JP5161887B2 - 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. 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. 2007-271727 Filing Date October 18, 2007

  Conventionally, a configuration that uses a merchandise balun in a mixer that generates an output signal in which an input signal is frequency-shifted according to a local signal can be considered. For example, a configuration in which a phase of an input signal or a local signal is shifted by 180 degrees by a merchandise balun and distributed to two multipliers is conceivable. At this time, the frequency of the input signal or the like input to the mixer is not always constant. For this reason, the mixer preferably has a wide operating band.

The following patent documents are recognized as prior art documents related to the mixer.
JP 2001-333120 A JP 2002-237856 A

  However, when trying to realize a broadband mixer using a merchandise balun, the flatness of the frequency characteristics of conversion loss deteriorates. For example, if the even mode impedance is increased and the odd mode impedance is decreased in order to widen the band of the merchandise balun, the difference between the conversion loss of the merchandise balun at the low frequency and the high frequency becomes large. For this reason, the flatness of the conversion loss is deteriorated.

  Accordingly, an object 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.

In order to solve the above-described problem, in the first aspect of the present invention, a frequency conversion device that generates an output signal obtained by shifting the frequency of an input signal according to a local signal, the differential signal based on the local signal. A first merchant balun that generates a local signal of the second, a second merchant balun that generates a differential input signal based on the input signal, and an output based on the differential local signal and the differential input signal Between the non-inverting side transmission line and the inverting side transmission line, and the non-inverting side transmission line and the inverting side transmission line that transmit the differential input signal from the differential input signal generator to the mixer. A provided characteristic correcting inductor, a first resistor between the non-inverting transmission line and the characteristic correcting inductor, and a second resistor between the inverting transmission line and the characteristic correcting inductor. For example, characteristic correction inductor, to lower the impedance of the frequency converter in the low frequency band, to increase the impedance of the frequency converter in the high frequency band having a frequency higher than the low frequency, the first resistor and the second Provided is a frequency converter in which the resistance value of the resistor is larger than the resistance value of the resistor in the non-inversion side transmission line and the inversion side transmission line.

According to a second aspect of the present invention, there is provided a quadrature modulator that performs quadrature modulation of an input signal according to a local signal and outputs the input signal, and receives the input signal and modulates the input signal according to a given local signal. A side modulator and a Q side modulator, and a 90-degree phase shift unit that causes the phase of a local signal supplied to the I side modulator and the Q side modulator to be 90 degrees different from each other. Each of the first merchant balun generates a differential local signal based on the local signal, the second merchant balun generates a differential input signal based on the input signal, and the differential local signal And a mixer that generates an output signal based on a differential input signal, a non-inverting transmission line and an inverting transmission line that transmit a differential input signal from the differential input signal generation unit to the mixer, and a non-inverting A characteristic correcting inductor provided between the transmission line and the inverting transmission line; a first resistor between the non-inverting transmission line and the characteristic correcting inductor; and the inverting transmission line and the characteristic correcting inductor. A second resistor in between, and the characteristic correcting inductor lowers the impedance of the modulator in the low frequency band and increases the impedance of the modulator in the high frequency band having a frequency higher than the low frequency. The resistance value of 1 resistance and 2nd resistance provides the orthogonal modulator larger than the resistance value of the resistance in a non-inversion side transmission line and an inversion side transmission line.

  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 which concerns on 1st Embodiment. It is a figure which shows an example of the measurement result of the conversion loss characteristic in the frequency converter. It is a figure which shows the circuit used for simulation. It is a figure which shows the calculated insertion loss characteristic and return loss characteristic. It is a figure which shows the calculated insertion loss characteristic. These are figures which show the calculated return loss characteristic. 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 ... Differential local signal generation part, 12 ... Differential input signal generation part, 14 ... Mixer, 16 ... Non-inversion side transmission line, 18 ... Inversion side transmission line, 20 ...・ Characteristic correction inductor, 22, 24... Resistor, 26, 28... Inductor, 30, 32, 34... Capacitor, 36, 38... Resistance, 50.・ Frequency converter, 200... Quadrature modulator, 201... 90 degree phase shifter, 202... I-side modulator, 203.

  Hereinafter, the present invention will be described through embodiments of the invention. However, the following embodiments do not limit the claimed invention, and all combinations of features described in the embodiments are invented. It is not always essential to the solution.

  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 generates an output signal IF obtained by shifting the frequency of the input signal RF in accordance with the local signal Lo, and includes a differential local signal generator 10, a differential input signal generator 12, a mixer 14, The inversion side transmission line 16, the inversion side transmission line 18, the characteristic correction inductor 20, the synthesis unit 50, a plurality of resistors 22, 24, 36, and 38, and a plurality of capacitors 32 and 34 are provided.

