Abstract:
A multi-band receiver for converting RF signals in different bands into IF signals in digital multimedia broadcasting (DMB) or digital audio broadcasting (DAB) is provided. The multi-band receiver includes an amplification unit amplifying the at least three RF signals, a voltage controlled oscillator (VCO) generating at least three basic oscillator signals, and an IF signal converting unit converting the at least three RF signals output from the amplification unit into IF signals by using the at least three basic oscillator signals. Each of the at least three basic oscillator signals is constructed with two differential signals having a phase difference of 90 degrees. Accordingly, it is possible to easily design a VCO and reduce the area of the VCO by processing application bands band-II, band-III, and L-band of a DMB system by using one or two VCOs in the multi-band receiver.

Description:
[0001]    This application claims priority to Korean Patent Application No. 10-2006-0102281, filed on Oct. 20, 2006, all the benefits accruing therefrom under 35 U.S.C. §119, the contents of which in their entirety are incorporated herein by reference. 
       BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present invention relates to a receiver for converting an radio frequency (RF) signal into an intermediate frequency (IF) signal in digital multimedia broadcasting (hereinafter, referred to as ‘DMB’) or digital audio broadcasting (hereinafter, referred to as ‘DAB’), and more particularly, to a terrestrial DMB receiver for supporting multi-band. 
         [0004]    2. Description of the Related Art 
         [0005]    Frequency bands used by terrestrial digital multimedia broadcasting (DMB) are various. For example, the frequency bands include band-II, band-III, and L-band. Here, the band-II ranges from 88 MHz (Mega Hertz) to 108 MHz. The band-III ranges from 174 MHz to 245 MHz. The L-band ranges from 1452 MHz to 1492 MHz. 
         [0006]    The terrestrial DMB receiver serves to mix a multi-band RF signal with an oscillator signal of a voltage controlled oscillator (hereinafter, referred to as ‘VOC’) to generate an IF signal, and select only a frequency of a desirable signal through a band pass filter. 
         [0007]      FIG. 1  is a circuit diagram illustrating a conventional multi-band receiver. 
         [0008]    Referring to  FIG. 1 , the conventional multi-band receiver for processing a multi-band signal in the band-II (88˜108 MHz), the band-III (174˜245 MHz), and the L-band (1452˜1492 MHz) includes first to third amplification units, first to third filters, first to third mixers, first to third VCOs, and a band pass filter. First, when an RF signal received through an antenna for band-II (88˜108 MHz) (hereinafter, referred to as ‘first band RF signal’) is provided, the first amplifier amplifies a desirable signal by minimizing noise included in the received signal and controls the gain. In addition, the output of the first amplifier is input into the first filter to remove an image frequency and input into the first mixer. The first mixer mixes the received signal with the oscillator signal output from the first VCO to generate an IF signal. 
         [0009]    On the other hand, an RF signal received through an antenna for band-III (174˜245 MHz) (hereinafter, referred to as ‘second band RF signal’) is input into the second mixer through the second amplifier and the second filter and mixed with the oscillator signal output from the second VCO to generate a desirable IF signal. An RF signal received through an antenna for L-band (1452˜1492 MHz) (hereinafter, referred to as ‘third band RF signal’) is input into the third mixer through the third amplifier and the third filter and mixed with the oscillator signal output from the third VCO to generate a desirable IF signal. 
         [0010]    The generated IF signal passes through the band pass filter so as to remove an image frequency. The band pass filter allows only the frequency of the desirable signal to be selected within a narrow bandwidth, so as to accurately select a channel. 
         [0011]    As described above, in the conventional multi-band receiver, since VCOs for processing the first to third band RF signals are separately constructed, the structure of the conventional multi-band receiver is complex. Since independent buffers are needed for the VCOs, power consumption is large. 
       SUMMARY OF THE INVENTION 
       [0012]    The present invention provides a multi-band receiver that is a terrestrial digital multimedia broadcasting (DMB) receiver capable of processing RF signals in different bands by using a voltage controlled oscillator (VCO) or two VCOs. 
         [0013]    According to an aspect of the present invention, there is provided a multi-band receiver including an amplification unit  204 , a VCO  202 , and an IF signal converter  205 . 
