JP2001203537A - Mixer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a mixer that extracts an intermediate frequency signal from two input signals while suppressing production of an undesired frequency component. SOLUTION: A coupler H1 outputs a 1st synthesis voltage resulting from shifting a phase of one input signal voltage by 90 degrees and synthesizing the resulting voltage with the other input signal voltage and outputs a 2nd synthesis voltage resulting from shifting a phase of the other input signal voltage by 90 degrees and synthesizing the resulting voltage with the one input signal voltage. A coupler H2 outputs the received 1st synthesis voltage and a 3rd synthesis voltage resulting from shifting the phase of the 1st synthesis voltage by 90 degrees. A coupler H3 outputs the received 2nd synthesis voltage and a 4th synthesis voltage resulting from shifting the phase of the 2nd synthesis voltage by 90 degrees. Non-reflecting terminators T1, T2 are connected to one-input terminals of the couplers H2, H3. Current conversion means D1-D4 convert the respective synthesis voltages into 1st-4th synthesis current including the components in proportion to a square value of each voltage by a prescribed coefficient, and a current extract means 1 extracts an intermediate frequency current on the basis of the sum of the synthesis current.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mixer for inputting two signals and extracting an intermediate frequency signal composed of a component of a difference between these frequencies, and particularly has a problem in practical use when generating an intermediate frequency signal. The present invention relates to a mixer that suppresses generation of an unnecessary frequency component signal to a small extent, thereby reducing conversion loss.

[0002]

2. Description of the Related Art Mixers are used to input two signals and extract an intermediate frequency signal composed of a component of a difference between these frequencies. For example, in a receiver employing a superheterodyne method, a received high-frequency signal is used. Signal (RF
Wave signal) and a local oscillation wave signal (LO
Wave signal) is mixed by a mixer to extract an intermediate frequency signal (IF wave signal).

FIG. 5 shows a configuration example of a single mixer using one diode. In this single mixer, the LO wave signal passing through the filter 11 and the filter 1
2 and the RF wave signal passed through the diode D5.
And the IF signal output from the diode D5 is extracted through the filter 13. In this configuration, for example, a directional coupler is provided outside the single mixer, and the LO wave signal input to the diode D5 and the R
The F-wave signal is on the same line.

[0004] The signal processing procedure in the above-described single mixer will be described in more detail using mathematical expressions. For example, Equation 1
If the signal voltage V _RF signal voltages V _LO and RF wave signal of the LO wave signal shown in it is input to a single mixer, the signal voltage V5 which is inputted to the diode D5 is as shown in equation 2.

[0005]

(Equation 1)

[0006]

(Equation 2)

Here, it is assumed that, when a signal voltage V is input to the diode D5, the signal current I flowing through the diode D5 becomes as shown in Expression 3.

[0008]

(Equation 3)

In Equation 3, a, b, c,... Are predetermined coefficients, which are generally determined according to the characteristics of the diode D5. In the following description, for simplicity, terms up to the square of V in Equation 3 will be taken.
The term of the third power of V or more, which has relatively little influence on, is ignored in the calculation. By substituting the signal voltage V5 input to the diode D5 for V in the above equation 3, and calculating the signal current I5 flowing through the diode D5, the equation 4 is obtained.

[0010]

(Equation 4)

The first item of the component of the signal current I5 is a DC component (a component of a constant), and the second item is a component of an input wave (a component having a frequency of ω _LO or ω _RF ). , Third
The item is the second harmonic component (the component whose frequency is 2ω _LO or 2ω _RF ), and the fourth item is the sum component of the LO wave signal and the RF wave signal (the component whose frequency is ω _LO + ω _RF ). Yes, fifth
The item is a difference component (a component whose frequency is ω _RF −ω _LO ) between the LO wave signal and the RF wave signal. The fifth item among these components is an intermediate frequency component detected as an IF wave signal, and this IF wave signal component is generated due to the square of V (cV ² ) in Equation 3. It should be noted that from the term of the zeroth power of V (a) and the term of the first power of V (bV) in Equation 3,
No wave signal is generated.