  The differential local signal generator 10 receives the local signal Lo, and generates a differential local signal (Lo, RLo) based on the local signal Lo. The frequency conversion apparatus 100 may supply the local signal Lo received from the outside to the differential local signal generation unit 10 and may supply the local signal Lo generated internally to the differential local signal generation unit 10. As an example, the frequency of the local signal Lo may be about 3.06 to 12.06 GHz. Further, the power of the local signal Lo may be about 20 dBm.

  The differential local signal generation unit 10 receives a local signal at one end and a balun having a balanced line having the other end opened and two unbalanced lines each having an electrical length of ¼ of the wavelength of the local signal. May be used to generate differential local signals (Lo, RLo). The differential local signal generation unit 10 of this example generates a differential local signal using a merchandise balun.

  The differential input signal generator 12 receives the input signal RF and generates a differential input signal (RF, RRF) based on the input signal RF. The frequency conversion apparatus 100 may supply the input signal RF received from the outside to the differential input signal generation unit 12 or may supply the input signal RF generated internally to the differential input signal generation unit 12. The differential input signal generation unit 12 may generate a differential input signal using a balun as in the differential local signal generation unit 10. As an example, the frequency of the input signal RF may be about 3.00 to 12.00 GHZ. In this example, the frequency of the local signal Lo is set to a frequency that is 60 MHz higher than the input signal RF. Further, the power of the input signal RF may be about −10 dBm.

  The mixer 14 receives a differential local signal (Lo, RLo) and a differential input signal (RF, RRF), an output signal IF obtained by multiplying the local signal Lo and the input signal RF, an inverted local signal RLo, and an inverted signal. Output signal IF multiplied by the input signal RRF. The mixer 14 may multiply these signals by a double balanced mixer such as a diode bridge or a transistor.

  The mixer 14 has two local terminals that receive differential local signals (Lo, RLo) and two input terminals that receive differential input signals (RF, RRF). The two local terminals are connected to the two balanced lines of the differential local signal generation unit 10. The two input terminals are connected to the two balanced lines of the differential input signal generation unit 12 via the non-inverting transmission line 16 and the inverting transmission line 18.

  The synthesizer 50 synthesizes the in-phase output signal IF output from the mixer 14 and outputs it to the outside. The synthesis unit 50 of this example is provided between the input side terminal of the mixer 14 and the differential input signal generation unit 12 and adds the in-phase output signal IF output from the input side terminal of the mixer 14.

  The combining unit 50 includes an inductor 26, an inductor 28, and a capacitor 30. The inductor 26 is provided on a line connecting the terminal that outputs the output signal IF to the outside and the non-inverted transmission line 16. The inductor 28 is provided on a line connecting the terminal and the inverting transmission line 18. The capacitor 30 is provided between the terminal and the ground potential. The constants of the inductor 26, the inductor 28, and the capacitor 30 may be determined according to the frequency of the output signal IF to be sent to the outside.

  In this example, the frequency of the output signal IF is 60 MHz (the frequency obtained by subtracting the frequency of the input signal RF from the frequency of the local signal IF). The constants of the inductor 26, the inductor 28, and the capacitor 30 may be set so that the synthesizing unit 50 functions as a low-pass filter that passes a signal of the frequency.

  The characteristic correcting inductor 20 is provided between the non-inverting transmission line 16 and the inverting transmission line 18. The characteristic correcting inductor 20 corrects the flatness of the conversion loss characteristic in the frequency converter 100. For example, the characteristic correcting inductor 20 may compensate for the deterioration of the flatness of the frequency characteristic when the differential input signal generation unit 12 is widened. The widening of the differential input signal generation unit 12 and the correction of the flatness of the frequency characteristics will be described later with reference to FIGS. 2 to 5B. By providing the characteristic correcting inductor 20, it is possible to realize the frequency conversion device 100 having a flat conversion loss characteristic over a wide band.

  Capacitors (32, 34) are provided on the transmission paths of the non-inversion transmission line 16 and the inversion transmission line 18, respectively. The capacitors (32, 34) receive the differential input signals (RF, RFF) from the differential input signal generation unit 12 via the resistors (36, 38). The capacitors (32, 34) remove the DC component of the differential input signals (RF, RFF) and supply them to the mixer 14.