         [0014]    The amplification unit  204  may serve to remove noise from first to third band RF signals (band-II to L-band) and amplify the first to third band RF signals by automatically controlling the gain. The VCO  202  may generate first to third band basic oscillator signals VCO 1  to VCO 3  corresponding to first to third band RF signals (band-II, band-III, and L-band). The IF signal converter  205  may convert the first to third band RF signals (band-II, band-III, and L-band) output from the amplification unit  204  into IF signals by using the first to third band basic oscillator signals VCO 1  to VCO 3 . Each of the first to third band basic oscillator signals VCO 1  to VCO 3  may be constructed with two differential signals having a phase difference of 180 degrees from each other. 
         [0015]    According to another aspect of the present invention, there is provided a multi-band receiver including an amplification unit  305 , first and second VCOs  302  and  303 , and an IF signal converter  306 . 
         [0016]    The amplification unit  305  may serve to remove noise from first to third band RF signals (band-II to L-band) and amplify the first to third band RF signals by automatically controlling the gain. The first VCO  302  may generate first and second band basic oscillator signals VCO 4  and VCO 5  corresponding to first and second band RF signals (band-II and band-III). The second VCO  303  may generate a third band basic oscillator signal VCO 6  corresponding to a third band RF signal (L-band). The IF signal converter  306  may convert the first to third band RF signals (band-II, band-III, and L-band) output from the amplification unit  305  into IF signals by using the first to third band basic oscillator signals VCO 4  to VCO 6 . Each of the first to third band basic oscillator signals VCO 4  to VCO 6  may be constructed with two differential signals having a phase difference of 180 degrees from each other. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0017]    The above and other features and advantages of the present invention will become more apparent by describing in detail exemplary embodiments thereof with reference to the attached drawings in which: 
           [0018]      FIG. 1  is a circuit diagram illustrating a conventional multi-band receiver; 
           [0019]      FIG. 2  is a block diagram illustrating a multi-band receiver according to a first embodiment of the present invention; and 
           [0020]      FIG. 3  is a block diagram illustrating a multi-band receiver according to a second embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0021]    Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the attached drawings. When description of the known techniques or structures related to the present invention is unnecessary, the detailed description will be omitted. 
         [0022]      FIG. 2  is a block diagram illustrating a multi-band receiver according to a first embodiment of the present invention. 
         [0023]    Referring to  FIG. 2 , the multi-band receiver according to the first embodiment of the present invention includes an amplification unit  204 , a voltage controlled oscillator (VCO)  202 , a switch unit  203 , and an intermediate frequency (IF) signal converting unit  205 . 
         [0024]    The amplification unit  204  includes first to third amplifiers  211 ,  241 , and  271 . The first amplifier  211  amplifies only a desirable signal by minimizing noise included in a first band RF signal received through a band-II antenna  212  and automatically controls the gain. The output of the first amplifier  211  is connected to the IF signal converter  205 . The second amplifier  241  amplifies only a desirable signal by minimizing noise included in a second band RF signal received through a band-III antenna  242  and automatically controls the gain. The output of the second amplifier  241  is connected to the IF signal converter  205 . The third amplifier  271  amplifies only a desirable signal by minimizing noise included in a third band RF signal received through an L-band antenna  272  and automatically controls the gain. The output of the third amplifier  271  is connected to the IF signal converter  205 . 
         [0025]    The VCO  202  generates first to third band basic oscillator signals VCO 1  to VCO 3  (band-II to L-band) used to convert first to third band RF signals into IF signals. Each of the first to third band basic oscillator signals VCO 1  to VCO 3  is constructed with two differential signals having a phase difference of 180 degrees from each other. 
         [0026]    The IF signal converting unit includes first to third band IF signal converting units  210 ,  240 , and  270 . 
         [0027]    The first band IF signal converting unit  210  serves to convert the amplified first band RF signal into the first band IF signal by using the first band basic oscillator signal VCO 1 . The first band IF signal converting unit  210  includes a first frequency division unit  220  and a first mixing unit  230 . The first frequency division unit  220  outputs four first-band local oscillator signals LO 1  with phase differences of 90 degrees from one another by dividing the frequency of the first band basic oscillator signal VCO 1 . The first frequency division unit  220  includes first and second frequency dividers  221  and  222 . The first frequency divider  221  divides the frequency of the first band basic oscillator signal VCO 1  by sixteen. The second frequency divider  222  divides the frequency of the signal output from the first frequency divider  221  by two. The first mixing unit  230  mixes the amplified first band RF signal output from the amplification unit  204  with the first-band local oscillator signal LO 1  output from the first frequency division unit  220  to generate the first band IF signal. The first mixing unit  230  includes first and second mixers  231  and  232 . The first and second mixers  231  and  232  mixes two first-band local oscillator signals LO 1  having a phase difference of 180 degrees from each other received from the first frequency division unit  220  with the first band RF signal. The two first-band local oscillator signals LO 1  to be mixed by the first mixer  231  have phase differences of 90 degrees from the two first-band local oscillator signals LO 1  to be mixed by the second mixer  232 . 