The components of the first to fourth items are unnecessary frequency components generated as noise when the IF wave signal is generated. In order to eliminate such unnecessary frequency components, a low-pass filter for blocking a signal having a frequency higher than the frequency of the IF wave signal is provided as a filter 13 at the output end of the single mixer shown in FIG. That is, the signal current I5 output from the diode D5 by passing through the low-pass filter 13 has a structure in which an intermediate frequency current I _IF of IF wave signal is extracted from the output end. In such a configuration, although an unnecessary frequency component signal can be eliminated by the filter 13, the output of the IF wave signal obtained from the output terminal becomes extremely weak.

In general, since an LO wave signal is transmitted from a transmission source provided inside a receiver or the like, an input signal can be obtained with a sufficiently large power. Because it is received by radio, etc.
In many cases, an input signal can be obtained with very weak power. Therefore, in order to combine the LO wave signal and the RF wave signal to obtain an output of a sufficiently large IF wave signal, it is necessary to convert the RF wave signal into an IF wave signal with high efficiency. ,
The configuration of the single mixer described above is insufficient for practical use and the like.

FIG. 6 shows a configuration example of a balanced mixer using two diodes. In this balanced mixer, the LO wave signal and the RF wave signal input to the hybrid coupler H4 are combined, and the two combined wave signals output from the coupler H4 are respectively converted into diodes D
6. Input to diode D7. Then, the signal currents generated in the respective diodes D6 and D7 are summed in accordance with these synthesized wave signals, and the summed current passes through the low-pass filter 14 to extract an IF wave signal. In such a balanced mixer, generation of signals of unnecessary frequency components other than the intermediate frequency can be further suppressed as compared with the single mixer described above, and the efficiency of conversion from an RF wave signal to an IF wave signal can be further increased. It is known that can be.

The procedure of signal processing in such a balanced mixer will be described in more detail using mathematical expressions. In addition,
Signal voltage V of LO wave signal input to balanced mixer
_{It is} assumed that the _LO and the signal voltage V _RF of the RF wave signal are the same as those shown in Expression 1. As the hybrid coupler H4, a 90-degree hybrid 3 dB directional coupler (90 ° hysteresis) is used.
brid 3dB coupler), and this coupler H4
Then, when the LO wave signal and the RF wave signal are input, the LO
The phase of the wave signal is shifted by 90 degrees and the combined signal is added to the RF wave signal, and the phase of the RF signal is shifted by 90 degrees in the same direction and L
The O-wave signal and the added composite signal are output. 3 dB
Represents the amplitude ratio of the output signal to the input signal,
In the case of 3 dB, it becomes (1/2) ^1/2 .

The signal voltage V6 output from the hybrid coupler H4 and input to the diode D6 and the signal voltage V7 output from the hybrid coupler H4 and input to the diode D7 are expressed by Equation 5.

[0017]

(Equation 5)

In this balanced mixer, the signal voltage V6
Is input, the direction of the signal current I6 flowing through the diode D6 is opposite to the direction of the signal current I7 flowing through the diode D7 when the signal voltage V7 is input. total current I _BS signal current I6, I7 outputted from both diodes D6, D7 are as shown in equation 6. Note that the diode D6
Also, it is assumed that the characteristics of the diode D7 are expressed as in the above-described Expression 3 similarly to the diode D5 shown in FIG.

[0019]

(Equation 6)

In this manner, L is adjusted by the balanced mixer.
When the IF wave signal is extracted from the O wave signal and the RF wave signal, no DC component is generated at all as compared with the case of the above-described single mixer, and the same as the IF wave signal in the case of the single mixer. Neither does the component of the sum of the two signal frequencies generated with a large amplitude occur. As described above, in the balanced mixer, generation of unnecessary frequency signals other than the intermediate frequency can be suppressed as compared with the single mixer, and the amplitude of the IF wave signal is the same as that of the single mixer. (I.e., "cAB"), the balanced mixer can generally increase the efficiency of conversion from the RF signal to the IF signal compared to the single mixer.

[0021]

However, in the above-described balanced mixer, the generation of unnecessary frequency component signals is suppressed in the relative comparison with the single mixer, and the RF wave signal is efficiently converted into IF signals. Although it can be converted into a wave signal, there is a considerable loss in practical use and it is still insufficient. That is, in the above-described balanced mixer, the IF wave signal is generated by generating a composite wave signal of the LO wave signal and the RF wave signal and obtaining a signal current component proportional to the square of the signal voltage of the composite wave signal. Although an unnecessary frequency component such as a second harmonic is generated at the same time as the generation of the IF wave signal, there is a problem that conversion with sufficient efficiency in practical use is not performed. .

