Abstract:
A down-frequency conversion circuit and up-frequency conversion circuit, and a receiver and transmitter applying the same are provided. The down-frequency conversion circuit includes a harmonic mixer and general mixer, and thus becomes able to convert frequency using one LO (Local Oscillator) frequency, thereby reducing burden on generating LO frequency.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application claims the priority of Korean Patent Application No. 10-2011-0131345, filed on Dec. 8, 2011 in the KIPO (Korean Intellectual Property Office), which is incorporated herein by reference in its entirety. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     Methods and apparatuses consistent with the exemplary embodiments relate to a down-converter, up-converter, receiver and transmitter applying the same, and more particularly, to a down-converter and up-converter using a plurality of mixers, and a receiver and transmitter applying the same. 
     2. Background Art 
     In a 60 GHz RF (Radio Frequency) system for high speed data transmission, the method of generating LO (Local Oscillator) signals for frequency conversion is very difficult. 
     Especially, it is necessary to generate a swing full enough to switch a mixer, and to generate a high frequency of 60 GHz. In a case of making a transceiver with a direct conversion type frequency conversion circuit, generating signals of 60 GHz consumes a lot of power and is highly sensitivity to parasitic, making it difficult to adjust the LC resonance. Furthermore, using a double conversion type frequency conversion circuit requires various LOs, and thus it becomes necessary to generate a VCO (Voltage Controlled Oscillator) frequency of a common high frequency, or make various VCOs. 
     As such, each of the two types of conventional frequency converters has its advantages, but they also have disadvantages. Thus, there is a need to seek a method for providing a frequency converter which overcomes the above disadvantages of those two types of conventional frequency converters. 
     SUMMARY OF THE INVENTION 
     1. Technical Problem 
     The present disclosure has been presented to resolve the aforementioned problems, and the purpose of the present disclosure is to provide a down-converter and up-converter which include a harmonic mixer and general mixer, and to provide a receiver and transmitter applying the same. 
     2. Means for Solving the Technical Problem 
     According to an exemplary embodiment of the present invention, a down-converter may include a harmonic mixer where a signal of a first frequency, an In-phase signal of a second frequency, and a quadrature phase signal of the second frequency are input, and which outputs a signal of a third frequency generated by subtracting a twice value of the second frequency from the first frequency; a first mixer where a signal of the third frequency and an In-phase signal of the second frequency are input, and which outputs an In-phase signal of a fourth frequency generated by subtracting the second frequency from the third frequency; and a second mixer where a signal of the third frequency and a quadrature phase signal of the second frequency are input, and which outputs a quadrature phase signal of a fourth frequency generated by subtracting the second frequency from the third frequency. 
     In addition, the first frequency may be carrier frequency, the second frequency may be LO (Local Oscillator) frequency, the third frequency may be intermediate frequency, and the fourth frequency may be baseband frequency. 
     Furthermore, the first frequency may be 60 GHz, and the second frequency may be 20 GHz. 
     In addition, the aforementioned down-frequency conversion circuit may be applied to a receiver. 
     Meanwhile, according to an exemplary embodiment of the present disclosure, an up-converter may include a third mixer where an In-phase signal of a fifth frequency and an In-phase signal of a sixth frequency are input, and which outputs a signal of a seventh signal generated by adding the sixth frequency to the fifth frequency; a fourth mixer where a quadrature phase signal of the fifth frequency and a quadrature phase of the sixth frequency are input, and which outputs a signal of a seventh frequency generated by adding the fifth frequency to the sixth frequency; and a harmonic mixer where a signal of the seventh frequency, an In-phase signal of the sixth frequency, and a quadrature signal of the sixth frequency are input, and which outputs a signal of an eighth frequency generated by adding a twice value of the sixth frequency to the seventh frequency. 
     In addition, the fifth frequency may be baseband frequency, the sixth frequency may be LO (Local Oscillator) frequency, the seventh frequency may be intermediate frequency, and the eighth frequency may be carrier frequency. 
     Furthermore, the sixth frequency may be 20 GHz, and the eighth frequency may be 60 GHz. 
     In addition, the aforementioned up-frequency conversion circuit may be applied to a transmitter. 