  The characteristic correcting inductor 20 may be disposed between the capacitors (32, 34) and the mixer 14 so as to connect the non-inverting transmission line 16 and the inverting transmission line 18. The characteristic correcting inductor 20 of the present example connects the non-inverted transmission line 16 and the inverted transmission line 18 between the capacitors (32, 34) and the combining unit 50. With such a configuration, it is possible to prevent a direct current component from being transmitted between the non-inverting transmission line 16 and the inverting transmission line 18 via the characteristic correcting inductor 20.

  In addition, a first resistor 22 is provided so as to connect one end of the characteristic correction inductor 20 and the non-inversion transmission line 16. A second resistor 24 is provided so as to connect the other end of the characteristic correcting inductor 20 and the inverting transmission line 18.

  The resistance values of the first resistor 22 and the second resistor 24 may be larger than the resistance values of the resistors (36, 38) in the non-inverting transmission line 16 and the inverting transmission line 18. For example, the resistance values of the first resistor 22 and the second resistor 24 may be about 150Ω. On the other hand, the resistance value of the resistors (36, 38) may be about 10Ω. The capacitance of the capacitors (32, 34) may be about 5.4 pF. Further, the inductance of the characteristic correcting inductor 20 may be about 5 nH. Further, the inductance of the inductors (26, 28) may be approximately the same as that of the characteristic correcting inductor 20. Further, in this example, the example in which the frequency conversion device 100 functions as a down converter has been described, but in another example, the frequency conversion device 100 may function as an up converter.

  Even when the local signal (Lo, RLo) or the input signal (RF, RRF) leaks and is input to the synthesizer 50, the leak component is a differential signal. It cancels out by adding each other. For this reason, the frequency converter 100 can remove the leak components such as the local signal Lo and the input signal RF, and can output the output signal IF with high accuracy.

  FIG. 2 is a diagram illustrating an example of the measurement result of the conversion loss characteristic in the frequency conversion device 100. The measurement results of this example were measured under the frequency, power, and constant conditions described in FIG. In FIG. 2, the horizontal axis represents the frequency of the input signal RF, and the vertical axis represents the conversion loss at each frequency. The conversion loss can be obtained from the ratio of the power of the input signal RF and the power of the output signal IF, for example. Further, the conversion loss characteristic of the frequency converter 100 shown in FIG. 1 is indicated by a solid line, and the conversion loss characteristic when the characteristic correction inductor 20 is not provided is indicated by a dotted line. As shown in FIG. 2, when the characteristic correcting inductor 20 is not provided, the conversion loss characteristic has a steep slope.

  On the other hand, by providing the characteristic correcting inductor 20, it is possible to reduce the impedance in the low frequency band and increase the impedance in the high frequency band. For this reason, as shown in FIG. 2, the loss in the low frequency band can be suppressed, and the flatness of the conversion loss characteristic can be corrected. The inductance of the characteristic correction inductor 20 may be determined by the slope of the slope of the conversion loss characteristic when the characteristic correction inductor 20 is not provided.

  The conversion loss characteristic having a steep slope as shown by the dotted line in FIG. 2 becomes more prominent when the merchant balun of the differential input signal generation unit 12 is widened. Below, the deterioration of the flatness of the conversion loss characteristic accompanying the broadband of a merchant balun is demonstrated using a simulation result.

  FIG. 3 is a diagram illustrating a circuit used for the simulation. As shown in FIG. 3, in the simulation, a circuit in which two merchant baluns are connected point-to-back in a back-to-back manner was used. In this circuit, the balanced line on the non-inverting side of the first balun is connected to the balanced line on the inverting side of the second balun, and the balanced line on the inverting side of the first balun is connected to the non-inverting side of the second balun. Connect to the reverse balanced line.

  In the simulation, the insertion loss and return loss in the circuit were calculated. The insertion loss indicates the ratio of the power of the signal output from port 2 to the power of the signal input to port 1 in FIG. Return loss indicates the ratio of the power of the signal output from port 1 to the power of the signal input to port 1 in FIG.

  FIG. 4 is a diagram showing the calculated insertion loss characteristic and return loss characteristic. The return loss characteristic is indicated by a solid line, and the insertion loss characteristic is indicated by a dotted line. The horizontal axis in FIG. 4 indicates the frequency of the signal, and the vertical axis indicates the loss.

  As shown in FIGS. 2 and 4, the conversion loss characteristic of the frequency converter 100 and the insertion loss characteristic of the merchant balun have a correlation. Further, the slope in the vicinity of 3 to 5 GHz in the conversion loss characteristic is steeper because the return loss characteristic shown in FIG. 4 is caused by abrupt deterioration in the vicinity of 3 to 5 GHz. it can.