From the above, it is possible to reduce the conversion loss by eliminating the generation of unnecessary frequency components other than the intermediate frequency to the extent that there is no problem in practical use. There has been a demand for a mixer that can improve the efficiency of the conversion into a liquid. Further, for example, in the above-described balanced mixer, since the loss at the time of conversion is large, it is often necessary to amplify the obtained IF wave signal with an amplifier or the like, and it is possible to avoid performing such amplification processing. For this purpose, it has been required to improve the efficiency of conversion by the mixer.

The present invention has been made in order to solve such a conventional problem. When two signals are input and an intermediate frequency signal composed of a component of a difference between these frequencies is taken out, the present invention is practically used. An object of the present invention is to provide a mixer that can suppress generation of an unnecessary frequency component signal to the extent that there is no problem. More specifically, when an intermediate frequency signal is generated, unnecessary signal current such as a frequency component of a second harmonic generated by a square of a signal voltage in a diode or the like is suppressed, thereby making it possible to input an intermediate frequency signal. The conversion loss from the converted signal to the intermediate frequency signal is reduced, thereby improving the efficiency of the conversion.

[0024]

In order to achieve the above object, in a mixer according to the present invention, two signals are input and an intermediate frequency signal composed of a component of a difference between these signals is extracted as follows. . First, in the first hybrid coupler, two signals cos (ω _LO t) and cos (ω _RF t) such as an LO wave signal and an RF wave signal are input, and one of these input signals has a signal voltage. 90
The phase of the first composite voltage Vm1 added to the other input signal voltage and the phase of the other input signal voltage are shifted by 90 degrees in the same direction.
The second combined voltage Vm2 added to the one input signal voltage and the one input signal voltage is output with a stagger. For example, the first combined voltage Vm1 and the second combined voltage Vm2 are represented by Expression 7.

[0025]

(Equation 7)

Next, in the second hybrid coupler, the first composite voltage V
m1 is input, and the first combined voltage Vm1 and a third combined voltage Vm3 obtained by shifting the phase of the first combined voltage by 90 degrees are output. In the third hybrid coupler, the second composite voltage V is output from the first hybrid coupler.
m2 is input, and the second combined voltage Vm2 and a fourth combined voltage Vm4 obtained by shifting the phase of the second combined voltage by 90 degrees are output. For example, the third combined voltage Vm3 and the fourth combined voltage Vm4 are represented by Expression 8.

[0027]

(Equation 8)

Next, the first combined voltage Vm1 output from the second hybrid coupler is converted into a predetermined coefficient c by the square of the voltage Vm1 by the first current converting means composed of, for example, a diode. Is converted into a first combined current Im1 including a component proportional to. Further, the third combined voltage Vm3 output from the second hybrid coupler is proportional to the square of the voltage Vm3 by the predetermined coefficient c by the second current converting means composed of, for example, a diode. Is converted into a second combined current Im2 including the component.

Further, the second combined voltage Vm2 output from the third hybrid coupler is converted into the square of the voltage Vm2 by a predetermined coefficient by third current converting means constituted by, for example, a diode. It is converted to a third combined current Im3 including a component proportional to c. Further, the fourth combined voltage Vm4 output from the third hybrid coupler is converted to the square of the voltage Vm4 by the predetermined coefficient c
Is converted to a fourth combined current Im4 including a component proportional to.

Next, an intermediate frequency current is extracted by the current extracting means based on the sum of the first combined current Im1 to the fourth combined current Im4. For example summing current I _FS of first combined current Im1 to fourth combined current Im4 as shown in Equation 9.

[0031]

(Equation 9)

In Equation 9, for example, the first combined current Im1
Or when taking out only a component proportional to the square of the signal voltage for the fourth combined current Im 4, contributing current component I _FS (V component proportional to the square of signal voltage to the sum current I _FS
² ) is as shown in Expression 10, and only the intermediate frequency current is generated without generating the signal of the second harmonic.

