JP5137961B2 - Frequency converter and quadrature modulator - Google Patents

Description

The present invention relates to a frequency conversion device and a quadrature modulator. This application is related to the following Japanese application and claims priority from the following Japanese application. For designated countries where incorporation by reference of documents is permitted, the contents described in the following application are incorporated into this application by reference and made a part of this application.
Japanese Patent Application No. 2007-274281 Application date October 22, 2007

  2. Description of the Related Art Conventionally, a device using a multiplier (mixer) is known as a device that outputs a baseband signal by shifting the frequency according to a local signal (see, for example, Patent Document 1 or 2). The apparatus generates a signal having a frequency obtained by adding / subtracting the frequency of the baseband signal and the frequency of the local signal.

Such a multiplier has two input ports and one output port. By applying a baseband signal to one input port of the multiplier and supplying a local signal to the other input port, a signal obtained by multiplying the baseband signal and the local signal can be obtained.
JP 2001-333120 A JP 2002-237856 A

  Each port of the multiplier is connected to an internal multiplication circuit. For this reason, a leak component of each signal may appear at each port via a multiplication circuit or the like. For example, a leak component of a local signal may appear at the baseband input port and be output to the outside.

  When such a leak component is returned to the inside of the multiplier by external reflection or the like, a signal having the same frequency is multiplied to generate a DC component. For example, when a local signal and its leak component are multiplied, the frequency subtraction result is substantially zero, and a DC component is generated. For this reason, the multiplier may not operate accurately.

  In addition to the above-described DC component, the output port of the device includes a first signal having a frequency obtained by adding the frequencies of the baseband signal and the local signal, and a second signal having a frequency obtained by subtracting the frequencies of the baseband signal and the local signal. The signal, the leak component of the local signal returned to the inside of the multiplier, and the leak component of the baseband signal appear. Then, by providing a filter in the subsequent stage of the output port, either the first signal or the second signal is selectively passed, and other signals and leak components are removed.

  As an example, the frequency of the baseband signal is 1 MHz, and the frequency of the local signal is 4 GHz. In this case, the first signal (4.001 GHz), the second signal (3.999 GHz), the local signal leak component (4 GHz), and the baseband signal leak component (1 MHz) appear at the output port. Of these, the first signal 4.001 GHz is selectively passed. However, since the leak component (4 GHz) of the local signal to be removed exists in the band near the first signal (4.001 GHz) to be passed, the design of the filter becomes very difficult.

  In order to solve the above problem, it is also conceivable to use a double heterodyne configuration or the like to convert a baseband signal into an intermediate frequency signal and then modulate it with a local signal. Thereby, the design of the filter can be facilitated, but there may be a case where the configuration is not preferable in terms of cost and the like.

  Accordingly, an object of one aspect of the present invention is to provide a frequency converter and a quadrature modulator that can solve the above-described problems. This object is achieved by a combination of features described in the independent claims. The dependent claims define further advantageous specific examples of the present invention.

  According to a first aspect of the present invention, there is provided a frequency conversion device that outputs a baseband signal after frequency shifting in accordance with a local signal, a mixer that multiplies the baseband signal and the local signal, and outputs the first signal. The baseband signal is received at the port, the received baseband signal is output from the second port and supplied to the mixer, and the leak component leaking from the mixer to the second port is not passed through the first port. And a duplexer that outputs from a third port different from the above.

  In the second aspect, the quadrature modulator outputs the baseband signal by performing quadrature modulation according to the local signal, receives the baseband signal, and modulates the baseband signal according to the given local signal. An I-side modulator and a Q-side modulator, and a 90-degree phase shift unit for shifting the phase of a local signal supplied to the I-side modulator and the Q-side modulator by 90 degrees. Each of the units multiplies the baseband signal and the local signal and outputs them, and receives the baseband signal at the first port, outputs the received baseband signal from the second port, and supplies it to the mixer. A quadrature modulator having a duplexer that outputs a leak component leaking to the second port from a third port different from the first port without passing the leak component through the first port Subjected to.

  The above summary of the invention does not enumerate all the necessary features of the present invention, and sub-combinations of these feature groups can also be the invention.