     3. Advantageous Effects of Invention 
     According to various exemplary embodiments of the present disclosure, it becomes able to provide a down-converter and up-converter which include a harmonic mixer and general mixer, and a receiver and transmitter applying the same, thereby enabling frequency conversion using one Local Oscillator (LO) frequency and reducing burden on generating LO frequency. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and/or other aspects of the present disclosure will be more apparent by describing certain present disclosure with reference to the accompanying drawings, in which: 
         FIG. 1  illustrates a structure of a down-frequency conversion circuit, according to an exemplary embodiment of the present disclosure; 
         FIG. 2  is a down-frequency conversion circuit which includes a buffer amplifier, according to an exemplary embodiment of the present disclosure; 
         FIG. 3  is a circuit diagram illustrating the down-frequency conversion circuit of  FIG. 1  in more detail, according to an exemplary embodiment of the present disclosure; 
         FIG. 4  illustrates a structure of an up-frequency conversion circuit, according to an exemplary embodiment of the present disclosure; and 
         FIG. 5  is a circuit diagram illustrating the up-converter of  FIG. 4  in more detail, according to an exemplary embodiment of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     Certain exemplary embodiments are described in higher detail below with reference to the accompanying drawings. 
     In the following description, like drawing reference numerals are used for the like elements, even in different drawings. The matters defined in the description, such as detailed construction and elements, are provided to assist in a comprehensive understanding of exemplary embodiments. However, exemplary embodiments can be practiced without those specifically defined matters. Also, well-known functions or constructions are not described in detail since they would obscure the application with unnecessary detail. 
       FIG. 1  is a diagram illustrating a structure of a down-frequency conversion circuit  100 , according to an exemplary embodiment of the present disclosure. As illustrated in  FIG. 1 , the down-frequency conversion circuit  100  includes a harmonic mixer  110 , first mixer  120 , and second mixer  130 . 
     Herein, the first mixer  120  and second mixer  130  are general mixers. A general mixer outputs a signal of a frequency generated by adding or subtracting an LO (Local Oscillator) frequency to/from an input signal frequency. Meanwhile, in the harmonic mixer, an input signal, and two LO frequency signals having reverse phases in a same frequency are input, and the harmonic mixer outputs a signal of a frequency generated by adding or subtracting a twice value of frequency of the LO frequency to/from the input signal frequency. 
     In the harmonic mixer  110 , signals (RFIP, RFIN) of a first frequency, In-phase signals (LOIP, LOIN) of a second frequency, and quadrature phase signals (LOQP, LOQN) of the second frequency are input. Herein, the first frequency represents carrier frequency, and the second frequency represents LO (Local Oscillator) frequency. Therefore, the signal of the first frequency is the input signal received, and the signal of the second frequency is the LO signal. 
     In addition, the harmonic mixer  110  outputs signals (IFIP, IFIN) of a third frequency generated by subtracting a twice value of the second frequency from the first frequency of the input signal. That is, “third frequency=first frequency−(2×second frequency)”. Herein the third frequency is intermediate frequency. 
     In the first mixer  120 , signals (IFIP, IFIN) of the third frequency and In-phase signals (LOIP, LOIN) of the second frequency are input. In addition, the first mixer  120  outputs In-phase signals (BFIP, BFIN) of the fourth frequency generated by subtracting the second frequency from the third frequency. 
     In the second mixer  130 , signals (IFIP, IFIN) of the third signal and In-phase signals (LOQP, LOQN) of the second frequency are input. In addition, the second mixer  130  outputs In-phase signals (BFQP, BFQN) of the fourth frequency generated by subtracting the second frequency from the third frequency. 
     Herein, “fourth frequency=third frequency−second frequency”. In addition, the fourth frequency is baseband frequency, and the signals of the fourth frequency are baseband signals. 
     For example, in a case where the first frequency (carrier frequency) is 60 GHz and the second frequency (LO frequency) is 20 GHz, the frequency of the signals output from the harmonic mixer  110  is 20 GHz, and the frequency of the signals output from the first mixer  120  and second mixer  130  is baseband frequency. 
       FIG. 2  is a diagram illustrating a down-frequency conversion circuit  200 , according to an exemplary embodiment of the present disclosure. The down-frequency conversion circuit  200  of  FIG. 2  is a structure where a buffer amplifier  210  has been added to the down-frequency conversion circuit  100  of  FIG. 1 . 
     The buffer amplifier  210  amplifiers signals output from the harmonic mixer  110 . Therefore, the down-frequency conversion circuit  200  becomes able to amplify an intensity of a conversion signal through the buffer amplifier  210 . 
