signal (I signal),   signal (Q signal),       (3 GHz to 5 GHz),   (3 GHz to 5 GHz)   5 GHz) 2112 MHz,   1320 MHz   1320 MHz       3432 MHz,   3432 MHz,   2640 MHz,       3960 MHz,   3960 MHz,   3168 MHz       4488 MHz   4488 MHz                  
 
         [0061]     As described above, signals having lower frequencies than frequencies of signals transmitted to conventional mixers are transmitted to mixers of embodiments of the present invention. In other words, high frequencies of transmitted signals can be converted into low frequencies using a two-stage mixing process. Further, errors occurring in each component of the present invention and overall power consumption can be reduced.  
         [0062]     As described above, in embodiments of the present inveniton, a high frequency transmitted from an antenna of the UWB communication system can be converted into a low frequency using at least a two-stage mixing process. Power consumption of each component can be reduced, and the probability of an error occurring can be lowered. Also, an SBG can generate I and Q signals from one frequency so as to reduce errors.  
         [0063]     Although a few embodiments of the present invention have been shown and described, it would be appreciated by those skilled in the art that changes may be made in these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the claims and their equivalents.