It is a figure which shows the structural example of the frequency converter 100 based on 1st Embodiment. 3 is a diagram illustrating a configuration example of a duplexer 20. FIG. 2 is a diagram illustrating a configuration example of a mixer 30. FIG. 3 is a diagram illustrating a configuration example of a 180-degree phase shift unit 40. FIG. It is a figure which shows the structural example of the orthogonal modulator 200 which concerns on 2nd Embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Local signal supply part, 12 ... Baseband signal supply part, 20 ... Demultiplexer, 21 ... 1st port, 22 ... 2nd port, 23 ... 3rd port , 24 ... low pass filter, 25 ... high pass filter, 30 ... mixer, 34 ... baseband signal input section, 35 ... synthesis section, 40 ... 180-degree phase shift section, 41 · ..Unbalanced line, 42... 1st balanced line, 43... 2nd balanced line, 51... 1 unbalanced line, 52. 54, second unbalanced line, 55, second balanced line, 60, multiplication unit, 61, 62, 63, 64, diode, 65, 66, capacitor, 100,.・ Frequency converter, 200 ... quadrature modulator, 201 ... 90 degree phase shift , 202 ... I side modulator 203 ... Q side modulator 204 ... adding unit

  Hereinafter, the (1) aspect of the present invention will be described through embodiments of the invention. However, the following embodiments do not limit the invention according to the scope of claims, and the features described in the embodiments are as follows. Not all combinations are essential for the solution of the invention.

  FIG. 1 is a diagram illustrating a configuration example of a frequency conversion device 100 according to the first embodiment. The frequency conversion device 100 is a device that outputs a baseband signal by shifting the frequency according to a local signal, and includes a local signal supply unit 10, a baseband signal supply unit 12, a duplexer 20, and a mixer 30. Prepare.

  The local signal supply unit 10 outputs a local signal Lo having a predetermined frequency. The local signal supply unit 10 may generate the local signal Lo using a PLL circuit or the like. In this case, the local signal supply unit 10 may be able to set the frequency of the local signal Lo within a predetermined frequency range. The local signal supply unit 10 may output the local signal Lo received from the outside.

  The baseband signal supply unit 12 outputs a baseband signal BB having a predetermined frequency whose frequency should be shifted by the local signal Lo. The baseband signal supply unit 12 may generate the baseband signal BB and may receive it from the outside. The baseband signal supply unit 12 may output a baseband signal BB in which the frequency of the included signal component is within a predetermined range.

  The mixer 30 receives the baseband signal BB and the local signal Lo from different ports, respectively, and outputs an output signal RF obtained by multiplying the baseband signal BB and the local signal Lo. The mixer 30 may multiply the baseband signal BB and the local signal Lo by a diode bridge or a transistor.

  The duplexer 20 receives the baseband signal BB from the baseband signal supply unit 12 and supplies the received baseband signal BB to the mixer 30. Further, the duplexer 20 receives the leak component Leak leaked from the mixer 30 and absorbs the leak component Leak to the ground potential through a path different from the path connected to the baseband signal supply unit 12.

  With such a configuration, the leak component Leak can be prevented from returning to the inside of the mixer 30. Therefore, the mixer 30 can be operated with high accuracy, and an accurate output signal RF can be obtained. Even if the frequency of the baseband signal is small and the frequency difference between the output signal RF and the local signal Lo is small, the duplexer 20 absorbs the leak component of the local signal Lo, so that the RF of the mixer 30 is absorbed. The local signal Lo can be prevented from appearing at the output. For this reason, the filter provided in the subsequent stage of the mixer 30 can be designed easily. In this example, the frequency conversion device 100 has been described using the baseband signal BB. However, an intermediate frequency signal IF may be used instead of the baseband signal BB.

  FIG. 2 is a diagram illustrating a configuration example of the duplexer 20. The duplexer 20 includes a first port 21, a second port 22, a third port 23, a low pass filter 24, and a high pass filter 25. The first port 21 is connected to the baseband signal supply unit 12 and receives the baseband signal BB. The second port 22 is connected to the mixer 30 and outputs a baseband signal. The third port 23 is connected to the ground potential.