  Further, as described above, the deterioration of the conversion loss characteristic becomes more conspicuous as the merchant balun becomes wider. Next, the insertion loss characteristic and the return loss characteristic were calculated by simulation while changing the band of the merchant balun. In the following, simulation was performed using an ideal merchant balun. Here, the ideal merchant balun may be a merchant balun using a lossless line, for example.

  Further, the even mode impedance Ze and odd mode impedance Zo in the merchant balun were changed to change the band of the merchant balun. Generally, when the even mode impedance Ze is increased and the odd mode impedance Zo is decreased, the merchant balun band is widened. In the following simulation, loss characteristics at Ze = 300Ω and Zo = 15Ω and loss characteristics at Ze = 200Ω and Zo = 25Ω were calculated.

  FIG. 5A is a diagram showing the calculated insertion loss characteristic. FIG. 5B is a diagram showing the calculated return loss characteristics. 5A and 5B, the horizontal axis indicates the frequency of the signal, and the vertical axis indicates the loss.

  As shown in FIGS. 5A and 5B, it can be confirmed that the band when Ze = 300Ω and Zo = 15Ω is wider than the band when Ze = 200Ω and Zo = 25Ω. However, by widening the band, the flatness of the loss characteristics deteriorates on the low frequency side (for example, in the vicinity of 3 to 7 GHz) and on the wide area side (for example, in the vicinity of 9 to 13 GHz). In addition to the deterioration of the loss characteristics, considering that the loss on the line increases as the frequency becomes higher, it can be confirmed that if the merchant balun has a wider band, a steeper slope is generated on the lower side of the loss characteristics. .

  On the other hand, the frequency converter 100 described in relation to FIG. 1 is provided with the characteristic correcting inductor 20 to lower the low-frequency impedance and increase the high-frequency impedance. As a result, it is possible to compensate for the deterioration of the flatness of the conversion loss characteristic accompanying the increase in the bandwidth of the merchant balun.

  FIG. 6 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 input signal RF in accordance with the local signal Lo and outputs it, and includes a 90-degree phase shifter 201, an I-side modulator 202, a Q-side modulator 203, and an addition The 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 input signal RF and modulate the input signal RF 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 FIG.

  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, as the I-side modulator 202 and the Q-side modulator 203, it is possible to use a modulator having a wide band and good conversion loss characteristics.

  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 execution order 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”. It should be noted that they can be implemented 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 the sake of convenience, it means that it is essential to carry out in this order. is not.

Claims (3)

A frequency converter that generates an output signal obtained by shifting an input signal in accordance with a local signal,
A first merchant balun that generates the differential local signal based on the local signal;
A second merchant balun that generates the differential input signal based on the input signal;
A mixer that generates the output signal based on the differential local signal and the differential input signal;
A non-inverting transmission line and an inverting transmission line for transmitting the differential input signal from the second merchant balun to the mixer;
A characteristic correcting inductor provided between the non-inverting transmission line and the inverting transmission line;
A first resistor between the non-inverting transmission line and the characteristic correcting inductor;
A second resistor between the inverting transmission line and the characteristic correcting inductor;
The characteristic correcting inductor lowers the impedance of the frequency converter in the low frequency band, and increases the impedance of the frequency converter in the high frequency band having a frequency higher than the low frequency,
The frequency conversion device in which resistance values of the first resistor and the second resistor are larger than resistance values of resistors in the non-inversion side transmission line and the inversion side transmission line. Capacitors are provided on the transmission lines of the non-inverting transmission line and the inverting transmission line,
The frequency converter according to claim 1, wherein the characteristic correction inductor connects the non-inversion side transmission line and the inversion side transmission line between the capacitor and the mixer. A quadrature modulator that quadrature modulates and outputs an input signal according to a local signal,
An I-side modulator and a Q-side modulator that receive the input signal and modulate the input 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 first merchant balun that generates the differential local signal based on the local signal;
A second merchant balun that generates the differential input signal based on the input signal;
A mixer that generates an output signal based on the differential local signal and the differential input signal;
A non-inverting transmission line and an inverting transmission line for transmitting the differential input signal from the second merchant balun to the mixer;
A characteristic correcting inductor provided between the non-inverting transmission line and the inverting transmission line;
A first resistor between the non-inverting transmission line and the characteristic correcting inductor;
A second resistor between the inverting transmission line and the characteristic correcting inductor;
The characteristic correcting inductor lowers the impedance of the modulator in a low frequency band, and increases the impedance of the modulator in a high frequency band having a frequency higher than the low frequency,
The quadrature modulator wherein resistance values of the first resistor and the second resistor are larger than resistance values of the resistors in the non-inversion side transmission line and the inversion side transmission line.

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