[0033]

(Equation 10)

Therefore, the two input signals are combined by the first to third hybrid couplers, and an intermediate frequency current is generated by, for example, a term proportional to the square of the combined wave signal thus obtained. As described above, since generation of unnecessary frequency component signals such as second harmonics can be suppressed as described above, generation of unnecessary frequency component signals to the extent that there is no problem in practical use is eliminated, and The conversion loss to the intermediate frequency signal can be reduced, and the efficiency of the conversion can be improved.

[0035]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment according to the present invention will be described with reference to the drawings. FIG. 1 shows an example of a mixer according to the present invention. The mixer includes three hybrid couplers H1 to H3, four diodes D1 to D4, and a filter 1. This mixer connects one of the two output terminals provided in the first hybrid coupler H1 to the input terminal of the second hybrid coupler H2, and connects the other to the input terminal of the third hybrid coupler H3. The second hybrid coupler H2 and the third
Are connected to diodes D1 to D4, respectively, at the output terminals of the hybrid coupler.

In the present embodiment, for example, a receiver employing a superheterodyne system is provided with the mixer of the present invention, and the mixer uses the mixer to generate a local oscillation wave signal (LO wave signal) oscillated from a local oscillator provided inside the receiver. ) And the received high-frequency signal (RF wave signal) are mixed to extract an intermediate frequency signal (IF wave signal). Below,
The procedure of the signal processing performed by the mixer, together with the configuration of the mixer shown in FIG. 1, will be described in detail using mathematical expressions. It is assumed that a signal voltage similar to the above equation 1 is input to the mixer, that is, a signal voltage V _{LO of the LO} wave signal and a signal voltage V _RF of the RF wave signal as shown in the equation 11 are input. And

[0037]

[Equation 11]

As the hybrid couplers H1 to H3, in this embodiment, 90-degree hybrid 3 dB directional couplers are used. As described above, the hybrid coupler H1 forms the first hybrid coupler in the present embodiment, receives the LO wave signal and the RF wave signal, and outputs the phase of one of the input signals V _LO . Is shifted by 90 degrees to add the other input signal voltage _VRF to the first composite voltage Vp
And the phase of the other input signal voltage _{VRF in} the same direction by 90
It has a function of outputting the one input signal voltage V _LO and the added second combined voltage Vq with a stagger. here,
The signal voltage V _LO is the signal voltage of the input LO wave signal, and the signal voltage V _RF is the signal voltage of the input RF wave signal.

In this embodiment, the hybrid coupler H1
Since a 90-degree hybrid 3 dB directional coupler is used, the signal voltage input to the coupler H1 is actually multiplied by a coefficient of (1/2) ^1/2 and output. Therefore, the first combined voltage Vp and the second combined voltage Vq actually output from the hybrid coupler H1
Is shown as Equation 12.

[0040]

(Equation 12)

In this example, the hybrid coupler H1
In the above, a method of shifting the phase of the signal voltage by 90 degrees was used to shift the phase of the signal voltage by 90 degrees. However, conversely, the phase of the signal voltage was shifted by 90 degrees in the direction of advancing the phase. You can also

As described above, the hybrid coupler H2 forms a second hybrid coupler in the present embodiment, and receives the first composite voltage Vp output from the hybrid coupler H1 and inputs the first composite voltage Vp. It has a function of outputting a third combined voltage V3 obtained by shifting the phase of Vp and the first combined voltage Vp by 90 degrees. In this example, the first combined voltage Vp is input from one input terminal of the hybrid coupler H2 as described above, and the non-reflection terminal T1 is connected to the other input terminal. That is, no signal is input from the input terminal to which the non-reflection terminal T1 is connected.

In this embodiment, the hybrid coupler H2
Since a 90 ° hybrid 3 dB directional coupler is used, the composite voltage Vp input to the coupler H2 is actually multiplied by a coefficient of (１ ／) ^1/2 and output. For this reason, the first combined voltage V1 and the third combined voltage V3 actually output from the hybrid coupler H2 are expressed by Expression 13.