  The low pass filter 24 is provided between the first port 21 and the second port 22. The pass band in the low-pass filter 24 is set to a band that allows the frequency component of the baseband signal BB to pass and does not allow the frequency component of the local signal Lo to pass. Thus, the baseband signal BB received from the baseband signal supply unit 12 can be supplied from the second port 22 to the mixer 30. Further, it is possible to prevent the leak component Leak of the local signal from the mixer 30 from being output from the first port 21 and reflected at the output end of the baseband signal supply unit 12 or the like.

  The high pass filter 25 is provided between the third port 23 and the second port 22. The pass band in the high pass filter 25 is set to a band that allows the frequency component of the local signal Lo to pass and does not pass the frequency component of the baseband signal BB. As a result, the leak component Leak can be output from the third port 23 and absorbed by the ground potential.

  The low pass filter 24 and the high pass filter 25 may be connected to the second port 22 via a common transmission path. With the configuration described above, it is possible to prevent the leak component Leak from returning to the mixer 30 while supplying the baseband signal BB to the mixer 30.

  In this example, the case where the frequency of the baseband signal BB is lower than the frequency of the local signal Lo has been described. However, when the frequency of the baseband signal BB is higher than the frequency of the local signal Lo, the duplexer 20 is used. The high-pass filter 25 and the low-pass filter 24 may be replaced with each other. Further, the passbands of the low pass filter 24 and the high pass filter 25 may be fixed. In general, since the frequency difference between the baseband signal BB and the local signal Lo is sufficiently large, the baseband signal BB and the local signal Lo can be accurately obtained in a fixed pass band even when the frequency of the local signal Lo or the like is changed. Can be separated. The duplexer 20 may be able to change the pass bands of the low-pass filter 24 and the high-pass filter 25 according to the frequency bands of the baseband signal BB and the local signal Lo.

  FIG. 3 is a diagram illustrating a configuration example of the mixer 30. The mixer 30 includes a 180-degree phase shift unit 40, a multiplication unit 60, a baseband signal input unit 34, and a synthesis unit 35. The 180-degree phase shift unit 40 receives the local signal Lo from the local signal supply unit 10 and generates a local signal Lo and an inverted local signal RLo. The inverted local signal RLo may be a signal that is 180 degrees out of phase with the local signal Lo. The 180-degree phase shifter 40 may output the local signal Lo and the inverted local signal RLo using, for example, a balun.

  The 180-degree phase shift unit 40 includes a first unbalanced line 51, a microstrip line 53, a second unbalanced line 54, a first balanced line 52, and a second balanced line 55. The first unbalanced line 51 receives the local signal Lo at one end and is connected to the microstrip line 53 at the other end. One end of the second unbalanced line 54 is connected to the first unbalanced line 51 via the microstrip line 53, and the other end is opened.

  The first balanced line 52 forms a coupling line with the first unbalanced line 51. The second balanced line 55 forms a coupling line with the second unbalanced line 54. The electrical lengths of the first unbalanced line 51 and the second unbalanced line 54 are determined according to ¼ of the wavelength of the local signal. With such a configuration, the local signal Lo is output from the first balanced line 52, and the inverted local signal RLo is output from the second balanced line 55.

  Multiplier 60 multiplies local signal Lo and inverted local signal RLo with baseband signal BB and outputs the result. In this case, the phases of the two signals output from the multiplication unit 60 are inverted. The multiplication unit 60 includes a cascade-connected diode 61 and a diode 63, and a cascade-connected diode 62 and a diode 64 in parallel. The multiplier 60 receives the local signal Lo between the diode 61 and the diode 63 and receives the inverted local signal RLo between the diode 62 and the diode 64. Multiplier 60 receives baseband signals BB between diode 61 and diode 62 and between diode 63 and diode 64, respectively.

  The baseband signal input unit 34 receives the baseband signal BB from the duplexer 20 and supplies the baseband signal BB between the diode 61 and the diode 62 and between the diode 63 and the diode 64 in the multiplication unit 60. To do. The multiplier 60 supplies a signal obtained by multiplying the local signal Lo and the baseband signal BB to the synthesizer 35 via the capacitor 65. Further, the multiplication unit 60 supplies a signal obtained by multiplying the inverted local signal RLo and the baseband signal BB to the synthesis unit 35 via the capacitor 66.