       FIG. 3  is a detailed circuit diagram of the down-converter  100  of  FIG. 1 , according to an exemplary embodiment of the present disclosure. As illustrated in  FIG. 3 , the harmonic mixer  110  is embodied to include a total of 8 transistors, and the first mixer  120  and third mixer  130  are embodied to include 4 transistors each. 
     A down-converter of such a structure becomes able to convert the frequency of RF signals input into baseband frequency using only one LO frequency. Therefore, it becomes possible to have only one LO and VCO (Voltage Controlled Oscillator) for generating frequency. 
     Furthermore, the down-frequency conversion circuit illustrated in  FIGS. 1 to 3  may be applied to a receiver to convert a received signal into a baseband signal. Then, since there is one LO, VCO included in the down-frequency converter, it becomes possible to form a receiver at a lower cost. 
     Hereinbelow is explanation on the up-frequency conversion circuit, with reference to  FIGS. 4 and 5 .  FIG. 4  illustrates a structure of a up-frequency conversion circuit  400  according to an exemplary embodiment of the present disclosure. As illustrated in  FIG. 4 , the up-frequency conversion circuit  400  includes a third mixer  410 , fourth mixer  420 , and harmonic mixer  430 . 
     Herein, the third mixer  410  and fourth mixer  420  are general mixers. A general mixer outputs a signal of a frequency generated by adding or subtracting one LO (Local Oscillator) frequency to/from one input signal frequency. On the other hand, in the harmonic mixer, an input signal and two LO frequency signals having reverse phases in a same frequency are input, and the harmonic mixer outputs a signal of a frequency by adding or subtracting a twice value of the LO frequency to/from the input signal frequency. 
     In the third mixer  410 , In-phase signals (BFIP, BFIN) of the fifth frequency and In-phase signals (LOIP, LOIN) of the sixth frequency are input. In addition, the third mixer  410  outputs signals (IFIP, IFIN) of a seventh frequency generated by adding the sixth frequency to the fifth frequency. 
     In the fourth mixer  420 , quadrature signals (BFQP. BFQN) of the fifth frequency and In-phase signals (LOQP, LOQN) of the sixth frequency are input. In addition, The fourth mixer  420  outputs signals (IFIP, IFIN) of a seventh frequency generated by adding the sixth frequency to the fifth frequency. 
     Herein, “seventh frequency=fifth frequency+sixth frequency”. In addition, the fifth frequency is baseband frequency, and signals of the fifth frequency are baseband signals. Furthermore, the sixth frequency represents frequency of LO (Local Oscillator), and signals of the sixth frequency become LO signals. In addition, the seventh frequency is intermediate frequency. 
     In the harmonic mixer  430 , signals (IFIP, IFIN) of the seventh frequency, In-phase signals (LOIP, LOIN) of the sixth frequency, and quadrature phase signals (LOQP, LOQN) of the sixth frequency are input. In addition, the harmonic mixer  430  outputs signals (RFIP, RFIN) of the eighth frequency generated by adding a twice value of the sixth frequency to the seventh frequency. That is, “eighth frequency=seventh frequency=(2×sixth frequency)”. Herein, the eighth frequency is carrier frequency. 
     For example, in a case where the sixth frequency (LO frequency) is 20 GHz, a frequency of the signals output from the third mixer  410  and fourth mixer  420  is intermediate frequency, 20 GHz, and a frequency of the signals output from the harmonic mixer  430  is carrier frequency, 60 GHz. 
       FIG. 5  is a detailed circuit diagram of the up-converter  400  of  FIG. 4 . As illustrated in  FIG. 5 , the harmonic mixer  430  is embodied to include a total of 8 transistors, and the third mixer  410  and fourth mixer  420  are embodied to include 4 transistors each. 
     The up-converter of such a structure becomes able to convert input signals of baseband frequency into RF signals of carrier frequency using only one LO frequency. Therefore, it becomes possible to have only one LO and VCO (Voltage Controlled Oscillator) for frequency generation. 
     Furthermore, the up-frequency conversion circuit illustrated in  FIGS. 4 and 5  may be applied to a transceiver to convert signals to be transmitted from baseband into signals of carrier frequency. Then, since there is one LO, VCO included in the up-converter, it becomes possible to form the transceiver at a lower cost. 
     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 this embodiment without departing from the principles and spirit of the invention, the scope of which is defined in the claims and their equivalents.