[0044]

(Equation 13)

In this example, the hybrid coupler H2
In the above, a method of shifting the phase of the signal voltage by 90 degrees was used to shift the phase of the signal voltage by 90 degrees. However, conversely, the phase of the signal voltage was shifted by 90 degrees in the direction of advancing the phase. You can also

As described above, the hybrid coupler H3 forms a third hybrid coupler in the present embodiment, and receives the second composite voltage Vq output from the hybrid coupler H1 to input the second composite voltage Vq. It has a function of outputting a fourth combined voltage V4 obtained by shifting the phase of Vq and the second combined voltage Vq by 90 degrees. Note that, in the present example, as in the case of the above-described hybrid coupler H2, the hybrid coupler H
As described above, the second combined voltage Vq is input from one of the input terminals of No. 4 and the non-reflection terminal T2 is connected to the other input terminal.

In this embodiment, the hybrid coupler H3
Since a 90 dB hybrid 3 dB directional coupler is used as the above, the composite voltage Vq input to the coupler H3 is actually multiplied by a coefficient of (1/2) ^1/2 and output. For this reason, the second combined voltage V2 and the fourth combined voltage V4 actually output from the hybrid coupler H3 are expressed as in Expression 14.

[0048]

[Equation 14]

In this example, the hybrid coupler H3
In the above, a method of shifting the phase of the signal voltage by 90 degrees was used to shift the phase of the signal voltage by 90 degrees. However, conversely, the phase of the signal voltage was shifted by 90 degrees in the direction of advancing the phase. You can also

The diode D1 receives the first composite voltage V1 output from the second hybrid coupler H2, and includes a component proportional to the square of the voltage V1 by a predetermined coefficient c. In this example, the diode D1 constitutes a first current conversion means. Diode D
2 receives the third combined voltage V3 output from the second hybrid coupler H2 and converts the voltage V3 to the voltage V3.
It has a function of converting to a first combined current I2 including a component proportional to the square of 3 by the predetermined coefficient c. In this example, the diode D2 constitutes a second current conversion means. ing.

The diode D3 receives the second composite voltage V2 output from the third hybrid coupler H3 and converts the voltage V2 into a component proportional to the square of the voltage V2 by the predetermined coefficient c. The diode D3 has a function of converting it into the included third combined current I3.
Constitutes a third current converting means. The diode D4 receives the fourth synthesized voltage V4 output from the third hybrid coupler H3, and includes a component that includes a component proportional to the square of the voltage V4 by the predetermined coefficient c. 4 has a function of converting to a combined current I4 of
In this example, the diode D4 constitutes a fourth current converter.

In this example, it is assumed that the diodes D1 to D4 have characteristics similar to the characteristics expressed by the above-mentioned equation (3).
That is, when the signal voltage V is input to the diodes D1 to D4, the signal current I flowing through the diodes D1 to D4 is expressed as shown in Expression 15.

[0053]

(Equation 15)

Here, in the present example, for example, a term of the third or higher power of the signal voltage V, which has relatively little influence on the signal current I, is neglected in the calculation.
The explanation will be made up to the square of.

The first to fourth signal currents I1 to I4 converted by the diodes D1 to D4 as described above are summed up and input to the filter 1. here,
As shown in FIG. 1, the mixer of this embodiment has a configuration in which the directions of the signal currents flowing through the diodes D1 and D2 and the directions of the signal currents flowing through the diodes D3 and D4 are opposite to each other. Therefore, the first to fourth signal currents I1 input to the filter 1
The total current Is of .about.I4 is shown as in equation (16).

[0056]

(Equation 16)

[0057] In the thus obtained sum current Is, the signal component of the second harmonic wave (i.e., the frequency 2 [omega _LO and 2
a omega _RF component) without at all occurs, in this example as shown in Equation 16, the component (the frequency of the signal component (the frequency of the input wave is a _RF omega _LO and omega component) and the intermediate frequency signal omega _RF −ω
Only the component that is _LO ) occurs.

The filter 1 is, for example, a low-pass filter (L
PF). In this example, this filter 1
Has a function of passing an intermediate frequency signal having a frequency of (ω _RF −ω _LO ), while blocking a signal component having a frequency of ω _LO or ω _RF . That is, when the total current Is obtained as described above passes through the filter 1, the intermediate frequency signal I _IF is output from the output terminal of the mixer.
Only are retrieved and output.

In this embodiment, the filter 1 allows the total sum Is of the above-described first to fourth combined currents I1 to I4.
The current extracting means for extracting the intermediate frequency current based on the above is constituted. The current extracting means may have any configuration as long as it can extract the generated intermediate frequency signal. For example, without providing a filter, the intermediate output signal may be generated together with the other generated frequency component signals. A configuration for extracting a frequency signal may be used.