  The synthesizer 35 synthesizes and outputs the signals received from the multiplier 60. For example, the synthesizer 35 may add and output the signal given via the capacitor 65 and the inverted signal of the signal given via the capacitor 66. Thereby, the output signal RF can be obtained.

  The synthesizing unit 35 of this example may have the same configuration as the 180-degree phase shift unit 40. However, in the synthesizer 35, the first balanced line 52 receives the signal output from the multiplier 60 via the capacitor 65, and the second balanced line 55 receives the signal output from the multiplier 60 via the capacitor 66. receive. The first unbalanced line 51 is connected to an output port to the outside.

  Further, as described with reference to FIGS. 1 and 2, the local signal Lo or the like may leak and be output to the outside via the baseband signal input unit 34. When such a component is input to the baseband signal input unit 34 due to reflection or the like, the component of the local signal that leaks from the combining unit 35 to the outside increases. On the other hand, as described with reference to FIGS. 1 and 2, by providing the duplexer 20, the leakage component can be prevented from returning to the mixer 30. The configuration described with reference to FIG. 3 shows an example of the configuration of the mixer 30, and the mixer 30 can adopt another known configuration. Moreover, although FIG. 3 demonstrated using the structure of the double balanced mixer, the mixer 30 may be a single balanced mixer.

  FIG. 4 is a diagram illustrating a configuration example of the 180-degree phase shift unit 40. The 180-degree phase shift unit 40 includes an unbalanced line 41, first balanced lines (42-1, 42-2), and second balanced lines (43-1, 43-2). The unbalanced line 41 may be a line that receives the local signal Lo at one end (starting end) and is open at the other end (termination).

  The first balanced lines (42-1, 42-2) are provided on both sides of the unbalanced line 41 over a predetermined length from the start end of the unbalanced line 41, and are coupled to the unbalanced line 41. That is, the unbalanced line 41 is provided between the first balanced line 42-1 and the first balanced line 42-2. With such a configuration, the connectivity of the first balanced line 42 and the unbalanced line 41 can be improved.

  The first balanced line 42-1 and the first balanced line 42-2 are connected to each other to form a line on the loop. Also, one end of the first balanced line 42-1 and the first balanced line 42-2 is connected to the ground potential, and the local signal Lo is output from the other end. The first balanced line 42-1 and the first balanced line 42-2 may have an electrical length corresponding to ¼ of the wavelength of the local signal Lo.

  The second balanced lines (43-1, 43-2) are provided on both sides of the unbalanced line 41 over a predetermined length from the end of the unbalanced line 41. The length of the second balanced line 43 may be the same as the length of the first balanced line 42. The second balanced line 43-1 and the second balanced line 43-2 are connected to each other to form a line on the loop. One end of the second balanced line 43-1 and the second balanced line 43-2 is connected to the ground potential, and the inverted local signal RLo is output from the other end. With such a configuration, the connectivity of the second balanced line 43 and the unbalanced line 41 can be enhanced.

  FIG. 5 is a diagram illustrating a configuration example of the quadrature modulator 200 according to the second embodiment. The quadrature modulator 200 is a device that performs quadrature modulation on the baseband signal BB according to the local signal Lo and outputs the baseband signal BB, and includes a 90-degree phase shifter 201, an I-side modulator 202, a Q-side modulator 203, and An adding unit 204 is provided.

  The 90-degree phase shifter 201 receives the local signal Lo and supplies it to the I-side modulator 202 and the Q-side modulator 203. At this time, the 90-degree phase shifter 201 shifts the phase of the local signal Lo given to, for example, one of the I-side modulator 202 and the Q-side modulator 203 by 90 degrees, so that the I-side modulator 202 and the Q-side modulator 203 are shifted. The phase of the local signal Lo supplied to is different by 90 degrees. The 90-degree phase shifter 201 may generate these local signals Lo using, for example, a Lange coupler.