         [0028]    The second band IF signal converting unit  240  serves to convert the amplified second band RF signal into a second band IF signal by using the second band basic oscillator signal VCO 2 . The second band IF signal converting unit  240  includes a second frequency division unit  250  and a second mixing unit  260 . The second frequency division unit  250  outputs four second-band local oscillator signals LO 2  with phase differences of 90 degrees from one another by dividing the frequency of the second band basic oscillator signal VCO 2 . The second frequency division unit  250  includes third and fourth frequency divider  251  and  252 . The third frequency divider  251  divides the frequency of the second band basic oscillator signal VCO 2  by eight. The fourth frequency divider  252  divides the frequency output from the third frequency divider  251  by two. The second mixing unit  260  mixes the amplified second band RF signal output from the amplification unit  204  with the second-band local oscillator signal LO 2  output from the second frequency division unit  250  to generate the second band IF signal. The second mixing unit  260  includes first and second mixers  261  and  262 . The first and second mixers  261  and  262  mixes two second-band local oscillator signals LO 2  having a phase difference of 180 degrees from each other received from the second frequency division unit  250  with the second band RF signal. The two second-band local oscillator signals LO 2  to be mixed by the first mixer  261  have phase differences of 90 degrees from the two second-band local oscillator signals LO 2  to be mixed by the second mixer  262 . 
         [0029]    The third band IF signal converting unit  270  serves to convert the amplified third band RF signal into a third band IF signal by using the third band basic oscillator signal VCO 3 . The third band IF signal converting unit  270  includes a third frequency division unit  280  and a third mixing unit  290 . The third frequency division unit  280  outputs four third-band local oscillator signals LO 3  with phase differences of 90 degrees from one another by dividing the frequency of the third band basic oscillator signal VCO 3 . The third frequency division unit  280  includes fifth frequency divider  281 . The fifth frequency divider  281  divides the frequency of the third band basic oscillator signal VCO 3  by two. The third mixing unit  290  mixes the amplified third band RF signal output from the amplification unit  204  with the third-band local oscillator signal LO 3  output from the third frequency division unit  280  to generate the third band IF signal. The third mixing unit  290  includes first and second mixers  291  and  292 . The first and second mixers  291  and  292  mixes two third-band local oscillator signals LO 3  having a phase difference of 180 degrees from each other received from the third frequency division unit  280  with the third band RF signal. The two third-band local oscillator signals LO 3  to be mixed by the first mixer  291  have phase differences of 90 degrees from the two third-band local oscillator signals LO 3  to be mixed by the second mixer  292 . 
         [0030]    The frequency of the first band basic oscillator signal VCO 1  ranges from 2816 MHz to 3456 MHz. The frequency of the second band basic oscillator signal VCO 2  ranges from 2784 MHz to 3920 MHz. The frequency of the third band basic oscillator signal VCO 3  ranges from 2904 MHz to 2984 MHz. 
         [0031]    The multi-band receiver according to the embodiment may further include a frequency synthesizer  201  synthesizing and transmitting a signal with a predetermined frequency to the VCO  202 . 
         [0032]    The multi-band receiver according to the embodiment may further include a switch unit  203  switching and transmitting the first to third band basic oscillator signals VCO 1  to VCO 3  output from the VCO  202  to the IF signal converting unit  205 . 
         [0033]    As described above, the first-band local oscillator signal LO 1  for the band-II (88˜108 MHz) is generated by dividing the frequency of the first band basic oscillator signal VCO 1  by 32. The second-band local oscillator signal LO 2  for the band-III (174˜245 MHz) is generated by dividing the frequency of the second band basic oscillator signal VCO 2  by sixteen. The third-band local oscillator signal LO 3  for the L-band (1452˜2984 MHz) is generated by dividing the frequency of the third band basic oscillator signal VCO 3  by two. 