As described above, in the mixer according to the present invention,
Compared with the single mixer shown in FIG. 5 and the balanced mixer shown in FIG. 6 shown in the above conventional example, it is possible to suppress the generation of the signal of the most unnecessary frequency component such as the frequency component of the second harmonic. In addition, while suppressing unnecessary frequency components in this way, the amplitude (cAB) of the intermediate frequency signal is the same as in the case of the single mixer or the balanced mixer.
Conversion loss from the input signal to the intermediate frequency signal can be reduced, thereby improving the efficiency of the conversion. As described above, according to the present invention, it is possible to eliminate the generation of unnecessary frequency component signals to the extent that there is no problem in practical use, thereby improving the conversion efficiency.

Next, an experimental example in which the conversion loss in the mixer shown in FIG. 1 is measured will be described. In the mixer used in the experiment of this example, an NRD guide is used as a line for transmitting a signal, and a poly-tetra-fluoro-ethylene (non-dielectric constant: 2.04) is used as a dielectric material for the NRD. (Trade name: Teflon) is used. A signal of 60 GHz is used as the center frequency.
FIG. 2 shows a configuration example of a mixer having an appearance in which the upper metal plate is removed from the NRD guide structure used in this experiment. The mixer shown in the figure has three 90-degree hybrid 3 dB directional couplers H1 to H3 similarly to the configuration shown in FIG.
And four diodes D1 to D4, and their functions are as described above.

In this embodiment, the diodes D1 to D4 are constituted by diode mounts, and FIG. 3 is a three-dimensional view of the diode mount. As shown in the figure, in this example, Schottky barrier diodes are used as the diodes D1 to D4, and a low-pass filter (LPF) 1 is provided in this mount.
Both ends of the diode mount are connected to a back surface circuit by a semi-rigid cable, and an intermediate frequency signal is output from the back surface circuit.

In this example, a Gunn oscillator is used for the oscillation of the LO wave signal, a synthesized sweeper is used for the oscillation of the RF wave signal, and a spectrum analyzer is used for the measurement of the IF wave signal. I have. In the configuration of the mixer shown in FIG. 1, the hybrid couplers H2, H2
Although the non-reflection terminals T1 and T2 were connected to one input terminal of No. 3, in the experiment of this example, instead of connecting the non-reflection terminals, the hybrid couplers H2 and H3 were changed so that the conversion efficiency became the best. The length of the line connected to the one input / output terminal is adjusted.

The conversion loss from the RF signal to the IF signal was measured by the mixer having the above configuration. The procedure of mixing the LO wave signal and the RF wave signal input by the mixer to extract the IF wave signal is as described with reference to FIG.

FIG. 4 is a graph showing the conversion loss measured by using the mixer shown in FIG. 2 and the conversion loss measured by using the conventional balanced mixer according to the conventional example. . In this graph, the horizontal axis represents the frequency (MHz) of the intermediate frequency signal, and the vertical axis represents the conversion loss (d
B). When comparing the mixer of the present invention with the conventional balanced mixer, the conversion loss of the normal balanced mixer shown by the broken line is about 8 dB, while the conversion loss of the mixer of the present invention shown by the solid line is 1.0 to 1.0 dB. Improvement of the conversion loss of about 1.5 dB, that is, reduction of the conversion loss was realized.

In the mixer according to the experiment of this example, the effect of using the configuration in which the non-reflection termination is not connected to one of the input terminals of the hybrid couplers H2 and H3 as described above is compared with the characteristics of the balanced mixer. Although the bandwidth became narrower, the results of the above experiments demonstrated that the mixer of the present invention can improve the conversion loss as compared with the conventional balanced mixer.

As described above, in the present invention, when a process of inputting two signals and extracting an intermediate frequency signal therebetween is performed, generation of unnecessary frequency component signals is suppressed to a level that does not hinder practical use. Thus, the conversion loss can be reduced, and the efficiency of the conversion can be improved. For example, in the above experiment, it was confirmed that the conversion loss can be improved by 1.0 to 1.5 dB as compared with the conventional balanced mixer. As described above, the mixer of the present invention can obtain high conversion efficiency, and is particularly effective when, for example, it is difficult to use an amplifier when constructing a circuit. By ensuring the conversion efficiency, a large output intermediate frequency signal can be obtained without using an amplifier.