  The I-side modulator 202 and the Q-side modulator 203 receive the baseband signal BB and modulate the baseband signal BB according to the given local signal Lo. Each of the I-side modulator 202 and the Q-side modulator 203 may have the same configuration as the frequency conversion device 100 described with reference to FIGS. 1 to 4.

  Adder 204 adds the output signals output from I-side modulator 202 and Q-side modulator 203. According to the quadrature modulator 200 of this example, the I-side modulator 202 and the Q-side modulator 203 can each modulate a signal with high accuracy.

  As mentioned above, although this invention was demonstrated using embodiment, the technical scope of this invention is not limited to the range as described in the said embodiment. It will be apparent to those skilled in the art that various modifications or improvements can be added to the above-described embodiment. It is apparent from the scope of the claims that the embodiments added with such changes or improvements can be included in the technical scope of the present invention.

  The order of execution of each process such as operations, procedures, steps, and stages in the apparatus, system, program, and method shown in the claims, the description, and the drawings is particularly “before” or “prior to”. It should be noted that the output can be realized in any order unless the output of the previous process is used in the subsequent process. Regarding the operation flow in the claims, the description, and the drawings, even if it is described using “first”, “next”, etc. for convenience, it means that it is essential to carry out in this order. It is not a thing.

Claims (5)

A frequency conversion device that outputs a baseband signal by shifting the frequency according to a local signal,
A mixer for multiplying and outputting the baseband signal and the local signal;
The baseband signal is received at the first port, the received baseband signal is output from the second port and supplied to the mixer, and a leak component leaking from the mixer to the second port is supplied to the first port. A duplexer that outputs from a third port different from the first port without passing through ;
A baseband signal supply unit for supplying the baseband signal to the first port of the duplexer;
With
The duplexer outputs the leak component from the third port and absorbs it to a ground potential,
A low-pass filter that is provided between the first port and the second port, passes a frequency component of the baseband signal, and does not pass a frequency component of the local signal;
A high-pass filter provided between the third port and the second port, which passes the frequency component of the local signal and does not pass the frequency component of the baseband signal;
A frequency conversion device having: The frequency converter according to claim 1 , wherein the mixer is a double balanced mixer or a single balanced mixer. The mixer is
A 180 degree phase shift unit that receives the local signal and generates an inverted local signal that is 180 degrees different in phase from the local signal and the local signal;
A multiplier for multiplying the local signal and the inverted local signal by the baseband signal;
The frequency converter according to claim 2 , further comprising: a combining unit that inverts and combines one of the signals output from the multiplication unit. The 180 degree phase shift part is
An unbalanced line that receives the local signal at one end and is open at the other end;
A first balanced line provided on both sides of the unbalanced line over a predetermined length from the one end of the unbalanced line, and supplying the local signal to the multiplier;
The over from said other end a predetermined length of the unbalanced line, the provided on both sides of the unbalanced line, wherein the inverted local signal to claim 3 and a second balanced line supplied to the multiplying unit Frequency converter. A quadrature modulator that quadrature modulates and outputs a baseband signal according to a local signal,
An I-side modulator and a Q-side modulator that receive the baseband signal and modulate the baseband signal according to the given local signal;
A 90-degree phase shift unit for shifting the phase of the local signal supplied to the I-side modulator and the Q-side modulator by 90 degrees,
Each of the I-side modulator and the Q-side modulator is
A mixer for multiplying and outputting the baseband signal and the local signal;
The baseband signal is received at the first port, the received baseband signal is output from the second port and supplied to the mixer, and a leak component leaking from the mixer to the second port is supplied to the first port. A duplexer that outputs from a third port different from the first port without passing through ;
A baseband signal supply unit for supplying the baseband signal to the first port of the duplexer;
With
The duplexer outputs the leak component from the third port and absorbs it to a ground potential,
A low-pass filter that is provided between the first port and the second port, passes a frequency component of the baseband signal, and does not pass a frequency component of the local signal;
A quadrature modulator having a high-pass filter that is provided between the third port and the second port and passes the frequency component of the local signal and does not pass the frequency component of the baseband signal .

Images