         [0034]    It will be understood by those skilled in the art that it is possible to apply the present invention to a multi-band having three or more bands by using a VCO without departing from the spirit and scope of the invention by suitably selecting a basic oscillator signal and a frequency divider used to divide the frequency of the basic oscillator signal. 
         [0035]      FIG. 3  is a block diagram illustrating a multi-band receiver according to a second embodiment of the present invention. 
         [0036]    Referring to  FIG. 3 , the multi-band receiver according to the second embodiment of the present invention includes an amplification unit  305 , first and second VCOs  302  and  303 , and an IF signal converting unit  306 . 
         [0037]    The amplification unit  305  includes first to third amplifiers  311 ,  341 , and  371 . The first amplifier  311  amplifies only a desirable signal by minimizing noise included in a first band RF signal received through a band-II antenna  312  and automatically controls the gain. The output of the first amplifier  311  is connected to the IF signal converting unit  306 . The second amplifier  341  amplifies only a desirable signal by minimizing noise included in a second band RF signal received through a band-III antenna  342  and automatically controls the gain. The output of the second amplifier  341  is connected to the IF signal converting unit  306 . The third amplifier  371  amplifies only a desirable signal by minimizing noise included in a third band RF signal received through an L-band antenna  372  and automatically controls the gain. The output of the third amplifier  371  is connected to the IF signal converting unit  306 . 
         [0038]    The first VCO  302  generates first and second band basic oscillator signals VCO 1  and VCO 2  (band-II and band-III) used to convert first and second band RF signals into IF signals. The second VCO  303  generates a third band basic oscillator signal VCO 6  used to convert a third band RF signal (band-III) into an IF signal. Each of the first to third band basic oscillator signals VCO 4  to VCO 6  is constructed with two differential signals having a phase difference of 180 degrees from each other. 
         [0039]    The IF signal converting unit  306  includes first to third band IF signal converting units  310 ,  340 , and  370 . 
         [0040]    The first band IF signal converting unit  310  serves to convert the amplified first band RF signal into the first band IF signal by using the first band basic oscillator signal VCO 4 . The first band IF signal converting unit  310  includes a first frequency division unit  320  and a first mixing unit  330 . The first frequency division unit  320  outputs four first-band local oscillator signals LO 1  with phase differences of 90 degrees from one another by dividing the frequency of the first band basic oscillator signal VCO 4 . The first frequency division unit  320  includes first and second frequency divider  321  and  322 . The first frequency divider  321  divides the frequency of the first band basic oscillator signal VCO 4  by eight. The second frequency divider  322  divides the frequency of the signal output from the first frequency divider  321  by two. The first mixing unit  330  mixes the amplified first band RF signal output from the amplification unit  305  with the first-band local oscillator signal LO 1  output from the first frequency division unit  320  to generate the first band IF signal. The first mixing unit  330  includes first and second mixers  331  and  332 . The first and second mixers  331  and  332  mixes two first-band local oscillator signals LO 1  having a phase difference of 180 degrees from each other received from the first frequency division unit  320  with the first band RF signal. The two first-band local oscillator signals LO 1  to be mixed by the first mixer  331  have phase differences of 90 degrees from the two first-band local oscillator signals LO 1  to be mixed by the second mixer  332 . 
         [0041]    The second band IF signal converting unit  340  serves to convert the amplified second band RF signal into a second band IF signal by using the second band basic oscillator signal VCO 5 . The second band IF signal converting unit  340  includes a second frequency division unit  350  and a second mixing unit  360 . The second frequency division unit  350  outputs four second-band local oscillator signals LO 2  with phase differences of 90 degrees from one another by dividing the frequency of the second band basic oscillator signal VCO 5 . The second frequency division unit  350  includes third and fourth frequency divider  351  and  352 . The third frequency divider  351  divides the frequency of the second band basic oscillator signal VCO 5  by four. The fourth frequency divider  352  divides the frequency output from the third frequency divider  351  by two. The second mixing unit  360  mixes the amplified second band RF signal output from the amplification unit  305  with the second-band local oscillator signal LO 2  output from the second frequency division unit  350  to generate the second band IF signal. The second mixing unit  360  includes first and second mixers  361  and  362 . The first and second mixers  361  and  362  mixes two second-band local oscillator signals LO 2  having a phase difference of 180 degrees from each other received from the second frequency division unit  350  with the second band RF signal. The two second-band local oscillator signals LO 2  to be mixed by the first mixer  361  have phase differences of 90 degrees from the two second-band local oscillator signals LO 2  to be mixed by the second mixer  362 . 