When the mixer of the present invention is formed by using three identical 90 ° hybrid 3 dB directional couplers and four identical diodes as in the above embodiment, the 90 ° hybrid 3 dB directional coupler is used. Since the same components may be assembled as the coupler and the diode, the configuration of the mixer is not complicated, and the productivity and the like can be improved.

Here, in the above embodiment, a 90 ° hybrid 3 dB directional coupler is used as the hybrid coupler, and the combined voltage from the second and third hybrid couplers is proportional to the square of the voltage. Although the case where a diode is used as a current converting means for converting into a combined current including the components having the above-mentioned components has been described, any configuration may be used as long as circuit components or the like having similar functions are used. In other words, any configuration may be used as long as the generation of the intermediate frequency signal can suppress the generation of the signal of the unnecessary frequency component to the extent that there is no problem in practical use.

In the above embodiment, the case where the mixer according to the present invention is applied to a receiver employing the superheterodyne system and an intermediate frequency signal is extracted from a received high frequency signal and a local oscillation signal has been described. However, the present invention
Any signal can be applied as long as it performs a process of inputting two signals and extracting an intermediate frequency signal composed of components of these frequency differences. By applying the present invention, there is no practical problem. The generation of signals of unnecessary frequency components other than the intermediate frequency is suppressed to the extent that the conversion efficiency of the input signal to the intermediate frequency signal can be improved.

[0071]

As described above, according to the mixer of the present invention, when two signals are input and an intermediate frequency signal composed of a component of a difference between these frequencies is extracted,
As described above, four combined voltages are generated from the two input signal voltages by the three hybrid couplers, and these four combined voltages are converted into four combined currents by current conversion means such as diodes, respectively, and are converted. Since the intermediate frequency current is extracted based on the sum of the four combined currents, the generation of signals of unnecessary frequency components other than the intermediate frequency can be suppressed to a level that does not hinder practical use. To the intermediate frequency signal, and the efficiency of the conversion can be improved.

[Brief description of the drawings]

FIG. 1 is a configuration example of a mixer according to an embodiment of the present invention.

FIG. 2 is a configuration example of a mixer used in an experiment for measuring conversion loss.

FIG. 3 is a configuration example of a diode mount unit.

FIG. 4 is a graph of conversion loss obtained by an experiment.

FIG. 5 is a configuration example of a single mixer according to a conventional example.

FIG. 6 is a configuration example of a balanced mixer according to a conventional example.

[Explanation of symbols]

H1, H2, H3 ··· Hybrid coupler, D1, D
2, D3, D4, diode, T1, T2, non-reflective termination, 1, filter

Claims (1)

[Claims] 1. A mixer for inputting two signals and extracting an intermediate frequency signal composed of a component of a difference between these frequencies, wherein two signals are input and a phase of one signal voltage of one of these input signals is inputted. And a second composite voltage obtained by adding the one input signal voltage by shifting the phase of the other input signal voltage by 90 degrees in the same direction by adding 90 degrees to the other input signal voltage. And a first hybrid combiner that outputs the following. The first combined voltage is input from the first hybrid combiner, and the phases of the first combined voltage and the first combined voltage are shifted by 90 degrees. A second hybrid combiner that outputs a third combined voltage, and a second combined voltage that is input from the first hybrid combiner, and the phase of the second combined voltage and the phase of the second combined voltage Shifted 90 degrees A third hybrid combiner that outputs a fourth combined voltage; and a first hybrid combiner that outputs the fourth combined voltage.
A first current converting means for converting the composite voltage of the first voltage into a first composite current including a component proportional to the square of the voltage by a predetermined coefficient; and 3
A second current converting means for converting the composite voltage of the above to a second composite current including a component proportional to the square of the voltage by the predetermined coefficient; and Second
A third current converting means for converting the combined voltage of the above to a third combined current including a component proportional to the square of the voltage by the predetermined coefficient; and 4th
A fourth current conversion means for converting the combined voltage of the first to fourth combined currents into a fourth combined current including a component proportional to the square of the voltage by the predetermined coefficient; and the first combined current to the fourth combined current. A current extracting means for extracting an intermediate frequency current based on the sum of the currents.