         [0042]    The third band IF signal converting unit  370  serves to convert the amplified third band RF signal into a third band IF signal by using the third band basic oscillator signal VCO 6 . The third band IF signal converting unit  370  includes a third frequency division unit  380  and a third mixing unit  390 . The third frequency division unit  380  outputs four third-band local oscillator signals LO 3  with phase differences of 90 degrees from one another by dividing the frequency of the third band basic oscillator signal VCO 6 . The third frequency division unit  380  includes fifth frequency divider  381 . The fifth frequency divider  381  divides the frequency of the third band basic oscillator signal VCO 6  by two. The third mixing unit  390  mixes the amplified third band RF signal output from the amplification unit  305  with the third-band local oscillator signal LO 3  output from the third frequency division unit  380  to generate the third band IF signal. The third mixing unit  390  includes first and second mixers  391  and  392 . The first and second mixers  391  and  392  mixes two third-band local oscillator signals LO 3  having a phase difference of 180 degrees from each other received from the third frequency division unit  380  with the third band RF signal. The two third-band local oscillator signals LO 3  to be mixed by the first mixer  391  have phase differences of 90 degrees; from the two third-band local oscillator signals LO 3  to be mixed by the second mixer  392 . 
         [0043]    The frequency of the first band basic oscillator signal VCO 4  ranges from 1408 MHz to 1728 MHz. The frequency of the second band basic oscillator signal VCO 5  ranges from 1392 MHz to 1960 MHz. The frequency of the third band basic oscillator signal VCO 3  ranges from 2904 MHz to 2984 MHz. 
         [0044]    The multi-band receiver according to an embodiment of the present invention may further include a frequency synthesizer  301  synthesizing a signal with a predetermined frequency and transmitting to the first and second VCOs  302  and  303 . 
         [0045]    The multi-band receiver according to an embodiment of the present invention may further include a switch unit  304  switching the first to third band basic oscillator signals VCO 4  to VCO 6  output from the first and second VCOs  302  and  303  and transmitting to the IF signal converter  306 . 
         [0046]    As described above, the first-band local oscillator signal LO 1  for the band-II (88˜108 MHz) is generated by dividing the frequency of the first band basic oscillator signal VCO 4  by sixteen. The second-band local oscillator signal LO 2  for the band-III (174˜245 MHz) is generated by dividing the frequency of the second band basic oscillator signal VCO 5  by eight. The third-band local oscillator signal LO 3  for the L-band (1452˜2984 MHz) is generated by dividing the frequency of the third band basic oscillator signal VCO 6  by two. 
         [0047]    It will be understood by those skilled in the art that it is possible to apply the present invention to a multi-band having three or more bands by using two VCOs without departing from the spirit and scope of the invention by suitably selecting a basic oscillator signal and a frequency divider used to divide the frequency of the basic oscillator signal. 
         [0048]    In addition, the multi-band receiver for converting an RF signal into an IF signal according to an embodiment of the present invention may be applied to a case where the frequency of the IF signal is zero, in addition to a case where the frequency of the IF signal is greater than zero. That is, it will be understood by those skilled in the art that the multi-band receiver according to an embodiment of the present invention may be applied to a case where the frequency of the IF signal is zero, that is, a case of direct conversion by slightly modifying the multi-band receiver. 
         [0049]    It is possible to easily design a VCO and reduce the area of the VCO by processing application bands band-II, band-III, and L-band of a DMB system by using one or two VCOs in the multi-band receiver according to an embodiment of the present invention. Since one VCO is used, independent buffer ends are not needed, thereby reducing power consumption. In addition, since a signal with a frequency higher than that of the conventional signal used for the multi-band is generated by the VCO and used, unnecessary interference due to the signal is reduced. It is possible to improve a phase noise characteristic by using a plurality of frequency dividers. In addition, when using two VCOs, it is possible to easily design the VCOs and to reduce the area of each VCO by selecting a suitable frequency divider in a range in which frequency coverage is not high. 
         [0050]    While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the present invention as defined by the appended claims.